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  • Studies Show Slurry Roadside Disposal is Safe

    Download the printable PDF Academic and government research consistently demonstrates that disposing of CGR on roadsides poses no danger to soil or vegetation—and can even act as a soil stabilizer. Concrete grinding residue (CGR) is an inert, nonhazardous byproduct of the diamond grinding process, which is used on pavement to restore ride quality, increase skid resistance and reduce noise. When diamond grinding concrete highways, water used to cool cutting blades combines with hardened cement paste and aggregate particulates to generate CGR, also known as slurry. Many states do not have the benefit of clear, localized guidance on disposal methods for CGR. This leads to a situation in which CGR disposal is potentially posing unnecessary costs for projects—and leaves the beneficial effects of slurry underutilized. Often, states limit how much slurry can be discharged along the roadside during the diamond grinding process. But hauling slurry off-site for processing and disposal is costly for DOTs and for taxpayers. The elimination of unnecessary regulations in areas with site conditions that allow for the discharge of CGR directly to the road’s shoulder would benefit roadway owners and taxpayers by reducing construction costs. To determine the real impact of slurry on roadside soil and vegetation, multiple studies have been performed. They have all found slurry to be safe. What is Slurry? Slurry is a combination of water used to cool the grinding blades and solids resulting from the removal of a thin layer of the concrete, including silica, cadmium, and other chemical constituents of cement and supplementary cementitious materials. (It should be noted that while respirable silica on the jobsite can pose a health hazard to workers, silica in CGR is mixed with a substantial amount of water and does not become free or airborne after deposition on the site, so it is not harmful to workers.) The contents of slurry reflect the contents of concrete—mostly mineral—as well as possible compounds present in the cooling water. Over the years, multiple laboratory tests have been conducted to identify the components of CGR. Per the criteria for identifying hazardous waste under U.S. Code of Federal Regulations, Title 40, Part 261, the elements and compounds present in tested slurry are non-ignitable, non-corrosive and non-toxic; therefore, CGR can be considered a non-hazardous waste. Elevated soil pH has been the sole concern raised by slurry testing—and tests have shown the pH characteristics of disposed slurry did not exceed California’s stringent Title 22 standards. The California Department of Transportation (Caltrans) found that slurry samples for organic and inorganic constituents displayed no hazardous characteristics when compared to California Title 22 hazardous waste standards. Caltrans 96-hour Acute Toxicity testing showed no toxicity characteristics and that the slurry samples represent no toxic threat to public health and the environment. A Minnesota Department of Transportation (MnDOT) study found fresh CGR materials collected for research purposes were comprised predominantly of silica (53.12%) and lime (16.82%), which also are the major compounds found in concrete materials. The lime (along with some trace minerals) found in CGR can be beneficial to plant life. In fact, many DOTs regulate the deposition of slurry in terms of its lime equivalency, often called calcium carbonate equivalency (CCE). Lime equivalency, expressed as a percentage, is the acid-neutralizing capacity of a carbonate rock relative to that of pure calcium carbonate (e.g., calcite). Analyzing Slurry Compounds In May 1990, seven samples of diamond grinding slurry were presented to an independent testing laboratory in Charlotte, North Carolina, for chemical analysis. The objectives of the analysis were to determine composition of the slurry, quantify each component, and compare volume to maximum permissible limits for each component as established by the U.S. Environmental Protection Agency (EPA) and the North Carolina Department of Environment, Health & Natural Resources (now part of the North Carolina Department of Environmental Quality [DEQ]). The slurry samples were taken from three different work sites. One site had 20-year-old portland cement concrete (PCC) pavement; one site had two-year-old PCC pavement; and one site had one-year-old PCC pavement. Two samples were obtained from three locations on a highway grinding project in Delaware; three samples were taken from different locations on an interstate highway grinding project in Pennsylvania; and two samples were taken from different locations on a bridge deck grinding project in South Carolina. These jobsites were selected because they were considered representative of most grinding work and because work was underway at the time samples were needed; the actual sample locations were selected at random and samples were obtained on different days. After analysis, the report concluded: Under the criteria for identifying hazardous waste under 40 CFR 261, the above waste is nonignitable, non-corrosive and non-toxic; therefore, it is generally considered a nonhazardous waste. Studies Find Slurry is Safe Researchers have been working to identify CGR’s precise ecological effects, as well as how CGR disposal can be optimized. Tests consistently have shown that proper slurry deposition along roadsides is safe and can act like a fertilizer when used as a lime equivalent. Let’s review three studies by government and academic researchers—all of which found similar results. Minnesota Department of Transportation And Iowa State University’s Institute For Transportation Beginning in 2016, Iowa State University (ISU) conducted the study, “Concrete Grinding Residue: Its Effect on Roadside Vegetation and Soil Properties,” on behalf of MnDOT, evaluating slurry deposit impact on vegetation and soils. Tests included depositing slurry that had been collected from a slurry tank at a Minnesota construction site onto a controlled field site in Iowa. CGR was applied to test sections of vegetation at rates of 10 tons/acre (2.24 kg/m2), 20 tons/ acre (4.48 kg/m2) and 40 tons/acre (8.96 kg/m2); additionally, a control section was maintained. Properties of soils and plants were assessed before the application and one month, six months and one year after the CGR application Key Takeaways The study found that the application of CGR did not significantly affect soil physical properties. Effects of CGR on soil chemical properties were influenced by application rate, soil depth, time after CGR application and CGR source. Overall, application of CGR up to 40 dry tons/acre (the maximum amount studied) showed no significant adverse effect on soil or plant biomass. Iowa State University’s Institute for Transportation and Iowa Highway Research Board (IHRB) Another study, “Use of Concrete Grinding Residue as a Soil Amendment,” sponsored by the Iowa Highway Research Board (IHRB), further examined the environmental impacts of CGR. It also conducted a laboratory assessment of CGR as a soil amendment, since CGR’s high pH and rich calcium oxide content make it potentially suitable for recycling as a soil stabilizer. Clayed sand (soil type A-6 according to the American Association of State Highway and Transportation Officials [AASHTO] Soil Classification System) and sandy, silty soil with clay (AASHTO soil type A-4) were studied, focusing on CGR’s effect on soil plasticity and soil pH. Results of the study demonstrated that as CGR content was increased, the A-6 soil’s plasticity index (the difference between the liquid and plastic limit) decreased, going from an Atterberg limit measurement of 16 for the control group (with no CGR application) to a measurement of eight for the soil that received a CGR application rate of 40%. For soil type A-4, Atterberg limit measurements decreased from seven (for the control group) to five (at the 40% application rate). The study also found that with the addition of CGR, the maximum dry density (unit weight) of the soil went down, while the optimal moisture content went up. Unconfined compressive strength and California bearing ratio (CBR) of each soil were found to be optimized at a 20% CGR content. The application of CGR increased soil pH, alkalinity, electrical conductivity and cation-exchange capacity. Improvements in soil strength caused by the application of CGR are attributable to the formation of calcium silicate hydrate gel. The gel formation is a combined effect of flocculation, cement hydration and rehydration, and pozzolanic reactions. For the field investigation portion of the IHRB-sponsored research, the first application of CGR was made in the summer of 2020 and the second occurred in 2021. The objective of the field study was to strategize the field application process for CGR and evaluate its field performance in pavement shoulder stabilization. To set up the first field study, two CGR-stabilized pavement shoulder sections (250 feet by 5 feet) were constructed in Washington County, Iowa. Two different CGR application methodologies were established: A CGR reclaimed section, constructed by mixing settled CGR residue with the top 2 inches of shoulder materials; and A CGR application on the top section only, constructed by placing a ½-inch layer of settled CGR on the pavement shoulder. A section constructed with Base One (a soil stabilizing agent) was used as a control. CGR used in the test sections was collected at a diamond grinding site, then contained and transported in heavy-duty super-bags. CGR materials were allowed to settle in the bags before draining and dewatering. Figure 1 below illustrates construction of a CGR site in Washington County. The team took advantage of the laboratory study results, using the 20% application rate that lab studies had shown to be optimal, to achieve maximum soil stabilization in their field testing. Researchers compared the performance of the Base One treated section to the “CGR on top” and “CGR blend” sections using a lightweight deflectometer (LWD). Results showed high elastic moduli after seven days for CGR-incorporated sections, with moisture playing a vital role in seven-day and 28-day moduli (weather was a factor in the test cycle, with a lot of rain occurring). Performance measures for CGR-treated sections were very similar to the section treated with Base One, indicating that CGR shows great promise as a soil stabilizer. Dynamic cone penetrometer (DCP) tests were also performed 28 days after CGR application. The CGR-reclaimed section had lower Dynamic Cone Penetrometer Index values, as well as the highest CBR values. In May 2021, a second field demonstration site was constructed to explore the benefit of using CGR as a stabilizer for unbound pavement material at the shoulder. Located in Clinton County, Iowa, the site consisted of four test sections similar to those constructed in Washington County, including a Base One-treated section, a section in which CGR was mixed with shoulder material, a section that received CGR on its surface without reclamation and an untreated control section. Each section was 250 feet in length and 5 feet in width, and a 50-foot gap between sections was provided to avoid overlap between the sections during construction. The shoulder located on the other side of the road from the treated sections was considered an untreated section for field performance evaluation. CGR was again collected and transported from a nearby diamond grinding operation and applied at a 20% rate to test sections. Field evaluation of the site was performed using LWD and DCP tests, as well as visual inspection. One year after construction, researchers observed that the stabilized sections had a lower loss of aggregate than the untreated section. It was hypothesized that CGR stabilization reduces aggregate loss from the shoulder of the road that is caused by wind generated by high-speed truck traffic. Key Takeaways Work performed by the Iowa State University’s Institute for Transportation, when viewed alongside earlier study results from other states, allow researchers to conclude that, based on the soil types and plant communities investigated so far (with a maximum limit of 40 tons/acre), CGR roadside application poses no significant environmental drawbacks and may be beneficial in certain circumstances. CGR-stabilized shoulder sections may reduce aggregate loss. Nebraska Department of Roads and University of Nebraska-Lincoln Investigators from the University of Nebraska-Lincoln’s Department of Agronomy and Horticulture prepared a report titled, “Evaluation of Concrete Grinding Residue (CGR) Slurry Application on Vegetation and Soil Responses along Nebraska State Hwy 31” for the Nebraska Department of Roads (now part of the Nebraska Department of Transportation). The study took place between 2012 and 2014 and evaluated the effect of CGR application on soil chemical properties, existing vegetation and rainfall runoff. Tests were conducted along two state highway sections, one consisting of loam soil and the other consisting of silt loam soil. The CGR effective calcium carbonate equivalent (ECCE) ranged from 13% to 28%. Researchers took road shoulder slope measurements along NE State Highway 31, between mile marker (MM) 28 and MM36, to identify locations with uniform vegetation and adjacency to flat road areas. Sites selected for field experiments had an average slope of 21.3% for MM36 and 12.5% for MM34. Vegetation for all locations was predominantly cool season grasses. Soil textural classes were from loam to silt loam at both sites with pH greater than 7.0. Slurry used for the MM36 experiment was collected in barrels from a diamond grinding operation in Grand Island, Neb., in October 2012 and stored in a temperature-controlled environment. Slurry used at the MM34 site was collected in a ready-mix truck from a diamond grinding operation in Elkhorn, Neb., in May 2013 and was transferred to barrels and similarly stored. Prior to experimentation, all slurry was air-dried, mixed to homogenize and re-wetted to approximate water content on an actual diamond grinding operation. Using various methods, slurry density was estimated to be 10.3 lb gal-1 to 10.8 lb gal-1. Following EPA method 200.7, laboratory procedures were undertaken to determine: the moisture of the dried slurry to adjust application rate; the ECCE; the potassium, calcium, magnesium and sodium concentrations (percent by weight); and the heavy metal content (arsenic, cadmium, cobalt, copper, molybdenum, nickel, lead, mercury, selenium and zinc). In July 2013, controlled slurry treatments were applied at MM36. The application rates of dry slurry (0% moisture) were 0, 4.1, 8.2, 16.4 and 32.9 tons/acre for each treatment. Multiplying by an average ECCE of 13%, slurry rates applied were converted to lime equivalent rates. These rates were 0, 0.5, 1.1, 2.1 and 4.3 tons lime equivalent/acre, respectively. In June 2014, slurry treatments were applied along MM34. Application rates of dry slurry (0% moisture) were 0, 5.5, 10.9, 21.8 and 43.7 tons/acre for each treatment. With an average ECCE of 28%, the lime equivalent rates were 0, 1.5, 3.1, 6.2 and 12.3 tons lime equivalent/acre, respectively. At both sites, dried slurry was mixed with water to achieve a density of 10.5 lb gal-1. Slurry was applied by hand. Key Takeaways For the 2013 and 2014 one-time CGR slurry application, no change was observed in runoff volume, runoff chemistry, ground cover or species composition. The highest CGR application increased soil sodium and pH in the short term (one month) but did not persist after one year of CGR application. Nebraska currently disposes of CGR in accordance with the EPA’s National Pollutant Discharge Elimination System Permit Program. According to the permit, CGR roadside application is restricted to 5 dry tons/acre. Test results demonstrated, however, that the 5 tons/acre limit may be too restrictive. The maximum rate of application during testing was 40 dry tons/acre. While this amount— eight times the current limit—did raise pH, calcium and sodium levels one month after application, testing after one year showed the higher CGR discharge rate did not have a significant negative effect on soil overall. Study authors recommended measurement of existing conditions and the development of field tests that will allow for adjustment of CGR application rates. They also caution that application rates must consider the ECCE, moisture of the CGR and roadside soil texture. International Grooving and Grinding Association and North Dakota State University In 2009, the International Grooving and Grinding Association (IGGA) entered a research project with North Dakota State University (NDSU). This research studied five CGR samples from different areas across the country. The samples were obtained from California Interstate Highway 10 (10/ CA), Michigan Interstate 69 (69/MI), Nebraska Highway 75 (75/NE), Washington Interstate Highway 82 (82/WA) and Minnesota Interstate Highway 94 (94/MN). The research contained three phases: Determine chemical composition and characteristics of CGR; Determine what effect CGR has on the mechanical properties of the soil; and Determine what effect CGR has on plant growth. The chemical composition of the five CGR samples was analyzed with EPA methods 7470A, 6020A/6010B, 9038, 7196 and others. The tests were performed by a commercial laboratory. The CGR samples had a high pH, near 12. Otherwise, the solution phase levels reported were within toxicity limits outlined in the EPA’s Code of Federal Regulations, Title 40, Part 261. In the solid phase, mercury levels were below the reporting limit in four of the five samples, but one was elevated above what is expected in surface soils. Chemical oxygen demands ranged up to 2,210 mg/kg. Other solid phase values were below those generally found in surface soils. None of the semi-volatile compounds analyzed for were found in the samples. The influence of CGR additions from two of the CGR sources on two different soil types was evaluated by infiltration experiments. One of the experiments involved spreading a 2.5 mm layer of CGR, which is equivalent to 14 tons of dry CGR per acre, on the soil surface prior to infiltration. Two other experiments consisted of mixing CGR with soil in the top 3 cm of the infiltration columns at rates of 8% and 25%, which is equivalent to 14 dry CGR tons and 43 dry CGR tons per acre. This phase of the research initiative involved a greenhouse study looking at soil and plant health as a result of adding CGR. Samples 10/CA and 94/MN were air-dried and ground and mixed with two soils at rates of 8% and 25% by mass, which equated to 39 tons and 122 tons of dry CGR per acre, respectively. The two soils were a silty clay (fine, smectitic, frigid Typic Epiaquerts) and fine sandy loam (course-loamy, mixed, superactive, frigid Aeric Calciaquolls). Smooth brome (a common grass used for hay, pasture or silage) was planted into each treatment from seed and was used as the indicator of plant health. At the termination of the experiment, a soil sample was taken, and plant and root biomasses were quantified. The soil and plant samples were sent to a private laboratory and analyzed for several parameters. NDSU researchers were able to draw several conclusions from the CGR research initiative. Soil pH and electrical conductivity will likely increase after CGR application due to the liming potential and total dissolved salts present in CGR. Smooth brome growth will be a function of soil type, CGR, rate of application of this byproduct and, thus, CGR additions to soil will variably impact this plant species. Uptake of calcium, an essential plant nutrient, by smooth brome likely will be accentuated by the application of CGR. Trace metal uptake by smooth brome is variable and will depend on CGR and many soil chemical properties. Soil application rates of CGR likely will not increase trace metal levels in either soils or smooth brome above those found in uncontaminated soils. Application of CGR at the 8% rate (39 tons/acre) was beneficial for smooth brome growth, but application rates greater than 8% should be justified and are not recommended since the actual rate that smooth brome responded negatively was not determined. Key Takeaways This research indicates that CGR applied at less than 40 tons/acre, which is far more than is applied during normal grinding operations, is not harmful to the mechanical properties of the soil, increases the shoot biomass of smooth brome, and has a negligible effect on the trace metals in the soil and smooth brome. The addition of CGR does have a liming potential, which could be either good or bad based on soil type. It is recommended that good pH control measures should be a part of any CGR handling plan. NDSU researchers determined the results of this study do not point to degradation of soil hydraulic properties as a result of CGR application overall. This presumes that longer filtration times are detrimental and speeding of infiltration is not. In most instances this is probably the case, but exceptions are possible. There was an indication that the changes in infiltration due to CGR may moderate with time. Most importantly, the results of this work do not point to any reason, in terms of soil, chemical, physical or hydraulic properties, for restricting the application of CGR directly to soil when the application rates are less than those used in the experiments cited above. Best Practices for Slurry Management In accordance with research showing a lack of negative environmental effects from slurry disposal along roadways, states are changing regulations. For example, Minnesota recently enacted legislation redefining their solid waste definition throughout the state, exempting concrete saw-cut slurry from the solid waste classification and allowing slurry to be spread along adjacent slopes. This was done in part because there was no evidence showing slurry constituted a threat to the environment. IGGA determined best management practices for CGR disposal to help slurry byproduct continue to be handled in a professional, environmentally responsible way. When following the best management practices, studies show slurry is not harmful to soil or plant life and can even be beneficial as a soil additive. SLURRY DISPOSAL In rural areas with vegetated slopes, slurry can be deposited on the slopes as the grinding operation progresses down the road. As part of the contract documents, the engineer identifies wetlands and other sensitive areas where slurry discharge operations are not permitted. The engineer and contractor do a site inspection before diamond grinding to identify sensitive areas. Spreading of slurry should not take place through sensitive areas. Spreading stop and start points should be clearly marked on the shoulder of the road. Slurry generated while grinding in unpermitted areas should be picked up and hauled for disposal in non-sensitive areas on the job. Slurry should not be allowed to flow across the roadway into adjacent lanes. Diamond grinding equipment should be equipped with a well-maintained vacuum system that can remove all standing slurry, leaving the roadway in damp condition after the grinder passes. The vacuumed material should be spread evenly on the adjacent slopes by dragging a flexible hose or other approved device along the slope. Spreading should not take place on the shoulder. Spreading should begin a minimum of 1 foot from the shoulder, with each pass of the grinder moving the spreading operation further down the slope to ensure no buildup of grinding residue. Slurry should not be spread within 100 feet of any natural stream of lake or within 3 feet of a water filled ditch. Efforts should be taken to restrict the spreading operation to above the high-water line of the ditch. At no time will the grinding residue be allowed to enter a closed drainage system. The contractor is responsible for providing suitable means to restrict the infiltration of the grinding residue into the closed drain system. Slurry Collection and Pond Decanting In urban and other areas with closed drainage systems, the slurry should be collected in watertight haul units and transported to settlement ponds constructed by the contractor. These ponds may be constructed within or outside the right of way. All locations should be approved by the engineer. Ponds should be constructed to allow for the settlement of the solids and decanting of the water for reuse in the grinding operation. At the completion of the grinding operation, the remaining water will be allowed to evaporate or may be used in a commercially useful manner, like dust control. After drying, the remaining solids may be used as a fill material, a component in recycled aggregate or any other commercially useful application. The pond area shall be reclaimed to its original condition and vegetated to protect against erosion. Slurry Collection and Plan Processing Slurry should be collected and hauled, as with pond processing. Various plant designs can be used, such as centrifuge and belt press. The plant site should be prepared to control any storm water runoff in accordance with state regulations. The site should be restored and vegetated at the completion of operations. The processed water and solids are to be handled in the same way as the settlement ponds. The site may be within or outside the right of way. Site locations are to be approved by the engineer.

  • Diamond Saw Cut Textures: Improving Pavement Performance and Customer Satisfaction

    Download the printable PDF Diamond saw cut textures optimize performance at a competitive cost Increasingly, specifiers around the world are recognizing the benefits of diamond grinding and other diamond saw cut textures for their pavement and bridge deck surfaces. While most properly designed and constructed portland cement concrete pavements (PCCP) can last for decades with minimal structural damage, functional issues such as ride quality, noise and skid resistance can manifest over time due to surface abrasion and subgrade settlement. In the past, agencies used asphalt overlays to smooth and quiet their pavement. Roadway owners can no longer afford to address their concrete pavement repair needs with short-term solutions such as bituminous patches and thin asphalt overlays. Experience has shown that concrete pavements can achieve their maximum longevity through the use of diamond saw cut textures. Diamond Grinding Diamond grinding existing concrete pavement leaves a surface that is often as good as a new pavement. In reducing the bumps in the pavement surface, the dynamic loading from heavy wheel loads is decreased, resulting in lower stresses in the pavement. Diamond grinding reduces road noise by providing a longitudinal texture, which is quieter than transverse textures. The longitudinal texture also enhances surface macrotexture and skid resistance in polished pavement surfaces. Diamond grinding uses closely spaced diamond saw blades that gently abrade away the top surface of the concrete. On average, the diamond cutting media will contact the pavement surface nearly 27,000,000 times per square yard. This accounts for the gentle removal action, unlike carbide milling operations. The optimized surface is achieved by running the blade assembly at a predetermined level across the pavement surface. The uncut layer between each saw cut breaks off, leaving a flat surface (at a macroscopic level) with longitudinal texture. The result is a pavement that is smooth, safe, quiet and pleasing to ride on. Diamond grinding is increasingly used by roadway owners as a final surface texture on newly placed concrete pavements due to its smooth ride and low noise characteristics. This smooth ride translates into greater longevity by decreasing the effects of dynamic loading. Safety Grooving Pavement grooving is a process where specially designed grooving machines equipped with circular diamond-tipped saw blades are used to saw discrete drainage channels into the pavement’s surface. The blades are mounted and spaced on a horizontal shaft, and are cooled constantly by water pumped from a tanker, which is then recovered by an on-board vacuum system. These discrete channels can be constructed transversely or longitudinally into both concrete and asphalt surfaces. Longitudinal grooving is often performed to provide safer driving on a pavement surface. Studies conducted by the California Department of Transportation showed wet pavement accident rates decreased an average of 70 percent on all the grooved pavements studied, as compared to the control sections, where there was only a 2 percent reduction in accident rates. Dry pavement accident rates did not change as a result of the grooving. The study concluded that grooving produced an overall average 69 percent decrease in accident rates for the highways studied, in both wet and dry conditions. Next Generation Concrete Surface This innovative grinding technique, the Next Generation Concrete Surface (NGCS), is a long-lasting, economical, noise reducing surface texture developed for concrete pavement. It is a diamond saw-cut surface designed to provide a consistent profile absent of positive or upward texture, resulting in a uniform land profile design with a predominantly negative texture. Conventional diamond-ground surfaces produce a positive or upward texture, although they are still quieter than most other concrete pavement surface textures. NGCS is a hybrid texture that resembles a combination of diamond grinding and longitudinal grooving and is the quietest exposed concrete surface available today. Conclusion The use of conventional diamond grinding, safety grooving, and the Next Generation Concrete Surface all provide specifiers with long lasting surface treatments that will help keep pavements quieter, cost effective, safer and smoother. Motorists will appreciate the lack of orange cones during their daily drive to work as these methods allow roadways to be treated in phases using short lane closures during off peak hours. In the end, the taxpayers appreciate the higher road quality and fewer closures for repairs. Enlightened specifiers across the nation are adding these procedures as part of their pavement preservation toolbox.

  • Long-Lived Concrete Pavement: TH 210 in Minn. Achieves a 69-year Service Life—with more Years to Come

    Download the printable PDF With only 3 maintenance cycles and no traffic detours, TH 210 represents value to taxpayers A common issue for DOTs today is what to do with worn concrete pavements that have provided decades of service to the traveling public. The cost of reconstruction can be quite overwhelming, especially with increasing pressure to remediate the maximum number of lane miles. Is it possible to bring 50-year-old pavement back to its original glory? If Trunk Highway 210 (TH 210), west of Brainerd, Minn. is any indication, the answer is a resounding “yes!” The section consists of a 9-7-9 thickness design, meaning it is 9 inches thick at the pavement edges and 7 inches thick at the pavement center line. The center longitudinal joint was tied, while the 15-foot transverse joints were undowelled. It is noted that the pavement was cured over seven days of wet curing which surely helped prevent slab curling and shrinkage cracking. Throughout the pavement’s life it has experienced three maintenance efforts: 1974 (21 years in service): joint resealing was performed. This relatively light construction effort keeps water and debris from getting into joints in locations where the original sealer has deteriorated. Joint resealing will help prevent premature joint spalling. 1991 (38 years in service): pavement was rejuvenated using partial-depth repairs, full-depth repairs and diamond grinding. Partial- and full-depth repairs remove major blemishes such as potholes and significant slab cracking from roadways. Diamond grinding improves ride-quality and friction, bringing the pavement back to its original surface quality. 2013 (60 years in service): pavement was repaired with more partial- and full-depth repairs as well as dowel bar retrofit, then finished with a diamond-ground surface texture. Dowel bar retrofit (DBR) is an innovative technique used to add dowel bars to undowelled pavements, helping reduce slab faulting. This project installed bars in all undowelled transverse joints. Diamond grinding is often paired with DBR to remove any existing faulting, improve ride quality and reduce dynamic loading. Most of the original seven miles of concrete are still in service today, which marks 69 years of continuous service without a marked detour for the traffic. Very few roadways nationally can lay claim to having provided 69+ years of continuous service. Many people would also assume that a long-life pavement such as TH 210 is nearing the end of life, but not so with this road; the International Roughness Index (IRI) in 2022 was measured at a 70 (in/mile). With continued concrete rehabilitation activities, this pavement shows great potential to hit 100+ years of serving the travelling public. In laymen’s terms, an incredible investment was made on behalf of the taxpayers of Minnesota. There are a few key takeaways. First is that pre-emptive maintenance, often referred to as pavement preservation, is necessary to maximize the life of a pavement. Fixing minor issues before they become major is important in optimizing the life cycle cost of pavements. Pavement reconstruction can be costly and DOTs should strive to prevent the need for them with early intervention. Second is that smooth pavements stay smooth longer, so implementing techniques like dowel bar retrofit, diamond grinding and joint resealing early in the pavement’s life will reduce dynamic loads and greatly increase the amount of time a pavement remains serviceable at a high level for minimum cost. For more information, contact the IGGA with any and all questions on concrete pavement preservation and repair!

  • The Next Generation Concrete Surface: NGCS Helps Indiana Cross “the Finish Line”

    Download the printable PDF 42 bridges paved with concrete contribute to smooth, safe interstate highways The expected 2024 completion of a section of Interstate 69 that runs between Martinsville, Indiana and I-465 will be the culmination of 75 years of discussion about connecting southwest Indiana to Indianapolis, the state’s capital and its most-populous city. The Indiana Department of Transportation (INDOT) dubbed the project “The Finish Line,” as it is the sixth and final section of work to be performed developing the 142-mile interstate corridor between Evansville and Indianapolis. Once completed, I-69 will run continuously from Evansville to the Canadian border at Port Huron, Michigan. Construction for The Finish Line, also known as Section 6, includes 27 miles of new interstate highway, as well as work on the heavily traveled I-465 between I-70 and I-65 on Indianapolis’s southwest side. It entails either replacement, rehabilitation or new construction for 42 bridges. Concrete paving will be used on all of them, and many will be surfaced using next generation concrete surface (NGCS). “In the past, Indiana specified transverse tining on bridges for new construction, but for the Section 6 work, they specified next-generation concrete surface, or NGCS, which incorporates longitudinal grooving,” said Kevin Sorrell, owner of Americut® Diamond Grinding & Grooving, who completed work on seven bridges during the 2022 construction season and will undertake others in upcoming projects. Developed by Purdue University in conjunction with the American Concrete Pavement Association (ACPA), International Grooving & Grinding Association (IGGA) and the Portland Cement Association (PCA), NGCS represents the quietest non-porous concrete surface to date. It was created to achieve a concrete pavement surface that has good frictional characteristics and decreases pavement noise. It not only has the benefit of decreasing tire/pavement noise, but is shown to provide a smooth, uniform ride and increase driver safety, especially in wet weather conditions. Longitudinal grooving improves lateral stability for vehicles on the roadway and reduces hydroplaning potential. INDOT first tested NGCS in 2014 while participating in a demonstration project funded by the Federal Highway Administration’s (FHWA) Highways for LIFE (HfL) initiative, which has the objective of advancing longer-lasting highways and bridges using innovative technologies and practices. An FHWA grant was awarded to INDOT for research into a variety of concrete surfaces, including NGCS. According to an INDOT technical brief, the department looked to NGCS to “provide a significant reduction in tire-pavement noise and the ability to maintain friction for increased skid and hydroplaning resistance.” NGCS was used to rehabilitate the I-65/I-465 interchange in southeast Indianapolis. In the years since NGCS was first tested in Indiana, more longitudinal surfaces have been installed, but the use of NGCS on bridge surfaces as part of the Section 6 work represents major strides in its adoption. Nine bridges on I-69 between Fairview Road in Johnson County and I-465 in Indianapolis (three mainline bridges and six low-speed bridges) were tested for smoothness after construction was complete. Results showed that the pavements were very rideable. The three mainline bridges occupy asphalt-paved sections of roadway, but their smoothness is comparable to the asphalt sections and the transitions between paving types were also determined to be very good. “The Next Generation Concrete Surface—also called NGCS—used by INDOT on this project was developed to meet the demands of today’s driving public, as well as those living in the vicinity of dense roadway traffic,” said John Roberts, Executive Director, IGGA. “It is a cost-effective, super smooth concrete surface with low noise characteristics, which makes it an ideal surface for urban interstates, arterials and residential areas where tire/pavement traffic noise is a concern. It is fortunate that the taxpayers of Indiana have transportation officials that are willing to look at best practices abroad and develop pavement systems that are economical, sustainable and safe. These challenging times require innovative thinking and INDOT has shown they are up to the challenge.” Team Members ·         Americut® Diamond Grinding & Grooving ·         Diamond Coring Concrete Cutting Contractors

  • Asphalt Diamond Grinding: Road owners increasingly see benefits of grinding and grooving new asphalt pavements

    Download the printable PDF Grinding proves a cost-effective solution for achieving smoothness, safety and comfort Diamond grinding improves pavement friction characteristics while providing a smoother ride—and it can be used on asphalt or concrete. Unlike overlays, grinding can extend the construction season, even in low temperatures (above freezing), and it can be performed on new or existing pavement. Commonly used on concrete for over 60 years, diamond grinding is increasingly used on asphalt as well. Numerous states have used it to improve their roads’ smoothness and friction characteristics, while creating a quieter ride. South Carolina SC 544 in Conway, SC is a four-lane highway serving several of the state’s Grand Strand beach communities, and three separate sections were repaved in 2020. Due to the busy nature of this roadway during the vacation season, SCDOT chose to place the asphalt pavement in a single lift to expedite the project, with the final surface being diamond ground. Previous research proved that density could be obtained within a single, seven-inch lift. The issue was how to achieve smoothness. Typically, a final surface layer of asphalt is applied for this purpose, but for the SC 544 project, grinding of the single lift of asphalt pavement was used instead—a move that not only saved money and reduced traffic disruption but conserved resources. Diamond grinding also allowed contractors to achieve a smooth tie in between bridges and the surrounding pavement—another classic trouble spot in paving. A total of 106,632 square yards of pavement were diamond ground, creating an ultrasmooth, high friction and extremely quiet riding surface. The SCDOT Office of Materials & Research conducted rideability tests, with the first test being performed after the new asphalt pavement was completed, prior to diamond grinding, and a second one performed after the diamond grinding was complete. After grinding, IRI measurements were as low as 21 inches-per-mile and the average smoothness was 35 inches-per-mile. The average reduction in roughness was 56 percent. Missouri When the asphalt surface of Missouri’s U.S. 412 displayed cracking and increased roughness, diamond grinding was selected as the primary preservation treatment. Grinding had already been used successfully in the state on new asphalt pavement to mitigate flushing (bleeding) and loss of texture, as well as to meet MoDOT’s smoothness specification (a maximum average IRI of 80 inches per mile). IRI data collected on interstate projects that specified grinding showed that roughness decreased an average of 40 inches per mile. The department expected the preservation treatment on U.S. 412 to extend the pavement’s life by five to seven years, which is close to the life span of a thin overlay treatment—yet is achieved for significantly less money. Prior to commencing the diamond grinding operation on U.S. 412, potholes were patched and repaired. Since the road’s wheel paths were rutted, the middle hump—½ to ¾ inch—was removed using grinding to improve the ride and drainage characteristics. After grinding, the asphalt surface had improved friction and a smoother ride. New York New York state allows up to 5 percent of a pavement project’s total surface area to be diamond ground for ride quality remediation. Although typically this encourages use of diamond grinding to address localized roughness, the contractor for the resurfacing of I-787 in Watervliet approached the opportunity differently. The entire allowable 5 percent surface area was allocated to diamond grinding two ramps. Diamond grinding the entire surface of the ramps achieved a 40 percent reduction in IRI. Not only did the ramps turn out to be some of the smoothest and quietest sections of the entire project, but the contractor managed to achieve ride quality pay incentive in these pavement sections. Safety Grooving Another diamond saw-cut surface texture being applied to asphalt pavement is safety-grooving. This process involves cutting narrow, discrete grooves into the pavement surface to reduce hydroplaning potential and is a valuable asphalt pavement preservation method. Grooving is performed in areas where the texture on an aging asphalt pavement has become worn, flushed and polished, and there is concern that water on the roadway cannot be evacuated quickly enough. Ohio Rain and snow can compromise road surface friction, in turn compromising safety. Even for surfaces with adequate friction measurements, limited sight distance or challenging roadway configurations can cause an above-average accident rate. The Ohio DOT has found that increasing the pavement surface macrotexture in these areas can be helpful. In the 2010s, ODOT performed grooving and grinding of asphalt in three locations. When skid testing for a section of S.R. 126 in Hamilton County showed a lack of macrotexture, grooving and grinding resulted in a nearly 50% improvement in skid number (SN) 40-mph smooth tire values. Wet-road crashes were also occurring on the I-90 Innerbelt Curve in Cuyahoga County. Various treatments were considered by ODOT to reduce accidents at this location, and some lanes were subsequently ground and grooved. The diamond grooved section improved the average SN 40-mph smooth tire value by more than 50%, increasing it to 1 1⁄2 times its previous value. On I-75 in Montgomery County, commercial trucks were experiencing a higher-than-expected crash rate while navigating a heavily traveled high-speed zone with multiple curves. Skid tests showed that macrotexture required improvement, so grinding and grooving were performed on a 2-mile stretch of the road. The diamond-grooved section improved the average SN 40 smooth tire value by more than 70%, increasing it to 1.7 times its previous value, and crash data showed a dramatic reduction in accidents. Conserving resources, increasing safety, simplifying construction schedules and saving money are on the “wish list” of every road owner. Diamond grinding and grooving can help achieve all three, whether on concrete or asphalt pavement.

  • The Next Generation Concrete Surfaces (NGCS): NGCS Valuable Alternative to Noise Walls

    Download the printable PDF NGCS reduces noise, improves safety and ensures smoothness In 2019, the Minnesota Department of Transportation (MnDOT) announced a project to reconstruct and expand both directions of I-94 between TH25 in Monticello and TH24 in Clearwater, approximately 35 miles northwest of Minneapolis. The prime contractor for this design-build project was HcPCi, a joint venture between Hoffman Construction and PCiRoads, who are primarily grading and concrete paving contractors respectively. This $104 million dollar project called for approximately 14 miles of roadway to be reconstructed and for construction of an additional general-purpose lane in each direction, taking the roadway from four to six lanes, and included mainline segments of both asphalt and concrete. Primarily, the project called for expanding the roadway to the inside including a concrete median barrier. Locke Lake is a small lake adjacent to I-94, with about 2.6 miles of shoreline which is substantially developed with numerous single-family residences. HcPCi submitted an Alternative Technical Concept (ATC) to MnDOT, suggesting a change to the agency’s design. The ATC proposed maintaining the existing median width as opposed to constructing a concrete median barrier. The newly proposed layout widened the roadway to the outside, closer to the lakefront than what would have resulted from the initial MnDOT design. MnDOT is required to analyze noise impacts in various scenarios, and this location met MnDOT’s criteria for noise mitigation. The standard mitigation technique requires the construction of expensive noise walls. However, the geography of the site and the proximity of the lake to the roadway made the construction of noise walls exceedingly difficult. In response to this challenge, HcPCi provided data showing that using next generation concrete surface (NGCS) would provide noise reduction meeting MnDOT’s mitigation requirements. NGCS, a hybrid texture that resembles a combination of diamond grinding and longitudinal grooving, is the quietest non-porous concrete pavement surface available. Furthermore, it creates a smooth surface (enhancing rideability and pavement durability) and improves safety by reducing hydroplaning. Additionally, MnDOT maintenance personnel have reported that NGCS also reduces the amount of salt required during snow and ice operations compared to traditional surfaces. In 2022, the I-94 expansion project was completed with NGCS installed on the approximately 1/3-mile of roadway that was close to the lake, a more economical solution than expensive noise walls. MnDOT even expanded the scope of the project and installed NGCS in the westbound lanes of this stretch, as well. “Achieving success without noise walls represents a change in ‘business-as-usual,’” said Matt Zeller, executive director, Concrete Paving Association of Minnesota (CPAM). “Earlier applications of NGCS in Duluth, Minnesota demonstrated that the surface also enhances safety, so NGCS offers many advantages. NGCS provides a very smooth surface and has even been noted to hold salt better in the wintertime, reducing the overall use of salt and therefore providing an environmental benefit.” Team Members PCi Roads Concrete Paving Association of Minnesota

  • Diamond Grinding: Production or bump grind, what is the better value?

    Download the printable PDF. Learn how to apply grinding to optimize $$ spent. DOTs across the country diamond grind pavement to optimize pavement performance while minimizing their spending, often employing it to smooth out uneven spots in a pavement. They specify bump grinding—that is, grinding restricted to just the uneven areas—in an effort to address only troublesome locations and thereby conserve resources while meeting smoothness requirements. However, when it comes to diamond grinding, this selective approach is not always the most effective one. When leaving short sections of unground pavement between bump-ground segments, it is possible to increase the cost of the diamond grinding procedure while reducing the best outcome for the pavement surface. Increased costs can occur when machine operators stop and start a grinding pass, lifting the grinding head and then taking the time to reset it at the appropriate depth when addressing the next bump. This increases the overall amount of time, effort and fuel consumed, thereby increasing costs. While bump ground surfaces can significantly improve ride quality and increase pavement longevity, nothing beats the performance of a continuously ground, production surface. Performing a production grind, i.e., grinding the pavement full lane width and length, to a specified maximum IRI measurement, will achieve better results in terms of ride quality, friction, sound, fuel emissions, and aesthetics at a lower square yard cost in most cases. Bump grinding is normally based on hourly pricing as opposed to continuous production grinding which is typically based on square yard pricing. With this in mind, paving project managers and rehabilitation plan designers often lay down numerous start and stop points for the grinder operator to navigate thinking that they are saving money by doing so. This is often not the case. On the contrary, combining some of these patches into a continuous grind can actually be less expensive and provide a better end product for the driving public. Additionally, when pavement engineers are at the drafting table designing new, heavily phased paving projects, they should anticipate a significant amount of bump grinding and thereby consider incorporating continuous diamond grinding over the entire project to obtain the best value and performance from the grinding product. In summary, each project should be evaluated carefully before the work begins to determine where diamond grinding will be required and how best to approach the task to achieve a smooth, safe and economical pavement surface. Best results will always be achieved laying out a plan in advance, hiring a reputable contractor and trusting the advice of your grinder operator. To learn more, contact the IGGA or visit

  • Diamond Grinding: A Safe, Sustainable, Quiet and Cost-Effective Solution to Better Roadways

    Download the printable PDF Over the past hundred years, the expectations and capabilities of highways have shifted. In the 21st century, drivers and passengers expect long lasting, efficient, comfortable and safe travel on highways. Engineers can achieve those standards—and also meet the challenges of sustainability, noise levels, urban head island effect and budget—through the use of pavement diamond grinding. Diamond Grinding Offers Solutions to Many Pavement Challenges Highways have come a long way over the last 100 years. In generations past, the goal of roads was to keep people and goods moving to market and prevent vehicles from getting stuck in the mud of country roads. In the 21st century, the expectations and capabilities of highways have shifted. Today, users expect long lasting, efficient, comfortable and safe passage from location to location. When evaluating pavements for surface characteristics, three of the most important considerations are sustainability, safety and comfort. There are many statistical realities that engineers can take advantage of when trying to achieve these goals. First implemented in the early 1960s, pavement diamond grinding is the process of stacking diamond saw blades next to each other on a machine-driven shaft. As this shaft spins, the diamond blades are lowered on to the surface of the pavement. They abrade the surface when they contact the pavement material, removing high spots in the road profile and leaving behind a superior surface texture. Diamond grinding is like using a belt sander to remove edges and knots from a wood plank. By making the surface smoother, the number of localized and continuous elevation changes in the pavement surface are reduced. Diamond grinding has many additional benefits, particularly related to carbon and cost savings, less vehicle wear and tear, and increased safety. A Pavement that Lasts In a 2000 article by the FHWA, Enhancing Pavement Smoothness, data was evaluated showing that the smoother a pavement is, the longer it will last. This is the result of reduced frequency and severity of dynamic loads applied to the pavement surface. Highways typically are designed for 18-kip axel loads. When vehicles bounce due to a bump, the weight of the vehicle paired with the down force induced by gravity can result in an impact load more than 1.5 times the design capacity. When this increased loading continuously happens throughout the day, the structure of the pavement can experience significant fatigue. This premature breakdown of the pavement structure will cost owner agencies because they will not experience the expected lifespan of their investments. Similarly, the surface deterioration of these failing pavements will create cracks and potholes that pose a safety risk to the traveling public. The longer maintenance needs are left unattended, the more likely issues will expand—which can quickly increase the cost to repair. Surface damage that is fixed almost immediately may have negligible negative impact to users and modest repairs costs, but damage left for an extended period can propagate an area of structural damage, requiring a more expensive repair in the future. Transport Notes from the World Bank evaluated the relationship between maintenance timing and cost on South African highways. It was determined that three years of maintenance neglect resulted in six times the repair cost. Five years of neglect resulted in up to 18 times the repair cost. This relationship is due to the level of invasive work required to remediate a pavement section. For example, if a concrete pavement suffers from slab curling, the very cost-effective diamond grinding treatment can be performed using heaving machinery and minimal hand work. However, if that pavement is left to be beaten by dynamic loads for an extended period, the need for crack and full-depth repairs will be more prevalent—and drive-up costs. Reducing the International Roughness Index (IRI) before significant damage is done will mitigate this untimely wear and tear on pavements, resulting in a more efficient use of tax dollars and building materials. Case Study: Asset Management in Arkansas The Arkansas Department of Transportation (ArDOT) collects data on interstates every year. Once data collection is complete, it is processed and a pavement condition index (PCI) summary is calculated, using a weighted average of four types of pavement metrics: environmental cracking, structural cracking, roughness, and rutting. Conditions are assessed using FHWA threshold criteria for each 1/10-milelong pavement section. The index is then used to assign a pavement condition rating, or “grade,” which describes the pavement condition of the state highway system as good, fair, or poor. Pavement Preservation Efforts Maintain Rideability at a Competitive Cost Several sections of the pavement on I-40 in Arkansas are constructed of concrete, and a 4.3-mile section in Johnson County, constructed in 2002, provides one example of the advantages of pavement preservation. This portion of I-40 sees an average daily traffic (ADT) of 28,000 vehicles per day, with 36% of that traffic being trucks. The pavement is constructed of a 4-inch stone base, 4-inch treated permeable base and 12-inch jointed concrete pavement. The outside lane is 14 feet wide with an 8-foot asphalt shoulder. The cost of the 12-inch concrete pavement at the time of original construction was $24.15 per square yard in 2002 dollars, for a total of $9.4 million. At the time of construction, the pavement had an average international roughness index (IRI) of approximately 100 inches per mile. Pavement preservation was triggered in 2019 when an IRI of 112 was measured, since the department’s goal is to keep IRI measurements close to 100. No maintenance had been performed on the pavement since it was built; the only maintenance activities had been periodic asphalt shoulder patching and cleaning of edge drains. In 2020, the department performed the concrete pavement preservation (CPP) work. The existing pavement was in excellent structural condition with very few cracked slabs, so CPP consisted of patching 138 square yards—or 0.1% of the area—along with diamond grinding for smoothness and joint rehabilitation. The project was ground to an average IRI of 43 inches per mile. The cost for diamond grinding was $825,000 and the cost for joint resealing was approximately $300,000. The total cost for the project was $1.125 million, or $65,400 per lane mile. Based on the positive outcome of the original concrete construction, combined with diamond grinding and other minimal CPP at the 15- to 18-year point, ArDOT integrated additional diamond grinding and CPP into its road management efforts, notably planning their use on two large sections on I-30. Save On Fuel With more attention than ever being focused on energy conservation, vehicle fuel efficiency, and new alternatives such as hybrid cars and biodiesel, few people realize the significant impact that road rehabilitation methods like diamond grinding can have on energy use. Research by the MIT Concrete Sustainability Hub concluded that roughness and deflection of pavements impact the fuel economy of vehicles that traverse the pavement. When the surface of a pavement is smooth, vehicles traverse it more efficiently, with more of the expelled energy dedicated to forward movement rather than fighting vertical bouncing movements. When highway maintenance crews reduce the IRI of a pavement by 40%, it saves truck operators about .002 gallons of diesel or about .7 cents per truck per mile, according to IGGA’s Fuel/Carbon Savings Calculator. While this figure seems negligible, it has a significant impact when entire highway sections are evaluated. Even when considering alternative fuel vehicles, such as electric vehicles (EV), it is important to recognize that the battery of an EV traveling on a smooth, diamond ground pavement will carry the vehicle for a longer distance because it can move more efficiently. Although at this time research has not been done to show exactly how much improvement takes place, MIT researchers suggest the expected increased distance would be the same as the percent of fuel saved for their gasoline-powered counterpart. By removing faulting, slab warping, studded tire wear and unevenness resulting from patches, diamond grinding creates a smooth, uniform pavement profile. The longitudinal texture created by diamond grinding also enhances macro texture and skid resistance in polished pavements. Diamond Grinding Uses Fewer Resources Research shows a correlation between rough pavements and reduced driving speeds, which can lead to congestion. Pavement congestion can increase drive times and idle time on highways, resulting in higher fuel consumption. Smooth pavements can help increase driving speed thus reducing roadway congestion. The nature of diamond grinding makes it one of the most efficient pavement preservation techniques. It can be completed in short lane closures for less time than typical asphalt overlays, and may even be performed in a rolling closure next to live traffic. Overlays require the mining, producing, and hauling of virgin material. Each one of these steps has a significant cost and carbon impact to the project. Comparatively, a diamond grinding project only requires the removal of a small amount of material from the jobsite in the form of slurry. It is also important to consider the life-cycle cost of paving and rehabilitating both types of pavement surfaces. An asphalt surface should be replaced approximately eight to 15 years into its life with a new layer of asphalt. In that time frame and given the material hauling parameters, it is unlikely that asphalt overlays have the opportunity to be cost or carbon neutral. Diamond grinding on concrete pavements can last decades before requiring remediation. Pair this with the aforementioned material mining and hauling benefit, as well as the re-opening of concrete surfaces for carbon sequestration, and cost carbon neutrality becomes commonplace for diamond grinding. Highways with heavy traffic can even show a net negative cost and carbon impact. In fact, milling an asphalt overlay off an existing concrete road and then diamond grinding can be even more fuel efficient than milling and replacing with a 2-inch new overlay. How Much Fuel can be Saved? The Federal Highway Administration (FHWA) provides data about the fuel used in various aspects of highway construction including hauling, site preparation, producing materials and placing (construction). Using FHWA’s information, the diesel fuel used to build a mile of asphalt and concrete pavements can be calculated and is compared in the ACPA document QD023P. Using that FHWA information, as well as information from actual diamond grinding and joint resealing operations, the table compares the fuel consumption of a typical 3-inch asphalt overlay over an existing concrete pavement. It also compares the fuel consumption of a typical milling and 2-inch overlay operation that repairs a concrete road previously overlaid with asphalt. It then compares the fuel consumption for both options to diamond grinding and joint resealing. » It takes an average of 3,215 gallons of fuel per mile to place a 3-inch asphalt overlay over an existing concrete pavement. » It takes an average of 3,043 gallons of fuel per mile to mill and overlay with 2-inches of asphalt, a concrete pavement previously overlaid. » It takes an average of 935 gallons of fuel per mile for diamond grinding and joint resealing. Safer Surfaces Highway users are constantly at risk of motor vehicle accidents. Rough pavements increase this risk because they can cause the suspension of the vehicle to bounce. In extreme instances, this can result in tires leaving the surface of the pavement, causing them to momentarily lose friction. Potholes also can jolt the steering mechanism of a vehicle, causing the operator to lose control. Proactive drivers may even swerve to avoid potholes, causing them to depart from their driving lane and increasing the risk of contact with vehicles in adjacent lanes. Surface irregularities may impact drainage during wet weather events, increasing the risk of hydroplaning. Additionally, aggregates (rocks) dislodge and ravel out of an asphalt rubber overlay as it ages. These loose rocks lay on the pavement, acting like marbles on the roadway surface and reducing the braking ability of tires. This raveling of the pavement is also the reason the asphalt rubber gets louder over time. The University of Maryland compiled data from the United States, Australia and New Zealand. The results suggested a linear correlation between pavement roughness and vehicle accidents. The document also noted that pavements with 10 millimeters (mm) of rutting showed a higher risk and higher severity of vehicle accidents. Concrete pavement preservation (CPP) with diamond grinding is proven to be safer, with 42% fewer accidents in all-weather conditions when compared to a tined pavement surface. And construction required to perform diamond grinding is a safer alternative as well. Diamond grinding can be constructed all year long in day and night shifts without closing the freeway. This allows for construction at times that least impact the consumer, unlike asphalt rubber, which can only be placed during certain times of the year. Diamond grinding significantly reduces the amount of traffic congestion and consumer delays during construction as well, which results in far fewer accidents. Safe Surfaces Reduce Vehicle Maintenance The FHWA recognizes that smooth pavements reduce the need for maintenance on vehicle suspension and tires. Research cited in the Journal of the South African Institute of Civil Engineering concluded that in 2004, California drivers using roads in disrepair paid an average of $700 in vehicle maintenance and replacement cost compared to a national average of $400. The 43% increase in repairs to vehicles associated with road roughness was coined “the hidden tax of California road users.” These costs are significantly more when applied to commercial trucking equipment compared to passenger vehicles. This same function also translates to the goods being transported, as rough roads impact the condition of products before hitting store shelves. Tests have shown that roughness, as measured by the IRI, grows faster on asphalt versus concrete and asphalt will be rougher at 20 years old. Concrete pavement experiences a much slower deterioration and can take decades to reach the same condition level. Mill and fill must be performed on asphalt pavement about every 10 years to keep roughness under control; even then, it experiences periods of poor condition compared to concrete, which can be diamond ground every 25 years and remain fairly smooth. Because CPP-treated pavements stay smoother, they provide a quieter, better ride for motorists as well. Lower Roadway Noise Rough pavements and transversely tined pavements have a higher decibel reading compared to smooth and longitudinally ground pavements. According to the FHWA, highway noise is typically 70 to 80 dB(A) when standing 50 feet from the highway. Sounds in excess of 80dB(A) can cause hearing damage after extended exposure. The World Health Organization (WHO) attributes excess noise pollution to social, physical and mental health issues. Highways that run through urban areas can make it difficult for people to carry on conversations and interrupt concentration, having a negative social impact. Excess background noise has been shown to increase heart rate as well as increase potential for mental health episodes, creating an increased risk of physical harm, according to the WHO. Typical building codes for noise in the United States requires 45 to 55 dB(A) in living spaces during the day. This means that highway noise in urban areas must be kept at manageable levels to allow developers to build livable communities near highways. Case Study: California State Route 85 Tested for Quietest Pavement Route 85 near San Jose, Calif., has a high level of traffic—and noise is a major concern for local residents. With a truck ban in effect for Route 85, the main traffic noise source is from the interaction between passenger vehicle tires and the pavement surface. Parts of Route 85 are depressed and there are sound walls along the roadway. Previous noise studies have indicated that raising the height of the existing sound walls would not be effective in further reducing the noise levels. In response to these issues and complaints from the local citizens, a .88-mile diamond grinding test section was constructed between DeAnza Blvd. and Saratoga Ave. The citizens responded favorably to the test section. In June 2005, Caltrans contracted with Illingworth and Rodkin, Inc., to conduct tire pavement noise evaluations of the existing longitudinal tined surface and the diamond ground texture. The tire pavement noise evaluations found the diamond ground surface was almost 2.5 dBA lower in overall noise level and exhibited significantly less variability. The frequency content of the diamond ground texture was superior to all others, particularly in the 800- to 1,250-hertz range where human hearing is particularly sensitive to these frequencies. According to the Valley Transit Authority (VTA) project report, “diamond grinding caused a downward shift in the tonal characteristics of the sound and decibel reductions at frequencies that are easily heard by human ears.” The public responded favorably to the test section and, as a result, the VTA constructed a full-scale diamond grinding and grooving project on Route 85 between I-280 and Highway 87 in 2005. The goal of the project was to remove the roadway’s existing surface texture that was creating the offending sound. For the safety of the public and construction workers, traffic control measures including temporary lane closures and detours were used when needed. The cost of the project, which began in mid-2005 and was completed in mid-2006, was $9 million. The result for the citizens who had complained of noise from the highway before the changes is a quiet highway that has significant reduction in decibels and improvement in tonal qualities. Diamond Ground Concrete Proves to Be an Effective Way to Preserve Pavements Since its inception in the 1960s, diamond grinding has proven time and again to be the best solution to many common roadway issues. From its ability to provide a long-lasting surface for motorists while also reducing fuel and maintenance costs, to its natural tendency to capture carbon and reduce greenhouse gas emissions, diamond ground concrete pavements are a cost-effective option for roadway repair and replacement. Reduce IRI and Improve Roadway Smoothness As old concrete pavements begin to wear, they can lose their friction properties. Maintaining these properties is key to keeping highway systems safe for consumers. The State of Wisconsin determined that diamond ground surfaces resulted in a 42% reduction in all-weather vehicle accidents and a 57% reduction in wet weather accidents when compared to tined surfaces. In a publication in the Journal of Performance of Constructed Facilities, data was evaluated to determine estimated expected performance improvements due to diamond grinding in Texas. Data showed a single pass of diamond grinding reduces IRI by approximately 40%. Many contractors affiliated with IGGA have reported even better results. When encountering extremely rough or faulted pavements, a high-quality finish can be achieved by implementing a light bump grind first to remove localized roughness before the full production grind. The same Journal entry also reported a 30% improvement in skid number (SN), the metric used to identify friction issues in pavements. Case Study: Kentucky Improves Smoothness with Diamond Grinding Through implementing pavement management systems, Kentucky serves as an example of successfully staving off the need for extensive and expensive pavement reconstruction. By exploring the options available with CPP, the Kentucky Transportation Cabinet made strides in determining data that can be used to trigger CPP. The most common CPP technique used in Kentucky is diamond grinding. The state has been performing diamond grinding since the mid-1990s, but at that time they were just exploring options—little diamond grinding was being done. That changed in 2007, when the state increased its pavement preservation activities in an effort to improve the roadway system. Between 2007 and 2012, 536 interstate lane miles were diamond ground statewide, primarily in the Louisville area. During this period, IRI measurements for Kentucky’s interstate concrete pavements improved from an average of 112.1 inches per mile to an average of 74.5 inches per mile—the longest sustained improvement in the state’s IRI and their lowest recorded average IRI ever. The improvement was attributed to the 536 miles of diamond grinding that had taken place. The combined cost of the diamond grinding projects (including traffic control, patching, joint resealing and more) was $101 million, or $188,000 per lane mile. Reconstruction costs would have been an estimated $1.5 to $2.5 million per lane mile, so CPP saved the state more than $1 billion. The expected pavement life extension for ground pavement is 10 to 15 years. The average cost of diamond grinding in Kentucky during this five-year period was $2.75 per square yard. Of the state’s approximately 62,000 lane miles of roadway, about 1,800 are concrete; 820 of their 3,800 interstate lane miles are concrete. Therefore, finding an effective way to prolong concrete pavement life while improving performance is vital. When assessing its road network for needed repairs, the main indicator that Kentucky uses is pavement smoothness. Inertial profilometers are used to annually measure roughness on the interstate system and IRI values greater than 130 inches per mile will generally trigger CPP. Undertaking CPP is contingent on a situation in which there is moderate to low cracking and faulting. (Kentucky defines low faulting as ¼ to ½ inch. Faulting greater than ½ inch generally would necessitate full restoration rather than preservation.) Similarly, if a third or more of the slabs needed replacement, full restoration typically would occur. Pavements with IRI measurements lower than 130 still could trigger CPP if it appeared that cracking and faulting were about to become a major problem; conversely, if a road is expected to require major work (such as widening) within the upcoming five to 10 years, the cabinet will not recommend it for CPP. Inherent Sustainability While new technologies and modes of transport receive a lot of attention as carbon-reducing strategies, traditional pavements—specifically, concrete pavement—also can offer sustainability benefits. Concrete’s sustainable qualities, especially when paired with diamond grinding, are numerous. Diamond ground concrete pavements require little maintenance when compared to heavily modified thin-lift asphalt treatments and are naturally sustainable with the following attributes: Concrete pavement is produced locally, with local labor, supporting local communities, which is great for the economy. Concrete has a high level of light reflectivity, making it safer to drive on at night. During the day, heat and light are reflected, reducing urban heat islands (UHI). Concrete pavement increases fuel efficiency by 3% to 7% for semitrucks (saving 40 gallons per 1,000 miles driven) with similar savings in cars and light-duty trucks. Concrete is not petroleum based. There is no odor or stench when concrete pavement is placed or reheated daily by the sun. Concrete is fully recyclable; more than 140 million tons of concrete are recycled and reused every year. In addition to carbon-reducing changes occurring at the materials production level, in-service concrete contributes to carbon neutrality by absorbing atmospheric carbon. This carbon capture, known as carbonation, occurs when hydrated portland cement is exposed to atmospheric CO2, which reacts with the water and calcium compounds in concrete and produces calcium carbonate. Carbonation takes place over the lifetime of a pavement; while there is a risk of the rate of carbonation slowing over the years due to the pore-blocking effect of the calcium carbonates being formed, it is possible to remove the carbonated surface and expose a fresh, uncarbonated layer. The simplest way of doing this is by diamond grinding—a technique that is commonly performed as part of pavement preservation. Diamond grinding as often as every 10 to 15 years will enable a concrete pavement to restart the carbonation process and continue offsetting the carbon emitted by concrete production. For example, Chisago County, Minn., diamond ground 26.4 lane miles on I-35 and measured the carbon savings. Using the fuel/carbon calculator available on the IGGA website, it was determined that while the carbon dioxide released by equipment to perform the work was around 500,000 pounds, the annual carbon savings associated with improved ride quality and carbon sequestration was 152,000 pounds. That means that after only 3.5 years of service, the pavement will be carbon negative. While the cost of diamond grinding was approximately $850,000, the 10-year cost savings for users was in excess of $3.5 million in fuel alone—$66,000 dollars in estimated fuel savings or 16,139 gallons per mile per year. Many engineers lean on asphalt overlays as the most effective repair method for ride quality and surface texture issues. While in extreme cases this may be the best viable solution, the mining of new materials, hauling of new materials to a job site, and loss of carbon sequestration benefits make asphalt a more expensive and less environmentally conscious choice when compared to diamond grinding. While a diamond ground surface can remain effective in excess of 20 years, states asphalt overlays of concrete can last about 12 years when properly maintained. Twelve years of service is not enough time to offset the environmental benefit of a smoother riding surface. A diamond ground pavement is the only carbon negative surface treatment with a higher return on investment than asphalt overlayed sections. Harness the Power of Data The amount of carbon offset achieved via carbonation can be impressive. According to the MIT CSHub, carbonation “has been estimated to offset up to 43% of calcination emissions that occur during cement production.” But how can one determine the actual amount of carbon capture that is occurring on a given stretch of concrete pavement? The answer is to quantify inputs, then perform the carbon accounting. To help with this, MIT’s CSHub has made available a material- and facility-specific calculator for carbon uptake in concrete. With its broad focus—initial concrete mixture, location and exposure characteristics during the concrete’s service life, and eventual stockpiling conditions—the tool can help users assess the true rate of carbon capture for a given area of installed concrete. Lower Temperatures Heat is the number one weather-related killer in the United States, and city planners and other decision-makers are beginning to consider ways to enhance urban heat island (UHI) resilience. The UHI effect is caused when features of the built environment absorb and re-emit the sun’s heat more than a natural landscape. Concrete pavements are lighter in color than asphalt pavements and twice as reflective when new, leading to a reduced UHI. The result is lower temperatures in the areas surrounding concrete pavements that have been remediated using diamond grinding as opposed to ones overlayed with asphalt. A surface’s degree of reflectance is known as its albedo, which is expressed as a numerical value between 0 and 1. A light-colored object has a high albedo—near 1, or 100% reflectance. A dark-colored object has a low albedo—closer to 0. The albedo of a new asphalt pavement is about 0.05. Aged asphalt, which has faded to a lighter color, generally has an albedo between 0.10 and 0.18. New, cured gray cement concrete pavement, however, has an albedo in the range of 0.35 to 0.40. As concrete ages, it tends to darken because of dirt and tire wear, so older concrete may have an albedo in the range of 0.20 to 0.30. The use of light-colored aggregates, white cements and slag cements can improve albedo; white cement concrete pavements have albedos in the range of 0.70 to 0.80 when new and 0.40 to 0.60 after aging. Concrete surfaces become darker over time due to oxidation and petroleum-based fluids leaking from vehicles. Diamond grinding removes this darkened layer, re-establishing the like-new light color of the pavement and enhancing the reflective nature. Case Study: High Albedo Lowers Temperatures Phoenix is one of the nation’s fastest-warming big cities. In August 2021, IGGA partnered with the American Concrete Pavement Association (ACPA) to conduct infrared testing of diamond ground concrete and asphalt-rubber-surfaced pavements in the Phoenix area. Data was collected for three pavement structures on eastbound SR 202 between 40th Street and Dobson Road. A concrete pavement with a diamond ground surface. A concrete pavement overlaid with a 1-inch-thick asphalt rubber surface. An asphalt concrete pavement overlaid with a ½-inch-thick asphalt rubber surface. Test results showed higher temperatures on the asphalt rubber compared to diamond ground concrete over a 24-hour period. Diamond ground concrete surfaces consistently remained cooler. Just before sunrise, diamond ground concrete measured 1 degree to 10 degrees F cooler than asphalt rubber surfaces. At peak temperature, diamond ground concrete was 27 degrees F cooler than asphalt pavement overlaid with asphalt rubber. As cities respond to rising temperatures, diamond ground concrete surfaces offer a solution to increase albedo, reduce the UHI effect and overall greenhouse gas emissions, improve the health of local residents, and decrease roadway maintenance costs. Solutions Emerge for Next-Generation Concrete Preservation As good stewards of the public domain, engineers should always strive to help users save money and mitigate the environmental impact of pavements. Diamond grinding, grooving, and next generation concrete surfacing (NGCS) are all ways to provide the most value to taxpayers while increasing safety, sustainability and more. Diamond Grinding Conventional diamond grinding often is used to create the smoothest and safest pavements available today. It is appropriate for new construction and existing pavement repairs and can be performed at any time during a pavement’s life. Diamond grinding removes a thin layer of the hardened concrete surface using a self-propelled machine outfitted with a series of closely spaced diamond saw blades mounted on a rotating shaft. Unlike diamond-impregnated carbide bits, which use impact to chip away the concrete surface, diamond grinding blades use abrasion to gently remove the surface layer without the risk of introducing microcracking of the aggregates. After diamond grinding, the pavement texture consists of grooves and lands, with the grooves laying beneath the pavement interface. Diamond grinding has been in use since the 1960s, with nearly 20 million square yards of pavement diamond ground each year in the United States alone. In addition to using diamond grinding to improve the performance of existing, in-service pavements, several state DOTs specify diamond ground surfaces as the final surface on newly placed portland cement concrete pavement (PCCP). The technique is also becoming more popular for cost effective remediation of ride quality in asphalt pavements. Diamond grinding and safety grooving are the clear solution to remediating the surface texture of new asphalt and concrete roadways as well as bridge decks. Not only is it one of the cheapest highway treatments available, it’s likely the only treatment that is often cost and carbon negative. The table above shows how diamond grinding can address the three goals (sustainability, comfort and safety) for each of the problems identified. Safety Grooving A road’s surface texture can be lost through tire wear and by the action of abrasives, tire chains, salt, freezing and thawing. With the loss of texture comes loss of friction between the pavement and vehicle tires. Vehicle accidents increase when there is a loss of friction between the tire and pavement surface and conditions become slippery. Highway departments have found the best way to decrease accidents during inclement weather is to remove water from the surface and increase the traction between the tire and the road. Safety grooving is a technique of surface saw cutting designed specifically to improve friction and reduce water ponding. Grooving a pavement’s surface increases traction, reduces hydroplaning, minimizes splash and spray, and provides a more-effective braking surface. Unlike diamond grinding, safety grooving is not attributed to an improved ride quality. Municipalities and departments of transportation find grooving is an easily constructed and economical surface treatment that increases driver safety in wet conditions and saves on the costs of replacing or overlaying the pavement surface. To groove a pavement surface, machines equipped with circular diamond-tipped saw blades are used to cut grooves into the surface. The blades are mounted and spaced on a horizontal shaft and are cooled constantly by water pumped from a tanker, which is recovered by an on-board vacuum system. These discrete channels can be constructed transversely or longitudinally into concrete and asphalt surfaces. Engineers typically specify grooves 1/8- to 3/16-inch deep and approximately 1/10- to 1/8-inch wide. The spacing is typically 3/4-inch center-to-center—which leaves too large of a landing area between blades to impact the surfaces profile—although random spacing of blades is used at times when grooving transversely to control tire/pavement noise. Safety grooving is less expensive than diamond grinding as it requires fewer diamond blades to perform, but it is the most-effective tool for mitigating hydroplaning. The Department of Civil Engineering at the National University of Singapore conducted a study to evaluate the impact of various grooving patterns on hydroplaning. A very in-depth evaluation of 132 different grooving patterns concluded that the speed a typical passenger vehicle could obtain before hydroplaning increases by about 2.8 kilometers per hour h for every mm increase of groove depth, by about 3.5 kilometers per hour for every mm increase of groove width and by about 1.0 kilometers per hour for every mm decrease of groove spacing. Research at NASA’s Langley Research Center concluded that safety grooving of runways had a significant impact on wet weather landing of aircraft as well. This research led to the standard acceptance of safety grooving of asphalt and concrete commercial runways around the world. In 1990, safety grooving was inducted into the NASA hall of fame. Case Study: California Measures the Success of Grooving As early as the 1970s, Caltrans evaluated the effect of safety grooving on 39 pavement sections. The results showed a 20% reduction in all accidents, a 50% reduction in fatal accidents and a 70% reduction in wet weather accidents. While the data also showed a 15% average increase in Skid Number (SN), the researchers gave primary credit of improved safety to the reduction of hydroplaning, not the improvement of friction. Additionally, the California Department of Transportation conducted a study of 322 lane-miles of longitudinally grooved concrete pavement and compared it to control sections of 750 miles of ungrooved concrete pavement. The study found grooving produced an overall average 69% decrease in accident rates for the highways studied in wet and dry conditions. Another study in California showed how roads wear over time, causing a decrease in friction and an increase in accidents. On Interstate 5 at Laguna Canyon Road near El Toro Marine Air Station, there were no wet weather accidents when the road was newly constructed using a burlap drag surface texture. As the road aged, eight wet weather accidents were recorded during the next year and 47 wet weather accidents in the year after. As the road was being used over time, the pavement was wearing, causing the friction values to drop. To correct the problem, the road was longitudinally grooved, using a specified 1/8-inch by 1/8-inch on 1/2-inch center pattern. Accidents for the following five years were reduced to a total of eight wet weather accidents. This study shows how grooving can increase wet weather traction, reduce hydroplaning potential and make the road a safer place for motorists. NGCS NGCS is the first new non-porous concrete texture to be introduced in the last 20 to 30 years. It took three years to research and develop, but less than one year to construct field test sections. NGCS is the smoothest and most quiet pavement surface treatment available. In an effort to create a quieter concrete pavement surface, Purdue University conducted research to develop a machined surface texture that would offer superior noise characteristics. NGCS consists of a three-step process. If the pavement has localized roughness, it should be removed using a bump grind with a conventional diamond grinding head. The goal of this step is to have no significant bumps or faults and to have an average IRI at or below 80 inches per mile. Production grinding using an NGCS grinding head to remove approximately 1/8 inch of surface material over 100% of the surface area of the project. A NGCS head is a diamond grinding head that has a tighter spacing between saw blades than a traditional diamond grinding head. This tight spacing will result in the removal of positive or upward texture typically left between saw blades, offering a very quiet riding surface. The IRI after this step typically is at or below 45 inches per mile. Safety groove the surface. The safety grooving also adds the benefits of improved macro texture for friction and improved drainage to prevent hydroplaning. The NGCS was conceived as a “manufactured surface” which would result in consistent and predictable properties at the time of construction and throughout its life. The preceding photo shows typical onboard sound intensity levels associated with the various textures, and the NGCS surface has met the low noise goals and demonstrated the lowest variability in as-constructed results to date. With the improved lateral stability and hydroplaning resistance afforded by the NGCS texture, there are additional benefits than just noise reduction. As demonstrated by both quiet pavement research efforts, NGCS surfaces also produced the smoothest pavements of any texture evaluated. NGCS is the most superior texture available for new and existing concrete pavements, combining all of the forementioned benefits offered by saw cut surface textures. Friction testing of the surfaces for over a decade has indicated a stable surface with a good frictional resistance. Initial concerns that the flush grind process would produce a low friction surface were not accurate. The grooving used in the NGCS provides similar ribbed and smooth tire test results and enhances hydroplaning resistance. Today, 14 states have constructed NGCS surfaces and two major state quiet pavement research efforts have evaluated this texture. Millions of square yards of NGCS have been constructed across the globe with positive results. Slurry Disposal Concrete grinding residue (CGR) is an inert, non-hazardous byproduct of the diamond grinding process. When diamond grinding concrete highways, water used to cool cutting blades combines with hardened cement paste and aggregate particulates to generate CGR, also known as slurry. The slurry is similar to a weak agricultural lime. Many states do not have the benefit of clear, localized guidance on disposal methods for CGR. This leads to a situation in which CGR disposal is potentially posing unnecessary costs for projects—and leaves the beneficial effects of slurry underutilized. Often, states limit how much slurry can be discharged along the roadside during the diamond grinding process. But hauling slurry off-site for processing and disposal is costly for DOTs and for taxpayers. The elimination of unnecessary regulations in areas with site conditions that allow for the discharge of CGR directly to the road’s shoulder would benefit roadway owners and taxpayers by reducing construction costs. To determine the real impact of slurry on roadside soil and vegetation, multiple studies have been performed. They all have found slurry to be safe. For more information, see the IGGA white paper, “Studies Show Slurry Roadside Disposal is Safe.” In accordance with research showing a lack of negative environmental effects from slurry disposal along roadways, states are changing regulations. For example, Minnesota recently enacted legislation redefining their solid waste definition throughout the state, exempting concrete saw-cut slurry from the solid waste classification and allowing slurry to be spread along adjacent slopes. This was done in part because there was no evidence showing slurry constituted a threat to the environment. In the above linked resource, IGGA developed best management practices for CGR disposal to help slurry byproduct continue to be handled in a professional, environmentally responsible way. When following the best management practices, studies show slurry is not harmful to soil or plant life and can even be beneficial as a soil additive. Bibliography IGGA. Diamond Saw Cut Textures: Improving Pavement Performance and Customer Satisfaction, November 2020, Dare, Tyler; Thornton, William; Wulf, Tanya; Bernhard, Dr. Robert. “Acoustical Effects of Grinding and Grooving on Portland Cement Concrete Pavements;” Purdue University’s Institute for Safe, Quiet, and Durable Highways and the American Concrete Paving Association, U.S. Department of Transportation Federal Highway Administration. Highway Traffic Noise, IGGA. Diamond Grooved Surfaces Reduce Dynamic Hydroplaning, October 2014, Ong, G. P. and Fwa, T. F. “Analysis of Effectiveness of Longitudinal Grooving Against Hydroplaning,” Dept. of Civil Engineering, National University of Singapore, November 2005, Drakopoulos, Aris; Wenzel, Thomas H.; Shober, Stephen H.; and Schmiedlin, Robert B. “Crash Experience on Tined and Continuously Ground Portland Cement Concrete Pavements,” Transportation Research Record 1639, Paper No. 98-0467, Swanlund, Mark. “Enhancing Pavement Smoothness,” U.S. Department of Transportation Federal Highway Administration. Public Roads - Sept/Oct 2000, Louhghalam, Arghavan; Akbarian, Mehdi; Ulm, Franz-Josef. “Carbon management of infrastructure performance: Integrated big data analytics and pavement-vehicle-interactions,” Journal of Cleaner Production, Volume 142, Part 2, 20 January 2017, Pages 956-964. 2013 Status of the Nation’s Highways, Bridges, and Transit: Conditions & Performance. U.S. Department of Transportation Federal Highway Administration. Burningham, Sally and Stankevich, Natalya. “Why road maintenance is important and how to get it done,” The World Bank, Washington, D.C., Transport Note No. TRN-4 June 2005, documents1. Steyn, W J vd M; Monismith, C L; Nokes, W A; Harvey, J T; Holland, T J; and Burmas, N. “Challenges confronting road freight transport and the use of vehicle-pavement interaction analysis in addressing these challenges,” Journal of the South African Institution of Civil Engineering, ISSN 2309-8775, J. S. Afr. Inst. Civ. Eng. vol.54 n.1 Midrand Apr. 2012, Vinayakamurthy, Mounica; Mamlouk, Michael, Ph.D., P.E.; Underwood, Shane, Ph.D.; and Kaloush, Kamil, Ph.D., P.E. of Arizona State University. “Effect of Pavement Condition on Accident Rate,” University of Maryland National Transportation Center, Project ID: NTC2016-SU-R-2, World Health Organization. Compendium of WHO and other UN guidance on health and environment, Soundproof Guide. What is Acceptable Noise Levels in Residential Areas? CDC. What Noises Cause Hearing Loss? November 2022, Chen, Dar-Hao and Hong, Feng. “Long-Term Performance of Diamond Grinding,” Journal of Performance of Constructed Facilities, Vol. 29, No. 1, Jan. 10, 2014, Murray, B.D. “The Effect of Pavement Grooving on Skid Resistance,” California Department of Transportation, Report No. CA-TL-78-19, June 1978, Byrdsong, Thomas A. and Yager, Thomas J. “Some Effects of Grooved Runway Configurations on Aircraft Tire Breaking Traction Under Flooded Runway Conditions,” NASA, TN-D7215, April 1973, Scofield, Larry. “Development and Deployment of the Next Generation Concrete Surface,” CP Road Map, Map Brief January 2020, AzariJafari, Hessam; Guo, Fengdi; Gregory, Jeremy; and Kirchain, Randolph. “Carbon uptake of concrete in the US pavement network,” Resources, Conservation and Recycling, Volume 167, April 2021, 105397,,used%20for%20streets%20and%20highways. IGGA. Conserving Fuel When Rehabilitating Concrete Roads, September 2014, IGGA. Long-Lived Concrete Pavement: TH 210 in Minn. Achieves a 69-Year Service Life—With More Years to Come, March 2023, IGGA. California State Route 85 Tested for Quietest Pavement: Diamond Grinding was the Solution, January 2010, IGGA. Kentucky Uses Pavement Management Systems to Reduce Costs and Improve Pavement Smoothness, ACPA and IGGA. Development and Implementation of the Next Generation Concrete Surface, 2017, IGGA. Carbonation: Quantifying a Sustainability Benefit of Concrete Pavement, June 2022, IGGA. Studies Show Slurry Roadside Disposal Is Safe, White Paper, 2022, Coalition for Responsible Roads. IGGA. Bipartisan Infrastructure Law Series, Aligning your Department’s Priorities with BIL Funding Priorities, May Spotlight: Carbon Capture, May 2023, IGGA. Bipartisan Infrastructure Law Series, Aligning your Department’s Priorities with BIL Funding Priorities, August Spotlight: Albedo, August 2023, IGGA. Bipartisan Infrastructure Law Series, Aligning your Department’s Priorities with BIL Funding Priorities, July Spotlight: Pavement Grooving, July 2023,

  • 2023 IGGA Annual Meeting

    The IGGA Annual Meeting will take place in Marco Island, Florida, at the JW Marriott Marco Island Beach Resort from 8:00 AM - 3:00 PM Tuesday, December 12, 2023. A reception will take place on site at the Maia Restaurant from 4:30 PM – 6:30 PM.

  • Runway Grooving: A Good Solution Takes Off

    Grooving airport runways is common practice in the United States. The U.S. Federal Aviation Administration (FAA) recommends grooving for all airport projects funded with federal grants, which represents most projects. Similarly, U.S. Department of Defense facilities are increasingly specifying new, reconstructed or resurfaced runways to be grooved. In Canada, however, there has been limited use of runway grooving. In recent years this situation has been changing, due to the overwhelming evidence that grooving is a proven strategy for reducing the risk of hydroplaning and improving runway safety. Read more of this article in the April 2019 issue of Airport Business.

  • ODOT Uses Longitudinal Grooving for Safety on Asphalt as well as Concrete Pavements

    Diamond grooving on three Ohio highways significantly reduced wet-weather accident rates. ODOT has specified longitudinal diamond grooving -- which helps reduce hydroplaning risks, increases drainage at the tire/pavement interface, and aids in vehicle control -- on concrete bridge decks since 2012. However, most of Ohio's state roadways are not concrete; they are asphalt or composite pavement. The superior safety performance of grooving on bridge decks encouraged the department to use the technique on several sections of asphalt pavement, all located on high-speed roadways and tight curves where wet weather safety was a concern. Read more about ODOT's use of longitudinal grooving on asphalt pavements.

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