Avoid These Common Mistakes Before Grinding the Bridge Surface

Control deck grades to accommodate equipment and avoid joint damage

Increasingly, owners are specifying diamond grinding to improve the ride quality, friction and drainage capabilities of new bridge deck surfaces. Historically, bridges have suffered from ride quality issues where adjoining bridge deck segments and approach slabs meet one another. To counter this issue, agencies are now specifying that the final riding surface be diamond ground.

Diamond grinding provides a much smoother riding surface and reduced dynamic loading, while providing greater driver satisfaction. The diamond-ground surface also contributes to reduced tire/pavement noise, benefitting those who live in adjoining neighborhoods.

The introduction of diamond-ground surfaces on bridge decks has created some challenges, however, that can be easily overcome following a few simple tips as outlined below. Specifications for diamond grinding bridge decks generally require grinding in the longitudinal direction over the entire length of the bridge and over the full deck width, extending to within two feet of the parapets. The grinding depth required is usually a nominal ¼ inch and continuous across all joints.

Clearly, it is imperative that expansion joints and bridge components under the joints be protected from damage lest the contractor be subject to financial penalties and repair costs. To accomplish this, contractors should follow these simple tips:

• Ensure tight line and grade controls when paving. Diamond grinding machines have long wheelbases and need to transition slowly into grade changes. Whenever possible, grades should be consistent on both sides of the joint and on the approaches to the joints. Uneven deck surfaces will inevitably result in an inconsistent and spotty diamond-ground surface. 

  
  

• Add additional concrete thickness during the paving process to account for the sacrificial concrete removal during the grinding process. The amount of additional section thickness should be based on the paver’s confidence that a smooth deck can be achieved. As the paving challenges increase, so should the sacrificial concrete thickness. A ¼ inch sacrificial layer may not be enough. 

  
  

• Check your steel. Steel set improperly or at the incorrect elevation will cause problems during the grinding process. Well-placed steel and expansion joints, set below the sacrificial concrete layer, allow for a consistent depth of cut, permitting the diamond grinding machine’s grinding head to clear each expansion joint without causing damage. 

• Control your slump. Inconsistent slump during the paving process can lead to low spots on the deck surface, making it difficult for the grinder operator to meet specifications. Decks that require significant adjustments in cut depth leading up to a transition or expansion joint should be avoided.

  
  

• Slow down. Advancing the paver too quickly will often lead to increased roughness and will increase the risk of joint damage and low spots while grinding. The money saved shaving off an hour of labor costs will pale in comparison to a $100,000 expansion joint replacement if it is damaged by a grinder.

  
  

• Know your deck. It is important to be aware of the problems that can occur when deck grades are not well controlled. Issues such as low spots and high steel should be identified and related to the grinder operator before grinding commences. Ideally these issues will have been prevented before the paving process, as described above.

  
  

• Walk-behind and short wheel base grinders should not be used. Ride quality, drainage and aesthetics are degraded by such devices. 

By following these simple steps, contractors can reduce the risk of damage to vital bridge components—as well as avoid penalties—while providing the driving public with smooth, safe and quiet bridge deck riding surfaces.

Reach out today at https://www.igga.net/contact-usto learn more.