What to Do With Slurry From Cutting Concrete?

Dumping on Job Site

• Dumping concrete slurry involves collecting the residue created from cutting concrete into a plastic bin and unloading it at a concrete ready-mix plant. This option was the most popular until revisions were recently made to the Clean Water Act of 1987. The revisions were made because concrete slurry was leaving the job site, creating pollution in nearby water supplies. This option was the cheapest and most beneficial to the contractor because they didn’t have to pay for disposal of the slurry. Today, there are limited numbers of landfills that accept concrete slurry, making it more expensive to dispose of it in this manner.

Settling Ponds

• Contractors dispose of concrete slurry into settling ponds constructed at ready-mix facilities. Wash water from the concrete trucks is collected in settling pits. The material settles in the pit, with the heaviest material sinking to the bottom. The water that is on top is clearer once the aggregate settles to the bottom and is either reused to wash concrete trucks or pumped to a retention pond.

Chemical Stabilizing Systems

• An alternative solution to the traditional concrete slurry disposal methods, admixtures used in concrete mixes actually put the concrete in a dormant state and temporarily stop the hydration process. The amount of admixture used in various concrete mixtures depends on the amount of wastewater present and the amount of time desired to reuse the wastewater. Because the hydration of the cement is delayed, the wash water does not harden and it does not stick to the concrete drums on the trucks. The water left in the concrete drum can then be used in the next concrete mixture. This is a very costly process but is the most environmentally friendly.

Reclaiming

• Some contractors use the wastewater from concrete cutting for washout purposes or for producing fresh concrete. They simply use the wastewater in concrete mixtures for concrete in areas that do not carry a massive amount of traffic. The major disadvantage to this method is lack of knowledge. Researchers are still not sure what effects the wastewater has on the stability and longevity of concrete as it alters the properties of concrete.