Characterization of Concrete Grinding Residue and Its Impact On Soils and Plants.

Grinding of concrete highway surfaces is widely used to improve ride and extend useful highway life.  The resultant concrete grinding slurry (CGR) can be disposed of below the road shoulder at the site of grinding, collected and moved to a containment pond where it is then dewatered and the solids are transported to a landfill, or recycled.  The direct disposal of CGR to roadside soils has become an environmental issue for some states.  The objectives of this study were to (i) characterize CGR from across the United States, (ii) determine the impacts of CGR on water infiltration into soil, and (iii) determine the impacts of CGR on soil and plant health.  Results indicate that CGR is fairly inert, but this byproduct does have a solution pH that ranges between 11.6 and 12.5.  The addition of CGR to soil generally decreased infiltration time, but when applied to soil at 25% by mass, generally decreased plant production.  The application of CGR to roadside soils saves time and money for the grinding industry, but care needs to be taken to not introduce CGR into sensitive areas such as wetlands, surface waters, and ground waters.