Iowa Department of Transportation
Iowa Highway Research Board
Recycled Materials Research Center (RMRC)
University of Wisconsin-Madison
About the research
Diamond grinding is a widely-used rehabilitation technique usually referred to as resurfacing of Portland cement concrete (PCC) pavement. As a maintenance operation, diamond grinding can provide a smooth PCC surface with enhanced texture and skid resistance and reduced road noise. Typically, this operation uses a truck equipped with grinding heads at ground level to saw a thin layer of concrete, grinding it into fine particles, while mixing with water to cool blades and reduce dust. This process generates a slurry byproduct known as concrete grinding residue (CGR).
The majority of current maintenance practice involves spreading of fresh CGR on roadsides, resulting in potential environmental concerns regarding vegetation growth. This becomes a more critical issue when disposal of CGR slurries are adjacent to sensitive areas such as farmlands, water bodies, and high groundwater table presence. CGR disposal may lead to reduced density of vegetation, which may lead to increased erosive risks.
The composition of CGR can vary widely due to use of different Portland cement products and admixtures materials in concrete. Generally, CGR is characterized as having a high pH and is rich in metal content (e.g., chromium [Cr] and iron [Fe]) due to the addition of fly ash and/or steel slag during cement production or concrete mix preparation. Thus, the inappropriate disposal of CGR may cause critical environmental issues at sensitive nearby areas. On the other hand, CGR has a significant potential for reuse as construction material, liming products, or soil stabilizer due to its high pH and rich calcium oxide (CaO) content.
A summary based upon a comprehensive literature review conducted during Phase I of this project shows that CGR may pose some environmental concerns even though in some cases it seems to be environmentally friendly. In the Phase I study, a state-of-the-practice survey of regulations governing CGR management practices in all 50 US states was conducted to understand issues and concerns regarding CGR use in the concrete industry and state highway agencies (SHAs). In considering the properties of CGR, recycling of slurry waste in soil, concrete, and other applications could be an attractive alternative for ultimately improving roadway sustainability, long-term performance, and reducing life-cycle cost of pavement designs.
For this purpose, the second phase of research is proposed to evaluate the possibilities for reuse of CGR in several applications. In particular, this study will highlight CGR recycling opportunities for soil stabilization and erosion mitigation suggested by laboratory tests including: unconfined compressive strength (UCS), surface runoff tests, Atterberg limits, alkalinity, EC, pH, and leaching tests.