Effects of concrete grinding residue (CGR) on selected sandy loam properties

Concrete Grinding Residue (CGR) is a slurry waste generated from diamond grinding of fresh concrete pavement surfaces. Fresh CGRs are mostly disposed along the roadside which can impact the chemistry of soils and vegetation growth along the roadways. To understand the effects of CGR on soil chemical properties, sixteen controlled experimental plots (2-m by 2-m for each) classified as sandy loam or clayey sand were established and applied with four different CGR rates: 0, 2.24, 4.48, and 8.96 kg m−2. Soil samples were collected at various times, one month, six months, and twelve months, after CGR application to measure pH, electrical conductivity (EC), alkalinity, metal concentration, water-extracted cation exchange capacity (WE-CEC), exchangeable sodium percentage (ESP), and percentage base saturation (PBS). The results of statistical analyses indicated that the CGR applications impacted the chemical properties of soil, and the impact of CGR became greater with an increase in the CGR application rate. In addition, the CGR impact decreased with soil depth. For the CGR application rate of 8.96 kg m−2, soil pH, alkalinity, EC, WE-CEC and ESP increased by 24%, 392%, 219%, 219% and 106%, respectively, while PBS decreased by 16%. CGR also increased concentrations of Ca, K, Mg, Na, Al, and Fe in soil by at least 50%. However, the changes in soil properties such as pH and PBS did not persist twelve months after the CGR applications. The primary findings indicate that, although CGR can change some soil chemical properties significantly, changes may not have long term negative impacts on the soil and plant environment.