Carbon capture potential and environmental impact of concrete weathering in soil.

The enhanced weathering of concrete in soil has potential to capture atmospheric CO. The objective of this research was to conduct a laboratory experiment and evaluate the environmental impacts and carbon capture potential of concrete as an enhanced weathering material in soil. A column study was conducted with four treatments comprised of: 1) 100 % soil (S treatment), 2) 90 % soil and 10 % concrete by weight of 0.25-0.71 mm diameter fragments (S + C treatment), 3) 90 % soil and 10 % concrete by weight of 8-25 mm diameter fragments (S + C treatment), and 4) 100 % concrete composed of 8-25 mm diameter fragments (C treatment). Deionized water was added to the columns for 16 weeks. The S + C treatment experienced a significant increase in soil pH (8.0 ± 0.07) compared to the S (6.9 ± 0.22) and S + C (7.1 ± 0.08) treatments. The C treatment experienced a significant increase in leachate pH. Leachate NO concentrations in the S + C (33 ± 18 mg L) samples were significantly greater than those in other treatments. Soil microbial community concentrations were significantly less in the S + C treatment. The S + C treatment had a calculated average HCO concentration of 350 ± 120 mg L which was significantly greater than the S (230 ± 100 mg L), C (270 ± 170 mg L), and S + C (260 ± 50 mg L) treatments. Increased concentrations of Ca, SO, HSiO and HCO in the mixed concrete and soil samples are evidence that chemical reactions occurred due to the soil-concrete interaction and are likely capturing atmospheric CO.