Cost-Effective Use of Sustainable Cementitious Materials as Reactive Filter Media (Phase I)

Abstract

This report presents a laboratory study on the use of nano SiO2 as modifier in crushed fines recycled concrete (CFRCs), coupled with thermal treatment, with the goal of fabricating a sustainable reactive medium to capture the chloride anions in deicer-laden stormwater runoff. A uniform design (UD) scheme was employed for the statistical design of experiments. Predictive models were developed based on the experimental data to quantify the influence of each design parameter on the effectiveness of removing Cl- ions from simulated stormwater. The models were verified, and then employed for predictions. Finally, the samples of different CFRCs modified by nano SiO2 and heating regimes were prepared under the optimal parameters identified via the Response Surface Methodology (RSM). The optimal processing of CRFCs include the use of admixing nano SiO2 at 0.3% (by mass), then heating the material at 525oC for 3h. The structure and properties of these CFRCs materials were characterized by XRD, FTIR, BET, SEM and EDS. These advanced characterization tools revealed that the modified CFRCs achieved great potential to chemically bind chloride anions. This work is expected to produce substantial benefits for highway agencies and other stakeholders of deicer stormwater runoff, through enhanced understanding of the efficacy and appropriateness of cementitious filter media in passive reactive systems for decreasing contaminant loading in stormwater runoff. The use of CRFCs as a low-cost sorbent will be economically attractive and environmentally sustainable, diverting them from waste stream and landfill and towards sustainable stormwater management.