Design of a chitosan modifying alkali-activated slag pervious concrete with the function of water purification

Abstract

A kind of alkali-activated slag pervious concrete (AAS-PC) was designed to purify rainwater to prevent it from polluting groundwater resources. The pervious concrete was designed from two aspects: the cementitious material and the volumetric structure parameters of pervious concrete. Chitosan was used in the cementitious material paste to enhance the adsorption capacity for heavy metal ions and other pollutants. In consideration of adsorption, composition parameters of the cementitious material paste such as the chitosan content, the mole ratio of SiO2/Na2O, and the concentration of alkali activator wereoptimized by orthogonal experiment. The influences of the bulk porosity of aggregate (BPA) and the ratio of paste to aggregate (P/A, mass ratio) on water purification capability, water permeability, and mechanical properties of the AAS-PC were investigated. It is found that, with the BPA increasing, the adsorption to Pb2+ and the compressive strength of pervious concrete decreased gradually but its water permeability improved; meanwhile, with the P/A increasing, its adsorption to Pb2+ and the compressive strength increased, but its water permeability decreased. There is a negative correlation between the water purification and the water permeability of the pervious concrete. Considering the water purification, water permeability and strength properties of the pervious concrete, the optimum BPA was 30% and the optimum P/A was 0.25.