Hydration Characteristics And Leaching Behavior of Different Mixes Of Slag Based - Geopolymer Cement In Presence Of Heavy Metals

Abstract

Geopolymer binders are now considered to be a necessary condition for replacing Portland cement (OPC) to improve environmental and durability efficiency. Heavy metal contamination has become a very dangerous environmental issue that is becoming increasingly over time. The purpose of this work is to examine the effect of some heavy metals on the hydration characteristic of different mixes of slag-based geopolymer pastes containing some waste materials such as fly ash (FA) and cement kiln dust (CKD), and also, to study the stabilization of heavy metals on the geopolymer matrix to measure the possibility of using this method to remove it. Geopolymer synthesis by 100% slag and partial substitution of slag by 15% FA (85% slag+15%FA) and 5% CKD replacement (95% slag+5% CKD) were investigated. The mixture of liquid sodium silicate (Na2SiO3) and sodium hydroxide (5M NaOH) with a ratio (1:1) is used as an alkaline activator solution. Various percentages of copper ions (Cu2+) or cadmium ions (Cd2+) are added to the alkali -activated mixes. The results indicated that best mix for immobilization of Cu2+ is 100 %slag + 0.5%CuCl2 and for Cd2+ were in case of 100% slag + 0.5%CdCl2 and 95% slag + 5% CKD +0.5%CdCl2. . Our study results support the use of different prepared geopolymer pastes in heavy metals solidification /stabilization up to 90 days.