Comparing the Effects of two alkaline activators of Sodium Hydroxide and Calcium Carbide Residue on geopolymeric stabilization of clay soils

Nowadays, the ordinary Portland cement (OPC) industry causes to extensive environmental consequences due to consuming huge amounts of fossil fuels. This necessitated researchers to introduce a novel group of binders called “Geopolymer cements” or “Green cements” with higher performance and lower pollution compared to the OPC. Thus, in this research, the effect of using two types of alkaline activators such as sodium hydroxide (NaOH) and calcium carbide residue (CCR), for stabilization of clay soil (CL) has been investigated. Initially, the chemical compositions of soil, recycled glass powder, calcium carbide residue, and sodium hydroxide were obtained via X-ray fluorescence (XRF) test. Then, the mechanical behavior of different unstabilized, geopolymer-stabilized, and OPC-stabilized samples has studied using unconfined compressive strength (UCS) test. The effects of several parameters such as the type and concentration of alkaline activators, the curing times (7, 28, and 91 days), and the initial synthesis temperature (25 and 70 ˚C) on the UCS and failure strain of samples have been assessed. Moreover, in order to studying the microstructure of samples, the scanning electron microscope (SEM) images and energy dispersive X-ray (EDX) analysis of selected samples have been used. Results showed the effective stabilization of soil geopolymer, using both alkaline activators. However, the CCR will be more appropriate if environmental and economic problems considered.