Experimental Investigation of the Engineering and Leaching Properties of Alkali-Activated Geopolymer Soil

Geopolymer, a sustainable alternative to conventional binders, ultimately assists to control environmental pollution, reduces human health risks, and provides economic benefits. This study examined the mechanical, serviceability, and leaching characteristics of alkali-activated soil incorporating industrial by-products for potential use as road base, backfill, and/or clay liner material. The combined use of both NaOH and Na2SiO3 as alkali activators showed superior strength and durability, outperforming those activated solely with NaOH. The optimal unconfined compressive strength (UCS) values of 12.08 and 2.72 N/mm2 in the dry and saturated state, respectively, were found at 8 molar (M) NaOH and Na2SiO3 with 55% soil replacement. The calcium (Ca) content of ground granulated blast furnace slag (GGBS), which demonstrated greater reactivity during water curing compared to ambient curing, played a key role regarding strength and durability. Performance reliability was evaluated through a weather resistance test, which confirmed a maximum weight loss of 6.80% after seven wet-dry cycles and 5.67% after 28 days of acid immersion, compared to the initial weight. The leaching potential of the composite sample was under the permissible limit in deionized water but exceeded it in weak and strong acids. The cross-linked integrated morphology identified in field emission scanning electron microscopy (FESEM) images with the reduced peak accompanied by new minerals in x-ray diffraction (XRD) analysis of the composite compared to the raw materials indicated the polymer reaction.