Mechanical Strength of Saline Sandy Soils Stabilized with Alkali-Activated Cements

Abstract

Saline soils usually cannot satisfy the requirements of engineering projects because of their inappropriate geotechnical properties. For this reason, they have always been known as one of the problematic soils worldwide. Moreover, the lack of access to normal water has intensified the use of saline water resources such as seawater in many construction and mining projects. Although cement stabilization is frequently used to improve the engineering properties of saline soils, Portland cement’s usage as a binder is constrained by its negative consequences, particularly on the environment. In this line, the effects of NaCl on the microstructural and mechanical properties of alkali-activated volcanic ash/slag-stabilized sandy soil were investigated in this study. Moreover, the effects of binder type, slag replacement, curing time, curing condition, and NaCl content on the mechanical strength of stabilized soils were examined. In addition, microstructural analyses, including XRD, FTIR, and SEM–EDS mapping tests, were performed to understand the physical and chemical interaction of chloride ions and alkali-activated cements. The results show that alkali-activated slag can be a sustainable alternative to Portland cement for soil stabilization projects in saline environments. The increase in sodium chloride (NaCl) content up to 1 wt.% caused the strength development up to 244% in specimens with 50 and 100 wt.% slag, and adding more NaCl had no significant effect on the strength in all curing conditions. Microstructural investigations showed that the replacement of volcanic ash with slag resulted in the formation of C-S-H and C-A-S-H gels that reduced the porosity of the samples and increased mechanical strength. Furthermore, surface adsorption and chemical encapsulation mechanisms co-occurred in stabilized soil samples containing slag and volcanic ash.

Effect of Seawater on the Mechanical Strength of Geopolymer/Cement Stabilized Sandy Soils

“…On the other hand, in a steam-curing environment, the steam kept the shrinkage process from drying up, preserving the samples' strength. The results of this study contributed to the potential of using seawater as well as sea sand in the manufacture of geopolymer concretes [2,[17][18][19].…”

Saline-Alkali Soil Property Improved by the Synergistic Effects of Priestia aryabhattai JL-5, Staphylococcus pseudoxylosus XW-4, Leymus chinensis and Soil Microbiota

“…The physical improvements of salinealkali soil mainly include land leveling, soil improvement in micro areas, soil loosening, alternate wet and dry cultivation and soil surface coverage [5,6]. The chemical improvements refer to the transformation, adsorption or fixation of saline-alkali components in the soil through the application of chemical modifiers and organic matter [7,8] to reduce the contents of saline-alkali components in the soil. For example, the cation exchange capacity of saline-alkali soil is improved by using corn straw biochar to increase the contents of organic matters and nutrients in the saline-alkali soils [9].…”

Use of Alkali-Activated Slag as an Environment-Friendly Agent for High-Performance Stabilized Soil

“…Some scholars have studied the properties of alkali-activated slag and fly ash [ 33 , 34 ]. Reza et al [ 35 ] studied the effects of NaCl on the microstructure and mechanical properties of stabilized sandy soil with alkali-lithium-activated ash slag and confirmed that the alkali-lithium-activated slag could replace Portland cement for soil stabilization engineering in saline-alkali environments. Hania et al [ 36 ] investigated the potential of alkali-active powdered blast furnace slag and volcanic ash as green binders in clay stabilization projects.…”