Abstract
Gypseous soils are capable of presenting ground construction challenges to civil and geotechnical engineers due to their unpredictable deformation characteristics. These undesirable responses are sometimes caused by environmental changes in moisture content due to temperature variations, fluctuation of underground water table, surface water, and gypsum content. Hence, the adoption of effective and economical means of stabilising gypseous soils is imperative. This study’s focus is on the early age strength and microstructural characteristics of gypseous soils treated with lime and GGBS. Treated and untreated gypseous soils with 5%, 15%, and 25% gypsum content were subjected to wet–dry cycles while investigating unconfined compressive strength (UCS), water absorption, pH, microstructural changes, and swell. The analysis of the results shows that at zero cycle, the UCS of the untreated gypseous soils increases from 0.62 to 0.79 MPa and swell decreases from 69 to 23%, respectively, as gypsum content increases. However, upon subjection to wet–dry cycles, the UCS reduced from 0.16 to 0.08 MPa at the end of the sixth cycle due to dissolution of gypsum within the soil pores which reduced the strength. The result also shows that gypsum content increases water absorption and reduces the pH of the untreated gypseous soils because of the neutral pH of gypsum. Furthermore, lime-GGBS-treated gypseous soils maintained a higher pH after six wet–dry cycles compared to untreated gypseous soils due to the high pH of lime and the increase in calcium content which improved bonding. In addition, microstructural analysis using SEM indicated early age precipitation of cementitious compounds (CSH) for increasing strength of lime-GGBS-treated gypseous soils compared to untreated gypseous soils.
Highlights
Calcium-based additives such as cement, and lime have been widely used in improving many problematic ground conditions the world over
The study by [22] investigated the application of carbide slag-activated ground granulated blast furnace slag (GGBS) on the engineering characteristics of gypseous soil, and found that the initial formation of ettringite and synthesis of geopolymeric chains reduced the Ca(OH)2 concentration. This resulted to a reduction in further formation of ettringite development within the matrix of the treated gypseous soils thereby leading to a decrease in swell potential when compared to treatment with ordinary Portland cement (OPC)
To conduct a precise laboratory study, representative samples of soil 1 were mixed with 5%, 15% and 25% of gypsum by weight of dry soil, and hereafter referred to as gypseous soils with varying gypsum contents
Summary
Calcium-based additives such as cement, and lime have been widely used in improving many problematic ground conditions the world over. The study by [22] investigated the application of carbide slag-activated GGBS on the engineering characteristics of gypseous soil, and found that the initial formation of ettringite and synthesis of geopolymeric chains reduced the Ca(OH) concentration. This resulted to a reduction in further formation of ettringite development within the matrix of the treated gypseous soils thereby leading to a decrease in swell potential when compared to treatment with OPC. The early age wet and dry cycles of lime and GGBS-treated gypseous soils was studied in other to evaluate the performance of treated gypseous soils under changing environmental conditions characterised by changing moisture contents
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