Experimental Study on Early Age Characteristics of Lime-GGBS-Treated Gypseous Clays under Wet–Dry Cycles

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.

Behaviour and Microstructural Characteristics of Lime-GGBS-Treated Kaolin Clay Contaminated with Gypsum

“…The reduction in the UCS of the untreated gypseous soil might be attributed to increased sulphate contents in the absence of additional strength-yielding compounds at OMC, which lowered the UCS of the untreated gypseous soils and has been reported in [ 27 ]. Strength gain is mainly due to cementation from calcium-silica-hydrate and calcium-aluminate-hydrate reactions initiated in the soil-binder medium at higher pH, as reported by [ 48 , 72 , 73 ], which was not the case with the untreated gypseous soils at higher gypsum contents.…”

“…This characteristic aligns well with the swell curves shown earlier. Earlier research work [ 27 , 48 ] have highlighted the fact that more gypsum, above a critical percentage, led to increased cementation and resulted in lower water absorption and expansion. Furthermore, for the treated samples, SEM and EDX results at 28-days curing, as seen in Figure 13 and Figure 14 , show more binder flakes and crystals synonymous with long-term curing.…”

“…The materials used in this experimental work include kaolin(K), gypsum (GYP), lime(L), and ground granulated blast furnace slag (GGBS). Gypsum (CaSO 4 ⋅2H 2 O), a product of the reaction of calcium carbonates and sulphuric acid (H 2 SO 4 ), can be used to constitute sulphate-bearing soils in the laboratory [ 29 , 33 , 48 ]. The OPC used in this study is CEM1.…”

“…The OPC used in this study is CEM1. The gypsum, lime, and GGBS used in this study have been used in a previous study [ 48 ], with the lime in conformity with [ 49 ]. The chemical compositions of the materials are given in Table 1 below.…”

Performance of Sustainable Road Pavements Founded on Clay Subgrades Treated with Eco-Friendly Cementitious Materials

“…Carbon reduction in pavement construction was observed when recycled plastic (RP) waste was used at varying proportions to enhance the engineering properties for eco-friendly pavement application [8]. Road pavements are superimposed layers of materials placed over the natural ground [9,10]. Development of stresses within road pavement caused by traffic load and geotechnical issues lead to damage to the road pavement [11].…”