Swell and microstructural characteristics of high-plasticity clay blended with cement

Abstract

This study presents the effect of high plasticity on swell potential, swelling pressure and micro-structural characteristics of kaolinite-bentonite mixed clays. Five different mix ratios of kaolinite bentonite mixture of 100:0, 90:10, 75:25, 50:50 and 25:75 in % by weight of dry kaolinite were used. All five synthesised soils were then mixed with 0%, 5% and 8% of cement by weight of dry soil, cured for 28 days and subjected to the Atterberg limit, one-dimensional oedometer and scanning electron microscope test. The inclusion of 5% and 8% cement reduces the plasticity index of the treated soils as the percentage of bentonite increases. The effects on plasticity of treatment with 5% and 8% cement after a 28-day curing period was evaluated, and the results show that reduction in plasticity index resulted in decreased swell potential and swelling pressure of the kaolinitebentonite mixed clays. The results of microstructural analysis of 5% cement-treated soils show formation of flocculated fabric and cementation of soil particles, and filling with cementitious compounds of the voids of flocculated fabric in the soil. The reduction in swell can be attributed to the resulting compacted and dense mass of treated soils due to cementation of soil particles and cation exchange. The complex swell behaviour of high-plasticity kaolinite-bentonite mix is explained using the onedimensional oedometer test, by further experimental study and examination of the microstructure of treated soils.

Hydraulic and Swell–Shrink Characteristics of Clay and Recycled Zeolite Mixtures for Liner Construction in Sustainable Waste Landfill

“…The analyses of shrinkage characteristics of the studied light-textured clay-NaP1 zeolite mixtures showed agreement with literature reports suggesting that addition of fine particle zeolites to the natural clay specimens increases their expansiveness [55,56]. The contrary effect, the significant stabilization of clay soils by zeolite amendment, reported by [57][58][59][60][61] was not observed. The slight decrease of shrinkage potential value represented by COLE and shrinkage potential (Figures 8 and 9, respectively) was observed for clayzeolite mixtures based on specimens sampled in Jelen (clay loam), Lazek (silty clay), and Pawlow (clay loam).…”

“…Thus, different zeolite admixture in variable dozes to various types of soil may result in diversified influence on the resultant hydraulic properties of soils, including their hydraulic conductivity. Moreover, it should also be clearly underlined that, according to several sources [55,56], mixtures of expansive clayey soils with different dozes of various zeolites may present higher expansiveness than the original specimens, which is in contrast to reports describing reduction in swelling characteristics due to dispersive clays stabilization by fine particle materials e.g., cement, fly ash, or stone dust [57,58] or some natural zeolites [51,[59][60][61].…”

Appropriate Use of Lime in the Study of the Physicochemical Behaviour of Stabilised Lateritic Soil under Continuous Water Ingress

“…Extensive laboratory investigations have been carried out to evaluate the effect of traditional stabilisers, such as lime and cement, on the mechanical performance of lateritic soils and other residual soils [23][24][25][26][27][28][29][30][31][32]. The addition of quicklime (CaO) to lateritic soils or clayey soil in the presence of water, leads to a hydration (exothermic) reaction that produces hydrated lime Ca(OH) 2 .…”

Microstructure and Physical-Mechanical Characteristics of Treated Kaolin-Bentonite Mixture for Application in Compacted Liner Systems

“…Most researchers have focused on the use of relatively less proportions of bentonite (ranging from 2% to 20%), but it is pertinent to note that higher proportions have also been reported in literature [28,29]; hence, this study intends to experiment on expansive clays with proportions of sodium bentonite of up to 75% by weight of the entire soil mass. Since sodium bentonite is essentially composed of a high percentage of aluminates and silicates but a very low amount of calcium, 8% of cement was utilized to stabilise the soils based on established practices, and in order to prevent subsequent drying upon compaction [6,30]. Compared to the highest amount of the bentonite used for initial stabilisation of the mixture, this quantity of cement could be considered as being minimal.…”

“…Since natural sodium bentonite deposits are rarely found in abundance in some parts of the globe, clays containing kaolinite mineral (chemically weathered feldspar) of relatively lower swelling capacity are also sometimes used as sealants to contain wastes. Still, a mixture of bentonite with kaolinite and or without sand in different proportions have been used in the past as a probable compromise to satisfy cost and performance [3][4][5][6].…”