INVESTIGATION OF EFFECT OF ZEOLITE ON STRENGTH AND MICROSTRUCTURE DEVELOPMENT OF CEMENT STABILIZED CLAY

Abstract

Results of investigation of the effect of zeolite on the strength and microstructure development of cement stabilized clay soil are presented. Clay soil, collected from Giri Village, Gwagwalada area of Federal Capital Territory (FCT), Nigeria was stabilized with 0, 2, 4 and 6% cement, and admixed with 0, 3, 6, 9, 12 and 15% zeolite. Index properties tests were conducted on the natural soil, while Unconfined Compressive Strength (UCS) test was carried out on the natural soil and the soil treated with cement and zeolite. X-ray Fluorescence (XRF) was conducted on the soil, cement and zeolite, while X-ray Diffraction (XRD) and Scanning Electron Microcopy (SEM) tests were conducted on the natural soil and the soil treated with cement and zeolite. Results of the index properties of the clay indicated it classified under A-7-6 and clay of high plasticity (CH) based on AASHTO and Unified Soil Classification Systems respectively. The UCS increased from 71 kN/m2 for untreated soil to a maximum value of 1746 kN/m2 for the soil treated with 4% cement and 6% zeolite respectively. The XRF test result revealed silica, alumina and iron as the major oxides of the clay, while cement has quick-lime and silica, and zeolite composed of silica, alumina and sodium. XRD result showed that the clay composed of quartz, ankerite, orthoclase, montmorillonite and silicide minerals. Addition of 6% cement disintegrated the montmorillonite minerals to less active kaolinite mineral with introduction of calcite mineral. Addition of 4% cement and 6% zeolite further converted the montmorillonite mineral to kaolinite minerals with introduction of calcite and zeolite. The SEM result of the clay- cement-zeolite composite revealed a smooth, compact structure without pores, justifying the highest UCS value recorded at this mixture. 6% zeolite was therefore, observed to be the optimal zeolite for each of the cement contents considered in this study. The study also established that clay of high plasticity can be treated with 6% zeolite (and less cement content), to achieve the 1710 or 1750 kN/m2, reported in the literature, as criteria for design cement content, considered adequate for soil-cement composite as base course material for highway pavements with light to medium traffic.