Microstructural and Strength Characteristics of Cement Treated Clay Stabilized with Zeolite for Road Base Application

Abstract

The stabilization of clay soils with cement has been identified to be uneconomical, and its production is not environmentally friendly. The addition of pozzolanic material to cut down on the use of cement is very pertinent. Clayey soil was stabilized with 0, 2, 4, and 6% cement admixed with 0, 3, 6, 9, 12, and 15% zeolite. Index properties tests were conducted on the clay, while the unconfined compressive strength (UCS) test was carried out on the clay soil and clay treated with the selected composition of cement and zeolite. Tests including X-ray fluorescence (XRF) were conducted on the clay, cement, and zeolite. X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests were conducted on the clay and clay mixed with the selected composition of cement and zeolite. The objective of this study is to investigate the effect of zeolite on the strength and microstructure of cement stabilized clay soil. Index properties result in the group the clay as A-7-6 and clay of high plasticity (CH) based on AASHTO and Unified Soil Classification Systems, respectively. The (UCS) increased from 62kN/m2 for untreated clay to a maximum of 1552 kN/m2 for clay treated with 6% cement and 6% zeolite after 60 days of curing. The (XRF) test revealed major oxide compositions of the clay as silica, alumina, and iron; that of cement was quicklime and silica, while that of zeolite is silica, alumina, and sodium. The (XRD) result showed that the clay contained active montmorillonite along with other minerals. The addition of 6% cement disintegrates the montmorillonite minerals to less active kaolinite minerals with the introduction of calcite minerals. The addition of 6% cement and 6% zeolite further converted the montmorillonite mineral to kaolinite minerals with the introduction of calcite and zeolite. The (SEM) result of the clay mixed with cement and zeolite revealed a smooth, compact structure without pores which justifies the highest UCS value recorded in this mixture. 6% zeolite was observed to be the optimal zeolite that gave the highest UCS for each cement addition.