An experimental investigation was undertaken to evaluate the mechanical behavior of soil-cement mixtures. The primary motivation for the study was to investigate the innovative use of colemanite ore waste (CW) modified active belite cement (BC) in soil stabilization engineering (applications). The specific objectives of the research were to evaluate and compare: (1) compaction characteristics, (2) unconfined compressive stress-axial strain behavior, (3) unconfined compressive strength, (4) Young's secant modulus of elasticity, and (5) undrained shear strength characteristics of belite cement (BC)-clay and ordinary portland cement (OPC)-clay mixtures. BC and OPC were mechanically mixed with clay in five different dosages, i.e. 1.0%, 2.5%, 5.0%, 7.5% and 10.0% by using dry weight of clay, separately. Compaction characteristics of untreated soil, BC-clay and OPC-clay mixtures were evaluated at standard Proctor compaction energy. For a meaningful comparison of unconfined compression and triaxial test results, all specimens (untreated soil, BC-clay and OPC-clay mixtures) were prepared at maximum dry unit weight and optimum water content. Cylindrical samples of 50.0 mm in diameter and 100.5 mm in length were compacted in three layers and their strength characteristics were investigated at 1-, 7-, 14-, and 28-days curing times. Results of unconfined compression tests showed that cement dosage less than 5% has little effect on unconfined compressive strength (UCS) and exhibits ductile type of failure for both OPC-Clay and BC-Clay mixtures. In contrast, for cement content equal or greater than 5%, cement treatment significantly improved UCS and displayed brittle stress-strain behavior especially for BC-Clay mixtures. Similar behavior is obtained from undrained triaxial tests. The variation of undrained cohesion intercepts with respect to cement type, cement content and curing time is more sensitive than that of undrained internal friction angle. (C) 2013 Elsevier B.V. All rights reserved.