Calcined calcium bentonite clay as a partial replacement of Portland cement in mortar

In this study, bentonite clay and lime were used as a partial replacement of Portland cement in mortar. The clay was calcined at 800, 850, 900 and 1000°C. Particle size distribution, chemical analysis, X-Ray diffraction, SEM analysis, and DSC analysis were completed as a high-level effort to characterize the chemical makeup of the bentonite clay. The Portland cement control mix had the highest compressive strength. However, all the 30% calcined bentonite clay/lime replacement mixes were about 90 – 99% of control at 28 days. Many of the 30% replacement mixes met the CSA A3000 strength requirement. The addition of lime was found to be fairly insignificant. A general variance regression was undertaken on the compressive strength results using Minitab on the factors of temperature (800, 850 and 900°C), days cured (3, 7, 28, 56, and 90), with calcined clay replacement (30, 50, and 70%), and lime replacement of the calcined clay in the binder mix (0, 10 and 20%). The general variance regression indicated that all factors and interactions were significant with a 95% confidence, except for the interaction of days cured and the amount of lime added. The most significant factors for the compressive strength were the days cured and the amount of clay replacement. The Normal Consistency results clearly indicated that when more ordinary Portland cement (OPC) was replaced with calcined clay, the volume of water required to obtain normal consistency also increased. The final setting times also followed the same trend with increased setting time with increased replacement of OPC with calcined clay. Based on the results and analysis conducted, it was recommended that the optimum mix was clay treatment at 800°C, 30% replacement with 0% lime.Applied Science, Faculty ofEngineering, School of (Okanagan)Graduat