Workability and strengths of ternary cementitious concrete incorporating calcined clay and limestone powder

Abstract

Problems associated with the production and utilization of Portland cement have necessitated the use of alternative or supplementary binders in concrete production. This study investigated the use of two supplementary binders; calcined clay (CC) and limestone powder (LP) as substitutes for cement in the production of concrete. Both the calcined clay and limestone powder were characterized using X-ray diffraction (XRD), X-ray Fluorescence (XRF) and Scanning Electron Microscope (SEM). Blended concrete mix proportions containing calcined clay and limestone powder were prepared and tested for fresh and hardened concrete properties including workability, compressive and splitting tensile strengths. The outcomes of this research showed that calcined clay is majorly amorphous with traces of crystal particles while limestone is all crystal particles. Based on oxides composition, calcined clay can be used as pozzolan while limestone powder can be best utilized as pore fillers. The addition of both calcined clay and limestone powder resulted in the loss of slump, although the effect is more pronounced in concrete blends containing calcined clay. While the inclusion of limestone powder caused a slight loss of strength in the blended concrete, it can still be utilized to achieve reasonably high strengths. Only concrete mix incorporating 10% of calcined clay gives a slight increase in strength, hence calcined clay can be utilized to a limited volume in concrete production.