Effect of the Combination of Calcined Shale and Pozzolanic Materials on Compressive Strength of Concrete

This study investigated the influence of individual constituents of calcined shale or hybrid constituents of calcined shale and fly ash or silica fume on the workability and compressive strength. Calcined shale is heat treated in a kiln and then ground to a finer powder and the calcination temperatures of 800 °C were used. The test results demonstrated that the workability and compressive strength decreased with the inclusion of calcined shale increased and the compressive strength of the specimens containing calcined shale all lower than that of the control specimens. It might be due to the higher water demand and lower CaO value. However, the hybrid batches with calcined shale and fly ash or silica fume enhanced better performance on compressive strength than individual constituents of calcined shale. The combination of 10 % calcined shale and 10 % silica fume in concrete seemed to give superior compressive strength and gave the highest value in the testing series. Finally, the inclusion of calcined shale is help to reduce the emissions of CO₂ and revealed an ecological advantage for concrete containing a binder blend of cement and calcined shale.