Compressive Strength of Mortar by the Partial Replacement of Portland Cement with Calcined Clay and Limestone

This research studied the compressive strength of mortar by the partial replacement of Portland cement with Calcined Clay and Limestone (LC²). Investigated parameters consisted of three different levels replacement of cement with LC², i.e. 15% 30% and 50% by weight of cement and to determine the appropriate water content in the mortar by controlling the flowability to be between 105-115% according to ASTM C1437 Standard. Specimens for the compressive strength test were 5 cm cubes according to ASTM C109 Standard, whereby they were tested at 7, 14 and 28 days of curing. The results of this study showed that an increase in LC² replacement would lead to the need of more water in the mixture in order to keep the same flowability of mortar. Moreover the compressive strength of mortars with partial replacement of cement by ground calcined clay and limestone (LC²) would improve with curing ages. It was also found that when replacing a large amount of LC², i.e. 50%, the compressive strength during the first 7 days was reduced. The samples with the highest compressive strength were obtained when the samples with 30% replacement of LC², whereby the compressive strength at 28 days is 73.9 MPa.