Impact of adding limestone and metakaolin powder as cement paste replacement on durability of mortar

Document Type : Research articles

Authors

1 Department of Civil Engineering, Faculty of Engineering at MTI Modern University for Technology & Information, Cairo, Egypt

2 Department of Civil Engineering, Faculty of Engineering at Shoubra, Benha University, Cairo, Egypt

Abstract

Portland cement is crucial in global infrastructure, notably in concrete and mortar for construction. Its production, contributing 5-8% of human-made CO2 emissions, poses a significant environmental challenge amplified by rising global population and housing needs. Mitigating carbon emissions per ton of concrete is essential for sustainable construction, crucially reducing the global carbon footprint. This study investigates the impact of incorporating limestone powder (LS) and metakaolin powder (MK) as a cementitious paste volume replacement on the compressive strength, permeability, and durability of cement mortar specimens. Firstly, LS was added separately with 10%, 15%, and 20% by equal volume of cement paste while, secondly MK replaced by 20% and 30% by equal volume of cement paste and finally, combined LS and MK with ratios of 10% LS with 20% MK, 15% LS with 30% MK, and 20% LS with 30% MK were used. The results showed that higher proportions of LS decrease compressive strength, with optimal performance observed at 15% LS without additional additives. Substituting 30% MK significantly enhanced compressive strength, surpassing approximately 30% improvement compared to the OPC mortar. The combination of 15% LS and 30% MK proved most effective, achieving high compressive strength with a total replacement ratio of up to 45% of cement paste volume. The sorptivity rate decreased markedly with 15% LS and 30% MK individually, and their combination demonstrated that the optimal replacement ratio was achieved with 15% LS and 30% MK.

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