Mechanical strength and durability analysis of mortars prepared with fly ash and nano-metakaolin

Pozzolans such as fly ash (FA) and nano-metakaolin (MK) are the two industrial wastes that have attracted the attention of researchers due to their pozzolanic action that improves the performance of cementitious materials in an aggressive environment and can reduce global cement demand and lessen the emission of greenhouse gases. This study analyses the strength and durability properties of cement mortar with partial substitution of cement with MK in the presence of FA. The effect of substitution of MK in binary and ternary blends on strength and durability has been studied by varying the dosage of FA (5-20%) as well as MK (2.5-10%) and optimization of MK content has been carried out. A comparative analysis of beneficial aspects of FA and MK, along with their combination in optimized content at a fixed water/binder ratio of 0.5, has also been performed in terms of corrosion resistance through electrical resistivity and half-cell potential measurements. Further, the results have been correlated by microstructural analysis. The study reveals a significant increase in strength and durability of mortar at a dosage of 10% FA+7.5% MK with an increase in chloride, sulfate and corrosion resistance due to improved microstructure owed to the better pozzolanic action of the substituents with synergistic action. Thus, the partial substitution of cement with optimized content of MK (7.5%) in the presence of FA (10%) can not only help in solid waste management but can also reduce the cement consumption leading to sustainable construction.