Investigation of mechanical properties and permeability of concrete containing metakaolin, zeolite, and fly ash with two and three compounds

In this study, different combinations of replacement of metakaolin, zeolite and fly ash in single, binary, and ternary mix designs were investigated in order to determine the optimal amount of suitable pozzolans. Fifty mix designs with constant water to cement ratio were made and the results of compressive strength, tensile strength, slump, specific gravity, water absorption, and volumetric electrical resistivity of concrete were recorded in order to evaluate the effect of type and amount of pozzolans and the effect of their compositions. The results showed that the highest amount of compressive strength was related to the ternary composition of pozzolans, and the amount of replacement was 3% (M3Z3F3). 3-, 7-, 28- and 90-days compressive strength increased by 14.8%, 24.1%, 41.1% and 54.1% compared to the reference sample, respectively. Compressive strength of samples containing single, binary and ternary mixes with a total of up to 45% will increase the compressive strength by different percentages and will have a further downward trend. The tensile strength of concrete in all samples containing binary and tertiary compounds of pozzolanic materials was higher than the reference sample with the highest increase related to M5Z5, M5F5, Z5F5 with 84.2%, and M3Z3F3 with 94.7%. The maximum reduction of water absorption is in the ternary mix designs M13Z13F13 and M15Z15F15 with a decrease of 75.8% compared to the reference sample. In all samples containing pozzolanic materials, the amount of electrical resistance has increased compared to the reference sample (from 1.3 to 9.1 times). The amount of electrical resistivity of concrete samples containing ternary composition was higher than binary and single. The maximum is related to M13Z13F13 and M15Z15F15 designs, which increased 9.1 times more than the reference sample. The presence of more than 40% pozzolanic values has almost no effect on the mechanical properties of concrete.