Durability of concrete containing metakaolin and palm oil fuel ash under cyclic environment

Concrete incorporating metakaolin (MK) and palm oil fuel ash (POFA) was suggested as both binary- and ternary-blended concrete. The durability of concrete blended with MK and POFA was assessed through exposure to sodium chloride under wetting and drying cycles. Changes in compressive strength and the resistance of chloride penetration of the concrete mixtures were evaluated. The results indicated that MK and POFA enhanced the compressive strength of concrete at later ages. The compressive strength increased during sodium chloride exposure relative to water curing until a specific limit, but it began to decline after 300 days. MK and POFA demonstrated very low chloride ion permeability in concrete, as proposed by ASTM C1202, and decreased the depth of chloride penetration to less than 14 mm. The enhancement of durability performance is attributed to the pore refinement, pozzolanic activity, and chloride binding capacity of MK and POFA. X-ray diffraction and scanning electron microscopy of the combined effect of MK and POFA in concrete revealed an enhancement in the microstructure and the resistance to chloride penetration.