The effect of steam curing regimes on the chloride resistance and pore size of high–strength green concrete

Abstract Since diminishing the consumption of cement has many benefits, ongoing research on the incorporation of the industrial/agricultural wastes as an alternative or partial substitution for cement is of paramount significance. This study aims to examine the effect of steam curing regimes (SCRs) on the chloride resistance and microstructure of high-strength green concrete (HSGC). To this end, palm oil fuel ash, a type of waste from the palm oil industry, was treated so that ultrafine palm oil fuel ash (U-POFA) could be obtained. U-POFA was utilized as a partial substitute of the mass of cement at 0%, 20%, 40%, and 60% to produce HSGC. Varying steam curing temperatures (50 °C, 65 °C, and 80 °C) and varying periods (6, 11, and 16 h) were applied to the HSGC. Moreover, a steam curing cycle that did not exceed 24 h was applied. The tests performed on the HSGC samples included compressive strength (CS), rapid chloride permeability, and rapid chloride migration. The evaluation of the microstructure of the HSGC samples was undertaken via Mercury Intrusion Porosimetry (MIP) in addition to scanning electron microscopy with energy dispersive x-ray. The results showed that the application of SCRs with a high volume with UPOFA resulted in enhanced CS, chloride resistance, and microstructure properties of HSGC at an early age of 3 days and a later age of 360 days. Such enhancement in the concrete properties mainly depends on the cement replacement rates by U-POFA, temperature, and the steam curing period. It was, therefore, concluded that U-POFA played a key role in reducing the negative impact, which might have been caused by the utilization of varying SCRs.