Suitability of cement combinations for carbonation resistance of structural concrete

Purpose – This paper aims to assess the suitability of cement combination containing CEM I, fly ash, silica fume and metakaolin for durability design against carbonation-induced corrosion in concrete. Design/methodology/approach – Cube compressive strengths at 28 days and accelerated carbonation depths at 28 days and at various exposure ages were determined at the water/cement ratios of 0.35, 0.50 and 0.65. To assess their suitability for carbonation-induced corrosion, the material costs and embodied carbon dioxide (eCO2) contents of the concretes at equivalent performance were compared. Findings – Cement combination concretes achieved equal carbonation resistance with CEM I at higher compressive strengths, lower water/cement ratios and higher cement contents. The comparison of the concretes, at equivalent performance, based on the carbonation-induced corrosion exposure classes XC3 and XC4 (Table A.4 of BS 8500-1), shows that ternary and more binary cement concretes have lower costs and eCO2 contents than those recommended in Table A.6 of BS 8500-1. Research limitations/implications – This analysis is limited to a working life of 50 years. Further research is needed to verify the suitability of the cement combinations for a working life of 100 years and for the other aspects of durability design covered in BS 8500. Practical implications – Cement combination concretes have lower eCO2 content. Hence, when they are cheaper than CEM I concrete at equivalent performance, they would make concrete construction more economic and environmentally compatible. Originality/value – This research suggests the inclusion of metakaolin and ternary cement combination concretes in BS 8500 for durability design against carbonation-induced corrosion.