Fresh‐state performance design of green concrete mixes with reduced carbon dioxide emissions

The use of environment‐friendly cement‐replacement materials results in concrete mixes with significantly reduced water‐to‐binder ratios, leading to increased viscosity and yield stress. This may be considered a hindrance to the widespread implementation of this green concrete technology. In this comprehensive experimental study, a performance‐based design was applied to select different concrete mixtures for reduced carbon dioxide (CO 2 ) emission and improved performance in terms of both fresh and hardened states. A parameter study was carried out to study the rheological properties, compressive strength, and CO 2 emissions of 26 mortar mixes with different binder systems and different water‐to‐binder ratios (W/B) with the aim of determining alternative low‐environment impact combinations. A strong effect of the paste composition (binder amount) on the plastic viscosity and resulting CO 2 emissions was observed. For fixed proportions of paste and fine aggregate the plastic viscosity shows a non‐linear decreasing trend to the W/B ratio and non‐linear increasing trend to the B/(W+B) ratio. Finally, a successful candidate paste composition satisfying the performance requirements was selected as a reduced CO 2 emission alternative. The candidate paste composition (Mix No. 6) with relatively large amounts (fly ash / cement = 3) of supplementary cementitious materials (fly ash) was selected for the development of environment‐friendly concrete mixtures. The maximum compressive strength increase with this mix was found to be around 25% and maximum CO 2 reduction obtained was about 68% when compared to that of the control mix. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.