ABSTRACT

Worldwide there is a dominance of prescriptive-type specifications in industry, focusing mainly on minimum cement content, maximum water/binder ratio and compressive strength. According to Wasserman et al. (2009), these specifications resulted from previous practice and experience from times when there was no availability of chemical admixtures or supplementary cementitious materials (SCMs) to contribute to mixture properties. Today, in many cases, such specifications do not prove to be favourable as various problems can arise from their adherence (Wasserman et al. 2009): since cement is the most expensive constituent of concrete mixtures, a higher cement content results in higher costs. From a technical point of view, higher binder content may result in higher strengths, depending on the amount of water used, but it may also result in a higher paste volume, thus making the mixture more susceptible to cracking caused by shrinkage, thermal effects and Alkali-Silica reaction (ASR). As such, there is a worldwide need to reduce the binder content in concrete, a trend which is inhibited by the general opinion among numerous professional engineers that high binder contents are a guarantee for higher durability.