Cement-superplasticiser compatibility - Issues and challenges

This paper summarises the current knowledge in the scientific community about the interaction between cement and high-range water reducing chemical admixtures or superplasticisers. The definition, classification and chemical compositions of the water reducing chemicals are discussed first, followed by a review of their mechanism of action in concrete. Test methods to evaluate the effectiveness of superplasticisers are also reviewed. Specific issues of incompatibility are then addressed, namely, loss of workability, alteration of setting behaviour, reduced rates of strength gain, and change in long term response. The factors controlling the compatibility are discussed next in detail, including the role of the chemistry (of cement and admixture), the presence of other mineral and chemical admixtures, and the proportioning of concrete. Finally, a detailed insight into the needs for further research is provided.