Predicting relative compressive strength of concrete containing superabsorbent polymers

Superabsorbent polymer (SAP) can affect the strength of concrete both positively and negatively, but the overall direction and degree remain controversial. By coupling the influence of paste strength and SAP void content, this paper presents a model to calculate the long-term compressive strength of a SAP-modified concrete relative to another one without SAP but with the same water-to-binder ratio (w/b) and the same paste content. Results indicate that in a cement concrete, there exists a critical w/b, above which any amount of internal curing water reduces strength. The critical w/b depends on paste content. At a certain paste content, the largest possible degree of enhancement is greater, when w/b is lower. The model is validated by experimental results, both original and from the literature, and is applicable to concretes whether or not supplementary materials are used.