Can superabsorent polymers mitigate autogenous shrinkage of internally cured concrete without compromising the strength?

The paper “Super absorbing polymers as an internal curing agent for mitigation of early-age cracking of high-performance concrete bridge decks” deals with different aspects of using superabsorbent polymers (SAP) in concrete to mitigate self-desiccation. The paper concludes that “Addition of SAP leads to a significant reduction of mechanical strength”.

The experimental results are in contradiction with several publications and question the appropriateness of using SAP as internal curing agent. However, the observed strength loss – and possibly also other observations – seems to be caused by overestimation of SAP water absorption. This results in an increase in water/cement ratio (w/c) for concrete with SAP.

It is misleading to conclude on how SAP influences concrete properties, based on comparison of concrete mixes with SAP and reference concrete without SAP, if SAP mixes have higher w/c than the reference mix.