Effect of internal curing with super absorbent polymers on autogenous shrinkage of concrete at early age
Abstract High performance concrete (HPC) is used extensively in practice. However, this type of concrete has a low water to cement w c ratio, which causes self desiccation and leads to a rather high autogenous shrinkage (AS) AS then increases the risk of cracking if the concrete is restrained from shrinking freely at early age. Internal curing (IC) has been extensively used in reducing AS and consequently mitigating the high risk of early age cracking of HPC. Super absorbent polymers (SAPs) can supply additional IC water for hydration of concrete, thereby counteracting the effects of self desiccation. Although experimental studies were conducted to mitigate the AS of internally cured concrete with SAP, research on the relationship between the AS of concrete and the amount of IC water provided by SAP is still lacking. Thus, an experimental study on the effect of IC on the early age expansion, AS development, AS rate, and IC efficiency of concrete with SAP was conducted. Test results showed that (1) the early age expansion occurred obviously prior to the first day for the internally cured concrete, and the maximum expansion increased with the increase of IC water; (2) the ultimate AS at 28 days and AS rate of internally cured concrete decreased with the increase of the amount of IC water; (3) the proposed model to estimate the AS of internally cured concrete with SAP considering the early age expansion and amount of IC water indicated good correspondence with the experimental results; and (4) the IC efficiency of SAP decreased with the increase of IC water in concrete.