Effect of superabsorbent polymer on the shrinkage and crack resistance of concrete at early age

The superabsorbent polymer (SAP) with different volumes and modes of entrained water is incorporated into concrete to study the effect of SAP on the compressive strength, flexural strength, shrinkage, plastic cracking and electrical resistivity of concrete at early age. The result indicated that the influence of SAP with different modes of entrained water on the early strength of concrete is relatively obvious. It is beneficial for the early strength of concrete to add pre-absorbed SAP whose internal curing (IC) is detracted from mixing water and unabsorbed SAP. But the early strength of concrete is decreased by adding pre-absorbed SAP. The effect of pre-absorbed SAP is limited on shrinkage of concrete when IC water is detracted from mixing water. The unabsorbed SAP gradually decreases the concrete shrinkage with its volume increase. The moderate volume of pre-absorbed SAP can decrease the early concrete shrinkage. In addition, SAP can effectively alleviate the early appearance and development of concrete cracks. Furthermore, the pre-absorbed SAP can efficiently enhance the crack resistance of concrete. When the unabsorbed SAP is added, the cracking of concrete is reduced with the increase of volume. The longer the curing age, the more obvious would be the influence of SAP on the internal humidity of concrete, which effectively delays the increase of concrete resistivity.