Effect of superabsorbent polymers and expansive agent on the properties and microstructures of self-stressing high performance concrete

Abstract

In order to overcome the self-desiccation and high autogenous of high performance concrete (HPC), the superabsorbent polymers (SAP) and expansive agent (EA) are considered to be compositely incorporated, which has great significance to the HPC structures. This paper presents an experimental study on the compounded effect of SAP and EA on the properties of HPC. The workability, internal relative humidity (IRH), compressive strength and free expansive ratio as well as self-stress of HPC were examined. The influencing mechanism of SAP and EA on HPC was discussed. The results showed that the compressive strength of HPC generally decreases with the increases of EA and SAP contents and additional water ratio. The water release of SAP particles mainly occurs at 7–10 d to maintain a high IRH. The higher EA content induces the larger free expansive ratio and self-stress, caused by the increased hydration products of Aft and Ca(OH)2 bulks. For a low SAP content of 0.1%, the shrinkage is alleviated, but it becomes even worse for a higher SAP content. The total amount of pores increases with the inclusions of EA and SAP, except for the harm pores. The hydration products caused by EA could fill and compensate the pores left behind by the SAP particles, showing synergetic improvement effect. The self-stress values of HPC in this study are at the range of 2.73–3.44 MPa, From the present study, the SAP content of 0.1% is more recommended for the HPC in real engineering practices.