Internal Curing by SAP in Ultra-High Strength Concrete with Cement-Silica Fume-Fly Ash Binder

Super-absorbed polymer (SAP) is an effective internal curing materials for reducing autogenous shrinkage and improving cracking resistance of ultra-high-strength concrete (UHSC). This study investigated the compressive strength, shrinkage properties of UHSC with cement–silica fume–fly ash binder. The composition of the binder was designed using seven-batch factorial design method. The relationships between the binder composition and the properties were expressed in contours. Results showed that, silica fume could improve the compressive strength and total shrinkage of UHSC. However fly ash reduced the compressive strength and total shrinkage of UHSC to certain extent. On the other hand, under the internal curing of SAP, the silica fume and fly ash demonstrated positive synergistic effects on the compressive strength. At the early age of hydration, the effectiveness of internal curing first increases and then decreases with the increase of fly ash and silica fume content. However, at the later age of hydration, the effectiveness of internal curing by SAP reduced because of the pozzolanic activity of silica fume and fly ash