Influences of superabsorbent polymer (SAP) on the compressive strength and crack-healing ability of self-compacting concrete containing high-volume ground bottom ash

Abstract

This study investigated the use of superabsorbent polymers (SAPs) as an internal curing and crack-healing material in self-compacting concrete (SCC) made with high-volume ground bottom ash (GBA). With a total binder content of 600 kg/m 3 and a water-to-binder (w/b) ratio of 0.27, ordinary Portland cement (OPC) was replaced with pozzolanic materials by up to 70 % by weight of the binder. The pozzolanic blend comprised high-volume GBA, original fly ash (FA), and nano-silica (NS) in three weight ratios: 70:0:0, 60:10:0, and 58:10:2 (GBA:FA:NS). Additionally, pre-absorption with SAP and a saturated calcium hydroxide (Ca(OH)₂) solution was employed, and the crack-healing ability of SCC with SAP was observed. The results demonstrated that SAP significantly controlled the slump flow and T 50 while reducing the required dosage of superplasticizer. However, an increase in SAP content led to a decrease in compressive strength. Reduced water flow rate through the cracked concrete was observed for the first two weeks in SCC mixes containing 0.6–1.8 % of SAP by weight of the binder, decreasing by over 90 % after curing for 28 days. In SCC mixes incorporating SAP saturated with Ca(OH) 2 , a 98 % reduction in water flow rate was achieved, in addition to a slight increase in compressive strength, due to the additional formation of calcium-silicate-hydrate (CSH) gels and calcium carbonate (CaCO 3 ) precipitation. Furthermore, the inclusion of SAP or SAP saturated with Ca(OH) 2 significantly reduced chloride penetration in SCC. Microstructure analysis revealed the presence of crack-healing products including CSH gels and CaCO 3 precipitation.