Abstract
Laboratory evaluations were performed to investigate the effect of internal curing (IC) by superabsorbent polymers (SAP) on the internal relative humidity (IRH), autogenous shrinkage, coefficient of thermal expansion (CTE), and strength characteristics of low water-cement ratio (w/c) mortars. Four types of SAP with different cross-linking densities and particle sizes were used. Test results showed that the SAP inclusion effectively mitigated the IRH drops due to self-desiccation and corresponding autogenous shrinkage, and the IC effectiveness tended to increase with an increased SAP dosage. The greater the cross-linking density and particle size of SAP, the less the IRH drop and autogenous shrinkage. The trend of autogenous shrinkage developments was in good agreement with that of IRH changes, with nearly linear relationships between them. Both immediate deformation (ID)-based and full response-based CTEs were rarely affected by SAP inclusions. There were no substantial losses in compressive and flexural strengths of SAP-modified mortar compared to reference plain mortar. The findings revealed that SAPs can be effectively used to reduce the shrinkage cracking potential of low w/c cement-based materials at early ages, without compromising mechanical and thermal characteristics.
Highlights
High-performance concrete (HPC), which typically has a low water-cementitious ratio (w/cm), is prone to early-age shrinkage cracking induced by internal drying [1,2]
Test results showed that the superabsorbent polymers (SAP) inclusion effectively mitigated the internal relative humidity (IRH) drops due to self-desiccation and corresponding autogenous shrinkage, and the internal curing (IC) effectiveness tended to increase with an increased SAP dosage
The findings revealed that SAPs can be effectively used to reduce the shrinkage cracking potential of low w/c cement-based materials at early ages, without compromising mechanical and thermal characteristics
Summary
High-performance concrete (HPC), which typically has a low water-cementitious ratio (w/cm), is prone to early-age shrinkage cracking induced by internal drying [1,2]. The internal drying is a process that consumes water from within the concrete itself (i.e., water from pores) for delayed hydration of unhydrated cement grains present in the matrix [2,3]. For this reason, the internal drying is clearly distinguished from typical long-term drying triggered by “diffusion-evaporation”. Taylor [8] and Nakataki and Gomi [9] described that shrinkagePolymers 2018, 10, 1074; doi:10.3390/polym10101074 www.mdpi.com/journal/polymers
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