An overview on the effect of internal curing on shrinkage of high performance cement-based materials

Abstract

High performance cement-based materials, such as high or ultra-high performance concrete (HPC or UHPC) have been widely used and still faces the risk of cracking caused by shrinkages, especially autogenous shrinkage. Internal curing is an effective method to reduce or even eliminate autogenous shrinkage and has effects on chemical shrinkage, dry shrinkage, etc. The commonly used internal curing materials include super-absorbent polymer (SAP) and porous materials. Porous materials refer to lightweight aggregate (LWA) and porous superfine powders. In this paper, the internal curing materials has been divided into two categories based on water absorbing mechanism. The effects of these two categories of internal curing materials on shrinkage of high performance cement-based materials are reviewed. The addition of internal curing materials releases internal curing water, postpones the drop of internal RH, and reduces autogenous shrinkage, but increase chemical shrinkage. The addition of internal curing materials with extra water increases drying shrinkage. The mechanisms of shrinkage on internal curing are also summarized and discussed. However, those mechanisms only focus on certain type of shrinkage. To reduce the risk of cracking more effectively, the relationship of different type of shrinkages should be established.

Comprehensive approach to evaluation of mechanical properties of waste aggregate concrete reinforced by steel fiber

“…Calculated values of both factors for tested SFRCs are graphically presented in Figure 5. Equations (11) and (12) describe relations visible in Figure 5. It can be easily observed that all tested SFRCs fulfill both requirements, thus reinforcement substitution is enabled in all analyzed cases.…”

Internal curing of alkali-activated fly ash-slag pastes using superabsorbent polymer

“…Chemical shrinkage is recognised as one of the main causes of early-age autogenous shrinkage resulting from volumetric difference between chemical reactants and products in matrix. The previous studies of chemical shrinkage in OPC system reported that the inclusion of SAP increased chemical shrinkage since the additional water promoted further hydration [18]. Thus, more capillary voids were formed, which contributed to a greater shrinkage.…”

“…In general, various curing methods including external and internal curing are applied to reduce shrinkage of concrete by maintaining the relative humidity. The internal curing method has better effects by adding materials with a high water absorption capacity, which can gradually release water during concrete hardening, such that additional water is supplied to the surrounding matrix once self-desiccation occurs, which can then eliminate shrinkage and stimulate further reaction [18][19][20][21]. Lightweight aggregate and superabsorbent polymer (SAP) have been commonly used as internal curing agents in previous research on internal curing of concrete.…”

“…Among them, SAP shows superior absorption and desorption capacity, allowableness of free design of form and size of concrete composite, resistance of concrete to chloride penetration and lower cost [18,[22][23][24].…”

“…Consequently, the strength development of mixtures containing SAP is affected due to those macro voids [28]. Liu et al [18] explored the effect of SAP on mitigation of shrinkages in high strength OPC concrete and found that SAP significantly reduced autogenous shrinkage and drying shrinkage with the dosage around 0.3% to 0.9%. It was also reported that the addition of SAP in high performance OPC concrete leads to a reduced shrinkage [16,26,27,29].…”