Efficiency of internal curing by superabsorbent polymers (SAP) in PC-GGBS mortars

Abstract

This paper evaluates the effect of superabsorbent polymers (SAP) on hydration and microstructure of PC-GGBS mortars. Development of autogenous shrinkage, microstructural characteristics (MIP/SEM) and compressive strength were analysed during the first 90 days. Four levels of Portland cement (PC) replacement by GGBS (0%, 25%, 50% and 75%) and two types of SAP with different water absorption capacities were considered. The results proved the efficiency of internal curing by SAPs in PC-GGBS systems due to significant reduction in autogenous shrinkage, especially for higher contents of GGBS. SAP facilitates GGBS hydration activated by portlandite; its products can be deposited into the nano pores leading to a small relative expansion of the hardened bulk volume. This process is initiated during the second week and it lasts until the sixth week. Despite increased total porosity, compressive strength of SAPs modified mortars is comparable to the reference samples for low GGBS contents in advanced ages.

The Influence of Dosing Method and Material Characteristics of Superabsorbent Polymers (SAP) on the Effectiveness of the Concrete Internal Curing

“…Those two facts seem to indicate that the homogeneity of the material increased, i.e., the degree of hydration increased slightly without compromising the pore distribution. This conclusion stands in stark contrast with other published results [ 27 , 37 , 38 , 47 ]. Usually with higher dosages of SAP introduced into concrete mix by means of the most common methodology of dosing, a decrease in mechanical properties of concrete is observed [ 32 , 33 ].…”

“…In the case of SAP MR series of concrete mixes, results fit in the trend of literature research results [ 27 , 32 , 33 , 38 ]. The drop in strength is increasingly stronger as the percentage of mixing water absorbed by SAP increases.…”

“…Analyzing the published research results, the decrease in compressive strength is visible as the proportion of water absorbed in the total amount of mixing water increases [ 27 , 32 , 33 , 35 , 36 , 37 , 38 ]. The reason behind this behavior of the concrete composite is the uneven distribution of SAP in the concrete mix.…”

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

“…It was also reported that the addition of SAP in high performance OPC concrete leads to a reduced shrinkage [16,26,27,29]. Fernando et al [30] partially replaced OPC with slag in mortars and found that mortars with SAP have reduced autogenous shrinkage, especially when slag content is high. Oh and Choi [20] and Song et al [21] estimated the effect of internal curing by SAP in AAS mortars and both reached a conclusion that SAP is an effective internal curing agent resulting in large reduction of shrinkages with comparative decrease in compressive strength.…”

Effect of Internal Curing by Super Absorbent Polymer on the Autogenous Shrinkage of Alkali-Activated Slag Mortars

“…IC was originally defined by the American Concrete Institute (ACI) as supplying water throughout a freshly placed cementitious mixture using reservoirs, via pre-wetted lightweight aggregates [ 15 ], pre-wetted crushed returned concrete fines, super absorbent polymer(SAP) and other carriers that readily release water, as needed for hydration or to replace moisture lost through evaporation or self-desiccation. SAP is widely used for IC of cement-based materials: pastes [ 16 , 17 ], mortars [ 18 , 19 ], concretes [ 20 , 21 , 22 , 23 , 24 , 25 , 26 ], and alkali-activated materials: pastes [ 27 , 28 ], mortars [ 29 , 30 , 31 , 32 , 33 ] due to its super water absorption capacity. Oh and Choi [ 30 ] investigated the effect of SAP on the hydration process and autogenous shrinkage.…”