Effect of binder characteristics on workability, hydration, and strength of 0.42 w/b cementitious systems with superabsorbent polymer admixtures

This study aimed to characterize the effects of changes in binder characteristics on fresh and hardened properties of 0.42 w/b cement pastes and mortars internally cured with superabsorbent polymers (SAP) in the absence of additional “mixing water”. Industrially-sourced SAP was characterized in five binder systems: three different Type I portland cements (PCs) (each with different alkalinity and fineness), Type III PC, and a binary system (70% of Type I PC and 30% of slag cement). Characterization techniques included gravimetric absorption; mortar flow; isothermal calorimetry; thermogravimetric analysis; microstructural analysis of SAP voids; and determination of 3-, 7-, and 28-day compressive strength and 7- and 28-day flexural strength. SAP absorption capacity and mortar flow varied across binders. However, hardened properties of Type I PC pastes and mortars were similarly affected by the addition of SAP, regardless of cement source. Type III PC pastes and mortars containing SAP showed increased early-age compressive strength and rate of hydration. The 3- and 28-day compressive strength values for mortars prepared with binary cementitious system and SAP were higher than those of companion mortars without SAP. Across Type I cement sources, hardened properties of pastes and mortars were similarly affected by the addition of SAP, while changes in fresh properties due to the addition of SAP were influenced by changes in cement chemistry. Synergistic acceleration of strength and hydration was observed in Type III pastes and mortars with SAP and a mitigating effect of SAP was observed on the retardation of strength development in the binary cementitious system.