Rheological behavior of low shrinkage very high strength self-compacting concrete

Abstract

High performance self-compacting concretes have high potential to develop shrinkage, and possible solutions for this comportment should not compromise the workability of the mixtures. This work investigated rheological behavior over time of high performance self-compacting concretes (HPSCCs) containing an expansive admixture (EXA) and a shrinkage-reducing admixture (SRA). Cement pastes formulated from these HPSCCs were produced. The flow behavior of the HPSCCs and pastes were evaluated by rheometry and workability tests for up to 90 min. Isothermal calorimetry was utilized to measure the effect of EXA and SRA on cement hydration. The results showed that cement pastes containing SRA required less superplasticizer than pastes containing EXA and reference mixture, for the same workability. The flow behavior of cement pastes was similar at 90 min, independent of the rheological model adopted (Herschel-Bulkley or Bingham). The dynamic yield stress values of pastes containing some shrinkage mitigator agent ranged from 143 to 233 Pa at 90 min. The mixtures containing EXA showed an accelerated hydration, while incorporation of SRA in the pastes resulted in a retarded hydration of Portland cement compared to the reference mixture. After 90 min, by the slump flow diameter, all concretes could still be considered as self-compacting. The highest flow loss (−19.1%) was observed for concrete containing 15% EXA and the lowest (−0.1%) for the concretes containing 0.5% and 1.0% of SRA. After 90 min, the dynamic yield stress values of HPSCCs ranged from 19.5 to 40.7 Pa. Overall, shrinkage mitigator agents can be used in HPSCCs without compromising the workability of the mixtures.