Title:
Self-Accelerated Reactive Powder Concrete Using Partially Hydrated Cementitious Materials
Author(s):
Ahmed M. Soliman and Moncef L. Nehdi
Publication:
Materials Journal
Volume:
108
Issue:
6
Appears on pages(s):
596-604
Keywords:
Accelerating admixture; derivative thermo-gravimetric analysis; reactive powder concrete; thermo-gravimetric analysis; ultra-high-performance concrete.
DOI:
10.14359/51683462
Date:
11/1/2011
Abstract:
This study pioneers the concept of self-accelerated concrete. The effect of adding partially hydrated cementitious materials (premade or from returned/unused concrete) on the setting and hardening process of reactive powder concrete (RPC) cured at various temperatures was investigated. The partially hydrated cementitious materials (PHCMs) were added at rates of 25, 33, and 50% of the overall batch weight. Similar mixtures incorporating chloride-based accelerating admixtures (CAs) and nonchloride-based accelerating admixtures (NCAs) were also tested for comparison. The results indicate that the added PHCMs alert the hydration kinetics and act as a setting and hardening accelerator. Mixtures incorporating PHCMs showed comparable or higher early-age compressive strengths than those of both the control mixture and mixtures incorporating accelerating admixtures. Microstructure analyses indicate that the addition of PHCMs enhances the nucleation and renews the formation process of calcium silicate hydrates (CSHs) through diminishing the protective layer formed around anhydrated tricalcium silicate (C3S) during the pre-induction period. Therefore, using PHCMs paves the way for self-accelerated concrete without the need for accelerating admixtures, providing a safe and cost-effective method for precast and cast-in-place concrete. Using leftover and unused concrete in this process enhances the sustainability of concrete and minimizes disposal in ready mixed concrete operations.