Speaker
Description
In an increasingly competitive market, the precast industry is constantly looking for ways to ensure a quick turnaround and rapid delivery with an acceptable cost and without harming the quality of the final concrete element. One of the most common levers allowing to boost production cycles is to adopt advanced curing techniques like steam curing or heat curing. These options are not effective in terms of cost and CO2, but still a common practice used when quick formwork removal is needed.
To increase productivity a potential solution that consists in incorporating calcium aluminates as strength boosters is proposed. A complementary study showed that incorporating calcium aluminates in a self-compacting concrete (SCC) formulation for the precast industry led to an improvement of the resistance to chloride and had no significant effect on carbonation. The focus of this study is to investigate the strength development of a self-compacting concrete (SCC) formulation for the precast industry including 50kg/m3 and 100kg/m3 calcium aluminates as Portland cement substitute.
Compressive strength results carried out from 6h and up to 180d show respectively 7.8MPa and 16.7MPa for the system containing 50 and 100kg/m3 at 6h. On the other hand, the reference shows no strength development at 6h. At 180d, the three tested systems have close strength values with no strength decrease for accelerated systems over time. Bound water correlates well with the strength results. XRD-Rietveld quantification shows that in the boosted systems, ettringite is the main crystalline hydrate forming and no conversion products (C3AH6, C2AH8, CAH10) are formed. Mercury Intrusion Porosimetry measurements show that porosity keeps refining between 28d and 180d for the reference mix and the system containing 50kg/m3 of calcium aluminates accelerator. The total porosity is also reduced. This is explained by a further hydration of the silicates phases.
Affiliations
Imerys, 01Rue le Chatelier, 38090 Vaulx-milieu-France
| Keywords | precast, calcium aluminates, strength, hydration |
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