Abstract
A comparison was made between the impact of raising the thermostatic temperature and the impact of prolonging the thermostatic time on the performance of steam-cured concrete containing a large portion of fly ash (FA) or ground granulated blast furnace slag (GGBS) by analysing the form removal strength, chemically combined water content, reaction degree, strength development, chloride permeability, and volume stability. For the materials and test conditions reported in this study, raising the thermostatic temperature is more favourable for concrete containing FA, as indicated by the significantly higher form removal strength and the higher growth of reaction degree of FA compared with prolonging the thermostatic time. With an increase in the thermostatic temperature, the hydration degree of a binder containing FA or GGBS initially increases and subsequently decreases. Although concrete containing FA can obtain satisfactory form removal strength with steam curing at 80°C, the late strength development of concrete containing FA is slow for the same curing conditions. The effect of the late performance of resistance to chloride ion permeability improved by FA is better than the effect improved by GGBS. The risk of destroying the structure of concrete containing a large portion of FA or GGBS due to delayed ettringite formation (DEF) is minimal when specimens were steam-cured at 80°C.
Highlights
Concrete is one of the most common construction materials
(2) The order of the degree of influence of prolonging the thermostatic time on improving wc content of binders is the binder containing large portion mineral admixtures > the pure cement paste at the same thermostatic temperature. This finding may be attributable to this reason: when considering the binder containing a large portion of ground granulated blast furnace slag (GGBS) or fly ash (FA), the thermostatic time may Curing temperature (∘C)
This result indicates that increasing the thermostatic temperature to 80∘C can effectively enhance the hydration degree of paste containing a large portion of FA or GGBS
Summary
Concrete is one of the most common construction materials. Cast-in-situ concrete and precast concrete are two techniques that housing developers and construction workers often adopt. The formation of ettringite produced by cement hydration in the case of a minimum curing temperature of 70∘C is decomposed during steam curing and reformed during the service life This process is called delayed ettringite formation (DEF), and it can substantially weaken the late performance of concrete [13,14,15]. By adjusting the thermostatic time and the thermostatic temperature under steam curing conditions, concrete with a large portion of mineral admixtures may achieve the required form removal strength. Our study focused on a comparison between the impact of prolonging the thermostatic time and the impact of raising the thermostatic temperature on the hydration degree of a binder, the strength development and the resistance to the chloride ion permeability of concrete, and the volume stability of steam-cured concrete with a large portion of mineral admixtures
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