Abstract
In order to explore the influence of curing time on the surface permeability of concrete, 10 groups of high content fly ash and slag concrete with two kinds of water‐binder ratio were designed. There were cured under five curing methods, respectively. The influence of curing time on the surface permeability of concrete was studied. The mechanism was explained by hydration heat and mercury intrusion porosimetry. The results show that inadequate curing time leads to insufficient hydration of cementitious materials in concrete with large amount of mineral admixtures and significant increase in the diffusion of chloride ions on the surface of concrete. Standard curing for 14 days can basically ensure the chloride ion penetration resistance of concrete with large amount of mineral admixture. When the standard curing time is less than 7 days, the chloride ion penetration resistance deteriorates seriously. Under the condition of insufficient standard curing time, adding a small amount of limestone powder can effectively enhance the chloride ion permeability of concrete with a large amount of fly ash and slag.
Highlights
Reinforced concrete structure is the most widely used structural form in the world, and its structural durability has become one of the most concerned hotspots in the field of civil engineering. e concrete surface has a protective effect on the interior of the structure and its reinforcement and is the first barrier to prevent external erosion [1, 2]
Studies have shown that there is a rich slurry effect and boundary effect with the formwork when concrete is poured and hardened, which results in large differences in the microstructure between the concrete surface and its internal body [3–5]. erefore, the study of concrete surface permeability is of great significance to the exploration the durability of concrete structures
The number “F35–0.45′′ indicates that the cementitious material in the concrete contains 35% fly ash and the water-binder ratio is 0.45. e number “SL 45–0.45′′ means that the cementitious material in this mix proportion concrete contains 45% slag and 5% limestone powder by mass, with the water-binder ratio of 0.45
Summary
Reinforced concrete structure is the most widely used structural form in the world, and its structural durability has become one of the most concerned hotspots in the field of civil engineering. e concrete surface has a protective effect on the interior of the structure and its reinforcement and is the first barrier to prevent external erosion [1, 2]. Concrete based on cement binder is the basic building material. In order to reduce carbon dioxide emissions and protect nonrenewable resources, industrial waste is used as much as possible to reduce the content of silicate clinker in cement and concrete components [7, 8]. Fly ash is one of the residues produced by coal combustion for power generation and heating. It is captured by an electrostatic precipitator or a bag filter before flue gas emission. Modern concrete often uses a large amount of mineral admixtures to replace part of the cement, which reduces the heat of hydration of concrete, improves the later strength, and reduces carbon emissions in the building materials industry [12–15]
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