Effect Of Curing Conditions On Carbonation Properties Of Concrete With Mixed Mineral Admixture

With the wide application of mineral admixtures in the production of concrete, the issue of carbonation has become the bottleneck of large-scale use of mineral admixtures. How to fully play the advantages of mineral admixtures under the condition of making sure of the durability of the concrete has become a major issue in the study of concrete. This paper is based on the research progress at home and abroad, carbonation resistance property of concrete under different curing condition with mixed mineral admixtures was mainly studied.In this paper, by adjusting the content of fly ash and slag powder,50percent of cement was replaced to produce concrete. After curing at different condition to study the effect of curing condition and mixed mineral admixtures on the peaceability, strength, water absorption ratio, resistance to chloride ion permeability, capillary water absorption and the carbonation resistance property of concrete, the research results are as follows:1. The slump of concrete with the amount of slag powder increased first and then decreased, it is the biggest when mixed with40percent fly ash and10percent slag powder; The strength of concrete mixed with fly ash and slag powder is higher than that with fly ash only, but is lower than single doped slag powder.2. Under the same curing condition, the water absorption ratio and capillary water absorption of the concrete mixed with fly ash and slag powder is smaller than the concrete with fly ash only, but bigger than that single doped slag powder. The property of resistance to chloride ion permeability and carbonation resistance of concrete mixed with fly ash and slag powder is better than the concrete mixed with fly ash only, but worse than that single doped slag powder. The gap between the water absorption ratio is obviously reduced when the content of slag powder exceeds20percent; the resistance to chloride ion permeability property of concrete increased significantly when the content of slag powder exceeds 10percent. When the content of slag powder exceeds30percent, the property of carbonation resistance of concrete improved obviously under the condition of the same moisture and the same temperature before form removal. The effect of slag powder content on the resistance to chloride ion penetration property is larger than the effect of curing condition.3. When the mix proportion is the same, different curing conditions have a great impact on the water absorption, resistance to chloride ion permeability and carbonation resistance property of concrete. When the standard curing time is more shorter, the curing moisture is more lower and the curing temperature before form removal is more higher, the water-absorbing ability of the concrete getting better, the property of resistance to chloride ion penetration and carbonation resistance getting worse. The property of resistance to chloride ion penetration of the concrete is good when curing under standard condition for3days, and the capillary water absorption reduced significantly; after7days of standard curing, the strength of the concrete tends to be stable, the speed of the decrease rate of water absorption decreased, the change of carbonation depth decreased.4. The carbonation property of concrete mixed with mineral admixture has a correlation with strength, water absorption ratio, resistance to chloride ion permeability and capillary water absorption. The lower the strength of concrete is, the greater the water absorption is, the poorer the resistance to chloride ion penetration is, the more the water absorption is, the poorer the property of carbonation resistance is. Conversely, the better the property of carbonation resistance is.