Carbonation Depth Model and Prediction of Hybrid Fiber Fly Ash Concrete

The concrete is weakly alkaline, the alkalinity of the concrete will be reduced after being carbonized, and the protective effect of the concrete on the steel bar will be weakened, even leading to corrosion of the steel bar. In this paper, fly ash is used to replace cement in the same amount, and basalt fiber and polypropylene fiber are added in a certain amount to make hybrid fiber fly ash concrete. Through rapid carbonation test, the influence of carbonation time and fly ash content on carbonation performance of hybrid fiber fly ash concrete is studied. The curve is fitted according to a single factor carbonation model with fly ash content as the main parameter, and the fitting curve and prediction formula are obtained. The results show that, in the same carbonization time, compared with the concrete without fly ash, the concrete with fly ash content of 5%, 10%, 20%, and 30% has average carbonization depth promotion rates of 6.4%, 14.9%, 59.8%, and 73.5%. When the fly ash content varies in the range of 10%∼20%, the carbonation resistance of hybrid fiber concrete changes most sensitively. At the same fly ash content, with the increase of carbonization time, the carbonization depth of concrete increases by 41.7%∼62.3%; Through the verification of the fitting curve and fitting formula obtained after fitting, it is concluded that the error of the prediction formula of carbonation depth of hybrid fiber fly ash concrete is within 9.1%, and the error of carbonation depth of 14 d and 28 d is within 4.3%. Replacing cement with fly ash has certain engineering significance and can achieve the purpose of recycling waste materials.

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