Carbonation Depth Model and Prediction of Hybrid Fiber Fly Ash Concrete

Abstract

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.

Effect of Equal Volume Replacement of Fine Aggregate with Fly Ash on Carbonation Resistance of Concrete

“…This is different from the previous concrete with fly ash instead of cement [32,33], and its carbonation depth often increases with an increase in the fly ash content; for fly ash concrete, the addition of fly ash reduces the amount of cement. Therefore, the content of carbonised materials such as Ca(OH) 2 and C-S-H gel can be reduced, and the content of Ca(OH) 2 is further reduced by the secondary hydration reaction [34,35]; thus, the ability of concrete to resist carbonation decreases. After replacing fine aggregate with fly ash, the amount of cement does not decrease in concrete, although the secondary hydration of fly ash reduces the content of carbonatable substances in CFA; however, fly ash exerts its microaggregate effect uniformly in the voids of aggregate particles [36,37].…”

Properties and Performance of Polypropylene Fiber Reinforced Concrete : A review

“…For hybrid fiber concrete of (PPF and basalt fiber), the carbonation renitence was most critically converted by (10%-20%) fly ash proportions incorporation as mentioned by [63], and at the same proportions, the concrete depth carbonization was modified by 41.7%-62.3% via carbonation time increment [62]. Wang et al…”

Development of hybrid machine learning-based carbonation models with weighting function

“…According to past publications, carbonation models can be classified into four categories based on how the relationship between carbonation depth and its influencing parameters is determined [1]: (1) empirical models, where the relationship between the carbonation depth and its determinants is derived from actual experiments [2][3][4][5][6][7][8][9], such as the square root model [3]; (2) statistical models, where the dependent and independent variables are related by mathematical functions, such as multiple linear regression [10]; (3) numerical models, which consider several physiochemical equations, including chemical reaction rates, mass conservation in gas-liquid two-phase flow, diffusion and dispersion of CO2 in water, energy conservation in porous media, and solubility of CO2 in water, and simulate the phenomena by computer software [11][12][13][14]; (4) machine learning (ML)-based models, which has been applied in recent simulations to find complex nonlinear relationships during the carbonation process [15][16][17][18]. However, all these models have their drawbacks.…”