盐冻环境下CO2养护生物炭再生混凝土的损伤规律与寿命预测OA

To enhance the durability of recycled concrete in cold saline-alkaline regions,this study focused on C30 recycled concrete with five biochar incorporation levels(0%,2.0%,4.0%,6.0%,and 8.0%,mass fraction).Two curing methods,standard curing and CO2 curing,were applied.Sulfate freeze-thaw cycle tests were conducted to measure macroscopic indicators including mass loss rate,relative dynamic elastic modulus,and compressive strength loss rate.Microscopic pore structure analysis was performed using nuclear magnetic resonance(NMR)technology.A damage model based on the Weibull distribution was established to predict service life of concrete under salt freezing environment.The results show that biochar significantly improves the salt-freeze resistance of recycled concrete,with an optimal incorporation rate being 4.0%.After 300 freeze-thaw cycles under standard curing,the mass loss rate,relative dynamic elastic modulus,and compressive strength loss rate of the 4.0%biochar group improve by 46.8%,58.0%,and 22.7%,respectively,compared with the reference group.CO2 curing further enhances the performance,reducing the mass loss rate and compressive strength loss rate by 36.8%and 33.1%,respectively,compared with the standard-cured group at the same biochar content.The porous adsorption characteristics of biochar,combined with the densification effect of CO2 curing through carbonation,synergistically optimize the pore structure and reduce the proportion of harmful pores.The damage model based on the Weibull distribution exhibits a good fit and predicte that the service life of the optimal combination(4.0%biochar with CO2 curing)in North China could reach 9 288 d,which is 175.4%longer than that of the reference group.The study confirms that the synergistic effect of biochar and CO2 curing produces a"1+1>2"enhancement effect on the salt-freeze resistance of recycled concrete,significantly extending its service life in cold saline-alkaline environments.