高温后再生保温混凝土损伤劣化数值分析

Numerical Analysis of Damage and Deterioration of Recycled Aggregate Concrete Mixed with Glazed Hollow Beads after High Temperature

【目的】内部多孔且高温稳定的玻化微珠(glazed hollow beads,GHB)可在一定程度上减缓混凝土的高温损伤劣化,提升混凝土的抗火性能。为了进一步明确GHB改善混凝土抗火性能的机理,从细观尺度出发,提出一种可考虑初始缺陷和再生骨料(recycled coarse aggregate,RCA)取代率的再生保温混凝土(recycled aggregate concrete mixed with glazed hollow beads,RATIC)细观模型的建模方法。【方法】利用现阶段比较常用的塑性损伤模型,探究了RCA取代率(0,50%,100%)、GHB含量(0,70%,100%)和孔隙率(0,2%,4%)对于高温后RATIC力学性能的影响。【结果】结果表明:随着受火温度的提高,荷载作用下RATIC试件的损伤分布均呈现出逐渐加剧的趋势,且500℃后,试件的损伤分布较400℃之前严重。GHB的加入可在一定程度上缓减混凝土内部的损伤劣化,而RCA的加入会加剧此现象。此外,随着孔隙率增大,RATIC试件的强度逐渐变低。

【Purposes】 The internally porous and highly thermally stable glazed hollow beads(GHB) can reduce the high temperature damage and deterioration of concrete to a certain extent,and improve the fire resistance of concrete.In order to further clarify the mechanism of GHB in improving the fire resistance of concrete,starting from the meso-scale concrete,we proposed a modeling method for RATIC meso-scale model that can take into account the initial defects and the replacement rate of recycled coarse aggregate(RCA).【Methods】 The effects of RCA replacement rates(0,50%,100%),GHB contents(0,70%,100%),and porosity(0,2%,4%) on the mechanical properties of RATIC after high temperature were explored by utilizing the plastic damage model commonly used at curent stage.【Findings】 The results show that with the increase of fire temperature,the damage distributions of the RATIC specimens under load exhibit a gradually increasing trend,and the damage distribution of the specimens after 500 ℃ is more serious than that before 400 ℃.The addition of GHB alleviates the damage and deterioration inside the concrete to a certain extent,while the addition of RCA exacerbates this phenomenon.In addition,the strength of RATIC specimens gradually decreases with the increase of porosity.