矿物掺合料对再生混凝土抗冻性与可再生性的影响

Effects of Mineral Admixtures on Frost Resistance and Renewability of Recycled Aggregate Concrete

为探究矿物掺合料对再生混凝土抗冻性与可再生性的影响,本文选取硅灰、粉煤灰和粒化高炉矿渣三种矿物掺和料,通过不同掺量组合制备了五组不同胶凝体系的再生混凝土。采用快冻法对再生混凝土进行冻融试验,通过测定冻融过程中再生混凝土的相对动弹性模量、质量损失率和抗压强度损失率评价其抗冻性,采用SEM观察冻融后再生混凝土的微观结构。此外,对冻融后的再生混凝土进行破碎,获得二代再生粗骨料,并依据其表观密度、压碎值、坚固值和吸水率评估再生混凝土的可再生性。结果表明:5%(质量分数,下同)硅灰+20%粉煤灰+20%矿渣+55%水泥组合的质量损失率和抗压强度损失率明显比单掺5%硅灰以及5%硅灰+20%粉煤灰和5%硅灰+20%矿渣组合的低,且相对动弹性模量比其他组合的高。四种不同胶凝体系的二代再生粗骨料物理性能均达Ⅲ类标准,可用于强度等级为C25的结构混凝土的制备。

In order to explore the effects of mineral admixtures on frost resistance and renewability of recycled concrete,three kinds of mineral admixtures,such as silica fume fly ash,fly ash silica fume and granulated blast furnace slag,were selected.Five groups of recycled aggregate concrete with different cementitious systems were prepared by different dosage combinations.The freeze-thaw test of recycled aggregate concrete was carried out by rapid freezing method.By measuring the relative dynamic elastic modulus,mass loss rate and compressive strength loss rate of recycled aggregate concrete during the freeze-thaw process,the frost resistance of recycled aggregate concrete with different cementitious systems was evaluated.The microstructure of recycled aggregate concrete after freeze-thaw cycle was observed by SEM.In addition,the recycled aggregate concrete after freeze-thaw cycle was crushed to obtain the second generation of recycled coarse aggregate,and the renewability of recycled aggregate concrete was evaluated according to its apparent density,crushing value,firmness value and water absorption.The results show that the mass loss rate and compressive strength loss rate of combination of 5%(mass fraction,the same below)silica fume+20%fly ash+20%slag+55%cement are significantly lower than those of combination of 5%silica fume,5%silica fume+20%fly ash and 5%silica fume+20%slag,and the relative dynamic elastic modulus is also higher than that of other combinations.The second generation of recycled coarse aggregates of four combinations all meet the gradeⅢaggregate standard,which can be reused for structural concrete with strength grade of C25.