冻融-碳化耦合作用下矿渣-粉煤灰再生混凝土试验研究

通过在含有100%再生粗骨料的混凝土中同时掺入20%的矿渣和0%,15%,30%掺量的粉煤灰,并进行碳化、冻融和冻融-碳化耦合试验,研究冻融和碳化环境对再生混凝土耐久性的影响,对比分析试件抗压强度、质量损失率、相对动弹性模量、碳化深度的变化规律,建立冻融-碳化耦合作用下矿渣-粉煤灰再生混凝土抗压强度模型。结果表明:粉煤灰掺量为15%时,再生混凝土的抗冻性能最好,当冻融次数大于100次后,粉煤灰对再生混凝土抗冻性能的促进作用开始减弱;粉煤灰掺量越多,再生混凝土的抗碳化性能越弱,当粉煤灰掺量为30%时,其碳化深度是粉煤灰掺量为0试件的2倍以上;在冻融-碳化耦合环境中,冻融作用促进了碳化深度的增长,碳化作用加剧了矿渣-粉煤灰再生混凝土的冻融破坏;建立的矿渣-粉煤灰再生混凝土冻融-碳化耦合抗压强度模型能较好地反应冻融-碳化耦合环境下的抗压强度退化规律。

Experimental study on slag-fly ash recycled concrete under the action of freeze-thaw-carbonation coupling

In order to research the durability of recycled concrete mixed with slag-fly ash in the freeze-thaw and carbonation environment,20%slag and 0%,15%,30%fly ash were simultaneously blended in the recycled concrete containing 100%recycled coarse aggregate,and carbonation,freeze-thaw and freeze-thaw-carbonation coupling test were carried out.The degradation law of specimen compressive strength,mass loss rate,relative dynamic elastic modulus and carbonation depth changes was analyzed.The compressive strength model of slag-fly ash recycled concrete under the action of freeze-thawcarbonation coupling was established.The results show that the frost resistance of recycled concrete is best,when the content of fly ash is 15%in recycled concrete,at the same time,the promoting effect of fly ash on the frost resistance of recycled concrete begins to weaken,when the freeze-thaw cycles are more than 100 times.The more fly ash content,the weaker the anti-carbonization performance of recycled concrete,and the carbonization depth is twice as much as that of recycled concrete without fly ash when the fly ash content is 30%.In the regenerated coarse aggregate coupling compressive strength environment,the freeze-thaw effect promotes the growth of carbonation depth,and the carbonization accelerates the freeze-thaw damage of slag-fly ash recycled concrete.The established slag-fly ash recycled concrete freeze-thaw-carbonization coupling compressive strength model can better reflect the degradation law of compressive strength under the freeze-thaw-carbonization coupling environment.