再生粗骨料混凝土抗冻性能研究进展

Research Progress on Frost Resistance Property of Recycled Coarse Aggregate Concrete

将再生粗骨料应用于混凝土制备可有效减少原材料生产对生态环境的破坏,还可实现建筑废弃物的再生利用。但由于存在老旧砂浆包裹、原始缺陷较多等问题,再生粗骨料混凝土吸水率较高且薄弱界面较多,抗冻性能较差,对寒冷环境下的混凝土结构产生了极为不利的影响。本文综合分析国内外对再生粗骨料混凝土抗冻性能的研究现状,发现复杂脆弱的界面过渡区是再生粗骨料混凝土承受冻害时的薄弱环节,微裂缝和孔隙的发育使其在冻融循环过程中的性能不断降低。再生混凝土的抗冻性能随着再生粗骨料掺量的增加而加速劣化,再生粗骨料质量掺量应控制在50%以内。质量损失、相对动弹性模量和抗压强度是评价再生混凝土冻融损伤水平的常用指标,质量损失在试验初期会出现负增长情况,相对动弹性模量在有限冻融循环次数下的反应较不敏感,相比之下抗压强度能更好地体现再生粗骨料混凝土的冻融损伤水平。未来,还应对再生混凝土冻融损伤机理进行更加系统深入的研究,探究效果良好的非破坏性试验指标,以及在标准冻融试验的基础上结合特定工程环境对再生混凝土抗冻性能进行具体评价,推动再生粗骨料混凝土更加广泛的应用。

The application of recycled coarse aggregate in the field of concrete production effectively reduces environmental pollution,and realizes building waste recycling.However,due to the inherent defects such as surface wrapping by existing mortar and initial imperfection,recycled coarse aggregate concrete(RCAC)has a relatively high water absorption rate and inferior interface bond which will lead to poor frost resistance of RCAC structures exposed to subzero environment.Based on the review of both domestic and overseas researches for frost resistance of RCAC,it is found that the interfacial transition zone in freezing RCAC presents complexly vulnerable character.The development of micro-crack and pores causes the deterioration of RCAC under the freeze-thaw cycles.The growth of recycled coarse aggregate replacement percentage accelerates the degradation of frost resistance,and the mass content of recycled coarse aggregate should be controlled within 50%for optimum consideration.Mass loss,relative dynamic elastic modulus and compressive strength are usual parameters for damage level evaluation of recycled concrete.The mass loss shows negative growth at the initial stage of test,and the relative dynamic elastic modulus is less sensitive under limited freeze-thaw cycles.By contrast,the compressive strength better reflects the freeze-thaw damage level of RCAC.In the future,it is necessary to pay more attention on more systematic and in-depth research into the freeze-thaw damage mechanism of recycled concrete,and to explore reasonable non-destructive test indices that work well,as well as specific evaluation of the frost resistance behavior of recycled concrete for specific engineering environments based on standard freeze-thaw tests,in order to promote more widespread use of RCAC.