基于结晶劈裂作用的再生粗骨料冻融改性方法

A Freezing-Thawing Modification Method for Recycled Coarse Aggregate Based on Crystallization Fracture of Pores

关键词:  再生粗骨料  冻融改性  结晶劈裂  孔隙介质力学  细观模拟

Key words:  recycled coarse aggregate  freezing-thawing modification  crystallization fracture  poromechanics  mesoscale modeling

摘要:

利用多孔水泥基材料在冻融循环中的孔隙水结晶劈裂原理，开展了不同工况下再生粗骨料的冻融改性试验，以部分或全部去除再生粗骨料表面附着的旧砂浆.结果表明：冻融最低温度越低，附着砂浆的剥除速率越快；经过一定次数的冻融循环后，附着砂浆几乎全部剥离，且改性后的再生粗骨料各项物理力学性能接近天然骨料；高温干燥预处理对后续冻融改性有较好的促进作用.最后，基于孔隙水相变的热力学原理以及冻胀开裂的孔隙介质力学机理，对再生粗骨料的冻融改性进行了理论分析，构建了再生粗骨料细观模型，从细观尺度解释了附着砂浆冻胀开裂及剥离的全过程.

Abstract:

Based on the crystallization fracture principle of ice forms in porous cement-based materials and initiates cracking during freezing-thawing cycles， freezing-thawing modification experiments of recycled coarse aggregate under different working conditions were carried out to remove part or all of the attached old mortar. The results show that the lower of the minimum freezing-thawing temperature is， the faster of the peeling of the attached mortar is. After a certain number of freezing-thawing cycles， the attached mortar is almost completely peeled off. Besides， the physical and mechanical properties of the modified recycled coarse aggregate are close to those of natural aggregate. In addition， the high temperature drying treatment before freezing-thawing cycles improves the efficiency of the method. Finally， based on thermodynamics and poromechanics principles， the process of freezing and cracking to remove the attached mortar is analyzed and simulated in a mesoscopic model.