为探讨赤泥的再生利用问题,利用碱激发原理开展了碱激发赤泥胶凝材料研究.设计了不同碱激发材料和配合比,进行了碱激发胶凝材料宏观性能和微观机理研究,在此基础上,进行了碱激发赤泥稳定建筑垃圾集料的道路基层材料性能试验.结果表明:碱激发赤泥形成了新的化合物,水玻璃激发赤泥的强度高于石灰激发赤泥的强度,但前者干缩率较大,石灰稳定赤泥具有较好的综合性能.选择合适的配合比,以石灰赤泥为胶结料稳定废旧混凝土类建筑垃圾骨料制备的道路基层材料,可满足各级公路道路基层的强度要求.
为了解决再生混凝土在复杂环境条件下的耐久性能研究匮乏问题,对5种再生混凝土进行碳化、干湿与冻融耦合作用下的耐久性试验,测试其动弹性模量、氯离子迁移系数、碳化深度及微观孔隙特征参数,并引入孔隙迂曲度指标进行分析.结果表明:交替碳化与干湿对再生混凝土的冻融劣化效果有显著促进作用,累计碳化42 d与干湿循环42次可使再生混凝土冻融损伤量增加21.9％ ～26.9％,抗氯离子渗透性能降低45.05％ ～96.18％;与单一碳化42 d相比,交替干湿循环42次与冻融循环300次可使再生混凝土的碳化深度增加1.6～3.5倍.此外,碳化、干湿作用均增大孔隙迂曲度,而冻融及三因素耦合作用均减小孔隙迂曲度;孔隙迂曲度与氯离子迁移系数及相对动弹性模量均具有显著的相关性,在一定程度上可作为再生混凝土耐久性能评价指标.
为探究赤泥回收利用方法,以烧结法赤泥为活性材料,不同模数的水玻璃溶液为激发剂,制备了赤泥基碱激发胶凝材料,测试了其力学性能及孔结构特征,并通过XRD、SEM及差热分析探究了其微观机理.试验表明,水玻璃模数对材料性能有较大影响,水玻璃模数为0.96时体系的激发效果最好,28 d抗压强度达到10.21MPa.硬化试件的主要强度来源物质为水化硅酸钙凝胶,强度较高的材料其微观结构更为致密,碱激发产物数量更多.
The effect of different aggregate treatment methods on the properties of both the recycled aggregate and the recycled concrete was studied. In this work, the compressive strength, dynamic elastic modulus, dry shrinkage rate, and chloride ion migration coefficient for five types of recycled concretes were investigated. Moreover, the Vickers hardness index and micro-morphology of new and old interfaces were analyzed. The results showed that "carbonation" significantly improved the mechanical properties and the dry shrinkage resistance of the recycled concrete. However, "slurry wrapping" greatly enhanced the chloride ion penetration resistance. Different aggregate treatment methods had different mechanisms to strengthen the interface. The influence of "carbonation" on the old interfacial zones (ITZ) was more significant than that on the new ITZ. A contrary influence of the "slurry wrapping" on both old and new ITZs was observed. The old interface had an obvious effect on the compressive strength and dynamic elastic modulus, while the new interface with different treatments had a non-negligible influence on the chloride penetration resistance. Besides, in this study, two optimization methods were proposed based on the improvement of "carbonation" and "slurry wrapping" treatment, respectively. These optimized methods can further improve the quality of recycled aggregate and the performance of recycled concrete. (C) 2019 Elsevier Ltd. All rights reserved.
