再生混凝土的力学性能及微观形貌分析

发布时间：2018-09-11 17:16

【摘要】：随着建筑业高速发展,建筑废弃物也急剧增加,将其中的废弃混凝土回收处理后作为再生骨料不仅能降低成本、解决城市建筑废弃物的堆放、占地和环境污染等问题,而且能实现混凝土工业的物质循环利用,保证建筑工业的可持续发展。但是,再生骨料相对于天然骨料而言,颗粒棱角多,表面粗糙,再加上废弃混凝土块在破碎过程中产生大量微裂缝,使得再生混凝土与天然混凝土的性能存在差异。因此,本文以试验研究为主,对再生混凝土的力学性能和微观形貌进行研究,开展的工作及得出的结论如下:1.保持水灰比0.55不变,改变再生骨料取代率来研究再生混凝土的工作性能和力学性能。再生骨料取代率分别为0、20%、30%、40%、50%、60%、70%、80%、100%。试验结果表明:随着再生骨料取代率增大,新拌混凝土流动性变差,粘聚性和保水性增强;当再生骨料取代率分别为20%、40%、50%、60%、70%、80%、100%时,再生混凝土的抗压强度比普通混凝土低;但当再生骨料取代率为30%时,再生混凝土的抗压强度较普通混凝土反而有所提高,建议再生骨料取代率控制在30%左右比较合理。2.在再生骨料取代率为100%的基础上,设计了三种水灰比,水灰比分别为0.5、0.55、0.6,对于每一种水灰比采用粉煤灰等量取代水泥10%、20%、30%来研究粉煤灰对再生混凝土工作性能和力学性能的影响。试验结果表明:再生混凝土的坍落度随着粉煤灰掺量的增加而增加,流动性增强,但混凝土粘聚性和保水性基本保持不变;再生混凝土抗压强度随粉煤灰掺量的增加而减小,当粉煤灰掺量为20%时,再生混凝土抗压强度降低最少。3.采用扫描电镜对再生混凝土微观形貌进行了研究。试验结果表明:在再生混凝土中掺入粉煤灰使水泥水化产物中的Ca(OH)2晶体颗粒细化,密实性得到提高;随着水灰比的减小,龄期的增加,水泥石结构孔隙减少,界面过渡区更加密实和均匀。
[Abstract]:With the rapid development of the construction industry, the construction waste is also increasing rapidly. Using the waste concrete as recycled aggregate can not only reduce the cost, but also solve the problems such as stacking of urban construction waste, occupation of land and environmental pollution, etc. Moreover, it can realize the material recycling of concrete industry and ensure the sustainable development of construction industry. However, compared with natural aggregate, recycled aggregate has many edges, rough surface and a large number of micro-cracks in the process of crushing of waste concrete, which makes the performance of recycled concrete and natural concrete different. Therefore, the mechanical properties and microscopic morphology of recycled concrete are studied in this paper, and the results are as follows: 1. The working and mechanical properties of recycled concrete were studied by changing the replacement ratio of recycled aggregate and keeping the water-cement ratio at 0.55. The replacement rate of regenerated aggregate is 0, 20, 30, 40, 50, 50, 60, 70, and 80, 80, 100. The experimental results show that with the increase of recycled aggregate substitution rate, the flowability of fresh concrete becomes worse, the cohesion and water retention increase, and the compressive strength of recycled concrete is lower than that of ordinary concrete when the replacement ratio of recycled aggregate is 20, 404050 and 50, respectively. But when the replacement ratio of recycled aggregate is 30, the compressive strength of recycled concrete is higher than that of ordinary concrete. It is suggested that the replacement rate of recycled aggregate should be controlled at 30% or so. On the basis of 100% replacement rate of recycled aggregate, three kinds of water-cement ratio are designed, the water-cement ratio is 0.550.65%, respectively. For each kind of water-cement ratio, fly ash is used to replace the cement with the equal amount of fly ash to study the influence of fly ash on the working performance and mechanical properties of recycled concrete. The test results show that the slump of recycled concrete increases with the increase of fly ash content, and the fluidity increases, but the cohesion and water retention of recycled concrete remain unchanged, and the compressive strength of recycled concrete decreases with the increase of fly ash content. When the content of fly ash is 20%, the compressive strength of recycled concrete decreases by a minimum of. 3. 3. The microstructure of recycled concrete was studied by scanning electron microscope (SEM). The experimental results show that adding fly ash into recycled concrete can refine the Ca (OH) _ 2 crystal particles and improve the compactness of cement hydration products, and with the decrease of water-cement ratio and the increase of age, the pore size of cement stone structure decreases. The transition zone of the interface is more dense and uniform.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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