再生骨料混凝土拉伸徐变影响因素试验研究

发布时间：2019-01-07 22:24

【摘要】：当前由废弃混凝土产生的一系列环境、资源问题越来越突出,将废弃混凝土经加工后作为再生骨料进行再次利用成为解决这些问题的重要方法,对保护环境、节约资源,从而促进社会可持续发展有着重要的作用。目前对再生骨料混凝土拉伸徐变特性的研究还鲜见报道,由于再生粗骨料与天然粗骨料的差别很有可能导致再生骨料混凝土拉伸徐变性能与普通混凝土存在较大差异。因此,本文通过研究再生粗骨料取代率、粉煤灰取代率、粉煤灰加矿渣复掺取代率对再生骨料混凝土拉伸徐变的影响,以期加深对再生骨料混凝土拉伸徐变影响因素的了解,从而推广再生骨料混凝土的运用。本文主要完成的工作如下：1.再生粗骨料的物理力学性能试验表明,表面附着的大量旧砂浆导致再生粗骨料与天然粗骨料相比存在着密度低、空隙率大、吸水率及压碎指标高的特点。2.通过再生骨料混凝土基本力学性能试验,研究70%再生粗骨料取代率、粉煤灰取代率、粉煤灰加矿渣复掺取代率对再生骨料混凝土基本力学性能的影响。试验结果表明,再生粗骨料取代70%天然粗骨料会导致再生骨料混凝土基本力学性能不同程度的下降；掺粉煤灰会导致再生骨料混凝土基本力学性能不同程度下降,且再生骨料混凝土基本力学性能随粉煤灰掺量的增加而降低;粉煤灰加矿渣复掺也会导致再生骨料混凝土基本力学性能不同程度的降低,且复掺量越大其基本力学性能降低越多,但其降低幅度低于总掺量相同的掺粉煤灰组。3.通过再生骨料混凝土单轴拉伸徐变试验,研究70%再生粗骨料取代率、粉煤灰取代率、粉煤灰加矿渣复掺取代率对再生骨料混凝土拉伸徐变性能的影响。试验结果表明,再生粗骨料取代70%天然粗骨料会导致再生骨料混凝土拉伸徐变增大；掺粉煤灰会导致再生骨料混凝土拉伸徐变增大,且拉伸徐变随粉煤灰掺量的增加而增加；粉煤灰加矿渣复掺也会引起再生骨料混凝土拉伸徐变的增大,且拉伸徐变随复掺量的增加而增大,但其增大幅度明显低于总掺量相同的掺粉煤灰组。4.将再生骨料混凝土拉伸徐变试验结果与目前国内外的几种混凝上徐变预测模型进行对比,发现常用的徐变预测模型不适用于再生骨料混凝土的拉伸总徐变预测,而经拟合确定参数后的M-Burgers模型则能对若干试验组的拉伸基本徐变有较好的预测。选取M-Burgers模型为参考模型,在该模型的基础上结合本试验引入适当参数考虑粗骨料取代率、矿物掺和料的影响,建立了适合于再生骨料混凝土的拉伸基本徐变预测模型。
[Abstract]:At present, a series of environmental problems caused by waste concrete are becoming more and more prominent. Using waste concrete as recycled aggregate after processing becomes an important method to solve these problems, which can protect the environment and save resources. So as to promote the sustainable development of society has an important role. At present, there are few reports on tensile creep properties of recycled aggregate concrete. Due to the difference between recycled coarse aggregate and natural coarse aggregate, the tensile creep behavior of recycled aggregate concrete may be different from that of ordinary concrete. Therefore, in this paper, the influence of the replacement rate of recycled coarse aggregate and the replacement rate of fly ash and slag on tensile creep of recycled aggregate concrete is studied in order to deepen the understanding of the factors affecting the tensile creep of recycled aggregate concrete. Thus the application of recycled aggregate concrete is popularized. The main work of this paper is as follows: 1. The physical and mechanical properties of recycled coarse aggregate show that a large amount of old mortar attached on the surface leads to the characteristics of low density, large porosity, high water absorption and crushing index compared with natural coarse aggregate. 2. The effects of 70% recycled coarse aggregate replacement ratio and fly ash plus slag replacement ratio on the basic mechanical properties of recycled aggregate concrete were studied through the test of the basic mechanical properties of recycled aggregate concrete. The test results show that the recycled coarse aggregate can replace 70% natural coarse aggregate, which will lead to the decrease of the basic mechanical properties of recycled aggregate concrete in varying degrees. The basic mechanical properties of recycled aggregate concrete decrease with the increase of fly ash content. The addition of fly ash and slag can also reduce the basic mechanical properties of recycled aggregate concrete to different degrees, and the more the content of fly ash is, the lower the basic mechanical properties of recycled aggregate concrete are, but the decrease range is lower than that of fly ash group with the same amount of fly ash. Through uniaxial tensile creep test of recycled aggregate concrete, the effects of 70% recycled coarse aggregate replacement ratio and fly ash and slag co-substitution ratio on tensile creep properties of recycled aggregate concrete were studied. The experimental results show that the tensile creep of recycled aggregate concrete increases with the replacement of 70% natural coarse aggregate with recycled coarse aggregate, and the tensile creep increases with the increase of fly ash content, and the tensile creep of recycled aggregate concrete increases with the addition of fly ash. The addition of fly ash and slag can also increase the tensile creep of recycled aggregate concrete, and the tensile creep increases with the addition of fly ash, but the increase range is obviously lower than that of fly ash group with the same total content. 4. The results of tensile creep test of recycled aggregate concrete are compared with several kinds of creep prediction models at home and abroad. It is found that the commonly used creep prediction model is not suitable for the total tensile creep prediction of recycled aggregate concrete. The M-Burgers model can predict the basic creep of some test groups. The M-Burgers model is selected as the reference model, and based on the model, a basic creep prediction model suitable for recycled aggregate concrete is established by introducing appropriate parameters to consider the influence of coarse aggregate substitution ratio and mineral admixture.
【学位授予单位】：福州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU528

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