再生粗骨料混凝土的早期裂缝试验研究与数值模拟

发布时间：2018-06-11 13:17

本文选题：再生粗骨料 + 早期开裂　；参考：《宁夏大学》2017年硕士论文

【摘要】：粗骨料是制备混凝土必不可少的原材料,现有的天然砂石粗骨料已经难以维持混凝土粗骨料的可持续发展,因此必须要找到合适的天然粗骨料的替代品。整个地球每年都因旧建筑物、旧公路拆除而产生规模庞大的废弃混凝土,这些废弃混凝土又得不到有效的循环利用,因此研究再生混凝土的性能十分重要。这些废弃混凝土块经过机械破碎、分级后,按一定的替代率与相应的配合比可以制成再生粗骨料。现在研究的大都是再生粗骨料混凝土的力学性能,而关于再生粗骨料混凝土的早期开裂及钢纤维再生粗骨料混凝土早期开裂的研究是少之又少,同时试验的复杂性和高成本性又限制了再生混凝土的发展,有限元数值模拟作为一种数值分析方法,即方便直观又节省了试验成本。因此,本文的主要研究内容如下:(1)采用集中约束平板法,利用万能试验机及裂缝宽度观测仪测取试验数据,通过分析试验所得的数据,研究了再生粗骨料对天然粗骨料的不同替代率、钢纤维不同体积掺量对再生粗骨料混凝土 28天抗压强度和早期开裂性能的影响,主要得出以下结论:①随着再生粗骨料替代率的增加,再生混凝土的28d抗压强度、28d抗劈裂强度,均表现出先增大后减小的趋向,当替代率为60%时,抗压强度达到最大值;随着再生粗骨料替代率的增加,再生混凝土的24h水分蒸发速率、最大裂缝宽度、裂缝总面积先减少后增大。当再生粗骨料对天然骨料的替代率为60%时,再生粗骨料混凝土板的开裂程度最小。②钢纤维再生粗骨料混凝土板的28天抗压强度随着钢纤维体积掺量的增加,而先降低后增加;其24h水分蒸发速率、最大裂缝宽度、裂缝总面积则整体表现出先降低后升高的趋向。再生粗骨料混凝土板的28d抗劈裂强度随着钢纤维体积掺量的增加而增高。当钢纤维的体积掺量达到0.8%,钢纤维再生粗骨料混凝土板的早期开裂程度最小。(2)通过ANSYS完成有限元数值模拟,先选择Solid70单元进行热分析,热分析完成后,将Solid70单元转换为Solid45单元,读取热分析结果,进行结构分析,得到再生粗骨料混凝土板的温度应力。得到温度应力后,重新建立有限元模型,采用Solid65单元进行结构分析,从而得到钢纤维再生粗骨料混凝土早期开裂多少的情况。计算分析了钢纤维不同体积掺量对钢纤维再生混凝土板早期开裂的影响,数值模拟结果表明:钢纤维再生混凝土板的早期开裂基本发生在裂缝诱导器附近,随着钢纤维体积掺量的增加,模型板裂缝的数量先减少后增加。当钢纤维体积掺量达到0.8%,有限元模型板的早期开裂最少;当钢纤维的体积掺量为1.2%时,虽然模型板的裂缝没有沿裂缝诱导器分布,但是裂缝的数量最多。本文通过试验研究再生粗骨料混凝土和钢纤维再生粗骨料混凝土的早期开裂性能,通过ANSYS模拟钢纤维再生粗骨料混凝土的早期开裂,试验结果和数值模拟结果趋势比较接近,给再生粗骨料混凝土用于工程实际提供了支持。
[Abstract]:Coarse aggregate is an essential raw material for the preparation of concrete. The existing natural aggregate coarse aggregate is difficult to maintain the sustainable development of the coarse aggregate of concrete. Therefore, it is necessary to find a suitable substitute for natural coarse aggregate. The whole earth is dismantled from old buildings and old roads to produce large scale of waste concrete every year. Concrete can not be recycled effectively, so it is very important to study the performance of recycled concrete. After being mechanically broken, these concrete blocks can be made into recycled coarse aggregate according to a certain substitution rate and corresponding mix ratio. Most of the research is on the mechanical properties of recycled coarse aggregate concrete. The early cracking of aggregate concrete and the early cracking of steel fiber recycled coarse aggregate concrete are few. At the same time, the complexity and high cost of the experiment restrict the development of recycled concrete. The finite element numerical simulation is a numerical analysis method, which is convenient and intuitive and saves the cost of the test. Therefore, the main research of this paper is the main research of this paper. The contents are as follows: (1) using the centralized constrained flat plate method, using the universal test machine and the crack width observatory to measure the experimental data. Through the analysis of the data obtained from the experiment, the different substitution rate of recycled coarse aggregate to natural coarse aggregate and the 28 day compressive strength and early cracking performance of the recycled coarse aggregate concrete with different volume of steel fiber are studied. The main conclusions are as follows: (1) with the increase of the replacement rate of recycled coarse aggregate, the 28d compressive strength of recycled concrete and the splitting strength of 28d show a tendency to increase first and then decrease. When the substitution rate is 60%, the compressive strength reaches the maximum. With the increase of the replacement rate of recycled coarse aggregate, the 24h moisture evaporation rate of recycled concrete is increased. When the replacement ratio of recycled coarse aggregate to natural aggregate is 60%, the cracking degree of recycled coarse aggregate concrete slab is the smallest. (2) the 28 day compressive strength of steel fiber recycled coarse aggregate concrete slab increases with the volume of steel fiber volume, and then increases first, and the water evaporation rate of 24h The maximum crack width and the total area of the crack show a tendency to decrease first and then increase. The 28d splitting strength of recycled coarse aggregate concrete plate increases with the increase of the volume of steel fiber. When the volume of steel fiber is 0.8%, the early cracking degree of the steel fiber recycled coarse aggregate concrete slab is the smallest. (2) complete through the completion of the steel fiber reinforced concrete slab. The finite element numerical simulation, first select the Solid70 unit for thermal analysis, after the thermal analysis is completed, the Solid70 unit is converted to Solid45 unit, the thermal analysis results are read, and the thermal stress of the recycled coarse aggregate concrete slab is obtained. After the thermal stress is obtained, the finite element model is rebuilt, and the structure analysis is carried out by the Solid65 element. The early cracking of steel fiber recycled coarse aggregate concrete was obtained. The effect of different volume of steel fiber on the early cracking of steel fiber recycled concrete slab was calculated and analyzed. The results of numerical simulation showed that the early cracking of the steel fiber recycled concrete slab was basically near the crack inducer, with the volume of steel fiber volume added. When the volume of steel fiber volume reaches 0.8%, the early cracking of the finite element model plate is the least. When the volume of steel fiber is 1.2%, the cracks in the model plate are not distributed along the crack inducer, but the number of the cracks is the most. The early cracking performance of steel fiber recycled coarse aggregate concrete was simulated by ANSYS to simulate the early cracking of steel fiber regenerated coarse aggregate concrete. The trend of experimental results and numerical simulation results was close, and it provided support for regenerated coarse aggregate concrete used in engineering practice.
【学位授予单位】：宁夏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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