机制砂再生混凝土微观结构及二轴应力状态下受压力学性能研究

发布时间：2018-05-09 20:49

本文选题：机制砂 + 再生混凝土　；参考：《广西大学》2017年硕士论文

【摘要】：由于天然砂具有短期内不可再生的性质,混凝土用砂寻求可替代资源是不可避免的趋势,机制砂也就成为最佳的选择。另一方面,日益增多的废弃混凝土也将成为城市的一大公害。将机制砂与再生粗骨料有机结合在一起配制成机制砂再生混凝土不仅能解决天然资源的匮乏问题,对环境保护也起到积极的作用,符合可持续发展的科学理念。本文总共制作了 190个不同石粉含量(0%5%、10%、15%)和不同再生粗骨料取代率(0%、33%、66%、100%)的C35标准立方体混凝土试块,分别对其微观结构、劈裂抗拉强度、单轴及二轴受压应力状态下的力学性能进行研究。主要研究工作如下:一、对不同石粉含量以及不同再生粗骨料取代率的机制砂再生混凝土进行劈裂抗拉试验。结果表明机制砂再生混凝土最优石粉含量为10%;低石粉含量(0%、5%)的情况下,再生粗骨料取代率为100%时,机制砂混凝土劈裂抗拉强度最低,而高石粉含量(10%、15%)的机制砂再生混凝土及天然砂再生混凝土劈裂抗拉强度在再生粗骨料取代率为66%时最低。二、通过扫描电镜对机制砂再生混凝土微观结构进行研究。分析结果表明石粉可以促进水泥水化反应,而且石粉含量的多少影响水化产物的数量以及晶体形态。当石粉含量为10%时,混凝土达到最佳堆积密实状态,水化产物能很好的填充混凝土内部孔洞,骨料砂浆紧密粘结,因此力学性能最好。同时石粉具有填充的作用,使砂浆更加密实。对界面过渡区进行对比分析,机制砂再生混凝土三个界面过渡区强度大小排序为旧骨料与旧砂浆界面过渡区新旧砂浆界面过渡区新骨料新砂浆界面过渡区。三、对机制砂再生混凝土进行单轴及双轴受压力学性能试验,观测分析了其破坏过程以及破坏形态。单轴压状态下的混凝土破坏形态为柱状破坏,双轴压状态下的破坏形态基本为层片状劈裂破坏,只是由于应变比的不同及采用的骨料不同导致破坏时裂缝的倾斜角度以及层片状破坏的细密程度有所差异。四、二轴受压应力状态下的机制砂再生混凝土强度整体上比单轴应力状态下抗压强度高,但是提高倍数略有差别,提高值在1.051～2.142倍之间。二轴压应力状态下最大强度与采用的骨料类型与应变比有关,采用天然砂作为细骨料的混凝土,其最大值均出现在应变比为0.5,而对于机制砂普通混凝土与不含石粉机制砂再生混凝土二轴压应力状态下的最大强度出现在应变比为0.25,含石粉机制砂再生混凝土二轴压应力状态下在应变比1.0时出现最大强度。石粉对机制砂再生混凝土二轴压强度也有提高作用,但是提高效应不是很明显。机制砂再生混凝土主轴峰值应变随着应变比的增大整体呈先增大后减小的趋势,水平轴峰值应变整体上随着应变比的增大而增大。五、二轴压应力状态下各混凝土的应力-应变全曲线都包含四部分,分别为:混凝土内部被压实阶段、线性上升段、裂缝开展阶段、下降段。各阶段所占比例以及破坏剧烈程度与石粉含量、骨料类型有关。在最佳石粉含量范围内石粉含量越少,再生粗骨料取代率越多,机制砂再生混凝土呈脆性破坏越严重。六、根据实测应力-应变曲线特点建立了机制砂再生混凝土二轴受压应力状态下主轴受压应力-应变全曲线表达,其结果与试验数据吻合良好;同时参考过镇海破坏准则公式,建立了机制砂再生混凝土实用的破坏准则。
[Abstract]:As natural sand is not renewable in the short term, it is inevitable that it is an inevitable trend to seek alternative resources for concrete sand, and the mechanism sand will be the best choice. On the other hand, the increasing number of waste concrete will also become a major public hazard in the city. The organic sand is organically combined with recycled coarse aggregate to form a mechanism sand. The raw concrete can not only solve the shortage of natural resources, but also play a positive role in environmental protection. It is in line with the scientific concept of sustainable development. In this paper, 190 C35 standard cubic concrete blocks with different content of stone powder (0%5%, 10%, 15%) and different recycled coarse aggregate (0%, 33%, 66%, 100%) are made in this paper. The structure, splitting tensile strength, the mechanical properties of the uniaxial and two axial compression stress states are studied. The main research work is as follows: first, the splitting tensile test of the mechanism sand recycled concrete with different stone powder content and the replacement rate of recycled coarse aggregate shows that the optimum stone powder content of the machined sand recycled concrete is 10%; the low stone powder is low. Under the condition of content (0%, 5%), when the replacement rate of recycled coarse aggregate is 100%, the splitting tensile strength of mechanism sand concrete is the lowest, while the splitting tensile strength of the mechanism sand recycled concrete and natural sand recycled concrete with high stone powder content (10%, 15%) is the lowest when the replacement rate of recycled coarse aggregate is 66%. Two, through scanning electron microscope, the mechanism sand recycled concrete micro The results show that the stone powder can promote the hydration of cement, and the amount of the stone powder affects the quantity of the hydration products and the crystal form. When the stone powder content is 10%, the concrete can reach the best packing state. The hydration products can fill the inner hole of the coagulant soil well, and the aggregate mortar is tightly bonded. Therefore, the aggregate mortar is tightly bonded. The mechanical properties are the best. At the same time, the stone powder has the effect of filling, making the mortar more dense. Comparison and analysis of the interface transition zone, the strength of the three interface transition zones of the mechanism sand recycled concrete is sorted as the transition zone of the new mortar interface in the transition zone of the old mortar interface and the old mortar interface. Three, the regeneration of the mechanism sand The failure process and failure form of concrete were observed and analyzed by uniaxial and biaxial compression behavior tests. The failure form of concrete under single axial compression was columnar failure. The failure form under double axial pressure was basically lamellar split fracture, only due to the difference of strain ratio and the difference of the aggregate used to cause breakage crack. Four, the compressive strength of the machined sand recycled concrete under the stress state of the two axis is higher than that under the state of uniaxial stress, but the increase is slightly different, and the increase value is between 1.051 and 2.142 times. The maximum strength and the bone used under the two axis stress state. The material type is related to the strain ratio. The maximum value of the concrete with natural sand as fine aggregate appears at the strain ratio of 0.5, while the maximum strength for the two axis compressive stress state of the mechanism sand ordinary concrete and the non stone powder mechanism sand recycled concrete appears at the strain ratio of 0.25 and the two axis compressive stress of the sand regenerated concrete containing the stone powder mechanism. The maximum strength of the strain ratio is 1 at the strain ratio. The stone powder also improves the two axial compressive strength of the machined sand recycled concrete, but the effect is not obvious. The peak strain of the main shaft of the mechanism sand recycled concrete increases first and then decreases with the increase of the strain ratio, and the peak strain of the horizontal axis increases with the strain ratio as a whole. The stress strain curve of each concrete under the condition of five, two axis compressive stress contains four parts, which are the internal compaction stage, the linear rising stage, the crack development stage, the descending section. The proportion of each stage and the severity of the damage are related to the stone powder content and the aggregate type. The less the content is, the more the replacement rate of the recycled coarse aggregate is, the more brittle fracture of the machine-made sand recycled concrete is more serious. Six, according to the characteristics of the measured stress strain curve, the full curve of the compressive stress strain of the spindle under compressive stress state of the mechanism sand recycled concrete under the stress state of the two axis is established, and the result is in good agreement with the experimental data, and at the same time it has been referred to the destruction of the sea. A practical failure criterion for recycled aggregate concrete is established.

【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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