含石粉机制砂再生混凝土受压性能研究及水化机理分析

发布时间：2018-04-30 01:38

本文选题：石灰石粉 + 机制砂　；参考：《广西大学》2017年硕士论文

【摘要】：机制砂再生混凝土作为一种新型环保绿色建筑材料,在实际投入生产前仍需对其材料性能进行大量的理论和试验研究。本文以试验为主,结合理论方法,针对含石粉机制砂再生混凝土的拉压强度、单轴受压应力-应变本构关系和水泥水化微观机理进行研究。在普通混凝土配合比公式的基础上,采取附加用水量的方法进行调整再生混凝土的配合比,试验配制相同水灰比(0.4)设计强度为35MPa,不同石粉含量(0%、5%、10%、15%)、不同再生粗骨料取代率(0%、33.3%、66.6%、100%)的机制砂再生混凝土。主要完成了以下工作:首先,本文对120个立方体试块进行混凝土立方体抗压和劈裂抗拉强度试验,分析石粉含量、再生粗骨料取代率对机制砂再生混凝土拉、压性能的影响,并建立立方体抗压强度和劈裂抗拉强度的换算关系。试验结果表明,机制砂再生混凝土中含有一定量的石粉对混凝土强度的提高起促进作用,建议的合理石粉含量为10%。机制砂再生混凝土的抗压和抗拉强度随着再生粗骨料取代率的增加先降低后提高,在再生粗骨料取代率为66.6%时达到最小值;随着再生粗骨料取代率继续增大至100%,其强度有所提高。根据试验建立的立方体抗压强度和劈裂抗拉强度的换算关系为:ft=0.175fcu0.75;较普通混凝土,在相同立方体抗压强度下,换算得到劈裂抗拉强度值较小。其次,完成了 60个棱柱体轴心受压试验,得到不同石粉含量、不同再生粗骨料取代率下的机制砂再生混凝土单轴受压应力-应变全曲线。结果表明,机制砂再生混凝土立方体抗压强度与轴心抗压强度的换算公式为:fc=0.818fcu;较普通混凝土,在相同立方体抗压强度下,换算得到轴心抗压强度值较大。机制砂再生混凝土单轴受压应力-应变全曲线与普通混凝土大致相同,根据曲线特点采用损伤力学理论分析机制砂再生混凝土的单轴受压破坏过程,建立机制砂再生混凝土单轴受压应力-应变损伤本构方程。最后,通过对混凝土各水化龄期试验样品进行X射线衍射物相分析(XRD)和扫描电镜观测(SEM),分析机制砂再生混凝土水化产物的种类及其微观形貌特征,揭示石粉对机制砂再生混凝土力学性能的影响机理,从微观的角度分析石粉对混凝土强度的影响。试验结果表明,石灰石粉微细骨料起填充、反应和晶核效应等作用,其中反应效应主要发生在水化过程的中后期;掺入石灰石粉微细骨料还对水化产物的形貌产生了影响。
[Abstract]:As a new environmental protection green building material, recycled concrete with machine-made sand still needs a lot of theoretical and experimental research before it is put into production. In this paper, the tensile strength, uniaxial compressive stress-strain constitutive relation and hydration micromechanism of recycled concrete with stone powder are studied in terms of tensile strength, uniaxial compressive stress-strain constitutive relation and cement hydration mechanism. On the basis of the formula of ordinary concrete mix ratio, the method of additional water consumption is adopted to adjust the mix ratio of recycled concrete. The design strength of the same water-cement ratio is 0.4) the design strength is 35 MPA, the content of different stone powder is 0 0 and 5%, and the replacement rate of different recycled coarse aggregate is 33.3% and 66.6% respectively). The main works are as follows: firstly, the concrete cube compressive and splitting tensile strength tests are carried out on 120 cube specimens, and the effects of stone powder content and recycled coarse aggregate replacement rate on the tensile and compressive properties of recycled concrete made of machine-made sand are analyzed. The conversion relationship between cube compressive strength and split tensile strength is established. The test results show that a certain amount of stone powder in recycled concrete with machine-made sand can promote the improvement of concrete strength, and the suggested reasonable stone powder content is 10. The compressive and tensile strength of recycled concrete with recycled sand decreases first and then increases with the increase of the replacement ratio of recycled coarse aggregate, and reaches the minimum value when the replacement rate of recycled coarse aggregate is 66.6. The strength of regenerated coarse aggregate increases with the ratio of replacement of recycled coarse aggregate to 100. The conversion relationship between the cube compressive strength and the splitting tensile strength established by the test is: (1) ftr 0.175 fcu0.75; compared with ordinary concrete, the value of splitting tensile strength is smaller than that of ordinary concrete under the same cube compressive strength. Secondly, the axial compression tests of 60 prisms have been completed, and the stress-strain curves of recycled concrete under uniaxial compression with different content of stone powder and different replacement rate of recycled coarse aggregate have been obtained. The results show that the conversion formula of cube compressive strength and axial compressive strength of recycled concrete with mechanism sand is: 1 / fc0. 818 fcu. compared with ordinary concrete, under the same cube compressive strength, the value of axial compressive strength can be obtained by conversion. The stress-strain curve of recycled concrete under uniaxial compression is approximately the same as that of ordinary concrete. According to the characteristics of the curve, the damage mechanics theory is used to analyze the uniaxial compressive failure process of recycled concrete with machine-made sand. The stress-strain damage constitutive equation of recycled concrete under uniaxial compression was established. Finally, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to observe the hydration products of recycled concrete from different hydration ages of concrete. The types and microscopic morphology of hydration products of recycled concrete with machine-made sand were analyzed. The influence mechanism of stone powder on the mechanical properties of recycled concrete made of machine-made sand is revealed, and the influence of stone powder on the strength of concrete is analyzed from the microscopic point of view. The results show that the effect of filling reaction and nucleation of limestone fine aggregate mainly occurs in the middle and late stage of hydration and the morphology of hydration product is also affected by the addition of limestone fine aggregate.
【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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