【作者】 王玥；

【导师】 闫滨；

【作者基本信息】 沈阳农业大学 ， 水利工程， 2018， 硕士

【摘要】 多孔混凝土是一种自身具有贯通孔隙的混凝土,因其透水性和透气性而被称为“会呼吸的混凝土”,为环境带来良好的生态效应,是保持生态良性循环的的重要基础之一。多孔混凝土是由连通孔隙和实体部分组成的多孔结构,具有高孔隙率、低强度的特点。在多孔混凝土中掺入适量硅灰可有效提高其强度,但现有研究成果主要集中在多孔混凝土抗压强度、抗折强度和抗冻性等宏观性能,对于其本构关系、微观结构的研究甚少。因此,本文主要针对掺硅灰多孔混凝土本构关系及微观结构进行研究。本构方面,参考过镇海教授提出的本构模型,并调用MATLAB软件中的nlinfit函数进行非线性最小二乘法拟合,对掺硅灰多孔混凝土的本构关系进行拟合;微观方面,采用扫描电镜及X射线能谱仪对掺硅灰多孔混凝土的内部微观结构进行观察。本文取得的主要研究成果如下:(1)研究多孔混凝土的配合比设计、制备工艺及其主要的物理力学性能。多孔混凝土的设计孔隙率与有效孔隙率接近,数值相差均在1%以内,说明绝对体积法能有效控制多孔混凝土的孔隙率;然而平面孔隙率与有效孔隙率相差略大,说明还受到成型工艺的影响;掺硅灰多孔混凝土的有效孔隙率与渗透系数之间存在良好的正比例关系,但与抗压强度基本成反比例关系,并据此分别得出对应关系式和相关系数。(2)通过对12组配合比(36个尺寸为100×100×300mm~3)的多孔混凝土试件进行单轴受压试验,从而拟合出掺硅灰多孔混凝土的本构关系。根据试验所得到应力—应变曲线的特点,提出含有参数a和b的多孔混凝土的本构关系式;然后得到不同设计孔隙率的多孔混凝土在不同硅灰掺量下的本构参数a和b值;最后将拟合所得的曲线与试验结果相比较,拟合结果较好。(3)通过观察水泥石和界面过渡区的微观形貌,进一步分析硅灰的作用机理及不同掺量对水泥水化反的影响。得出当硅灰掺量小于10%时,在硅灰微粒填充效应和火山灰效应的综合作用下,试件内部裂缝和孔隙减小,微观结构的密实度显著提高,又由于硅灰可消弱粗骨料表面水膜作用,使得ITZ厚度减薄;但当硅灰掺量超过10%后,过量硅灰产生团簇现象,使得水泥浆体结构不均匀,对强度造成不良影响。更多还原

【Abstract】 Porous concrete is a kind of concrete with perforated pores.Because of its permeability and permeability,it is called"breathing concrete",which brings good ecological effect to the environment and is one of the important bases for maintaining a benign cycle of ecological environment.It has the characteristics of high porosity and low strength.Adding appropriate amount of silica fume to porous concrete can effectively improve its strength,but the existing research results mainly focus on the macroscopic properties such as compressive strength,flexural strength and frost resistance of porous concrete,and little research on its constitutive relation and microstructure.Therefore,the constitutive relationship and microstructure of silica fume reinforced porous concrete are studied in this paper.With reference to the constitutive model proposed by Zhenhai Professor,and using the nlinfit function in MATLAB software to fit the nonlinear least square method,the constitutive relation of porous concrete mixed with silica fume is fitted.In the microcosmic aspect,the internal microstructure of porous concrete mixed with silica fume is introduced by scanning electron microscope and X ray energy spectrometer.The main results obtained in this paper are as follows:(1)The mix design,preparation process and main physical and mechanical properties of porous concrete are studied.The design porosity of the porous concrete is close to the effective porosity,and the difference of the numerical value is within 1%.It shows that the absolute volume method can effectively control the porosity of the porous concrete.However,the plane porosity is slightly different from the effective porosity.There is a good positive proportional relationship between the effective porosity and the permeability coefficient,but it is basically in inverse proportion to the compressive strength,and the corresponding relation and correlation coefficient are obtained respectively.(2)The constitutive relationship of porous concrete mixed with silica fume is fitted through the uniaxial compression test of 12 groups of porous concrete specimens with 36sizes of 100×100×300mm~3.According to the characteristics of stress strain curve obtained by the test,the constitutive relation of porous concrete containing parameters a and B is proposed,and the constitutive parameters a and B of porous concrete with different design porosity under different silica fume content are obtained.Finally,the fitting results are compared with the test results,and the fitting results are better.(3)The action mechanism of silica fume and the effect on the hydration reaction of cement are further analyzed by observing the microstructure of cement stone and ITZ.It is concluded that when the amount of silica fume is less than 10%,under the silica fume filling effect and the volcanic ash effect,the cracks and pores in the specimen are reduced,and the microstructural density is greatly improved.Because the silica fume can weaken the water film on the surface of coarse aggregate,the thickness of the interface transition zone is thinner.But when the amount of silica fume is more than 10%,excessive silica fume produces clusters,which makes the structure of cement paste uneven and has a bad effect on the strength.更多还原