复合胶凝材硬化浆体孔隙特征与其水化后钙矾石含量相互关系的试验研究

发布时间：2018-09-01 05:54

【摘要】：随着混凝土胶凝材中收缩裂缝和延迟钙矾石的致裂影响导致的工程渗漏水问题不断突显,常规修补措施难以及时地发现和解决这些微裂缝。因此,论文以胶凝基材为研究对象,以硅粉、粉煤灰和矿粉作为主要掺和料,采用压汞法和低场核磁共振法对不同龄期下复合胶凝材硬化浆体的孔隙特征进行测试,通过Rietveld全谱拟合定量分析水化产物中钙矾石的含量变化,初步研究了复合胶凝材硬化浆体的孔隙特征与钙矾石含量的相互关系,并结合对应的抗折抗压强度,选出了孔隙特征和强度更优的胶凝材配合比。通过胶凝基材改性研究控制微观孔隙的产生和发展,为自修复混凝土的研究奠定了试验基础,并得出以下结论:(1)在适当的掺量下,复合胶凝材硬化浆体的抗折、抗压强度比纯水泥高;多掺和料复合胶凝材硬化浆体的强度总体上比同龄期的单掺和料复合胶凝材的强度低;复合胶凝材硬化浆体的强度与孔隙率基本成反比趋势。(2)压汞法测出复合胶凝材硬化浆体的孔隙主要分布在3.5nm～1OOnm的范围内,最可几孔径随龄期增加总体向小孔径移动,且前期减小快,后期变化慢;而低场核磁共振法测得的孔隙分布范围大多在1nm～300nm之间,最可几孔径在7d龄期后几乎保持不变。(3)不同配合比复合胶凝材硬化浆体的平均孔径和孔隙率均随着龄期的增加而不断减小,且前期减小快,后期变化慢;随着某一掺和料掺量的增加,平均孔径总体减小;多掺和料复合胶凝材在适当的掺量下,比单掺时更明显地降低了硬化浆体的孔隙率、平均孔径和最可几孔径。(4)不同配合比的复合胶凝材料水化产物中的钙矾石含量主要分布在0～3%的范围内,对应的孔隙率则集中分布在15%～30%之间,平均孔径集中分布在14nm～30nm之间。(5)综合考虑抗折抗压强度、平均孔径和孔隙率的测试结果,确定了单一掺和料时复合胶凝材的最优掺量范围:硅粉6%左右,粉煤灰4%～8%之间,矿粉12%左右。多掺和料复合胶凝材的优化掺量范围:硅粉6%左右,粉煤灰7.5%以下,矿粉4%～8%左右,水泥80%左右。
[Abstract]:With the problems of engineering leakage caused by shrinkage cracks and delayed ettringite cracking in concrete cementitious materials, it is difficult to find and solve these microcracks in time by conventional repair measures. Therefore, taking the cementing base material as the research object, taking silica powder, fly ash and mineral powder as the main admixture, the pore characteristics of the composite cemented paste at different ages were measured by mercury injection method and low field nuclear magnetic resonance method. The change of ettringite content in hydration products was quantitatively analyzed by Rietveld full-spectrum fitting. The relationship between pore characteristics and ettringite content of hardened paste of composite cementing material was studied preliminarily, and the corresponding flexural compressive strength was combined with the relationship between the pore characteristics and the content of ettringite. The best mix ratio of gelling material with better pore characteristics and strength was selected. The formation and development of micro-pores are controlled by the modification research of cementing base material, which lays an experimental foundation for the study of self-repairing concrete, and draws the following conclusions: (1) the bending resistance of the composite cement hardened paste is obtained under the appropriate dosage. The compressive strength is higher than that of pure cement, the strength of multi-admixture composite cementing paste is lower than that of mono-admixture compound cementing material of the same age, and the strength of multi-admixture composite cementing material is lower than that of single-admixture composite cementing material of the same age. The strength and porosity of composite cemented paste are inversely proportional to each other. (2) the porosity of composite cemented paste is mainly distributed in the range of 3.5nm~1OOnm by mercury injection method, and the most suitable pore size moves to small pore size with increasing age. The pore distribution range measured by low field nuclear magnetic resonance (LFS) is between 1nm~300nm, and the change is slow in the later stage, but the pore distribution range measured by low field nuclear magnetic resonance method is mostly between 1nm~300nm. (3) the average pore size and porosity of the composite cementing paste with different mix ratio decreased with the increase of age, and decreased rapidly in the early stage and slow in the later stage; (3) the maximum pore size remained almost unchanged after 7 days of age. (3) the average pore size and porosity of the composite cementing paste with different mix ratio decreased with the increase of age. With the increase of a certain amount of admixture, the average pore size decreases generally, and the porosity of hardened paste decreases more obviously when the amount of multi-admixture compound cementing material is suitable than that of single admixture, and the average pore size decreases with the increase of the amount of admixture, and the average pore size decreases with the increase of the amount of admixture. (4) the content of ettringite in the hydration products of the composite cementitious materials with different mix ratios is mainly distributed in the range of 0 ~ 3%, and the corresponding porosity is concentrated in the range of 15% and 30%. The average pore size is concentrated between 14nm~30nm. (5) considering the test results of flexural compressive strength, average pore size and porosity, the optimum dosage range of composite cementing material is determined: silica fume is about 6%, fly ash is between 4% and 8%. Ore powder is about 12%. The optimum dosage range of multi-admixture compound cementing material is about 6% of silica powder, 7.5% of fly ash, 4% of mineral powder and 80% of cement.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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