钢纤维轻骨料混凝土性能与叠浇梁受弯性能研究

发布时间：2018-05-11 09:42

本文选题：钢纤维轻骨料混凝土 + 拌合物性能　；参考：《郑州大学》2014年博士论文

【摘要】：轻骨料混凝土具有轻质、高强、抗震性能和耐久性能好等优点，越来越多地被应用于土木工程中。在轻骨料混凝土中掺入钢纤维配制的钢纤维轻骨料混凝土(简称SFRLC)，不仅具有轻骨料混凝土的各种优点，而且能显著提高轻骨料混凝土的抗拉、抗裂性能和韧性，改善混凝土结构的延性、抗疲劳性能和耐久性能。因此，开展钢纤维轻骨料混凝土材料与构件性能试验与理论研究具有重要的应用价值与理论意义。为充分利用钢纤维轻骨料混凝土和普通混凝土的优点，作者提出了一种新型结构形式：在下部一定高度的钢纤维轻骨料混凝土上同期现浇普通混凝土组成的叠浇梁。本文采用不同配合比方法进行钢纤维轻骨料混凝土配合比设计，，通过系列试验研究了不同参数对钢纤维轻骨料混凝土基本性能的影响，对所提出的新型钢纤维轻骨料混凝土叠浇梁（简称SFRLCB）开展了系统试验研究和理论分析，所完成的主要工作和取得的结论：（1）采用松散体积法对钢纤维机制砂轻混凝土和钢纤维全轻混凝土(简称SFRFLC)进行配合比设计，系统研究了水灰比、水泥用量、砂率及钢纤维体积率等参数对混凝土性能的影响。结果表明：机制砂轻混凝土的抗压强度及弹性模量、劈裂抗拉强度和轴心抗拉强度均随水灰比的增大而减小，但抗弯强度受水灰比的影响不明显；当水泥用量较高时，砂率对混凝土轴心抗拉强度和抗弯强度的影响较小；当水泥用量较低时，混凝土的轴心抗拉强度和抗弯强度受砂率和水泥用量的关联影响，砂率对混凝土劈裂抗拉强度的影响不明显。全轻混凝土的强度受砂率、水灰比及水泥用量的关联影响，其强度值主要取决于水泥砂浆及陶粒强度的强弱；存在使混凝土各强度指标达到最佳值的水泥用量、水灰比及砂率。掺加钢纤维显著增强了机制砂轻混凝土的劈裂抗拉强度和轴心抗拉强度，明显提高了全轻混凝土的抗弯强度。（2）采用考虑钢纤维裹浆厚度的直接设计方法进行高强钢纤维全轻混凝土配合比设计，系统研究了钢纤维体积率、水灰比、钢纤维裹浆厚度及砂率对高强钢纤维全轻混凝土性能的影响。结果表明：按考虑裹浆厚度的直接设计方法配制的高强钢纤维全轻混凝土，能满足拌合物工作性能、干表观密度和强度的要求。随着钢纤维体积率的增加，高强钢纤维全轻混凝土立方体抗压强度、轴心抗压强度和轴心抗拉强度均有所提高，劈裂抗拉强度显著提高。经综合分析，确定钢纤维全轻混凝土最佳钢纤维裹浆厚度为1.0mm。（3）对试验中采用不同配合比方法的钢纤维轻骨料混凝土的劈裂抗拉强度和轴心抗拉强度的关系进行了分析研究，结果表明：该类轻骨料混凝土劈裂抗拉强度与轴心抗拉强度的比值随轻骨料性质和钢纤维特征含量的变化而变化，建议轻骨料混凝土和钢纤维轻骨料混凝土抗拉强度采用轴心抗拉强度法测定。（4）考虑水泥用量、水灰比及钢纤维体积率变化，进行了钢纤维全轻混凝土抗冻性能试验研究。结果表明：钢纤维全轻混凝土的抗冻性能受水泥用量及水灰比的影响，掺入钢纤维可显著提高全轻混凝土的抗冻性能。与相对动弹性模量相比，抗弯强度损失率对冻融循环更为敏感。建议对承受弯曲作用为主的钢纤维轻骨料混凝土构件，采用抗弯强度损失率作为抗冻性能的1个评价指标。（5）系统进行了42根钢筋钢纤维全轻混凝土叠浇梁、12根钢筋混凝土梁和4根钢筋钢纤维全轻混凝土梁的受弯性能试验。结果表明：3类试验梁的破坏形态基本相似，均为适筋破坏；钢纤维掺量、叠浇高度对试验梁极限承载力具有较大影响，且变化规律与配筋率相关；纵筋配筋率显著影响试验梁的极限承载力，受压区混凝土强度等级对叠浇梁的极限承载力影响较小。根据理论分析和试验结果，建立了钢筋钢纤维全轻混凝土叠浇梁受弯承载力的计算模型和计算方法，提出了叠浇梁钢纤维全轻混凝土最小高度和最佳高度计算公式。（6）结合试验梁的研究成果，分析了钢纤维体积率、普通混凝土强度等级、纵向受拉钢筋配筋率和钢纤维全轻混凝土截面高度等参数对叠浇梁正截面抗裂弯矩的影响规律。结果表明：叠浇梁受压区混凝土与受拉区钢纤维全轻混凝土的截面高度存在较优值，受压区高强混凝土保障了叠浇梁正截面的较高抗裂弯矩；适当的纵向受拉钢筋配筋率有利于提高叠浇梁的正截面抗裂弯矩；钢纤维对叠浇梁正截面抗裂弯矩的提高与其对全轻混凝土抗拉强度的提高是一致的。结合理论计算分析，提出了钢筋钢纤维全轻混凝土叠浇梁正截面抗裂计算方法以及充分发挥钢纤维全轻混凝土抗拉能力的截面高度计算公式。（7）根据叠浇梁在正常使用荷载作用下的裂缝分布情况，明确了叠浇梁裂缝分类统计原则，进行了各类裂缝数量、平均裂缝间距、平均裂缝宽度及最大裂缝宽度分布规律的统计分析，建立了叠浇梁纵向受力钢筋重心水平位置处平均裂缝间距、平均裂缝宽度和最大裂缝宽度的计算模型和计算方法。
[Abstract]:Lightweight aggregate concrete has many advantages, such as light weight, high strength, good seismic performance and good durability. It is more and more used in civil engineering. Steel fiber lightweight aggregate concrete (SFRLC) mixed with steel fiber in lightweight aggregate concrete not only has various advantages of lightweight aggregate concrete, but also significantly improves lightweight aggregate concrete. Tensile, crack resistance and toughness improve the ductility, fatigue resistance and durability of concrete structures. Therefore, it is of great applied value and theoretical significance to carry out the performance test and theoretical study of steel fiber lightweight aggregate concrete materials and components. The author proposes to make full use of the advantages of steel fiber lightweight aggregate concrete and ordinary concrete. A new type of structural form: a superimposed cast-in-place beam of steel fiber lightweight aggregate concrete at a certain height at the lower level. The mix proportion of steel fiber lightweight aggregate concrete is designed by different mix ratio methods. The basic properties of steel fiber lightweight aggregate concrete are studied by a series of experiments. A new type of steel fiber reinforced concrete composite cast-in-place beam (SFRLCB) is carried out in a systematic test and theoretical analysis, and the main work and conclusions are achieved.
(1) the loose volume method is used to design the mix ratio of steel fiber reinforced lightweight concrete and steel fiber all light concrete (SFRFLC). The effects of water cement ratio, cement dosage, sand rate and steel fiber volume rate on the concrete performance are systematically studied. The results show that the compressive strength and modulus of elasticity of the machine made sand lightweight concrete, splitting resistance The tensile strength and the axial tensile strength decrease with the increase of water cement ratio, but the bending strength is not obviously influenced by the ratio of water to cement. When the cement content is high, the sand ratio has little effect on the tensile strength and bending strength of concrete axle center. When the cement dosage is low, the axial tensile strength and bending strength of the concrete are affected by the sand rate and cement. The effect of sand ratio on the splitting tensile strength of concrete is not obvious. The strength of all light concrete is influenced by the correlation of sand ratio, water cement ratio and cement content. The strength of the concrete mainly depends on the strength of cement mortar and the strength of the ceramsite, and the cement dosage, water cement ratio and sand ratio that make the concrete strength indexes reach the best value. The tensile strength and axial tensile strength of the machine-made sand lightweight concrete are significantly increased by adding steel fiber, and the flexural strength of all lightweight concrete is obviously improved.
(2) using the direct design method considering the thickness of steel fiber, the mix ratio design of high strength steel fiber full light concrete is designed. The effect of steel fiber volume rate, water cement ratio, thickness of steel fiber and sand ratio on the performance of high strength steel fiber lightweight concrete is systematically studied. The results show that the direct design method considering the thickness of the steel fiber is made up. The high strength steel fiber full light concrete can meet the requirements of the working performance of the mixture, the density and strength of the dry surface. With the increase of the steel fiber volume rate, the compressive strength of the high strength steel fiber full light concrete cube, the axial compressive strength and the axial tensile strength of the axle are improved, and the splitting tensile strength is greatly improved. The steel fiber is determined by comprehensive analysis. The best steel fiber wrapped thickness of all lightweight concrete is 1.0mm.
(3) the relationship between splitting tensile strength and axial tensile strength of steel fiber lightweight aggregate concrete with different mix ratio methods was analyzed. The results showed that the ratio of splitting tensile strength to axial tensile strength of this kind of lightweight aggregate concrete varies with the change of light aggregate quality and steel fiber characteristic content. The tensile strength of lightweight aggregate concrete and steel fiber reinforced lightweight aggregate concrete is determined by axial tensile strength method.
(4) considering the amount of cement, the ratio of water to cement and the change of the volume ratio of steel fiber, the frost resistance performance of the steel fiber full light concrete is studied. The results show that the frost resistance of the steel fiber full light concrete is affected by the cement dosage and the water cement ratio, and the frost resistance of the whole light concrete can be greatly improved by the addition of steel fiber. The flexural strength loss rate is more sensitive to the freezing and thawing cycle. It is suggested that the flexural strength loss rate is used as the 1 evaluation index for the frost resistance of the steel fiber lightweight aggregate concrete members.
(5) the flexural performance tests of 42 steel fiber reinforced steel fiber fully lightweight concrete beams, 12 reinforced concrete beams and 4 steel fiber full light concrete beams are carried out. The results show that the failure modes of the 3 type test beams are basically similar, all of which are suitable for reinforcement, and the steel fiber content and superposition height have great influence on the ultimate bearing capacity of the test beams. And the change rule is related to the reinforcement ratio; the longitudinal reinforcement ratio has a significant influence on the ultimate bearing capacity of the test beam, and the concrete strength grade of the compression zone has little influence on the ultimate bearing capacity of the superimposed beam. Based on the theoretical analysis and test results, the calculation model and calculation method of the bending bearing capacity of the steel fiber reinforced steel fiber full light concrete superposition beam are established. The formula for calculating the minimum height and optimum height of steel fiber reinforced lightweight concrete is presented.
(6) combining with the research results of the test beam, the influence of the steel fiber volume rate, the strength grade of the ordinary concrete, the reinforcement ratio of the longitudinal reinforced bar and the height of the steel fiber full light concrete section on the bending moment of the cross section beam is analyzed. The results show that the section of the concrete and the steel fiber full light concrete in the compression zone of the cast in place beam is cut. There is a better value in the height of the surface, and the high strength concrete in the compression zone ensures the high cracking bending moment of the cross section of the beam, and the proper reinforcement ratio of the longitudinal reinforced bar is beneficial to the improvement of the bending moment of the cross section of the beam, and the improvement of the crack resistance of the steel fiber to the cross section of the cast beam is consistent with the increase of the tensile strength of the full light concrete. On the basis of rational calculation and analysis, the calculation method for the crack resistance of steel fiber reinforced steel fiber full light concrete superposition beam and the calculation formula for full play of the tensile capacity of the steel fiber full light concrete are put forward.
(7) according to the distribution of the cracks under the normal use load of the superimposed beam, the classification statistics principle of the cracks of the superimposed beam is clarified, and the statistical analysis of the number of cracks, the average crack spacing, the average crack width and the distribution law of the maximum crack width is carried out, and the average crack between the horizontal position of the center of gravity of the longitudinal stress bar of the superimposed cast-in-place beam is established. The calculation model and calculation method of the average crack width and the maximum crack width are given.

【学位授予单位】：郑州大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU528.2;TU37

【参考文献】