自密实轻骨料混凝土的力学性能研究

发布时间：2018-04-13 23:32

本文选题：自密实轻骨料混凝土 + 高温　；参考：《大连理工大学》2014年博士论文

【摘要】：自密实轻骨料混凝土是基于自密实混凝土和轻骨料混凝土而发展起来的新型混凝土,具有自重轻、可自填充密实、浇筑无需振捣等优点。作为一种新型的建筑材料,自密实轻骨料混凝土的高温性能、粘结滑移性能和断裂性能目前还没有深入的研究。本文通过对自密实轻骨料混凝土试件的高温试验、侧向力用作用下的拉拔试验以及三点弯曲梁断裂试验,研究了自密实轻骨料混凝土高温性能、与变形钢筋的粘结滑移性能和断裂性能。主要的研究内容和结论如下： (1)对强度等级为C40和C50的自密实轻骨料混凝土进行高温试验,研究高温下自密实轻骨料混凝土的爆裂性能,探索自密实轻骨料混凝土的爆裂原因,对比了自密实轻骨料混凝土高温前后的质量损失、超声波速以及残余力学性能,研究自密实轻骨料混凝土在高温下的损伤程度以及力学性能,对比了同强度等级的普通混凝土、轻骨料混凝土和自密实混凝土的高温性能。研究结果表明,由于轻骨料吸湿性强以及自密实轻骨料混凝土的密实性,自密实轻骨料混凝土在高温下易发生爆裂,但未爆裂前自密实轻骨料混凝土的残余强度比普通混凝土较高,显示出在保持强度稳定方面的优越性。 (2)根据自密实轻骨料混凝土的爆裂结果分析,在自密实轻骨料混凝土中加入了聚丙烯纤维,以提高自密实轻骨料的高温性能。结果表明,聚丙烯纤维减小了自密实轻骨料混凝土的爆裂,提高了混凝土残余力学性能,是一种提高自密实轻骨料混凝土高温性能的有效方法。 (3)研究了自密实轻骨料混凝土和变形钢筋在侧向压力作用下的粘结滑移性能,研究了侧压力大小和方向、混凝土强度、混凝土保护层厚度和钢筋直径比值、轻骨料类型等对自密实轻骨料混凝土和变形钢筋粘结滑移性能的影响。通过对69组自密实轻骨料混凝土的拉拔试件的试验研究表明,随着侧向压力增大,自密实轻骨料混凝土和变形钢筋的粘结破坏模式逐渐由劈裂破坏向拔出破坏转变,粘结强度的变化均和破坏模式和侧压力作用方式有关。在单侧压下,复合型劈裂-拔出破坏试件的粘结强度总体随侧压力增大而增大,拔出破坏试件的粘结强度和侧压力无关。在双侧压作用下,复合型劈裂-拔出破坏和拔出破坏下,粘结强度均随着侧压力的增大而增大。根据试验结果,回归了粘结强度、最大粘结应力对应的滑移量以及残余强度和粘结强度的比值等相关参数与侧压力的关系,公式计算结果和试验结果吻合良好。 (4)提出了适用于自密实轻骨料混凝土和变形钢筋的粘结滑移数学模型,合理预测了在复杂应力状态下自密实轻骨料混凝土和变形钢筋的粘结滑移曲线,并与试验结果吻合良好。 (5)基于粘聚力模型,提出了求解自密实轻骨料混凝土Ⅰ型断裂KR阻力曲线的解析方法。根据裂缝扩展准则,当外力引起的应力强度因子和粘聚力引起的应力强度因子之差达到起裂断裂韧度时,裂缝开始扩展,据此计算了初始裂缝高比和尺寸不同的八组三点弯曲梁的荷载-张开口位移,并和试验结果吻合良好,验证了该准则的正确性。因此,根据裂缝扩展准则,混凝土的KR既可以表示为起裂断裂韧度和粘聚力引起的应力强度因子之和,也可以表示为外力引起的应力强度因子。在此基础上计算了不同缝高比的自密实轻骨料混凝土三点弯曲梁的KR阻力曲线以及断裂过程区长度。结果表明,KR阻力曲线和初始缝高比无关,自密实轻骨料混凝土的断裂过程区长度随裂缝扩展先增大,在达到完整断裂区后逐渐减小。此外,KR阻力曲线对混凝土的软化曲线形状不敏感,即软化曲线的形状对计算结果并没有明显影响。
[Abstract]:Self compacting lightweight aggregate concrete is a new type of concrete self compacting concrete and lightweight aggregate concrete is developed based on, has the advantages of light weight, self filling, pouring without vibration and other advantages. As a kind of new building material, high temperature of self compacting lightweight aggregate concrete, the performance of bond slip properties and fracture at no further research. This paper through high temperature test specimens of self compacting lightweight aggregate concrete, test and pullout test under three point bending fracture of lateral force, high temperature of self compacting lightweight aggregate concrete and deformed bar and the bond slip properties and fracture properties. The main research contents and conclusions are as follows:
(1) of self compacting lightweight aggregate concrete for high temperature test of strength grade of C40 and C50, burst properties of self compacting lightweight aggregate concrete of high temperature, explore the bursting reason of self compacting lightweight aggregate concrete, compared the mass loss of self compacting lightweight aggregate concrete before and after high temperature, ultrasonic velocity and residual mechanical properties of self the damage degree of compacting lightweight aggregate concrete under high temperature and mechanical properties, compared to ordinary concrete with the same strength grade, lightweight aggregate concrete and self compacting concrete high temperature performance. The results of the study show that, due to the strong absorption of lightweight aggregate and self compacting lightweight aggregate concrete compactness, self compacting lightweight aggregate concrete under high temperature burst burst, but not before the residual strength of self compacting lightweight aggregate concrete is higher than ordinary concrete, showing strength in keeping stable superiority.
(2) according to the analysis of self compacting lightweight aggregate concrete crack results in self compacting lightweight aggregate concrete with polypropylene fiber, in order to improve the high temperature performance of self compacting lightweight aggregate. The results show that the polypropylene fiber reduces self compacting lightweight aggregate concrete crack and improve the residual mechanical properties of concrete, is an effective way to improve the the performance of self compacting lightweight aggregate concrete at high temperature.
(3) the study of self compacting lightweight aggregate concrete bond slip properties and deformation of reinforced under lateral pressure, the lateral pressure magnitude and direction, concrete strength, thickness and diameter of reinforcement ratio of concrete protective effect of lightweight aggregate type of self compacting lightweight aggregate concrete and deformation performance of reinforced bond slip. Through the experiment on 69 groups of self compacting lightweight aggregate concrete pull-out specimens show that with lateral pressure increases, the adhesion of self compacting lightweight aggregate concrete and deformed bar failure mode gradually from splitting failure to pullout failure change, change of bond strength and related failure modes and lateral pressure in unilateral way. Under pressure, the composite bond strength overall split split - pullout specimens with lateral pressure increases, pull-out bond strength and lateral pressure of damaged specimens. In the role of bilateral pressure, composite Split - pullout failure and pullout failure, bond strength both increase with lateral pressure. According to the test results, the regression relationship between slip and bond strength, residual strength and bond strength of the related parameters and the lateral pressure ratio of the maximum bond stress corresponding to the formula calculation results and test results good agreement.
(4) a mathematical model of bond slip for self compacting lightweight aggregate concrete and deformed steel bar is put forward, and the bond slip curves of self compacting lightweight aggregate concrete and deformed steel bar under complex stress condition are reasonably predicted, which is in good agreement with the experimental results.
(5) the cohesion model based on analytic method is proposed for solving the self compacting lightweight aggregate concrete fracture type KR resistance curve. According to the crack propagation criterion, when the external force caused by the stress intensity factor and the cohesion of the stress intensity factor caused by the difference between the fracture toughness, the cracks began to expand, calculated the initial crack size ratio and eight different groups of three point bending beam load - opening displacement, and in good agreement with the experimental results, verifies the correctness of the criteria. Therefore, according to the concrete crack propagation criterion, the KR can be expressed as the fracture toughness and cohesive force caused by the stress intensity factor and also, can be expressed as the external cause of the stress intensity factor. On the basis of calculation of different crack depth ratio of self compacting lightweight aggregate concrete three point bending beam KR resistance curve and fracture process zone length. The results show that the resistance of KR Force curve and initial crack depth ratio is independent of the length of fracture process zone of self compacting lightweight aggregate concrete increases with the crack expansion, decreased gradually in the fracture zone to complete. In addition, the KR resistance curve of concrete softening curves is not sensitive to the shape of the softening curve has no obvious effect on the results.

【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU528

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