表面设置防火涂料钢纤维混凝土高温后力学性能的研究

发布时间：2018-02-13 04:03

  本文关键词： 钢纤维混凝土 防火涂料 高温 力学性能 有限元模拟 SEM　出处：《湖南大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着社会经济的高速发展和城市化步伐的加快,都市变得高楼林立,人口开始过度集中,意外导致的火灾引起建筑物破坏和人员伤亡的现象时有发生。人们为了防止火灾隐患,通常会在公共建筑、隧道建筑等表面涂刷一层混凝土防火涂料。而设置有防火涂层和无防火涂层混凝土构件高温后的力学性能就会有很大不同。本文研究表面涂有一定厚度防火涂料的钢纤维混凝土高温力学性能。本文首先研究了目标温度、防火涂料厚度以及钢纤维掺量对钢纤维混凝土高温后力学性能的影响。然后利用有限元模拟了涂有防火涂料的混凝土在升温、恒温以及降温过程中的温度应力以及温度场的分布。最后运用电子扫描显微镜(SEM)观察了高温后钢纤维混凝土的微观结构,分析了混凝土内部结构的高温损伤以及钢纤维与混凝土基体的界面区随温度的变化规律。主要研究结果如下：(1)防火涂料在高温下会很好的隔离钢纤维混凝土,降低混凝土表面的温度,从而延缓和减轻混凝土结构的火灾损伤。在钢纤维混凝土表面涂上防火涂料,历经一定的高温条件后,其力学性能(抗压强度、劈裂抗拉强度、抗折强度)下降的风险大大降低,残余力学强度值增加。(2)在一定的高温作用下,随着防火涂层厚度的增加,钢纤维混凝土的抗压强度、劈裂抗拉强度、抗折强度均呈增加的趋势,其中800℃高温条件下,防火涂层的影响效果最为显著,随着防火涂料层厚度的增加,这种增强的效果开始削弱,钢纤维混凝土力学性能的增长开始变得缓慢。(3)当钢纤维混凝土表面带有一定厚度的防火涂料时,随着钢纤维掺量的增加,高温后混凝土力学性能降低的幅度均有所减小。目标高温条件一致时,钢纤维掺量越大,混凝土力学强度越大。(4) 在恒温阶段,随着恒温时间的增加,试件表面与试件中心温度的差值逐渐降低。并且恒温也减小了混凝土内外的应力差。在自然冷却降温阶段,混凝土的峰值应力先增大后降低,混凝土在降温阶段也有一定程度的高温损伤。随着防火涂料厚度的增加和钢纤维掺量的增加,试件表面和试件中心的温差均呈现降低的趋势。(5) 随着温度的升高,混凝土内部结构逐渐开始劣化,水化产物逐步分解,在800℃下,与普通混凝土相比,表面设置防火涂料的钢纤维混凝土基体的高温损伤程度降低,水泥石劣化程度较小。随着温度的升高,钢纤维与混凝土基体的界面区的水泥石逐渐变成粉末状,混凝土与钢纤维之间的粘结力降低。然而目标温度相同时,当混凝土表面涂有防火涂料,界面区水泥石的损伤程度大大降低,水泥石与钢纤维的粘结力较表面无防火涂料的钢纤维混凝土好。
[Abstract]:With the rapid development of social economy and the acceleration of urbanization, the city has become overcrowded, the population is beginning to be overconcentrated, and the accidental fire has caused the destruction of buildings and casualties from time to time. Usually in public buildings, A layer of concrete fire resistant coating is painted on the surface of tunnel buildings. The mechanical properties of concrete members with and without fire resistance coating will be very different after high temperature. This paper studies the surface coating with a certain thickness of fire resistant coating. The mechanical properties of steel fiber reinforced concrete (SFRC) at high temperature are studied in this paper. The effect of thickness of fire resistant coating and the amount of steel fiber on the mechanical properties of steel fiber concrete after high temperature. Then the finite element method is used to simulate the temperature rise of concrete coated with fire resistant coating. The distribution of temperature stress and temperature field in the process of constant temperature and cooling. Finally, the microstructure of steel fiber reinforced concrete (SFRC) after high temperature was observed by means of electron scanning microscope (SEM). The high temperature damage of concrete internal structure and the variation of interface zone between steel fiber and concrete matrix with temperature are analyzed. The main results are as follows: 1) Fiberproof coatings can isolate steel fiber reinforced concrete well at high temperature. Reduce the temperature of concrete surface, thus delay and reduce the fire damage of concrete structure. Apply fire resistant coating on the surface of steel fiber concrete, after a certain high temperature condition, its mechanical properties (compressive strength, splitting tensile strength, splitting tensile strength), The risk of decreasing the flexural strength is greatly reduced, and the residual mechanical strength is increased. At a certain high temperature, the compressive strength and splitting tensile strength of the steel fiber reinforced concrete increase with the increase of the thickness of the fire resistant coating. The flexural strength of the coating is increasing, especially at 800 鈩，

本文编号：1507278