含水率对混凝土强度影响初步研究

发布时间：2018-02-16 03:47

本文关键词： 抗压强度抗拉强度孔隙水压最大粒径损伤值　出处：《西北农林科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：混凝土强度与其含水量直接相关，并与其加载速率有关。该文混凝土试样浸泡在水中让其自由吸水，形成不同的含水量试样，采用不同的加载速率测试其强度，并采用超声波仪测定其波速，研究含水量对混凝土强度影响规律。另外，结合高坝混凝土在水中工作的环境，通过对混凝土标准试块外围施加高压水，形成渗透作用，重点研究孔隙水压、不同作用时间、不同最大骨料粒径对C15和C20等级混凝土的力学特性影响，，以揭示高渗透孔隙水在混凝土内渗透过程对混凝土强度的影响规律，得出以下结论：（1）混凝土含水量随着其浸泡时间的增加而逐渐递增，浸泡初期混凝土含水量增加迅速，而后逐渐放缓，并趋于稳定，稳定含水率在3.9%左右。混凝土试块浸泡后其超声波波速较浸泡前增大，超声波穿透混凝土试件横截面所需时间变短。当含水量低于3.5%时，超声波波速增加幅度不显著，当含水量超过3.5%时，超声波波速增加率明显增大。（2）相同含水量条件下，混凝土抗压强度随加载速率的增加出现先迅速增大后逐渐稳定现象；相同加载速率下，混凝土抗压强度随含水量增加而逐渐降低。当加载速率大于1.0MPa/s，混凝土抗压强度基本达到稳定。混凝土抗拉强度随加载速率变化趋势与其抗压强度基本相似。（3）在压力水作用下，随孔隙水压逐渐增大，混凝土抗压强度损伤值呈逐渐递增趋势。相同孔隙水压作用下，混凝土强度等级越低，其损伤值越大，最大粒径越大，其损伤值也越大。混凝土劈裂抗拉强度损伤值随着孔隙水压的增加呈递增趋势，且其抗拉强度损伤值受混凝土强度等级的影响，在相同的外围孔隙水压力作用下混凝土强度等级越高，其抗拉强度损伤值越小。
[Abstract]:The strength of concrete is directly related to its water content and its loading rate. The influence of water content on the strength of concrete is studied by using ultrasonic wave velocity. In addition, combined with the environment of high dam concrete working in water, high pressure water is applied to the outside of concrete standard test block to form permeation effect. The effects of pore water pressure, different acting time and different maximum aggregate particle size on the mechanical properties of C15 and C20 grade concrete are studied in order to reveal the influence of high permeability pore water on the strength of concrete. Draw the following conclusions:. 1) the water content of concrete increases gradually with the increase of soaking time, and the moisture content of concrete increases rapidly at the beginning of soaking, then slows down and tends to be stable. The steady moisture content is about 3.9%. The ultrasonic wave velocity of concrete specimen increases after soaking, and the time required for ultrasonic wave penetrating the cross section of concrete specimen becomes shorter. When the water content is lower than 3.5, the ultrasonic wave velocity increase is not significant. When the water content exceeds 3.5, the increase rate of ultrasonic wave velocity increases obviously. (2) under the same water content, the compressive strength of concrete increases rapidly first and then stabilizes with the increase of loading rate, while at the same loading rate, the compressive strength of concrete increases rapidly and then stabilizes gradually with the increase of loading rate. The compressive strength of concrete decreases gradually with the increase of water content. When the loading rate is more than 1.0 MPA / s, the compressive strength of concrete is basically stable, and the variation trend of concrete tensile strength with loading rate is basically similar to its compressive strength. 3) under the action of pressure-water, with the increase of pore water pressure, the damage value of concrete compressive strength increases gradually. Under the same pore water pressure, the lower the strength grade of concrete is, the greater the damage value is and the larger the maximum particle size is. With the increase of pore water pressure, the damage value of concrete splitting tensile strength is increased with the increase of pore water pressure, and the damage value of its tensile strength is affected by the strength grade of concrete. The higher the strength grade of concrete is under the same external pore water pressure, the smaller the damage value of tensile strength is.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU528

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