泵送混凝土回弹特性影响因素的研究

发布时间：2018-08-30 08:54

【摘要】：回弹法是现场混凝土质量检测最常用的一种无损检测方法,其通过回弹值及碳化深度两个指标推定混凝土抗压强度,使推定强度的误差精度保持在允许范围内。在回弹过程中,影响泵送混凝土回弹特性及误差的因素有很多,其中回弹仪能量、浇筑面及龄期对其影响比较大,对这三个方面的研究可以有效提高现场检测的精度,对推广回弹法在泵送混凝土板类构件及长龄期泵送混凝土中的应用具有重要的现实意义。试验直接接取搅拌站泵送混凝土制作成型,采用自然养护模拟实际工况,并对到达龄期的不同强度等级泵送混凝土及预留的长龄期泵送混凝土进行了回弹、抗压、碳化试验,通过对所测数据的分析,研究了不同能量回弹仪的回弹特性,给出了不同浇筑面的回弹值修正关系,并提出了几种提高长龄期泵送混凝土回弹检测精度的方法。研究结果表明:(1)随着能量的升高,回弹仪适用的泵送混凝土强度不断升高;2.207J回弹仪的适用范围为30~60MPa,4.5J回弹仪的适用范围为40~70MPa,5.5J回弹仪的适用范围为40~87.4MPa;低龄期时,强度增长是影响回弹值增长的主要因素,随着龄期的增长,碳化的影响逐渐增大;(2)泵送混凝土抗压强度的增长对浇筑顶面回弹值的影响最大;随着水胶比减小、龄期的升高,三个浇筑面的回弹值差距逐渐缩小;底面回弹值与浇筑侧面回弹值的相关性较好,可以进行回弹值修正增强推定准确度;(3)长龄期泵送混凝土回弹值的升高主要由碳化引起,即“碳化效应”对回弹值增长的影响大于抗压强度;长龄期泵送混凝土可以通过加深碳化修正深度、重新拟合以及系数修正地方曲线的方式提高回弹法的检测精度。
[Abstract]:Springback method is one of the most commonly used nondestructive testing methods in the field of concrete quality testing. The rebound value and carbonation depth are used to predict the compressive strength of concrete so that the error accuracy of the predicted strength is kept within the allowable range. In the springback process, there are many factors that affect the springback characteristics and error of pumping concrete, among which the energy, pouring surface and age of the springback meter have a great influence on it. The research on these three aspects can effectively improve the accuracy of field detection. It has important practical significance for popularizing springback method in pumping concrete slabs and long term pumping concrete. The concrete of mixing station was directly taken in the test to make the concrete, and natural curing was used to simulate the actual working conditions. The springback, compression and carbonization tests of the pumping concrete with different strength grades and the reserved long age pumping concrete were carried out. Based on the analysis of the measured data, the springback characteristics of different energy springback instruments are studied, and the relationship between the springback values of different pouring surfaces is given, and several methods to improve the precision of springback detection of pumping concrete with long age are put forward. The results are as follows: (1) with the increase of energy, the strength of pumping concrete used by the elastometer increases continuously. The suitable range of the resilience instrument is 30 ~ 60MPA ~ (4.5J). The range of application is 40 ~ (70) MPA ~ (5.5J) and the range is 40 ~ 87.4MPa at a young age, and the following results are obtained: (1) with the increase of energy, the range of application of the recoil is 2.207J. The increase of strength is the main factor affecting the increase of springback value. With the increase of age, the influence of carbonization increases gradually. (2) the increase of compressive strength of pumping concrete has the greatest effect on the springback value of the topping surface, and with the decrease of water-binder ratio, the age increases. The difference between springback value of three pouring surfaces was gradually narrowed, the correlation between the springback value of bottom surface and the springback value of pouring side was better, the springback value could be modified to enhance the presumption accuracy; (3) the increase of springback value of long-age pumping concrete was mainly caused by carbonization. That is, "carbonation effect" has more influence on the increase of rebound value than compressive strength, and the precision of springback detection can be improved by means of deepening carbonization correction depth, refitting and coefficient modifying local curve.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528.53

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