回弹法检测高温喷水冷却后高强混凝土抗压强度试验研究

为研究高温喷水冷却后高强混凝土的回弹值与轴心抗压强度的相关性，以历经最高温度、恒温时间和混凝土强度等级为变化参数，共设计117 个混凝土棱柱体试件，先后进行回弹检测和轴压试验，分析各变化参数对回弹值和轴心抗压强度的影响规律，并基于规范和实测数据，对高温喷水冷却后混凝土强度与回弹值间关系进行公式拟合。研究结果表明：温度在400 ℃前，部分回弹值和抗压强度出现回升，600 ℃后二者下降明显；超600 ℃恒温1.0 h 试件的回弹值和抗压强度衰减最严重；在200 ℃和800 ℃时，混凝土强度等级对回弹值和抗压强度影响最显著；总体上，各变化参数改变对抗压强度影响更大；利用二次多项式拟合得到的公式计算值满足规范要求，能较准确地反映高温喷水冷却后混凝土回弹值与抗压强度的关系。

Experimental study on compressive strength of high-strength concrete after exposure to high temperature and water cooling by rebound method

In order to study the correlation between rebound value and axial compression performance of high- strength concrete after being exposed to high temperatures and water cooling,a total of 117 concrete prismatic blocks were designed for rebound detection and axial compression test with the highest temperature, constant temperature time, and concrete strength grade as parameters. The influence of various change parameters on the rebound value and the axial compressive strength were analyzed. The relationship of concrete strength and rebound value after exposure to high temperature and water cooling was fitted by formula based on the relevant specification and measured data. The results showed that: before 400 ℃ ,some rebound values and compressive strength increase, and after 600 ℃ , both of them drop sharply. When the temperature is constant for 1.0 h and the temperature exceeds 600 ℃ , the rebound value and compressive strength decay the most. At 200 ℃ and 800 ℃, the concrete strength grade has the most significant impact on the rebound value and compressive strength.In general, changes in various parameters have a greater impact on compressive strength. The calculated value of the formula obtained by the quadratic polynomial fitting meets the requirements of the specification, and can reflect the relationship between the rebound value and compressive strength after exposure to high temperatures and water cooling.