Mechanical and frost resistance properties of high air content hydraulic concrete

摘要

The frost resistance of hydraulic concrete is evaluated under -17 degrees C freezing temperature according to the Chinese standards. However, the freezing-thawing condition is usually less than -17 degrees C because of the broad distribution of water conservancy project in China. Therefore, the freezing-thawing cycle experiment of high frost resistance design level concrete with air content above 5.5% was conducted, and -17, -30 and -40 degrees C freezing temperatures were adopted during the test. The mechanics and frost resistance properties of hydraulic concrete after freezing-thawing cycles were studied. Also, the microscopic characteristic of hydraulic concrete after freezing-thawing cycles was observed by using environmental scanning electron microscope. The test results indicated that the lower was the freezing temperature in the centre of concrete specimen, the greater was performance deterioration. The freezing-thawing cycles had significant impact on the microstructure of concrete. The number of internal micro fractures and the width of micro fractures increased after freezing-thawing cycles.