Application Research On Gypsum Paste Used As Standard Paste In The Compressive Strength Test Of Wall Bricks

At present, the wall material industry developed quickly, mainly included the three types, which were wall bricks, building blocks, and panels, in which the wall bricks had a large portion in industry. In original standard, the compressive strength of wall bricks used the way of artificial leveling with cement paste, leading the results of low efficiency due to the limit of the long curing age. To solve this problem, gypsum paste was used as the leveling material, which would enhance the efficiency of test and currency of test results, promoting the progress of wall bricks measurement technique in our country.Firstly, the method of comparative study was used. Cement paste in original standard and gypsum paste were used to the compressive strength measurement in the same strength level, different types of bricks(fired common brick, fired hollow brick and fired perforate brick), and different producing area(more than ten cities in China). The compressive strength of cement paste leveled at 3 days and gypsum paste leveled at 4 hours were compared, to explore the possibility of substitution of cement by gypsum. Secondly, the elementary composition of gypsum and sand in gypsum paste, the compressive strength of gypsum and crystal structure, the content of silica in sand, the fluidity of gypsum paste, initial setting time and compressive strength were tested. Lastly, the statistical methods of F-test, coefficient of skew, Kurtosis coefficient method, Gaussian distribution and Dixon guidelines were used to processing data and analyze the uniformity of gypsum paste.The results showed that:(1) The gypsum paste as a leveling material which substituted cement paste had no negative effect on the compressive strength results of wall bricks. Furthermore, the curing time of gypsum paste was only 4 hours while the cement paste was 3 days, largely shortened the measurement period and enhanced the testing efficiency.(2) All technical parameters of gypsum paste were meet the requirements of experiment.(3) The results of statistics showed smaller states dispersion and more currently results, indicating that the accuracy of compressive strength of wall bricks were guaranteed by gypsum paste.