Pressure Bleeding Rate and Crack Resistance of High-Strength Concrete with Good Fluidity

Abstract

Abstract In order to explore the factors affecting the pressure bleeding rate of high-strength concrete with good fluidity and its performance, the variation of the pressure bleeding rate of high-strength concrete with good fluidity and its crack resistance were studied from the aspects of the quantity of admixtures and mineral admixture, water–cement ratio, unit water consumption, and sand ratio. Furthermore, the corresponding bleeding improvement measures and appropriate mix ratio were proposed for better performance of concrete. The test results show the following: (1) the concrete with the pebbles of the largest particle size and poor gradation in the coarse aggregate has a higher pressure bleeding rate than the concrete with the crushed stones of a smaller largest particle size and good gradation; (2) the more the fine aggregate and the smaller the fineness modulus, the lower the pressure bleeding rate of concrete; (3) with the increase in the quantity of superplasticizer, the pressure bleeding rate will increase: when the quantity is greater than 1.2 %, the concrete will produce serious bleeding; (4) adding fly ash and silicon ash can effectively reduce the pressure bleeding rate: the quantity of the fly ash should not exceed 25 % and the optimum quantity of silica fume ranges from 5 % to 10 %; (5) under other conditions unchanged, the pressure bleeding rate increases with the increase of water–cement ratio and unit water consumption; and (6) when the sand ratio is in the range of 38 % to 44 %, the pressure bleeding rate decreases as the sand ratio increases. Based on those tests for bleeding rate and slab cracking, the mix ratio of C60 high-strength concrete with good fluidity could be optimized. The high-strength concrete with good fluidity can simplify civil engineering construction and improve civil engineering concrete durability and recycling of industrial wastes. So, it is a green building material with excellent performance.