Study For Sulfate Attack Resistance Of Manufactured Sand Concrete

The natural sand which is a kind of non-renewable resource in a short time is facing trend of growing shortage. So the manufactured sand will inevitably be widely used in engineering construction. The manufactured sand has many characteristics, such as the surface is coarseness, more edges, more microcracks and large porosity, poor graduation, which will result in bad influence to the performance of concrete especially durable performance. Sulfate attack which is an important content of durability of concrete has been widely concerned at home and abroad all the time. At present there is little research on sulfate attack of manufactured sand concrete, so in this paper the sulfate resistance capacity of manufactured sand concrete is comprehensivly studied.The mian achievements are concluded as follows:1. The sulfate resistance capacity of concrete with different amount of manufactured sand is studied basied on bending degradation coefficient, compressive degradation coefficient and rate of quality change. The result indicates the sulfate resistance capacity of concrete is improved with mix of manufactured sand and natural sand. With the increase of mixing amount, the sulfate resistance capacity of concrete is taking on the trend of rising first, then dropping. When the mixing amount is 50%, the sulfate resistance capacity of concrete is best.2. The sulfate resistance capacity of manufactured sand concrete with rice husk ash is also studied. The result indicates the rice husk ash improves the sulfate resistance capacity of manufactured sand concrete, and the more amount of rice husk ash, the better the capacity. The influence of three kinds of admixtures on sulfate resistance capacity of concrete are in an order:silica fume> rice husk ash> fly ash.3. The microsopic method based on nitrogen adsorption method is used to analyse the relationship between pore structure and sulfate resistance capacity of manufactured sand concrete. The result indicates the mix of manufactured sand and natural sand and the addition of RHA refine the pore size distribution of concrete, reduce the average pore size, improve the pore structure and improve the sulfate resistance capacity of manufactured sand concrete.4. The surface fractal dimension D is obtained based on FHH equation. And a linear relationship is established between surface fractal dimension and sulfate resistance capacity. The result indicates the bigger the surface fractal dimension, the better the sulfate resistance capacity.5. Three kinds of flexural stresses 0.2,0.4 and 0.6 are designed to study the influence of flexural stress on sulfate resistance capacity of manufactured sand concrete. The result indicates the flexural stress accelerates the sulfate attack of concrete and the greater the stress, the more obvious the acceleration.