Influence Of Sand Quality On Performance Of Concrete

In recent years, with the further development of our economy and urban infrastructure, there is a lack of the natural sand used to meet the requirements for engineering construction, so the use of manufactured sand to prepare concrete has become a trend. Manufactured sand particle size distribution is similar to natural sand.With its wide source of raw materials and stable performance, it is an ideal substitute for natural sand.Firstly, the influence of three manufactured sand with representative lithologic characters on the action effect of the concrete performances were researched, which include limestone, basalt and gneiss. The results showed that the change of lithologic characters of manufactured sand had effect on the concrete workability, strength and durability, but that the difference was not significant.Secondly, the effect of lime stone dust content on concrete properties was studied. The results showed that the proper amount of stone dust could improve the gradation of manufactured sand, increase the paste volume and fill the void among particles, which could improve the workability and strength of manufactured sand concrete. As crystal nuclei, stone dust have effects of stimulation on hydration of cement.CaCO3 in stone dust participates hydration of C3 A and forms hydrated calcium carboaluminate,thus enhances hydration of cement.Stone dust also have densification effect on transition zone and improve pore structure,then improve properties of concrete.However, the optimum content of stone dust in manufactured sand was different for manufactured sand concretes of different strength grade.For concrete strength grade C25, C35 and other low intensity level, the optimum range of crusher dust content is 15 to 21%; For C55 and above grade concrete,the best crusher dust content is 7% or less.Finally, the effect of characteristic indexs of manufactured sand on the concrete performance was studied.The results confirmed that the mechanism of sand methylene blue value has nothing to do with the lithology and stone powder content, and is proportional to the mud powder content. The improvement of mechanism sand methylene blue value, increased the plastic viscosity of concrete, increasing the stern acid on the adsorption of water reducing agent. For the influence of mechanical properties and durability of concrete is related to the strength grade. the appropriate value of methylene bluein favor of sand on the strength and durability of coagulation increased, but high-strength grade concrete, raising the value of methylene blue will result sand concrete strength and durability deteriorated.