Research On Fabrication And Property Of Granite Manufactured Sand Concrete

In the area of sand and gravel shortage,the effective use of granite manufactured sand to prepare concrete is an urgent technical problem to be solved.As a harmful substance of machine-made sand,excessive mica content will cause problems such as decreased working performance and mechanical strength of concrete,which will limit its application in practical engineering.Therefore,this paper takes the granite mechanism sand of Pubo section of Nanzhan Expressway as the research object.Firstly,the basic characteristic indexes of granite mechanism sand are determined.Then,the influence of different mica content on the working performance and mechanical properties of mortar and concrete was studied,and the influence mechanism of mica on cement paste was revealed from the microscopic point of view by SEM technology.Based on this,an effective mica-cement paste regulator was developed,and the modification mechanism of the regulator was revealed by SEM and MIP technology.Finally,the optimal dosage of the regulator was obtained by comparing the fluidity and mechanical properties of the mortar and concrete with different dosage of the regulator,the preparation method of the concrete was determined,and the durability of the concrete with the recommended ratio was studied.The main research work and achievements are as follows :(1)Test and analysis of basic characteristics of granite mechanism sand.The grading characteristics,fineness modulus and stone powder content of manufactured sand were obtained by screening.The content of machine-made sand mica was measured by comprehensive specification method and X-ray diffraction method.The results show that the granite manufactured sand has a high content of needle flakes and uneven surface roughness,and the mica content is 11.8 %.(2)Study on the effect of mica content on the properties of mortar and concrete.The influence of mica content on the fluidity and mechanics of mortar and concrete was studied by controlling the content of mica by mixing granite machine-made sand with mica and machine-made sand without mica.The influence mechanism of mica on cement paste was analyzed from a micro perspective by SEM technology.The results show that the higher the mica content,the worse the fluidity of mortar and concrete,mainly due to the strong adsorption of mica-containing manufactured sand.Compared with concrete without mica,the 28 d compressive strength of concrete with11.8 % mica content decreased by 15.3 %.Part of the mica exists in the mechanism of sand and stone powder,which makes the mica and cement paste have a weak bond zone,which leads to the significant deterioration of the mechanical properties of mortar and concrete.(3)Study on preparation technology of granite manufactured sand concrete.Based on the influence mechanism of mica on cement paste,a regulator that can solve the influence of mica was developed.The modification mechanism of the regulator was analyzed from three aspects : particle distribution morphology,appearance morphology and pore size distribution characteristics by SEM and MIP technology.By adjusting the design parameters of the mix ratio,the preparation law of the concrete without adding the regulator is obtained,and then the preparation law of the mortar and concrete modified by the regulator is obtained by adding the regulator to prepare the mortar and concrete,and the recommended mix ratio of the concrete containing the mica granite machine-made sand is determined.The results show that the modifier can effectively improve the mechanical properties of mortar and concrete,and the nano-crystal nucleus of the modifier makes the cementitious material more evenly dispersed.After adding the regulator,the porosity in the cement paste decreases and the interior of the paste is denser.When the dosage of regulator is6.0 ‰,the mechanical properties of mortar and concrete are the best.(4)Study on the durability of granite manufactured sand concrete.The concrete was prepared by using the recommended mix ratio,and the drying shrinkage performance,chloride ion penetration resistance and carbonation performance of the concrete containing mica granite manufactured sand were comprehensively analyzed.The results show that the 150 d dry shrinkage rate of the concrete with the regulator is reduced by 5.0 % ～ 7.0 % compared with the concrete without the regulator.In addition,the electric flux of concrete with modifier is lower than that of concrete without modifier,and the electric flux of 6h is reduced by 250 C ～ 400 C.The incorporation of regulators can reduce the carbonation depth of concrete containing mica granite mechanism sand at each carbonation age;in addition,the compressive strength of concrete after carbonization is improved.