Property Study Of Sand Concrete Based On The Characteristics Of Tailings Sand

Sand concrete as a new cement-based material,its property is significantly influenced by the characteristics of the aggregates.The workability of sand concrete affected by tailings sand with fine grain and angular character,and results in ineffective utilization of tailings resources.But the tailings sand after the admixture modified can not only reduce the void between the aggregates,enhance the meshing effect between the particles,but also promote the hydration of the cementitious materials,it can promote the mechanical properties of concrete to some extent.Sand concrete is prepared aim to the characteristics of tailing sand to improve its property,not only has practical guidance,but also has good social and economic benefits.The feasibility of tailings sand as a construction sand for the preparation of sand concrete was explored in this paper,the influence of tailing sand characteristics on the concrete working property with tailing sand was studied,the surface response method was used to optimize the mix proportion of tailings sand concrete under different ratio of sand to cement,the influence of tailing sand characteristics on the compressive strength,flexural strength,bending stress and toughness of tailings sand concrete was studied,the effect of tailings sand characteristics on the Durable property of sand concrete under different ratio of sand to cement were analyzed by the freeze-thaw test,and the roughness of the fracture surface of sand concrete was characterized by fractal dimension,and the expansion path of microcracks,weakness of the interface transition zone and hydration products in sand concrete were characterized by SEM.The following main conclusions were drawn:(1)The iron tailing sand from Shangluo area and gold tailing sand from Tongguan county are mainly composed of quartz,feldspar and silicate minerals,which have stable physical and chemical properties,and the quartz content is close to 70%.The fineness modulus of the tailing sand is finer,but a series of physical and chemical properties meet the requirements of sand for construction.(2)According to optimization analysis with surface response,the optimum ratio of water to cement and admixture dose for sand concrete are 0.2 and 2.5% respectively,when the ratio of sand to cement is 1.5.The optimum ratio of water to cement and admixture dose for sand concrete are 0.3 and 1.5% respectively,when the ratio of sand to cement is 2.0.The optimum ratio of water to cement and admixture dose for sand concrete are 0.40 and 3.0% respectively,when the ratio of sand to cement is 2.5.The optimum ratio of water to cement and admixture dose for sand concrete are 0.50 and 3.0% respectively,when the ratio of sand to cement is 3.0.(3)Compared with ordinary fine sand concrete,the compressive strength of iron tailing sand concrete increased by 3.29% and flexural strength by 10.12% on average at 7 days;the compressive strength increased by 5.06% and flexural strength increased by 8.33% on average at 28 days.However,the 7 days compressive strength of gold tailing sand concretes was not much different from that of ordinary fine sand concrete,and the flexural strength increased by4.12% on average;the 28 days compressive strength was lower than that of ordinary fine sand concrete,with an average decrease of 6.63% and the flexural strength was increased by 2.24%on average.The brittleness coefficients of sand concrete all ranged from 5:1 to 6.5:1,but the brittleness coefficient of iron tailing sand concrete was the lowest,averaging 5.32% lower than that of gold tailing sand concrete;and 9.43% lower than that of ordinary fine sand concrete.(4)The freeze-thaw property of tailings sand concrete and ordinary fine sand concrete decreases with the increase of the ratio of sand to cement,and the mass loss rate and relative dynamic elastic modulus loss rate of iron tailings sand concrete under each freeze-thaw cycle are basically lower than those of gold tailings sand concrete and ordinary fine sand concrete under the same mix proportion.When the ratio of sand to cement is 2.5 or 3.0,the freeze-thaw resistance of tailings sand concrete reaches the highest level of F250;when the ratio of sand to cement is1.5 or 2.0,the freeze-thaw resistance of tailings sand concrete decreases slightly and the freeze-thaw resistance is F200.