Study On Application Of Limestone Manufactured Sand Reinforced Concrete In Mountainous Areas Of Northwest Guangxi

Manufactured sand is a new type of building material obtained by rinsing,crushing and screening natural mother rocks.As natural sand resources are increasingly in short supply,studying the mechanical property and durability related to manufactured sand concrete and further exploring the flexural capacity of manufactured sand reinforced concrete is significant to infrastructure construction and ecological protection in areas lacking in natural sand resources,and also lays foundation for promoting the application of manufactured sand.This paper studies the related physical property indicators of manufactured sand by using manufactured sand made from limestone exploited in Lingyun County,Baise City,Guangxi.And the sand is used as fine aggregate to prepare manufactured sand concrete test blocks with different rock flour contents(0%,5%,10%,15%,20%)under the intensity of C50 by means of orthogonal design.Meanwhile,manufactured sand reinforced concrete beams with a rock flour content of 5%and 10%and a manufactured sand replacement rate of 0%,20%,40%,60%,80%,100%are cast.Experimental study and finite element analysis are conducted to test the mechanical property of the manufactured sand reinforced concrete beams.The major study contents are as follows:(1)Experiments are done to study the physical properties of both manufactured sand and natural sand including grain composition,fineness modulus,apparent density,clay lump content,MB value and ruggedness.The result shows similarities or no remarkable differences between the average values of all indicators of manufactured sand and natural sand,so the preparation methods for natural sand concrete can be applied to manufactured sand concrete.(2)Lots of experiments are done to study the compressive strength,breaking strength,splitting tensile strength,axial compressive strength,elasticity modulus mechanical property,and chloride ion penetration resistance of manufactured sand concrete with different rock flour contents.The results suggest that proper rock flour content can facilitate the mechanical property and durability of manufactured sand concrete.When the rock flour content is about 10%,manufactured sand concrete has better properties than natural sand concrete.(3)Experiments are done to test the bearing capacity of C50 manufactured sand RC beams and study the strain,middle span deflection,crack development and other characteristics of the concrete and longitudinal tensile bars of the tested beams.The results show similarities of manufactured sand RC beams and natural sand in fracture and destruction forms,and that the tested beams with a rock flour content of about 10%have better bearing capacity than natural sand concrete.That provides certain basis for the application of manufactured sand in real projects.(4)ABAQUS finite element software is used to conduct analogue simulation to the bending and bearing test for manufactured sand RC beams with an aim to study the flexural behavior,deflection change,crack developing,etc.of manufactured sand RC beams applied in real projects.The results suggest:there is a small gap between the ultimate load acquired by numerical simulation calculation and the test result,so the software can properly simulate the test results.Meanwhile,parameters like reinforcement ratio and sectional dimension can be changed to discuss their impact on the bearing capacity of manufactured sand RC beams.