Study On Mechanical Test And Properties Of Limestone Manufactured Sand Concrete Structure In Northern Guangxi

The demand for river sand in the construction market has increased sharply in recent years.The excessive exploitation of river sand leads to the destruction of ecological environment.As a new material to replace river sand,mechanical sand is of great significance in practical engineering.The influence of stone powder content on the action mechanism,nonlinear constitutive relation and design calculation of Manufactured sand concrete(MSC)structure is particularly important.However,these technologies are not mature yet.The characteristics,production technology,physical properties of materials and mix ratio design of limestone mechanism arenite from Rongshui to Hechi expressway in northern Guangxi were studied in this paper.Besides,84 concrete prismatic test blocks of 100mm×100mm×300mm were poured,the stress-strain constitutive test of concrete was carried out,the failure mechanism was explored.The constitutive equation suitable for the Manufactured sand concrete(MSC)is obtained by least square method to fit the test curve.Then the accuracy of constitutive equation is verified by using finite strip method with MATLAB analysis software.Finally,the constitutive equation of mechanical sand concrete is introduced and the formula of flexural capacity of MSC beam is deduced.The results are as follows:(1)The selected limestone parent rock has excellent mechanical properties and quality,and the standardized production method is adopted to obtain the limestone manufactured sand(MS)with excellent physical properties.The MS and river sand have similar physical properties,which completely meet the requirements of the specification.The MS and river sand have similar physical properties,which completely meet the requirements of the specification.(2)In order to study the MSC hydration products chemical composition and MSC pore structure,explore powder changes at the micro level of MSC mechanism.After the relevant test,we found that the limestone powder could participate in the cement hydration reaction and fill the pore structure of concrete,thus influence MSC macroeconomic performance.(3)We explore the limestone powder on its macro performance indicators by carrying out the durability performance of MSC and mechanical performance test.The results show that the resistance to chloride ion permeability of concrete with stone powder content of MS increases with the increased,while the compressive strength showed a trend of decrease after the first increase,river sand concrete permeability,compressive resistance than the vast majority of MSC.It also confirms the mechanism of the effect of limestone powder on the microstructure from the macroscopic view.(4)In uniaxial compressive stress-strain constitutive experiment of MSC,we found that the MS and river sand concrete failure are,about 60 degree angle,pattern basic similar.Horizontal and inclined cracks sand mechanism of high strength concrete test curve fell steep,damage forms for brittle failure.It shows that the ductility of river sand concrete is much better.(5)After analyzing and fitting the test data,it is suggested that the stress-strain curve of MSC would be expressed by segmental rational formula,and the fitting results are basically consistent with the test data.The applicability of constitutive equation of MSC is verified by programming calculation.(6)It is deduced that the coefficient of alpha and beta in the calculation formula of the flexural capacity of the normal section of MSC is smaller than that of ordinary concrete.