Research On The Influence Of Stone Powder Content On The Crack Resistance Of Early-age Manufactured Sand Concrete

The application of manufactured sand alleviates the gap of natural sands in engineering.At the same time,due to the different molding methods of manufactured sand and natural sand,the surface of manufactured sand has many edges and corners,so that the mechanical bite ability between concrete aggregates is stronger than that of natural sand concrete,which has a good application prospect.However,there are some controversies on the limit of stone powder content in the current standard for the research of stone dust content on the strength of manufactured sand concrete.Currently,there is little research on the effect of stone dust content on the crack resistance of manufactured sand concrete,which limits the wide application of manufactured sand in engineering.This thesis adopts the method of mixing stone dust to prepare manufactured sand with four mass fractions of 5%,10%,15%,and 20%stone dust content.The design strength is C₂₈30 concrete mix ratio.At the same time,natural sand concrete is used as a comparison.The thesis through the analysis of the influence of stone dust content on the thermodynamic parameters of manufactured sand concrete,further study the influence of stone dust content on the crack resistance of manufactured sand concrete（that is,the cracking temperature difference）,and use numerical simulation methods to model and analyze the crack resistance of concrete specimens under the same boundary conditions.The results is verified by comparison with the test results.The influence of stone dust content in machine-made sand on the thermodynamic properties of concrete at 3d,7d,14d,28d ages is studied.With the increase of stone powder content,the tensile strength and compressive strength of concrete specimens first increase and then decrease,and both reach the maximum when the content of stone dust is 10%.And the elastic modulus gradually decreases.The compressive strength,tensile strength and elastic modulus of manufactured sand concrete are higher than natural sand concrete.The stone dust content has little effect on the thermal parameters of manufactured sand concrete,and the linear expansion coefficient shows a gradually increasing trend with the increase of the stone dust content.The crack resistance of manufactured sand concrete with different stone dust content in a temperature stress testing machine at a constant temperature of 20°C to 14 days of age was studied.Under the same boundary conditions,with the increase of stone dust content,the crack resistance of manufactured sand concrete shows a trend of first strengthening and then weakening.When the stone dust content is 15%,the crack resistance of concrete is the strongest.The crack resistance of natural sand concrete is weaker than that of manufactured sand concrete.It shows that at the age of 14 days,a proper amount of stone dust can enhance the crack resistance ability of manufactured sand concrete and reduce the risk of concrete cracking.Through numerical simulation,the deformation and stress of concretes under the same boundary conditions are analyzed,and their crack resistance ability is studied.It is concluded that the crack resistance ability of manufactured sand concrete shows a trend of first strengthening and then weakening with the increase of the stone dust content.At 15%stone dust content,concrete has the strongest crack resistance ability,which can better verify the accuracy of the test.After the above tests,the analysis results can be obtained.The appropriate amount of stone dust has a certain positive effect on improving the thermodynamic properties and crack resistance of the manufactured sand concrete.This result also provides a research basis for the manufactured sand to be widely used in engineering.