Study On Long-term Performance Of Self-compacting Concrete With Manufactured Sand

In view of the increasing scarcity of natural sand resources,C50 self compacting concrete is prepared by limestone machine-made sand in this paper.The particle characteristics of machine-made sand,mortar performance and long-term performance of self compacting concrete are studied.The research results have certain reference value for the application of dense reinforced structure and concrete filled steel tube engineering.The main research work and conclusions are as follows:In this paper,starting from the particle characteristics of machine-made sand,firstly,the performance of cement mortar is studied,the specific surface area of natural sand and limestone machine-made sand is calculated by experiment,and the morphology characteristics of different fine aggregate are analyzed by image processing software;the influence of different kinds of fine aggregate aggregate ratio,fly ash content and silica fume content on the rheology of cement mortar is measured by water film thickness;orthogonal design is adopted The influence of different raw materials on the fluidity and mechanical properties of cement mortar was studied.The results show that the self similarity of machine-made sand is better than that of natural sand,its roundness value and axial coefficient deviate more from 1,and its shape is more inclined to irregular cube;fly ash and silica fume can reduce the minimum water demand for water film forming,fly ash can increase the water film thickness,while silica fume in high water consumption can hinder the increase of water film thickness,and the addition of fly ash can slightly reduce the compressive strength of cement mortar Low replacement rate of machine-made sand can slightly improve the flexural strength of cement mortar.Secondly,the "full calculation method" and "absolute volume method" are used to design the mixture ratio of C50 machine-made sand self compacting concrete with the same raw material,and the gradation of coarse aggregate is optimized.The strength of concrete designed by the two methods can meet the design requirements,but the sand ratio and mixture fluidity of "full calculation method" are low,"absolute volume method" is more suitable for the mix design of self compacting concrete with machine-made sand.Then,the effects of different stone powder content of machine-made sand on the performance,mechanical properties and long-term durability of self compacting concrete mixture are studied.The influence of different fine aggregate on the performance of self compacting concrete mixture is analyzed by using three indexes of self compacting performance,clearance passing performance and anti segregation performance;the cube compressive strength and splitting tensile strength of different ages are measured,and the influence of different fine aggregate on the mechanical performance of self compacting concrete is analyzed;the chloride ion penetration resistance test,frost resistance test,water penetration resistance test and sulfate resistance test are carried out The effects of different fine aggregate on the long-term durability of self compacting concrete were studied by erosion test,carbonation test and early cracking test.The results are as follows: with the increase of stone powder in machine-made sand,the mechanical properties,mechanical properties and long-term properties of self compacting concrete mixture increase first and then decrease;the mechanical properties of machine-made sand concrete with 7% stone powder content are the best,and the mechanical properties of machine-made sand concrete with 9%stone powder content are the best;the stone powder content is resistant to chloride ion erosion,sulfate erosion and early cracking The durability of the machine-made sand with stone powder content is 7% ～ 9%,and the early crack resistance of the concrete with 5% stone powder content is the best.To sum up,the stone powder content of C50 machine-made sand self compacting concrete should be 7%,not more than 9%;the single C50 machine-made sand self compacting concrete has good chloride ion resistance,frost resistance,water penetration resistance,sulfate corrosion resistance and carbonation resistance,which can be used to design concrete structures with a life of 100 years...