| In recent years,the construction field has consumed tremendous res ources,and the depletion of natural sand has become the shortage of natural resources in China.Lanzhou area in Gansu Province is rich in basalt ores,but the stone powder produced by the basalt manufactured sand has become a secondary resource which is d ifficult to use.This subject aims at exploring the application of basalt manufactured sand and stone powder in concrete,and studies the influence of basalt manufactured sand and stone powder on the performance of concrete.In this paper,the C50 strength grade is taken as the research object,and the compressive strength,shrinkage strain and chloride diffusion test of basalt manufactured sand concrete and basalt powder concrete are carried out respectively,in order to analyze the difference of the influence of basalt manufactured sand and basalt powder on the basic performance and chloride diffusion performance of concrete.The reasonable content range of basalt powder is obtained by compressive strength and shrinkage strain,and the influence of basalt powder on the basic properties of concrete is evaluated.The influence of basalt powder on chloride diffusion of concrete is analyzed by chloride diffusion coefficient and electric flux,and the chloride diffusion coefficient and electric flux are obtained by correlation fitting regression,respectively,with the content and age of basalt powder.The correlation between periods.The results of comprehensive tests show that:(1)The overall strength of basalt manufactured sand concrete is lower than that of natural sand concrete,but the later strength of basalt manufactured sand concrete increases rapidly;the single index ultrasonic velocity is not enough to evaluate the compactness or strength of basalt manufactured sand concrete,and the variation of ultrasonic velocity of concrete is fluctuant and quite different;the shrinkage strain of pure basalt manufactured sand concrete is higher than that of pure natural sand concrete,but it is not enough to evaluate the compactness or strength of basalt manufactured When the content of manufactured sand is not higher than 40%,the shrinkage strain of concrete can be reduced.The quantitative relationship fitting curves of strength and shrinkage strain of basalt manufactured sand concrete with the change of manufactured sand content can be obtained,and the best prediction function can be obtained.(2)When the content of basalt powder is not higher than 10%,its strength is slightly higher than that of benchmark,and decreases when the content of basalt powder exceeds 10%.When the content of stone powder is less than 10%,its strength increases slightly,but its workability decreases slightly.When the content of stone powder is less than 15%,the shrinkage strain of concrete will increase and the content of stone powder will increase.When the content of stone powder is less than 10%,the shrinkage increment does not change much.Controlling the content of stone powder below 10%can reduce the shrinkage strain of concrete and increase it when it is higher than 10%.The shrinkage strain decreases gradually with the increase of age and approaches the fixed value when it reaches 120 days.The correlation coefficient R~2 of strength fitting curve of stone powder doped in is higher than 0.95.The correlation coefficient R~2 of strength fitting curve of stone powder doped in is between 0.7 and 0.9,and its reliability is lower than that of stone powder doped in.The best predictive function of shrinkage strain fitting curve of concrete with and without stone powder is quadratic function of one variable,and the correlation coefficient R2 is higher than 0.9.(3)The chloride diffusivity and electric flux increase with the increase of age,and the chloride diffusivity and electric flux decrease with the increase of age.The best predictive functions of chloride diffusivity of stone powder are quadratic function and cubic function,respectively.The correlation coefficient R2 is higher than 0.9 in the range of stone powder content less than 20%.The expression of the best predictive function of electric flux is a cubic function of one variable.When the content of stone powder is not more than 20%,the correlation coefficient R2 is 0.87except for 28 days,and the other correlation coefficient R2 is higher than 0.9.(4)Whether basalt powder is doped internally or externally,the predictive function reliability of chloride diffusion coefficient varying with time is higher.The reliability of the predictive function of electric flux is lower than that of chloride diffusion coefficient,which is more convincing than that of electric flux in evaluating chloride diffusion performance. |
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