Study On The Characterization Of Manufactured Sand Particle Shape And Clay And Their Influence On The Performance Of Concrete

With the rapid development of infrastructure construction in China for many years,the consumption of concrete has reached an unprecedented level.As one of the important components of concrete,the consumption of fine aggregate has also increased.As a non renewable resource,natural sand has been unable to meet the market demand.As the most ideal substitute of natural sand,machine-made sand has become the main source of fine aggregate.However,at present,due to the inadequate production process and supervision measures of manufactured sand,there are problems such as unqualified particle shape and high content of stone powder or mud powder,which will have a great impact on the performance of concrete and even lead to potential safety hazards.In this paper,a variety of methods are used to quantitatively characterize the particle shape of manufactured sand.The particle shape parameters obtained by different existing characterization methods and their correlation are compared.Combined with the particle shape parameters,the effects of different particle shapes of manufactured sand on the properties of mortar and concrete are studied.The relationship between different kinds of mud powder and its content and MB value is analyzed.Combined with the test results of MB value,the influence of mud powder type and content on the macro performance and microstructure of mortar concrete is studied,which provides a theoretical basis for guiding the production,popularization and improvement of quality index of machine-made sand.The conclusions are as follows:1.The particle shape parameters of five kinds of manufactured sand were obtained by gap rate method,flow time method,aims and dip.The angularity of the five manufactured sands increases first and then decreases with the decrease of particle size.The edge angle in the range of 0.3-0.6 particle size is highly similar to the edge angle of the overall particle size,and there is little correlation between the edge angle and the two-dimensional shape value.The dip particle shape parameters obtained by single-sided projection method have great fluctuation.The aspect ratio,aspect ratio,radius ratio,roundness and fractal dimension of manufactured sand are obtained by increasing the projection direction and quantity.There is a strong correlation between aspect ratio and aspect ratio,but fractal dimension has no correlation with other parameters.2.Different particle shapes of manufactured sand have a significant impact on the performance of mortar concrete.MSC with the worst particle shape parameters has the worst workability,impermeability and highest compressive strength,and MSA with the best particle shape parameters has the best workability and impermeability.Among the several parameters,the correlation between edge angle and mortar fluidity and strength is the highest,and the correlation between particle shape parameter and impermeability is small.3.The addition of three kinds of mud powder can improve the MB value of manufactured sand,and its sensitivity to MB value is montmorillonite,illite and kaolin in turn.At the maximum content,the MB value of montmorillonite is 3.7 times that of illite and 6.8 times that of kaolin.The addition of mud powder will reduce the working performance of mortar concrete to varying degrees.The low content of montmorillonite will have a negative impact on the mechanics and durability of mortar concrete;However,illite and kaolin can improve the mechanical and durability of mortar concrete at low content and will also be damaged at high content.The addition of mud powder has no effect on the type of mortar hydration products but will affect the amount of products.The porosity,average pore diameter and cumulative pore volume in mortar will increase with the increase of mud powder content.The cumulative pore volume of montmorillonite,kaolin and illite increased by 67.12%,42.47% and 54.79% respectively when the content of mud powder was 10%.