Influence Of Coarse Aggregate Shape And Gradation On Dispersion Of Concrete Strength

With the continuous development and improvement of transportation infrastructure construction,the demand for the stability of concrete performance is getting higher and higher,and as the coarse aggregate is used as the continuous development and improvement of transportation infrastructure construction,the demand for the stability of concrete performance becomes more and more.As one of the important components of concrete materials,coarse aggregate has a great influence on the quality of concrete.In this paper,coarse aggregates along the Guangping Expressway in Qingchuan Mountain are used as raw materials to study the influence of needle-flaky content and gradation of coarse aggregates on the dispersion of concrete strength.Separate the coarse aggregate into needle-like flakes,and study its influence on the dispersion of concrete strength and the influence on the fluidity of fresh concrete.Through the design of different coarse aggregate gradations,the influence of coarse aggregate gradation on concrete strength dispersion and flow properties is studied.Because the traditional method is time-consuming and laborious to distinguish the shape of needles,this article is based on Matlab’s image analysis method to verify the feasibility of quickly identifying needles with image analysis.The following results have been obtained through research:Sampling and researching the grain shape of almost all stone quarries along the Guangping Expressway.We keep the content and quality of raw materials other than coarse aggregate unchanged.The bulk density of coarse aggregates,crushing index,needle flake content and other indexes are tested.It was found that the average content of needle-like flakes was about 6.4%,of which needle-like content accounted for about4%,and flake-like content accounted for about 2.4%.And the fluctuation range is not large,so the needle-like flakes are in a reasonable range.For this,we separate the needle-like and the flakes,and set 5 content levels,and the needle-free flake particles are used as the control group.The results show that :(1)The greater the needle-flaky content,the greater the dispersion of its strength.(2)The effect of needle-sheet shape on the strength dispersion of low-grade concrete and high-grade concrete is inconsistent.Its influence on the dispersion of the strength of high-grade concrete is higher than that of the dispersion of low-grade concrete.(3)The needle-like shape has a greater influence on the early strength dispersion of concrete than on the late strength dispersion of concrete.(4)The influence of flaky particles and needle-shaped particles on the dispersion of concrete strength is different.Aiming at the study of the influence of coarse aggregate grading on the dispersion of concrete strength,this paper separates the low-grade concrete and high-grade concrete,and divides the low-grade concrete into groups.33 raw material quarries along the Guangping Expressway are used for sampling.Obtain the finest gradation and the coarsest gradation that exceed the upper and lower limits of the specification,and combine the specifications to formulate 7 consecutive gradations.The median value of the specification is the best reference group and the single gradation is used as the control group.And late intensity for research.The high-grade concrete gradation is divided into groups,the original gradation of local coarse aggregate is adopted,and 4groups of continuous gradation are formulated in accordance with the specifications.The research results show that:(1)The influence of the gradation thickness of the coarse aggregate on the dispersion of concrete strength shows a certain regular change.The standard median strength dispersion is the smallest.Increasing and decreasing the coarse aggregate thickness will increase the intensity dispersion.(2)The intensity and intensity dispersion are centered on the standard median value,and increasing and decreasing the thickness of the coarse aggregate will show a symmetrical change.(3)The workability,mechanical properties and strength dispersion of single gradation are worse than continuous gradation.(4)The influence of the same gradation on the dispersion of the early concrete strength is greater than the influence of the dispersion of the late concrete strength.