Study On The Morphological Characteristics Of Limestone Mechanism Sand And The Performance Of Mechanism Sand Self-compacting Concrete

Sand as a fine aggregate,is the main component of concrete,concrete preparation of sand mainly includes two types: sand and natural sand.Natural sand,in a short time can not be recycled,and the mechanism of sand,in the mountains more raw materials rich areas,its production and application,will fundamentally solve the problem of natural sand resources depletion and so on.Self-compacting concrete as a "green concept" under the product,because of its high mobility,high resistance to segregation bleeding,high resistance to deterioration and good durability,can better meet the reinforcement of complex engineering and other complex Requirements,in some complex projects and special projects have been applied to the promotion.At present,the fine aggregate used in the preparation of self-compacting concrete is very demanding,and the quality of the produced sand is uneven.The grain shape of the sand is more irregular,the roughness is larger and the surface morphology is more complicated Difficult to meet the requirements of self-compacting concrete preparation.This paper selected five parameters of length-width ratio,roundness,fullness ratio,sphericity and fractal dimension to characterize the morphology of fine aggregates.Related parameters were quantitatively determined based on digital image processing(DIP)technology and fractal theory.The results showed that the shape of the river sand was close to that of the sphere,and the crushing mechanism had obvious angular and irregular shapes,and the difference was very large.In the process of sand production,it was necessary to shape and process the sand.The proposed values for the roundness,aspect ratio,fullness ratio,sphericity,and fractal dimension of the limestone mechanism after shaping were: 0.88 ~1.00 and 0.74 ~1.00,0.97~1.00,0.82~1.00,and 1.010~1.025,respectively.In the study of the performance of mechanical sand self-compacting concrete,the widely distributed limestone sands in the southwest region were selected as research objects.Studies had shown that the effect of the content of limestone-based sand and gravel on the performance of concrete existed a certain rule,and there was an optimal value of stone powder content.It was proposed that for medium-strength sand self-compacting concrete,the content of stone powder was suggested to be 6%~16%.For high-strength machine-made sand self-compacting concrete,the content of stone powder was recommended to be 6%~12%.Adjusting the proportion of greater than 1.18 mm and less than 1.18 mm mechanism sand particles can improve the gradation of self-compacting concrete with mechanism sand.When the sand ratio was in the range of 39%~42%,the limestone mechanism sand had good work performance of self-compacting concrete.The study on the mechanism of action of limestone rock powder in self-compacting sand with mechanism sand has concluded that the incorporation of stone powder prolonged the dissolution period of the hydration reaction of the cementitious material.With the increase of the amount of stone powder,the induction period and accelerating period of the condensate materials were correspondingly reduced.After adding limestone rock powder,no hydration calcium carbonate was detected in the hardened cement slurry,and there was a large amount of stone powder not involved in the reaction,indicating that the volcanic ash efficiency of silica fume and fly ash is relatively strong and the effect of stone powder on cement hydration was far less than that of silica ash and fly ash.