Study On The Effect Of Aggregate Characteristics On The Crack Resistance Of Steel Fiber Reinforced Concrete

With the rapid development of the concrete industry,people’s research on steel fiber reinforced concrete is becoming more and more in-depth.As one of the important properties of steel fiber reinforced concrete,crack resistance is of great significance in preventing cracking.Because the addition of steel fibers can effectively prevent the expansion of micro cracks and the formation of macro cracks in concrete,we often overlook the crack resistance effect brought by aggregates.As a skeleton,aggregates play a huge role in the workability,strength,and crack resistance of concrete.This article studies the impact of coarse aggregate type,maximum particle size,fine aggregate type,and mechanical sand and stone powder content on the crack resistance performance of steel fiber reinforced concrete.The specific content is as follows:(1)According to the principle of mix design,the C50 concrete mix proportion is determined.Based on this mix proportion,changes in the types of coarse aggregate,maximum particle size,fine aggregate,and mechanical sand and stone powder content are carried out.By adding or reducing water reducing agents and adjusting the sand ratio,the slump of the concrete mixture is basically the same.The results show that the working performance of the concrete is better after replacing the coarse aggregate with limestone crushed stone,but there is a risk of segregation;The impact of the type of fine aggregate on the workability of concrete can be ignored;The increase in the maximum particle size of crushed stones requires less water reducing agents and higher sand content to ensure consistent concrete performance,and the segregation rate of concrete increases with the increase of crushed stone particle size;The increase in the content of machine-made sand and stone powder requires more water reducing agents to ensure consistent working performance of the concrete.The addition of machine-made sand and stone powder can effectively reduce segregation rate,increase uniformity,and achieve the best anti segregation rate at 6%.(2)Exploring the variation law of aggregate characteristics on mechanical properties while ensuring that the working performance of concrete is basically consistent.The results show that the mechanical properties of concrete are better when coarse aggregate is replaced with limestone and gravel;The mechanical properties of concrete are better when the fine aggregate is replaced by cobblestone machine made sand with limestone machine made sand;Increasing the particle size of crushed stones can improve the mechanical properties of limestone concrete,and the strength is optimal when the maximum particle size is 26.5mm;Increasing the particle size of crushed stones can reduce the mechanical properties of cobblestone concrete,and the strength is the worst when the maximum particle size is 26.5mm;Adding machine-made sand and gravel powder can effectively improve the mechanical properties of concrete,and the optimal dosage is 6%,at which point the mechanical properties of concrete are optimal.(3)Selecting several sets of ratios with better mechanical properties for the threepoint bending test of composite beams,to explore the variation law of aggregate characteristics on the occurrence of cracks in steel fiber concrete under external loads.The results show that replacing coarse aggregate with limestone crushed stone can effectively improve the fracture performance of concrete;The replacement of fine aggregate by limestone mechanism with cobblestone mechanism sand can effectively improve the fracture performance of concrete;Increasing the particle size of crushed stones can effectively improve the fracture performance of concrete,and when the maximum particle size is 19 mm,the increase is the greatest,indicating the optimal fracture performance of concrete;The addition of machine-made sand and gravel powder can also effectively improve the fracture performance of concrete,and the maximum increase is achieved when the content is 6%,indicating the optimal fracture performance of concrete.(4)Selecting several sets of ratios with better mechanical properties to explore the changes in aggregate characteristics on the early and long-term crack resistance performance of steel fiber reinforced concrete.The results show that replacing coarse aggregate with limestone crushed stone can effectively improve the early crack resistance and impact toughness of concrete,and reduce dry shrinkage deformation;Replacing fine aggregate with limestone machine made sand with cobblestone machine made sand can effectively enhance the early crack resistance of concrete,improve impact toughness,and reduce dry shrinkage deformation;Increasing the particle size of crushed stone can effectively enhance the early crack resistance,improve impact toughness,and reduce dry shrinkage deformation,and the overall crack resistance performance of concrete is optimal when the maximum particle size is 19mm;The addition of machine-made sand and gravel powder effectively improves the early crack resistance and impact toughness of concrete,reduces dry shrinkage deformation,and 6% is the optimal dosage.