Grain Shape Evaluation Of Coarse Aggregate And Its Influence On The Performance Of Concrete

With the development of concrete,natural high quality aggregate is decreasing.However,the demand for aggregate is increasing,This makes the aggregate production become the main source of concrete materials,and the dosage is also increasing.However,Irregular particles,including needle shaped particles,flaky particles and needle like particles,are produced during the production of mechanical lithotripsy.The quality of crushed aggregate and the content of needle flake will directly affect the final pulp and bone ratio of concrete,thus affecting the durability of concrete.The evaluation of coarse aggregate is different from that of other countries.This paper selects 3 typical evaluation methods: GB,Euro standard and strip screen.In the grain shape aspect,the three methods are used to carry out screening tests of different aggregate,packing density test and crushing index test,and the strictness of the three methods is compared.In the concrete test,under the premise of the irregular particle content as the only variable,according to the influence of the irregular particle content on the concrete performance,the experiment selected the different aggregate from two aspects of the low strength and the high strength concrete,and analyzed the influence of the irregular particle content on the amount of water reducing agent,and the strength and the chloride ion.The influence of osmosis.Through this research,we draw the conclusion that the European standard method is more strict for the evaluation of irregular aggregate properties,and the strip sieve method is the next.In the three way,irregular particles will lead to a decreasing trend of aggregate density.The increase of irregular particle content will affect the crushing index value of aggregate,and the influence of flake aggregate on crushing value is greater than that of needle shaped aggregate.When the content of irregular particles in coarse aggregate reaches 5%,the fluidity of concrete mixture will decrease obviously,but when the content of low strength concrete is 10%,the strength of concrete is highest,the strength of concrete is the highest,the national standard method,the bar sieve method,and the European standard method are small,the gradient of the particle content is smaller and the highest is at the same time.The content is only 15%.The influence of irregular particle content on the compressive strength of concrete is not obvious,but the strength under the European standard method is higher than that of the national standard method and the bar screen method.For the bar screen method,when the irregular particle content is 20%,the strength decreases more obviously,and the strength decreases by 13.13% when it reaches 30%.In the high concrete,the influence of the GB method is the most obvious for the chloride ion penetration.The electrical conductivity is the highest,the change of the European standard method is relatively gentle.Under the bar screen method,the electrical conductivity reaches the highest when the irregular particle content reaches 10%.