Study On The Influence Of Coarse Aggregate Types On High Performance Concrete Under Compound Admixture

Since the quantity of cement as cementing materials in concrete is very big,it indicates the use the admixtures such as coal ash,slag powder partly replacing cement in the importance of high performance concrete,and choose the appropriate admixture than it was especially important;Coarse aggregate in concrete is an important part in concrete aggregate,accounts for about 60% ~ 70% of aggregate quality,Different kinds of coarse aggregate performance difference is very big,this also leads to the configuration of the performance of high performance concrete difference is big,therefore,the study on the coarse aggregate of different habitats and varieties should be further studied.In this paper,coal ash and slag powder in Lanzhou and its surrounding area are selected as admixture to study its basic properties;select the limestone,diorite and pebble coarse aggregate,analyze the difference of its performance and morphology.And determine the proportion of the suitable admixture by the strength and fluidity of the mortar.And the influence of coarse aggregate types on the workability,mechanical properties and durability of high performance concrete is studied in the appropriate proportion of admixtures.The results show the crushing value of the coarse aggregate of diorite is the smallest,its strength is higher,the crushing value of the limestone coarse aggregate is the largest,the strength is slightly weaker,the pebble's angularity is weak,the spheroid is similar,the surface is smooth,the coarse aggregate of the diorite is the second,the limestone coarse aggregate is the strongest and the surface is rough.The composite admixture(coal ash and slag powder)as a whole instead of the amount is 20%,the coal ash:slag powder = 1:2,flexural and compressive strength of mortar can meet the requirements,fluidity of sand reach the best.The high performance concrete with pebble configuration has the best mobility,followed by diorite allocation,and the worst limestone configuration.Limestone configuration of high performance concrete early concrete compressive strength,flexural strength,the highest,diorite configuration of The Times,the configuration of the pebble,compressive strength,bending strength and the difference is not obvious,to the late stage,diorite configuration concrete compressive strength,flexural strength,the highest of diorite configuration C50 standard about 17% higher than that of compressive strength of concrete,limestone configuration.In terms of durability,The sulfate corrosion resistance of high performance concrete with diorite configuration is better than that of the other two kinds of coarse aggregate,and the decrease of sulfate corrosion resistance coefficient of concrete in the two mechanism coarse aggregate is slower;the frost resistance durability of the high performance concrete with the diorite coarse aggregate is 37.2%,the frost resistance is the best,while the frost resistance durability coefficient of pebble allocation is the lowest.