Study On Properties Of Ultra-fine Fly Ash High Strength Concrete

With the further development of China's construction industry,the research of concrete admixtures is also deepening.In this paper,the original ash is grinded into ultrafine fly ash(UFA)with an average particle size of 2.95 um.As a mixture of new mixed concrete,UFA is used to study the performance and mechanical properties of UFA concrete.In this paper,from two angles,one is to make a high strength concrete test block with different admixture(silica fume,original ash and UFA)instead of 10% cement,and compare the working performance of different concrete(slump and slump loss),and compare the early compressive strength of different concrete and the later compression of concrete.Strength,the splitting tensile strength of different concrete 28 d is compared.Secondly,the test block is made with UFA as the admixture instead of cement,and the compressive strength of the test blocks of different dosage of UFA in different ages is compared and analyzed,thus the optimal UFA content in the corresponding age is obtained,and the following conclusions are drawn:With different admixtures(silica fume,original ash and UFA)in place of 10% cement content,high strength concrete,superfine fly ash,fly ash and silica fume can be used as admixtures to improve the initial slump of fresh concrete,and the initial slump of concrete mixed with super fine fly ash or silica fume is improved.More obvious,to reach 210 mm.In addition,the three kinds of admixtures are separately disposed of concrete.The inhibition effect on the time loss of the slump of each concrete is ultrafine fly ash > fly ash > silica fume,and superfine fly ash as admixture can better restrain the slump loss of concrete.For the mechanical properties of the test blocks obtained by different admixtures,the compressive strength of the test block doped with UFA is greater than the strength of the fly ash test block based on the 7d age,and it is lower than the strength of the silica fume test block;the compressive strength of the silica fume concrete block is the largest increase in the period of 3d to 28d;the compressive strength of the UFA concrete block is strong during the period of 28 d to 60 d or to the 90 d.The maximum value of growth is far greater than that of other concrete blocks.With the same admixture UFA replacing the concrete with different dosage(10%,20%,30%,40%,50%),the strength of the concrete block with the amount of UFA is 30%,and the strength increases most,so the optimum content of the UFA system is 30%.This paper also associates with some problems in actual construction.From the theoretical point of view,using UFA as the advantage of the mixing material,it can solve the problem of engineering distance better,and can better solve the problem of excessive hydration heat in early concrete,and can save water and mud,and have better economic benefits.