An Experimental Study On Influence Of Silica Fume With Fly Ash On The Mechanical Properties And Durability Of Concrete

The mechanical properties,the anti permeability of concrete and the freezing resistance can be reacted through the microscopic pore structure.The appropriate part of the cement of fly ash and silicon powder is incorporated into the concrete.The addition of the admixture improves the concrete structure by improving the internal pore structure as well as the mechanical properties of the concrete.At the same time,the pollution problems of industrial waste materials such as fly ash and silicon powder are solved by recycling of industrial waste.The amount of cement used in the preparation of concrete materials is reduced,achieving the effect of economical applicability.Therefore,the research on fly ash and silicon powder compound concrete has multiple meanings of resource recycling,environmental protection and economy.In this study,fly ash and silicon powder are blended into ordinary Portland cement by equal replacement method.After the test calculation,the design of the mixture ratio is completed.With the change of curing time,the effects of compressive strength,splitting tensile strength,impermeability,freezing resistance and internal pore distribution under different dosage conditions are analyzed.The optimal choice is made by analyzing the amount of admixture.In this test,10%,20%,30%fly ash and 2%,4%,6%silicon powder are equally used to replace the part of P.042.5 ordinary Portland cement.The concrete test block with 9 different dosages is prepared with water-cement ratio of 0.29.The mechanical properties of the cubes of 7d,28d,56d and 90d in different curing periods are tested.Impermeability testing,freezing resistance testing and testing and analysis of internal porosity conditions are also implementedThe results of this study:1.Under the same curing period,the incorporation of fly ash has a disadvantage effect on the early strength of concrete.With the increase of the dosage,the strength also decreases,but the growth shows a large increase in the later stage.The strength plays a positive role throughout the curing period,but it does not fully compensate for the tendency of the fly ash to cause less strength in the early stage.In the later stage,the silicon powder is weak,but the strength of the concrete can still be slightly increased.2.In the different dosage,the strength of concrete also shows an increasing trend with the increase of the dosage.The trend in the first and middle stage are slow,and the growth is stable in the later stage.However,the amount of fly ash should be controlled below 30%,and the large amount of fly ash has a strong counteraction to the mechanical properties of concrete.3.The incorporation of fly ash and silicon powder can improve the Freezing resistance and Impermeability,and the effect is more obvious with the increase of dosage.30%of the amount of fly ash is different from the way of influencing the strength.Relatively small amount of fly ash will be more conducive to the permeability resistance and.4.The addition of the two admixtures is beneficial to improve the internal pore structure of the concrete.Because its particle size is smaller than that of cement,it can fully fill part of the pores inside the concrete,resulting in a large increase of harmless pores and a decrease of harmful pores.It has been improved from the micro level,which is also reflected in the improvement of macroscopic properties.