Experimental Study On Water-binder Ratio Of Large Cementitious Materials

With the invention of high efficiency water reducing agent and continuous technical progress,modern concrete theory and practice progress,but also for the wide use of various admixtures in concrete laid a foundation.At present,the national policy has proposed carbon peak and carbon neutralization.Under the environment of green environmental protection,energy saving and emission reduction,limestone powder as a new admixture has entered people’s vision,and a new cementing material system has emerged.Admixture for cement and activity of classic gelled material,this article will cement,active admixture and inactive admixture of gelling system known as the big gelled material,at present such as powder class of inactive admixture research very much,but this kind of inactive gelled material to make the design of concrete problems begin to highlight,Ordinary concrete mix design procedures of mixture ratio design method in the water-binder ratio calculation part there is a common problem is according to the formula to calculate the water-binder ratio will appear larger deviation,lead to large amount of surplus of intensity,at the same time,the selection of active influence coefficient should be on the premise of the existence of water reducing agent were measured.Therefore,it is necessary to redefine the relationship between the large cementing material system and the water-binder ratio,so as to effectively consume solid waste,solve the current problem of high quality admixtures such as fly ash in short supply,and explore the relevant scientific laws of large cementing materials and concrete.This paper carried out the mortar test and concrete test,the mortar test selected benchmark cement,fly ash,slag powder,limestone powder and other cementing components,divided into9 kinds of water binder ratio each water binder ratio 16 groups of test to prepare mortar,study the compressive strength,durability and shrinkage performance of mortar;In the concrete test section,concrete composed of different large cementitious materials is designed for compressive strength test.The results show that 0.40 water-binder ratio combined with slag powder + limestone powder,fly ash + slag powder + limestone powder has a higher contribution to the compressive strength of cementing sand,and the composition of large cementing materials with 25% slag powder and 15% limestone powder and 10% fly ash respectively has a better contribution to the strength of cementing sand.When the ratio of the total amount of large cementing material to the mass of standard sand is fixed at 1:3,the strength of 0.40 waterbinder ratio is generally the highest.It is suggested to take 0.40 as the water-binder ratio to evaluate the strength of large cementing material containing limestone powder under the condition of adding admixture.In terms of concrete with different strength grades,the strength is the highest when the content of limestone powder is 20%.When limestone powder and fly ash are mixed,the strength decreases with the increase of limestone powder.The compressive strength of cementitious material group is higher when 70% cement,20% fly ash and 10%limestone powder are added.When fly ash,slag powder and limestone powder are mixed,the strength is the highest when the total content is 40%.These three kinds of large cementitious materials can provide better strength for concrete.The relationship between the composition of cementitious materials and the water-binder ratio corresponding to different strength grades of concrete is preliminarily clarified through concrete test.At the same time,according to the relationship between the compressive strength of 0.40 water-binder ratio in the mortar test and the water-binder ratio,and combined with the concrete test,the influence coefficient of mineral admixture strength was proposed,which was verified and corrected by the compressive strength of concrete test.In terms of durability and shrinkage performance of mortar,fly ash has influence on compressive strength of mortar,but in shrinkage test,the combination of fly ash and limestone powder can restrain shrinkage.In terms of carbonization performance,the carbonization depth of the water-binder ratio of 0.40 is smaller than that of other water-binder ratio test groups.In terms of crack resistance,from the crack width of 28 d,the crack time of reference cement was significantly delayed after the addition of admixtures.From the microscopic aspect,it can be seen that the micromorphology of the gelled sand with the addition of additives shows that the hydration is more complete,the structure is relatively dense and the defects are less when the water-binder ratio is 0.40.