Research On The Effect Of Admixtures On The Strength And Autogenous Volume Deformation Of Externally Mixed MgO Roller Compacted Concrete

Roller Compacted Concrete Mixed with MgO(RCCM)is a hydraulic material that can simplify temperature control measures,has significant economic benefits,and is in line with policy orientation.At present,the regional shortage of fly ash resources and the problems of long-distance transportation are prominent.There are many studies or applications on RCCM with fly ash alone,and roller compacted concrete(RCC)with limestone powder or(and)phosphorous slag powder.However,there are few studies on the preparation of RCCM with limestone powder or(and)phosphorous slag powder.In this paper,through strength test,autogenous volume deformation test,XRD,MIP,SEM,etc.,the influence of full or partial replacement of fly ash by limestone powder or(and)phosphorous slag powder on the strength and autogenous volume deformation of RCCM is discussed,providing engineering applications Technical basis.Based on the experimental conditions,the main conclusions are as follows:(1)When the fly ash content of RCCM is 60%(the same below),partial or full replacement of fly ash with phosphorous slag powder alone will not change the delayed micro-expansion characteristics of RCCM or the characteristics of stable expansion;When phosphor slag powder replaces part of fly ash,the intensity of RCCM changes little,and the autogenous volume deformation can increase by about 10×10^-6;when phosphor slag powder replaces all fly ash,the strength increases by about 10%,and the RCCM expands stably The amount change is small.(2)When limestone powder is used alone to replace part or all of fly ash,RCCM still has delayed micro-swelling characteristics or the expansion volume tends to be stable;when limestone powder is used to replace part of fly ash,RCCM stable expansion volume increases,It is mainly at the expense of strength,so it is recommended that the replacement ratio should not exceed 1/3,and the stable expansion can increase by about 15×10^-6.(3)When PL admixtures are used to replace all fly ash,RCCM also has the characteristics of delaying micro expansion and stabilizing expansion;RCCM also increases autogenous volume deformation at the expense of strength,so it is recommended that phosphorous slag powder accounts for The proportion of PL admixture is not less than 2/3,and the stable expansion and strength change of RCCM is small at this time.(4)For similar projects,it provides a test mix reference scheme and a comparable fly ash replacement scheme.