Effect Of Replacing Part Of Cement By Granite Powder On Mechanical Properties Of UHPC

Ultra-high performance concrete(UHPC)is a kind of cement-based composite with ultra high strength,high toughness,and low porosity.However,the cost of UHPC is expensive.In the last few decades,environment of Fujian province was polluted by a large amount of abandoned granite powder(GP).If we can apply GP to UHPC,it can not only reduce the cost of UHPC but also improve environment.As a admixture,GP has been applied to preparation of bricks,ceramics and ordinary concrete.In order to decrease the cost of UHPC,rice husk ash,fly ash and slag has used to preparation of UHPC as a admixture.However,as a admixture,there are few GP has been applied to UHPC.Therefore,this paper investigated a part of ordinary Portland cement(OPC)of UHPC replaced by GP(CO)and a part of OPC with all of quartz powder of UHPC replaced by GP(CS).The effects of replacement rate(the mass ratio of GP to cement replaced),curing condition,curing age on UHPC mechanical properties were studied in this paper.Type of hydration productions,morphology and pore structure were analyzed and regulation of mechanical properties were explained,by FSEM-EDS,XRD,NMR and pore structure analyzer.Conclusions are presented as follows:1.In CO and CS systems(W/B=0.18,autoclave curing,curing age 28 day),hydration production is Tobermorite,average pore size and cumulative pore volume decrease.Furthermore,cement paste and interfacial transition zone become density,Q0 and Q1 decrease and Q2 increase as the replacement rate of GP increases from 0 to 15%,while small quantities of Q3(1Al)is produced in CO system.So all the compressive strength and flexural strength increase and ratio of compressive strength to flexural strength decrease.As the replacement rate of GP increase from 15%to 25%,average pore size and cumulative pore volume increase,while cement paste and interfacial transition zone become incompact,as a result,the compressive strength and flexural strength all decrease and ratio of compressive strength to flexural strength increase.Therefore,the compressive strength and flexural strength are highest and ratio of compressive strength to flexural strength is minimun when the replacement rate of GP is 15%.Compared with CO system,the compressive strength of CS system drops by 2.73%,flexural strength increases by 0.56%and ratio of compressive strength to flexural strength drops by 1.20%.2.In CO and CS systems(W/B=0.18,the same replacement rate of cement by GP,curing age 28 day),as the curing condition changes from standard curing,water curing at 90? to autoclave curing,quantities of calcium hydroxide and unhydrated cement decrease,Cement paste become density,and bond of cement paste and aggregate strengthen is strengthened,Furthermore,interfacial transition zone become density,while average pore size and cumulative pore volume decrease.Q0 decreases,Q2 decreases and Q3(1Al)increases in CO system.As a result,the compressive strength and flexural strength increase obviously and ratio of compressive strength to flexural strength decrease.Further,autoclave curing can promote prodution of Q3(1Al),and replacement rate of GP have a significant influence on increasing amplification of the compressive strength and flexural strength and declining amplification of ratio of compressive strength to flexural strength.In addtion,compared with CO system,the compressive strength of CS system increases by 0.30%,2.03%,2.01%and the flexural strength of CS system drops by 4.17%,2.10%,1.28%in these three curing conditions.3.In CO and CS systems(autoclave curing,the same replacement rate of cement by GP,curing age 28 day),as water-binder ratio increases,cement paste and interfacial transition zone become loose,while average pore size and cumulative pore volume increase,and the compressive strength,flexural strength and and ratio of compressive strength to flexural strength decrease obviously.Furthermore,when the water-binder ratio is 0.20,replacement rate of GP has a signidicant influence on declining amplification of the compressive strength,flexural strength and ratio of compressive strength to flexural strength.when water-binder ratios are 0.16,0.18 and 0.20,the compressive strength of CS system decreases by-0.18%,1.07%,1.32%and the flexural strength of CS system drops by 0.93%,1,67%and 0.15%compared with CO system...