Influence Of BSF Admixture On The Performance Of Concrete

In order to use BSF compound mineral admixture material(a mineral admixture prepared by mixing waste brick powder,granulated blast furnace slag powder and fly ash,and adding a small amount of modifier)in pavement concrete,in this paper,C35 pavement concrete was prepared by partially replacing cement with this kind of admixture material,the early shrinkage performance of C35 pavement concrete,the effect and mechanism of BSF admixture on the performance of concrete were investigated.Calcium and magnesium based materials were employed to compensate the shrinkage of concrete,and the mechanics,shrinkage and frost resistance properties of concrete after shrinkage compensated were investigated also.The experimental results showed that: Although waste brick powder and fly ash could compensate the shrinkage of concrete slightly,the use of GBFS caused the shrinkage of concrete greatly,the comprehensive effect of the application of BSF mineral admixture was that the shrinkage of concrete was aggravated remarkably.When the dosage of BSF was less than 10%,the compensating shrinkage effect of brick powder and fly ash appeared to dominate,the concrete exhibited good volume stability.Once the dosage of BSF was more than 20%,the contraction effect of GBFS dominated,and the shrinkage of concrete was exacerbated.calcium and magnesium expansion agent could compensate the shrinkage of concrete effectively,because of volume expansion caused by calcium hydroxide and magnesium hydroxide generated from the hydration of calcium oxide and magnesium oxide contained in the expansion agent.When the content of expansion agent was no more than 5%,the mechanical properties of concrete were enhanced.When the content of expansion agent was no more than 10%,the frost resistance performance of concrete were improved also.The effect of magnesium expansion agent on the frost resistance of concrete was better than calcium expansion agent.