Mix design of C60 porous coarse aggregate high performance concrete
In order to reduce the cost of high performance concrete(HPC),different types of aggregates are often used to partially or completely replace ordinary sand and gravel.However,there are few studies on the preparation of HPC by porous coarse aggregate.In this paper,5~10mm porous coarse aggregate is used to replace ordinary stone to produce HPC.Under low water-binder ratio,coarse aggregate was difficult to mix due to its rich pores,so additional water is used to wet coarse aggregate in advance.Based on the orthogonal test of 4 factors and 4 levels,the effects of different factors on the working performance and mechanical properties of concrete are studied.The mix ratio of porous coarse aggregate HPC is optimized by Design-expert software.The results show that When the water-binder ratio is 0.28,the binder-aggregate ratio is 0.51,the sand ratio is 42%,the amount of water reducing agent is 0.2%and the additional water consumption of aggregate is 7.618%~7.973%,HPC with compressive strength ≥ 60MPa and flow expansion ≥ 500mm can be prepared by using porous coarse aggregate.The most influential factors on compressive strength and expansion are sand ratio and aggregate additional water consumption.The empirical formulas of compressive strength and expansion degree are proposed.The microscopic analysis of the optimized specimen shows that the porous coarse aggregate after water absorption has a certain internal curing effect,the combination of slurry and aggregate is high,and the internal pores of concrete are mainly harmless and less harmful pores,which ensures the strength of the specimen.