Study On The Preparation Of HPC Using High Belite Cement

R&D of high strength HPC with strength grade C50 - C80 was conducted using high belite cement (abbreviated as HBC) as the main component of cementitious material. The workability, physical mechanical properties, durability and sub-microstructure of HBC concrete have been researched systematically in comparison with HBC using ordinary Portland cement (abbreviated as OPC). The resultant HBC concrete possesses the properties of initial slump>180mm,slump loss at 90min< 40mm,freeze resistance grade>F300,permeability resistance grade>W25 and Cl- penetration value <1000 coulom and the following research results have been obtained.1. The results of research on the workability of HBC concrete show that HBC concrete, when compared with OPC concrete, has excellent compatibility with superplasticizer, in terms of better initial fluidity, less slump loss, definite saturation point and less dosage at saturation point. In addition, good mineral admixture such as I class fly ash can obviously improve the workability of HBC concrete. Moreover, HBC concrete exhibits more excellent workability under the condition of low w/c ratio, which indicates HBC is more suitable for making super high strength concrete whose w/c ratio is very low.2. The research results indicate that the physical mechanical properties of HBC concrete such as compressive strength, flexural strength, splitting tensile strength, elasticity modulus and etc. is equivalent to that of OPC concrete at age of 28d and remarkably surpasses OPC concrete at 90d though its early age strength (3d, 7d) is relatively lower. Moreover, the relation of w/c ratio of HBC with compressive strength as well as strength at 7d with 28d (C50 - C80) has been established and the effect of the dosage and type of fly ash on compressive strength of HBC has also been studied.3. The results of research on durability of HBC concrete including resistance of freeze-thaw, permeability, carbonation, corrosion as well as shrinkage and sub-microstructure structure exhibit HBC concrete has good properties of freeze-thaw resistance, permeability resistance, carbonation resistance, corrosion resistance and less shrinkage compared with OPC concrete.4. The study on pore structure shows that the incremental pore size of HBC concrete (3d, 7d) is relatively larger, approximately equivalent at 28d, but smaller at 90d and180d compared with OPC concrete. The harmful pore of both HBC and OPC concrete decreases sharply but little harmful and harmless pores increase greatly, especially the harmless pore whose pore size is less than 20nm for HBC concrete increases much more than OPC concrete, which can explain why HBC concrete possesses excellent long term properties.