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通过压汞试验研究了粉煤灰掺量对混凝土孔径分布的影响规律,从气体在混凝土中的扩散机理出发,并结合压汞试验结果研究了粉煤灰掺量对气体O2及CO2在粉煤灰混凝土中扩散能力的影响.结果表明:粉煤灰等量取代水泥达45%时,混凝土总孔隙率、有害孔及多害孔(孔径>50 nm)的分孔隙率、最可几孔径及平均孔径均明显增大;O2及CO2气体在普通混凝土及粉煤灰混凝土中扩散时,在大多数孔隙(80%以上)中扩散属于过渡区扩散;在同等条件下气体CO2在粉煤灰混凝土中的扩散能力较气体O2差;由于粉煤灰掺量对过渡区扩散孔分孔隙率占总孔隙率比值影响不大,导致粉煤灰掺量即使达到45%时对气体的有效扩散系数增大幅度不足10%.
The effect of fly ash content on the pore size distribution of concrete was studied by mercury injection test. Based on the diffusion mechanism of gas in concrete and the results of mercury intrusion test, The results show that when the equivalent amount of fly ash is replaced by 45% cement, the total porosity, harmful porosity and multi-pore damage (pore size> 50 nm) are divided by porosity, most probable pore size and The average pore diameter obviously increases. When O2 and CO2 are diffused in ordinary concrete and fly ash concrete, diffusion in most of the pores (above 80%) belongs to the diffusion of transition zone. Under the same conditions, the gas CO2 in fly ash concrete In the diffusion capacity is worse than the gas O2; as the fly ash content of the transition zone diffusion porosity fraction of the total porosity ratio has little effect, resulting in even when the fly ash content reached 45% of the effective diffusion coefficient of gas increased Significantly less than 10%.