Experimental investigation on fractal characteristics of pores in air-entrained concrete at low atmospheric pressure

摘要

This study intends to investigate the characteristics of pore structure of air-entrained concrete at low atmospheric pressure (0.7P(0) = 0.7 atm) and standard atmospheric pressure (P-0 = 1 atm) through in situ experiments. By using the data obtained from mercury intrusion porosimetry (MIP) test, the surface fractal dimension in different pore size regions is computed and linear regressed based on thermodynamic model. The results show that low atmospheric pressure has great impact on the fractal properties of pores and pore volume. The surface fractal dimension of pores <10 nm prepared at 0.7P(0) is 4.5%-27.6% smaller than that at P-0; the surface fractal dimension of pores 10 nm and 1000 nm at 0.7 P0 is respectively 9.4%-38.9% and 38.5%-66.7% lower than that at P-0; and the volume of pores within 10-1000 nm at 0.7P(0) is 19.8%-41.8% higher than that at P-0. The mechanisms behind the abnormal structure of pores at 0.7P(0) are discussed from perspectives of cement hydration and mechanical equilibrium of air bubble.

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