粉煤灰喷射混凝土孔隙结构的演变特征

Evolutionary Characteristics of Pore Structure of Fly Ash Shotcrete

为了寻找长期服役的喷射混凝土配合比,采用低场核磁共振技术,研究了不同粉煤灰掺量改性胶凝材喷射混凝土的微观孔隙结构,测定了不同掺量的粉煤灰喷射混凝土在不同养护龄期的微观孔隙结构分布特征及孔隙度.研究结果表明:掺有粉煤灰的喷射混凝土孔隙度随粉煤灰掺量的增加而增大,随龄期的延长总体呈现先减小后趋于平稳的趋势;粉煤灰掺量为10%时孔隙度最小,掺量为0时孔隙度最大;在7 d龄期后,不同粉煤灰掺量的喷射混凝土内部孔隙半径主要在1~80 nm的范围内,该半径范围内的孔隙含量占总孔隙含量的80%,最可几孔半径在12 nm.

To study the mixture ratio of pore structure in fly ash shotcrete during operation,low-field magnetic resonance imaging technology was adopted. The micro-pore structure of the modified cementitious shotcrete with different fly ash content was investigated. The micro-pore size distribution characteristics and porosity of shotcrete with different fly ash content,at different curing phases were measured. The results show that the porosity of the fly ash shotcrete increases with an increase in the fly ash content; however,with increase in the curing age,the porosity generally decreases first,and subsequently tends to be stable. The results also indicate that the value of porosity is minimum and maximum when the amount of fly ash is 10% and 0,respectively. After the 7-day healing period,the inner pore radius of shotcrete varies from 1 to 80 nm for different proportions of fly ash. In such a radius range,the value of micro-pore is 80% of the total fissure value. The most probable pore radius is approximately 12 nm.