Evolutionary Characteristics of Pore Structure of Fly Ash Shotcrete

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.