Study on Mechanical Properties and Microstructure characteristics of Fly Ash Mixed Wet Shotcrete under Low Temperature Curing Environment

Abstract

To systematically examine the mechanical properties and microstructure of fly ash-doped wet shotcrete under low-temperature curing conditions, experimental studies were conducted on the compressive strength. The investigations encompassed varying activator dosage, fly ash dosage, and curing temperature for a thorough examination of the material’s performance. The results show that the addition of activator can significantly improve the compressive strength of fly ash wet shotcrete under low temperature curing, but the optimal dosage of different activator types is not consistent. The selection of NaAlO2 as the activator has the most significant effect on the compressive strength of the samples. Under low temperature curing environment, the increase of curing age can also significantly improve the compressive strength of the sample, especially the early strength. The order of influence degree of three factors on compressive strength is that alkaline activator has the highest influence degree, curing temperature has the second, fly ash content has the least influence degree, and activator content is the significant influence factor of early compressive strength. A prediction model for the compressive strength of wet shotcrete doped with fly ash was established in the low temperature curing environment, and the effect of increasing the dosage of activator on the compressive strength of the sample increased with the decrease of curing temperature. With the increase of the content of activator and curing temperature, the size of the void structure in the sample is gradually reduced, which makes the density of the microstructure gradually increase, and thus improves the macroscopic compressive strength of the sample.