Investigation of unconfined compressive strength and pore structure of Basalt Fiber Pisha Sandstone cement soil under low temperatures

Abstract

This study explores the relationship between unconfined compressive strength and pore structure in basalt fiber Pisha sandstone cement soil (BF-PSC) subjected to low temperatures. Basalt fibers (BF) with varying mass fractions (0 %, 0.15 %, 0.30 %, 0.45 %, and 0.60 %) were incorporated into Pisha sandstone cement soil (PSC) to formulate BF-PSC. The materials underwent unconfined compressive strength tests and nuclear magnetic resonance (NMR) assessments at ambient temperatures of 20 °C, 0 °C, −5 °C, −10 °C, −15 °C, and − 20 °C. Grey correlation analysis was used to determine the unconfined compressive strength of BF-PSC at low temperatures and to investigate the relationship between strength and pore structure. A prediction model for unconfined compressive strength in low-temperature environments was established. The results show that the unconfined compressive strength of BF-PSC with BF mass fraction of 0.15 % to 0.30 % significantly improves across various ambient temperatures (20 °C to −20 °C), with an optimal BF content of 0.15 %. Additionally, porosity decreases as temperature drops, while the saturation degree of the bound fluid and the percentage of micro pores increase. Grey correlation analysis revealed a strong correlation between bound fluid saturation, microporosity, and unconfined compressive strength. The developed predictive model, based on temperature, BF dosage, bound fluid saturation, and micro pores proportion, achieved a correlation coefficient of 0.963, effectively predicting unconfined compressive strength for BF-PSC with BF mass fractions ranging from 0 % to 0.60 % at temperatures from 0 °C to −20 °C.