Freeze-thaw resistance of basalt fiber reinforced foam concrete

Uniaxial compression-acoustic emission combined tests were conducted on basalt fiber reinforced foam concrete specimens (BFRFC) with different densities (600 kg/m³ and 1000 kg/m³) and fiber admixtures (0, 0.15%, 0.30%, and 0.45%) under the conditions of 0, 25, 50, and 75 freeze-thaw cycles. And based on the distribution law of acoustic emission RA-AF values, the b-value change curve as well as three macroscopic freezing performance indexes (water absorption, mass loss rate, and relative dynamic elastic modulus), the damage characteristics and freezing performance change rule of each grade of BFRFC under freeze-thaw environment were investigated. The results show that the stress-strain relationship curves during uniaxial compression of BFRFC have obvious stages. Freezing and thawing cycles lead to a decrease in the overall strength of the specimen, accelerated cracking, and an increase in the percentage of internal shear damage, whereas increasing both the basalt fiber doping and the material density can increase the peak load carrying capacity of the specimen (up to 11.14 MPa, 10.20 MPa, 8.741 MPa, and 7.498 MPa under 0, 25, 50, and 75 freezing and thawing cycles, respectively), inhibit the loss of the peak strength (up to 17.9%), increasing the percentage of tension damage (up to 32.4%) and delaying specimen damage. In addition, with the increase of the number of freeze-thaw cycles, the water absorption and mass loss rate of BFRFC increase, and the relative dynamic elastic modulus decreases. In contrast, the water absorption and mass loss rate of high-density and high-fiber doped BFRFC are smaller, the relative dynamic elastic modulus is larger, and the mass loss rate and relative dynamic elastic modulus can be kept below 3% and above 70% respectively under 75 freeze-thaw cycles, which has better frost resistance.