Thermal insulation and high-temperature resistant cement-based materials with different pore structure characteristics: Performance and high-temperature testing

Pore structure is a key factor affecting the fire resistance of cement-based fireproof materials. In this study, a heat-insulating and heat-resistant cement-based material (PABC-perlite-aerogelbasalt-cement) was prepared by adding expanded perlite (EP), SiO2 aerogel (SA), basalt fibre (BF) and standard sand as raw materials. Ether defoaming powder (DP) was subsequently added to improve the pore structure of PABC by decomposing and eliminating air bubbles to increase its fire resistance. The physical, thermal, mechanical and microstructural characteristics of PABC before and after temperature treatments of 20 degrees C, 200 degrees C, 400 degrees C, 600 degrees C, and 800 degrees C with different DP dosages were analysed to better understand the working mechanism of DP and the mechanism by which DP indirectly slows the high-temperature deterioration of PABC. The results revealed that increasing the DP dosage decreased the porosity and effectively improved the 28 d compressive strength and tensile strength of PABC, which reached 38.35-47.74 MPa and 2.50-2.84 MPa, respectively. Moreover, the coefficient of thermal conductivity of PABC was 0.31-0.7 times lower than that of ordinary cement mortar. The specimen surfaces did not exhibit any bursting after high-temperature calcination, and the porosity of the specimens increased with increasing temperature. Small pores gradually decreased, whereas large pores and oversized pores gradually increased, and the pore structure deteriorated. In particular, at a calcination temperature of 600 degrees C, the internal steam pressure owing to excessive implosion effect (R2D6), compressive strength and tensile strength of the specimens significantly decreased. Furthermore, with an appropriate pore structure (R2D1), the internal steam pressure was fully released. After calcination at 800 degrees C, the specimen still exhibited a compressive strength of 5.60 MPa and a tensile strength of 0.99 MPa, which enhanced the fire-resistant properties of PABC. DP plays an important role in regulating the pore structure characteristics to alleviate the high-temperature deterioration of PABC.