Thermo-mechanical properties of fibre reinforced cement-based foam exposed to sulphate

• Thermal conductivity of cement-based foams was evaluated after exposure to sulphate solution.
• Exposure to sulphates leads to a densification of cellular structure due to the formation of expansive products.
• An initial self-sealing of cells leads to a rise in thermal conductivity, followed by a drop upon expansive cracking.
• Cell closure, crack formation and their subsequent sealing is manifested upon toughness factor and thermal conductivity.

This paper presents the effect of sulphate exposure on the thermal conductivity of cement-based foams and examines their correlation with certain mechanical properties. The study was conducted on cement-based foams with a cast density of 475 kg/m3. Along with a plain mix, another series with polypropylene fibre at 0.2% volume fraction was prepared to investigate the role of flexural toughness on thermal conductivity. The tests were conducted on prisms of cement-based foams immersed in a sodium sulphate solution after specific intervals of exposure. Whereas the flexural toughness was measured based on standard four-point bending tests, a transient plane source (TPS) thermal analyzer was employed to measure thermal conductivity. The microstructure of the exposed specimen was analyzed with the help of scanning electron micrograph and the phases were identified using X-ray diffraction. The results reveal that thermal conductivity increases over the initial stage of sulphate immersion and subsequently drops to a plateau value. This rise-and-fall was mimicked by the flexural toughness factor.