Thermal insulation and acoustic absorption performance of textile fibre-reinforced cement mortars

Textile fibres show significant potential for the enhancement of the thermal insulation and acoustic absorption properties of fibre-reinforced mortars. However, studies on how different fibre types, especially clothing fibres, affect mortar microstructure and related performance remain limited. This study investigates the effects of polyester, cotton, nylon, and elastane fibres on the thermal conductivity, sound absorption, and compressive strength of cement mortars. Fibre parameters, including volume fraction (0.25 %, 0.5 %, and 1.0 %) and length (6, 12, and 18 mm) were systematically varied to characterise performance using Grey Relational Analysis. The best-performing mixes at 28 days were analysed using micro-computed tomography, scanning electron microscopy, and nanoindentation to assess microstructural changes. Elastane fibres at 0.5 % volume and 12 mm length demonstrated the best overall performance, reducing thermal conductivity by 62 % and giving a 21 % increase in peak sound absorption coefficient at 856 Hz. Moreover, compressive strength increased to 39.65 MPa (from 39.21 MPa in the control mix). Microstructural analysis revealed that elastane increased total porosity by 43.4 % compared to the control, yet compressive strength was maintained. This is attributed to elastane's high elongation capacity (519 %), which enables dual functionality: air entrapment for improved insulation and stress distribution to mitigate cracking. Other fibres demonstrated varying performance in mortars. 18 mm nylon fibres at 0.25 % volume yielded the highest compressive strength (42.27 MPa). Cotton fibres (6 mm, 0.5 %) reduced thermal conductivity by 48 % without compromising strength, while polyester fibres lowered it by 47 % but reduced compressive strength by 15.3 %. Based on mechanical and insulation performance, elastane-reinforced mortars at 12 mm (0.5–1.0 %) and 18 mm (0.5–1.0 %) meet Class II standards set by the International Union of Laboratories and Experts in Construction Materials, highlighting their potential for sustainable, structural, and insulating applications using textile waste. • Nylon fibres of length 18 mm and 0.25 % dosage reduced mortar porosity by 11 %. • Peak sound absorption occurred between 800 and 1000 Hz for all fibre reinforced mortars. • Elastane fibres increased porosity of mortar by 43.4 % without compromising strength. • Elastane fibres reduced thermal conductivity of mortar by up to 66.7 %. • Elastane fibres of 12 mm length and 0.5 % dosage showed both insulation and structural benefits.