Enhanced acoustic properties of concrete composites comprising modified waste sheep wool fibers

Sheep wool is an environmentally friendly, renewable, and entirely recyclable resource that satisfies the standards of green building components. Consequently, it is increasingly employed in building material technology. The sound absorption characteristics of sheep wool render it a satisfactory building insulation material with desirable acoustic properties. This study investigates the effect of waste sheep wool fiber (WF) and modified WFs (MWF) on the acoustic and mechanical properties of concrete. Plain concrete and concrete mixtures containing 0.5–2.5% WF and MWF were tested for compressive strength, modulus of elasticity (MOE), ultrasonic pulse velocity, sound absorption, and transmission loss. The addition of WFs to concrete mixtures slightly reduced the compressive strength and MOE values. However, it significantly improved the sound insulation and noise reduction behavior of concrete specimens, with sound absorption coefficients of 0.66 and 0.75 for mixtures containing 2.5% WF and MWF, respectively, at a frequency of 2000 Hz. In general, the addition of WFs to concrete composites improved their overall acoustic qualities. The findings showed that sheep wool waste, as a sound insulation material, has acoustical properties similar to those of polymeric-based fibers, with the added advantages of being environmentally friendly, affordable, biodegradable, and abundant.