Impact of varying basalt fibre size on the acoustical properties of low carbon concrete

• The absorption coefficients and transmission show the basalt-fibre infused concrete samples behave like resonators. • Varying basalt-fibre size impacts the absorption mechanism of concrete samples. • Very good agreement between measurements and computational results. • Basalt-fibre acts as a damper in concrete leading to reduction in sound transmission. • Perforation increased absorption and shifted maximum absorption to higher frequency. The impact of varying basalt fibre size and perforating concrete samples was investigated to improve the acoustical properties of low-carbon concrete. The research was focused on how the length and quantity of basalt fibres and perforation of samples could influence sound absorption and transmission, with an intention to apply them as sound reflectors and sound absorbers. Concrete samples both with and without perforations were designed and created. Their sound absorption coefficient and transmission loss values of the samples were measured applying transfer function method in a circular metal impedance tube. Two-Dimensional (2D) computational simulations were carried out on periodic perforated material that are mimicking perforated concrete samples to determine their sound transmission loss values and absorption coefficients applying the thermo-viscous acoustics, pressure acoustics, and solid mechanics models in COMSOL Multiphysics software. Computational results matched up well with the experimental results for perforated materials in one-third octave bands. The results reveal that varying basalt fibre size and quantity of them within materials significantly influences the sound absorption mechanism of the concrete causing the samples to behave like resonators around their natural frequency. Introducing perforations into samples enhanced sound absorption performance and moved the peak absorption to higher frequencies. However, the increase in sound absorption came with a trade-off, decreased sound transmission loss, meaning more sound passed through the perforated samples. Finally, the average sound absorption coefficients and transmission loss values of the basalt fibre reinforced samples were compared to those of glass-bead samples and to the concrete samples without basalt fibre infusion. The results clearly showed that adding basalt fibres to concrete boosted sound absorption coefficient and the frequency at which the peak sound absorption occurs was shifted to lower frequencies.