Development of sound-absorbing pervious concrete for interior applications

This study focuses on the development of sound-absorbing pervious concrete, aiming to find the most advantageous composition for manufacturing interior sound-absorbing cladding panels. 29 compositions were manufactured to analyse the impact of aggregate gradation and type, cement amount, water-cement ratio, and incorporation of silica fume, superplasticizer, and polypropylene fibres on the sound absorption coefficient. Different aggregate sizes and their combinations within the range 0-8 mm were examined, mostly for mixed construction aggregate and silica sand; however, the impact of pumice, lightweight clay aggregate (Liapor/ceramsite) and recycled concrete aggregate was also studied. The cement amount used in the samples varied between 200 and 400 kg m-3, the water-cement ratio between 0.22 and 0.4, the silica fume substitution between 5 and 15 wt% of cement, and the superplasticizer share between 0.5 and 1.5 wt% of cement. Bulk density, flexural strength, compressive strength, and sound absorption coefficient were measured. The sound absorption coefficient was examined for 20 mm thick samples in two impedance tubes using the transfer function method; the monitored frequency range was 100-4000 Hz. For each sample, its noise reduction coefficient (NRC) and weighted sound absorption coefficient alpha w were calculated. The best acoustic results in this study were measured for samples containing pumice aggregate 3-7 mm, reaching NRC equal to 0.7 and alpha w to 0.55. However, the most advantageous samples satisfying the minimum set mechanical requirements while keeping promising sound absorption were those containing mixed construction aggregate of size 4-8 mm, W/C equal to 0.22, and with the addition of superplasticizer and silica fume.