Effect of Concrete Thickness and Expanded Polystyrene Layer on Stiffness and Floor Impact Sound Insulation Performance of Cross-Laminated Timber Slabs

This study aimed to investigate the effects of an expanded polystyrene (EPS) layer and varying precast concrete thickness on the stiffness and acoustic performance of cross-laminated timber (CLT) slabs. Six different concrete thicknesses and EPS layers were applied to larch and pine CLT slabs for testing. Airborne sound transmission loss (Dw) was measured using speakers, light impact sound (LnT,w) using a tapping machine, and heavy impact sound (LiA,Fmax) using rubber balls, in accordance with KS F ISO717-2. The results indicated that the EPS layer significantly improved light impact sound insulation (by 8 dB) and airborne noise insulation (by 5 dB), but had a minimal effect on heavy impact sound (0.5 dB). Both stiffness and sound insulation increased with concrete thickness, although improvement plateaued beyond 100 mm for larch CLT and 150 mm for pine CLT. The flexural and impact stiffness of larch CLT slabs were 24.3% and 19.2% higher than those of pine CLT slabs, respectively. Moreover, impact stiffness demonstrated a stronger correlation with acoustic performance than the previously established relationship with area density.