Due to the different microstructures of the samples, large differ- ences were observed in their porosity values. This diversity is very interesting because it can provide very different porous micro- structures and consequently different acoustical properties. This porosity is distributed between pores of different sizes (ranging from 1 lm to 1 cm) into and between the particles and in the bin-
der. The values obtained are shown in Table 1. The porosity de- creased with the increase of the binder concentration. Sample M1 presented higher values of porosity because of the composition of the composite. Vermiculite and EPS contributed to the porosity with micropores, and their presence resulted in the increased over- all porosity of the granular mix. The GTR grain size and binder in Sample M2 determined the value of its porosity. Samples M4 and M5 presented a similar porosity attributed to a relatively high pro- portion of larger grains in the mix. The other samples had low porosity because the voids between individual grains were filled by the binder.