Paper by DURAN LOWKE MANNEL CALIS GEHLEN from ISCR 12th 2014 Prague Czech Republic
Concrete pavers are often used for construction of urban area roads as they offer both easy and fast construction as well as high aesthetical value. Although noise reduction is also very important in urban areas, research focusing on low noise concrete pavers is still rare. This paper illustrates a study for optimizing aggregates pore distribution for porous concrete pavers in view of noise reduction. As a first step packing density and void ratio of typical granulometric fractions and mixes of these were experimentally determined. The results showed good correlation to analytical calculated packing densities. Afterwards sound absorption curves were determined for each mix by means of an impedance tube. Among others, the test results demonstrated an increasing sound absorption coefficient by increasing void ratio. Probably particle shape had influence on packing density and sound absorption of the mixes. For studying the effect of void ratio and fineness of voids on sound absorption this influence had to be eliminated. Therefore packing density and sound absorption of spherical glass beads were analyzed. Mixes of single grain sizes and mixes of two grain sizes were analyzed. The results showed that for mixes of single grain sizes the fineness of the voids of the mix affects significantly the acoustical properties of the mix. In mixes of two grain sizes the voids fineness have bigger effect than the void ratio on acoustical properties. These findings were then transferred to mixes of closely sieved aggregates following previous tests. Concluding results could be corroborated on porous concrete mixes with different grain-size distribution curves. The results of this study enable the design of porous concrete mixes ensuring good sound absorption so the design can focus also on other concrete properties like strength and durability.