Abstract
Low-noise asphalt mixtures are characterized by increased air void content. Their more open structure contributes to faster degradation within the operating temperature range. For this reason, binder modification is used in their production. The correct selection of modifiers allows one to significantly improve the technical properties of the mixtures. The article presents the results of tests of six types of mixtures: stone mastic asphalt (SMA8), porous asphalt (PA8), stone mastic asphalt reducing tire/road noise (SMA8 LA) and stone mastic asphalt reducing tire/road noise, with 10%, 20% and 30% content of rubber granulate (RG). Bitumen 50/70 modified with copolymer styrene butadiene styrene (SBS) and crumb rubber (CR) was used for the production of the mixtures. In order to determine the differences in the technical properties of the mixtures, the following parameters were tested: stiffness modules by indirect tensile testing of cylindrical specimens (IT-CY) in a wide range of positive temperatures, and resistance to permanent deformation using the British and Belgian methods with the use of double wheel tracker (DWT). The test results and their analysis confirmed that there was a significant improvement in the IT-CY stiffness modules of SBS and CR modified mixtures. Replacing more than 20% of coarse aggregate with RG causes a significant decrease in the stiffness of the mixture (by 90% in relation to the reference mixture SMA8 LA). The SMA mixtures obtained lower values of rutting resistance parameters (WTS and PRD) in water (Belgian method) compared to the results obtained in the air tests (British method). On the other hand, mixtures of PA, thanks to the compression of stresses in pores filled with water, obtained better results when the rutting resistance test was performed in the water (Belgian method).
Highlights
Development of the communication infrastructure and the increase in road traffic volume have resulted in an increase in the noise level generated by motor vehicles in the road surroundings [1]
Based on the tests of the stiffness modulus and rutting resistance of grit mastic mixtures SMA8, SMA8 LA and porous asphalt PA8, with binders modified with styrene butadiene styrene (SBS) copolymer or crumb rubber, or combined modification with SBS and crumb rubber, the following conclusions were formulated: 1. The type of modifier used has a significant effect on the stiffness of asphalt mixtures and their temperature sensitivity confirmed by the change in the value of the stiffness modulus as a function of temperature
The highest increase was obtained at the temperature of 35 ◦C for SMA8 LA mixtures with 10% rubber granulate: by 163% for the binder modified with SBS copolymer, by 92% for the binder modified with crumb rubber and by 104% for the modification with 2% SBS + 10% crumb rubber, compared to mixtures with bitumen 50/70
Summary
Development of the communication infrastructure and the increase in road traffic volume have resulted in an increase in the noise level generated by motor vehicles in the road surroundings [1]. Positive results are obtained with the use of binders modified with the addition of SBS copolymer (e.g., Kraton 1192), CR from used car tires and a combination of these two modifiers [4,5,6] Modifiers of this type contribute to a greater range of viscoelasticity, increasing the softening temperature, improving the resistance to technological and service aging, and increasing low temperature cracking resistance [7,8]. Laboratory tests of stiffness modulus and rutting resistance well characterize asphalt mixtures at positive operating temperatures, and at the same time allow one to assess the quality of the bitumen binders [20,21]. The aim of the presented research to show how the modification of bitumen and the addition of RG change the stiffness modulus and rutting resistance according to the British and the Belgian methods of low-noise asphalt mixtures
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