Rubberized Asphalt
with			used in
St. Petersburg, Russia to reduce noise
In St. Petersburg, Russia in 2018 the Western High-Speed Diameter (WHSD), a strategic investment project of the city, is developing a major world-class transportation hub to improve the quality of life experience by reducing traffic noise from the pavement surfaces. The WHSD is a 46-kilometer highway consisting of three sections and connecting the north and south of St. Petersburg.
Photo by Samuel Wolfgang Moroder from Wikimedia
To this end WHSD engaged the services of DSK Dorstroy the business unit of the ABZ-1 Group of Companies to propose a solution (www.abz-1.ru). The traditional open graded hot mix solutions to reduce noise have not been cost effective in Russia because of the cold weather usage of studded tires that wear out that kind of surface prematurely.
Photo by  Ninaras from wikimedia Commons
The challenge was to find a mix with low air void content (2 percent or less) yet capable of providing cost effective noise reduction, good rut and wear resistance and wet friction property. Maidanova Natalia, PhD, Deputy Director for Quality, Head of the Research Center ABZ1 proposed the use of an asphalt hot mix with rubberized asphalt with RARX (www.rarx.net) which combines the benefits of the dry and wet process of asphalt rubber, thus allowing greater amounts of ground tire to be incorporated in the hot mix. RARX is reacted and activated rubber which can be placed directly as a dry powder into the pugmill of the contractor’s plant.
Under Dr. Natalia’s direct supervision several mixes were formulated and tested in laboratory; “The task that the customer has set is to reduce the noise from moving vehicles along the highway. The highway passes through the city, sometimes near residential areas. The second task is to reduce the wear of the coating from the impact of studded tires. To solve these problems, compositions with RARX and with additives of super wear-resistant mineral compounds were developed”
Mixes A and D were selected as they exhibit some different but important excellent performance in some key indicators. For instance, RARX-SMA 16 has the highest tensile strength at -18 ⁰C. While RARX-THINGAP+Abrasive had the best rutting resistance. Both mixes had great wear resistance in the Prall test. CONSULPAV (www.consulpav.com) under the support of SILENT RUBBER PAVE project (silentrubberpave.eu) provided technical input to this project. The 25 tons of RARX required for this job was supplied by CIRTEC (www.cirtec.es). The demonstration projects with MIX A (RARX SMA16) and Mix D (THING GAP RARX + Abrasive) were built October 13th, 2018. Air temperature was 15 ⁰C!!! The layer thickness was 5 cm for MIX A and 4 cm for MIX D. “The temperature of the mixture in the machine is 182 ⁰C, after Shuttle-Bag when it is loaded into the stacker 165 ⁰C, after the plate of the stacker 164 ⁰C, after 2 passes with a steel roller Hamm 90 – 157 ⁰C, after 4 passes -151 ⁰C, after passes 6 – 145 ⁰C, after 8 passes – 139 ⁰C. After 8 passes reached compaction. The mixture did not stick to the rollers”.
In the photo, from left to right, Dr. Natalia, Mikhail Kalinin, the Director of ABZ-1 OJSC (business unit of ABZ-1 Group of Companies), produced the mixes at their asphalt plant, and Kirill Melnik, Head of the Laboratory. Everyone is very happy to have a successful demonstration project that took place on fantastic weather day. The last time that St. Petersburg felt 15 ⁰C on October 13th was 120 years ago! Nevertheless, she acknowledges that the stakes are very high. Traditional wisdom dictates that to resist studded tires large particles aggregates must be used. Meanwhile tradition wisdom also dictates that to reduce noise small particle size mixes should be used combined with more open graded gradation. The compromises made towards improving noise reduction may affect durability regardless how good Prall test results appear to indicate. The combination RARX with high quality abrasives has never been tried before! “In a year or two we will be able to ascertain the cost benefit of these innovative solutions with RARX”. No noise evaluating CPX tests have been done yet. However, Dr. Natalia’s expression after driving over the section was: “Drove over the overlay by car at a speed of 110 kilometers per hour. Noise from the wheels significantly lower !!!!” I guess you can be the judge of the effectiveness of these RARX-SMA and RARX-THINGAP in noise reduction. In the video below, they are the blacker surface on the left lane that appears around the 34th second into the video (turn up the sound to listen, you will listen to the noise difference between regular and the new RARX sections).
I think St Petersburg has just made the very first step into improving the St Petersburg quality of life. We acknowledge the contributions made by Dr. Maidanova Natalia, Deputy Director for Quality, Head of the Research Center ABZ-1 to this article.
		Dr. Jorge B. Sousa Director Rubberized Asphalt Foundation Jorge.B.Sousa@gmail.com