Thin-layer pavement layers of Broken Rock-Mastic Asphalt Concrete ЩМАс-5
With the exception of network of Federal and Regional Highways, the public motor roads of Tatarstan Republic have low traffic intensity and density of freight traffic. Judging from that, the main reason for destruction of these roads‘ covering is not the insufficient load-carrying capacity of the roadway covering structure, but the ageing, shortening of the life cycle of the upper-most layer due to climatic influences such as high and low ambient temperature, humidity, sun radiation etc. These problems might be solved through the use of Broken Rock-Mastic Asphalt mix for creation of upper paving layer, which protects the structural layers of pavement from exposure to environmental aggressive factors, provides for the additional rigidity of structure and, consequently, extends the service life of the motor road between the repairs.
Taking into account advantages of Broken Rock-Mastic Asphalt mix and recent demand for reducing the cost of paving layers for the motor roads with low traffic intensity (Category IV - V) while satisfying the necessary operational requirements, we suggested for creation of the upper paving layer to substitute the dense fine-granule Asphalt Concrete mix of the Type B, 2-M with 4 cm thickness with thin-layer paving of ЩМАс-5 mix (thickness of 2 cm). This led to 12% reduction of the cost of the pavement compared to the conventional solutions.
ЩМАс-5 is a separate variety of Broken Rock-Mastic Asphalt Concrete. It differs in composition and usage from other types of mixes. Its composition comprises grains of over 5 mm in size constituting 15 – 20 % of the total mass, needed for providing the necessary roughness of the asphalt concrete surface. What especially differs this mix from other types is the inclusion of special type of mineral material – fractioned sand with grains from 2.5 to 5 mm (produced when crushing rock), which constitutes 60 – 70 % of the mix mass.
Structure of ЩМАс-5 provides for optimal combination of maximal rigidity under compression and shearing with excellent compliance and high deformation under tension. These rheological characteristics are especially important to provide for resistance to shearing and cracking of the pavement under the conditions of strain and deformation of the construction layers of the motor road. The above physico-mechanical properties give the ЩМАс-5 significant advantage over the conventional asphalts.
Creation of thin-layer paving with this mix was performed on the following sites: