Asphalt concrete based on bituminous polysulfide binder, designed according to the volumetric method
The purpose of this study is the development of new asphalt mixes in the system of volumetric - functional design, using bituminous polysulfide binders (hereinafter - BPV) in their composition. Research methods. At the first stage, research was carried out on the BPV of various grades to determine the brittleness temperature by the Fraas method and the softening temperature using the ring and ball method. At the second stage, studies of BPW were carried out in order to establish its compliance with the requirements for binder grades according to PG. The following indicators were determined: flash point using the Cleveland open crucible method; dynamic viscosity, which is defined as the ratio between the applied shear stress and the shear rate of the bituminous binder; shear stability using the DSR dynamic shear rheometer, the method of determining which is to evaluate the shear stability of the bituminous binder by oscillating shear deformation of the sample and determining the values of the complex shear modulus and phase angle; bitumen and determining the effect of this impact on bitumen by comparing the physical and chemical parameters of bitumen obtained before and after exposure; aging temperature according to the PAV method, which consists in exposing samples of bituminous binders to elevated temperature and pressure in order to simulate aging processes during a period of operation in the pavement from 5 to 10 years; fatigue resistance, which is determined on a bituminous binder aged by the PAV method; low-temperature resistance, the method of determining which is to evaluate the low-temperature properties of the bituminous binder by determining the complex shear modulus in the frequency range at different temperatures and determining the stiffness values S(t) and the parameter m. At the final stage, the compositions of the asphalt concrete mix were selected and tests were carried out for resistance to rutting by rolling a loaded wheel over a test sample at the required temperature and determining the rut depth after 10,000 load cycles (20,000 wheel passes) or until the limit value was reached. Results. Synthesized organic polysulfides based on sulfur and mixtures of higher fatty acids (hereinafter referred to as PS). The softening temperature of BPV with a polysulfide content of 25 and 40 wt.% is 50 and 54°C, and the brittleness temperature is -22 and -25°C, respectively. The combination of bitumen with PS makes it possible to obtain binders of a new composition with a set of property indicators corresponding to grades PG 58-40 and PG 52-34. The compositions of the SP-16 asphalt concrete mix based on industrially produced and bitumen-polysulphine binders have been selected. Comparative tests of asphalt concrete were carried out to determine their resistance to rutting by rolling a loaded wheel. It has been established that the depth of the rut of the control composition on the binder PG 70-28 is 1.26 mm, on bituminous polysulfide binders, depending on the content of polysulfide, it varies within 1.87 ... 2.62 mm. The obtained values of indicators meet the requirements of regulatory documents. It has been established that the introduction of polysulfide into bitumen makes it possible to lower the lower temperature limit PG of the binder, to increase its softening temperature and the upper limit PG, respectively. The rut depth indicators of asphalt concrete on BPV meet the requirements for asphalt concrete used in extreme and difficult conditions.