Evaluating the effect of asphalt binder modification on the low-temperature cracking resistance of hot mix asphalt

This study focused primarily on the effects of various polymer modifications on the low-temperature cracking performance of asphalt binders and resultant mixtures. Two air-blown bitumens were blended with four polymers with or without the addition of polyphosphoric acid (PPA). The low-temperature properties of the neat bitumens and the modified binders were characterized using bending beam rheometer (BBR). The prismatic samples of dense graded asphalt mixtures with the same content of different binders of 4.7% by weight were tested on direct tension at constant strain rate. The low-temperature cracking of the mixtures was also evaluated by tensile stress restrained specimen test (TSRST). The results indicated that the low-temperature parameters were dependent on base bitumen and on polymer modification. For all tested binders, the Superpave criterion E0.30. Polymer modification showed significant benefits as compared to the corresponding base bitumen for direct tensile strength of asphalt mix at low temperatures. Addition of PPA reduced the strength at −30°C while raised at −20°C and −10°C. The BBR limiting binder stiffness temperature was close to the TSRST critical asphalt mix cracking temperature. Keywords: Asphalt pavement, Polymer modification, Thermal stress, Low-temperature cracking, Tensile strength, Critical temperatur

nanostructured bitumen with nanocarbon

Physical and chemical indicators of bitumen quality of grade BND 70/100 with the added carbon nanopowder 2% by weight have been studied by laboratory test methods and analysis. High reaction ability of nanopowder particles and concentration of excess surface and internal energy in them have been determined, which provide the increase of low-temperature resistance, aggregate strength, and improvement of rheological properties of nanostructured bitumen. Essential structure variation has been proved: the increase of asphaltenes and oils content for 9% and 7.2% respectively due to the decrease of resins for 16.2% by weight. Methods have been discussed for preparing a liquid nanocarbon mix, adding of the mix into bitumen and homogenization of the bitumen. Some economic indicators have been represented which influence essentially the reduction for the cost value of the nanostructure bitumen

Temperature in pavement and subgrade and its effect on moisture

This paper gives the results of experimental research of temperature variation and its effect on distribution of moisture in pavement and subgrade of a highway located in the eastern region of Kazakhstan. The sensors consisting of two elements have been used to measure temperature and moisture. The first of them is designed for measurement of temperature and based on the effect of thermal resistance, and the second one based on diamagnetic penetration allows measuring of moisture. Peculiarities of temperature variation in time in pavement layers and points of subgrade, temperature distribution in the depth at different time moments have been described. Important characteristics have been determined – duration of a frozen condition and freezing, average rates of freezing and defreezing in points of pavement and subgrade located in various depths. Quantity of unfrozen water in subgrade soil depends on negative temperature and initial moisture and it is satisfactorily approximated by semi-logarithmic function. Keywords: Pavement, Subgrade, Sensors, Temperature, Moisture, Unfrozen wate

MECHANICAL CHARACTERISTICS OF ROAD COMPOUNDED BITUMEN AT LOWTEMPERATURES

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