Influence of constant strain levels on the viscoelastic properties of asphalt concrete

Abstract

The flexural stresses applied by vehicular movement exhibit a great influence on the viscoelastic properties of asphalt concrete pavement. However, the fatigue life of the flexible pavement is related to the ability of the pavement to sustain the accumulated strain in the pavement structure through the design life of the pavement and it is considered as a good measure of its fatigue life.In the present work, asphalt concrete mixtures were prepared in the laboratory at optimum binder content and compacted in a slab mold using the roller compaction. Beam specimens of 62 mm width, 56 mm depth, and 400 mm length; were obtained from the prepared asphalt concrete slab samples.The beam specimens were tested for fatigue under repeated flexural stresses at 20℃ environments following the constant strain mode of loading. Constant strain modes of three levels have been tried as target amplitude, (750, 400, and 250) microstrain and the implemented loading frequency was 5 Hz throughout the test. The viscoelastic properties of asphalt concrete specimens have been monitored, analysed, and compared. It was noticed that the phase angle of asphalt concrete rises at failure by (33.3 and 50) % when the constant strain level rises from 250 to 400 and 750 respectively. However, the cumulative dissipated energy of asphalt concrete specimens increases at failure by (10 and 24) folds when the constant strain level declines from 750 to 400 and 250 respectively. On the other hand, the fatigue life of asphalt concrete specimens was (6.1 and 141.8) folds higher than that of 750 constant strain level for specimens practicing 400 and 250 constant strain levels respectively. It was revealed that higher constant strain level can exhibit sharper trend of decline in its initial stiffness as compared with the other microstrain levels.

The Role of Dissipated Energy and Stiffness in Enhancing the Fatigue Life of Asphalt Concrete under Environmental Influence

“…Laboratory roller compaction was conducted to the target bulk density according to procedure described by EN12697-33, (2007), [18]. The details of conducting the compaction process can be referred to Sarsam, (2023), [19]. The temperature of the compaction was maintained at 150°C throughout the rolling compaction process.…”