Abstract
At intermediate service temperatures hot mix asphalt (HMA) concretely are subjected to different loading rates due to movement of vehicles which can significantly affect their mechanical characteristics and final service load. Hence, in this paper the effect of loading rate on intermediate temperature fracture resistance of HMA materials is investigated experimentally in different modes of cracking. Different hot mix asphalt mixtures made of various compositions were subjected to asymmetric threepoint bend loading in the form of edge cracked semi-circular bend (SCB) specimens. The effect of aggregate type and air void were studied on the fracture energy values for three mode mixities (including pure mode I, mixed mode I/II and pure mode II) and at different temperatures of 5°C, 15°C and 25°C. Trends of change in fracture energy values revealed noticeable influence of loading rate on the low and intermediate temperature cracking behavior of tested asphalt mixtures with different air void contents and aggregate types subjected to mixed mode I/II loading. Also, a change observed in fracture resistance of asphalt mixtures at nearly zero (5°C) and intermediate temperatures (25°C) that was due to change in the behavior of bitumen from elastic to viscoelastic.
Highlights
B y changing the service temperature in the asphalt concrete layers, visco-elastic behavior of bitumen may result in different performances for asphalt mixtures
Using strain Energy as the total energy consumed in global system on specimens to overcome the fracture resistance of asphalt mixes is accepted in this research and used to investigate characteristic specification of various asphalt mixtures under different loading conditions
The fracture energy of each sample was determined from Eq 1 using the area under load-displacement curve until peak load obtained from each fracture test
Summary
B y changing the service temperature in the asphalt concrete layers, visco-elastic behavior of bitumen may result in different performances for asphalt mixtures. Various fracture models have been considered for different characteristics of asphalt mixtures, but such models are generally suitable for low temperature testing conditions, in which the type of fracture is dominantly linear and elastic These models can not necessarily provide predictions for accurate inelastic nonlinear viscoelastic fracture behavior which usually occurs at intermediate temperatures [13,14,15]. The experimental procedure used for determining intermediate-temperature cracking resistance of AC mixtures was developed by Wu et al [31, 43] They used a same SCB specimen geometry with different testing parameters (i.e. loading rate, temperature), apparatus (displacement measurement devices), and fracture energy calculation methods for both low and intermediate temperature fracture behavior evaluation of AC materials. In this research strain energy as the total energy consumed in specimen to overcome the fracture resistance of asphalt mixtures, is assumed to investigate characteristic specification of various asphalt mixtures under different loading rates
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