Effect of ageing on asphalt binders in the State of Qatar: a case study

Ageing of asphalt binders has a significant impact on the rheological properties of asphalt binders and thus affects the performance of asphalt pavements. The rate of binder ageing is accelerated at high temperatures. This study presented a case study on the effect of ageing of the asphalt binder properties in the State of Qatar where asphalt mixtures experience harsh environmental conditions of elevated temperatures. The researchers collected field cores from 5-year-old trial pavement sections in Qatar, recovered the binder and tested to evaluate the change in the rheological properties of the binders. Test results indicated that there is a significant effect of ageing on the rheological properties of asphalt binder in Qatar. This effect was more prominent in the wearing course of pavements and diminishes with the increase in pavement depth. Binders along the wheel path experienced less ageing compared to shoulder. Aggregate type and mix design methods were also found to be affecting the extent of ageing of asphalt binder in the field. Furthermore, the researchers found that the current practice of ageing asphalt binders in pressure ageing vessel (PAV) to simulate ageing in the field is not sufficient for the Qatar case. It is recommended to extend the PAV ageing period from the standard 20 h for a hot climate like Qatar and it might go up to about 70 h based on the results of this study.