Induction heating performance of asphalt pavements incorporating electrically conductive and magnetically absorbing layers

In recent years, electro-magnetic induction technology has been widely applied in functional asphalt pavements as an in-situ heating method. Most of the existing research focused on incorporating inductive agents in asphalt pavements to improve their induction heating performance (IHP). In addition to electrically conductive asphaltic layers, a new structure of asphalt pavement incorporating magnetically absorbing asphaltic layers is proposed in this research to enhance the IHP. This multi-layer asphalt pavement system is mainly composed of three sub-systems from top to bottom: the upper one made of electrically conductive layers containing waste steel shavings, the middle one is the asphalt mixture layer with the pre-embedded induction coil and the lower one made of magnetically absorbing layers containing waste ferrites to replace the conventional waterproof adhesive layer. The upper part was developed with four different content of waste steel shavings, used as inductive agents in asphalt. Meanwhile, three kinds of magnetically absorbing layers were prepared, including common magnetically absorbing layers and two kinds of asphalt magnetically absorbing layers. Then, the pavement performance test was performed to examine the asphalt magnetically absorbing layers, and the induction heating experiments of the newly formed multi-layer systems were conducted. Heating and energy saving rates were used to evaluate the effect of the content of inductive agents and the magnetically absorbing layers on IHP. Results show that the asphalt magnetically absorbing layers can meet the requirements of the conventional waterproof adhesive layer. It was also found that the optimal IHP was obtained when the content of waste steel shavings was 6%. More interestingly, the common magnetically absorbing layers improve the IHP better than the asphalt magnetically absorbing layers. This means that the addition of asphalt has a negative impact on the magnetic absorption effect.