Effect of Steel Slag Aggregate on Pavement and Flame-Retardant Performance of Warm-Mixed Flame-Retardant Asphalt Concrete.

With the rapid development of tunnel construction, tunnel safety and the shortage of high-quality aggregates have concerned researchers so that this issue has become a research hot spot in the past few years. In the present study, we intended to prepare warm-mixed flame-retardant asphalt concrete using steel slag aggregate and evaluate its pavement and flame retardant performance. In this regard, the chemical composition and microstructure of the steel slag were studied using X-ray fluorescence analysis (XRF) and scanning electron microscopy (SEM). Then diverse pavement performances, including the dynamic stability, immersion Marshall, freeze–thaw splitting strength and low-temperature bending, were investigated for the warm-mixed flame-retardant asphalt concrete with steel slag aggregate. Moreover, a creative method of the flame spray gun combustion test was proposed to characterize the combustion degree and evaluate the flame-retardant performance of the asphalt concrete with steel slag. The experimental results show that the high-temperature and moisture stability performance are improved due to the addition of steel slag, however, the low-temperature performance is reduced for the warm-mixed flame-retardant asphalt concrete while it is still higher than the requirement value of the Chinese specification (GB/T 30596-2014). Meanwhile, the ignition temperature is increased and the ignition time is delayed for warm-mixed flame-retardant asphalt concrete because of the addition of steel slag. It is concluded that asphalt concrete with steel slag has excellent flame-retardant performance so that it is an appropriate choice for tunnel pavement.