Noise-reducing double-layer porous pavement with steel slag as aggregate in the top layer

This paper presents results of a trial replacing the natural aggregate in the top layer of a double-layer porous asphalt pavement with steel slag. A 200 m long motorway section was paved with this material and performance in terms of macrotexture and noise properties (made annually with the CPX method) were monitored for an entire life-cycle of 7 years. The results in terms of noise reduction compared to the common Swedish reference pavement (SMA16) indicated an initial noise reduction of about 7 dB; only marginally lower than the same pavement with normal natural aggregate. By time, this marginal loss in noise reduction was turned into a somewhat higher noise reduction after 5-6 years of service. This was surprising since the steel slag pavement appeared to clog a little more than the conventional double-layer asphalt pavement. Probably, there are (uncertain) properties in the slag material which balances out the clogging effect. At the present time this pavement has reached an age of 7 years, which is similar as the conventional porous pavement has served on the same road over two lifecycles so far. With its lower noise-reducing deterioration versus time, steel slag is a promising material for recycling in this way.