Re-texturing of worn concrete roads to maintain adequate resistance to skidding at high speeds is currently achieved by cutting grooves into the hardened concrete surface. Surface dressings are known to afford a cheap and rapid method of renewing texture on bituminous roads and this report reviews five full-scale road experiments designed to test the effectiveness of the technique on heavily-trafficked concrete roads as an alternative to grooving. The research has demonstrated the feasibility of applying single surface dressings to ungrooved concrete roads carrying over 2000 commercial vehicles a day in one lane (cvd/lane). Surfaces which have been previously grooved require double dressings at this traffic level, but single dressings have proved satisfactory for such roads below 2000 cvd/lane. Target rates of spread of binder recommended for use with 10 mm nominal sized chippings are: (a) rubberised cut-back bitumen 1.1 l/sq m (b) rubberised road tar 1.4 l/sq m (c) tar/bitumen binder 1.3 l/sq m. It is shown that, by using aggregate of high polished-stone value, considerable increases in resistance to skidding, averaging 0.20 and 0.27 units at 50 and 80 km/h respectively, have resulted from the application of surface dressings to worn concrete roads. At higher speeds, the effectiveness of the dressings is dependent upon depth of texture maintained and accordingly recommendations are made for the minimum abrasion values of the aggregates used, to limit wear under traffic. (Author/publisher)
Samenvatting