ROUTOFLEX M: AN EASY-TO-USE, HIGH PERFORMANCE BINDER PARTICULARLY SUITED FOR THIN DRESSING OF ASPHALTIC CONCRETE FOR ROAD MAINTENANCE --BITUMEN, FLEXIBLE AND DURABLE. 3RD EUROBITUME SYMPOSIUM 1985, THE HAGUE, NETHERLANDS, SEPTEMBER 11-13, 1985

The use of thin wearing courses must not involve working under over critical conditions. Temperatures close to those normally employed and conventional equipment facilitate the use, and enhance the reliability of special products. The routoflex m binder (alias bp 247) developed for this application jointly by bp and gerland is -thanks to the choice of two suitable polymers -as easy to use as a non-modified bitumen of equivalent penetration value. Thin routoflex surfacings are laid down at a temperature between 140 deg c and 170 deg c, which illustrates their excellent handling characteristics, as more particularly evidenced by the gyratory shear compactor. The plasticity interval (59 deg c on the ring and ball test, -27 deg c on the fraass test) is very wide (86 deg c). Temperature susceptibility is very low (penetration index + 1.67). At low temperatures, flexibility -demonstrated by substantial tensile elongation values -is such that the asphalt concrete at -20 deg c has a modulus of rigidity equivalent to that obtainable with a 180/220. Cohesion at high duty temperatures is such that the asphaltic concrete performs better on the rutting test at 60 deg c than 40/50 bitumen, which is already good in performance terms. The fatigue strength of asphaltic concrete obtained is very much superior to that obtainable with 40/50 (0.00022 for relative deformation at million cycles as against 0.00014 adhesion is reflected in: -an immersion/compression ratio of 0.96 on the duriez test -excellent performance on the stripping test, whatever the nature of the aggregate used. As for ageing, oxidation and temperature resistance are very satisfactory as determined by tests of residual cold tensile strength and loss on heating. By virtue of their excellent overall performance they can be employed to obtain very effective thin surfacings for deformable substrates subject to high deflection, heavy traffic loadings and the effects of weather. Thin routoflex surfacings are particularly suitable for road construction and maintenance in mountainous areas. They can be used in very thin surfacings in the shape of microbetons and high quality chipping-based dressings, mainly for busy roads in built-up areas. Their properties of cohesion, water resistance, ageing and fatigue strength already referred to are such that they can constitute excellent pervious surfaces. The characteristics described are generally obtained without increasing the content of binder. Additionally, they are particularly economic in use since thin dressings can be applied to distorted and worn substrates, thus making it possible to postpone more substantial maintenance work, avoid the need for removal and other work required to restore road levels or edges, and also minimise the quantities of materials required per square metre. For the covering abstract of the symposium see IRRD 815173.