The post-war pattern of refining in Europe led to the introduction of fiddle East bitumens of relatively unknown quality. This met with some resistance from road engineers accustomed to the traditionally accepted Western Hemisphere supplies. For this reason a series of experimental road surfaces has been laid in England and Sweden to compare the performances of Mexican, Venezuelan and Middle East penetration grade bitumens, and to study the effect of physical and chemical properties on their durability in road surfaces. This report is only concerned with the results of an experiment at Wallingford in Southern England. The road surface has been examined annually by an independent evaluation panel, whose assessment indicated that after four years service the quality of all the 58 experimental sections was satisfactory, and that the Middle East materials had so far given service equivalent to that of the accepted Western Hemisphere products. The resistance to stripping of the experimental bitumens in the road surface has depended largely on the type of stone used, and the deficiencies of one type of stone examined, quartzite, were substantially overcome by the addition, during mixing, of minor proportions of hydrated lime to the aggregate. The Middle East bitumens tested appear to have hardened less rapidly than those from the Western Hemisphere; thus, although the latter had better initial temperature-susceptibility, the advantage of remaining soft at low temperatures was soon lost, due to the faster and greater hardening of the Western Hemisphere bitumens. The predicted ultimate hardness of the bitumens correlates with the asphaltenc content of the original material. The relative hardening tendencies of bitumens can be predicted by the Accelerated Weathering and Thin Film Oven tests. The main conclusion at this stage of the experiment is that Middle East road bitumens can be formulated which should give overall performance as satisfactory as that of the Western Hemisphere products under mild climatic conditions in an open textured carpet.
Les normes du raffinage d'après-guerre en Europe ont conduit à l'introduction de bitumes du Moyen-Orient d'une qualité assez mal connue. Ceci devait se heurter à une certaine opposition des ingénieurs des Ponts-et-Chaussées accoutumés à la fourniture traditionnelle de l'Amérique. Pour cette raison, des revêtements expérimentaux furent construits en Angleterre et en Suède afin de comparer les performances des bitumen orginaires du Mexique, du Venezuela et du Moyen-Orient, et d'étudier les effets de leurs propriétés physiques et chimiques sur Ia résistance des routes. Le présent rapport ne concerne uniquement que les résultats obtenus au cours des expériences faites à Wallingford, dans