Discussion on Paper No. 6267: The Design and Construction of Concrete Roads Overseas.

Abstract

D.S.I.R.) referred to an informal international committee of engineers from several European countries which had been formed as a result of discussion at the Tenth International Congress of the Permanent International Association of Road Congresses held at Istanbul in 1956. Representatives of seven countries had got together with the idea of having a small body of people who could carry out a really detailed study of each other's practices and methods of design to compare and contrast the reasons for those designs.159. The members of the committee did not represent their countries in any way, but were all engineers of very wide experience in both practice and research on the subject of concrete roads. A report had been prepared as a result of the examination of these detailed methods of design and it was hoped to publish it in the near future. Some of the main conclusions had been very similar to those of the Authors.160. For instance, the thicknesses of concrete used for design purposes for given weights of traffic were similar in these seven European countries. For a particular set of conditions of soil and traflic, the design thicknesses ranged from 20 to 24 cm-a relatively small variation compared with some of the other variations in design which had become all too evident in the discussions. These thicknesses were expected to provide adequate service; but, since the members of the committee had not agreed on the expected life of the road, or on the exact nature of the traffic which was going to use the road, or, in fact, on what constituted failure, it had not been possible to arrive at a definite thickness which could be used in all conditions. 161. It had been agreed, however, that what was now wanted was information on the nature and volume of the traffic using the roads, its distribution across the road, and the nature of the permissible wheel loads used; that was where discussion had broken down in trying to reach precise agreement on the question of thickness. Mr Sparkes thought that the question of the thickness of the concrete had been about the only point on which the committee had reached any substantial measure of agreement. In alm?st all other respects there were large differences of opinion.162. There was wide variation in the adopted distances between expansion joints as the Authors had pointed out, from a distance of about 35 ft in Belgium up to almost t Proc. Instn civ. Engrs, vol. 9, p. 23 (Jan. 1958