Thirty-six unreinforced concrete roads constructed between 1970 and 1979 were surveyed by the Advisory Panel on Concrete Road Construction to provide information on the structural performance, the performance of joints and the surface characteristics. Typical lengths of carriageway, each comprising 100 bays, were chosen from each scheme and examined in detail. Statistical examination of the performance data has produced a number of important conclusions. Relationships exist between the extent of transverse cracking and the ratios of bay length to slab thickness and bay length to bay width. These would suggest that for slab thicknesses greater than 225 mm bay lengths should not exceed 5 m and for lesser slab thicknesses 4 m when using aggregates other than limestone; bay widths should not exceed 4.2 m. When limestone aggregates are used throughout the depth of the slab these lengths may be increased by 20 per cent. Fixed-form paved slabs are better than those produced by slip form paving in respect of less shallow-spalling at transverse joints and more adequate surface textures; two-course working produces better riding quality than single-course construction. Transverse joints with neoprene seals had greater vulnerability to shallow spalling and had more deficient contraction joints than those sealed with hot-poured compounds. However, in half the schemes where neoprene seals were used they were placed by a wet-plough method which also contributed to shallow spalling and deficiencies at the joints. Riding quality and adequacy of surface texture are related; roads of poorer riding quality have greater deficiencies in surface texture. Significant differences were observed for cracking, deficient contraction joints and surface texture when the effects of contractors were studied; the standard of workmanship plays an important part in the performance of concrete roads. A number of factors, including aggregate type, sub-base type, method of placing dowel bars and presence of bottom crack inducers, have no significant effect on the performance indicators. Deep spalling at transverse joints and shallow spalling at the intersections of transverse and longitudinal joints are not significantly related to any of the variables studied. (A)

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