Thin continuously reinforced concrete and steel fibre reinforced concrete overlays – Performance assessment after two and three years in service

Seven experimental sections of thin overlay construction on old concrete and asphalt road pavements have been built in Belgium since 1982. These comprise a total area of 107 000 m2 of fibre reinforced concrete (five sections) of la cm and 12 cm thickness and 34000 m2 of continuously reinforced concrete (two sections) of 12 cm, 14 cm and 16 cm thickness. Three experimental road sections wich steel fibre reinforced concrete overlays (70 000 m2) have already been described in a paper presented at the Cembureau Symposium on overlays which was held at Brussels in 1984. The present paper complements that one with further information on the behaviour of thin overlays. The adhesion to the underlying course (bituminous or concrete pavements) and its effect on cracking at the corners and joints has been investigated on the basis of adhesion tests performed on cores drilled from the pavement. The quality of the concrete (the as-placed mix has a relatively high water content) is brought into relation with the results of tests simulating more particularly the behaviour with respect Co deicing salts, etc. In 1984 and 1985 two more experimental sections (36 000 m2) were built wich a distinctly lower number of fibres per unit quantity of concrete (40 kg of thicker fibres per m3). This made for easier placing and better quality of the concrete. In those same years two experimental sections of thin continuously reinforced concrete overlay were applied to a bituminous pavement which had in part been mechanically roughened. The overlay consists of concrete (0 - 20 mm aggregate size) containing 0.6% and 0.77- of longitudinal rèinforcement consisting of 12 mm and 16 mm diameter bars. The paper summarizes the observations relating to the installing of the overlays and gives an analysis of the cracking that occurred. These matters are considered in the context of the construction job parameters.