An Applied Research Programme on Continuous Reinforced Concrete Pavements

Continuous reinforced concrete (CRC) pavements built in France since this technique was first used in 1983 have pratically all been designed in the same way as pavements consisting of dowelled slabs. Owing to the circular form of the test tracks at fatigue facility of the Laboratoire Central des Ponts et Chaussées in Nantes, CRC has not been involved in the extensive experiments into concrete pavements calTied out since at this facility, and the design methods have remained unchanged. The fact that full-scale fatigue tests on CRC structures necessitate the availability of a straight-line traffic simulator resulted in the national "FABAC" (FAtigue du Béton Armé Continu) [fatigue of CRC] research project, which has the following principal objectives to clarify the behaviour and damage modes of CRC structures. There is particular interest in precisely characterising the behaviour of the interface between the CRC and its foundation, since certain professionals believe that the assumption of complete slip adopted in the cunent design method is unduly penalising; - to clarify the role and true value of transverse reinforcement in the CRC, which is now highly controversial owing to the complications of laying and the resulting cost; - to test a new type of longitudinal reinforcement consisting of high elastic limit steel strips, developed in France, known as FLEXARM +. This project was initiated in mid-1995 and today has a provisional budget of nearly five million francs. The test sections have now been built together with two linear fatigue machines which can simulate traffic equivalent to one twin-wheel passage of 6,5 tonnes a second, making at least 2 million passages a month. Eight tests have so far been carried out, one of them being extended up to 10 million passages, equivalent to nearly 8 million trucks. The measurements and observations made during these tests appear to suggest excellent performance by composite structures such as a lean concrete foundation, a bituminous interface, an upper course in CRC or alternatively a bituminous foundation and an upper course in CRC.