Continuous reinforcement in concrete pavement

Abstract

Summary: Concrete pavements, unless constructed with closely spaced transverse joints, generally crack transversely at frequent intervals. These cracks tend to open appreciably with time unless the pavement is reinforced. For some years there has been a continued interest on the part of highway engineers regarding the practicability of concrete pavements constructed without transverse joints and reinforced longitudinally with continuous bonded steel in sufficient amount to hold all cracks closed. In the autumn of 1938 a considerable number of continuously reinforced sections, ranging from 20 to 1,310 ft in length, were constructed near Stilesville, Indiana, on US 40 as a co-operative research project to study the effects of varying amounts of longitudinal steel in sections of various lengths. The behaviour of the sections during the first ten years of service life shows conclusively that continuous reinforcement can be depended upon to prevent the opening of transverse cracks in concrete pavements. In the long, heavily reinforced sections many fine cracks have developed in the central region. These cracks have not opened and have ravelled only slightly with traffic and exposure, a condition that has required no maintenance and may be considered superficial. The sections have remained strong, durable structural units. The presence of even the heaviest longitudinal bar reinforcement has apparently not affected adversely the condition of the concrete in the pavement. The concrete appears to be sound throughout, there has been no spalling, and there is a complete absence of longitudinal cracking above the bars. Infact, the manner in which the steel has held closed all cracks, especially those in the more heavily reinforced sections, is believed to have been conducive to distributed interfacial pressure at the cracks which should tend to minimize damage to the concrete from concentrations of presswe such as sometimes develop at cracks in plain concrete pavements. Pumping has developed at many of the transverse joints, but, wth two exceptions, has not been observed at any of the vast number of transverse cracks. This indicates that a concrete pavement without transverse joints and containing adequate longitudinal reinforcement is not nearly so susceptible to pumping as pavements of other designs. In spite of the many transverse cracks that have developed in the long sections, the riding quality of the pavement has remained excellent and the pavement itself has been protected from damaging impact forces such as tend to develop where the surface alinement is not maintained.