Durability of Certain Configurations for Providing Skid Resistance on Concrete Pavements

About the report:

The main objective of this study was to establish the factors that influence the durability of the surface configurations that are used or can be used to provide high and long-lasting skid resistance for portland cement concrete pavements. In the development of such durable surface texture an insight into the pavement wear mechanism in the presence of grooves is necessary. The wear of pavements may involve polishing and small-scale degradation at the top surface as well as a possible large-scale material loss. The study of wear phenomena for rough textured concrete pavements involved the investigation of: (1) The surface behavior of the pavement, and (2) the structural behavior of the area below the top surface and around the grooves. The wear phenomena occurring at the top surface was investigated experimentally by petrographic examination of thin sections prepared from the cores taken from actual highways that had experienced various degrees of wear. The samples included saw cut grooves imparted to the worn concrete surface, and also textures imparted to the fresh concrete pavements by burlap drag and metal tines. The microscopic study of the thin sections showed that most of the cracks were found at the top surface and virtually no cracks were seen at the bottom of the grooves. Variation in the strength of the pastes affected the wear. The loss of material at the surface in strong pastes resulted from flaking, and in weaker pastes it was because of crushing. Both pastes yielded good microtexture, but the weaker mixtures wore faster. The chipping of aggregates at planes and zones of weakness also provided good microtexture. Concrete slabs having different surface textures were prefabricated and tested on a circular test track. After 1,670,000 wheel passes, no appreciable wear was observed. This indicated that the surface pressures exerted by the tires used in the test track are low, and it takes a large number of wheel passes to wear the pavement surface. The samples studied microscopically had a maximum groove depth of 1/8" (3.2 mm), and it was noted that a large-scale material failure did not occur in the concrete and wear was mainly a surface phenomenon. However, deeper grooves might cause a structural failure as well as the ordinary surface wear. The structural behavior of the area below the top surface and around the grooves was investigated theoretically. Involved was the determination of internal stresses within the concrete under an assumed surface loading. If the internal stresses were higher than the ultimate capacity of the material, cracks and eventual loss of material would occur at critical regions. This would indicate a large-scale failure. Initially three types of grooves (square, triangular and round), having a 1/8" (3.2 mm) texture depth and 3/4" (19.0mm) spacing were considered. It was found that the critical locations where stresses could develop to cause failure were at the bottom or at the corner of the grooves. Later the effect of groove geometry on the internal stresses was investigated theoretically by considering the effect of increasing the depth of square grooves from 1/8" (3.2 mm) to 1" (25.4 mm) in 1/8" (3.2mm) increments while keeping the groove width and spacing constant. In this way deeper rectangular grooves were formed that provided better drainage. It is concluded that the deeper grooves are more prone to. structural failure since increasing the depth of the groove yields higher principal tensile stresses. The freezing and thawing durability of the square, triangular, and round groove configuration was satisfactory, and after 50 cycles no differences could be distinguished in the durability of the tested groove configurations.

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