Compatible Approach to Concrete Strength Characterization in the Design and Construction of Concrete Pavements

The effectiveness of a concrete pavement construction specification depends on the degree of correlation the criteria in the specification have to the material properties and behavior characteristics that govern the performance of pavements. Since concrete strength is determined on the basis of small test specimens, it is important that the strength measured in these specimens be representative of the strength within the actual configuration of a pavement system. A primary deficiency in this regard is that strengths obtained from different test specimens can be quite different from each other and from the strength of the concrete in the pavement. This fact raises the question of which specimen should serve as a representative concrete strength standard that would allow a reliable measure of concrete quality and yet provide a parameter that is compatible with design stress calculations. This deficiency is encompassed within size and geometry effects that are present when estimating strength from small test specimens. Since most distresses in concrete pavements are due to tension-induced cracking, it is only logical that tension-type tests be used to represent concrete resistance to failure. A simplified tension test method, based on the fracture mechanics theory, provides a solution to the deficiency by taking into account size and geometry effects. The method considers the geometry of the specimen from which the strength is being measured (e.g., cylinder) and the geometry of the structure to which the measured strength is being applied (e.g., pavement slab). This method makes it possible to circumvent the problem of obtaining a representative strength value from a small laboratory specimen.