The AASHTO LRFD (Load and Resistance Factor Design), as well as other design manuals, has specifications that estimate the structural performance of a concrete mixture with regard to compressive strength, tensile strength, and deformation-related properties such as the modulus of elasticity, drying shrinkage, and creep. The Washington State Department of Transportation (WSDOT) is evaluating the performance properties of approved concrete mixtures, and verifying the measured properties and comparing them to those expected from AASHTO specifications. Factors influencing the structural behavior of concrete mixtures include the coarse aggregate source and size, paste content, water-to-cementitious ratio, and age characteristics.
These factors are not integrated within AASHTO LRFD models to predict the concrete mixture’s performance. Current specifications relate most of the structural performance properties to the compressive strength, with little regard to the mixture proportions. This research was directed toward assessing the performance of the approved WSDOT concrete mixture and the sensitivity of the properties based on aggregate source and paste content.
The objectives of this research were to investigate whether modifications to AASHTO LRFD specifications were required, and if so, to recommend improvements using pertinent mixture proportions.