Structural Design Parameters of Current WSDOT Mixtures

Abstract

The AASHTO LRFD, and other design manuals, has specifications which estimate the structural performance of a concrete mixture with regards to the 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 and comparing the measured properties 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 objective of this research was to investigate if modifications to AASHTO LRFD specifications were required, and if so, recommend improvements using pertinent mixture proportions.