David G Tepke

CONCRETE MATURITY FIELD STUDIES FOR HIGHWAY APPLICATIONS

The Arrhenius maturity function was used to estimate strength evolution in three highway structures: a bridge pier, a bridge deck, and pavement. The research documents field instrumentation and strength estimation. Each structure was constructed with a mixture containing 35% ground granulated blast-furnace slag as a mass replacement of total cementitious materials and approximately a 0.40 water-cementitious materials ratio. The temperature profiles for each application were recorded and discussed. The logarithmic strength-maturity relationship was compared with the hyperbolic strength-maturity relationship for each application. Cylindrical concrete specimens, cast on site during construction, were exposed to a variety of curing conditions. Minor differences in material proportions were also investigated. The quality of cure of the companion specimens significantly affected the strength-maturity relationship. Small deviations in mixture proportions did not appear to affect significantly the strength maturity relationship for the mixtures studied.

Performance Evaluation of Concrete Bridge Deck Affected by Chloride Ingress: Simulation-Based Reliability Assessment and Finite Element Modeling

Modeling is presented for the effect of cracks on chloride ingress into bridge decks with epoxy-coated reinforcing steel. A finite element diffusion model is used in conjunction with a Monte Carlo probabilistic method to address the inherited randomness of input variables. Field data from New York and Pennsylvania bridge decks under service are used to derive the distributions of diffusion coefficients and concrete cover depths under common specifications and construction practices for bridges in the northeastern United States.

CONCRETE MATURITY PROGRESS: SURVEY OF DEPARTMENTS OF TRANSPORTATION

Results are provided from a concrete maturity survey that was distributed to representatives of 50 departments of transportation (DOTs) in the summer of 2000. The purpose was to display the state of national advancements and practices relating to concrete applications for predicting in situ portland cement concrete strength. Information such as DOT project and research details, method of maturity determination, state applications, and general attitudes toward the concept was requested. Representatives from 44 states replied to the 12-question survey. Results revealed that about 73 percent of the states that responded either have conducted or are currently involved in at least minor research with the concept. Furthermore, approximately 30 percent of the represented states have protocol or specifications governing the use of this developing technology. Representatives throughout the United States have reported that maturity is being used to predict critical strengths for such actions as pavement opening to the public; pavement opening to construction traffic; structural acceptance; and formwork removal for bridges, pavements, and other highway structures.