Paul J Tikalsky

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.

SBRA Model for Corrosion Initiation of Concrete Structures

This paper presents a finite element based probabilistic corrosion initiation model using Simulation Based Reliability Assessment (SBRA). The model is focused on the effect of diffusions and ingress of chloride ions in bridge decks with excessive cracks to investigate the performance of different corrosion resistant steel reinforcements. The objective of this research is based on the formulation of probabilistic corrosion initiation model with the inclusion of distribution of High Performance Concrete (HPC) diffusion coefficients computed from fundamental electrochemistry and the variation of surface chloride concentration from the field data of Virginia bridge decks as well as other random variable parameters. This study shows the variability and sensitivity on estimation of the time to onset of corrosion using Monte Carlo technique. In addition, the estimation of corrosion free service life for the preliminary design of concrete structures in harsh chloride environments will be indicated.

Drying shrinkage behavior of mortars made with ternary blends

Ternary cementitious blends are widely used in todays concrete mixtures, particularly when high performance is needed. This paper discusses drying shrinkage behavior of mortar mixtures made with various ternary blends. Ternary blends consisting of different combinations of portland or blended cement, slag, fly ash, and silica fume were considered. The amounts of slag, fly ash, and silica fume ranged from 15% to 35%, 13% to 30%, and 3% to 10% by mass of cementitious materials, respectively. Mortar bars were made with the ternary blends and subjected to drying (i.e., temperature = 73° ± 3°F and relative humidity = 50% ± 4%) after standard moist curing for 28 days. Free shrinkage of the bars was assessed at 56 days of age after 28 days of drying. A response surface analysis was done to examine the effects of blend proportions on shrinkage behavior of the mortars. To validate this model, an independent group of mortar mixtures with different ternary combinations was cast, and the measured values were compared with the predicted shrinkage values. The results indicated that of the three supplementary cementitious materials in the ternary blends studied, slag showed a dominant effect on increasing mortar shrinkage. The contribution of Class C fly ash to the shrinkage was slightly less than that of slag. An increase in silica fume or in Class F fly ash content slightly increased free shrinkage. There is a good correlation between the measured shrinkage strain and the strain predicted from the shrinkage model developed from the response surface analysis.

Properties of Different Pumice Grades Blended with Cement

AbstractThe research focused on determining the effect of fresh and hardened properties of paste, mortar, and concrete using high Si-Al-Na–containing pumice as a supplementary cementitious material...