Efficacy of a Ternary Blend Mixture in Improving Bridge Deck Concrete Durability in Tennessee: Fid-Bau Portal

Efficacy of a Ternary Blend Mixture in Improving Bridge Deck Concrete Durability in Tennessee

Nidiffer, Robert / Burdette, Edwin / Brown, Casey / Ankabrandt, Ryan

Studies related to the durability of bridge deck concrete in the state of Tennessee have been ongoing at the University of Tennessee for the past decade. The most recent phase of this research began in the fall of 2009 with a focus on developing a criteria and methodology to assess the durability of bridge deck concrete in Tennessee. The concrete’s resistance to chloride ion penetration was used to evaluate durability. This resistance was measured by two test methods: the surface resistivity (SR) test and the rapid chloride ion penetration (RCP) test. Current guidelines set forth by the Tennessee Department of Transportation (TDOT) require that a Class D concrete mixture be placed on all bridge deck applications. The SR and RCP tests have been performed on Class D concrete cylinders from various bridge deck placements across the state for the past 2.5 years. The Class D mixture consists of 75% cement and 25% fly ash (generally Class F). Results indicate that the current concrete mixture fails to adequately resist chloride ion penetration at satisfactory levels. Ternary blend concrete mixtures, so defined when the mixture contains three different types of cementitious materials, have been found to offer benefits to both the strength and durability of concrete. Thus, it was decided to propose a ternary blend concrete mixture. While ternary blends are not currently prohibited by TDOT, the Class D concrete mixtures currently being placed on bridge decks are, as noted, binary mixtures. Ternary blend laboratory samples were created to compare SR and RCP values to the typical Class D mixtures. Results from the tests, as well as results reported in technical literature, indicate that ternary blend mixtures have significantly better resistance to chloride ion penetration than the typical Class D mixtures, indicating improvement in concrete durability with such a mixture.