Concrete containing slag generally exhibits excellent long-term strength and durability. However, several authors have expressed concern about the scaling resistance of concrete containing slag, especially when the dosage of slag exceeds 50% of the total cementitious material in the mixture (1-6). Much of the concern appears to be based on the results of laboratory scaling tests (most commonly ASTM C672) (7), which tend to be in poor agreement with field observations (2-6, 8-10). Others indicate that the test performs adequately for evaluating the relative scaling resistance of concrete specimens (11). A systematic study is needed to determine why this anomalous relationship exists between the scaling of field and laboratory concrete specimens containing slag. Ground granulated blast-furnace slag (GGBFS), referred to simply as ¿slag¿ in this document, has a long history of use with portland cement in concrete. Generally, slag improves many properties of both plastic and hardened concrete. The Transportation Research Board (TRB) Committee on Chemical Additions and Admixtures for Concrete summarizes the impact of slag on the properties of portland cement concrete (PCC) as listed in the table below (1). It is apparent that slag can make a significant contribution to the production of durable concrete products.

· Document the field performance of existing concrete pavements, bridge decks, and other structures made with slag cement that have been exposed to cyclical freeze-thaw cycles in the presence of deicing chemicals. · Determine from the field study and construction/design records which mixtures and construction parameters have produced scale-resistant concrete containing slag. · Determine the effectiveness of ASTM C672 in predicting the deicer scaling behavior of field concrete. If discrepancies are noted, an attempt will be made to explain why the lab tests do not adequately mimic field performance and alternative procedures will be recommended to improve the correlation between lab tests and field performance.

The project is proposed to be accomplished in two phases: Phase 1: - Document the field performance of existing concrete pavements, bridge decks, and other structures made with slag cement that have been exposed to cyclical freeze-thaw cycles in the presence of deicing chemicals. - Determine from the field study and construction/design records which mixtures and construction parameters have produced scale-resistant concrete containing slag. Phase 2: - Determine the effectiveness of ASTM C672 in predicting the deicer scaling behavior of field concrete. If discrepancies are noted, an attempt will be made to explain why the lab tests do not adequately mimic field performance and alternative procedures will be recommended to improve the correlation between lab tests and field performance. Note: Phase 1 of the project will be initiated once sufficient sponsorship is identified to enable expeditious execution of the research plan. Phase 2 sponsorship solicitation will continue concurrently with Phase 1 activity.

Phase I State DOTs* (3 @ $25,000) $75,000 Slag Cement Association* $100,000 Federal Highway Administration $100,000 Phase II: 7 states @ $25,000 = $175,000 Total Budget $450,000