National Concrete Pavement Technology Center

Project description

The main objectives of this project is to further validate the aggregate-solution method and the accelerated concrete cylinder testing (ACCT) and validate the approach (developed in research project 0-6656) of developing alkali silica reaction (ASR) resistant concrete mix. Developing Alkali-silica reaction (ASR) resistance mix is a combined approach of aggregate -solution testing measuring Ea (activation energy) and threshold alkalinity (THA) and concrete testing. The specific objectives are as follows: (1) Validate the usefulness of threshold alkalinity in determining alkali loading for different aggregate sources which could potentially be used to modify mix design option 7. In option 7 of Texas Department of Transportation (TxDOT) Item 421, it is recommended that the total alkali contribution from cement in the concrete should not exceed 3.5 lbs per cubic yard of concrete when using hydraulic cement alone. With the eventual loss of Class F fly ash sources, the department needs to investigate other methods to determine potential reactivity of aggregates in terms of alkali threshold (current test methods are not appropriate for this analysis) in order to be prepared in the event Class F fly ash is no longer readily available. (2) Further validation of ACCT (testing period, expansion limits, level of alkali loadings, appropriate level of soak solution chemistry, suitable specimen dimension etc.) method - Use the TxDOT field exposure block data to calibrate the ACCT method. (3) Suitability of ACCT to test job mix. (4)Validation of the combined approach using both aggregate-solution and concrete testing for formulating ASR resistant mix.