Applying Statistical Methods for Further Improvement of High-Performance Concrete for New York State Bridge Decks

A new concrete mixture designated “Class HP” for high-performance has been developed for bridge decks in New York State. A modification of the state’s standard Class H concrete, it has better handling and workability characteristics, reduced permeability, and greater resistance to cracking and displays little or no surface scaling. These improvements have potential to result in twice the previously expected concrete service life. The mixture incorporates substitutions for cement of 20 percent Class F fly ash and 6 percent microsilica. It has now been established as the required concrete mixture for all decks built by the New York State Department of Transportation. Its successful implementation has triggered further research toward an even better mixture. An experiment was designed and performed to investigate the effects on cracking and permeability of microsilica and fly ash content, as well as the effects of total weight of cementitious materials. Experimental designs allowed investigation of a broad range of possible combinations while only a limited number of mixtures were tested. Statistical analysis of experimental data is presented and some concrete mixes are recommended for further study, especially those having 10 to 25 percent fly ash, 11 to 12 percent microsilica, and 327 to 375 kg/m³ (550 to 630 lb/yd³) of cementitious materials, and also those with 20 to 35 percent fly ash, 4 to 6 percent microsilica, and 392 to 428 kg/m³ (660 to 720 lb/yd³) of cementitious materials.