EVALUATION OF STEEL BRIDGE DECK MA MIXTURE PROPERTIES DURING CONSTRUCTION

Responses of steel bridge deck pavement to environmental and traffic loadings are much different from those of normal highway asphalt concrete pavement or concrete bridge deck. Steel bridge deck pavement generally deals with more challenging conditions, especially orthotropic steel bridges (Seim and Ingham, 2004; Medani et al., 2007; Battista et al., 2008; Cong et al., 2009; Kashefi et al., 2010). Therefore, materials used in constructing the steel deck bridges must possess excellent properties. Guss Asphalt (GA) and Mastic Asphalt (MA) are two types of asphalt concrete primarily used in steel deck bridge pavement construction (Eulitz et al., 2004; Ripke, 2009; McFadyen and Blumensen, 2010; Bocci and Canestrari, 2012). These two materials are composed of specifically graded aggregate and high content of asphalt binder to form a coherent, voidless and impermeable solid or semi-solid mass at ambient temperatures, but sufficient fluid at construction temperatures. The asphalt concrete mixtures are placed using hand float or other suitable equipments. No compaction is required. Therefore, these types of asphalt concrete mixtures are termed as poured asphalt mixture. Two different types of poured asphalt mixtures are known: GA and MA. GA was developed in Germany and MA was originated in England. To obtain adequate workability, GA and MA have been mixed and constructed at temperatures between 200 degrees C and 240 degrees C. In this study, GA and MA mixture samples were prepared using both laboratory mixers and batch plant and truck mixers. Samples were subjected to laboratory testing to evaluate the workability, rutting resistance and fatigue cracking resistance of the poured type asphalt mixture. Test results indicated that mixing time had significant influence on workability, rutting resistance and fatigue cracking resistance of the poured type asphalt mixtures. Longer mixing time and higher mixing temperature resulted in better rutting resistance but lower fatigue cracking resistance(Pauli and Huang, 2013). Therefore, during construction, mixing time and higher mixing temperature need to be controlled to achieve adequate performance for both rutting and fatigue cracking. It is recommended that, during construction, the Dynamic Stability at 60 degrees C and Impact Toughness at 15 degrees C be used as the quality control indexes.