Concrete Bridge Deck Overlays in Illinois: Mix Design Experimentation and211 Investigation of Construction Methods

摘要

The purpose of a bridge deck overlay is to extend the life of a structure by211u001eproviding a durable wearing surface and a barrier against chloride intrusion. The 211u001emajority of the deck overlays in Illinois' recent past have contained 211u001emicrosilica. Problems associated with microsilica deck overlays, such as rapid 211u001eslump loss, poor constructability, and shrinkage cracking, prompted the 211u001edevelopment of three alternative mix designs and a subsequent field evaluation. 211u001eIn Design 1, th microsilica content was dropped from 50 to 33 lbs/cu yd. Design 211u001e2, a ternary mix design, contains cement, microsilica, and Class C fly ash. 211u001eDesign 3, which contains fly ash and no microsilica, has a 25% cement replacment 211u001erate at a 1.5:1 replacement ratio. All three designs share changes in coarse 211u001eaggregate gradation, proportion of coarse and fine aggregate, and water-cement 211u001eratio. Twenty-one bridge deck overlays were included in the field evaluation of 211u001ethe three mix designs. All of the overlays used the new designs and were 211u001econstructed in 1998. Construction observations are reported as well as various 211u001etest results, including flexural strength, rapid chloride permeability (Illinois 211u001eModified AASHTO T 277), salt ponding and chloride ion content, and tensile 211u001estrength of bond (pull-off). Also, initial distress surveys of all 21 structures 211u001ewere performed between three and six months after the overlays were placed.