Mechanical Properties and Durability of Bonded-Concrete Overlays and Ultrathin Whitetopping Concrete

Concrete overlays have been used for pavement and bridge-deck rehabilitation for many years. The mechanical properties and durability of several plain and fiber-reinforced concrete-overlay mixes were analyzed. Eight different concrete-overlay mix designs were investigated. The materials properties investigated were compressive and splitting tensile strength, modulus of elasticity, bond to concrete (with three different surface roughness characteristics), and durability. Freeze-thaw tests were performed to determine the durability of the concrete mixtures used. Strength and stiffness were investigated from 1, 3, 7, and 14 days. Laboratory tests on the strength and stiffness development of eight candidate concrete-overlay designs showed that high-strength concrete was appropriate for opening overlays to traffic in 24 h or less, but normal-strength concrete may be used if traffic loading may be delayed for 48 or 72 h. For larger projects, where paving continues over several days, normal-strength mixtures may be used when 48 to 72 h or more of curing can be achieved before traffic loading begins, with high-strength mixtures used for the last day's construction. All the high-strength concrete overlay-mixture designs tested appear to have satisfactory strength, stiffness, bond properties, and durability for use in bonded overlay construction. The normal-strength concrete is more economical than the high-strength concrete but develops its design properties more slowly.