Ultra-High Performance Concrete Overlays for Concrete Bridge Decks

With much of the world's infrastructure needing rehabilitation, new and more effective methods of repair are required to ensure that concrete structures can continue to perform adequately. This work investigates the potential for using locally produced ultra-high performance concrete (UHPC) as an overlay material to rehabilitate existing normal strength concrete (NSC) bridge decks. Bond strength tests were conducted using NSC substrate with four different textures seven days after casting the UHPC overlay. Depths of the different textures determined in accordance with ASTM E965 were 0.05, 0.90, 1.6, and 2.8 mm. Results from slant shear, split cylinder, and split prism tests indicate good bond even when inadequate texturing was provided. Average shear strengths from slant shear (ASTM C882) specimens increased from 7.1 MPa for the 0.05 mm texture to 19.8 MPa for the 2.8 mm texture. Similarly, bond strengths from split cylinders (ASTM C496) increased from 1.8 MPa for the 0.05 mm texture to 2.4 MPa for the 2.8 mm texture. Bond strength testing of split prisms specimens was conducted using a modified version of ASTM C496 and produced results of 1.5 MPa for the 0.05 mm texture and 3.7 MPa for the rough texture. Direct tensile strength testing was performed in accordance with ASTM C1583 and produced a bond strength of 1.08 MPa for chipped texture with a depth of 1.00 mm. Testing of chloride permeability (ASTM C1202) of the UHPC indicated negligible charge passing through the specimens. Free shrinkage measurements initiated 90 minutes after placement resulted in a total shrinkage of 1800 micro-strain in the UHPC after seven days. Results from these tests indicate the potential of locally produced UHPC to serve as an alternative to traditional overlay materials.