PAVEMENT OVERLAYS IN VIRGINIA

This paper describes the installation and performance of three hydraulic cement concrete overlays in Virginia. Two of the overlays were placed on continuously reinforced concrete pavement, and the other was placed on rutted asphalt pavement. The overlays were placed to increase the flexural strength of the pavement and demonstrate the feasibility of concrete overlays for extending the service life of pavements. One of the overlays was also placed to prevent spalling caused by a shy cover over the reinforcement. The concretes used in the overlays were strong and highly resistant to the intrusion of solutions, characteristic of high performance concretes. Hooked-end steel, polyolefin, and monofilament and fibrillated polypropylene fibers were added to the concrete used in 31-m test sections to improve its toughness and ability to control cracks. The overlay thicknesses are as follows: 51 mm for project A, 102 mm for project B, and sections of 51 mm, 76mm, and 102 mm for project C. Each of the test section was 610 m long. Concretes were tested in the unhardened state for slump and air content and in the hardened state for compressive strength, permeability to chloride ions, freeze-thaw durability, length change, and shear bond strength. The fiber-reinforced concrete was tested in flexure in accordance with ASTM C1018. The overlays were tested for tensile bond strength, skid resistance, and stiffness measured by a falling weight deflectometer. Tests revealed that all of the overlay concretes were strong and had low to very low permeabilities. Freeze-thaw resistance and shear and tensile bond strengths were all acceptable. Pavement stiffness and skid resistance were improved with the addition of the overlays. The addition of fibers to the overlay concretes improved their toughness and appears to be restricting crack widening at 1 year after placement.