Large portions of Maryland’s 16,000 lane-miles of major roadways are composite pavements, consisting of an asphalt surfacing on top of a Portland Cement concrete (PCC) pavement. The composite pavements of this type are generally located on roadways that carry heavy traffic, in terms of volume and/or weight, such as primary highways. When distresses occur along these pavements that require some form of repair and rehabilitation, it is necessary that these repairs be performed quickly to minimize disruptions to traffic.

The full-depth concrete patch repair has been used for rehabilitation of composite pavements to address distresses such as reflective cracking at the locations of joints and cracks in the underlying concrete pavement. The full-depth repair involves complete removal of the entire depth of concrete and the asphalt at the affected area, typical patch areas being 6 ft long and 12 ft wide, and replacement with a new concrete and asphalt patch. This technique has been used successfully for many years. However, depending on materials and procedures used, it may take one or more days before the repaired pavements can be opened to traffic, which is unacceptable for heavily trafficked roadways in urban areas.

Maryland State Highway Administration (SHA) currently requires use of a 12-hour concrete mix for patching in heavily trafficked roadways in urban areas. This mix is required to achieve 2,500 psi compressive strength in 12 hours. However, it is desired by the SHA to reduce the concrete set time to allow the patch to be opened to traffic after about 4 hours after placing the concrete in the patch. The objective of the project is to test proper concrete material mix design both in the lab and in the field for composite pavements that will allow the repaired sections to be opened to traffic after four hours of concrete placement in the patch area. A shorter patch repair time would minimize the disruption caused to traffic and ultimately provide longer lasting composite pavements.

Following describes briefly the proposed laboratory test program to determine the best two mix designs to be used for field trials. Two mix designs will then be selected based on compressive strength, freeing-thawing durability, and initial and peak concrete temperatures. For the selected two mixes, additional specimens will be fabricated to establish the strength-maturity relationship and the strength-pulse velocity relationship.

Two four-hour mix designs will be developed under this stage of testing. Selection criteria will be concrete compressive strength and freezing-thawing durability. The specified concrete compressive strength is 2,000 psi at four hours. Concrete temperature development also will be monitored for all mixes.

Phase 1. Determination of Final Mix Designs

1a. Compressive Strength Test

1b. Freezing-Thawing Durability Test

Phase 2. Non-Destructive Strength Evaluation

2a. Pulse Velocity Test

2b. Maturity Test