Category:506 Concrete Overlays for Pavement

506.1 Design of Unbonded Concrete Overlays

In specifications for unbonded concrete overlays, there are provisions that require the contractor to establish the existing roadway profile and set the final overlay profile. For this reason the bid item for contractor staking should be included in the contract. For alternate bid projects, this pay item should be included in Section 1 to apply to both the asphalt and concrete overlay alternates.

During construction, the contractor establishes the existing roadway profile and sets the final overlay profile. The resident engineer may adjust the final profile as needed. The profiles are determined in order to account for existing undulations in the pavement and to re-establish a smooth profile, not to re-establish the vertical alignment grade control points. The cubic yards of concrete required will be determined by the resident engineer from the set or adjusted profile. This quantity will be the field established plan quantity and will be paid for at the contract unit price for unbonded concrete overlay. The plan quantity included in the contract should account for the additional concrete material in excess of the specified overlay thickness. This will require the designer to estimate what these quantities are during the field check, to avoid an overrun in project cost. It is recommended the field check include establishment of a profile line for estimation of concrete material quantity needed. The designer may want to review records of past projects to determine typical quantities greater than the overlay thickness.

If existing asphalt overlays are being removed, a pay item should be included for a EPG 401 bituminous interlayer 1 in. thick. If existing asphalt is partially removed and at least 2 in. of existing asphalt remains over the existing concrete, the pay item for surface preparation should be included and no bituminous interlayer is necessary.

506.2 Construction Inspection (for Sec 506)

506.2.1 Ultrathin Concrete Whitetopping (for Sec 506.10)

506.2.1.1 Mix Design (for Sec 506.10.3)

Mix Approval (for Sec 506.10.3.1)

The contractor shall submit a mix design to District Materials for review and approval. Representative samples may need to be sent to Construction and Materials for laboratory testing.

506.2.1.2 Construction Requirements (for Sec 506.10.4)

Opening to Traffic (for Sec 506.10.4.6)

See Sampling

506.2.1.3 Method of Measurement (for Sec 506.10.5)

Pavement Thickness Determination (for Sec 506.10.5.3)

(Sec 506.10.5.3.1) Measurements for pavement thickness should be taken at random locations at approximately 200 ft. intervals per each 12 ft. lane. Additional measurements should be taken if the inspector has reason to believe that the pavement is deficient in thickness.

506.2.2 Portland Cement Concrete Unbonded Overlay (for Sec 506.20)

506.2.2.1 Description (for Sec 506.20.1)

Because of the field established plan quantity requirement, Contractor Furnished Staking should be set up in the contract. The contractor should provide enough information to establish the initial and final roadway profile in order to calculate this quantity. This information should include centerline and edgeline elevations at intervals acceptable to the resident engineer. The resident engineer should insure that the minimum overlay thickness is at the plan thickness.

506.2.2.2 Material (for Sec 506.20.2)

Debonding Material (Sec 506.20.2.1) This debonding material also helps control heat between the base surface and the unbonded overlay.