This item includes placing a surface or intermediate course asphalt concrete that is accepted based on the level of density obtained. The specification requires the Contractor to obtain a minimum level of density that is measured based on cores taken from the completed pavement course. In the event the minimum required density is not obtained, there is a deduction to the Contractor’s pay for the item. This type of specification is known as a performance specification. Performance specifications tell the Contractor what is to be achieved, but not necessarily how to perform the work. This differs from standard method specifications that detail exactly how the work shall be performed. For this item, while material and equipment requirements are standard, the method of compaction is not defined; therefore, the Contractor selects the rollers for the course being placed, not ODOT. Under this specification, a Contractor can be rewarded for providing a better product than required by the minimum specification, but as noted above, can be penalized for not meeting the minimum requirements. The requirements of 401 apply unless noted.
Item 446 is accepted by density testing and the roller selection is at the discretion of the Contractor and not governed by 401.13. The requirements of 401.16 that detail compaction operations are waived except the last four paragraphs. These last four paragraphs describe general rolling pattern requirements such as compacting the longitudinal joint first, removal of roller marks, and complete coverage. The Inspector should observe the rolling pattern for conformance.
Density of the asphalt concrete is based on cores that are cut from the completed pavement course. ODOT performs the density testing of these cores at the District Test Lab. Random core locations are determined by the Engineer as detailed in 446.05. Ten, 4 inch cores are required to be cut per lot. A lot is one day (or night) of production with provisions for combining a small production day (<400 tons) with the next day’s lot. Each lot is divided into five equal sublots and two cores are cut from each sublot. Core locations are determined at random by using a random number selection process. That process will be used for all lots and is detailed below.
Cores are required to be cut within 48 hours of placement. To allow the Contractor to core the same day, determine core locations prior to the end of work by estimating production based on production rate and Contractor expectations. The Engineer should only mark the core locations for each sublot after the paving operation (including the finish roller) has completely finished rolling the sublot. The core drill operation can begin cutting cores when the newly placed pavement surface temperature is less than 140 °F. The Department does not intend to bias the Contractor’s operations by specifying where the cores will be taken. In cases where paving is being done under a flagger closure of one lane of a two-lane highway using Standard Construction Drawing MT-97.11 or MT-97.12, some allowance can be made for allowing the paving operation to proceed concurrently with the marking and cutting of cores required for 446 density acceptance. See, Two-Lane Flagger Closure, below for this exception.
If a cold longitudinal joint is made between the mainline and shoulder, include the shoulder area in the lot for coring. If a hot joint is made between the mainline and shoulder, the shoulder is not included in the area to be cored, but the Contractor must use the same equipment and rolling pattern on the shoulder as on the mainline. In this case, it is very important to monitor the rolling pattern on the shoulder. If the Contractor does not adhere to this requirement, include the shoulder in the lot for coring. A hot joint means the Contractor is using two pavers concurrently: one paving the mainline and one paving the adjacent shoulder. Asphalt delivery trucks are alternated between the pavers to maintain a close distance of about one truck load of material.
There are additional, specific requirements for cold longitudinal joint cores. In each lot, three cores are taken from the cold longitudinal joint. One core should be taken in the first and last sublots and randomly one core from one of the middle three sublots. Joint cores are to be 3, 4, or 6 inches from the cold joint depending on its construction type. All other cores are to be located at least 12 inches from the edge of pavement.
Form TE-217 provides a standardized method for sublot layout and random selection of core locations (transversely and longitudinally). The form is located on ODOT’s Construction website and is available as either an Excel spreadsheet that automatically calculates core sample locations or as a manual-use (non-electronic) form.
If using the Electronic TE-217 form After entering the beginning and ending stations for the lot, press key F9 and the computer automatically generates the random numbers. The form automatically calculates the core sample locations as shown in the orange highlighted boxes. Use these locations to lay out the cores on the completed asphalt mat. Note that both forms are set-up for continuous mainline paving and may have to be modified when the paving operation does not continue in a straight line. enter all required information as indicated by the yellow highlighting.
Figure 446.A – Electronic TE-217 Form
For the Non-electronic TE-217 form The selection of random numbers must come from a table. This table is included with the non-electronic all calculations are done manually.TE-217 on the ODOT website as well as instructions for selecting random numbers. The same random number selection method should be used consistently on the project. When this form is completed, use the calculated locations to lay out the cores on the completed asphalt mat.
The Engineer will physically mark the core locations on the mat using aerosol paint. Be sure coring takes place where marked. This can be ensured by observing each coring operation and by painting the core location with a small diameter circle with an “X” or other marking. The Contractor must be instructed to cut the core within this circle. The cut core should be examined to verify there is paint on the surface which indicates the core was cut at the selected location. If the Contractor takes “sister” cores, make sure they are cut within 4 inches longitudinally of the Department’s cores. Sister cores are tested by the Contractor for comparison to ODOT test results. For joint cores, use a different paint color than for the mainline cores. This provides assurance that joint cores are cut from the locations selected by the project.
There have been incidents where cut cores have been switched out with other cores that presumably would provide better density test values. Project personnel must witness the coring operation and take immediate possession of the core from the contractor upon removal, to ensure the cores being tested for payment are from the locations selected by the project through the random selection process. Substitution of cores by cutting in other locations or by replacing cut cores with others is absolutely prohibited and will not be tolerated. No cores for acceptance testing can be taken by the contractor without project personnel present. Project personnel should immediately take possession and maintain custody of all lot samples until shipped to the District lab for testing.
Core holes are required to be filled by the next work day using the same asphalt mixture used to place the mat. The holes must be dry and coated with tack meeting the requirements of 407.02. The asphalt must be compacted adequately and finished flush with the completed asphalt mat. It is important that the core holes are dry and clean prior to tacking and filling. Compaction must be done with a suitable tamper. The sole of a worker’s boot is not a suitable tamper.
After core samples are obtained, package and identify in accordance with current District or Laboratory policy. The District test lab may have specific requirements for labeling the core samples. The samples should be shipped to the District lab as soon as possible. Care should be taken not to damage the core by dropping, throwing, or exposing it to excessive heat. Cores should not be stacked in any way.
In cases where paving is being done under a flagger, closure of one lane of a two-lane highway using Standard Construction Drawing MT-97.11 or MT-97.12, some allowance can be made for allowing the paving operation to proceed concurrently with the marking and cutting of cores required for 446 density acceptance.
In all cases, the Contractor should lengthen their lane closures to the maximum permissible length detailed in the above referenced Standard Construction Drawings to allow the Engineer adequate time to mark the required core locations and for core cutting operations. The Contractor will provide to the Engineer the planned quantity that will be placed for the day’s production.
Follow the requirements above for, “Core Procedures,” with the following changes.
Determine the planned quantity of asphalt that will be placed for that day and determine the core random locations. The Engineer will mark the core locations after the paving operation (including the finish roller) has completely passed the selected core location. The core drill operation can begin cutting cores when the newly placed pavement surface temperature is less than 140 °F. It is the Contractor’s responsibility to maintain the lane closure during all paving, marking, and coring operations per the requirements of the Standard Construction Drawing used for the paving operation.