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, enter all
required information as indicated by the yellow highlighting. 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.
Figure 446.A – Electronic TE-217 Form
For the Non-electronic TE-217 form, all
calculations are done manually. The
selection of random numbers must come from a table. This table is included with the
non-electronic 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.
1. In addition to the Documentation Requirements listed
in 401,
use Form
TE-217 to determine and record core locations for each day of production.