chapter 3 rigid pavement - DOT On-Line Publications - Department ...

SAMPLING AND CORING PROCEDURES
Number of Projects: Since three dowel inserter projects were
available for evaluation, three additional independent projects
using dowel baskets were also selected for this study. The
comparison section with dowel baskets on the I-90 Janesville
dowel inserter project was not included in this study due to
reports from field personnel that unusual care k'as taken in
placing the baskets on that project. The six projects that were
selected for this study are described in Table 1.
Wmber of Dowels ner Proiect: To achieve good statistical
reliability while keeping costs and coring damage down to a
reasonable level, a nominal sample size of 90 dowels per project
was selected.
Jocation of Test Joints: The test joint locations on each
project were selected in such a manner so that a representative
sample would be collected. The optimum procedure would have been
to select joints at random intervals throughout the project, but.
traffic control cost constraints dictated the need to concentrate
the testing in limited test sections. Three test sections were
designated for each project. The test sections were located a
mile apart, and were located in the central portion of the
project. Spreading the test sections out in this manner assured
that all test joints would not fall in a single isolated problem
area of the project. Central location of the test sections on
the project assured that samples would not be taken near the ends
of the project, where "start-up" paving problems typically occur.
The location of the starting points for each of the test sections
on each of the projects are given in Table 2.
A total of 15 test joints were designated in each test section.
To assure equal rotation through the C-joint repeating random
skewed joint spacing pattern, every third joint in the test
section was designated as a test joint.
Location of Test Dowels in Test Joints: At each test joint, one
dowel was tested in the passing lane, and one dowel was tested in
the driving lane. This was done to assess the relative placement
error as it varied across the test joint. On the South Madison
Beltline project, which had three lanes per direction, testing
was confined to the two adjacent lanes (closest to the median)
which were paved simultaneously with the dowel bar inserter.
The lateral position of each of the dowels across the pavement
was identified by numbering the dowels for each lane in ascending
order from the shoulder to the longitudinal joint between the two
lanes, as shown in Figure 1. The lateral position of the test
dowels for all successive test joints on a project was determined
by rotating through the random number sequence shown in Table 3.
This assured even representation in the sample for all dowel
positions across the lanes.
3.5.8