Field compaction of asphalt mixtures is an important process that influences
performance of asphalt pavements; however there is very little effort devoted to evaluate
the influence of compaction on the uniformity and properties of asphalt mixtures. The
first part of this study evaluated relationships between different field compaction patterns
and the uniformity of air void distribution in asphalt pavements. A number of projects
with different asphalt mixture types were compacted, and cores were taken at different
locations from these projects. The X-ray Computed Tomography (X-ray CT) system was
used to capture the air void distributions in these cores. The analysis results have revealed
that the uniformity of air void distribution is highly related to the compaction pattern and
the sequence of different compaction equipment. More importantly, the efficiency of
compaction (reducing air voids) at a point was found to be a function of the location of
this point with respect to the compaction roller width. The results in this study supported
the development of the "Compaction Index (CI)," which quantifies the degree of field
compaction. The CI is a function of the number of passes at a point and the position of
the point with respect to the compaction roller width. This index was found to correlate
reasonably well with percent air voids in the pavement. The CI calculated from field
compaction was also related to the slope of the compaction curve obtained from the
Superpave gyratory compactor. This relationship offers the opportunity to predict field
compactability based on laboratory measurements. The compaction of longitudinal joints
was investigated, and recommendations were put forward to improve joint compaction.
The air void distributions in gyratory specimens were related to the mixture mechanical
properties measured using the Overlay and Hamburg tests. The second part of this study focused on studying the relationship between air
void distribution and moisture diffusion. A laboratory test protocol was developed to
measure the diffusion coefficient of asphalt mixtures. This important property has not
measured before. The results revealed that the air void phase within the asphalt mixtures
controls the rate of moisture diffusion. The measured diffusion coefficients correlated
well with the percent and size of connected air voids. The measured diffusion coefficient
is a necessary parameter in modeling moisture transport and predicting moisture damage
in asphalt mixtures.
The last part of this study investigated the resistance of asphalt mixtures with
different percent air voids to moisture damage by using experimental methods and a
fracture mechanics approach that accounts for fundamental material properties.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2008-12-242 |
| Date | 2008 December 1900 |
| Creators | Kassem, Emad Abdel-Rahman Ahmed |
| Contributors | Masad, Eyad |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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