1 Mar 98
(7) Lessons Learned
(a.) This paragraph highlights important details or information that were gained during the
design and construction of this project. Central plant (pugmill mixing) provides superior mixing
when compared to in-place mixing of materials. The placement of these materials with a
conventional asphalt paver proved very successful in obtaining desired grades and surface
smoothness and in preventing mixture segregation. Large pieces of RAP material proved difficult
to break up and required many passes of the pulvermixer to achieve the desired sizes. The cold
weather, over the winter, allowed the contractor to crush the RAP into particle sizes of 50 mm
(2 in.) or less. In anything but sub-freezing temperatures, especially with soft asphalt cements
used in the area, crushing of the RAP would not have been possible. The smaller size of the RAP
made it possible to mix the materials in a pugmill. The procedures used resulted in an excellent
pavement for low intensity traffic.
(b.) Recent laboratory evaluation showed that the two mixtures contained near optimum
asphalt content and other mixture properties, indicating that satisfactory performance could be
expected. When the surface mixture was placed on a heavily trafficked quarry road with a
suitable amount of base course it developed minimal distress and was providing a suitable riding
surface. This would indicate that with high quality materials (RAP and asphalt cement) and good
mixture design, construction procedures, and quality control, a high quality base or intermediate
course for pavements can be constructed.
(a.) The source of the contaminated materials on Guam included a large number of old
rusting and leaking 55 gal drums containing asphalt cement and other petroleum materials. WES
did an evaluation of the petroleum materials from samples obtained from several barrels and
learned that the majority contained an asphalt cement similar in properties to an AC 20. A small
number of the barrels contained a cutback asphalt cement equivalent to an MC 70. There were
over 200 barrels of the asphalt materials and the cost to encapsulate each barrel inside another
container and ship them for disposal was estimated at over 1 million dollars.
(b.) WES performed mix designs using these asphalt materials and local aggregates for both
hot- and cold-mix asphalt concrete mixtures. The base decided to use the cutback material as a
prime and a tack coat and use the asphalt cement to produce hot-mix asphalt. Two parking lots
were paved with these materials.
(c.) Rather than paying the cost of disposal, the base was able to use these asphalt materials
in pavement construction, turning a cost into a benefit. The parking lot pavements are performing