ETL 1110-3-487
1 Mar 98
Environmental Conservation's Guidance Manual for Storage, Remediation, and Disposal of Non-
UST Petroleum Contaminated Soils, dated July 29, 1991.
(c.) The use of a surface treatment on top of the cold-mix RAP surfacing was investigated. It
was not used, partly due to concerns with the short construction season and also in the belief that
sealing the roadway would prevent proper curing and might trap moisture within the recycled
pavement. Local experience has shown that surface treatments have not performed well in this
area.
(5) Construction
Initial in-place mixing methods proved acceptable; however, difficulties due to oversized
materials in the RAP stockpile and the existence of various debris materials in the stockpile
slowed the mixing with the pulvermixer. The subgrade materials were only partially mixed, in that
a loader alternated bucket loads of each material into the dump trucks for transport to the
construction site. A late start and the slowed construction rate resulted in placement of only the
subbase layer during the first year. During the winter the contractor was able to process the RAP
stockpile through a crusher, resulting in a RAP material that was more homogeneous and properly
sized for construction of a ASB. This crushing allowed the RAP material to be mixed in the
pugmill of an asphalt stabilization plant during the second years construction, eliminating the need
for in-place mixing. The pugmill mixing allowed for closer control of the proportions of the
contaminated soil and surface mixtures. Both layers were placed with conventional asphalt
concrete paving and compaction equipment. The minimum compactive effort applied consisted of
at least two passes with a vibratory roller, four passes with a pneumatic roller, and finish rolling
with as many passes with a steel-wheel roller as required to achieve density.
(6) Performance
The use of the materials at this site for pavement construction resulted in substantial savings in
removal and disposal costs. The only distresses noted on the pavement surface were transverse
cracks which occur randomly every 30 to 60 m (100 to 200 ft), minor surface imperfections (open
surface texture, related to mixture design), and some minor surface damage cause by snow plows.
The roadway has provided excellent performance by eliminating the need for occasional grading
(required with the previous gravel surface) and by eliminating dust problems inherent with gravel
roads. The materials placed on the road were only designed to provide an improved surfacing;
however, the resultant surface has provided performance similar to that expected from a hot-mix
asphalt concrete pavement. The contaminated materials provided a satisfactory material for
pavement construction; the roadway has performed very well for almost 4 years. A recent
pavement condition survey (PCI) obtained a value of 87, which categorizes the pavement as being
in excellent condition.
B-9
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