Environmental Engineering Reference
In-Depth Information
Figure 2. Trial road section: field compaction of
unbound granular base course with lift thickness of
20 cm on a compacted red lapilli subgrade.
Figure 1. stockpiling of volcanic continuous grading
aggregate (cGa) after moistening and mixing.
first test sections a tendency towards a more dif-
ficult densification (decreased unit weights) when
compacting the granular base course on the exist-
ing pavement was verified.
in attempting to validate the utilization of
these volcanic granular materials in untreated
road base courses and the requirements and tests
for field compaction, the object of this work has
been to study the influence of foundation condi-
tions and construction procedures on the rate of
compaction.
2.2 Sampling and laboratory tests
With the aim of verifying the characteristics of
basaltic local material related to field compaction
and to evaluate the effects of densification on its
properties, especially on particle shape and grad-
ing, 7 aggregate samples have been recovered from
exploration pits: one from stockpile after moisten-
ing and mixing, and 3 from each trial road section
after densification.
laboratory testing have included sieve analysis,
flakiness and elongation indexes of coarse aggre-
gate, particle density and water absorption (frac-
tions: 0/4, 4/20 and >20 mm) and Modified Proctor
test with coarse particle correction, according to
Portuguese and spanish standards.
2
eXPeRiMenTal MeThoDoloGY
Two new experimental test sections of about 100 m
each were constructed, where a detailed surveying
program was performed with in-situ testing and
sampling for laboratory tests. in both, conditions
in relation to granular material origin and compac-
tion equipment and procedures have been unmodi-
fied, and therefore only roadbed conditions have
differed.
2.3 In-situ testing
Deflection dynamic response tests with a Falling
Weight Deflectometer (FWD) carl BRo Pri 2100
have been applied to determine differences of
structural performance in the base course support.
20 FWD tests on each experimental road section
had been carried out with load plate diameter of
450 mm, 20 and 40 kn of applied impulse loads,
and 9 deflection sensors (geophones) on two paral-
lel alignments coinciding with the road lane wheel-
paths.
2.1 Test road sections
one experimental road section (station 0 +600 to
0 + 700) included spreading aggregate base on a
compacted lapilli subgrade ( Fig. 2 ). The unbound
crushed stone base has been compacted with lift
thickness of 20 cm and 4, 8, 12, 16, 20, 24, 28, 32
and 36 roller simple passes with a 18.5 T vibrating
roller. The other 100 m long trial section (station
3 +600 to 3 +700) has been constructed with a simi-
lar procedure with the difference of compacting the
aggregate untreated base directly on the aged asphalt
pavement after scarification and re-densification
with 16 vibrating roller simple passes.
3
ResUlTs anD DiscUssion
3.1 Granular material characterization and
comparison with Standard specifications
Geotechnical properties of volcanic aggregates may
suffer frequent and important variations (including
gradation, physical, chemical and mechanical prop-
 
 
 
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