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OCR for page 22
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TABLE 13 t/NMAS, temperature in C at 20 min., gyrations were increased up to 300 gyrations. This shows the
asphalt high temperature grade, and difference in difficulty of compacting mixes at thinner lifts in the gyratory
temperature mold. Permeability testing was only performed on specimens
Section/Mix Temp. at Asphalt Difference that met the desired air voids. The results were very limited,
20 min., °C Grade, PG but, did show that generally the coarser mixes (larger maxi-
1 2.5 60 67 -7
mum aggregate size or higher percentage of coarse aggregate)
9.5mmFG 3.6 82 67 15
5.1 95 67 28 had higher permeabilities.
2 2.1 64 67 -3
9.5mmCG 2.4 72 67 5
5.1 105 67 38
3 2.2 65 76 -11 4.7 EVALUATION OF EFFECT OF t/NMAS
9.5mmSMA 3.7 100 76 24 ON PERMEABILITY USING
5.2 112 76 36 VIBRATORY COMPACTOR
4 2.2 72 76 -4
12.5mmSMA 3.1 118 76 42 All specimens compacted at t/NMAS of 2.0, 3.0, and 4.0 did
3.8 120 76 44 achieve the target air void content, which was 7 ± 1.0 percent.
5 2.6 124 67 57
19mmFG 3.0 122 67 55
Figure 34 shows the relationship between average permeabil-
5.2 130 67 63 ity for the two aggregate types and t/NMAS. In general, the
6 2.1 82 67 15 permeability decreased as t/NMAS increased. Most of the
19mmCG 3.2 120 67 53 mixes had permeability values fewer than 50 × 10-5 cm/sec.
5.1 118 67 51
7 2.7 86 76 10
However, at t/NMAS equal to 2.0, the 9.5-mm and 12.5-mm
19mmCG 3.8 120 76 44 NMAS SMA mixes had average permeability values of 173
5.2 142 76 66 × 10-5 cm/sec and 196 × 10-5 cm/sec, respectively. These
values for the SMA exceed the recommended maximum
permeability value of 125 × 10-5 cm/sec. It appears from these
4.6 EVALUATION OF EFFECT OF t/NMAS
data that a specification requirement of 7 percent air voids
ON PERMEABILITY USING
GYRATORY COMPACTOR would be acceptable for all of the mixes if the t/NMAS is
3 or greater. The likely reason that the thinner samples have
Specimens were compacted to 7.0 ± 1.0 percent air void high permeability is that the voids are more likely to be inter-
content at t/NMAS of 2.0, 3.0, and 4.0. For most mixes, spec- connected all the way through the samples when the samples
imens could not achieve the target air voids even when the are thinner. Hence when mixes are placed thin, in this case
97.5 40
97.0
Steel Wheel Roller 30
96.5 Difference in Temperature
Difference in Temperature, oC
96.0 20
%Lab Density
95.5
10
95.0
%Lab Density Difference in Temperature
94.5 Steel Roller 2
R = 0.9821 0
2
R = 0.6392
94.0
-10
93.5
93.0 -20
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
t/NMAS
Figure 25. Relationships between density, t/NMAS, and temperature for Section 1.
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23
96.0 50.0
Difference in Temperature.
2
95.0 R = 0.998
40.0
94.0
30.0
Difference inTemperature, C
o
93.0
%Lab Density
20.0
92.0
10.0
91.0
%Lab Density
0.0
%Lab Density Steel Roller
90.0
Steel/Rubber Tire Roller 2
R = 0.6796
2
R = 0.5115
-10.0
89.0
88.0 -20.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
t/NMAS
Figure 26. Relationships between density, t/NMAS, and temperature for Section 2.
100.0 50
Difference in Temperature
Steel Wheel Roller 2
99.0 R = 0.976
Rubber Tire Roller 40
%Lab Density
Difference in Temperature Steel Roller
98.0
2
R = 0.8335
30
97.0
Difference in Temperature, C
o
20
96.0
%Lab Density
95.0 10
94.0
%Lab Density 0
Steel/Rubber Tire Roller
93.0 2
R = 0.1864
-10
92.0
-20
91.0
90.0 -30
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
t/NMAS
Figure 27. Relationships between density, t/NMAS, and temperature for Section 3.
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104.0 100
%Lab Density
103.0 Steel Roller
102.0 Steel Wheel Roller 2
R = 0.8711
Rubber Tire Roller 80
101.0
Difference in Temperatur e
100.0
99.0
98.0 60
Difference in Temperature, C
o
97.0
96.0
%Lab Density
40
95.0
94.0 %Lab Density
93.0 Steel/Rubber Tire Roller
2 20
92.0 R = 0.7651
91.0
90.0 0
89.0 Difference in Temperature
2
R = 0.8884
88.0
87.0 -20
86.0
85.0
84.0 -40
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
t/NMAS
Figure 28. Relationships between density, t/NMAS, and temperature for Section 4.
105.0 70
Different in Temperature @ 20 Min.
2
R = 0.8191
104.0
60
103.0
50
102.0
Difference in Temperature, C
o
101.0
%Lab Density
40
100.0
30
99.0
%Lab Density
98.0 Steel Roller 20
2
R = 0.7736
97.0
10
96.0
95.0 0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
t/NMAS
Figure 29. Relationships between density, t/NMAS, and temperature for Section 5.
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25
100 70
Difference in Temperature
2
R = 0.6816
99 60
Steel/Rubber Tire Roller
98 Difference in Temperature 50
Difference in Temperature, °C
%Lab Density
97 40
96 30
95 20
Steel/Rubber Tire Roller
2
94 R = 0.4489 10
93 0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
t/NMAS
Figure 30. Relationships between density, t/NMAS, and temperature for Section 6.
100.0 70
Steel Roller
99.0 60
Steel/Rubber Tire Roller
98.0 Difference in Temperature
50
97.0
40
96.0 %Lab Density
Difference in Temperature,°C
Steel Roller
2 30
95.0 R = 0.6529
%Lab Density
94.0 20
93.0 10
92.0 Difference in Temperature %Lab Density 0
2
R = 0.9904 Steel/Rubber Tire Roller
91.0 2
R = 0.8092
-10
90.0
-20
89.0
88.0 -30
87.0 -40
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
t/NMAS
Figure 31. Relationships between density, t/NMAS, and temperature for Section 7.
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104.0
102.0
100.0
98.0 2
y = -0.8216x + 7.2531x + 80.848
2
R = 0.2562
%Lab Density
96.0
94.0
92.0
90.0
88.0
86.0
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
t/NMAS
Figure 32. Relationships between density and t/NMAS for all sections.
180
25 mm (1.0")
32 mm (1.25")
160 38 mm (1.5")
44 mm (1.75")
140 51 mm (2.0")
64 mm (2.5")
89 mm (3.5")
Temperature of Mix, °C
120
100
80
60
40
20
0
0 10 20 30 40 50 60 70
Time, min.
Figure 33. The effect of layer t/NMAS and cooling time on mix temperature.
