Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 30
30
conditioned for at least 4 hours at the test temperature. Sam- four residual application rates--0 (No Tack), 0.031, 0.062,
ples were then placed in the testing chamber while attempt- 0.155 gal/yd2. Field-cored specimens for tack coat applied
ing to minimize temperature loss (Figure 22b) and were then between new and new HMA surfaces were available for
conditioned for 30 minutes at the target temperature to com- SS-1h tack coat. Sample sizes and other test conditions were
pensate for temperature loss during specimen placement in the the same as field-cored sample testing. Laboratory-fabricated
LISST device (Figure 22c). Finally, shear load was applied by specimens consisted of two layers, with a tack coat at the
the shear loading frame at a loading rate of 2.54 mm/sec until interface of these layers. The diameter of each specimen was
failure, as shown in Figure 22d. 4.0 in. The bottom half of each specimen was prepared by
compacting the mixture to a height of 2.0 in at 150°C using
the Superpave Gyratory Compactor (SGC). The compacted
3.7Experiment Plan V: Effects of
specimen was then allowed to cool to room temperature, and
Pavement Surface Type and
its air void content was measured. Compacted bottom halves
Sample Preparation Method
having an air voids content of 6 ±1 percent were prepared.
Experiment V was designed to measure and compare the The asphalt materials used as tack coat were then heated to
interface shear strength for different surface types and sample the specified application temperature. The calculated amount
preparation methods. For this purpose, samples were pre- of the preheated tack coat was then uniformly applied on the
pared to simulate different field conditions and were tested bottom half of the specimen using a brush. Once application
using the LISST device. Table 8 presents the field test matrix. of the tack coat was complete, it was allowed to cool to room
Four types of field pavement surfaces and five tack coat temperature and the top half of the sample was compacted
materials were evaluated. However, only one emulsion (SS-1h) by placing the bottom half in the SGC mold and compacting
was used on the new HMA surface and two emulsion grades loose mix on top of the tack-coated bottom half.
(SS-1h and SS-1) were used on the milled surface. Four resid-
ual application rates were selected including, zero (no tack)
3.8Experiment Plan VI: Effects
application rate. The effects of rainy and dusty conditions
of Surface Texture and
during construction operations were simulated for the differ-
Permeability on Interface
ent surface types as part of this experiment. Test temperature
Shear Strength
and the tack coat coverage rate were kept constant at 25°C
and 100% coverage, respectively. To assess variation in the The objective of this experiment was to evaluate the effects
results, triplicate samples were tested for each condition; of surface texture and permeability on tack coat interface
375 samples were tested as part of the test matrix. shear strength using laboratory-prepared specimens. Three
To assess the influence of sample preparation methods, mixture types with different texture and permeability com-
laboratory-fabricated specimens were prepared using five positions (see Table 9) were considered to use as the layer on
tack coat materials--SS-1h, trackless, locally-used trackless which the tack coat was applied. Table 10 presents the mix
(AUT), PG 64-22, and CRS-1--as tack coat was applied at designs adopted in the preparation of the three mix types.
Table 8. Test factorial for field-prepared samples.
Variables* Content Levels
Old HMA, new HMA, grooved PCC,
Pavement surface type 4
milled HMA
Tack coat material SS-1h, SS-1, CRS-1, Trackless, PG 64-22 5
2
Residual application rate 0- (No-Tack), 0.031-, 0.062-, 0.155-gal/yd 4
Wetness (Rain) condition Wet, Dry 2
Cleanliness condition Dusty, Clean 2
Test temperature 25°C 1
Confinement pressure (psi) 0, 20 2
Tack coat coverage 50%, 100% 2
Number of replicates 3 3
Total Number of Samples 474
* Some variables were partially evaluated according to the test factorial.
OCR for page 31
31
Table 9. Test matrix to evaluate effects of texture and permeability on
SS-1 tack coat.
Residual No. of
Mixture Texture
Permeability Tack Coat Application Rate Tested
Type Roughness
(gsy) Specimens
0.000 3
0.031 3
Sand Low Low SS-1
0.062 3
0.155 3
0.000 3
High 0.031 3
SMA Low SS-1
0.062 3
0.155 3
0.000 3
Open-graded
friction 0.031 3
High High SS-1
course 0.062 3
(OGFC)
0.155 3
Table 10. Job mix formula.
Mixture Type Sand SMA OGFC
Binder Type PG 70-22 PG 76-22 PG 76-22
Binder Content (%) 6.0 6.2 6.5
Air Voids (%) 13.2 3.5 21.2
Aggregate Gradation
Sieve Size % Passing
37.5 mm (1½ in) 100 100 100
25 mm (1 in) 100 100 100
19 mm (¾ in) 100 100 100
12.5 mm (½ in) 100 93 95
9.5 mm ( in) 100 66 67
4.75 mm (No.4) 97 29 17
2.36 mm (No.8) 90 23 8
1.18 mm (No.16) 81 19 6
0.6 mm (No.30) 66 18 5
0.3 mm (No.50) 25 15 5
0.15 mm (No.100) 8 12 4
0.075 mm (No.200) 4 8.8 3
