Geosynthetics June/July 2019 - 26

Using geosynthetics in flexible airport pavements

Sieve Designation

Percent by Weight Passing Sieve
AC 150/5370-10H

Phase I

Phase II

3 inch (75 mm)

100

100

100

3/4 inch (19 mm)

70-100

100

100

No. 10 (2 mm)

20-100

86.5

91

No. 40 (425 μm)

5-60

46.3

51

No. 200 (75 μm)

0-8

0.2

0.1

Coefficient of Curvature (Cc )

0.4

0.7

Coefficient of Uniformity (Cu )

2.89

6

TABLE 1 Twelve inches (305 mm) of P-154 subbase gradation comparison

Sieve Designation

Percent by Weight Passing Sieve
AC 150/5370-1011

Phase I

Phase II

3 inch (75 mm)

100

100

100

1 1/2 inch (37.5 mm)

95-100

100

100

1 inch (25 mm)

70-95

96

84

3/4 inch (19 mm)

55-85

91

80

No. 4 (4.75 mm)

30-60

54

28

No. 40 (425 μm)

10-30

15

8

No. 200 (75 μm)

0-8

10

5

Coefficient of Curvature (Cc )

9.08

2.71

Coefficient of Uniformity (Cu )

80.09

21.2

Maximum Dry Density (pcf )

144.7

146.7

Optimum Moisture (%)

4.9

5.9

TABLE 2 Seven inches (178 mm) of P-209 aggregate base gradation comparison

incorporating various geosynthetic products at the base course/subbase interface, while Phase II, completed in 2018,
included six test items incorporating various geosynthetic products at the subbase/
subgrade interface.

Pavement material
placement and properties
The subgrade material was constructed
using a locally available clay, known as
Vicksburg buckshot clay. The clay soil
liquid limit, plastic limit and plastic
index were 90, 28 and 62 respectively,
which classifies as a high-plasticity clay
26

Geosynthetics | June July 2019

(CH) per the Unified Soil Classification
System (USCS). Modified Proctor test
per American Society for Testing and
Materials (ASTM) D1557, Method C for
Phase I and Phase II, yielded a maximum
dry density of 101.4 pcf (1,624.3 kg/m3)
and 102.4 pcf (1,640.3 kg/m3) at a target
optimum moisture of 19.8% and 22.8%,
respectively. The material was placed and
compacted at a target moisture of 38%
to achieve a desired California Bearing
Ratio (CBR) of 3.0%.
Subbase material was constructed
using a locally available granular material
meeting the gradation requirements of
P-154 per draft FAA Advisory Circular
150/5370-10H, as shown in Table 1. Per
ASTM D2487, the Phase I and Phase II
granular subbase materials were classified
as poorly graded sand (SP) and wellgraded sand (SW), respectively.
Aggregate base course material was
constructed using locally available material
known as 610 crushed limestone, closely
representing the gradation requirements
of P-209 per draft FAA Advisory Circular
150/5370-10H, as shown in Table 2. Per
ASTM D2487, the Phase I and Phase II
aggregate base materials were classified as
a poorly graded gravel with silt and sand
(GP-GM) and well-graded gravel with silt
and sand (GW-GM) per USCS respectively. Modified Proctor compaction tests
were performed in accordance with ASTM
D1557, Method C. A summary of Phase I
and Phase II aggregate base test results are
shown in Table 2.
The HMA pavement surface course
was constructed using a locally available 0.5-inch (12.7-mm) nominal maximum aggregate size (NMAS) mixture,
using a PG 67-22 asphalt binder content
of approximately 5.3%. A comparison
of the mix design and the FAA P-401
per Advisory Circular 150/5370-10H
is shown in Table 3. For constructability purposes and to reduce variability,
the asphalt was placed and compacted
Geosynthetics June/July 2019

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