Degree of Compaction and its effects on

Degree of Compaction and its effects on
Cost and Life of Roads in Brunei Darussalam
by
Dr. S. A. Sultan 1 and Mr.Wee Hong Joo 2

ABSTRACT
The performance of a pavement system involves the interaction of many variables such as material
properties, environment, traffic loading, construction practices, maintenance activities, and
management constraints. The pavement design process has as its objective, the design and
management of a pavement throughout its life time in order to minimize the total cost. This
approach, can be used to select an optimum pavement strategy considering the interaction of these
many variables.
A comprehensive analysis was carried out using local values of the above mentioned variables in
Brunei Darussalam to study the effect of degree of compaction of pavement layers on the optimum
pavement management strategy. This analysis was implemented using mechanistic-empirical
design approach. Different relationships were developed to find the effect of the degree of
compaction on the total cost of the pavement, maintenance cost, the time to the first overlay, and the
total life of the road. These effects will be presented into mathematical relationships or models to
help the road engineers and contractors in understanding and assessing the required degree of
compaction for their pavement layers.
2.


INTRODUCTION

2.1

Background

Pavement design is normally a inquisitive process in which the designer assumes a certain
combination of thickness of layered materials and subsequently checks the layered systems for
adequacy from the points of view of traffic and environmental deterioration, construction and
rehabilitation costs, as well as the future seal costs, overlays and routine maintenance (AASHTO,
1986).
In the course of this analysis, a designer may see areas in which he could improve the over-all cost
by making modifications in his trial designs.
_____________________________________________________________________________
1
Consultant, Associated Consultant Pte. Ltd., P.O. Box 697, Bandar Seri Begawan BS8671, Brunei
Darussalam, e-mail: sasultan@brunet.bn
2


Engineering Manager, Associated Consultant Pte. Ltd., P.O. Box 697, Bandar Seri Begawan
BS8671, Brunei Darussalam

With the variety of materials and thickness available to highway designer, A computer program is
normally required to consider between one and two thousands different trial designs. The material
properties, the traffic, and environmental factors are combined to predict a time at which the
serviceability index of the pavement would drop below an acceptable level (Huang, 1993).
The development of an operational pavement systems model using a computer program called
SAMP, System Analysis and Management of Pavement simplified the process, (Lytton et. al., 1975).
The SAMP computer program was developed from Flexible Pavement System (FPS) - 4, one of the
FPS - series computer programs written for implementation within the Texas Highway Department.
Two structural subsystems, the AASHO Interim Guide flexible pavement equation and the
deflection equation, were represented in the FPS series.
The SAMP computer program adopts the view that routine maintenance and future rehabilitation
(overlay) are part of the total pavement management process (Sultan and Joo, 2000). Future costs
are discounted to the present and the total cost per square meter is used, as the criterion for
determining which pavement design is the optimum. Included in the total cost is the users cost, a
term for the expense to the traveling public of being delayed while detouring on overlay activity.
These costs are weighted equally with actual construction dollars.
The purpose of the Pavement Management System PMS analysis is to design from available input

data, a pavement that can be maintained above specified minimum serviceability over the specified
design period at a minimum over-all cost. The PMS provides the decision-maker with a set of
feasible pavement designs arranged in some priority order- in the present case, that of increasing
total cost. The information provided for each alternate design includes (1) initial construction
configuration, (2) overlay schedule and (3) cost breakdown. The cost breakdown includes initial
construction, overlays, routine maintenance, salvage value, and user’s costs during overlay
construction. All costs are discounted to present value using the interest rate selected by the program
user. The system was implemented taking into consideration the local construction practices and the
magnitude of the input variables in Brunei Darussalam to study the effect of compaction degree of
pavement layers. The following procedure was followed (Sultan, 1999a; Sultan 1999b; Sultan,
1999c;Tong, 1997).
2.1.1 The Input Data.
ACost of Materials
For the purpose of this analysis, the local market prices were taken for comparison purposes
only as shown in Table 1 (Hj Abd Rahman and Sultan, 2000).

BMaterial Characterization
In this analysis, four different types of pavement materials were used to design pavement
layers as shown in Table 2. Each one of the materials used has its own layer coefficient and
other strength properties according to AASHTO design method (AASHTO, 1986).


Table 1: Input Variables for SAMP Analysis.
MATERIALS
ILAYER
CODE
1
A
2
B
3
C

COST
STR.
MIN.
MAX
SALVAGE
NAME
RM / m3
COEFF.

DEPTH (cm)
DEPTH. (cm)
VALUE
ASH
60.00
.44
5.00
5.00
.00
M.BI
65.00
.32
10.00
25.00
.00
SAND
18.00
.09
10.00
25.00

.00
SUBG
.00
.00
.00
.00
PROGRAM CONTROL AND MISCELLANEOUS VARIABLES
THE TOTAL NUMBER OF MATERIALS AVAILABLE EXCLUDING SUBGRADE
THE LENGTH OF THE ANALYSIS PERIOD (YEARS)
THE WIDTH OF EACH LANE (METER)
THE INTEREST RATE OR TIME VALUE OF MONEY (PERCENT)
ENVIRONMENTAL AND SERVICEABILITY VARIABLES
THE SERVICEABILITY INDEX FOR THE INITIAL STRUCTURE
THE SERVICEABILITY INDEX OF ANY OVERLAY
THE MINIMUM ALLOWED VALUE OF THE SERVICEABILITY INDEX (POINT AT WHICH AN
OVERLAY MUST BE APPLIED)
THE LOWER BOUND ON THE SERVICEABILITY INDEX WHICH WOULD BE ACHIEVED IN INFINITE
TIME WITH NO TRAFFIC
THE RATE AT WHICH NON-TRAFFIC FACTORS REDUCE THE SERVICEABILITY INDEX
LOAD AND TRAFFIC VARIABLES

THE ONE-DIRECTION AVERAGE DAILY TRAFFIC AT THE BEGINNING OF THE ANALYSIS PERIOD
THE ONE-DIRECTION AVERAGE DAILY TRAFFIC AT THE END OF ANALYSIS PERIOD.
THE ONE-DIRECTION ACCUMULATED NUMBER OF MEQUIVALENT 18 KIP AXLES
DURING THE ANALYSIS PERIOD.
THE PERCENT OF ADT WHICH WILL PASS THROUGH THE OVERLAY ZONE DURING EACH HOUR
WHILE OVERLAYING IS TAKING PLACE
THE TYPE OF ROAD UNDER CONSTRUCTION (1-RURAL, 2-URBAN)
CONSTRAINT VARIABLES
THE MINIMUM ALLOWED TIME TO THE OVERLAY
THE MINIMUM ALLOWED TIME BETWEEN OVERLAYS
THE MAXIMUM FUND AVAILABLE FOR INITIAL CONSTRUCTION
THE MAXIMUM ALLOWABLE TOTAL THICKNESS OF INITIAL CONSTRUCTION
THE MINIMUM THICKNESS OF AN INDIVIDUAL OVERLAY
THE ACCUMULATED MAXIMUM THICKNESS OF ALL OVERLAYS
TRAFFIC DELAY VARIABLES ASSOCIATED WITH OVERLAY AND ROAD GEOMETRIC
ASPHALTIC CONCRETE PRODUCTION RATE (TONS/HOUR)
ASPHALTIC CONCRETE COMPACTED DENSITY (TONS/COMPACTED M3)
THE DISTANCE OVER WHICH TRAFFIC IS SLOWED IN THE OVERLAY DIRECTION
THE DISTANCE OVER WHICH TRAFFIC IS SLOWED IN THE NON-OVERLAY DIRECTION
THE DISTANCE AROUND THE OVERLAY ZONE (km)

THE NUMBER OF HOURS/DAY OVERLAY CONSTRUCTION TAKES PLACE
TRAFFIC DELAY VARIABLES ASSOCIATED WITH TRAFFIC SPEEDS AND DELAYS
THE PERCENT OF VEHICLES THAT WILL BE STOPPED BECAUSE OF THE MOVEMENT OF
PERSONNEL EQUIPMENT.
IN THE OVERLAY DIRECTION
IN THE NON-OVERLAY DIRECTION
THE AVERAGE DELAY PER VEHICLES STOPPED BECAUSE OF THE MOVEMENT OF PERSONNEL
AND EQUIPMENT
IN THE OVERLAY DIRECTION (HOURS)
IN THE NON-OVERLAY DIRECTION (HOURS)
THE AVERAGE APPROACH SPEED TO THE OVERLAY AREA(km/h)
THE AVERAGE SPEED THROUGH THE OVERLAY AREA(km/h)
IN THE OVERLAY DIRECTION (km/h)
IN THE NON-OVERLAY DIRECTION (km/h)
THE TRAFFIC HANDLING MODEL USED
MAINTENANCE VARIABLES
THE NUMBER OF DAYS PER YEAR THAT THE TEMPERATURE REMAINS BELOW ZERO C
THE COMPOSITE LABOR WAGE
THE COMPOSITE EQUIPMENT RENTAL RATE
THE RELATIVE MATERIAL COST (1.00 IS AVERAGE)


MODULUS
MPa
3500
2200
70.00
30.00
3
20.
3.75
5.0
4.0
4.0
2.5
1.5
.120

6687.
7743.
7196682.

5.0
1
1.5
3.0
100.00
32.0
.00
3.0
100.0
1.80
1.0
1.0
.00
5.0

5.00
5.00

.200
.200

50.
50.00
50.00
3
0.
15.00
25.00
1.00

Table 2: Different Combinations of Pavement
Layers used for Analysis.
A1

0.44

MATERIAL
A1 (A)

A2

MATERIAL
A2 (B)

0.32

MACADAM BIT (1)

0.22

MACADAM BIT. (2)

0.18

AGG. + CEMENT

0.13

CRUSHED AGG.

ASP.CON.

A3
0.09
0.10
0.11
0.09
0.10
0.11
0.09
0.10
0.11
0.09
0.10
0.11

MATERIAL
A3 (C)
SAND
CRUSHED AGG.
AGG + CEMENT
SAND
CRUSHED AGG.
ACC + CEMENT
SAND
CRUSHED AGG.
AGG .+ CEMENT
SAND
CRUSHED AGG
AGG. + CEMENT

TYPE
A
B
C
D
E
F
G
H
I
J
K
L

CDesign Period
In this analysis, an average design period of 15 years was used for comparison purposes, as
the life of the road pavement.
DTraffic Volumes
A typical traffic volume data was taken from an average arterial road for the purpose of
analysis as shown in Table 1.This data was converted into 18-kip ESAL (Equivalent Single
Axle Load) as required by AASHTO design method.
EOthers
The salvage value of pavement materials was taken as zero according to the local practice
(based on local market prices). The other values were taken as averages or as considered by
local road industry practice, as shown in Table 1.

F-

Summary

For the purpose of this analysis, different degrees of compaction were taken for each of
asphalt, base, subbase and subgrade layers to evaluate the effects of degree of compaction
using a developed version of SAMP computer program, (Sultan and Lou, 2000).
3.

ANALYSIS OF RESULTS.

Fig.1 is prepared to show the output relationship between the degree of compaction of the subgrade
soil and the total cost of the road pavement. Decreasing the degree of compaction of subgrade soil
from 100% to 90% increases sharply the total cost of the pavement (total cost includes construction
cost, routine maintenance cost, and overlay cost for total life of 15 years) from $B 11.5 per square
meter to $B 15.5 per square meter, or by 5% for each 1.0% reduction in degree of compaction. The
degree of compaction required by design method is 95%.

y=132.556-2.829*x
102
100

Dc (%)

98
96
94
92
90
88
11.0

11.5

12.0

12.5

13.0

13.5

14.0

14.5

15.0

15.5

Tc ($B/m2)
Fig.1: Relationship between Degree of compaction (Dc) of subgrade soil
and the Total cost (Tc) of the pavement in $B/m2.

Fig.2 is prepared to show the effect of the degree of compaction of the subgrade soil layer on the
resilient modulus and the maximum dry density. It is well known that reducing the degree of
compaction of the subgrade soil layer reduces the resilient modulus and the dry density of soil,
(AASHTO, 1986), but the relationship which defines the rate of this reduction for a certain
environment is not known, (Huang, 1993). The literature review that have been carried out by Tong
(1997) laid open that this type of relationship is not available.
Fig.3 shows the effect of the degree of compaction on the total cost of the pavement and the dry
density of the subgrade soil.
Fig.4 is prepared to show the effect of the degree of compaction of the subbase layer on the total cost
of the pavement. The degree of compaction of the subbase layer has less effect on the total cost of
the pavement in comparison with the rest of layers. This can be attributed to the main function of the
subbase layer as a non major load carrying layer and it serves mainly as drainage layer.
Fig.5 is prepared to show the effect of the degree of compaction of the base layer on the total cost of
the pavement.
Fig.6 is prepared to show the effect of the degree of compaction of the asphalt layer on the total
pavement cost. The most important effect on the cost of the pavement by the degree of compaction
can be recognized in Fig.6.
Fig.7 is prepared to show the relationship between the time to the first overlay and the degree of
compaction of asphalt layer. Decreasing the degree of compaction of asphalt layer from 100% (or
98% following the design standard) to 95% reduces the time to the first overlay from 4 years to 1.5
years.

z=65.17+0.012*x+0.321*y

Fig.2: Relationship for Maximum Dry Density (MDD), Resilient
Modulus (RM), and Degree of Compaction (Dc) of subgrade soil.

90.500
91.581
92.662
93.743
94.824
95.905
96.986
98.067
99.148
100.229
above

z=96.402+0.015*x+-2.039*y

Fig.3: Relationship for Maximum Dry Density (MDD), Total cost (Tc),
and Degree of Compaction (Dc) of subgrade soil.

90.500
91.581
92.662
93.743
94.824
95.905
96.986
98.067
99.148
100.229
above

102
100

Dc (%)

98
96
94
92
90
88
10.9

11.1

11.3

11.5

11.7

11.9

Tc ($B/m2)
Fig.4: Relationship between Degree of Compaction (Dc) of subbase layer
and the Total cost (Tc) of the pavement.

102
100

Dc (%)

98
96
94
92
90
88
11.0

11.4

11.8

12.2

12.6

Tc ($B/m2)
Fig.5: Relationship between Degree of Compaction (Dc) of base layer
and the Total cost (Tc) of the pavement.

13.0

100.5

99.5

Dc (%)

98.5

97.5

96.5

95.5

94.5
11.0

11.6

12.2

12.8

13.4

14.0

Tc ($B/m2)
Fig.6: Relationship between Degree of Compaction (Dc) of asphalt layer
and the Total cost (Tc) of pavement.

100.0
99.5
99.0

Dc (%)

98.5
98.0
97.5
97.0
96.5
96.0
95.5
1.6

2.0

2.4

2.8

3.2

3.6

To (years)
Fig.7: Relationship between Degree of Compaction (Dc) of asphalt layer
and the Time to first overlay (To).

4.0

4.

CONCLUSIONS

The importance of the degree of compaction of the pavement layers during construction is not only
as a quality controlling measure, but it is also a factor that controls the total cost of the road
pavement and its design life. New relationships were developed to define the effect of the degree of
compaction on the total pavement cost, life and performance in Brunei Darussalam with high
correlation factors for confidence level of 95%. These relationships will help road engineers and
contractors to understand and evaluate the negative effects of the reduction of degree of compaction
on the total cost and life of road pavement.
References
AASHTO, (1986), AASHTO, “Guide for Design of Pavement Structures”, Washington, D.C.,
USA.
Hj Abd Rahman, Hj. R., and Sultan, S.A., (2000), “ New Techniques for Design and Quality Control
of Pavement Stabilization in Brunei Darussalam.”, Proc. the 10th REAAA Conf., Tokyo, Japan.
Huang, Y. H., (1993), “ Pavement Analysis and Design”, Prentice Hall, Inc., New Jersey, USA,
pp.805.
Lytton, R.L., et. al., (1975), “Flexible Pavement Design and Management Systems Approach
Implementation”, NCHRP Report 160.
Sultan, S.A., and Lou, C., T., (2000), “ New Approach for Pavement Management System in
Borneo Island”, Proc. the 10th REAAA Conf., Tokyo, Japan.
Sultan, S.A., and Joo, W. H., (2000),“ Minimum Maintenance Approach for the Design of Flexible
Pavement in The Tropics”, Proc. the 10th REAAA Conf., Tokyo, Japan.
Sultan, S.A., (1999a), “One Day Seminar on Flexible Road Pavement”, The Institution of Engineers,
Malaysia, (IEM), Sarawak branch, Kuching, Malaysia.
Sultan, S.A, (1999b), “Two Day Seminar on Road Construction over Peat and New Techniques for
Design and Quality Control of Stabilized Pavement”, The Institution of Engineers, Malaysia, (IEM),
Sarawak Branch, Kuching, Malaysia.
Sultan, S.A., (1999c), “One Day Seminar on Design and Quality Control of Stabilized Pavements”,
The Institution of Engineers Malaysia, (IEM), Sabah branch, Sabah, Malaysia.
Sultan, S.A.,(1999d), “One Day Seminar on Road Maintenance in The Tropics”, Kuching, The
Association of Consulting Engineers, Malaysia, (ACEM), Sarawak, Malaysia.
Tong, L.N., (1997),”New Pavement Management System for Flexible Pavements in Malaysia”,
B.Sc graduation project dissertation, Department of Civil Engineering, University Malaya, Kuala
Lumpur, Malaysia.