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SUMMARY
Andi Alifuddin, Doctoral Program in Environmental Sciences, Post Graduate
Program of Brawijaya University, Absolute Density of Fibers Use On Asphalt
Concrete Mixes In Increasing Tensile Stress, Promotor: Prof. Ir. Antariksa,
M.Eng., Ph.D., co-promotor: Dr. Ir. Pitojo Tri Juwono, MT, and (Alm). Dr. Ir. H.
Iskandar BP, M.Sc.
In Indonesia, asphalt mixture for flexible pavement is designed using Marshall’s
method. The Marshall plan is set for heavy traffic conditions by the sample test
compacting with 2x75 of impact. However, this method is not sufficient to ensure
the performance of asphalt mixtures used for heavy /high traffic with high
temperatures in overcoming the occurrence of premature damage. Damage in
pavement layers is generally affected by large pores due to poor compaction
implementation, effect in water infiltrate through the pavement structure from
cracks and fissures. This phenomenon forms holes in pavement surface. Several
quality control tests show that the suitability of the control parameters in the field
is often not fulfill the requirements in the specification. Moreover, after passage of
traffic within a few years, the cavities in the mixture reach ± 1% leads to a change
in plastic form. Therefore, we need a maximum compacting concept so the
asphalt mixture no longer decreases the cavity due to traffic load.The absolute
density method is intended to be the highest density that can be achieved by the
mixture so that the mixture could not be denser. Compacting method using
Marshall instrument and Percentage Refusal Density (PRD) is conducted to
minimize the pores and cavities of the mixture.
This study aims to examine and analyze the technical properties of asphalt
concrete mixture. The scope of the study includes tensile strength, tensile strain,
resilient modulus (MR), and deformation by addition of fibers using absolute
density compaction method, gyratory compactor, and durability to a modified
immersion. This research was conducted by exprimental method with some
mixed compositions. The implementation of research was done in several stages
of testing. The first phase was preparation of materials and equipment. The
second phase was testing of material characteristics and mechanical properties
of fibers which include treatment with sea water immersion, single fiber tensile
strength test, and morphological analysis of fiber surface shape by SEM test.The
third phase was carried out by pretest, testing of two mixed compositions,
mixtures of composite asphalt with fibers (asphalt + SI) and mixture of fiber
composite and aggregate (SI + aggregate) in order to determine the fibers
treatment model on the mixture that fulfill specifications required under Marshall
parameters. Furthermore, mixture composition was designed based on
preliminary test results in use of fibers with different compaction model. The
percentage variations of fibers content were 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, and
1.2% and variation of length were 5 mm, 6 mm, 8 mm, 10 mm, 12 mm and 14
mm. The test was carried out on Marshall’s mixture with standard compaction by
2 x 75 of impact on each mixture design with optimum asphalt content of 5.9%.
The Fourth phase was mechanical properties test of asphalt mixtures on
variations in length and percentage of fibers content, the optimum percentage of

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fibers content, temperature variations with standard Marshall’s compaction by
2x75 of impact, absolute density compaction by 2 x 400 of impact and gyratory
compactors. For deformation and durability testing, the length and percentage of
the optimum fibers were used with variations of 40ºC and 60ºC temperatures and
variations of modified immersion time of 24 hours to 120 hours (for 5 days).
The test results were analyzed by several methods. Feasibility analysis and
material characteristic ware analyzed with quantitative descriptive analysis, mixed
characteristics and mechanical properties were analyzed with mathematical
model analysis based on relationship graph and SPSS program.
The result of this series of experimental test is: the highest single tensile strength
obtained at 3 weeks immersion period with 0.3 mm diameter. The tensile stress
value is σ = 130.45 N / mm2 and maximum strain of 14.24%.
While the SEM test results shown that the fibers with immersion performed
morphological changes with a rougher surface shape compared to the non-
submerged sample. Preliminary test results on mixed compositions with
composite fiber and aggregate fiber treatment models showed better mixture
characteristics by fulfilling all of Marshall’s parameters and mixed specifications
with a maximum stability value of 1390.65 kg with a density of 2,293 gr / cm2.
Meanwhile, the mixture with the asphalt fiber composite fiber treatment resulted
in a maximum stability value of 1370.49 kg with a density of 2,268 gr / cm3. The
test results by strengthening the fibers in the mixture showed tensile stress,
tensile strain and elastic modulus increased along with increasing length and
percentage of fibers up to the optimum limit of 8 mm and 0.6% and then linearly
decreased.
Fibers with immersion have a higher tensile stress value than fibers without
immersion. For the minimum fiber length of 5 mm with a percentage of 0.2%, the
value of tensile stress of fibers without immersion is σ= 17,214.52 kPa and
tensile strain of 0.01119 while the value of tensile stress of fibers with immersion
is σ = 19,29.37 kPa and tensile strain of 0.0159. For the optimum fiber length of 8
mm with a percentage of 0.6%, the value of tensile stress of fibers without
immersion is σ= 18,966.29 kPa and tensile strain of 0.01317 while the value of
tensile stress of fibers s with immersion is σ = 26,795.84 kPa and tensile strain of
0.01486. For the maximum fiber length of 14 mm with a percentage of 1,2 %, the
value of tensile stress of fibers without immersion is σ= 4817.37 kPa and tensile
strain of sebesar 0.00642 while the value of tensile stress of fibers s with
immersion is σ = 7670.06 kPa and tensile strain of 0.0679.
Meanwhile, for asphalt mixture without fibers, the value of tensile stress is 𝜎 =
17.688.25 kPa and tensile strain of 0.01126. Based on the tensile stress on the
optimum fibers length and percentage (6 mm and 0.6%), the tensile stress of the
mixture for compaction with 2 x 75 of impact increased by 35.18%. This shows
that fiber has a contribution in improving the performance of asphalt concrete
mixtures. For mixture with absolute density compaction by 2 x 400 of impact on
the use of fibers with length and the optimum percentage increased by 42.88%
with tensile stress σ = 30.976.16 Kpa and tensile strain of 0.01376. For gyratory
compactor optimum percentage increased by of 40.88% with tensile stress of
0.01394 The decrease of the strain value of the mixture by compacting 2 x 400 of

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impact due to the high density of the mixture so that the stiffness modulus of the
mixture is increased.
Overall, the mixture with fibers reinforcement has higher performance and
resistance compared to the mixture without using fibers. This is shown from the
results of durability test with modified immersion for 5 days where on the
immersion duration of 48 hours mixture with compaction 2 x 400 of impact
increased the value of residual strength index of 2.64% and for gyratory
compressor of 3.11% and then decreased to duration of 5 days immersion with
value of IKS 78.32%. for compaction 2 x 400 of impact and 79.82% with gyratory
compactor, while for the mixture without fibers, IKS value is equal to 74.39%..
The result of mixed deformation test with fiber reinforcement has higher
deformation resistance compared to non-fibers mixture with total deformation (for
40ºC temperature) is 1.09 mm with fiber, 1.19 without fiber, with dynamic stability
(DS)= 12600 trajectory/ minutes with fiber, 10500 trajectory/ minutes without
fiber. For testing at temperature of 60ºC, total deformation is 2.71 mm with fiber,
2.89 mm without fiber, and DS= 3928 trajectory/ minutes with fiber, 3706
trajectory/ minute without fiber.
Regression test results on the level of significance of independent variables: fiber
length, content percentage, temperature, compaction, and duration of immersion
can be concluded: 1). Length has negative correlation or neither effect nor
significant to increase of tensile stress, tensile strain and resilient modulus, 2)
Fiber’s content percentage has positive correlation and significant to increase of
tensile stress, tensile strain and resilient modulus, 3) All variations of temperature
have significant effect to tensile stress, tensile strain and resilient modulus and all
test groups. 4) Compaction has significant effect on tensile stress, tensile strain
and resilient modulus; 5) Duration of immersion has significant effect on residual
strength index (IKS), first durability index (IDP) second durability index (IDK).
The results of the application and field testing show that the asphalt concrete
mixture with fibers has higher deformation and tensile resistance levels than the
fibrous blends and has a correlation or similarity with the results of laboratory
testing.
The results of this study indicate that the main function of the fibers in the asphalt
mixture is as a reinforcing material that provides additional tensile strength of
combining the material elements; this can increase the amount of energy that can
be absorbed during fatigue and fracture processes in the mixture, Mahrez et al.
(2005), the fiber can stabilize the asphalt properties to prevent the increase of
pores in the mixture and increase the density, Garcia et al. (2013). fibers convert
modified asphalt viscoelastic, increase the dynamic modulus, Wu S et al, (2007),
resistance to temperature changes Putman et al (2004), creep, rutting resistance,
Chen et al. (2005), while reducing reflective asphalt cracking in the mix and the
pavement structure.
Keywords: Tensile stress, tensile strain, resilient modulus, fibers, absolute
density, gyratory compressor.

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