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Sains Malaysiana 41(12)(2012): 1595–1603
The
Aging Properties of HMB15 with Varying Binder Film Thicknesses
(Sifat Penuaan HMB15 dengan
Ketebalan Filem Perekat yang Berubah)
College
of Civil and Transportation Engineering, Hohai University, 1 Xikang Road, Nanjing,
Jiangsu Province 210098, China
Nur
Izzi Md. Yusoff*
Department
of Civil and Structural Engineering, Universiti Kebangsaan Malaysia
43600
Bangi, Selangor, Malaysia
Mohd. Rosli Hainin
Faculty of Civil Engineering, Universiti Teknologi Malaysia,
81310, Skudai, Johor, Malaysia
Gordon
D. Airey
NTEC,
University of Nottingham, University Park, Nottingham
NG7
2RD, United Kingdom
Received:
15 May 2012 / Accepted: 20 July
2012
ABSTRACT
In order to cope with the ever-increasing traffic loading and to
minimise the cost of road construction and maintenance, several road trials of
High Modulus Base (HMB) materials containing a 15
penetration bitumen (known as HMB15) have been carried out in
the UK since 1990s. It has been showed that, although HMB15
behaved in a similar way to conventional Dense Bitumen Macadam with a cost
saving of approximately 25%, its long-term durability (aging and moisture
damage) is still a major concern of researchers as considerable deteriorations
have been commonly observed during the ongoing investigations on cored samples
from the sites (either with or without traffic loading). The aim of this paper
was to quantitatively show the relationship between aging properties of HMB15
and its binder film thickness (binder content), so that an optimum binder
content could be determined. In order to achieve this, 5 groups of cylindrical HMB15
specimens with different binder contents (3.5%, 4%, 4.5%, 5% and 5.5%) were
fabricated and subjected to SHRP long-term oven aging test
(at 85oC for 5 days), their mechanical properties both before
and after aging simulation were tested using Indirect Tensile Stiffness Modulus
(ITSM)
tests. In addition, binders were recovered at different aging stages and their
rheological characteristics were investigated with Dynamic Shear Rheometer (DSR)
tests. Based on these, aging indices of different groups were calculated and
their mathematical relationship with binder film thicknesses was regressed. The
results show that the aging properties of HMB15
mixtures are significantly affected by their binder film thicknesses. However,
regression analysis between aging indices and binder film thicknesses indicates
that, as the binder film becomes thicker than 9.5 μm, the change of aging
indices with film thicknesses becomes minor and therefore, a film thickness of
approximately 9.5 μm was recommended for HMB15
mixtures.
Keywords: Aging; DSR; film thickness; HMB15; ITSM
ABSTRAK
In order to cope with the ever-increasing traffic loading and to
minimise the cost of road construction and maintenance, several road trials of
high modulus base (HMB) materials containing a 15
penetration grade bitumen (known as HMB15) have been carried out in
the UK since 1990s. It has been showed that, although HMB15
behaved in a similar way to conventional dense bitumen Macadam with a cost
saving of approximately 25%, its long-term durability (aging and moisture
damage) is still a major concern of researchers as considerable deteriorations
have been commonly observed during the ongoing investigations on cored samples
from the sites (either with or without traffic loading). The aim of this paper
was to quantitatively show the relationship between aging properties of HMB15
and its binder film thickness (binder content), so that an optimum binder
content could be determined. In order to achieve this, 5 groups of cylindrical HMB15
specimens with different binder contents (3.5%, 4%, 4.5%, 5% and 5.5%) were
fabricated and subjected to SHRP long-term oven aging test
(at 85oC for 5 days), their mechanical properties both
before and after aging simulation were tested using indirect tensile stiffness
modulus (ITSM) tests. In addition, binders were recovered at
different aging stages and their rheological characteristics were investigated
with dynamic shear rheometer (DSR) tests. Based on these,
aging indices of different groups were calculated and their mathematical
relationship with binder film thicknesses was regressed. The results showed
that the aging properties of HMB15 mixtures were
significantly affected by their binder film thicknesses. However, regression
analysis between aging indices and binder film thicknesses indicated that, as
the binder film becomes thicker than 9.5 μm, the change of aging indices
with film thicknesses becomes minor and therefore, a film thickness of
approximately 9.5 μm was recommended for HMB15
mixtures.
Keywords: Aging; DSR; film thickness; HMB15; ITSM
ABSTRAK
Dalam usaha untuk berdepan dengan beban trafik yang semakin
meningkat dan mengurangkan kos pembinaan jalan serta penyelenggaraan, beberapa
percubaan pembinaan jalan raya daripada bahan tapak modulus tinggi (HMB)
yang mengandungi bitumen bergred penembusan 15 (dikenali sebagai HMB15)
telah dijalankan di UK sejak tahun 1990-an. Ia telah
menunjukkan bahawa, walaupun HMB15 mempunyai ciri yang sama
dengan jalan konvensional asfalt berbitumen padat dengan penjimatan kos
kira-kira 25%, ketahanan jangka panjang (jangka hayat dan kerosakan akibat
kelembapan) masih membimbangkan penyelidik kerana kerosakan yang agak besar
telah biasa dilihat semasa siasatan dijalankan ke atas sampel yang dibuang dari
tapak kerja (dengan atau tanpa muatan lalu lintas). Tujuan
kajian ini dijalankan adalah untuk mengkaji hubungan kuantitatif antara sifat
penuaan HMB15 dan ketebalan filem pengikat (pengikat kandungan),
supaya kandungan bitumen yang optimum dapat ditentukan. Bagi mencapai
matlamat ini, lima kumpulan HMB15 spesimen silinder dengan
kandungan pengikat yang berbeza (3.5%, 4%, 4.5%, 5% dan 5.5%) telah direka dan
tertakluk kepada SHRP ujian ketuhar penuaan jangka
panjang (pada 85oC selama 5 hari), sifat-sifat
mekanik mereka sebelum dan selepas simulasi penuaan telah diuji dengan
menggunakan ujian kekukuhan tegangan tidak langsung modulus (ITSM).
Di samping itu, pengikat pulih pada peringkat usia yang berbeza dan ciri-ciri reologi mereka dikaji dengan reometer ricih dinamik
(DSR). Berdasarkan ini, penuaan indeks kumpulan-kumpulan yang
berbeza telah dikira dan hubungan matematik dengan filem pengikat ketebalan
telah mengurang. Keputusan menunjukkan bahawa sifat
penuaan HMB15 campuran ini secara ketara dipengaruhi oleh
ketebalan filem pengikat. Walau bagaimanapun, analisis regresi antara
indeks penuaan dan ketebalan filem pengikat menunjukkan bahawa, apabila filem
pengikat menjadi tebal daripada 9.5 μm, perubahan penuaan indeks dengan
ketebalan filem menjadi kecil dan dengan itu, ketebalan filem kira-kira 9.5
μm disyorkan untuk HMB15 campuran.
Kata kunci: DSR; HMB15; ITSM;
ketebalan filem; penuaan
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*Corresponding
author; email: izzi@eng.ukm.my
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