Effects of rh-wma additive on the rheological properties of reclaimed asphalt binders and the engineering properties of recycled mixtures / Lillian @ Lilia Gungat
Penggunaan asfalt kitar semula (RAP) merupakan satu pilihan sebagai turapan mapan
disebabkan oleh kelebihannya dari segi ekonomi dan alam sekitar. Walau
bagaimanapun, penggunaan asfalt kitar semula dalam kuantiti yang tinggi memerlukan
suhu penghasilan yang tinggi dan akan mengakibatkan peningkatan penggunaan
tenaga dan masalah alam sekitar semasa penghasilan campuran asfalt. Suhu yang
tinggi diperlukan semasa penghasilan dan pemadatan campuran asfalt kerana pengikat
asfalt kitar semula telah teroksida dan menjadi kukuh. Campuran asfalt dengan
kekukuhan yang tinggi lebih terdedah kepada kegagalan lesu. Ini menerangkan alasan
kenapa penggunaan asfalt kitar semula terhad terutamanya di kawasan yang
mempunyai sumber agregat yang banyak. Kajian ini mengkaji prestasi satu bahan
tambah campuran asfalt suam (WMA) yang agak baru yang dinamakan sebagai RH
WMA, bagi menurunkan suhu penghasilan asfalt. Kandungan optimum RH-WMA
telah ditentukan melalui ujian-ujian reologi bahan pengikat asfalt. Sebanyak 3% RH
WMA daripada berat bahan pengikat telah ditambahkan ke dalam bahan pengikat dan
campuran asfalt kitar semula. Kesan RH-WMA ke atas bahan pengikat dan campuran
kitar semula telah dikaji melalui sifat kimia, sifat reologi dan ujian prestasi campuran
asfalt. Keputusan ujian menunjukkan bahawa penambahan RH-WMA telah
menurunkan kelikatan bahan pengikat pada suhu tinggi dan memperbaiki rintangan
terhadap kelesuan pada suhu sederhana. Penurunan kelikatan juga diperhatikan apabila
RH-WMA ditambahkan kepada bahan pengikat asfalt kitar semula dan ini mempamerkan
potensi untuk mengurangkan suhu penghasilan campuran asfalt kitar semula. Keputusan
ujian Fourier Transform Infrared (FTIR) menunjukkan kebolehan RH-WMA untuk
mengurangkan kesan penuaan. Pengurangan kesan penuaan juga dilihat dalam lengkung
utama reologi pada frekuensi tinggi atau suhu rendah. Berdasarkan lengkung utama,
penambahan RH-WMA menunjukkan bentuk lengkung yang sama dengan bahan pengikat
kawalan tetapi menunjukkan peningkatan modulus kompleks dan penurunan sudut fasa. Perbandingan dengan bahan pengikat kawalan menunjukkan bahawa pengikat asfalt kitar
semula yang dicampurkan dengan RHWMA berpotensi untuk meningkatkan rintangan
terhadap aluran. Keputusan kandungan bahan pengikat yang optimum (OBC) berdasarkan
kaedah tindak balas permukaan (RSM) dan mengoptimumkan pelbagai kriteria dalam
penghasilan campuran asfalt kitar semula bersama RH-WMA (RAM-WMA) menunjukkan
bahawa suhu campuran memberikan kesan signifikan ke atas kandungan bahan pengikat
yang optimum. Prestasi campuran asfalt kitar semula bertambah baik dari segi kekukuhan
dan rintangan terhadap aluran. Walau bagaimanapun, kebolehan campuran asfalt
untuk merintangi kelesuan berkurang dengan ketara apabila asfalt kitar semula dengan
kekukuhan yang tinggi dari lokasi R1 dan R3 dicampurkan bersama dengan campuran
asli. Namun, penambahan RH-WMA telah memperbaiki rintangan kelesuan dalam
campuran asfalt. Kesan kombinasi kelembapan dan penuaan ke atas campuran asfalt
telah mengurangkan rintangan kelesuan dalam semua jenis campuran asfalt berbanding
dengan spesimen tanpa dikenakan lembapan. Secara umumnya, penambahan RH-WMA
berpotensi mengimbangkan kesan buruk kekukuhan dalam asfalt kitar semula dan
seterusnya memaksimumkan kebaikan penggunaan asfalt kitar semula. __________________________________________________________________________________
Reclaimed asphalt pavement (RAP) utilization is an option as a sustainable pavement
due to its economic and environmental benefits. However, the use of high RAP content
in pavement construction implicates high production temperature and hence increasing
energy consumption and environmental problems during the asphalt mixture
production. Higher asphalt mixture production and compaction temperatures are
needed because the RAP binder is oxidized and stiffened. Asphalt mixtures with very
high stiffness are more susceptible to fatigue failure. This explains the reason why
RAP usage is limited particularly in areas with high amount of aggregates resources.
Therefore, this research investigates the performance of a relatively new warm mix
asphalt (WMA) additive named RH-WMA additive to reduce asphalt production
temperatures. The optimum RH-WMA content was determined through asphalt binder
rheological tests. A total of 3% RH-WMA additive by mass of asphalt binder, was
incorporated into the recycled asphalt binder and mixture. The effects of RH-WMA
additive on recycled asphalt binder and mixture were investigated via chemical
properties, rheological properties and mixtures performance test, respectively. The test
results showed that the incorporation of RH-WMA additive with asphalt binder
decreased the viscosity at high temperature and improved fatigue resistance at
intermediate temperature. Viscosity reduction was also observed when RH-WMA
additive incorporated with recycled asphalt binder and hence indicated the potential to
reduce the production temperature of the RAP mixture. The Fourier Transform
Infrared (FTIR) test result showed the ability of RH-WMA additive to reduce the
effects of aging. The reduced effects on aging is also shown in the rheological master
curves at high frequency and/or low temperature. From the rheological master curves,
the addition of RH-WMA additive increased the complex modulus and reduced the
phase angle values compared to the control sample. This observation showed that the
recycled asphalt binder incorporated with RH-WMA additive showed potential
improvement in rutting resistance. The optimum binder content (OBC) results based
on response surface method (RSM) and multi criteria optimization in recycled asphalt
mixture with RH-WMA additive production indicated the significant effects of mixing
temperature on the OBC. The performance of recycled asphalt mixtures were
improved in terms of stiffness and resistance to rutting. However, the asphalt mixture’s
ability to resist fatigue decreased considerably when stiffer RAP from locations R1
and R3 were incorporated in the virgin mixture. The incorporation of RH-WMA
additive improved the mixture’s resistance to fatigue. The combined effects of
moisture and aging also decreased the fatigue resistance of all mixture types in
comparison with unconditioned specimen. In general, the addition of RH-WMA
additive can potentially balance the adverse effects of RAP stiffness and hence
maximize the benefits of RAP usage.
Effects of rh-wma additive on the rheological properties of reclaimed asphalt binders and the engineering properties of recycled mixtures / Lillian @ Lilia Gungat
Effects of rh-wma additive on the rheological properties of reclaimed asphalt binders and the engineering properties of recycled mixtures_Lillian @ Lilia Gungat_A9_2017_MYMY