Abdullah, Noor Halizah
(2012)
Laboratory Simulative Clogging Behaviour And Fracture Toughness Of One And Two-Layer Porous Asphalt.
Masters thesis, Universiti Sains Malaysia.
Abstract
Clogging causes porous asphalt to lose its permeability function after a few
years in service. Therefore, two-layer porous asphalt was developed to minimize this
problem. This study presents a laboratory simulative test of clogging phenomenon
occurred on porous pavements. To ascertain the clogging of porous asphalt, one and
two-layer specimens were subjected to six clogging and cleansing cycles. The
permeability loss was assessed using a falling head water permeameter. Porous
asphalt specimens were tested incorporating conventional 60/70 and PG76 modified
bitumen at four binder contents and three different top layer thicknesses of two-layer
specimens. Selected specimens were subjected to temperature conditioning (10, 30
and 50 °C) to determine the effects of temperature to the severity of clogging. Semicircular
bending test was used to assess the fracture toughness of porous asphalt. One
and two-layer specimens were tested at 0, 10 and 20 °C testing temperatures. The
overall results showed that porous asphalt loses its permeability mainly in the first
two to three clogging and cleansing cycles. The clogging trend exhibits an
exponential pattern with addition of clogging material. The performance of porous
asphalt in resisting clogging can be ranked from the clogging and clog-recovery
index. It was also found that two-layer specimens were a better clog-resistant mix
compared to one-layer specimens while top layer thicknesses of two-layer specimen
have no significant effect on clogging. Binder type and content have significant
effects on clogging of porous asphalt. Higher temperature caused severe clogging to
the mix and lower temperature result in least clogged mix. Generally, lower testing
temperature resulted in higher fracture toughness. Subsequently, one-layer specimen exhibit higher fracture toughness compared to two-layer specimen and binder types
also exhibit significant effect on the fracture toughness of porous asphalt.
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