Self Healing Aspalt on the A58

On this Blog we will give info on the test track with Self Healing Asphalt that is built on the A58 near Vlissingen in The Netherlands. The Asphalt is a special type of ZOAB (very porous aphalt concrete) containing small steelwool fibres. A known but serious problem with ZOAB is ravelling: stones at the surface coming off in time due to microcracking in the binder. The special ZOAB that is developed at Delft University (sponsored by AgentschapNL) can be heated with induction energy due to the fibres that are present which closes the microcracks and with that extends the service life of the road.

Monday, 24 October 2011

Strength Recovery Tests

Last week Quantao performed some strength recovery tests of beams on an elastic foundation.
The set up used for these tests is given below.

The test procedure consists of breaking the notched beam on the elastic foundation, heating the fractured beam, resting the heated beam for 6 hours and finally breaking the healed beam again.

The healing index is defined as the original strength divided by the healed strength).

 

The fractured beam showing the two fracture surfaces at the location of the notch is given below.


 Next figure shows typical loading curves of original beam and healed beam (different heating temperatures)


 The strength recovery ratios are presenteed in the next figure.



The fractured beam cannot heal the crack by itself at 5°C and 20 °C: the crack is too big to be healed by natural healing. Induction heating can heal the crack and the extent of healing depends on the heating temperature. The optimal heating temperature is 85°C to obtain highest strength recovery. Further heating causes binder drainage and swelling problems, which offsets the healing benefit.
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