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.

Testing Different Coils

Last week we spend together with our partner SGS-Intron a day at the producer of the induction machine that we are using to heat and heal the asphalt. We once again found out that the mechanism of induction heating is influenced by many factors. To find the right combination of fibres in the material (length, cross section, amount, distribution) and settings of the machine (frequency, power, coil design etc) needs some insight knowledge, but also some trial and error.

We can not say that we had nothing to choose from..............



Breijn Symposium

Breijn is organising a symposium series this month about "Flexibilitiet in Levensduur"
Erik gave a presentation on Self Healing Materials yesterday. Last week Prof Sybrand van der Zwaag of Aerospace Engineering  of TU Delft was the guest speaker and next week Prof Andre de Boer from TU Twente will take the floor. More info on the symposium can be found on the Breijn-website.

Main topic of the presentation was Self Healing Concrete and Asphalt.
The Self Healing Asphalt part was dealing with the subject on this blog.
More info on the Self Healing Concrete projects can be found on http://www.selfhealingconcrete.blogspot.com/

At the end of the symposium all participants received the Self Healing Breijn-Cube. Guess what kind of material this is?.....

more results from tests

Quantao obtained in the last weeks some new interesting data from the tests.
The tests that he performed are the 4-point bending fatigue tests on beams. See one of the posts below for the set-up. What comes out of the tests is that the optimum healing temperature is 85 C. The tests are done on 'fresh' samples and samples that are artificially aged to an age of about 5 years. The healing performance and fatigue life extension ratio of the fresh and aged samples is almost equal. In the aged samples we see a slight decrease of 2%.

In the graph below the fatigue life extension ratio is plotted for tests were we only had natural healing (just rest periods) and were we had our induction healing combined with rest periods.

RTL4 news item

RTL4 news had yesterday an item on road damage on Dutch highways. Self Healing Asphalt with steelwool was proposed as a possible solution. In the video you see some shots from the project in our lab.
RTL4 is a commercial TV station, which means you first have to watch a commercial before the video starts. Sorry about that.....

Microscopy and Nano-Indentation

To measure the properties of our self healing asphalt we are doing a lot of different tests. These tests are performed on the virgin material, the aged material (after oxidation) and on the the damaged and subsequently healed material (after applying the induction healing).
We are applying also some new techniques, like microscopy on thin slices of 30 micrometer thick. See the image on the left.
Another technique we are using is nano-indentation on polished samples (image on right side). The indents are performed using a berkovich tip and a cooling stage at a temperature of -20 C with our Agilent G200 Nano Indenter.

Very Nice Self Healing Product

If you are interested in other self healing products you should have a look at the video below. This is realy incredible!. It would be nice if our asphalt would perform in a similar way......

Self Healing Concrete BLOG

We are proud to announce that we also created a BLOG for Self Healing Concrete.

If you want to find out more, have a look at:
http://www.selfhealingconcrete.blogspot.com/

Article in NRC 30/31 July

Another article discussing our project was recently published in NRC Handelsblad on July 30/31.

2nd edition of Self Healing Materials brochure

AgentschapNL published a new version of the Self Healing Materials booklet. You can download it by clicking on the image. Happy reading!



test results look promising....

Of course you are all waiting to see some results of the laboratory tests that are now being performed on the samples that we took from the road. We do not have final conclusions yet, however, tests show that the service life of the material might increase (a lot).

The results shown below are from the 4-point bending fatigue tests performed in the road engineering lab at Delft Univerity. In this set-up different type of tests are compared.






The first line in the graph at the right is for the reduction in flexural sifttness in the original fatigue test. The next line is if we repeat the fatigue test after a rest period of 18 hours. The third line is for the case if we apply heating to 70 C during the rest period. The heating realy improves the behaviour of the material

In the figure at the right it can be seen that we did do multiple loading cycles where we had rest periods including heating. The material almost recovers completely after each cycle and the total fatigue loading cycles that can be done is much much larger than the test without resting and heating.






Please don't get too exited....We should not conclude yet from this result that the service life of the road will increase in the same manner, however, it looks promissing, doesn't it?

article on project in Nederlands Dagblad

On August 4 the Nederlands Dagblad published an article in Dutch with the title
"The ideal asphalt does not exist yet" (but we are getting close....).

self healing conference ... continued

The extended abstract of the presentation can be downloaded here: Schlangen_Extended_Abstract_BATH

and the powerpoint slides of the presentation can be found here: Schlangen_Presentation_Bath

Self Healing Conference Bath

End of June we had a very interesting conference in Bath UK about self healing materials.
A lot of new research was presented and many good ideas for furthure work were proposed.
Below you see all the participants:

Erik presented the work on the self healing road. It turned out that this was one of the first real application (and maybe the only one...) of a civil engineering self healing material.

laboratory testing

More and more lab-tests are being started these days.
The samples are ageing, the induction machine is being optimized, Cantabro tests are running to measure particle loss and 4 point-bending fatigue tests are started as can be seen in the photo below.

Last day Alvaro at TU Delft

After 3 years working with great succes as a post-doc on the project Alvaro Garcia gave yesterday his final Seminar on the subject during the monthly Microlab-Colloquium. Now Alvaro will go for 1 month back to Spain. Not to rest after the hard work, but to walk for about 1000 km in Santiago de Compostela. After that he will continue his career at EMPA in Switzerland working on similar topics like material optimization and self healing of asphalt and concrete. We wish him all the best overthere, but we are sure we will stay in contact and will continue to have many discussion on our steelwool fibre asphalt.

RSAT plates under induction machine

The first RSAT plates from the road are tested this week at Brein (Heijmans) in Rosmalen and transfered to Delft to heat them with induction energy. In the picture below you see the laboratory setup for the heating with the induction machine and the infrared camera for measuring the temperature in the sample. In the small picture you see a screenshot of the computer showing the temerature in the sample. Next week we will do similar tests at SGS-Intron with the bigger version of the induction machine that will be used for the road.

Many applications of new asphalt

The new asphalt contains steelwool fibres. Magnets will stick to it. You can start thinking of many more applications. It can for instance hold buisiness cards or family pictures on your desk .....

Self Healing Asphalt in Technisch Weekblad

The 'Technisch Weekblad' published an article (in Dutch) on the self healing asphalt. Click on the image to read the article.

Asphalt core under induction machine

The image below shows an asphalt core (left) and the same core heated under the induction machine (right). The right photo is taken with our infrared camera. It can be clearly seen that the induction heating primarily heats up the bitumen (with the steel wool fibers) and not the aggregates. In the infrared image the aggregates are darker, which means the temperature is lower.

Core Drilling

Today the road was inspected and 120 cores have been drilled from the road. The road survived the cold days with ice and snow perfectly. No damage or even small cracks could be observed.








The cores will be tested in our lab. We will perform mechanical tests to measure the indirect tensile strength. The cores will be scanned in our CT-scanners to measure the fibre distribution. Part of the cores will be aged in the weather-o-meter and we will apply induction heating to the samples to test how fast heating is possible.


The results of the tests will be put on this blog when available,

Front cover of DCMat newsletter

The newsletter of the Delft Centre for Materials DCMat has also an article on our asphalt this month.


This is the link to the newsletter.

TU DELTA article on self healing highway

The weekly newspaper DELTA of Delft University published an article today on the self healing highway. Click here to read the article.

Asphalt core heated with induction energy

At the right you can see an asphalt core with steelwool fibers that is heated op to 120 oC under the induction machine in the laboratory. The image is taken with our infrared camera.

The team added

There is a new page added to the blog on which the people are introduced that are responsible for the development of this self healing asphalt.

Brochure on Self Healing Asphalt

Rijkswaterstaat (Dutch Government) published a brochure on self healing asphalt and roads. Our self healing asphalt with steelwool fibers is described in this report as one of the very good options. Another project we are working on now (also sposored by AgentschapNL) is the use of capsules filled with rejuvenator inside the bitumen. This project is also described in the brochure. You can download it here. The brochure is both in Dutch and in English. Happy reading.

Happy 2011

Fireworks on the asphalt.