Kijk het webinar OESA terug

Op maandag 27 mei organiseerden we samen met Rijkswaterstaat en het Ministerie van Transport in China een webinar over OESA: Open Emulsion Sand Asphalt. Je kunt het webinar hier terugkijken. Onderaan deze pagina staan de vragen en antwoorden die voor een gedeelte tijdens het webinar zijn beantwoord en voor een deel na het webinar zijn binnengekomen. Omdat het webinar in het Engels werd gegeven zijn ook de vragen en antwoorden in het Engels. 


Inge van VilsterenInge van Vilsteren: she is the coordinator of the action plan in the MoU concerning exchange of knowledge about Innovation in Road Maintenance. She will give a short introduction to this subject. 







Koen BrounsKoen Brouns, director of PaveCare. PaveCare is a company, specialized in life time extended maintenance in infrastructure 


Vragen en antwoorden

Is this material already available on the dutch market for all regular roadcontractors?

The development started in 2001, with one contracter. Beginning of 2004 a second one developed OESA for the Dutch market. Nowadays four contractors made the effort to follow a validation traject and proof their product. Every contractor could do so. The material is widely available.

What kind of test methods do you use to eveluate the mechanical properties of GGMS in your lab.

There are no functional specifications for the contractor for this product on the road. Al specifications are on the mix. The only functional test that is demanded is the skid-resistance. This we demand for every new toplayer on our highways.

After how many years do you applie the GGMS normaly?

Our laser crack measuring system ‘tells’ us when the first stoneloss has started. On average this is at about 8 years on the heavy lane.  

Is the GGMS effective for rutfilling (spoorforming). Max thickness in your experience?

Ruts can’t be deeper than 5 mm, because the biggest “stone” is 3 mm. When apply it thicker, you will have friction-problems. When you have a problem with rutting in PA, there’s probably a issue with the layer beneeth the PA

This GGMS is an open mix especially developed for the Porous Asphalt layer. If rutting occurs in the Porous Asphalt than most often something else is the cause of this.  Most situations we see that the binder layer is causing this rutting.

Is there a special design for the gradation or material content which make it porous?

You can find this information on the attached datacheet.

Can you apply the GGMS on any stage of rafeling damage?

Well… you could, but you should better not. It is best to use this GGMS at the start of stone loss. To put it simple just one layer of stones should be missing. If stoneloss is already developing towards holes in the toplayer, the GGMS probably will not keep this together and degradation will go on.

What kind of rubber do you use in the GGMS?  truck tyre rubber or car rubber? How to mix the crumb rubber into the GGMS?

There is no rubber used in GGMS

How do you check the bonding strength of GGMS to the old porous asphalt surface?

In first, when developing this mix, we did all kinds of tests. Some of these tests we made up ourselfs, because no standard test was available for this specific product. But we have seen that the bonding of the GGMS is not a problem. The GGMS has very good adhesion to the PA. The quality of the PA is the determining factor.

Can you put the GGMS twice or only once?

Yes that’s possible, however the drainage will be less.

How long in general does it last?

Our goal is to extend the lifetime of the Porous Asphalt with 3 till 5 years. The application starts at the expectancy of end of lifetime of approximately 3 years.

When you want to remove it, how to?

All used materials are in line with all other asphalt products. At end of lifetime we mill out the total porous asphalt layer (~50 mm) including the GGMS. All milled material will be delivered to the asphalt production plants, allowing them to reuse recycled milled material for the production of new asphalt.

And how to ensure the underneath layer's air voids not destroyed by the removal action?

We mill out the complete top layer. The binder layer underneath is a dense asphalt concrete. We do not take out just the GGMS layer.

From our own experience we see that milling out just a bit of the total layer (by example half of the 50 mm PA; 25 mm milling) is not a problem. We do this in the Netherlands at specific locations and then apply a thin PA 8 layer. After milling we use a cleaner truck with water pressure and vacuum cleaner.

Do you use a modified binder in the emulsion?

The emulsion is modified with latex

Can you use GGMS to solve roughness problems?

In general; no. As seen in the beginning of the presentation, the GGMS fills out al the missing stones. The surface of the toplayer now will consist of the original stones of the PA and locally the GGMS. The tires use mostly the roughness of the minerals. If the skidresistance of the PA is not at the right level, it still is not after applying the Gap Graded Micro Surfacing.

Only shortly after applying the GGMS is on top of the PA and in this stage the skid resistance is very high.

What is the max aggr size in your PA for which you apply this procedure?

In the Netherlands we use a PA16 (and a 70/100 normal penetration bitumen).  We do have road sections with two-layered PA. In that situation the top-layer is a PA8 (and a few sections now have PA5 as a toplayer).

What makes OESA better than a conventional seal?

GGMS has drainage capability, normall doesn’t have that. Being gap grated makes it possible to be applied thin, and this meet the friction demands.

When you apply OESA to porous asphalt, what do you mean by “porous asphalt”? Do you mean the single-layer type with 16 mm max aggr size only, which gives just a small noise reduction, or do you apply OESA also on the much more noise-reducing twinlay version with 8 or 6 mm max aggregate size?

In the Netherlands we use a PA16 (and a 70/100 normal penetration bitumen).  We do have road sections with two-layered PA. In that situation the top-layer is a PA8 (and a few sections now have PA5 as a toplayer).

With OESA applied, what do you mean by >25 % voids content? Is that the voids only in the OESA or the total of voids in the OESA plus the PA on which it is applied?

This is the voidcontent of the GGMS indeed. There is not a good test-system to measure the voidcontent of the total of voids in the OESA plus the PA on which it is applied. This is not needed either; in the development of this product we had focus on water drainage and noise effects.

When OESA has been applied do you think that there is any access to voids in the PA under it?

In our experience there is. Of course it depends on the quality of the porous asphalt layer itself. If , due time, the waterdrainage of this layer has become very pour, this will have its effect on the drainage after applying the GGMS. The cleaning of the PA with high pressure and vacuum cleaning will help a bit.

Datacheet Pavecare ZOAB