There is lot of research going on for harmonization of procedures for preparation of BSMs specimens. Few European countries use slotted mold for the preparation of BSM specimens. Won't the water ooze out from the slots carrying fine particles during compaction, which may result in variation of densities?
In the case of bitumen emulsion-based (stabilised) materials compaction has arole to increase the mixture density and to initiate emulsion breaking by applying pressure on emulsion film. In this regards, selection of a suitable compaction method should be based on their suitability to fulfil these two roles.
The most commonly applied methods for laboratory compaction of these mixtures in Europe are gyratory and static compaction. There are few other methods like Marshall and roller compactor. On one hand, the Marshall compaction is practically useful but, because of applying an impact load, is not is not the best solution for mechanical triggering of the emulsion breaking. On the other hand, roller compaction is still subject to research (e.g. see my dissertation) when it is about these materials. You can find some additional relevant articles in the list.
As you mentioned all the devices must be adjusted to enable an appropriate drainage of the extruded water. A filter paper is usually inserted between the specimen and the openings and the drained water mostly clear. Assuming the mixture is well designed, there will be no loss of fine particles because they should be well coated during mixing and bound by the remaining bituminous binder during the drainage. However, the fine particles do react with the aqueous phase and various effect can be observed. Please, refer to the listed articles for more details.
For any further issues, please do not hesitate to ask.
Article Characterization of the reactivity of road aggregates with r...
Article Evaluation of the compactability of bituminous emulsion mixe...
Article Effect of compaction energy on physical and mechanical perfo...
Thesis Influence of bitumen emulsion and reclaimed asphalt on mecha...
Dear Miomir,
Thank you for your response and reading materials. The explanation was crisp and clear.
Although most European countries use static and gyratory compaction for BSMs, many studies have reported that static compaction provides too high density compared to that obtained in field, while gyratory compactor is still new for larger part of the world. It is has been shown that Proctor compaction is most suitable for determination of OMC in BSMs. Can further steps of determination of optimum emulsion content and foam content be performed using Proctor compaction?
Dear Arush,
Proctor compaction is very similar to Marshall compaction, as it consists on repetitive hammer impacts. Indeed, it is not the best method for materials with emulsion, as it is not effective to drain off the emulsion water and break the emulsion.
In countries, such as Spain, we use the Proctor only in a previous stage to determine the optimum water content. In a second stage, we add different amounts of emulsion, providing that the sum of added water and emulsion water is equal to the optimum previously obtained. However, for this second stage with emulsion, static compaction is used and mechanical tests are carried out. Nowadays, it is getting more and more common the use of gyratory compaction, as it seems to simulate better the field conditions.
I invite you to read our publications on this topic, especially the attached one, where we propose a new methodology for the study of BSMs.
For further information do not hesitate to contact me.
Regards
Article A proposed methodology for the global study of the mechanica...
Proctor compaction is an impact compaction as Breixo said and is a very unsuitable for emulsion-based mixtures. Although Marshall compaction is unsuitable, too, if I would have to choose between these two, I would choose Marshall. For your information, there is one modification of the Proctor compactor made by Wirtgen (see the provided link), which is originally aimed to be used for mixtures with foamed bitumen.
Your comment about the deviation of the static compaction energy in some countries' procedures form the results obtained on-site is absolutely justified. However, there are different ways the static compaction can be applied (stepwise, continuous, etc.). The good thing is that equipment for static compaction is widely available and the static compaction promotes emulsion breaking. Above all, you can easily adjust the procedure. For more details, you can see my article on the effect of compaction energy (see the link below).
https://www.wirtgen.de/en/products/cold-recyclers-soil-stabilizers/ancillary-equipment/wlb10s.php
Article Effect of compaction energy on physical and mechanical perfo...
Thank you Miomir Miljković for sharing this valuable data.
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