Project description of specific research RS-1
The general principle of the research consists in analysing the various impacts of the production of warm mix asphalt (WMA) in comparison with hot mix asphalt (HMA) production. This research will be carried out by taking into account the specificities of the Swiss market.
Note that for the terminology used in this document, warm mix asphalt (WMA) has the same meaning as Low Temperature Asphalt (LTA).
In the framework of this specific research and according to [1], it is proposed to consider following processes:
|
Category |
Processes |
|
Red flag |
WMA– Modification of the coating sequence |
|
WMA – Based on foam bitumen (foam and one-phase foaming) |
|
WMA – Based on waxes |
|
WMA – Combination of principles |
|
Reference mixture |
Reference hot mix asphalt (HMA) |
|
WMA: Warm Mix Asphalt |
Figure 1: Processes considered for RS-1
Concerning the final choice of the products (e.g. Sasobit®, Aspha-min®, WAM-Foam®,…), this choice will be performed considering the outcomes of the initial project and the other research packages needs. A proposal will be made in the first weeks of the project and this proposal will be finally submitted to the scientific committee of the project.
For this research, the various measurements will be performed during production in asphalt plant. Thus, the production in plant of the mixtures dedicated to the other specific researches will be used in order to perform the emissions measurements. The general organisation of the productions in plant will be performed by the RS-3 dealing with mix design and performance optimization. Consequently, a good collaboration and communication with this research is a must.
From a general point of view, the organization of the research consists in a first phase of an information gathering and critical analysis of the situation. Then, various aspects will be considered such as the emissions (measurements campaigns), energy consideration, costs, and the impacts on asphalt plants. These various elements will lead to the production of a best practice document that could be used by all the asphalt plant producers. Note that this document and its guidelines will be focused on the Swiss context.
Based on the various processes and products to be considered within this research, the project chart below has been developed (Figure 2). (please see pdf. page down)
1. Knowledge update
The first phase of the project concerns an update of the knowledge in the domain, especially considering the two aspects mentioned hereafter. In order to reach it, an extensive literature survey will be carried out. One can mention that some information will be also provided by the associated partner Ammann that is one of the world's leaders in that field. A critical analysis of the information gathered at both national and international levels will be also conducted.
1.1 Type of asphalt plants
The various types of asphalt plants and the associated particularities will be analysed. This analysis will be especially focused on the existing installations in Switzerland. The evolution of the type of asphalt plants and the future trends and developments will be also considered.
In order to perform a complete analysis, key contacts will be made, especially with the SMI (Schweizerische Mischgut-Industrie) at a national level. By having a close contact with SMI within this research, this will obviously facilitate the further contacts with asphalt plant owners. This process is also fully in agreement with SMI's objectives that are in particular the dissemination of new developments and knowledge in the field of bituminous mixtures.
1.2 WMA impacts on plants
In the knowledge update and literature study, the impacts of the production of warm mix asphalt on plants will be also analysed. Indeed, before to start the research, it is crucial to have a better understanding of what has been done abroad. In order to achieve this, the ongoing collaborations between LAVOC and the Laboratoire des Ponts et Chaussées (LCPC) in France will be an important support. For this part of the analysis, a focus will be put on gathering information on some of the major questions related to that research that are:
• Which part of the asphalt plant is "affected" by the production of WMA in comparison with HMA?
• What can we do in order to modify an asphalt plant? How much does it cost?
• How the production rate and the production regime of an asphalt plant is affected by the production of WMA instead of HMA?
In this part of the research, contacts will be made with SMI, but also with FOEN (Federal Office of the Environment) in order to get their impressions and current needs or projects related to that topic. At an international level, some information will be provided by Eurasphalt [12] and some other European associations.
It is important to highlight that the global effects of WMA production in asphalt plant is very much depending on the type of processes and the products used. Indeed, the production of WMA with a "simple" modified binder or the "more elaborated" production of WMA with a foaming process or double coating sequence are diametrically opposed. From a general point of view, some of the most affected aspects, depending on the LTA technology are:
• Storage of bitumen (segregation, different types, adding additives into the bitumen tank)
• Mixing process for different LTA technologies (cycle, foaming, cycle time, location of addition, ageing of bitumen during mixing)
• Remaining moisture content of mineral, influence of residual moisture in mineral
• Storage of warm mix (segregation, agglomeration/clumping, sticking, max. storage time)
2. National / International survey
After the initial phase of knowledge update, it is proposed to carry out a national and international survey based on a questionnaire.
2.1 Questionnaire to selected plants
The circulation of a questionnaire will be done, this in order to better identify the needs from the asphalt plant owners, still with a focus on the Swiss context. The contacts established with SMI in the previous phase of the research will be also used here. It is also expected to benefit from the dense international network of both Ammann and LAVOC in order to increase the number of answers and to enrich the answers with international experience.
In order to have an international perspective, it is proposed to circulate the questionnaire to companies, but also to a panel of researchers involved. This will be carried out through the FEHRL network (Forum of European National Highway Research Laboratories) that can be reached by LAVOC who is the Swiss representative in this association.
The questionnaire will take into account, at least following aspects:
• Annual production per type of asphalt and number of available recipes
• Economical aspects (costs of energy, materials, maintenance, plants,…)
• Measurements of the emissions if already done (who, how, frequency, results,…)
• Type of energy used, energy consumption (annual, per ton,…)
• Experience with WMA so far and experience of their suppliers
• Future projects related to WMA and priorities for the potential development of the asphalt plant
As explained above this survey will take into account a large number of plants by sending the questionnaire. For a selection of representative plants (3 to 5 plants), it is planned to go on-site for a more detailed discussion with the persons in charge of the installation.
3. Emissions measurements campaign
While the first part of the research is based on gathering information, the third phase is dedicated to the measurements to be performed.
3.1 Plant selection
As explained in introduction, these measurements will be made on the asphalt plant used for the production of the mixtures tested within this PLANET project. The production of the mixture is managed by the RS-3. Nevertheless, a proposal of asphalt plant will be made by the beginning of the project to the RS-3 and other partners involved in order to find the most adapted solution. Note that contacts with an asphalt plant interested to take part have already been made.
3.2 Measurements
The call for tender documents mentioned that the measurements have to be done for the reference mix and one or two of the "red flag products". In this research, it is proposed to carry out the measurements for the mixtures produced in the framework of this project i.e. reference mix and four "red flag" mixtures. Besides, in function of the asphalt plant choice, some additional measurements or data could be foreseen.
Two measurement devices are proposed for flue gas emissions:
• For CO, NOx, O2 and T (CO2 is calculated): Measurements with "Afriso-Euro-Index‚ Minilyzer’". With this measurement device, data can be logged with device's software and will then be stored and available as a text file.
• For TOC (Total Organic Compounds): Measurements with "SICK-MAIHAK Bernath-Atomic FID 3006". With this device, it is necessary to record data manually by writing down the values in intervals.
Dust measurements are not proposed in a first phase. The installation of the above mentioned devices needs about half a day in function of the asphalt plant type. The installation does not need any specific modification or adaptation of the asphalt plant. Note that most of the measurement devices to be used will be made available by Ammann and this would avoid increasing the measurement costs in a too important manner.
In order to perform reliable measurements of the emissions, it is necessary to have at least 2-3 hours production in a continuous way. Besides we would suggest, for each type of asphalt mixture considered, to perform two different measurement sessions.
We can finally mention that for these measurements some experiences, feedback and data will be provided thanks to collaboration with LCPC in France.
3.3 Data analysis and treatment
This phase consists of treating and analysing the various measurements performed. After an analysis of the quality of the various data recorded, some conclusions will be drawn for the comparison between the different types of asphalt mixtures. For the data analysis of the various components, existing knowledge in Ammann group will be used as well as LAVOC's resources, contacts and collaborations. This analysis will be also performed within a specific collaboration with RS-2 dealing with energy end environmental assessment of the asphalt mixtures.
In this phase of the research, the analysis of the compounds measured will be also considered in regards with the legislation applied in Switzerland and European Union.
The data measured will be also compared with the database about ecological impacts of materials Ecoinvent® [8] and if relevant, a proposal of contribution to the database will be made.
4. Energy considerations
Some considerations related to the energy flow during the production of warm mix asphalt in comparison with hot mix asphalt will be made. Note that this energy flow will be compared on the basis of one ton asphalt production. In order to achieve this, the data gathered throughout the questionnaires will be used. Besides, a more detailed monitoring of the asphalt plant during the production used for the PLANET research will be proposed. Some other measurement data also available will be included in this analysis.
In this analysis, a special emphasis will be put on taking into account the length of the mixing i.e. if a dedicated process needs a longer mixing time or not than a reference mixture.
5. Impacts of WMA production on plants
This part of the study will be focused on all the technical aspects related to the production of warm mix asphalt. In other words, what do we have to modify if we want to produce WMA? The technical aspects of these modifications will be considered here, while the economic aspects will be treated in the next phase of the research. This concerns for instance:
• System in order to switch between HMA and WMA production and time needed – Impacts on the production rate.
• Mixing process for different LTA technologies (cycle, foaming, cycle time, location of addition, etc.). For this part, some laboratory tests might be foreseen. For instance, this would permit to better understand what happens with the quality of the mixture at shorter mixing time. In a first phase, Marshall testing and Gyratory Compactor (PCG) would be proposed. If relevant, more sophisticated tests could also be made.
• Remaining moisture content of mineral, influence of residual moisture in mineral, drum modifications.
• System for moisture control of the aggregates (measurement and humidification?).
• Storage of warm mix (segregation, agglomeration/clumping, sticking, max. storage time).
• Storage of bitumen (segregation, different types, adding additives into the bitumen tank).
• Number of fuel tank needed in function of LTA process and connexions to the plant.
This part of the analysis is highly dependent on the type of process and mixture considered. Thus, a specific section of the final report will provide the necessary modifications in function of the asphalt plant type and WMA product selected.
One can also mention that this part is one of the key contributions of the research and is very time consuming in order to analyse in detail all the potential impacts. This can be seen in the proposed planning.
6. Cost Benefit Analysis (CBA)
Based on the various findings so far, a comprehensive methodology for a cost benefit analysis will be proposed. This aims at answering the following question: Is it profitable, from an economical point of view, to produce LTA in my plant? Indeed, this is an important question that has been partially addressed by some authors ([14], [15]).
A methodology will be proposed in function of the asphalt plant types used in Switzerland by comparing the necessary investments with the savings that can be expected. Important data for the savings will be provided by the measurements in plant that will allow estimating in particular the effect on CO2 taxation decreases. Then, some examples of CBA will be made for representative plants of the Swiss market. This CBA will also provide some key information to the other work packages, especially RS-5 dealing with the development of a multicriteria model.
7. Best practice for WMA production
One of the objectives of the present research consists in assisting Swiss plant owners in a process for the production of warm mix asphalt. Thus, it is proposed to produce a best practice (or best available technique – BAT) guideline document. This summary document will be based on the Swiss context and its particularities (size of production, number of different mixtures produced …), and the information gathered in the previous steps (3, 4, 5 and 6) will be summarized. It is especially intended to put en emphasis on:
• Recommendations for an efficient production of LTA in plants
• Proposal of a methodology for a quick and simple evaluation of the asphalt plant compatibility
• Proposal of a methodology for the follow-up of the asphalt plant from an environmental and energy point of view
• Provide a few examples
• Specific analysis related to the storage procedure of bitumen i.e. if new bitumen are necessary; method for the storage, duration,…
• Provide recommendations for an efficient use of RAP (hot and/or cold introduction)
8. Conclusions and recommendations
In the final part of the research, some conclusions and recommendations will be provided, based on the findings. In this phase, a very important emphasis will be put on the dissemination activities to the various plant owners in Switzerland. Indeed, one of the objectives is to provide some information to plant owners, this in order to provide them all the necessary information for a further production of WMA. These dissemination activities will also allow promoting bituminous mixtures with low energy and environmental impacts to the various persons working in that field.
In this chapter, it will also be analysed if, from an economical point of view, the production of WMA is viable alternative to hot mix asphalt, and under which conditions. Besides, the combination with RAP will be also discussed.
Technical contribution to the research partners
LAVOC will primarily provide technical support to research partners through its experience acquired in recent years in the domain of warm mix asphalt (mix design, material performance, environmental and energy considerations).
An important technical support is also provided through international collaborations with research institutes active in the field of WMA such as LCPC and Belgian Road Research Center (BRRC). In particular, collaborations are taking place with the LCPC on the problem of emissions measurements for warm mix asphalt (measures in asphalt plants and laboratory [11]) and the energy evaluation of WMA.
Ammann will provide technical support and large expertises in the whole domain of asphalt plants, and especially in the domain of emission and temperature measurements in asphalt plants.
