Template for samaris documents

3.6The opinion of the WP3 group on environmental impact evaluation

Based on the review of existing information on environmental impact evaluation of the use of alternative materials for road construction, the WP3 group has drawn a number of conclusions and expresses a number of recommendations:

It is generally recognised that one of the most important environmental risks associated with the use of alternative materials for road construction purposes during the lifetime of the construction project is the potential leaching and subsequent migration of contaminants from the alternative material into the environment. Since both the general acceptance of alternative materials for road construction and regulatory concerns focus on these issues, the WP3 group will focus future work within SAMARIS on the development or adoption of concepts and methods aimed at evaluating the impact of components leached from various parts of a road construction scenario on groundwater and surface water.

It is the opinion of the WP3 group that proper results can only be achieved if appropriate tools are used to test the leaching properties of the materials to be used in road construction. The test methods must be chosen and the results interpreted in accordance with the water flow regime and the mechanism controlling contaminant release in the chosen scenario. Wrong choices of leaching tests and wrong interpretation of results may lead to meaningless evaluations and may potentially cause unintended harm to the environment (or discard materials on a wrong basis). The WP3 group will provide guidance and recommendations concerning choice of test methods, interpretation of results and performance of environmental impact evaluations for various road construction scenarios involving the use of alternative materials.

It is the opinion of WP3 that all of the leaching test methods necessary for this purpose (with the possible exception of methods for leaching of organics) are available or under development as CEN methods (TC 292) or available as national standards. In fact, only a few methods are necessary.

It is the opinion of the WP3 group that the methodology developed and applied in connection with the setting of the limit values at European level for acceptance of waste for landfilling in accordance with the European Landfill Directive may be applicable to the evaluation of the impact of contaminants leached from road construction materials on the environment. The WP3 group will therefore use this methodology as the basis for further work and adjust it to fit the chosen road scenarios and the relevant impact scenarios.

It is the opinion of the WG3 group that the current developments at European level, in particular in relation to the Construction Products Directive, underscore the need for the kind of guidance and methodology development that the WP3 (as well as WP4 elsewhere in Samaris) group aims to provide.

4.Synthesis and COOPERATION

4.1Recycling and cleaner technology today and in the future

Traditionally, natural raw materials are used for road construction. However – due to political intentions to reduce the use of or in some regions even lack of natural raw materials and the problem of depositing alternative materials (e.g. building, road demolition and industrial waste materials) - environmental thinking is focusing on reuse of alternative materials.

The problem as identified and described in e.g. the European ALT-MAT project, ALT-MAT (2001), is that traditional product specifications (according to level 5 in the technical pyramid in Figure 2.3 and in section 2.2.2) are often directly applied to alternative materials, resulting in the fact that these are often disqualified in relation to natural materials.

Instead, the use of alternative materials should be considered based on the higher levels 2, 3 or 4 in the same technical pyramid, meaning focus on the functional behaviour in the road pavement.

Thus traditional thinking, from the point of view of tendering and materials often blocks for the use of new technologies and new materials in the road sector. This blocking situation is reinforced by the apparent lack of relevant tools for the assessment of materials’ properties. Now, a better mastering of these materials implies sometime to get out of the traditional division between road techniques (bound materials/unbound materials ) and sciences (physics/chemistry) to take advantage of solutions which are ready for use.

Cleaner technology challenges ways of dealing with leaching problems from roads, often disfavouring the use of alternative materials. The challenge is to limit or isolate the leaching.

Above, the question has been raised regarding the reuse of tyre and it is important that WP3 group considers whether there is a relevant assessment approach and test for this material. Tyres are not in the list, but it is worth considering. Does WP3 group have a way to compare MSWI bottom ash to tyres for a given application? The question is a bit provocative but it shows the limits of our concepts and approaches today. Generalisation efforts in the development of assessment methodologies are still necessary to progress.

4.2Mechanical and engineering properties

Existing frameworks for assessment of alternative materials

Several very relevant papers in the fields of assessment of alternative materials have been found in the last seven years period, nine from Europe, seven from USA and one from OECD.

The WP 3 group has identified some interesting methodologies from the reviewed reports, and the group will primarily use the following two key reports for further work:

• 
  - COST 337 (2002); Unbound Granular Materials for Road Pavements; Draft Final Report
  
• 
  - FHWA-RD-00-140 (2001); Framework for Evaluating Use of Recycled Materials in the Highway Environment
  

The present technical requirement pyramid from COST 337 gives a general overview. Level 2 to 5 seems to be of interest as a starting point for the development of general methodology for assessment of alternative materials which is the work for the WP3.

When looking for pre-existing frameworks the group agreed that the most pragmatic one is the framework proposed by the FHWA (RD-00-140). The group’s proposal is to start by an assessment of the procedures and tests proposed in this framework (and of their European equivalents) for the nine materials the group has already chosen for further work. The reliability of the tests proposed in the framework for these materials will be analysed for each application of the typical road structure that has been defined on the basis of typology used in the two previous approaches (COST 337 and FHWA-RD-00-140).

The user guidelines in the report FHWA-PL-00-025 (2001) gives a good overview of several alternative materials. In complement to information collected earlier in Deliverable 4 on the nine materials at stack in WP3, in order to provide a clear description of these materials, the group will provide information related to there usual qualities and drawbacks for road use.
Other important recommendations and problems to be solved for alternative material use

There are common agreements about some of the recommendations from the reports, but the group needs to discuss to which level the recommendation can be incorporated in the SAMARIS’ proposal for general methodology for assessment of alternative materials. The tendency will be, as far as they will be judged relevant by the group, first to take advantage of pre-existing test methods, and second, if no test method seems relevant for a property to be assessed, to make a proposal for the principles a test to develop should follow.

It is important to take into account that alternative materials in many cases (either considering mechanical field or laboratory performance tests) behave differently from conventional materials. As much as possible, design and requirements should be based on performance-related tests.

There is a need for new or modified test methods for alternative materials. For some alternative material there is a gap between their behaviour in the field and what could be deduced from conventional tests in the laboratory. Examples of properties and corresponding tests that are not suitable for several alternative materials include permeability, compressibility, bearing capacity and shear strength, as described in the FHWA report. This supports the findings on the European level.

Climate effect needs to be taken into an assessment methodology framework. The assessment of climatic conditions in the cases where alternative materials are used as unbound aggregate is more or less the same as the assessment for the use of natural materials in road construction. However, in some regions freeze/thaw test and assessment are interesting; in other region this does not apply.

Moisture content variation and water movements are important factors for alternative materials as well as for natural materials. The SAMARIS group will stay in touch with COST 351 - with the main goal to study o water flow and moisture variations in pavements.