Putting recycled concrete into practice in Belgium: From case studies over chain management to standards and quality assurance

Although there has been extensive research and several demonstration projects in Belgium and abroad, the use of recycled aggregates in concrete is still limited in practice. Several barriers were identified: lack of practical experience, limiting standards and the need for specific quality assurance. The paper describes recent developments in Belgium, with focus on practical experiences and support of the professionals on the one hand, and development of standards and quality assurance schemes on the other. Practical experience is gained through 10 pilot projects using recycled aggregates in structural concrete for roads & buildings. The results show concrete with recycled aggregates on an industrial scale can fulfill all technical requirements. However, specific attention points are to be taken into account, as well in the design phase (applications, ambition levels), the preparation phase (quality of aggregates, ITT of concrete) as in the execution phase (finishing, curing …). A step-by-step procedure to guide the process has been elaborated. Complimentary, research has been executed to reinforce the recycling chain, and to directly link the demolition of a building to the crushing and the quality of the recycled aggregate for use in concrete, in order to obtain a so called ‘short & strong chain’ in order improve confidence & to divide costs & benefits over the actors. A second development is the specific Belgian standardisation and certification framework, based on the European standard EN 206. Specific aspects of the Belgian approach are the implementation of the ‘specificity of use’-principle, application of correction and safety factors on the calculation of the effective water-to-cement-ratio and the required quality of the recycled aggregates. To support the development of the standard, research is being executed in several Belgian laboratories. Results on aggregate quality (10 sources) and concrete performance (20%, 30%, 50% replacement) show the feasibility and the limits. Finally, a specific certification scheme for concrete with recycled aggregates is being developed. This procedure addresses requirements on the high-quality aggregates, specific initial type testing and factory production control schemes, practical implications on the concrete production plant (storage of aggregates, mixing procedure …). The combination of the different developments will lead to the increased and responsible use of recycled aggregates in structural concrete in Belgium.