The recovery of residual granular materials during road repair work

Definition

Every year in Quebec, road repair projects generate significant quantities of residual granular materials. These residual granular materials are mainly crushed stone, concrete and residual bituminous coating.

The Guide d’application du RVMR (2023) defines what crushed stone, concrete and residual bituminous coating consist of. The definitions of residual concrete and bituminous coating are intuitive, however, that of crushed stone is less so. Residual crushed stone generated during demolition work on civil engineering works is defined as a natural granular material having undergone screening and/or crushing during its manufacture, and which is present in a distinct horizon.

Valorization of residual granular materials

The valorization of residual granular materials is firstly governed by the Regulation respecting the regulatory scheme applying to activities on the basis of their environmental impact. This defines the conditions under which the recovery of residual materials is exempt from ministerial authorization. The Regulation respecting the reclamation of residual materials then defines the standards to be respected (nature, composition and levels of contaminants for example) in this latter situation and the possibilities of recovery following a categorization of residual granular materials.

The advantages of recovering residual granular materials

The main advantage of valorizing residual granular materials is cost reduction. For example, it is common to find C10 to C50 petroleum hydrocarbon contents between 700 and 3500 ppm in the foundation of a road following an environmental characterization. Such a content may be due to previous spraying of dust suppressants. In the past, residual crushed stone was more often than not used as soil, and such a C10 to C50 HP content meant that it could only be used on the site of origin (soil in range B-C of the du Guide – Soil Protection and Contaminated Sites Rehabilitation of the MELCCFP). Other avenues of recovery existed (technical landfill, visual, noise or security screens for example), but had several limitations (volumes that could be recovered and real opportunities for recovery, for example). A residual crushed stone that has a content between 700 and 3500 ppm in HP C10 to C50 can be a category 3 of the RVMR (if the other required parameters also categorize it) and it can be valorized off-site in numerous ways, including foundation material, sub-foundation or road embankment.

Landfill: Other alternatives

The alternative to recovery is landfilling and the cost per ton can reach up to $200/ton. This high cost and the quantities of residual granular materials generated on site can ultimately represent a significant sum which could otherwise have been invested in more “interesting” aspects of the renovation project.

Avizo, partner of choice

Avizo is capable of characterizing the residual granular materials in view of the valorization according to the RVMR, before or during your project. A characterization of residual granular materials can be carried out alone or integrated into the environmental site assessment process, phases I and II as required in the context of certain projects requiring ministerial authorization, since the Guide de caractérisation des terrains du MELCCFP considers aggregates as one of the mediums that must be evaluated during the process.