Suitability of recycled construction and demolition aggregates as alternative pipe backfilling materials

• Physical properties of recycled construction materials were assessed.
• The compaction characteristics were found to be within the requirements.
• Total concentration and leachate values satisfied the allowable limits.
• The requirements for pipe backfilling and sub-base applications were compared.
• Recycled construction materials are suitable for pipe backfilling applications.

This research was undertaken to investigate the suitability of recycled construction and demolition materials as alternative pipe backfilling materials for stormwater and sewer pipes. Three commonly found recycled construction and demolition waste materials, (crushed brick, recycled concrete aggregate and reclaimed asphalt pavement) were investigated to assess their suitability as a pipe backfilling material. The physical, geotechnical and chemical properties of these construction and demolition materials were compared with local engineering and water authorities specifications for typical quarried materials so as to assess their performance as a viable substitute for virgin quarried aggregates in pipe backfilling applications. Physical and geotechnical characterisation tests such as particle size distribution, specific gravity, water absorption, Los Angeles abrasion, California Bearing Ratio and modified Proctor compaction tests were undertaken. Chemical properties were also determined, including organic content, pH, trace element or total concentration and leachate testing of the construction and demolition materials for a range of contaminant constituents. In terms of physical, geotechnical and chemical assessment for pipe backfilling applications, recycled concrete aggregate and crushed brick were found to have the properties recommended by environmental protection authorities while reclaimed asphalt pavement material did not meet some of the specified requirements. Also shear strength properties were found to be equivalent or superior to those of typical quarry backfilling materials. This research indicates that traditional considered waste materials can be reused viably as alternate pipe backfilling materials.