Dynamic compaction of crushed concrete fill, full-scale test at Jätkäsaari, Helsinki

Abstract

Concrete waste in the form of crushed concrete can be utilized in street and road structures. Today, a significant amount of concrete waste generated by various demolition and other activities is not fully utilized in infrastructure projects within Helsinki; as a result, a portion of concrete waste generated in the city is be transported to other sites outside the Helsinki metropolitan area. In Helsinki, large-scale land reclamation projects have been implemented, and this trend will continue in the near future. Utilization of concrete waste as fill material in land reclamation projects will reduce the need to transport concrete waste outside the Helsinki metropolitan area, with a concurrent reduction in need to transport blasted rock to the land reclamation sites. This will promote reuse and recycling of waste and will reduce heavy traffic and CO2 emissions. Crushed concrete has not been previously tested in Finland as a fill material in land reclamation projects subjected to deep compaction methods. In 2018-2019 suitability of crushed concrete for land reclamation purposes was tested in a full-scale dynamic compaction test. The objective of the test was to assess the degree of compaction produced by dynamic compaction, determine the compression rate of compacted layers under pre-loading embankment, and measure environmental impacts of the fill material. The pilot structure was implemented in Tritoninpuisto (Triton Park) located in the southern part of Jatkasaari. Crushed concrete with varying grain size was compacted using the dynamic compaction method. All materials compacted well. Results of the pilot study indicate that dynamic compaction can be applied to densify crushed concrete fill material for land reclamation. Settlement plates on the top and the bottom of the pilot structure were used to monitor short-term settlement during dynamic compaction and long-term settlement after completion of the work. Long-term settlement was minor after compaction and placement of a pre-loading embankment. Implemented study has indicated that compacted crushed concrete is a suitable material for land reclamation in street and park areas.