Productization of a recovered material often require a full scale laboratory and field study. Low volume roads and other lightly loaded pavement structures such as pedestrian and bicycle ways offer a inexpensive platform to research and test the performance of the recovered material in actual climate and ground conditions. Different kinds of pavement structures has been built on different pilot projects around Finland. A Common factor for the recovered materials that have been used in the projects is the material regional availability.
The city of Tampere is developing its construction material usage towards to the principles of circular economy. The use of industrial by-products and recovered materials in road construction will support the foregoing target.
In this study with the city of Tampere, locally available industrial by-products and recovered materials are used to design the pavement structures of paved pedestrian and bicycle ways. The aim for the study is to optimize several individual parameters in of the structures. Key factors observed during this study are cost-effectiveness, technical performance, environmental impacts and practicality of the construction process.
Local recovered materials that are used in the design are recovered municipal solid waste incineration bottom ash (MSWI BA), bottom ash, biomass fly-ash (BFA) and granulated fly-ash. Technical and environmental properties of the materials are studied in a preliminary laboratory tests. Local boundary conditions for the design process are frost susceptible soil and low bearing capacity of the subgrade. The effects of these damaging conditions are prevented by designing different pavement structure types with the use of the multifunctional technical properties of the recovered materials.
This study includes two full scale pilot projects where the different experimental pavement structures are built. Pilot-projects include a diverse follow-up research of the technical performance and environmental impact of the experimental structures. Manual follow-up research is used to monitor the pavement deterioration and collect material samples of the structures by test drilling. Automatic data acquisition equipment is used to collect continuous information of the temperature gradient on each structure. The optimal methods of construction and material handling for each structure are studied during the construction period together with the construction services of the city of Tampere.
Suitability of each experimental pavement structure type is evaluated in the final stage of the project by analyzing the follow-up research data and calculating the construction costs of each structure. The city of Tampere is developing a digital database where different kind of spatial data e.g. well logs, groundwater basins is stored. In the future city planners can use this data and guide the recovered material usage in different areas on the streets of Tampere.
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