Vaihtoehtoisia maarakennusmateriaaleja sisältävien tie- ja katurakenteiden vaurioituminen

The properties of alternative earth construction materials differ significantly from conven-tional construction materials. There is not yet sufficient information about properties and long-term performance of many of the alternative materials so as to enable their smooth uti-lization. The aim of the literature review included in this study was to investigate the experi-ences obtained from typical deterioration mechanisms of road and street structures contain-ing alternative earth construction materials and to search for approaches that have been used in mechanical modelling of them. The research material used originates mainly from the Nor-dic countries, Central Europe and North America.

The first part of this report presents on a general level materials properties that affect suita-bility of alternative construction materials in road and street structures. In addition, factors affecting functionality and deterioration of road structures are presented. The main purpose of the study was to find out typical ways of utilizing various alternative construction materials in road and street structures, as well as the performance of these materials during construc-tion and thereafter. Long-term performance and causes of damages have been assessed based on the available literature. The research was focused on crushed concrete, reclaimed asphalt concrete, fly ash, municipal solid waste incineration (MSWI) bottom ash, tire shreds, tire bales and by-products from steel manufacturing. A particular attention was given to ma-terials that are self-binding or that are used together with a binging agent.

On the use of crushed concrete as an earth construction material there are long-term posi-tive experiences both from Finland and from other parts of Europe. In structures containing recycled asphalt concrete successful compaction is a significant factor. Fly ash is also a poten-tial material for road and street structures and it has been successfully used in improving the bearing capacity of low volume roads. Fly ash is sensitive to moisture, which must be taken into account in the design and during construction. Most of (MSWI) bottom ash studies focus on its environmental impact. However, structures made of it have mostly been performing well. The use of tire shreds and bales as a lightweight material in low-volume roads has been tried with good results. Large compressibility of these materials can, however, cause prob-lems. Experiences on their use as an insulation material vary.

In connection with this study some examples of approaches used for mechanical modelling of test structures containing alternative construction materials were found. As such they can not, however, be transferred as analysis tools for the types of structures containing alterna-tive materials in Finland. One small step towards developing of such a tool was taken in con-nection with this research when the mechanical behavior of some example structures was analyzed using the traditional Oedemark’s bearing capacity calculation method, multi-layer linear elastic analysis and 3D Finite Element Modelling. A fundamental observation from these analyses was that the mechanical behavior of structures containing alternative con-struction materials can be markedly different from the traditional type of structures. Conse-quently, there is an obvious need for development of a load carrying capacity design ap-proach tailored for this type of structures.