The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Fly Ash Mixtures as Flexible Structural Materials for Low-Volume Roads

Pentti Lahtinen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission for public examination and debate in Auditorium R1 at Helsinki University of Technology (Espoo, Finland) on the 7th of December, 2001, at 12 noon.

Overview in PDF format (ISBN 951-22-5707-6)   [2711 KB]
Dissertation is also available in print (ISBN 951-726-826-2)

Abstract

Extensive research and several studies have been carried out on the recycling of industrial by-products in soil construction in Finland in the 1990's. The research and studies have been made mainly in the laboratory of SCC Viatek Ltd SGT in cooperation with the public research institutes. The main beneficiaries have been the industry, the national road administration and the municipalities.

The Doctoral Thesis focuses on the versatile usage opportunities of the fly ashes (FA) from the combustion of coal and biofuel like peat and wood and their mixtures with certain other industrial by-products in soil construction. The main objective of this thesis is to show the conditions and premises on which the NRC (New Recycled Construction) -materials are at least as viable or even more viable than the natural stone materials in the applications for low-volume roads. The research and studies have succeeded in the development of new materials and structure applications for low-volume roads, proper equipment and work methods to manufacture the NRC-structures and proper test methods for the quality assurance of the materials.

The new FA-based construction materials include; a) materials based on FA, fibre-ashes, gypsum-ashes and slag-ashes for NRC-solid structures; b) binder admixtures based on FA for the stabilisation of old road structure courses; c) binder admixtures based on FA for the mass-column stabilisation of soft soil. It has been shown that FA from biofuel that have been studied relatively little so far may have even better geotechnical properties than the FA from coal. Additionally it has been possible to attain a versatile array of materials by mixing the FA with fibre sludge (outcome: fibre-ashes), process gypsum (outcome: gypsum-ashes) or stainless steel slag (outcome: slag-ashes). The properties of the different mixtures can be regulated by changing the proportion of different components. Thus, it has been possible to find proper materials for low-volume roads that require high heat insulation, deformation durability and bearing capacity.

The studies on the test methods have been focused on the methods and criteria to optimise the properties and to assess the long-term durability of the NRC-materials. It has been possible to show that the most important methods to assess the long-term durability are the tests for frost susceptibility and the freeze-thaw durability. It is not possible to judge the long-term durability of NRC-materials with the mere stress-strain tests. Also the environmental impact of the NRC-materials has been studied both in the laboratory by leaching tests and in the full-scale test structures with samples of soil and groundwater. The studies include also the use of a mathematical dynamic transportation model to predict the distribution of molybdenum from the coal ash structures to the environment surrounding the structures. The environmental studies indicate that there is no environmental risk involved in the use of FA-based materials in soil construction, assuming that the materials are used in a proper way.

NRC-technology will make the sustainable road construction possible. The durable NRC-structures will be economically viable alternatives to the conventional stone structures. Additionally it will be possible to save even 24 % of the non-renewable gravel and other natural resources, and there will be less need to use land for deposits or for stone intake at sensitive groundwater areas.

This thesis consists of an overview and of the following 6 publications:

  1. Lahtinen, P., Jyrävä, H., Suni, H. (1999): New methods for the renovation of gravel roads. Paper for IRF Regional Conference, European Transport and Roads, Lahti 24-26. May 1999. 7 pages.
  2. Lahtinen, P., Fagerhed, J.A., Ronkainen, M. (1998): Paper Sludge in Road Construction. Paper for the Proceedings of the 4th International Symposium on Environmental Geotechnology and Global Sustainable Development, 9. - 13. August 1998, Boston (Danvers). University of Masschusetts, Lowell, pp. 410-419. 9 pages.
  3. Lahtinen, P., Jyrävä, H., Kuusipuro, K. (2000): Deep Stabilisation of Organic Soft Soils. Paper for the Proceedings of the Grouting Soil Improvement Geosystems including Reinforcement of the 4th GIGS, the International Conference on Ground Improvement Geosystems, by the Finnish Geotechnical Society in Helsinki, 7-9. June 2000, pp. 89-98. 10 pages.
  4. Lahtinen, P., Jyrävä, H., Suni, H. (2000): New Methods for the Renovation of Gravel Roads. Paper for the Proceedings of the NGM-2000, XIII Nordiska Geoteknikermötet, Helsinki 5. -  7. Juni 2000. Building Information Ltd., Helsinki, pp. 531-538. 8 pages.
  5. Lahtinen, P., Jyrävä, H., Suni, H. (2000): Use of Industrial Wastes in the Construction of Low-Volume Roads. Paper for the conference of Geo-Denver 2000, 5. - 8. August 2000. Proceedings pending. 11 pages.
  6. Lahtinen, P., Palko, J., Karvonen, T. (2000): Molybdenum transport in coal fly ash soil constructions. Paper for Ecogeo-2000, International Conference on Practical Applications in Environmental Geotechnology, Helsinki 4. - 6. September 2000. Proceedings pending. 7 pages.

Keywords: recycling, waste, residues, by-products, road materials, road structures, applications, construction, geotechnics, environmental effects, low-volume roads, gravel roads, fly ash

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© 2001 Helsinki University of Technology

Last update 2011-05-26