28-09-2013, 03:02 PM
RECYCLING OF INDUSTRIAL BY-PRODUCTS FOR SOIL CON- STRUCTIONS IN FINLAND
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Introduction
In Finland, the development of soil construction materials based on Different industrial by-products
has brought along a wide and versatile choice of different materials and applications for soil con-
struction. For utilization, the most important by-products are generated in energy production and by
the metallurgical, chemical, forest and mining industries. Most of the applications are created for
the road construction and landfill constructions.
The increasing public pressure on environment protection is one of the most important reasons for
the development stated above. The environment will benefit from the savings of un-renewable natu-
ral materials and from the decreasing need to use land for waste disposal. However, there are also
both technical and economical benefits from the utilization of new materials based industrial by-
products compensating for traditional construction materials.
Recyclable by-products
Recyclable by-products can be found within many industrial branches: the energy production, and
the mining, chemical, steel, construction and the pulp and paper industry. Table (1) fives a list of
the of by-products that mainly are being used for soil construction in Finland.
Within and between the groups in Table (1) there are essential differences between the individual
by-products from different sources (mills, power plants) with respect to their characteristics and
properties and, consequently, their scope of usage in soil construction applications. For example,
the power plants produce various ashes the characteristics and properties of which depend on the
properties and quality of the feedstock and on several parameters on the incineration process.
Ashes
In Finland, around 1,2 million tons of different ashes are generated each year. Out of this, about
half is from the coal combustion prosesses and the other half from power plants combusting peat,
wood and miscellaneous feedstock as fuel.
Apart from the environmental benefits there are both technical and cost related reasons to support
the use of ashes as construction material: for example most of the ashes are beneficial for road base
and sub-base courses due to their significant strength development, frost resistance and lightness.
This fact brings along economic benefits; for example, sometimes a road can be constructed and
maintained with even 50 % less costs than by using traditional construction materials, Nowadays,
research and development of ashes is concentrated on the utilization of ashes as stabilization com-
ponent for different types of soil as as a binder component for materials based on other industrial
by-products.
Fibre wastes
Each year Finnish forest industry is generating around 0,5 million m3 of fibre wastes which can be
utilized in soil construction. The development of fibre wastes for soil construction applications
started in Finland at the beginning of the 1990's. The most important applications are the sealing
layers of landfills and the different courses and structures of road construction.
In Finland, the fibre-ashes and stabilized fibre waste has been used in road tests constructions. The
preliminary results are very promising. The fibre waste gives the road resilience or deformation
resistance, which is important for road constructions on slightly frost heaving or yielding sites.
Road construction materials based on fibre waste also bring along cost savings in construction.
Development of new soil construction materials
Re-use of industrial by-products in soil construction requires massive and wide research and devel-
opment. For example, during the development there have been separate test arrangements for the
resistance to fatigue in different climatic circumstances and with different traffic loads. Further, In
Finland Viatek Ramboll Ltd. has developed a laboratory testing system where a sample is tested for
durability andresistance to fatigue with different successive stress factors like acid seepage water,
freeze-thaw cycles, impregnation with water and loading. The environmental acceptability of new
materials is essential, and it is studied mostly by leaching tests and by analyzing the content of envi-
ronmentally harmful substances in leachates and in by-product itself. The environmental tests are
run parallel with the technical tests.