Abstract
With natural (fluvial, glaciofluvial) sand/gravel resources being rapidly depleted in many countries, the last decade has seen a significant trend towards using more alternative materials for construction purpose. In Norway the development and implementation of crushed aggregate technology has been the most important way to get around the problem with increased resource scarcity. Today Norway is one of the European countries with the highest percentage of crushed/manufactured aggregates. A crushed product will reveal a different particle size distribution, a sharper, more angular particle shape, and not least – a significantly different mineral composition. The latter may often be characterised by more polymineral composition, and it will also much more depend on the local bedrock. When handled with care and knowledge, these differences can give the user a lot of new opportunities relating to materials design.
In Norway, research is currently being undertaken to study the properties of crushed aggregates for road construction – specifically relating to frost heave protection and the development of new guidelines for this purpose. During the spring 2014 The Norwegian Public Roads Administration introduced a new handbook with requirements for roads construction in Norway, including new specifications for the frost protection layer. When pavements are constructed over moist and/or frost susceptible soils in cold and humid environments, the frost protection layer also becomes a very important part of the road system. According to new specification, the allowed amount of fines content (<0.063 mm) was increased to 15% (calculated for the material less than 22.4 mm).
Analysing these new requirements, several questions are arising. First of all how this materials size will affect heat exchange in the layer, secondly – if the allowable fines content will make the materials frost susceptible.
Various publications emphasise the outstanding effect of the mineral content of fine grains on the frost susceptibility of soils. But detailed quantitative information with regard to the allowable contents of fine grains and specific (clay) minerals in order to provide a certain degree of safety against freezing-thawing damage on roads, highways, railways, airfields, etc., is rarely available.
The study presented here is part of a larger research program to investigate the properties of crushed rock materials in relation to frost heaving in the frost protection layer. An important issue will be the resistivity for frost penetration due to presence of water and fine particles. Due to new requirements for allowed fines content, it is essential to investigate if increased amount of fines <0.063 mm together with increased water content in the frost protection layer, will not lead to more frost heave problems.
Novel research as well as innovative industrial development relating to manufactured (crushed) aggregates has involved technologies to control even the particle size distribution of the fines. The industrial perspective to be followed up is to tailor-make not only the sand grading and fines content, but also the grading curve of the finest fractions (crusher fines as well as industry fillers), to meet requirements designed by the frost properties research. Also – since the mineral composition of the fines influences upon the properties – a part of the industrial perspective will also be to do the necessary mineralogical analyses in order to choose the rock, and to design the fines grading and amount in relation to the mineral composition.
In Norway, research is currently being undertaken to study the properties of crushed aggregates for road construction – specifically relating to frost heave protection and the development of new guidelines for this purpose. During the spring 2014 The Norwegian Public Roads Administration introduced a new handbook with requirements for roads construction in Norway, including new specifications for the frost protection layer. When pavements are constructed over moist and/or frost susceptible soils in cold and humid environments, the frost protection layer also becomes a very important part of the road system. According to new specification, the allowed amount of fines content (<0.063 mm) was increased to 15% (calculated for the material less than 22.4 mm).
Analysing these new requirements, several questions are arising. First of all how this materials size will affect heat exchange in the layer, secondly – if the allowable fines content will make the materials frost susceptible.
Various publications emphasise the outstanding effect of the mineral content of fine grains on the frost susceptibility of soils. But detailed quantitative information with regard to the allowable contents of fine grains and specific (clay) minerals in order to provide a certain degree of safety against freezing-thawing damage on roads, highways, railways, airfields, etc., is rarely available.
The study presented here is part of a larger research program to investigate the properties of crushed rock materials in relation to frost heaving in the frost protection layer. An important issue will be the resistivity for frost penetration due to presence of water and fine particles. Due to new requirements for allowed fines content, it is essential to investigate if increased amount of fines <0.063 mm together with increased water content in the frost protection layer, will not lead to more frost heave problems.
Novel research as well as innovative industrial development relating to manufactured (crushed) aggregates has involved technologies to control even the particle size distribution of the fines. The industrial perspective to be followed up is to tailor-make not only the sand grading and fines content, but also the grading curve of the finest fractions (crusher fines as well as industry fillers), to meet requirements designed by the frost properties research. Also – since the mineral composition of the fines influences upon the properties – a part of the industrial perspective will also be to do the necessary mineralogical analyses in order to choose the rock, and to design the fines grading and amount in relation to the mineral composition.