This thesis deals mainly with road construction materials, particularly in cases where they may contribute to polluting substances. The study is not focused on one clearly defined pollutant or material. Rather its aim is to consider the complexity of the measuring and evaluation of some pollutants with respect to sampling and chemical analysis. The research reported is therefore fairly broad. Asphalt wear can be considerable in areas with intensive use of studded tyres. Field measurements showed that large amounts of the solids accumulated in the snow along a rural highway could be attributed to asphalt wear. The wear particles evidently contained metals, of which many were the same as those attributed to vehicle emissions. Elements which also had other sources than the asphalt were Cr, Cu, Ni, Pb, Zn, V and S. The composition of the asphalt wearing courses was reflected in the elements found in the snow, which indicated a possibility of distinguishing asphalt pavements comprising different types of mineral aggregates. When the accumulated solids (from the snowbanks) were exposed to leaching at a pH of 4, only a minor part of the elements was released (0-10 percent of the original content). The results suggest that most elements are bound in the matrix of particles and are not very amenable to leaching. Road dust accumulated during the autumn was also tested for leaching. To investigate the adsorption and release of metals, laboratory experiments were designed and carried out. The adsorption characteristics of Zn, Cu, Cd, and Pb were tested on two minerals. The metals showed the same individual properties irrespective of the sorbent, but the adsorption capacities of the minerals differed, the one mineral (gabbro) being able to absorb 3-4 times more metal ions than the other (porphyry). Through material analyses, polyaromatic hydrocarbons (PAH) were found in bituminous binders. These binders constitute approximately 5 percent of an asphalt, thus the PAH concentrations in the asphalt become low, a very few ppm. PAH were also detected in tyre rubber with concentrations of up to around 90 ppm, where pyrene was distinguished as the major one. Asphalt was shown to be not very susceptible to leaching, which is due to the hydrophobic properties of asphalt. Field measurements, aimed at evaluating leaching from road construction materials, were carried out at a road constructed with a porous asphalt and unbound base layers. The construction materials (macadam and blast furnace slag) as well as drainage water were analysed for chemical composition. The metals found in the drainage water were mainly the same as those comprising the construction materials. Blast furnace slag was physically and chemically characterised and tested for leaching. Leaching of sulphur was observed and also the significance of considering the size of the specific surface area exposed to the leaching, as it is a crucial parameter when estimating the total amounts of leached substances. (A)

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  • Corporate Authors:

    Luleaa Hoegskola

    Avdelningen foer Transportteknik
    Luleaa,   Sweden 
  • Authors:
  • Publication Date: 1998


  • English

Media Info

  • Features: References;
  • Pagination: 130 p.
  • Serial:

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Filing Info

  • Accession Number: 00818889
  • Record Type: Publication
  • Source Agency: Swedish National Road and Transport Research Institute (VTI)
  • Files: ITRD
  • Created Date: Nov 7 2001 12:00AM