Why is concrete replacing bituminous roads


In the case of repair and renewal projects on motorways and federal roads, the greater part of the old asphalt is used for unbound base layers (often on secondary roads) after it has been shredded; high-quality aggregates are obtained and supplied for the new superstructure. Old asphalt should serve as a supplement for new concrete in the highest possible proportions. For this purpose, in laboratory tests on road sub-concrete with natural gravel or recycling surcharge made from old concrete, the surcharge 4/32 was replaced by different proportions of recycled old asphalt and tested for strength (flexural tension, pressure, splitting tension) and modulus of elasticity up to the age of 180 days, Frost resistance and frost / de-icing salt resistance checked. The addition of asphalt impaired the strength of the water / cement ratio, and from a certain percentage also the resistance to freeze-thawing salt. These impairments could, however, be compensated for by concrete technology measures. If the asphalt content in grain 4/32 is less than 40 to 50 percent, it is sufficient to lower the water / cement value by adding an appropriate condenser to achieve RVS-based strength. Resistance to frost and de-icing salt is achieved as usual with LP concrete. 20 percent of the rough surcharge for the sub-concrete of a new ceiling can be covered by reconditioned asphalt (the old parking strip or the bituminous underlay of the old concrete ceiling). Concrete with old asphalt as surcharge is technically equivalent to natural surcharge if the concrete recipe is adapted accordingly and concrete production is even. The decision can thus be made depending on the local cost situation, taking into account the transport burden and protection of natural occurrences. A prerequisite for practical execution is a uniform production, especially uniformity with regard to the type and proportion of old asphalt.

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  • Publication Date: 1998


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  • Accession Number: 01229963
  • Record Type: Publication
  • Source Agency: Federal Highway Research Institute (BASt)
  • Files: ITRD
  • Created Date: Nov 19 2010 7:22 PM