CHANGES IN THE PROPERTIES OF ROCK AGGREGATES IN THE PASSAGE THROUGH THE DRYING DRUM OF A HOT MIX PLANT

AENDERUNGEN DER EIGENSCHAFTEN VON GESTEINSZUSCHLAEGEN BEIM DNRCHGANG DURCH TROCKENTROMMELN VON HEISSMISCHANLAGEN

A considerable reduction in the strength properties is accounted for by loosening of the structure, which arises from the different degrees of thermal expansion of the various minerals of a rock or, in the case of large crystal rock, from the anisotropy of the thermal expansion of the individual crystals. Such a strength reducing, structural loosening may be assessed by a thorough petrographic study. Improvements of the strength properties are achieved through breakdown of brittle grains, corner wear and breaking-off of conglomerates and caked material. Particle refinement is also brought about by these and by the elimination of weak points and the chipping of grains caused by heat stress. This refinement of the material is to be achieved by appropriate regulation of the materials feeding process and of the hot screening. In the checking of the bitumen adhesion an improvement was noted only in cases of material with a natural affinity in the raw (supplied) condition. Some materials, which, according to the results of standard tests should definitely require a binding additive, achieved a considerable improvement because of surface heat treatment or drying out of the binder grains. In future the behaviour of the binder coating under water immersion should only be determined by putting the materials to be tested through a drying drum. /TRRL/

• Corporate Authors:

  Forschungsgesellschaft fuer Strassenwesen, Austria

  Eschenbachaasse 9
  110 Vienna,   Austria 
• Authors:
  • Eppensteiner, W
• Publication Date: 0

Language

• German

Media Info

• Features: Figures; Photos; References; Tables;
• Pagination: p. 32-40

Subject/Index Terms

• TRT Terms: Adhesion; Aggregates; Asphalt plants; Binders; Chemical processes; Chippings; Driers (Devices); Dryer drum process; Drying; Gravel; Hot coated materials; Metal heating; Minerals; Mixing plants; Properties of materials; Refining; Rocks; Strength of materials; Thermal expansion
• Uncontrolled Terms: Heat treatment; Modifications
• Old TRIS Terms: Aerobic processes; Aggregate drier
• ITRD Terms: 4585: Chippings; 5184: Drying; 4575: Gravel; 4997: Hot coated material; 3648: Mixing plant; 9048: Modification; 5925: Properties
• Subject Areas: Construction; Geotechnology; Highways; Materials; I36: Aggregates;

Filing Info

• Accession Number: 00157465
• Record Type: Publication
• Source Agency: Bundesanstalt für Straßenwesen (BASt)
• Report/Paper Numbers: Publication No. 65 Monograph
• Files: ITRD, TRIS
• Created Date: Dec 8 1977 12:00AM