STUDIES OF THE THERMAL TRANSFORMATION OF SYNTHETIC AGGREGATES PRODUCED IN A ROTARY KILN

THE WIDE VARIATIONS FOUND IN THE PROPERTIES OF SYNTHETIC AGGREGATES MADE FROM CLAY-TYPE MATERIALS MAY BE DUE IN LARGE PART TO DIFFERENCES IN THE DEGREE OF THERMAL TRANSFORMATION OF THEIR CONSTITUENTS RESULTING FROM PROCESSING IN ROTARY KILNS. IN ORDER TO STUDY THIS PROBLEM, TWO DIFFERENT CLAYS WERE PROCESSED IN A RESEARCH ROTARY KILN UNDER DIFFERENT CONDITIONS OF TEMPERATURE AND RETENTION TIME. FOR EACH MATERIAL, FIRING CONDITIONS WERE PLANNED TO YIELD TWO GROUPS OF AGGREGATES, ONE HEAVY (MORE THAN 55 LBS. PER CU. FT.) AND ONE LIGHT (< 55 LBS. PER CU.FT.). THE RAW CLAYS & THE RESUL- TING AGGREGATES, AS WELL AS A COMMERCIAL SYNTHETIC AGGREGATE FOR COMPARISON, WERE INVESTIGATED BY X-RAY DIFFRACTION, DIFFERENTIAL THERMAL ANALYSIS (DTA), EFFLUENT GAS ANALYSIS (EGA), AND GAS CHROMATOGRAPHY (GC). THIS COMBINATION OF METHODS YIELDED USEFUL INFORMATION CONCERNING THE EXTENT OF THE TRANSFORMATION OF THE CLAY MINERALS INTO NEW CRYSTALLINE SUBSTANCES, THE ELIMINATION OF IMPURITIES (SUCH AS ORGANIC MATTER, CARBONATES, AND SULFUR COMPOUNDS), AND THE GASES RESPONSIBLE FOR BLOATING. FROM THIS INFORMATION THE POORLY BURNED AGGREGATES COULD BE IDENTIFIED. RETENTION TIME AS WELL AS TEMPERATURE WAS SHOWN TO BE IMPORTANT IN BRINGING THE THERMAL REACTIONS TO COMPLETION. THE MOST EFFECTIVE COMBINATION OF TEMPERATURE AND RETENTION TIME DEPENDS UPON THE PARTICULAR RAW MATERIAL. FIRING CONDITIONS PRODUCING A LIGHTWEIGHT AGGREGATE DO NOT AUTOMATICALLY INSURE THAT THE AGGREGATE WILL BE CHEMICALLY AND PHYSICALLY SOUND. THE EFFECTS OF THE DEGREE OF THERMAL TRANSFORMATION OF THE ENGINEERING PROPERTIES OF THESE AGGREGATES, AND ON THEIR BEHAVIOR IN CONCRETE, ARE DISCUSSED IN REPORTS 81-8 AND 81- 10. /AUTHOR/

• Supplemental Notes:
  • Hpr, 81
• Corporate Authors:

  Texas Transportation Institute

  Texas A&M University System, 1600 E Lamar Boulevard
  Arlington, TX  United States  76011

  Texas State Department of Highways & Public Transp

  11th and Brazos Streets
  Austin, TX  United States  78701

  Bureau of Public Roads /US

  400 7th Street, SW
  Washington, DC  United States  20590
• Authors:
  • Houston, J T
  • Blank, H R
  • Kunze, G W
• Publication Date: 1969-8

Subject/Index Terms

• TRT Terms: Aggregates; Artificial aggregates; Cement kilns; Clay; Clay minerals; Differential thermal analysis; Diffraction; Gas analysis; Gas chromatography; Lightweight aggregates; Materials tests; Ovens; Retaining walls; Temperature; Terminations; Thermal properties; X rays
• Uncontrolled Terms: Aggregate testing; X-ray diffraction
• Old TRIS Terms: Aggregate characteristics; Retaining
• Subject Areas: Geotechnology; Highways;

Filing Info

• Accession Number: 00217489
• Record Type: Publication
• Source Agency: Bureau of Public Roads /US
• Files: TRIS, STATEDOT
• Created Date: Dec 22 1994 12:00AM