PERFORMANCE STUDIES OF SYNTHETIC AGGREGATE CONCRETE

THE RESULTS ARE REPORTED OF THREE EXPERIMENTAL PROGRAMS CONDUCTED ON SYNTHETIC AGGREGATES: PHYSICAL DURABILITY, CHEMICAL DURABILITY, AND MECHANICAL DURABILITY. IN THE PHYSICAL DURABILITY PROGRAM, FIVE SELECTED COMMERCIALLY PRODUCED AND EIGHT TTI KILN-PRODUCED LIGHTWEIGHT COARSE AGGREGATES WERE INVESTIGATED. ABSORPTION CHARACTERISTICS AND POROSITY VALUES WERE DETERMINED FOR EACH OF THE AGGREGATES. A TOTAL OF 69 BATCHES OF CONCRETE USING THESE COARSE AGGREGATES AND NATURAL SAND WERE MIXED AND TESTED IN ACCORDANCE WITH ASTM C290. VARIOUS DEGREES OF SATURATION OF THE COARSE AGGREGATES AT THE TIME OF MIXING WERE OBTAINED BY IMMERSING THEM IN WATER FOR PERIODS RANGING FROM 6 HOURS TO 180 DAYS. THE RESISTANCE OF STRUCTURAL LIGHTWEIGHT CONCRETE TO FREEZING AND THAWING AS MEASURED BY ASTM C290 WAS GREATLY INFLUENCED BY THE DEGREE OF SATURATION OF THE COARSE AGGREGATE AT THE TIME OF MIXING. FOR THE CONCRETES INVESTIGATED, THE CRITICAL DEGREE OF SATURATION OF THE COARSE AGGREGATE AT THE TIME OF MIXING WAS FOUND TO BE ABOUT 0.25. EXPERIMENTS ON CHEMICAL DURABILITY CENTERED UPON THE DETECTION AND POSSIBLE EFFECTS OF DELETERIOUS SUBSTANCES LIKELY TO BE PRESENT, SUCH AS "UNDERBURNED" CLAY MINERALS, LUMPS OF LIME AND OF ANHYDRITE, AND DECOMPOSABLE SULFIDES. UNDERBURNED CLAY MINERALS CAN SOMETIMES BE DETECTED BY PETROGRAPHIC AND DTA METHODS, MORE DEFINITELY BY X-RAY DIFFRACTION. SIMPLER TESTS, SUCH AS BOILING IN A PRESSURE COOKER, ARE ALSO REPORTED. IT WAS FOUND THAT LUMPS OF LIME DISINTEGRATE DURING MIXING OF CONCRETE, BUT LUMPS OF ANHYDRITE HYDRATE MORE SLOWLY AND EXPAND, CAUSING SWELLING AND DISTORTION OF CONCRETE TEST BARS. THE MECHANICAL DURABILITY PROGRAM WAS DESIGNED AS A PILOT STUDY OF THE ABRASION RESISTANCE CHARACTERISTICS OF SYNTHETIC AGGREGATES. THE TEST USED IN THE INVESTIGATION WAS ASTM C418-67T, "METHOD OF TEST FOR ABRASION RESISTANCE OF CONCRETE (TENTATIVE)." THIS TEST MEASURES ABRASION IN TERMS OF THE VOLUME OF MATERIAL ERODED BY A STREAM OF STANDARD SIZE SAND PARTICLES, BLASTED ONTO A SPECIFIED SURFACE AREA. LABORATORY TESTS WERE PERFORMED ON SPECIMENS MADE WITH FOUR COMMERCIALLY PRODUCED SYNTHETIC AGGREGATES AND ONE COMMERCIAL NATURAL GRAVEL AGGREGATE. ALL LABORATORY TESTS WERE PERFORMED ON SAWN SURFACES TO EXPOSE THE AGGREGATE AND THEREFORE AMPLIFY THE EFFECTS OF THE AGGREGATE. REPRODUCIBILITY OF THE METHOD IN TERMS OF COEFFICIENT OF VARIATION WAS FOUND TO VARY WITH MOISTURE CONTENT OF THE SPECIMENS. THE RESULTS OBTAINED ON SPECIMENS SOAKED 24 HR. PRIOR TO TESTING (AS SPECIFIED IN ASTM C418-67T) WERE MORE CONSISTENT THAN THOSE OBTAINED ON AIR DRY SPECIMENS. THERE WAS NO SIGNIFICANT DIFFERENCE IN THE PERFORMANCE OF THE SYNTHETIC AGGREGATE CONCRETES TESTED. HOWEVER, THEY ALL EXHIBITED HIGHER LOSSES THAN THE NATURAL GRAVEL CONCRETE. THE CEMENT FACTOR OF THE CONCRETE DID NOT SIGNIFICANTLY AFFECT THE RESULTS OBTAINED. /AUTHOR/

  • Supplemental Notes:
    • Res Rept No 81-86, 27 PP, 32 FIG, 5 TAB, 28 REF
  • Corporate Authors:

    Texas Transportation Institute

    Texas A&M University System, 1600 E Lamar Boulevard
    Arlington, TX  USA  76011
  • Authors:
    • Buth, E
    • Blank, H R
    • McKeen, R G
  • Publication Date: 1968-9

Subject/Index Terms

Filing Info

  • Accession Number: 00213414
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Mar 16 1970 12:00AM