LABORATORY AND FIELD EVALUATION OF LIGHTWEIGHT AGGREGATES AS COVERSTONE FOR SEAL COATS AND SURFACE TREATMENTS

THE RECENT INTRODUCTION OF LIGHTWEIGHT AGGREGATE AS A COVERSTONE FOR SEAL COATS AND SURFACE TREATMENTS WAS PROMPTED BY PREDICTED IMPROVED CONSTRUCTION AND SERVICE CHARACTERISTICS OF THE MATERIAL. A LABORATORY EVALUATION WAS CONDUCTED OF LIGHTWEIGHT AGGREGATES FROM 7 SOURCES, 6 IN TEXAS AND 1 IN LOUISIANA, CONSISTING OF EXPANDED CLAY AND SHALE. THE PRIMARY OBJECTIVES WERE TO DETERMINE WHETHER OR NOT LIGHTWEIGHT /SYNTHETIC/ AGGREGATES ARE ACCEPTABLE AS EQUAL TO PRECOATED LIMESTONE AVAILABLE IN THE SAME GENERAL MARKET AREA. TO COMPARE THE PHYSICAL CHARACTERISTICS OF THE LIGHTWEIGHT AGGREGATE WITH THE ACCEPTED SERVICEABILITY OF PRECOATED STONE, IT WAS NECESSARY TO DESIGN AND CARRY OUT AN EXTENSIVE LABORATORY STUDY ON THE LIGHTWEIGHT MATERIAL. FOLLOWING CONCLUSIONS WERE MADE' /1/ FOR SEAL COATS AND SURFACE TREATMENTS A MINIMUM AS WELL AS A MAXIMUM UNIT WEIGHT IS RECOMMENDED, /2/ LABORATORY DESIGN AND EVALUATION OF SEAL COATS, PREPARATORY TO CONSTRUCTION, RESULT IN IMPROVED OVERALL ECONOMY, /3/ LABORATORY STUDIES AND FIELD OBSERVATIONS SHOWED THAT THE LIGHTWEIGHT MATERIAL HAD A STRONG AFFINITY FOR ALL THE ASPHALT-CEMENTS USED IN THE PROJECT, /4/ CRUSHING OF COVERSTONE IS MINIMIZED WHEN THE PNEUMATIC ROLLER ALONE IS USED TO SEAT THE COVER MATERIAL, AND IT IS RECOMMENDED THAT ONLY PNEUMATIC ROLLING OF LIGHTWEIGHT AGGREGATE BE PRACTICED, /5/ THE STEEL FLAT ROLLER CAUSED DEGRADATION OF BOTH TYPES OF COVERSTONE PARTICULARLY IN AREAS OF IRREGULAR CROSS-SECTION, /6/ LABORATORY INDUCED WINDSHIELD DAMAGE WAS SEVERE FOR THE CRUSHED LIMESTONE AND PRACTICALLY INSIGNIFICANT FOR THE LIGHTWEIGHT MATERIALS, /7/ THE TEXAS AND LOUISIANA MODIFICATIONS OF THE LOS ANGELES ABRASION TEST WERE FOUND TO BE LESS SEVERE THAN THE ASTM STANDARD TEST WHEN USED TO MEASURE THE ABRASION RESISTANCE OF THE LIGHTWEIGHT MATERIALS UNDER STUDY, /8/ ONE HUNDRED CYCLES OF RAPID FREEZE-THAW CAUSED A SIGNIFICANT LOSS FOR SOME GRADE 3 AND GRADE 4 LIGHTWEIGHT MATERIALS, /9/ LIGHTWEIGHT AGGREGATE A SHOWED A MAXIMUM WEIGHTED AVERAGE LOSS OF 1.56 PERCENT WHEN SUBJECTED TO 5 CYCLES OF THE MAGNESIUM SULFATE SOUNDNESS TEST WHICH COMPARED TO 3.07 PERCENT LOSS FOR THE SAME MATERIAL AFTER 100 CYCLES OF RAPID FREEZE-THAW, /10/ UNDER A VARIETY OF CONSTRUCTION AND SERVICE CONDITIONS, LIGHTWEIGHT AGGREGATE A, AFTER 1 TO 4 YEARS OF SERVICE, PROVED TO BE A HIGHLY SUCCESSFUL COVER TREATMENT FOR SEALS AND SURFACE TREATMENTS, /11/ VOLUME OF VEHICULAR SERVICE APPEARS TO HAVE NO MEASURABLE EFFECT ON THE DEGRADATION OF LIGHTWEIGHT AGGREGATE A, /12/ THE LIGHTWEIGHT AGGREGATE WAS FAVORABLY ACCEPTED BY CONTRACTORS AND TEXAS HIGHWAY DEPARTMENT PERSONNEL THROUGHOUT THE AREA IN WHICH IT WAS USED, AND /13/ LIGHTWEIGHT AGGREGATE A IS CONSIDERED EQUAL TO PRECOATED LIMESTONE FOR SEAL COAT AND SURFACE TREATMENT WORK.

Media Info

  • Media Type: Print
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: pp 25-81
  • Monograph Title: Asphalt pavements, bases and surface treatments
  • Serial:

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Filing Info

  • Accession Number: 00210606
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Nov 18 1994 12:00AM