A RECOMMENDED SYNTHETIC COARSE AGGREGATE CLASSIFICATION SYSTEM (REVISED AUGUST, 1969)

RESEARCH WAS CONDUCTED ON SYNTHETIC AGGREGATES FOR HIGHWAY USE. A REVISION IS PRESENTED OF THE RECOMMENDED SYNTHETIC AGGREGATE CLASSIFICATION SYSTEM FOR HIGHWAY CONSTRUCTION, BASED ON THE RESULTS OF THE RESEARCH STUDIES. THIS CLASSIFICATION SYSTEM IS NOT INTENDED TO REPLACE OR SUPPLANT EXISTING REQUIREMENTS FOR SYNTHETIC AGGREGATES IN HIGHWAY CONSTRUCTION, BUT IS OFFERED AS A SUPPLEMENT TO EXISTING AGGREGATE REQUIREMENTS. THE DRY LOOSE UNIT WEIGHT IS USED AS A QUALITY ACCEPTANCE CRITERIA. IT IS RECOMMENDED THAT THE DRY LOOSE WEIGHT DETERMINATION BE MADE IN ACCORDANCE WITH TEX-404-A, EXCEPT THAT THE AGGREGATES SHALL BE TESTED IN AN OVEN-DRY CONDITION. THE SAMPLES SHALL CONSIST OF THE ONE-HALF TO NO. 4 FRACTION AND SHALL HAVE 30-70 PERCENT BY WEIGHT RETAINED ON THE 3/8 INCH SIEVE. EXAMINATION OF THE TEXAS HIGHWAY DEPARTMENT AGGREGATE GRADATION SPECIFICATIONS FOR PORTLAND CEMENT CONCRETE, SEAL COATS AND HOT MIX ASPHALT PAVEMENTS REVEALS THAT A MAJOR PORTION OF THE AGGREGATE SKELETON WILL BE INCLUDED WITHIN THIS SIZE RANGE. COARSE SYNTHETIC AGGREGATE IS DIVIDED INTO TWO CLASSES AND EACH CLASS IS SUBDIVIDED INTO THREE GROUPS OF DESCENDING PHYSICAL REQUIREMENTS. THE MAXIMUM UNIT WEIGHT VALUES USED FOR GROUP 1 (55 PCF) WERE TAKEN FROM ASTM DESIGNATION C330-64T. IN ORDER TO DELINEATE GROUP 2 FROM GROUP 1, THE MINIMUM UNIT WEIGHTS FOR GROUP 2 WERE SET AT 55 PCF. THE USE OF THE 35 PCF MINIAL WEIGHT FOR GROUP 1 IS TO ENSUE THAT ONLY STRUCTURAL QUALITY COARSE AGGREGATES WILL BE USED. A TABLE IS PRESENTED SHOWING THE PERMISSIBLE COARSE AGGREGATE GROUP DEFINED FOR EACH HIGHWAY FUNCTION, FROM SURFACE TREATMENT TO BASE MATERIALS.