A LABORATORY METHOD TO DETERMINE POLISH SUSCEPTIBILITY OF AGGREGATES
A LABORATORY PROCEDURE IS DEVISED TO EVALUATE THE POLISHING TENDENCIES OF AGGREGATES. THE DESIGN OF THE POLISHING MACHINE IS AIMED AT REPRODUCING THE ACTION OF TRAFFIC IN THE FIELD. THE POLISHING INSTRUMENT IS A PAIR OF 7:50 X 14 ASTM E-17 TEST TRAILER TIRES CHASING EACH OTHER AROUND A 6-FT DIAMETER CIRCLE AT ABOUT 22 1/2 RPM DAY AND NIGHT. THE DIAMETER TRACK IS DIVIDED INTO 16 EQUAL SEGMENTS, EACH OF WHICH HOLDS ONE SAMPLE, ENABLING REPLICATE TESTS TO BE CONDUCTED ON ONE OR MORE AGGREGATES AT A TIME. THE SIZES OF AGGREGATE PARTICLES WERE TESTED FOR THEIR INFLUENCE ON THE SYSTEM. THREE TYPES OF SAMPLES WERE USED: PARTICLES PASSING A 3/4 IN. SIEVE AND RETAINING ON A 5/8 IN. SIEVE, MATERIAL BETWEEN 3/8 AND 1/4 IN., AND A ROCK SLAB. ONCE THE SPECIMENS ARE MOUNTED IN THE ROCK, THEY ARE EXPOSED TO CONTINUOUS TRAFFIC AT THE RATE OF 32,500 REV. PRODUCING 65,000 COVERAGES PER DAY. THE SKID RESISTANCE OF EACH SAMPLE IS MEASURED DURING THE "PIT STOPS." THE DEGREE OF POLISH IS MEASURED BY THE BRITISH PORTABLE TESTER (BPT). ANALYSIS OF VARIANCE OF THE PROCESS WAS ALSO PERFORMED. FINDINGS SHOW THAT (1) THE DATA OBTAINED AGREED WELL WITH THE PRECISION STATEMENT FOR THE TEST METHOD AS IT IS GIVEN IN ASTM, (2) THE VARIANCE BETWEEN SAMPLES MAKES UP THE GREATEST PART OF THE TOTAL TO THE EXTENT THAT IT IS ABOUT 4 TIMES THE SUM OF THE REST. THE AVERAGE SKID NUMBER FOR A MATERIAL PLOTTED AGAINST THE CORRESPONDING TRAFFIC MEASURED BY REVOLUTIONS GIVES A HYPERBOLIC CURVE. A COMPUTER PROGRAM GIVES THE BEST FITTING HYPERBOLA FOR EACH SET OF DATA POINTS. CORRELATION COEFFICIENTS ARE AROUND 0.96 OR HIGHER. AT INFINITY, THE COMPUTATIONS GIVE AN INTERCEPT WHICH MAY BE INTERPRETED AS THE ULTIMATE SKID NUMBER THAT WOULD BE PRODUCED IF THE POLISHING PROCESS IS CONTINUOUS FOR AN INFINITE NUMBER OF REVOLUTIONS. THE HYPERBOLIC CURVE APPROACHES THE ASYMTOTE WITH INCREASED TRAFFIC. THE SLOPE GIVES A COMPARATIVE POLISH RATE. IF ALL THESE HOLD UP THROUGHOUT THE INVESTIGATION, THEN THE METHOD DESCRIBED GIVES A CONVENIENT QUANTITATIVE EVALUATION OF ULTIMATE POLISH POTENTIAL OF AN AGGREGATE.
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Supplemental Notes:
- Paper sponsored by Committee on Characteristics of Aggregates and Fillers for Bituminous Construction and presented at the 49th Annual Meeting. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.
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Authors:
- Smith Jr, Nathan L
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Conference:
- 49th Annual Meeting of the Highway Research Board
- Location: Washington District of Columbia, United States
- Date: 1970-1-12 to 1970-1-16
- Publication Date: 1970
Media Info
- Media Type: Digital/other
- Features: Figures;
- Pagination: pp 11-14
- Monograph Title: Aggregates and skid resistance of bituminous pavements
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Serial:
- Highway Research Record
- Issue Number: 341
- Publisher: Highway Research Board
Subject/Index Terms
- TRT Terms: Aggregates; Computer programming; Polished aggregates; Rocks; Size; Skid resistance; Skidding; Slabs; Statistical analysis; Tires; Traffic
- Uncontrolled Terms: Skid number
- Old TRIS Terms: Revolution
- Subject Areas: Data and Information Technology; Geotechnology; Highways; Materials; Operations and Traffic Management; Vehicles and Equipment;
Filing Info
- Accession Number: 00211609
- Record Type: Publication
- Files: TRIS, TRB
- Created Date: Aug 8 1971 12:00AM