HOW AGGREGATE PARTICLE SHAPE INFLUENCES CONCRETE MIXING WATER REQUIREMENT AND STRENGTH

VARIATIONS IN MIXING WATER REQUIREMENT AND STRENGTH WERE MEASURED IN 5-1/2-SACK, 3 TO 4-IN. SLUMP CONCRETE CONTAINING AGGREGATES FROM NINE SOURCES, ALL OF WHICH WERE GRADED TO A 1-IN. MAXIMUM SIZE. TESTS FOR THE VOID CONTENT OF BULK AGGREGATE AND THE RATE OF FLOW THROUGH AN ORIFICE PROVIDED EXCELLENT EMPIRICAL MEASUREMENTS INDIRECTLY RELATED TO PARTICLE SHAPE CHARACTERISTICS USED TO EXPLAIN THESE VARIATIONS. WITH SELECTION OF SUITABLE EQUIPMENT AND GRADINGS, THE TESTS WERE APPLICABLE TO EITHER FINE OR COARSE AGGREGATE. VOID CONTENT OF AGGREGATE WAS THE MOST SATISFACTORY AND CONVENIENT MEASURE OF SHAPE CHARACTERISTICS. CONTRARY TO CURRENT CONCEPTS, DIFFERENT COMMERCIALLY PRODUCED FINE AGGREGATES HAD A MUCH GREATER EFFECT ON CONCRETE MIXING WATER DEMAND AND STRENGTH THAN THEIR COARSE COMPANIONS. A 4 PERCENT INCREASE IN FINE AGGREGATE VOIDS CAUSED A 3 GAL PER CUBIC YARD INCREASE IN WATER DEMAND, WHILE A SIMILAR INCREASE IN COARSE AGGREGATE VOIDS PRODUCED AN INCREASE FROM 1 TO 1-1/2 GAL. FINE AGGREGATES INFLUENCED COMPRESSIVE STRENGTH ALMOST EXCLUSIVELY THROUGH THEIR EFFECT ON MIXING WATER. HOWEVER, OTHER FEATURES ALSO HAD SOME EFFECT. THE 3-GAL INCREASE IN MIXING WATER LOWERED COMPRESSIVE STRENGTH ROUGHLY 1000 PSI. FOR COARSE AGGREGATES, THE SITUATION WAS QUITE DIFFERENT. ALTHOUGH THE SHAPE CHARACTERISTICS DETERMINED MIXING WATER REQUIREMENTS, THIS EXPLAINED ONLY A PART OF THE VARIATION IN COMPRESSIVE STRENGTH. OTHER FACTORS SUCH AS ELASTICITY, MINERALOGY, OR BOND WITH CEMENT PASTE WERE PROBABLY AS IMPORTANT AS PARTICLE SHAPE IN THIS RESPECT. A SIMILAR SITUATION APPEARED TO BE THE CASE FOR FLEXURAL STRENGTH, WHERE RELATIONSHIPS BETWEEN MIXING WATER AND SHAPE FEATURES OF EITHER FINE OR COARSE AGGREGATE WERE LESS DEFINED. /JM/

• Supplemental Notes:
  • Vol 2, No 4, PP843-865, 9 FIG, 7 TAB, 9 REF, 1 APP
• Authors:
  • Wills, M H
• Publication Date: 1967-12

Media Info

• Serial:
  • Journal of Materials
  • Publisher: American Society for Testing and Materials (ASTM)

Subject/Index Terms

• TRT Terms: Aggregates; Aggregates by shape and surface texture; Air voids; Bonds; Coarse aggregates; Compressive strength; Concrete; Elasticity (Mechanics); Fine aggregates; Flexural strength; Mineralogy; Mix design; Particles; Shape; Water consumption
• Uncontrolled Terms: Aggregate shape
• Old TRIS Terms: Air voids content; Particle shapes; Water requirements
• Subject Areas: Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00217756
• Record Type: Publication
• Files: TRIS
• Created Date: Sep 9 1994 12:00AM