AIR VOID SYSTEMS IN READY-MIXED CONCRETE

CONCRETE PRODUCED AT A COMMERCIAL BATCH PLANT IN TRUCK MIXERS WAS SUBJECTED TO EXTENSIVE TESTING FOR THE PROPERTIES OF THE ENTRAINED AIR SYSTEM, FROST RESISTANCE AND COMPRESSIVE STRENGTH. SIXTY, 6-YARD BATCHES OF SILICEOUS AGGREGATE CONCRETE WERE INCLUDED IN THE PROGRAM. THE VARIATIONS IN THE PROPERTIES UNDER INVESTIGATION COULD BE ATTRIBUTED TO DIFFERENT CHEMICAL TYPES OF AIR-ENTRAINING AGENTS AND RETARDERS AND TO DIFFERENT MIXING METHODS. THE FOLLOWING INDICATORS OF THE QUALITY OF THE ENTRAINED AIR SYSTEM WERE USED FOR COMPARISON: (1) POWERS' SPACING FACTOR, (2) PHILLEO SPACING FACTOR, (3) SPACING FACTOR FROM THE VOID SPACING INDICATOR (VSI), AND (4) SPECIFIC SURFACE. THE VSI IS A NEW TEST FOR THE QUALITY OF THE ENTRAINED AIR SYSTEM IN PLASTIC CONCRETE. IT IS SHOWN TO BE A VALUABLE INDICATOR OF THE FROST RESISTANCE OF CONCRETE. A SECOND SERIES OF CONCRETE BATCHES WAS MIXED IN THE LABORATORY. THESE BATCHES WERE PROPORTIONED USING THE SAME AGGREGATES, CEMENT AND ADMIXTURES AS THE READY MIX CONCRETE. THE MAIN DIFFERENCES WERE THE SIZE OF BATCH, THE MIXER AND THE BATCH TEMPERATURES (AVERAGE 74 DEGREES F COMPARED TO 89 DEGREES F). A FIELD SURVEY OF BRIDGE DECKS AND CONCRETE POURS IN VARIOUS PARTS OF THE STATE OF TEXAS IS INCLUDED. /AUTHOR/