READYMIX INDUSTRY There are two main components in asphalt concrete: 1) the asphalt cement, or glue, and 2) the aggregates.

READY MIX INDUSTRY (BASED ON ASTM C94) BASIS OF PURCHASE BATCHING MIXING TRANSPORTING

BASIS OF PURCHASE: IN ABSENCE OF A DESIGNATED SPECIFICATION, A PURCHASER MUST REQUEST: DESIGNATED SIZE OR SIZES OF AGGREGATE SLUMP REQUIRED AIR ENTRAINMENT – AIR TEST AT PLACEMENT THE CHOICE OF OPTION A,B,OR C FOR PROPORTIONING THE MIX DRY UNIT WEIGHT FOR YIELD TEST (FOR STRUCTURAL LIGHTWEIGHT CONCRETE)

BASIS OF PURCHASE: OPTION A OR C (ASTM C94) MANUFACTURER ASSUMES FULL RESPONSIBILITY FOR SELECTING THE MIX PROPORTIONS PURCHASE HAS TO DECIDE ON THE 28 DAY STRENGTH OPTION B (IN ADDITION) PURCHASE MUST SPECIFY MIN. ALLOWABLE CEMENT CONTENT TO BE USED IN THE MIX DESIGN DESIGNATED SIZE OR SIZES OF AGGREGATE SLUMP REQUIRED AIR ENTRAINMENT – AIR TEST AT PLACEMENT OVEN DRY WEIGHT FOR YIELD TEST (UNIT DRY WT.)

BASIS OF PURCHASE: OPTION B continued (ASTM C94) PURCHASER ASSUMING THE RESPONSIBILITY FOR PROPORTIONING THE CONCRETE MIXTURE SPECIFY CEMENT CONTENT PER CY SPECIFY WATER CONTENT PER CY THE TYPE AND DOSAGE FOR ALL THE ADMIXTURE SIZE OF AGGREGATE AND SLUMP REQUIRED

BATCHING MEASURED BY WEIGHT CEMENT FINE AND COARSE AGGREGATE FLYASH AND POZZOLANS MEASURED BY WEIGHT AND VOLUME WATER ADMIXTURE

BATCHING BATCH PLANTS HOPPER CAN WEIGH CUMULATIVELY OR INDIVIDUALLY AGGREGATES WATER CONTENT HAS TO BE DETERMINED TOTAL MOISTURE =WATER CONTENT TOTAL WET WT. = DRY AGG + WT. OF MOISTURE POWDERED ADMIXTURE ARE MEASURED BY WEIGHT LIQUID ADMIXTURE ARE MEASURED BY WEIGHT OR VOLUME

BATCHING BATCH PLANTS WEIGH BATCHER TRUCK MIXERS COARSE AGG SHOULD BE DISCHARGED BEFORE OTHER INGREDIENTS ALL SCALES HAVE TO BE CALIBRATED

SHOULD NOT EXCEED 63% OF THE DRUM VOLUME MIXING MIXERS AND AGITATORS STATIONARY MIXERS I.E. TILTING DRUM MIXER DISCHARGES WHILE TILTING THE MIXING, IN OPPOSE TO A NON-TILTING MIXER TRUCK MIXERS (AVG CAPACITY IS 8-9 YDS) Note the cliché – “Give me the whole nine yards!” FRONT DISCHARGE REAR DISCHARGE SHOULD NOT EXCEED 63% OF THE DRUM VOLUME AGITATORS (MAYBE TRUCK MIXERS OR AGITATORS) MUST BE ABLE TO DELIVER THOROUGHLY MIX CONCRETE TO THE JOBSITE SHOULD NOT EXCEED 80% OF THE DRUM VOLUME

MIXING UNIFORMITY TEST SAMPLES MUST HAVE THE SAME: SLUMP- SLUMP TEST UNIT WT. – YIELD TEST AIR CONTENT – AIR METER OR AIR TEST STRENGTH – COMPRESSION TEST

MIXING MIXING AND DELIVERY CENTRAL MIX – CONCRETE THAT IS MIXED COMPLETELY IN A STATIONARY MIXER SHRINK MIX- CONCRETE THAT IS FIRST PARTIALLY MIXED IN A STATIONARY MIXER, AND THEN MIXED COMPLETELY IN A TRUCK MIXER TRUCK MIX –CONCRETE THAT IS COMPLETELY MIXED IN A TRUCK MIXER, 70-100 REVOLUTIONS AT THE MIXING SPEED

MIXING NON-AGITATING MIXING REQUIRES SLUMP TEST USED FOR SHORTER HAULS

TRANSPORTING JOB SITE CONTROL NO ADDITIONAL WATER CAN BE ADDED EXCEPT IF SLUMP DOES NOT REACH SPECIFIED SPEC. AND THE WATER CEMENT RATIO IS NOT INCREASED SHRINK MIX- CONCRETE THAT IS FIRST PARTIALLY MIXED IN A STATIONARY MIXER, AND THEN MIXED COMPLETELY IN A TRUCK MIXER TRUCK MIX –CONCRETE THAT IS COMPLETELY MIXED IN A TRUCK MIXER, 70-100 REVOLUTIONS AT THE MIXING SPEED

TRANSPORTING INSPECTION AT THE JOBSITE CONCRETE MUST BE TESTED FOR SLUMP, AIR CONTENT, AND STRENGTH ACI CERTIFICATION FOR CONCRETE FIELD TESTING TECHNICIAN – GRADE LEVEL I ONE STRENGTH TEST IS PREPARED FOR EVERY 150 CY AND AT LEAST ONE FOR EACH DAY THE CONCRETE IS DELIVERED OR FOR EACH CLASS OF CONCRETE (I.E. CLASS A,B OR C ) AT LEAST THREE STRENGTH TEST SHOULD BE MADE AND AVERAGE I.E. FOR A 4000 PSI CONCRETE THREE SAMPLES - 4400 3600 4300 GIVES AN AVERAGE 4100 AND NONE OF THEM ARE LESS THAN 500 PSI BELOW THE SPECIFY STRENGTH