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ADMIXTURES

WHAT IS BEING USED AND THE EQUIPMENT FOR CONCRETE PAVEMENTS

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ADMIXTURESAir-Entraining AgentsWater ReducersRetarders/Hydration StabilizersAcceleratorsVMA?

WCPA 2018 Conference

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ADMIX EQUIPMENTBottle/Meter Direct SystemsElectronic/Pneumatic ControlsComputer InterfaceDispensing


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THE BATCH SEQUENCEPutting it all togetherPushing the start buttonScalingThe Discharge Sequence


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SHES-FASTRACK MIXESMethods to Achieve Opening Strengths in >8 HoursMarrying Technology and TechniqueMix ComponentsCommonly used design parametersChemical ComponentsPutting it all togetherMix ManagementTestingOnce its downPredicting strength gain


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AIR ENTRAINING AGENTSMany different materials….Vinsol Resins & Rosins, Tall Oils, Vegetable oil acids, Synthetic Detergents…………Solid ContentCost?CompatibilityAir Void SystemResistance to Vibration


AIR IN CONCRETE

Entrained: intentionally stabilizing the air bubbles – become miniscule hollow spheres anchored below the surface of the concrete

ENTRAPPED AIREntrapped vs. EntrainedEntrapped: coarse void spaces, randomly distributed – cannot be counted on for durability but does provide some internal relief from freeze – thawEntrained- miniscule, shell- like bubbles that anchor below the surface that provide the voids for the relief from the tensile stresses of expansive water

THE ESSENTIALSWater-hard water or water w organics.W/C Ratio and slump may not be the same.Aggregate, Quality AND MoistureCementitious MaterialsSequencingMixing





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WATER REDUCERSTypically Classified into 3 CategoriesType A…………………Minimum 5% = 1.5gal/CYMid Range…………….6%-12% = 1.5 to 3gal/CYType F (Supers)……...<13% = +3gal/CYMeat and Potatoes ASTM C494 Type A A/D (Lignosulphonates)Typical Dosage RatesDispersionFinishabilityCo-Pilot to Air-Entraining Agent



RETARDERSRetarders are used to slow time of initial set by one hour or more

Should be used when additional time is required for placing and finishing concrete or when temperatures make it necessary

Dosage Rates

HYDRATION STABILIZERSHydration Stabilizers are used to slow time of set as well as the RATE of set.Can be used for extended haul times or to slow initial set and rate of set under normal and/or warm weather conditionsLess tendency to “snap” set. Aids in slump retention.Dosage rates tend to be linear than exponential.May or may not require use of Type A

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VISCOSITY MODIFIERSOriginally used for underwater/SCCIncreases Cohesiveness Usage in exterior concretesHarsh Coarse AggregatesManufactured SandsMaintains integral moistureFinishability “Buttery Feel”


VMA BENEFITS








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CONCRETE BATCH SEQUENCINGWeighing of AggregatesWeighing of Cement/Ash/SlagWeighing of Water Weighing of Admixtures (Bottles)



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THE BIRTH OF CONCRETEHead WaterAir-Entraining AgentWater ReducerAggregateCementTail WaterSlump Water

All in 60-90 seconds







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SHES-FASTRACK MIXESTypically “Full” 9-Bag Cement Content (846lbs)Type I/II or Type III CementsLow W/C Ratio >0.35 is common. Air-EntrainedAggregatesType F Water Reducer-Superplasticizer (Polycarboxylates)Retarders/Hydration StabilizersNon-Chloride AcceleratorCalcium Chloride


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SHES-FASTRACK MIXESSOME ASSEMBLY REQUIREDBatch Sequence Subject to ChangeLarge Volume of CementHead to Tail WaterCharging AggregatesMultiple AdmixturesRetarders/Hydration Stabilizers-Why oh Why?Non-Chloride AcceleratorCalcium Chloride


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SHES-FASTRACK MIXESLIGHT THE FUSE AND RUN

Ambient Conditions Rule-Torpedo AnalogySize of Patches=Size of BatchesLength of HaulWater ReductionSlump RetentionAcceleration up frontSlump & Air in the yardAccelerator on siteCalcium Chloride-Flake or Liquid.



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SHES-FASTRACK MIXESARRIVAL AT P.O.P.

Wake it up.Check Slump Visually AND with the Meter.Addition of AcceleratorMixingFirst LookTestingTime is of the EssenceSplitting up the TroopsTest SamplesCoveringCuring






Questions?

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