BATCHING AND MIXING
September 1, 2003CONCRETE MANUAL5-694.400BATCHING AND MIXING5-694.4005-694.401CHECKING BATCH PLANT OPERATIONCheck to ensure accuracy and dependable operation of the proposed equipment and methods priorto the start of concreting operations and after making any changes in the location or arrangement ofthe batching plant. Plant calibration is the responsibility of the Producer/Contractor.Check the general layout of the plant before the equipment is erected to ensure efficient operationand adequate space for stockpiling and handling materials in compliance with specificationrequirements. Whenever possible, avoid the arrangement and erection of batching plants incongested locations which are not conducive to proper handling of materials. Small stockpilesresult in segregation and non-uniformity of materials and very poor control of the concrete. Once abatching plant is erected in such a location, it is difficult to improve conditions. Experience hasdemonstrated that the most uniform concrete is produced when the batching plant is favored byadequate space for the maintenance of large stockpiles of materials.When draining aggregates at the batch plant site, provide provisions for disposal of drainage waterand for clear-cut separation of drained from undrained materials. Keep materials of differentsources/classes or gradations separated. Sometimes, timber bulkheads are erected to save space inthe Producer’s storage yard. These are satisfactory if built properly.Erect the weighing bins and hoppers on firm foundations to avoid settlement, which might affectthe accuracy of the equipment.At concrete batching sites, check that there is enough material in stockpiles to complete theconcrete pour or the rate of aggregate delivery is sufficient to keep up with the required rate ofconcrete delivery. When using a collecting hopper for handling more than one size aggregate,empty entirely of one size material before placing another size material within. Check to assurethat the conveyor and reflector chute used with the collecting hopper are clear of any accumulatedmaterials. The discharge chute for deflecting the material into the various storage compartmentsmust center over the correct compartment while it is charged with aggregate.5-694.410BATCHING EQUIPMENTCheck batching equipment before the operation begins. Inspect the equipment and review theprocedures the Producer/Contractor will follow during batching. The batching apparatus andprogress must meet specification requirements and produce uniform high quality concrete. Thefollowing information will aid the Inspector in evaluation of the equipment.The batching equipment generally consists of a weigh hopper loaded from overhead bins bygravity, that discharges either into the truck below or onto a belt that goes to the mixer. Weigh thecementitious materials independently of aggregates either on separate scales or in separatecompartments.
September 1, 2003CONCRETE MANUAL5-694.410 (1)The gates controlling charging and discharging of the weigh hopper must tightly close and haveoperating interlocks when producing concrete. See Figure A 5-694.410. The charging device shallprovide the capability of stopping the flow within the specified weighing tolerance and controllingthe rate of flow of the material. The manner of attachment of vibration equipment or other aids tocharging or discharging shall not interfere with the accuracy of the weighing.Figure A 5-694.410The Contractor should avoid overloading the weigh hopper or exceeding the scale capacity. Thebatches shall not overflow the weigh hopper or exceed the scale capacity. Sufficient clearancemust exist above batching hoppers to permit removal of any overload. When fully batched into thehopper, the top of the material must not touch the charging bin above.Cement weigh hoppers must have an access port to facilitate inspection of the interior. Theinstallation of the dust seal between the storage bin and the weighing hopper must not affect theweighing accuracy. The weigh hopper shall have a coned bottom and a vibrator to ensure completedischarge.Prior to mixing, carefully examine the mixer to assure that all requirements of Specification2461.4C2 regarding blade wear, drum speed, timing, etc. are met. The mixer shall produceconcrete at a rate applicable to the size of the pour and the type of operation. Mixers havingcapacities of 0.3 m3 (10 ft3) or more require automatic timers set in accordance with Specification2461.4C2 or 2301.3F prior to any mixing operations. Figure B 5-694.410 shows a mixer dumpinga load.
September 1, 2003CONCRETE MANUALFigure B 5-694.4105-694.410 (2)
September 1, 2003CONCRETE MANUAL5-694.410 (3)Specification 2461.4C2f states that the mixing period begins when the last of the materials enterthe mixer drum and ends when the discharge of the batch begins. Paving mixers, 0.75 m3 (1 yd3)or larger, are required to have a mixing time of 60 seconds. To attain this mixing time, considerother factors such as charging and discharging time in the total operating cycle. Specification2301.3F1 states that when mixing operations are first started on a project, set the timing device toproduce an operating cycle of 75 seconds for single drum and 55 seconds for dual drum mixers.See Figure C 5-694.410 for an example of a single drum mixer and Figure D 5-694.410 for anexample of a dual drum mixer. This operating cycle is the time period between successiveoccurrences at some fixed point in the operation, for example, from bell to bell. Reduce the cycletime if, after the operating constants are determined, the Inspector is certain that each batch willhave a full 60 seconds of mixing time during the operating cycle.Special points to observe regarding batching are the following: For both single and dual-drum mixers, the water should start into the drum in advance of thesolid materials and it should continue to flow into the drum until after all of the solid materialshave entered. The drum must empty of the preceding batch before the solid materials of a new batch enter thedrum. For dual-drum mixers, the first drum must empty completely and the transfer chute must closebefore the solid materials of a new batch enter the drum. Likewise, the second drum mustempty and the discharge chute close before the transfer of the following batch from the firstdrum begins. The number of revolutions at mixing speed shall not exceed 150.Figure C 5-694.410
September 1, 2003CONCRETE MANUAL5-694.411Figure D 5-694.4105-694.411TYPES OF BATCHING EQUIPMENTBatching equipment is designated as Manual, Semi-Automatic, and Automatic as defined below:A. ManualBatching equipment is charged by devices that are actuated manually, with the accuracy of theweighing operation being dependent upon the operator’s visual observation of the scale. Thecharging device is actuated by either hand or by power assists. The weighing accuracy shallcomply with tolerances per Specification 1901 and 2301.3F.B. Semi-AutomaticBatching equipment is charged by devices, which are separately actuated manually for eachmaterial to allow weighing of the material. They are actuated automatically when reaching thedesignated mass (weight) of each material. The weighing accuracy shall comply with tolerancesper Specification 1901 and 2301.3F.C. AutomaticBatching equipment is charged by devices which when actuated by a single starter switch, willautomatically start the weighing operation of all materials consecutively and stop automaticallywhen reaching the designated mass (weight) of each material. Automatic batching equipment shallhave suitable delivery interlocks per Specification 1901 & 2301.3F. See Figure A 5-694.411.
September 1, 2003CONCRETE MANUAL5-694.412Figure A 5-694.4115-694.412REQUIREMENTS FOR PAVING BATCHING EQUIPMENTBatching equipment used in conjunction with paving operations have further requirements inaddition to those specified for other types of concreting operations.The Contractor shall provide: Computerized batching is required. A computer-generated batch ticket showing the target and actual masses (weights) of allcomponents. This shall serve as the materials recorder along with cementitious cut-offs. The water added to the mix by an electronic meter, approved by the Engineer, which recordsthe amount of total water, including temper water, as part of each batch ticket.5-694.430CHECKING BATCHING AND MIXING EQUIPMENTThere are two items of equipment to closely observe at all times. These are the scales used forweighing the batch materials and the water measuring equipment. Check to make sure that thisequipment meets accuracy requirements before the work begins. An approved scale company mustcheck and calibrate the scales that have not received an approved inspection within six monthsprior to starting production. Thereafter, scales are checked and calibrated once each year.Additional calibrations are made at three-month intervals using the procedure described in 5694.431 and 5-694.433. The Producer’s Plant Personnel may perform these if observed by anAgency Inspector. If more than 45 days have elapsed since the full-scale check by a scalecompany, the first such check is made before operations begin. Spot-check the scale calibrations atleast once each month. The Producer should check the scales for zero balance and the
September 1, 2003CONCRETE MANUAL5-694.430effectiveness of the interlocking controls for the cement and aggregates at least twice each day andfor sensitivity at least once each day. The Producer shall report defective controls in the plantdiary.The most accurate weighing systems include load cells. A load cell uses a strain gauge to measurethe direct stress that is introduced into a metal element when it is subjected to a tensile orcompressive force.Load cells are attached to digital displays for easy reading and zeroing. They also featureprogrammable high/low set points. Signals for the load cells are sent electronically to thecomputer for accurate documentation. See Figure A 5-694.430.Figure A 5-694.430When weighing or measuring equipment is moved from one setup to another, theProducer/Contractor shall completely recalibrate it after erection at the new site. Erratic andinaccurate operation of the measuring equipment due to maladjustment or damage may result fromimpact and shock during the move.Sluggishness of the working parts or a marked change in the level of material in the weighinghoppers may indicate inaccurate operation of the scales. Providing the batch composition andother conditions remain constant, the water setting at the mixer should also remain relativelyconstant. A decided change in the required mixer setting following an extended period of uniformoperation indicates that something is wrong with the equipment and that an immediate check isrequired. In such cases, a thorough checking of the equipment is required in addition to recalibration. Investigate the cause of the trouble and eliminate it.
September 1, 2003CONCRETE MANUAL5-694.431 (1)In order to determine whether or not the concrete meets specification requirements for cementcontent, water-cement ratio, etc. the Inspector must know the exact amount of materials used inmixing the concrete.The equipment used for proportioning the various materials in the batching operations shall complywith Specifications 1901.8 and 2461.4B. Specification 2461.4D for ready-mix work and 2301.3Ffor concrete paving projects also apply. The Producer/Contractor is required to furnish personneland accessories needed to check the accuracy of the equipment. An Agency Monitor records theresults, while offering other reasonable assistance to facilitate this calibration. The equipment mustmeet accuracy and sensitivity requirements within the specified tolerances at all times.If water measuring equipment is inactive for any extended period of time, as over winter, theProducer/Contractor should dismantle and thoroughly clean and adjust before it is calibrated.Problems are frequently encountered with this type of equipment due to formation of scale andrust. This condition is aggravated considerably by long periods of inactivity or storage. Thepresence of scale or other foreign material in the system is invariably indicated by erratic operation.Erratic or inaccurate operation may also result from wear or maladjustment of the equipment, leakyvalves, etc. When such inaccurate operation is encountered, immediate correction is requiredbefore mixing is allowed to start.5-694.431CALIBRATING WEIGHING EQUIPMENTWhen a scale servicing company performs the required calibration they should generally follow theprocedures outlined below:A. Visual Inspection Prior to TestClearance around hopper and lever systemDust curtain for slack - freedomBalance of scaleCorrect problems noted above, before proceeding onB. Test Procedure1. Balance Indicator: Check for repeatability. Note the hangers, materials used to hold weights,and the correction weights are included in the balance.2. Sensitiveness: Check on non-automatic indicating scales. Twice the value of the minimumgraduated interval on the beam allowed.3. Fractional Poise: Check to capacity by 50 kg (100 lb.) increments; tolerance 0.5%.4. Balance Check: Remove test weights and recheck balance device. This action should notchange balance by more than one of the minimum graduations (plus or minus).5. Empty Test: Apply test weight to empty scale, minimum load of 500 kg (1000 lb.), 1000 kg(2000 lb.) desirable (or to capacity of device, whichever is greater); tolerance 0.5%.6. Balance Check: Remove test weights and re-check balance. The device should not changebalance by more than one of the minimum graduations (plus or minus).7. Half Normal Batch Capacity Test: Fill the hopper to about one-half the capacity of the devicewith batching materials, take reading, then apply test weights. Tolerance is applied only to the
September 1, 20038.9.10.11.CONCRETE MANUAL5-694.431 (2)total of the test weights used; tolerance 0.5%.Balance Check: Remove test weights and recheck reading with materials. Reading should notchange by more than one of the minimum graduations (plus or minus).Full Normal Batch Capacity Test: Fill the hopper with batching material to as near capacity thatwill still allow the test weights to be applied without exceeding the capacity and take reading.The test weights tolerance of 0.5% is applied only to the total of the test weights used.Balance Check: Remove test weights and recheck reading with materials. Reading should notchange by more than one of the minimum graduations (plus or minus).Electronic Indicators: Check for environmental factors such as R.F.I. interference from otherelectronic elements in the environment. Interference must not affect the device by more thantwo of the minimum graduations (plus or minus).C. Spot Check ProcedureThe usual procedure in making a spot check is to assure that the equipment is generally in goodoperating condition. The knife-edges or other working parts of the equipment shall have nobinding or cramping. The Producer must have a sufficient number of test weights. Fully load thestorage hoppers prior to the spot check.The first step is to balance the scale at a load of zero with the weighing hopper clean and empty.On single beam scales, obtain the zero balance with the adjustable counter weight provided. Formultiple beam scales, obtain zero balance first with the tare beam and then with each and all of theweight beams free to act with the tare beam. To prevent use with other beams, securely fasten in azero position any of the multiple beams actually not required in the weighing operations whenmultiple beam scales are used. After zero balance is satisfied, one or more of the test weights isapplied by means of a suitable hanger furnished by the Producer/Contractor. Knowing the mass(weight) of the hanger accessories is required because it is included as part of the applied load.If the scale is to operate with a normal working load of about 250 kg (500 lb.), apply the testweights in 50 kg (100 lb.) increments until the calibration is carried up to 350 kg (700 or 800 lb.),including the mass (weight) of the hanger. For larger scales, fill the bins to within approximately100 kg (200 lb.) of the expected operating point, then test weights in 50 kg (100 lb.) increments areapplied until a point approximately 100 kg (200 lb.) over the operating point is reached. Each timea weight increment is applied, balance the scales and record a reading opposite the known appliedload.While carrying the spot check over the expected operating range, check the sensitivity of theequipment by temporarily applying an additional load equivalent to 0.2% of the load at that time.The additional load should throw the equipment out of balance.If the equipment fails to meet requirements in any respect, a report should indicate the discrepancy.After the scales are repaired or otherwise rendered satisfactory, re-calibrate the scales and send acopy of the reports to the Project Engineer to document that the equipment complies with thespecifications. A sample of the Test of Weighing Equipment (Form 2124) is shown in Figure A 5694.717.
September 1, 2003CONCRETE MANUAL5-694.432For paving projects over 750 m3 (1000 yd3), check the various interlocking devices to assure properfunction. Check that the hopper inlet gate and the discharge gate cannot open at the same time. Ifone gate is open, the other gate is interlocked in the closed position. The cementitious scales shallhave these same features, but in addition, the discharge gate is not capable of opening until thescale is in balance at full load. Once the discharge gate is open, it is not capable of closing until thetare beam or dial comes back to zero balance. The discharge gate of the cementitious hopper isalways locked in the closed position during the weighing operation when the cementitious in theweighing hopper is outside the specified tolerance of 1%. Check this feature during the spot checkby resetting the scale at balanced loads by an amount equivalent to (both plus and minus) slightlymore than the 1% tolerance in mass (weight) permitted. If the discharge gate can open, thedischarge-locking device is not functioning properly.Do not use equipment for paving which does not have the required interlocking devices forcontrolling the batching operations as provided in Specification 2301.3F4.5-694.432AUTHORIZED SERVICE COMPANIES FOR SCALE CALIBRATIONSA list of authorized service companies for scale calibrations is available on the Mn/DOTConcrete Engineering Unit website at .asp.5-694.433CALIBRATING WATER MEASURING EQUIPMENTCalibrate and spot check water weighing equipment in accordance with the following sections.Carefully calibrate water-measuring equipment before mixing operations begin, but after the mixeris in its operating position. See Figure A 5-694.433 for an example of a water meter and a waterscale.Figure A 5-694.433Measure the mixing water on approved scales or by volume using an approved water-meteringdevice. For approval, the water meter shall comply with the following:1. It shall have a discharge indicator capable of setting to within 5 L (1 gal.) of a predeterminedamount.
September 1, 2003CONCRETE MANUAL5-694.4342. It shall have a positive automatic shutoff valve that stops the flow of water when the indicatedamount of water is delivered.3. It shall operate within a maximum delivery tolerance of 1% of the required water setting at thetime of batching.4. It shall bear an approved inspection seal displaying the date of the previous calibration andadjustment within 6 months of the date of use.Unless evidence is furnished indicating that the water meter was calibrated and adjusted within theprevious six months by an authorized service agency as listed on the Mn/DOT ConcreteEngineering Unit website, recalibrate and adjust prior to use in accor
material to allow weighing of the material. They are actuated automatically when reaching the designated m ass (weight) of each material. The we ighing accuracy shall co mply with tolerances per Specification 1901 and 2301.3F. C. Automatic Batching equipment is charged by dev
mechanical mixing (rotating, vibrating) hydraulic mixing pneumatic mixing pipeline mixing (turbulent flow, static mixer) Method of mixing fluids A –mechanical mixing using turbines B –mechanical mixing using blade impellers C –hydraulic mixing D –pneumatic mixing with stationary inputs
1.1. Inventorying Concrete Materials 1.2. Storing Concrete Materials 1.3. Water-Cement Ratio 1.4. Concrete Batching 1.5. Stationary Mixing and Delivery 1.6. Ready Mixing and Delivery 1.7. Hot Weather Batching 1.8. Cold Weather Batching 2. Concrete Paving Site Preparation and Construction 2.1. Preparing the Subgrade and Subbase 2.2. Setting .
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Fibo has a batching plant to deliver the concrete on demand. The Fibo solution can be far more economical than traditional batching plants. The concrete is high quality with weight batching, and with Fibo LINK every batch is stored in the cloud. The data can then be printed out as delivery and conformity documents for every batch. 1. Remote .
indicators and alarms are off. The unit is ready for batching or configuration. BATCHING: When SET/RDY is displayed, entering a batch quantity via the numeric keypad buttons will cause the displayed SET value to change and flash. Then, pressing the SET button locks in the new value, or pressing CANCEL reverts the value to its
circumstances in the production system are complex and various, such as multi-site plant [2], multiple products [3,4], deteriorating jobs [5], limited batch size [6], parallel batching [7], serial batching [8,9], and so on. There is not any single model that is the best to solve all problems in batching process.
CONCRETE BATCHING PLANT - LOT 2, 277-279 COLLIER ROAD, BAYSWATER Summary Ransberg Pty Ltd WA Premix proposes to construct a "wet-mix" concrete batching plant with an average production capacity of 135 m3/day of ready-mixed concrete (the proposal), located on Lot 2, 277-279 Collier Road, Bayswater (Attachment 1 and 2).
Manual Batching 101 The materials to be used in the batch are gathered or they may already be available to the operator at the batching station. The operator begins the batch process, adds materials following the onscreen prompts.- The finished product is moved to storage and Batch reports are produced to document what the batch contains.
