Batch plant maintenance

BATCH PLANT
MAINTENANCE
Maintenance PLAN of Concrete Batching Plant
CCCC-LBG / DAD November 14

REFERENCES
• ACI 117 SPECIFICATION FOR TOLERANCES FOR CONCRETE CONSTRUCTION
AND MATERIALS
• ACI 301 SPECIFICATIONS FOR STRUCTURAL CONCRETE
• ACI 304R GUIDE FOR MEASURING, MIXING, TRANSPORTING, AND PLACING
CONCRETE
• ACI 311.1R ACI MANUAL OF CONCRETE INSPECTION
• ACI 311.5R PLANT INSPECTION OF READY-MIXED CONCRETE
• ASTM C 94 STANDARD SPECIFICATION FOR READY-MIXED CONCRETE
• EPA US ENVIRONMENTAL PROTECTION AGENCY
• NRMCA NATIONAL READY MIXED CONCRETE ASSOCIATION

ACI 117 SPECIFICATION FOR
TOLERANCES FOR CONCRETE
CONSTRUCTION AND MATERIALS
2.4a CEMENTITIOUS
MATERIALS
Concrete batching tolerances
Less than 30% of scale capacity
–0 to +4% of the required mass
30% of scale capacity or greater
±1% of required mass
2.4b WATER &
ADMIXTURES
Total water content (measured by
weight or volume)
±3% of the required amount
Added water or ice, and free water
on aggregates
±1% of the total water content
Admixtures
±3% of the required amount
2.4c AGGREGATES
Individual material batching
±2% of the required mass

Supplementary
Cementing Materials
By Rafat Siddique,
Mohammad Iqbal Khan

ACI 301-
SPECIFICATIONS FOR STRUCTURAL
CONCRETE
Art. 1.6.3.2.c
Obtain production samples of
materials at plants or stockpiles during
the course of the Work and test for
compliance with Contract
Documents.
Art. 13.1.2.1.h
Plant quality control—
Submit certification of precast
concrete plants in accordance with
the Precast/ Prestressed Concrete
Institute (PCI) Plant Certification
program.
Alternatively, submit manufacturing
procedures and a quality control and
testing program to Architect/Engineer
for review and acceptance. Submit
evidence of plant certification or
documentation of manufacturing
procedures and quality control
program.
Art. 13.2.15.1
Specify if PCI plant certification and
testing and inspection program is not
required. Documentation of
certification of plant and personnel.

SUB 01 45 00-070 ITP CONCRETE
PRODUCTION ITP-SUB-GEN-G-PAS-
05009_A-CCCC-
LBG / DAD November 14

ACI 304R
- GUIDE FOR MEASURING, MIXING,
TRANSPORTING, AND PLACING
CONCRETE
• 3.5—Water and ice measurement
• 3.5.1 Batching equipment: Equipment
and methods used should be capable
of routine measurement within the 1%
tolerance. All equipment for water
measurement should be designed for
easy calibration so that accuracy can
be quickly verified.
• 3.5.2 Aggregate moisture determination
and compensation: Moisture meters
should be recalibrated monthly or
whenever the slump of the concrete
produced is inconsistent.
• 4.9—Maintenance
• Mixers should be properly maintained
to prevent mortar and dry material
leakage. Inner mixer surfaces should be
kept clean and worn blades should be
replaced. Mixers not meeting the
performance tests referenced in
Section 4.8 should be taken out of
service until necessary maintenance
and repair corrects their deficient
performance.

ACI 311.1R
ACI MANUAL OF CONCRETE
INSPECTION
7. BATCHING AND MIXING

ACI 311.5R
PLANT INSPECTION OF
READY-MIXED CONCRETE
1.3—Inspector duties
1.3.1 To determine required inspections,
the inspector should review and fully
understand the project specifications,
plans, and other project documents.
The inspector should observe that the
facilities, scales, and truck mixers meet
the specified project requirements. The
provisions of the following documents
should normally be incorporated in the
project specification:
ACI 301; ASTM C 94/C 94M;
Plant qualification in accordance with
the (NRMCA) checklist for certification of
ready-mixed concrete production
facilities; and Local agency
specifications.
1.3.2 Inspectors should conduct
activities in accordance with all
safety policies, health standards, and
safe work practices in effect at the
job site.
1.3.3 The inspector should verify proper
storage of all materials on a daily basis.
All storage areas should be clean and
free of contamination.
Cementitious materials should be stored
in weatherproof silos or similar structures.
Aggregate storage areas should provide
for separation and free draining of
stockpiled materials.
Storage areas should be equipped with
water spray systems for maintaining
aggregates in a saturated condition.
Means for protecting and preventing
freezing of aggregates during winter
production should also be provided.
Admixture storage areas should be
suitably insulated.

ACI 311.5R
PLANT INSPECTION OF
1.3.4 All tests and inspections should
be conducted at the frequencies
required by the project specifications
in a manner that does not interfere
unnecessarily with the manufacture
and delivery of the concrete.
1.3.4 During the first batch being
shipped to the project under the
inspector’s jurisdiction, the inspector
should be present at the batching
console to verify that the specified
type and amount of materials,
conforming to the approved design
mixture proportions, are batched and
delivered to the mixer.
1.3.4 If the operation is automated
and recorded, the inspector should
make observations as often as
possible, preferably on a continuous
basis, but at least once per hour.
If the batching operation is manual,
the inspector should be present at
the batching console during all
batching. The inspector should verify
that quantities of materials for each
batch fall within the tolerances set
forth by the project specifications.

SECTION 34 90 08:
• 2.4.3.1 Materials shall be measured by weighing, except as otherwise specified in the
Contract documents or where other methods are specifically authorized. The apparatus
provided for weighing the aggregates and cement shall be suitably designed and
constructed for this purpose.
• Each size of aggregate and the cement shall be weighed separately.
• The accuracy of all weighing devices shall be such that successive quantities can be
measured to within one percent of the desired amount.
• Cement in standard packages need not be weighed but bulk cement shall be weighed. The
mixing water shall be measured by volume or by weight (mass). The accuracy of measuring
the water shall be within a range of error of not over one percent.
• All measuring devices shall be subject to approval and shall be tested, at the Contractor's
expense, when deemed necessary by the Contracting Officer.
• 2.4.3.2 When volumetric measurements are authorized for projects, the weight (mass)
proportions shall be converted to equivalent volumetric proportions.
• In such cases, suitable allowance shall be made for variations in the moisture condition of the
aggregates, including the bulking effect in the fine aggregate.
• When sacked cement is used, the quantities of aggregates for each batch shall be exactly
sufficient for one or more full sacks of cement and no batch requiring fractional sacks of
cement will be permitted.
• 2.4.4.1 Batching: (c) Batching equipment and scales shall meet the requirements for
measurement and accuracy in ASTM C94

ACI 311.5R
PLANT INSPECTION OF
1.3.5 The inspector should verify that
coarse- and fine aggregate gradation
tests are being performed in
accordance with ASTM C 136 and that
the results meet the project
requirements. If deviation occurs, batch
plant personnel and the client should be
notified immediately, or previously
authorized action should be taken.
aggregate moisture contents are
properly determined in accordance with
ASTM C 566, and that the batch
quantities of materials are adjusted to
compensate for free moisture in the
aggregates.
If aggregate moisture contents are
being measured by rapid methods, daily
correlation tests following ASTM C 566
should be conducted.
1.3.7 The inspector should determine
that the trucks are in good operating
condition and not loaded beyond
their rated capacities for mixing and
agitation.
Trucks should also be inspected
(safety regulations regarding
confined spaces should be followed,
if applicable) for blade wear, build-up
of concrete on the blades, and for
proper mixing speed as described in
the NRMCA Quality Control Manual.
Truck mixers should be equipped with
counters or similar means to enable
verification of the number of
revolutions applied to the drum.
the scales and other measurement
systems have been properly
calibrated within the time period
specified by the project specifications
or referenced documents

ACI 311.5R
PLANT INSPECTION OF
1.3.9 The capability of the production
facility to produce concrete within
the temperature limits of the project
specification should also be
evaluated and verified.
In hot weather, this generally requires
a system for spraying and cooling
aggregates and a system for
efficiently weighing and delivering
crushed ice to the mixer in the range
of 40 to 100 lb per yd3 (18 to 45 kg
per m3).
1.3.10 For each batch of concrete
the inspector should verify that the
concrete plant is furnishing to the
purchaser a delivery ticket
conforming to ASTM C 94/C 94M. A
place should be provided on the
ticket to reflect the following
information:
• Name of the concrete plant;
• Serial number of the ticket;
• Date;
• Truck number;
• Name of the purchaser;
• Project designation (name and location);
• Class or designation of concrete; Amount
of concrete batched;
• Time batched;
• The amount of water withheld during
batching, if any, and the admixtures that
may be added at the jobsite; and
• Any additional information required by
the purchaser or the project specification.

ACI 311.5R
PLANT INSPECTION OF
1.4—Reports
1.4.1 The inspector should sign the
delivery ticket, issue an inspection
report, or supply other evidence that
the concrete batching has been
inspected.
1.4.2 The inspector should issue a daily
inspection report showing all test
results and documenting observations
made during the day. Deficiencies
and to whom they were reported
should be clearly identified.
The ACI Manual of Concrete
Inspection (SP-2) contains guidance
on reporting and samples of reports.

ASTM C 94-
STANDARD SPECIFICATION FOR
Art. 6 & 9
6.6 A certified copy of all proportions
as established in Options A, B, or C
shall be on file at the batch plant.
9.3 Mixing water shall consist of water
added to the batch. The added
water shall be measured by weight or
volume to an accuracy of 1 % of the
required total mixing water.
9.4 Liquid chemical admixtures shall
be batched by mass or volume.
Admixtures measured by either mass
or volume, shall be batched with an
accuracy of ±3 % of the total amount
required.
Art. 10
10.1 Means of control shall be
provided so that, as the quantity
desired in the weighing hopper is
approached, the material shall be
shut off with precision. Weighing
hoppers shall be constructed so as to
eliminate accumulations of tare
materials and to discharge fully.
10.3 Scales shall be considered
accurate when at least one static
load test within each quarter of the
scale capacity can be shown to be
within ±0.15 % of the total capacity of
the scale or 0.4 % of the net applied
load, whichever is greater.
NOTE 11—The batching accuracy
limit of 0.3 % of scale capacity
establishes a reasonable minimum
weighing tolerance limit that is
independent of the quantity of
material being weighed. It generally
governs for smaller batch quantities
weighed in weigh batchers (scales).
NOTE 13—The scale accuracy
limitations of the National Ready
Mixed Concrete Association Plant
Certification meet the requirements
of this specification.
ASTM International: C685/C685M
Standard Specification for Concrete
Made by Volumetric Batching and
Continuous Mixing

VARIATION IN CONCRETE
PERFORMANCE
DUE TO BATCHING
• The NRMCA Plant Certification requires producers to verify scale
accuracy at least once every six months and arrange for prompt
recalibration and correction if non-compliance is indicated or if the
plant is moved or other maintenance impacts the weighing systems.
• NRMCA certification requires that volumetric measuring of volumetric
measuring devices for water and chemical admixtures should be
checked for accuracy at least once every 6 months.
• The batching accuracy requirements in the NRMCA Plant Certification
program are as required in ASTM C94 and stated in Table 1.
• For weighed ingredients, accuracy of batching is determined by
comparison between the desired weight and the actual scale
reading; for volumetric measurement of water and admixtures,
accuracy is determined by checking the discharged quantity relative
to the target, either by weight on a scale or by volume in an
accurately calibrated container. Volumetric measurement is
commonly used for water and typically used for chemical admixtures.
It is realized that on any single batch, at least one of the ingredients
may be out of tolerance, as discussed later.
• For the NRMCA plant certification, inspectors are advised to review
several batch records and to determine that the plant complies with
the batching accuracy by reviewing the average of at least 10
batches of concrete.
• Improving batching accuracy can help attain more consistent
performance for fresh concrete properties that is important to the
contractor and to reduce variation of compressive strength of
concrete

RECOMMENDED PRACTICES FOR
BATCHING AND MIXING SCC:
• Always know and adjust for moisture in aggregates. Moisture
meters for sand are strongly recommended. When producing
SCC, run a moisture test on all aggregates within 1.5 hours of
actual batching of SCC. If the plant does not have a moisture
meter, moisture should be tested throughout the day. At a
minimum, determine aggregate moisture at the beginning of the
work day, mid morning, and mid afternoon. Also check moisture
any time new material is delivered to the plant.
• Once the admixture dosage is established, it should not vary
unless water demand of the materials has changed. This could be
due to changes in any of the components – aggregates, cement,
supplementary cementitious materials.
• Run gradations on aggregates a minimum of once per week or
whenever the SCC mix appears to have changed. If gradations
have changed, adjust mix proportions accordingly.
• Run a laboratory trial once per month, or whenever the mix
appears to have changed, to expose possible water demand
changes.
• If a central mixer is used, monitor the mixer amp meter as a
measure of moisture level and water demand. Confirm that your
amp meter can distinguish between an empty mixer and a highly
flowable SCC mix. If not, install a higher quality digital meter (0.1
amp resolution). In the absence of HRWR, identify an amperage
reading that corresponds to a slump which produces good SCC
upon later addition of the SCC admixture. If the amp reading is
too high, adjust with water. The amp reading should be stable
before adding the SCC admixture. Establish a second target for
after the addition of the SCC admixture. Adjust with admixture if
the reading is too high. Changing amp readings are an important
indicator of changes in materials.
• If using a truck mixer, occasionally confirm moisture control and
water demand by measuring the slump before SCC admixture
addition. Changes in “zero-admixture” slump are an indication of
changes in sand moisture or water demand. The “zero-admixture”
slump should be within ± 25 mm (1 in.) of the predefined target.
• Make sure the truck mixer is empty – as little as 5 L/m3 (1 gal/yd3)
of water can make the difference between success and failure.
Reverse ALL water and material out of drum before backing under
the batch plant. It is critical to make this point clear to truck
drivers.
• Mix SLOWLY. Poly-carboxylates that are designed to produce
highly stable SCC develop workability more slowly than typical
high range water reducers. Fast mixing leads to poor
reproducibility and can induce excess foaming, which is difficult to
get rid of after the fact. The concrete should have a folding
motion, not a slapping motion. For truck mixers, 1⁄2 speed (8-10
rpm) is sufficient.
• Do not deliver the concrete until the contractor or finisher is ready.
Standing trucks can cause an SCC pour to go very badly.
• As a general rule, addition of 5 L/m3 (1 gal/yd3) of water to SCC
can increase slump flow 50-75 mm (2-3 in.); while removing 5 L/m3
(1 gal/yd3) reduces slump flow 50-75 mm (2-3 in.)
• Air content can have an impact on slump flow. The direction and
magnitude of this relationship depends on the materials, mix
design, and the amount of air.

EPA –
US ENVIRONMENTAL PROTECTION
AGENCY
Air quality
management
The maximum level of concentration of solid
particles, at testing points determined in
accordance with this policy, is a total mass of 250
mg/m3 of residual gases after completion of the
process and before amalgamation with air, smoke or
other gases.
In the case of concrete batching plants, cement,
sand and aggregates can produce dust which may
enter neighboring premises and adversely affect
amenity value.
The best way to avoid offsite problems is to prevent
the release of the dust through good design and
management techniques. The provision of natural or
artificial wind barriers such as trees, fences and
landforms may help control the emission of dust from
the plant.
All concrete batching plant sites should demonstrate
good maintenance practices, including regular
sweeping to prevent dust build-up.
The prevailing wind direction should be considered
to ensure that bunkers and conveyors are sited in a
leeward position to minimize the effects of the wind.
Aggregate material should be delivered in a damp
condition, and water sprays or a dust suppression
agent should be correctly applied to reduce dust
emissions and reduce water usage. Aggregate
stored on site in stockpiles should be contained
within three-sided storage bunkers with windshields
that project 0.5 meter above the bunker wall.
Conveyors must be designed and constructed to
prevent fugitive dust emissions. This may include
covering the conveyor with a roof, installing side
protection barriers and equipping the conveyor with
spill trays, which direct material to a collection point.
Belt cleaning devices at the conveyor head may
also assist to reduce spillage. Mixer loading areas
should be roofed and enclosed on either two (drive-through)
or three sides. Water sprays and/or dust
curtain of suitable design, or an effective air
extraction and filtration system, should be installed to
suppress dust generated during mixer truck loading.
Weigh bins and hoppers should be enclosed on
three sides and roofed where a front-end loader is
used. The roof should extend 2 meters in front of the
bin. Any raw material spills should be removed
promptly by dry sweeping. Water should not be used
in the process of cleaning up spills except where the
area drains to a wastewater collection point where
washing down would be preferable to generating
dust by sweeping.
An approved fabric filter incorporating a fabric-cleaning
device should be installed on each cement
storage silo.
Adequate access to the filters should be provided to
allow for regular inspection and maintenance. A
pollution control equipment register (PCER) should
be used to record, on a weekly basis, the following:
pressure drop visual conditions of exhaust material
incidents of filter media failure/replacement.
Water management
Potential pollutants in batching plant waste water
and storm water include cement, sand, aggregates,
chemical admixtures, fuels and lubricants. The site
should be designed and constructed such that
clean storm water, including roof run off, is diverted
away from contaminated areas and directed to the
storm water discharge system. Underground storage
tanks should be tested annually for integrity.
Contaminated storm water and process wastewater
should be captured and recycled. Concrete
agitator bowls and chutes must never be washed
out to the storm water system or roadways.
Process wastewater and contaminated storm water
collected from the entire site should be diverted to a
settling pond, or series of ponds.
In general a high standard of yard and equipment
maintenance will considerably reduce the potential
for discharge of sediment to the wastewater
collection and recycling system.
Regular inspection and maintenance of the system is
necessary to avoid discharges of contaminated
water from the site. These inspections and
maintenance should be recorded. Areas where spills
of oils and chemicals may occur should be
equipped with easily accessible spill control kits to
assist in prompt and effective spill control, according
to the EPA Guidelines, Bonding and spill
management. Staff should be familiar with spill
response and notification procedures

NATIONAL READY MIXED CONCRETE ASSOCIATION

NRMCA CERTIFICATION
• NRMCA Personnel Certifications:
• Certified Concrete Sales Professional (CCSP)
• Certified Sustainability Professional
• Concrete Delivery Professional Certification
• Concrete Field Testing Technician Grade II
• Concrete Green Building Certification
• Concrete Sustainability Professional
Certification
• Concrete Technologist Level 2 "Technical
Short Course"
• Concrete Technologist Level 3
• Concrete Technologist Level 4 "Durability
Course"
• Effective RMC Supervisor Certification
• Environmental Professional Certification for
the Ready Mixed Concrete Industry
• Fleet Manager Certification
• NRMCA Plant Certifications:
• Quality: Plant and Truck Certification
• Quality Certification Program
• Environmental Stewardship: Green-Star
Certification Program
• Sustainability: Sustainable Concrete Plant
Certification
• Plant Manager Certification
• NRMCA Safety Certification (Online)
• OSHA 10-Hour Safety Certification for
General Industry
• Pervious Contractor Certification
• Plant Manager Certification
• Sales Manager Ceritification
• NRMCA Product Certifications:
• NRMCA Certified Environmental Product
Declaration

RAW MATERIALS
CHECK LIST FOR READYMIX CONCRETE
PRODUCTION FACILITIES
• Cementitious Materials
• .1 Bins or silos are tight and with free
movement to discharge opening [ ]
• .2 Separate storage is provided for
different types of cementing
materials to prevent contamination
– common bag houses should
shake down into the least affected
cementing material [ ]
• .3 Intra-plant handling prevents
contamination [ ]
• .4 All cementitious feed pipes are
marked and designated (e.g. GU,
HS, Fly Ash, etc)[ ]

RAW MATERIALS
• Aggregates
• .1 Aggregates stockpiles are
arranged to assure that each
aggregate as removed is clean,
distinct and not intermingled with
others
• .2 Procedures for unloading and
storing aggregates prevents harmful
segregation [ ]
• .3 Intra-plant handling and
transportation prevents harmful
segregation [ ]
• .4 Separate storage bins or
compartments for each size and
type of aggregate are properly
constructed and charged to
prevent mixing of different sizes and
types [ ]

RAW MATERIALS
• Water
• .1 Adequate supply with pressures
sufficiently constant or regulated to
prevent interference with accuracy of
measurement where flow meters are
used to measure mixing water – the flow
meter shall be calibrated and
documented at intervals of no more
than six months [ ]
• .2 The concrete producer must provide
certification that the water used meets
the requirements of CSA A23.1 at all
times. Water for concrete production
may be from one of the following
sources:
• Potable source (water is supplied by a
government/commercial agency) [ ]
• Non-potable source (satisfactory
history of strength and durability
made with the water has been
demonstrated) [ ]
• Water from concrete production
operations [ ]

RAW MATERIALS
Admixtures
.1 Storage of liquid admixtures is
provided to prevent damage by
freezing or contamination
2 Agitation is provided for liquid
admixtures that are not stable
solutions [ ]
.3 Each admixture shall be measured
and discharged separately [ ]

CHAPTER 4: Production Facilities
4.1 Compliance with Standards:
Production facilities and delivery
vehicles conform to the requirements
of ASTM C94.
• For delivery vehicles provide
statement on procedures and
frequency to evaluate blade
wear and buildup in truck mixers.
• Review statement by company on
frequency of verification of
accuracy of scales and
volumetric measuring devices.
• Review records of one scale
verification record– load test data
sheet required.
QUALITY CERTIFICATION
4.2 Monitoring Batching Accuracy:
PROGRAM
Provide description of:
• Procedures used to identify and
address out of-tolerance batches.
Indicate the specific individual
with responsibility for monitoring
batching accuracy.
• Describe corrective actions used
for consistent out of tolerance
situations.
• Provide two batch records from
each plant within the last 3
months. Records should indicate
target and actual quantities
batched for cementitious
materials, aggregates, batch
water and admixtures. Tolerance
information should be included in
batch records.
Procedures stated to monitor and to
address out of tolerance batches
• Review procedures used to
identify out-of-tolerance batches
and decision process and
responsibility for addressing these
situations.
• Review corrective action.
• Review 2 batch records from each
plant in submission within the last 3
months.

CHAPTER 4: Production Facilities
4.3 Control of Mixing Water.
Procedures stated to control mixing
water to within the ASTM C94
tolerance of ±3%
Review procedures used for control of
mixing water to include, but not
limited to:
• Frequency of verifying accuracy
of plant water measuring devices,
procedure used and accuracy
requirements.
• Verifying accuracy of measuring
devices (volumetric to 1.5%, scales
as per scale check) and
frequency
• Addressing mixer wash-water prior
to batching.
• Control of mixing water addition
at the slump rack.
QUALITY CERTIFICATION
PROGRAM
• Verifying accuracy of water
measuring devices on truck water
tanks – procedure and frequency
(water meters accurate to ±2%,
sight gages accurate to ±1
gallon).
• Process for trim water holdback
and communicating limits of
water addition to the purchaser
and procedures required by
drivers at the jobsite
Review sample of 1 delivery tickets
from each plant in the submission of
delivered loads documenting the
recording of jobsite water addition
and signature of purchaser.

PLANT CERTIFICATION
GUIDANCE TO CONCRETE PRODUCERS SEEKING
AND MAINTAINING PLANT CERTIFICATION
SCALE ACCURACY VERIFICATION
Scale accuracy should be verified anytime the plant is
moved, maintenance activities on the plant impact the
weighing systems, or when there is a concern on scale
accuracy determined from the batchman operating
the batching process or the quality of concrete.
There are some differences in what the scale
companies are accustomed to doing and what is
required by the NRMCA plant certification and ASTM
C94. The following should be communicated with the
scale company before they do scale checks:
• Minimum quantity of test weights should be at 10% of
scale capacity. Aggregate scale capacities will
generally govern the minimum amount of test
weights required – about 4000 lbs is typically needed.
(There may be situations where the plant
configuration does not permit the minimum test
weights to be used and that has to be verified by the
plant inspector).
• Test weights should be certified to be accurate to
0.01% of their indicated load within the last two
years. This is typically not a problem with commercial
scale companies.
• Scale checks should be done through range of use
of the scales. Scale companies may only verify it
through 50% of the scale capacity.
• Up through 50% of the scale capacity, scale checks
should be done using a build-up test load using a
combination of product and test weights in a
process called a substitute test. Scale increments
should not be skipped. In substitute testing, product
in the scale should only be to the load previously
verified – as close as possible.
• Over 50% of the scale capacity, strain test loading is
permitted. An unknown quantity of product is
charged and the incremental weight indication with
the test weights is verified. At least two points should
be tested in this portion of the scale – through typical
range of use.
• Scale accuracy requirements (ASTM C94) is the
greater of
• ±0.15% of scale capacity (governs at the lower
end)
• ±0.4% of applied test load
• If it's not accurate the scale has to be adjusted.
• A copy of the scale verification data sheets should
be obtained to indicate details of the test loads
used, test load increments, load indications and load
error. A certificate just indicating a scale is OK is not
acceptable.

SCALE ACCURACY VERIFICATION
• Additional Information
• a. Each scale is comprised of a suitable
system of lever and/or load cells, which
will weigh consistently within the
tolerance specified by the MRMCA, with
loads indicated either by a beam with a
balance indicator or a full reading dial or
digital readout display verifying
accuracy.
• b. Each scale must be calibrated at a
minimum of 2 points and at 20% and 80%
of the scales normal operating capacity.
• c. The Scale Manufacturer or Scale
Company must supply the necessary
documentation that government
approved test weights are used, which
are certified and traceable.
PLANT CERTIFICATION
• d. The Scale Manufacturer or Scale
Company must provide a procedure or
check list which is used for the inspection
and to document all mechanical checks,
calibration test results and any
deficiencies in the scale or weighing
system.
• e. The Scale Manufacturer or Scale
Company’s qualified technician must sign
the MRMCA Scale Check Data Form
certifying that all requirements have been
met.
• f. All scale check and calibration
reports/records must be kept on site and
must be available for inspection at all
times.

PLANT CERTIFICATION
WATER METER ACCURACY VERIFICATION
Accuracy of water meters should be
verified at least once every six months.
Maintain documentation of these
verifications for review by the inspector.
Accuracy of water meters is the same as
that required for batching accuracy
±1.5%. Measure accuracy using a large
enough volume of water – at least 50
gallons. Methods include:
• Discharge water into a 55-gallon drum
and weigh the quantity – can be
suspended from the cement scale.
• Perform this at least 3 times to obtain an
average.
• Some discharge 200+ gallons into a
truck mixer if truck scales are available.
After weighing the truck, water is
discharged and the truck is weighed
empty to determine water in the drum.
• Discharge water into a calibrated
container of at least 50 gallon
capacity. Calibrations on the container
should be accurate enough to
measure to within the required
accuracy tolerance.
When water is measured by weight,
accuracy requirements for scales apply.
COE CRD-C 143-62 Handbook for Concrete and Cement Specifications For Meters For Automatic Indication Of
Moisture ln Fine Aggregate

PLANT CERTIFICATION
ADMIXTURE DISPENSER ACCURACY VERIFICATION
The batching accuracy of dispensers of liquid admixtures
shall be checked at least every 6 months. This dispenser
accuracy check is usually performed by collecting the
chemical admixture into a calibrated container. It is
acceptable to use a dispenser measuring unit as the
calibrated container.
The process for checking accuracy using a calibrated
dispenser measuring unit is as follows:
• A dosage quantity check should be performed for each
dispenser.
• Determine the target quantity based on a typical
dosage rate within the recommended dosage range.
• Dose target quantity of admixture into the dispenser
measuring unit and hold for visual measurement.
• Calculate and confirm accuracy.
When the admixture is measured by a meter and batched
through a direct feed admixture system (with no dispenser
measuring unit), the accuracy check is conducted using a
calibrated flask/container. The process for checking
accuracy using graduated flask or container:
• A dosage quantity check should be performed for each
dispenser.
• Determine the target quantity based on a typical
dosage rate within the recommended dosage range,
but usually limited to under 5 gallons.
• Dose target quantity of admixture into calibrated
flask/container for measurement.
• Calculate and confirm accuracy.
The company can perform their own dispenser accuracy
checks instead of calling the dispenser representatives. If
the meter is not accurate, the admixture dispenser
representatives should be called in to calibrate the
dispensing system. Documentation of admixture dispenser
accuracy verification should be retained for review by the
inspector.
Some producers collect admixture at the point of
discharge into the mixer to verify the accuracy of the
dispensing system. This process checks the integrity of the
lines through which the admixture flows in addition to the
dispenser accuracy.

PLANT CERTIFICATION
MOISTURE PROBE ACCURACY VERIFICATION
Follow manufacturer’s directions for
verifying accuracy.
• The accuracy of moisture probes
should be relative to an aggregate
moisture measurement by drying
out an aggregate sample on a hot
plate or microwave oven (ASTM
C566). The aggregate sample
tested should be obtained from as
close to the location of the moisture
probe measuring the aggregate
moisture.
• There is no stated accuracy
(tolerance) for moisture probes in
the NRMCA Check List. Using the
required accuracy (±1.5%) for water
meters can be considered as a
basis for requiring corrections to the
device (calibration).
• Maintain documentation of these
checks and provide for review to
the inspector.

SUMMARY
ITEM Frequency Other
Monitoring Batching Accuracy Review 2 batch records from each plant in submission within the last 3
months.
Review procedures used to identify out-of-tolerance
batches and decision process and responsibility for
addressing these situations.
Review corrective action.
Control of Mixing Water Review sample of 1 delivery tickets from each plant in the submission of
delivered loads
Scale accuracy verification Anytime the plant is moved, maintenance activities on
the plant impact the weighing systems, or when there is a
concern on scale accuracy determined from the
batchman operating the batching process or the quality
of concrete
Water meter accuracy verification &
Water Flow Meter
At least once every six months. When water is measured by weight, accuracy
requirements for scales apply.
Admixture dispenser accuracy
verification
Checked at least every 6 months
Moisture Probe accuracy verification ACI 304.R/3.5.2 Aggregate moisture determination and compensation
Moisture meters should be recalibrated monthly or whenever the slump of the
concrete produced is inconsistent.
Followmanufacturer’s directions for verifying accuracy
All measuring devices shall be subject to approval and shall be tested, at the
Contractor's expense, when deemed necessary by the Contracting Officer.
Section 34 90 08
Art. 2.4.3
consistency-recording meters, such as
those operating from the amperage
Some draw on the electric motor drives for revolving-drum mixers, have also
proven to be useful. The most positive control method for maintaining batch-to-
batch uniformity, however, is a regularly scheduled program of tests of the
fresh concrete, including unit weight, air content, slump, and temperature.

PLANT MAINTENANCE PLAN

DAILY
1. Inspect oil and filter on air
compressor and drain tank,
manifolds, and all water traps.
2. Inspect and fill all oilers on plant.
3. Inspect all air cylinders.
4. Inspect tension on all V-drive belts.
5. Inspect conveyor belts for
alignment and excessive wear.
6. Perform housekeeping items, such
as cleaning up dust and debris.
First, the mechanism of lubricating oil
should be change often.
Before work, the machine should
have an empty running.
Second, check whether there is
water in the bucket of ingredients; if
you find some, clean it up.

DIARIO
1. Inspeccione el aceite y el filtro de aire
del compresor y el tanque de drenaje,
colectores, y todas las trampas de
agua.
2. Inspeccione y rellene todos los
engrasadores en planta.
3. Inspeccione todas las botellas de aire.
4. Inspeccione la tensión de todas las
correas V-drive.
5. Inspeccione las correas
transportadoras para la alineación y el
desgaste excesivo.
6. Lleve a cabo los elementos de
limpieza, tales como la limpieza de
polvo y escombros.
En primer lugar, el mecanismo de
aceite lubricante se debe cambiar
con frecuencia.
Antes del trabajo, la máquina debe
tener un funcionamiento vacía.
En segundo lugar, comprobar si hay
agua en el cubo de ingredientes; si
encuentra alguna, limpiarlo.

Weekly
1. Lubricate all bearings (ONE PUMP ONLY).
Included are head and tail pulleys on all
conveyors, snubber roller on loading
conveyor, head and tail bearings on
cement feeder screws, wheel bearing
supports on turn head, etc.
2. Lubricate all aggregate gate pivot
points.
3. Replace or blow clean all air filters on air
compressor and aeration blowers.
4. Inspect and tighten all bolts and
bearing set screws.
5. Inspect and/or adjust all belt
wipers.
6. Lubricate packing at the bottom
and top ends of the cement feeder
screws with oil.
7. Inspect all bags in cement bag
filters.
Be very careful with the batching's
control instrument, because this is an
electronic instrument, once exposed
to the sun or rain or lightning, it will be
damaged and seriously affect the
accuracy of the ingredients, which
affect the progress. The batching's
control instruments should be placed,
by erection, in a facility that will be
sun proof, rainproof, dustproof and
lightning protected.

Semanal
1. Lubrique todos los cojinetes (UNA
BOMBA SOLAMENTE). Se incluyen en la
cabeza y la cola poleas en todos los
transportadores de rodillos, cojinetes de
carga amortiguador en transportadoras,
cabeza y cola de tornillos alimentadores
de cemento, cojinete de la rueda apoya
en la cabeza a su vez, etc.
2. Lubrique todos los puntos de pivote
puerta agregados.
3. Vuelva a colocar o golpe limpio todos
los filtros de aire en el compresor de aire y
sopladores de aireación.
4. Inspeccione y apriete todos los
pernos y tornillos de fijación del
rodamiento.
5. Inspeccione y / o ajustar todos los
limpiadores de correa.
6. Lubricar embalaje en la parte
inferior y los extremos superiores de
los tornillos de alimentación de
cemento con aceite.
7. Inspeccione todas las bolsas en los
filtros de bolsa de cemento.
Tenga mucho cuidado con el
instrumento de control de la
dosificación, ya que este es un
instrumento electrónico, una vez que
se expone al sol o la lluvia o los
rayos, se dañará y afecta seriamente
la exactitud de los ingredientes, que
afectan a los progresos. Instrumentos
de control de la dosificación deben
ser colocados, por la erección, en
una instalación que va a ser a
prueba de sol, impermeable, a
prueba de polvo y relámpagos
protegidos.

Monthly
1. Inspect oil level in all gear reducers.
2. Adjust skirt boards as needed.
3. Adjust and tighten conveyor belts
as needed.
4. Change oil in air compressor.

Mensualmente
1. Revise el nivel de aceite en todos
los engranajes reductores.
2. Ajuste faldones, según sea
necesario.
3. Ajuste y apriete las cintas
transportadoras, según sea
necesario.
4. Cambie el aceite del compresor
de aire.

Semiannually
1. Change oil in all conveyor gear
reducers.
2. Remove bags in cement bag filters
and blow clean.
3. Tighten or replace all V-belts as
needed.
4. Inspect scale and water meter
accuracy.
5. Inspect hanger bearings in feeder
screws and replace as needed.
6. Inspect and acidize boiler.
7. Inspect and/or replace bin
aeration pads

Semi-anualmente
1. Cambie el aceite en todos los
reductores transportadora.
2. Retire las bolsas de filtros de bolsa de
cemento y golpe limpio.
3. Apriete o reemplace todas las correas
en V, según sea necesario.
4. Inspeccione la precisión de escala y
agua metros.
5. Inspeccione los cojinetes de la
suspensión en los tornillos de
alimentación y reemplace según sea
necesario.
6. Inspeccione y acidificar la caldera.
7. Inspeccionar y / o reemplazar las
almohadillas del bin aireación

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