3.1.2
Batch Plant
Batch plant shall conform to the requirements of NRMCA CPMB 100and as
specified; however, rating plates attached to batch plant equipment are not
required.
3.1.2.1
Batching Equipment
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NOTE: Refer to the appropriate DM to choose the
appropriate alternates.
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The batching controls shall be [partially automatic], [semiautomatic], [or]
[automatic]. [The semiautomatic batching system shall be provided with
interlocks such that the discharge device cannot be actuated until the
indicated material is within the applicable tolerance.] The batching
system shall be equipped with an accurate recorder or recorders that meet
the requirements of NRMCA CPMB 100. Separate bins or compartments shall be
provided for each size group of aggregate and cement, pozzolan, and GGBF
slag. Aggregates shall be weighed either in separate weigh batchers with
individual scales or cumulatively in one weigh batcher on one scale.
Aggregate shall not be weighed in the same batcher with cement, pozzolan,
or GGBF slag. If both cement and pozzolan or GGBF slag are used, they may
be batched cumulatively provided that the portland cement is batched first.
If measured by mass, the mass of the water shall not be weighed
cumulatively with another ingredient. Water batcher filling and
discharging valves shall be so interlocked that the discharge valve cannot
be opened before the filling valve is fully closed. An accurate mechanical
device for measuring and dispensing each admixture shall be provided. Each
dispenser shall be interlocked with the batching and discharging operation
of the water so that each admixture is separately batched and discharged
automatically in a manner to obtain uniform distribution throughout the
batch in the specified mixing period. Admixtures shall not be combined
prior to introduction in water. The plant shall be arranged so as to
facilitate the inspection of all operations at all times. Suitable
facilities shall be provided for obtaining representative samples of
aggregates from each bin or compartment. All filling ports for
cementitious materials bins or silos shall be clearly marked with a
permanent sign stating the contents.
3.1.2.2
Scales
The equipment for batching by mass shall conform to the applicable
requirements of NIST HB 44, except that the accuracy shall be plus or minus
0.2 percent of scale capacity. The Contractor shall provide standard test
weights and any other auxiliary equipment required for checking the
operating performance of each scale or other measuring devices. Tests
shall be made at the frequency required in paragraph TESTS AND INSPECTIONS,
and in the presence of a government inspector.
3.1.2.3
Batching Tolerances
a.
Weighing Tolerances
PERCENT OF REQUIRED
MATERIAL
MASS
Cementitious materials
0 to plus 2
SECTION 03301A
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