control charts shall be kept in the field by the Contractor's quality
control representatives and results plotted as tests are made. When a
single test result reaches the upper or lower action limit, a second
test shall immediately be made. The results of the two tests shall be
averaged. This average shall be used as the air content of the batch
to plot on the control chart for air content and on the control chart
for range and to determine the need for any remedial action. The
result of each test, or average as noted in the previous sentence,
shall be plotted on a separate chart for each mixture on which an
average line is set at the midpoint of the specified air-content range
from paragraph AIR CONTENT. An upper warning limit and a lower warning
limit line shall be set 1.0 percentage point above and below the
average line. An upper action limit and a lower action limit line
shall be set 1.5 percentage points above and below the average line,
respectively. The range between each two consecutive tests shall be
plotted on a control chart for range where an upper warning limit is
set at 2.0 percentage points and up upper action limit is set at 3.0
percentage points. Samples for air content may be taken at the mixer;
however, the Contractor is responsible for delivering the grout to the
placement site at the stipulated flow. If the Contractor's materials
or transportation methods cause flow loss between the mixer and the
placement, correlation samples shall be taken at the placement site as
required by the Contracting Officer and the air content at the mixer
controlled as directed.
b. Air-Content Corrective Action - Whenever points on the control
chart for percent air reach either warning limit, an adjustment shall
immediately be made in the amount of air-entraining admixture batched.
As soon as is practical after each adjustment, another test shall be
made to verify the result of the adjustment. Whenever a point on the
control chart range reaches the warning limit, the admixture dispenser
shall be recalibrated to ensure that it is operating accurately and
with good reproducibility. Whenever a point on either control chart
reaches an action limit line, the air content shall be considered out
of control and the concreting operation shall immediately be halted
until the air content is under control. Additional air-content tests
shall be made when grout mixing is restarted. All this shall be at no
extra cost to the Government.
3.6.2.7
Grout Flow
a. Tests - At least two tests shall be made on randomly selected
batches of grout mixture during each shift's production in accordance
with ASTM C 939. Additional tests shall be made when excessive
variation in flow of grout mixture is reported by the grout foreman or
Government inspector. Test results shall be plotted on control charts
which shall at all times be readily available to the Government.
Copies of the current control charts shall be kept in the field by the
Contractor's quality control representatives and results plotted as
tests are made. When a single-flow test reaches or goes beyond the
upper or lower action limit, a second test shall immediately be made on
the same batch of concrete. The results of the two tests shall be
averaged. This average shall be used as the flow of the batch to plot
on the control chart for flow and the chart for range and to determine
the need for any remedial action. An upper warning limit shall be set
at 1 second below the maximum allowable flow on separate control charts
for flow used for each type of mixture as specified in paragraph GROUT
FLOW, and upper and lower action limit lines shall be set at the
maximum and minimum allowable flows, respectively, as specified in the
SECTION 03372
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