PART C: COMPLETE THE DESIGN PROCEDURES
5. You completed step 1 of this process (Part B) when you determined the materials needed to
construct a concrete form. Now you are ready to design the actual form and will do this by
completing steps 2 through 17.
6. First, determine the rate of placing or the vertical fill rate per hour of the form. This
computation involves three parts. Determine the mixer output (step 2), the plan area (step 3), and
the rate of placing (step 4). Each of these steps is explained in the following pages.
Step 2. Determine the mixer output. Determine the mixer output by dividing the mixer
capacity by the batch time. The unit measurement for mixer output is measured in cubic feet
per hour (FPH). If you use more than one mixer, multiply the output by the number of
mixers. Batch time includes loading all ingredients, mixing, and unloading. Batch time is
measured in minutes. If the answer contains a decimal, round up to the next whole number.
Compute as follows:
mixer capacity (cu ft) 60 (min)
Mixer output (cu FPH) =
x
x number of mixers
(1)
batch time (min)
1 (hr)
EXAMPLE:
Determine the mixer output if the mixer capacity is 16 cubic feet, the batch time is 7 minutes,
and the mixer operates for 1 hour.
16 60
960
Mixer output =
x
x 1=
= 137.14, round up to 138 cu FPH
(2)
7
1
7
Problem 6. Work the following problem to see how well you understand the concept
covered in step 2. The solution to this problem is found at the end of the lesson. Determine
the mixer output if the mixer capacity is 16 cubic feet and the batch time is 6 minutes with
two mixers operating for 1 hour.
A.
290
B.
308
C.
320
D.
328
Step 3. Determine the plan area. The plan area is the area enclosed by the form. Determine
the plan area by multiplying the length by the width (it is measured in square feet). Compute
as follows:
Plan area (sq ft) = form L (ft) x form W (ft)
(3)
where--
L = length
W = width
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