TIME ELEMENT
A carpenter of average skill can build and erect 10 square feet of wood forms per hour. This figure increases as
the worker becomes more skilled in form construction. It also varies with the tools and materials available and
the type of form. Some forms, such as those for stairways, require considerable physical support from
underneath. Such forms take more man-hours and materials to build than simpler forms. For carpenters to move
from one level to another frequently requires additional time. Therefore, increased manpower support at the
ground level increases efficiency.
PART C - MIXING, HANDLING, TRANSPORTATION, PLACEMENT,
FINISHING, AND CURING OF CONCRETE
MIXING
Principles
You must follow established and well-defined concrete mixing procedures to produce good quality finished
concrete. You can never overcome oversights in this phase of concrete construction, whether caused by lack of
competent and conscientious supervision or inattention to detail. Whoever is in charge of construction must know
the concrete mixing procedures and make sure that they are followed. The extra effort and care this requires are
small in relation to the benefits.
Measuring Mix Materials
Concrete of uniform quality requires measuring the ingredients accurately. Check equipment accuracy
periodically and adjust when necessary. Check admixture dispensers daily because errors in admixture
measurements, particularly overdoes, can cause serious problems in both fresh and hardened concrete.
Cement
Concrete mixes normally call for sacked cement as the unit of measure.
Aggregate
Measure aggregate for each batch accurately, either by weight or by volume. Measurement by weight is the most
reliable because the accuracy of volume measurement depends on an exact knowledge of the amount of moisture
in the sand. Nevertheless, sometimes measurement by volume is more practical.
Measurement by weight. On comparatively small jobs, you can use platform scales placed on the ground
to weigh aggregate. Construct runways as shown in Figure 4-1, so that a wheelbarrow can be run onto
one side of the scale and off the other easily. With practice, you can fill a wheelbarrow so accurately that
adding or removing material to obtain the correct weight is seldom necessary. Always place the same
weight of aggregate on each wheelbarrow so that the quantity per batch equals the same number of
wheelbarrow loads. You need not load a wheelbarrow to capacity.
EN5466
4-4
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