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There have been questions
raised by some producers as to what the cement content of concrete masonry
units should be to obtain a quality product that meets ASTM specifications.
We have to, of course, start with a good aggregate that has a good gradation
and is not too dirty or gap-graded. The aggregate should be sound and of a
non-friable nature that does not have a tendency to fracture during the
forming process.
Many concrete product
producers have chosen to use the quantities of cement laid out in the chart
below. Some producers have opted to utilize less cement but there is always
the chance that other aspects of the mix can change and affect quality.
Included in this is the aggregate gradation and moisture content. Another
thing that can affect quality is cyclic variations in the forming process
that result in density variations.
The following chart is
presented as a starting point and cannot be considered generic because of
the widespread differences in available aggregates. The cement contents will
need to be adjusted to compensate for aggregate variations.
TYPICAL WEIGHT OF CEMENT PER CONCRETE MASONRY UNIT
|
CMU UNIT SIZE |
NORMAL WEIGHT |
LIGHTWEIGHT |
|
4" |
2.0-2.4 LBS |
2.1-2.6 LBS |
|
6" |
2.6-3.1 LBS |
2.8-3.3 LBS |
|
8" |
3.0-3.5 LBS |
3.2-3.8 LBS |
|
10" |
4.2-4.9 LBS |
4.5-5.3 LBS |
|
12" |
4.6-5.3 LBS |
4.9-5.7 LBS |
SAFETY BULLETIN
This notice is issued to advise you that some previously
accepted shop practices may not be keeping up with
changing Federal and State Safety and Health Standards. Your current shop
practices may not emphasize the need for
proper precautions to insure safe operation and use of machines, tools,
automatic loaders and allied equipment
and/or warn against the use of certain solvents or other cleaning substances
that are now considered unsafe or prohibited by
law. Since many shop practices may not reflect current safety
practice and procedures, particularly with regard to the safe operation of
equipment, it is important that you
review your practices to ensure compliance with Federal and State Safety and
Health Standards.
IMPORTANT
The operation of any machine or power-operated device can
be extremely hazardous unless proper safety precautions
are strictly observed. Observe the following safety precautions:
Always be sure proper
guarding is in place for all pinch, catch, shear, crush and nip points.
Always be sure that
all personnel are clear of the equipment before starting it.
Always be sure the
equipment is properly grounded.
Always turn the main
electrical panel off and lock it out in accordance with published lockout/
tagout procedures prior to making adjustments,
repairs, and maintenance.
Always wear
appropriate protective equipment such as safety glasses, safety shoes,
hearing protection and hard hats.
Always keep chemical
and flammable material away from electrical or operating equipment.
Always maintain a
safe work area that is free from slipping and tripping hazards.
Always be sure
appropriate safety devices are used when providing maintenance and repairs
to all equipment.
Never exceed the
rated capacity of a machine or tool.
Never modify
machinery in any way without prior written approval of the Besser
Engineering Department.
Never operate
equipment unless proper maintenance has been regularly performed.
Never operate any
equipment if unusual or excessive noise or vibration occurs.
Never operate any
equipment while any part of the body is in the proximity of potentially
hazardous areas.
Never use any toxic
flammable substance as a solvent cleaner.
Never allow the
operation or repair of equipment by untrained personnel.
Never climb or stand
on equipment when it is in operation.
It is important that you review
Federal and State Safety and Health Standards on a continual basis. All
shop supervisors, maintenance personnel, machine
operators, tool operators, and any other person involved
in the setup, operation, maintenance, repair or adjustment of Besser-built
equipment should read and understand this
bulletin and Federal and State Safety and Health Standards on which this
bulletin is based. |
