The Concrete is a man-made material, essentially
mixed at site. The properties of concrete depend on the properties of its
ingredients and their proportion, and it is likely to vary from mix to mix.
Tests must be conducted, therefore, to ensure that the concrete used is in
accordance with design specifications. It is a frequent test of compressive
strength, in which concrete samples are tested to failure.
A. Compression Testing Machines with Load Gauges
A brief general description of these machines is
:
Loading Unit : The loading unit is of fully welded construction
having a cross head, base and solid side plates. The hydraulic jack is fixed
to the base or on the top. The platens of the machine are hardened, ground
and polished. The upper platen is provided with self-aligning action. To
facilitate testing of various size specimens, suitable size spacers are
provided.
Pumping Unit : The hydraulic pumping unit is :
- Manually Operated or
- Electrically operated
The loads are measured on Bourdon tube type pressure gauges, which are
calibrated against certified proving rings. The pressure gauges are fitted
with a maximum load pointer. Both the Pumping units, manually operated and
electrically operated, are of two-speed design. In the Electrically Operated
Pumping Units, Pressure gauges are fitted with micro switches to switch-off
the motor when the load approaches the maximum capacity of the pressure
gauge, avoiding any over-loading. Relays are incorporated so that the motor
does not restart own after a power breakdown. The Electrically operated
pumping units can also be fitted with hand-operated pump as an option.
B. Digital Compression Testing Machines
The Digital Compression Testing Machine has been
designed to meet the need for a simple, economic and reliable means to test
concrete for its compressive strength. The design emphasizes simplicity,
both of construction and operation, and makes machine easy to use and
maintain. The unit is compact, making it useful for site applications. The
digital machines are provided with a pace rate controller, to enable
maintain a constant rate of loading. The Complete unit comprises :
Loading Unit is of fully welded construction having a cross-head
with a spherical seated platen. The lower platen is attached to the top of
the piston. The Loading Units of capacities, 250 kN, 500 kN, 1,000 kN, 2,000
kN and 3,000 kN are available. Cubes up to 300 mm & Cylinders up to 300
mm dia x 300 mm height can be tested using the appropriate models.
Pumping Unit, The two speed pump facilitates rapid approach of the
platens for daylight closure and also provides comprehensive control over
the application of load. A control valve provides fine control over the
loading rate for accuracy of pacing. The digital read-out unit, incorporates
a 4 digit display, calibrated in kN and features integral load pacing in
kN/Sec. Maximum load is held and retained for approx 15 min, unless
cancelled, using the panel mounted reset switch. Pace rate set for running
the test can be maintained manually with the help of a bar graph indicator.
