Things to Consider Before Doing Concrete Compression Test

Concrete compression testing is performed to determine the compressive strength of concrete. It is probably the most performed and most widely used and known concrete testing methods. The test involves crushing a test cylinder in a compression testing machines and recording the ultimate strength at failure.

AS1012.8.1 Chapter 7 gives guidance on the moulding of lab specimens. Rodding or tamping cannot be used on samples with slump less than 40mm. In those circumstances vibration must be used.  Care must be taken with specimens of concrete with slump greater than 100mm to ensure segregation does not occur.
The procedure for the compaction by vibration of specimens shall be as follows:
(a) Fill the moulds in two approximately equal layers.
(b) Vibrate each layer until the surface becomes relatively smooth in appearance. Vibration should not be prolonged beyond the point at which mortar commences to collect on the surface.
(c) Place sufficient concrete in the top layer, to overfill the mould when compacted; however, if the mould is not completely filled after partial compaction of the top layer, add some additional concrete and complete compaction.
(d) Strike off and smooth the surface of the concrete. Avoid a mirror finish.

In terms of preparing the test cylinders Australian Standard 1012 states:

Standard moist-curing conditions ensure that the concrete specimens made in the laboratory or in the field are kept wet and at a temperature of—

(a) 23 ±2°C, for the Standard Temperate Zone; or
(b) 27 ±2°C, for the Standard Tropical Zone.

Standard moist-curing conditions shall be provided by storing the specimen in lime-saturated water or in a fog room. Temperatures shall be recorded continuously, or the limits of temperature shall be recorded by a maximum/minimum thermometer.

The conditions shall be maintained at all times so that the specimens are kept within the appropriate temperature range specified in this Clause and so that the surfaces of the specimens are kept wet.

Take measurements of the concrete specimens by calculating their cross sectional area. Also take note of these measurements as they will affect the stress calculated.

Using an automated compression test machine the test itself should be fairly simple:
Set test parameters, including pace rate
Pressing the START button on the control unit
The machine automatically starts the rapid approach; switches the test speed after 1% of the load capacity of the machine, and stops once the specimen fails
The system will automatically save the test parameters and results
Location: 326 Keilor Rd, Niddrie VIC 3042, Australia

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