Details about concrete cube testing
Concrete is frequently utilized for structural application like foundations, columns, beams and floors. So, the concrete should contain adequate strength to bear the loads that will be enforced on it. To verify the eligibility of concrete, a concrete cube test should be conducted for evaluating the compressible cube strength of the concrete and communicating directly to the desired design strength stated by the designer.
Choosing a Sample (Sampling)
It is suggested not to select a sample from the first or last section of the pour as it does not depict the exact representation of the batch. The concrete is normally sampled once the 1st metre of concrete is poured to make sure that a perfect sample is selected. As stated in BS EN 12350-1, select a few samples during the pour for the best demonstration of the batch and ensure you select 150% of what you think to be perfect for requirement.
The sample is chosen and applied to form the cubes. The sample should be a good consistent mix, it may need some mixing after being chosen from the concrete batch to be appropriate for a slump test and cubes.
Slump Test – Slump test should be carried out prior to form your cubes to check the applicability of the concrete. If the slump test does not comply with the range limit as per the British Standard, then the load should be discarded.
Set the damp slump cone on a flat, hard surface. Stuff the cone with the concrete sample in three phases. As soon as each stage is filled, use the tamping rod to tamp the mix 25 times. Once the third tamping is completed, the extra concrete should be struck off flush to the top of the cone. Raise the mould cautiously upwards, to get rid of the commotion of the concrete inside.
The concrete will slump. Set the cone alongside the concrete slump and calculate the variation in height in mm among the top of the cone and the top of the highest point of the concrete.
Also keep record what the slump appear like true (identical shape to the cone), shear (the slump contain sheared in some way), collapse (no similarity to the original cone).
The slump is generally stated by the designer or may be a specific mix to facilitate in placement, i.e. a high slump for a pump mix. Record the slump on the suitable paperwork.
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