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Slump Test

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This is a site test to determine the workability of the ready mixed concrete just before its placing to final position inside the formwork , and is always conducted by the supervisor on site . However in mid of concreting process , should the site supervisor visually finds that the green concrete becomes dry or the placement of concrete has been interrupted , a re-test on the remaining concrete should be conducted in particular of the pour for congested reinforcement area . The procedure of test in brief is as follows;


1. Ensure the standard Slump Cone and associated equipment are clean before test and free from hardened concrete .
2. Wet the Slump Cone and drain away the superfluous water .
3. Request the mixer or concrete truck to well mix the concrete for additional 5 minutes .
4. Place the Slump Cone on one side ( ie. not in middle ) of the base plate on levelled ground and stand with feet on the foot-pieces of cone .
5. Using a scoop and fill the cone with sampled concrete in 3 equal layers , each of about 100mm thick .
6. Compact each layer of concrete in turn exactly 25 times with a Slump Rod , allowing the rod just passes into the underlying layer .
7. While tamping the top layer , top up the cone with a slight surcharge of concrete after the tamping operation .
8. Level the top by a “ sawing and rolling ” motion of the Slump Rod across the cone .
9. With feet are still firmly on the foot-pieces , wipe the cone and base plate clean and remove any leaked concrete from bottom edge of the Slump Cone .
10. Leave the foot-pieces and lift the cone carefully in a vertical up motion in a few seconds time .
11. Invert the cone on other side and next to the mound of concrete .
12. Lay the Slump Rod across the inverted cone such that it passes above the slumped concrete at its highest point .
13. Measure the distance between the underside of rod and the highest point of concrete to the nearest 5mm ( see Fig 7 – 3 ) .
14. This reading is the amount that the sampled concrete has slumped .
15. If the concrete does not show an acceptable slump ( see Fig 7 – 4 ) , repeat the test with another sample .
16. If the repeated test still does not show an acceptable slump , record this fact in the report , or reject that load of concrete .

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