Tests Conducted To Check Quality Of Concrete

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Test conducted on site for quality control

Slump test
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 ( i.e. not in middle ) of the base plate on leveled 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.
14. This reading is the amount that the sampled concrete has slumped.
15. If the concrete does not show an acceptable slump, 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.

Compression test
The Compression Test is a laboratory test to determine the characteristic strength of the concrete but the making of test cubes is sometimes carried out by the supervisor on site. This cube test result is very important to the acceptance of insitu concrete work since it demonstrates the strength of the design mix.
The procedure of making the test cubes is as follows: –

1. 150 mm standard cube mold is to be used for concrete mix and 100 mm standard cube mold is to be used for grout mix.
2. Arrange adequate numbers of required cube molds to site in respect with the sampling sequence for the proposed pour.
3. Make sure the apparatus and associated equipment ( see Fig 7 – 6 ) are clean before test and free from hardened concrete and superfluous water .
4. Assemble the cube mold correctly and ensure all nuts are tightened.
5. Apply a light coat of proprietary mold oil on the internal faces of the mold.
6. Place the mold on level firm ground and fill with sampled concrete to a layer of about 50 mm thick.
7. Compact the layer of concrete thoroughly by tamping the whole surface area with the Standard Tamping Bar. (Note that no less than 35 tamps / layer for 150 mm mold and no less than 25 tamps / layer for 100 mm mold).
8. Repeat Steps 5 & 6 until the mold is all filled. (Note that 3 layers to be proceeded for 150 mm mold and 2 layers for 100 mm mold).
9. Remove the surplus concrete after the mold is fully filled and trowel the top surface flush with the mold.
10. Mark the cube surface with an identification number (say simply 1, 2, 3, etc) with a nail or match stick and record these numbers in respect with the concrete truck and location of pour where the sampled concrete is obtained.
11. Cover the cube surface with a piece of damp cloth or polythene sheeting and keep the cube in a place free from vibration for about 24 hours to allow initial set .
12. Strip off the mold pieces in about 24 hours after the respective pour is cast. Press the concrete surface with the thumb to see any denting to ensure the concrete is sufficiently hardened, or otherwise de-molding has to be delayed for one more day and this occurrence should be stated clearly in the Test Report.
13. Mark the test cube a reference number with waterproof felt pen on the molded side, in respect with the previous identification number.
14. Place the cube and submerge in a clean water bath or preferably a thermostatically controlled curing tank until it is delivered to the accredited laboratory for testing.

Checking Quality of Fine Aggregates and Bricks
For checking the quality of fine aggregates, a field test was conducted in which the sand was placed in a flask containing water. The sand was allowed to settle for some time and then after few hours the reading of the silt or other impurity layer is takenIf that reading is less than 5% of the total sand that is put in the flask, then we accept the sand but if it is more than 5% the sand is rejected. Bricks were sent to the college laboratory for testing and thereby checking the quality of the bricks used at site.

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  • vijay December 20, 2011 at 7:56 pm

    my 7 days cube test result fail, but i still have 28 days cube tset, this 28days cube test result can cover the 7 days cube test report.

    • shalini May 1, 2012 at 9:34 pm

      yes to be on safer side check more cubes on 28Th day. how ever v have chemicals to restrengthen the concrete. make sure u get advise from ur seniors

  • hassan aref December 27, 2011 at 8:31 am

    i used C-30 concrete,the results 28 days for cube speciemen are 32,31,28,27.failed or accepted ?

    • m P K February 23, 2012 at 7:15 am

      these results are for individual cubes or set of three cubes???? pl. clarify

    • shalini May 1, 2012 at 9:37 pm

      just take the avg. of 4 cubes. so ur specimen avg is 29.5. i think its good value n not to worry.

      • Nitin September 21, 2012 at 7:06 am

        If the mix is M-30 and if the avg is 29.5, then r u sure tat its good and not a reason to worry.

    • Aanel Jadhav September 24, 2012 at 11:36 am

      the variation should not be more than 15 percent..

    • M.Madhan October 29, 2013 at 2:22 pm

      take the average result.

  • satheesu January 7, 2012 at 6:54 am

    please may i know the various satges of cube when compressing cube(means from started test intial between breaking point after ultimate poing like how many different stages)

  • shahid January 30, 2012 at 5:05 am

    hi.satheesh. compression test of cube is very easy. normally we use universal testing machine (UTM)for this test. place the cube b/w the platform and compressing rod( just like a sandwich). then we start the machine according to the procedure. make sure the needle of machine is starts from zero weight. then the machine starts compressing it. u should notice the load in meter, during the first crack occuring on cube and during the collapse of the cube. ( if any mistakes in this, pls inform)

  • shahid January 30, 2012 at 5:24 am

    the loads are in KN.

  • eng khslid wardak March 13, 2012 at 4:08 am

    dear sir:
    i didn’t find the standered cube so please send me a standered size for cube that i will make it in the site.

  • sudheer March 21, 2012 at 3:15 pm

    hi,about cube testing for 7 days, is 7 days count from concreting day or next day after concreting can you guide me

  • Shankar March 26, 2012 at 9:36 pm

    Dear Genious,
    If the failed cube test failed in the middle of construction, what kind of test we have to do in the building or what are the remedies ?

  • Shankar March 26, 2012 at 9:39 pm

    Dear Sirs,

    What are the different types of testing we have done for concrete & steel ?? please list out all the tests.

  • Akins March 31, 2012 at 5:37 pm

    Good day sir & keep up the good job; I want to ask if 7 days concrete cube test failed & the 28 days test was okay, can the 28 days result be used as a basis for the concrete soundness? If yes, what could have been the possible effect on the 7 days concrete? Thanks

  • Rajkumar July 13, 2012 at 8:28 am

    at which grade of concrte (PCC) cube to taken for testing

  • chaxul July 31, 2012 at 10:10 am

    If water cement rasio high in R.C.C construcion work .how to use concrect for construction

  • Adegbaju David August 16, 2012 at 2:27 am

    Sir,how can an even concrete cover be achieved

  • voloju August 24, 2012 at 12:29 pm

    concrete cubes for class 30 cubes for 7 days various batchs for same element and results are for 3 cubes 14, 16 and 24. poured concrete is accepted or not

  • kaleab tsegaye December 1, 2012 at 6:38 am

    what is the purpose of three days cube test on site work?

  • Udom February 14, 2013 at 4:43 am

    Pls help me, i cast cubes an crush @ 7days i got 19n/mm2 but @ 28days i got 14.5 what is happening pls email me

  • mitesh n maru April 3, 2013 at 5:50 am

    I have level difference. 3to 10 mm In Rcc floor so tell me how much difference. Will be acceptable. Inlevelling as per is code

  • rogin May 9, 2013 at 6:58 am

    i have done the cube test for 3rd day ans 7th day and i got the result as 3rd day 7.4N & 7th day 9.5N. these test are done on single cube. is it safe or should we go for 3 samples for each test for accuracy.

  • vijay bansal May 27, 2013 at 6:26 am

    Sir , can u provide me contact of testing labs in delhi & gurgaon pls ..

  • jas sharma November 25, 2013 at 1:47 am

    what are the field test for concrete leaving slump test behind………………..

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