1) Cube Test

I. Objective: - To determine compressive strength of concrete\

II. Sample Size : - 150mm X 150mm X 150mm

III. Equipment : - Compression Testing Machine (C.T.M)

IV. Procedure : -

a) Cube moulds of cast iron are oiled from inside so that concrete doesn’t adhere to the mould.

Fresh concrete is poured into moulds in 3 layers and properly compacted with help of

tamping rod with 35 numbers of blows in each layer. The moulds are then kept for 24 hours

for setting of concrete. After 24 hours cubes are removed from the moulds and placed in

water. After 7 days and 28 days of curing, the cubes are tested in compression testing

machine.3 samples are tested after 7 days and other 3 after 28 days.

b) While testing first the cubes are weighed and area of cubes is found. Then cubes are tested in

CTM and max load at which specimen fails is observed. Strength is then calculated as:-

Strength

c) Weight of cube should not be less than 8kg else the cube is failed.

d) Frequency of samples to be prepared as per IS 456

Quantity of Concrete No. Of Samples (Sets)1 – 5 m3 16 – 15 m3 216 – 30 m3 331 – 50 m3 4

51 m3and above4 + 1

additional sample for each additional 50 m3 or part thereof

Results: For M20 Grade concrete used at site, the following results were observed.

For 7 days strengthSample Load (N) Area (mm²) Strength (N/mm²)

1. 420000 22500 18.672. 435000 22500 19.333. 415000 22500 18.44

Average strength = 18.793 N/mm²

For 28 days strengthSample Load (N) Area (mm²) Strength (N/mm²)

1. 660000 22500 29.332. 635000 22500 28.223. 680000 22500 30.22

Average strength = 28.592 N/mm²

2) Slump Test

I. Objective:-To determine Consistency of Concrete Mix.

II. Equipment: - Slump Cone, Tamping Rod, Trowel, Non Porous surface.

Slump Cone is a hollow frustum made of thin

steel sheet with internal dimensions as: top

diameter 100mm, bottom diameter 200mm and

height 300mm.

Tamping Rod is 16mm diameter and 0.6m long

with bullet pointed at lower end.

III. Procedure: - Freshly prepared concrete mix prepared is poured into the slump cone into 4

equal layers each approximately ¼ of the height. Tamp each layer 25 times with the help of

tamping roads distributing the strokes in a uniform manner over the cross-section of mould.

For second layer and subsequent layers tamping rod should penetrate in to the underlying

layer. Strike off the top with a trowel or tamping rod so that mould is completely filled.

Remove the cone immediately, raising it slowly and carefully in vertical direction. As soon

as the concrete settlement comes to a stop, measure the subsidence in mm which will give

the slump.

IV. Results: Slump for M20 measured at site was as follows:

Sample Slump value

1 1½”

2 2”

3 1¾”

V. Precautions: -

a) The strokes are to be applied uniformly throughout the cross section.

b) The cone should be removed very slowly lifting it upward without disturbing the concrete.

The unsupported concrete should be allowed to spread and settle and after settlement the

height should be measured accurately.

c) The experiment should be completed within 3 minutes.

d) Mould and the base plate should be smooth, clean and damp but not wet from inside.

e) Test should be made away from any kind of ground vibrations.

1. Sieve Analysis for Coarse aggregates (20mm and 10 mm size)

I. Objective: - To determine grain size distribution of Course Aggregate

II. Apparatus : - Sieves of size – 40mm, 20mm, 10mm, 4.75mm, Pan; Sieve Shaker

III. Procedure: - Take 10kg of aggregate of nominal size 20mm. The sample shall be brought to

an air-dry condition before weighing and sieving. This may be achieved either by drying at

room temperature or by heating at a temperature of 100°C to 110°C. The air-dry sample

shall be weighed and sieved successively on the appropriate sieves starting with the largest.

Care shall be taken to ensure that the sieves are clean before use. Carry out sieve by hand.

Shake each sieve in order: 40mm, 20mm, 10mm, 4.75mm, over a clean dry tray for a period

not less than 2 minutes. The shaking is done in varied motion over the sieve surface in

frequently changing direction. Find the mass of aggregates retained on each sieve taken in

order. Material shall not be forced through the sieve by hand pressure, but on sieves coarser

than 20 mm, placing of particles is permitted.

IV. Results:

IS Sieve SizeCumulative

weight Retained (Gms.)

Cumulative % Retained

Total Passing

%

% Passing for Acceptable Limits

(as per IS:383; 1970)40mm 0 0 100 10020mm 10 0.5 99.5 85–10010mm 1280 64.0 36 0–20

4.75mm 1924 96.2 3.8 0-5Pan 2000 100 - -

Sieve analysis for Fine Aggregates

I. Objective: - To determine grain size distribution of Fine Aggregate.

II. Apparatus : - Sieves of size – 10mm, 4.75mm, 2.36mm, 1.18mm, 600µ, 300µ, 150µ, Pan;

Sieve Shaker

III. Procedure: - Repeat the same procedure as in case of coarse aggregate. The acceptable

limits of aggregates retained on each sieve should be as follows. For 500gm weight of

sample

IS Sieve Size

Cumulative

Retained

(Gms.)

Cumulative

% Retained

Total

Passing

%

% Passing for Acceptable

Limits (as per IS:383; 1970)

Zone 1 Zone 2 Zone 3

10mm - - 100 100 100 100

4.75mm 8 1.6 98.4 90–100 90–100 90–100

2.36mm 48 9.6 90.4 60-95 75-100 85-100

1.18mm 114 22.8 77.2 30-70 55-90 75-100

600µ 238 47.6 52.4 15-34 35-59 60-79

300µ 384 76.8 23.2 8-20 8-30 8-35

150µ 488 97.6 2.4 0-10 0-10 0-10

PAN 500 - - - - -

Total Cumulative % retained =256.00

Fineness modulus = 2.56