SPLITTING TENSILE STRENGTH TEST OF CONCRETE (IS: 516)

SPLITTING TENSILE STRENGTH TEST OF CONCRETE

Tests shall be made at recognized ages of the test specimens, the most usual being 7 and 28 days. Where it may be necessary to obtain the early strengths, tests may be made at the ages of 24 hours ± ½ hour and 72 hours ± 2 hours. The ages shall be calculated from the time of the addition of water to the dry ingredients.Number of Specimens – At least three specimens, preferably from different batches, shall be made for testing at each selected age.

Objective

To determine the tensile strength of concrete

Apparatus

Testing Machine – The testing machine may be of any reliable type, of sufficient capacity for the tests and capable of applying the load at the rate specified in 5.5. The permissible error shall be not greater than ± 2 percent of the maximum load.Cylinders –The cylindrical mould shall be of 150 mm diameter and 300 mm height conforming to IS: 10086-1982 Weights and weighing devices, tool and containers for mixing, tamper(square in cross section) etc.                                                                                                                                                                                              

Sampling Of Material

Samples of aggregates for each batch of concrete shall be of the desired grading and shall be in an air-dried condition. The cement samples, on arrival at the laboratory, shall be thoroughly mixed dry either by hand or in a suitable mixer in such a manner as to ensure the greatest possible blending and uniformity in the material.

Proportioning

The proportions of the materials, including water, in concrete mixes used for determining the suitability of the materials available, shall be similar in all respects to those to be employed in the work.

Weighing

The quantities of cement, each size of aggregate, and water for each batch shall be determined by weight, to an accuracy of 0.1 percent of the total weight of the batch.

Mixing Concrete 

The concrete shall be mixed by hand, or preferably, in a laboratory batch mixer, in such a manner as to avoid loss of water or other materials. Each batch of concrete shall be of such a size as to leave about 10 percent excess after moulding the desired number of test specimens.

Moulding

The cylindrical mould shall be of 150 mm diameter and 300 mm height conforming to IS: 10086-1982.

Compacting Of Concrete

Temping Bar : The tamping bar is a steel bar of 16 mm diameter , 60 cm long and bullet pointed at the lower end.

Hand Compaction

When compacting by hand, the standard tamping bar is used and the stroke of the bar should be distributed in a uniform manner. The number of strokes for each layer should not less than 30. The stroke should penetrate in to the underlying layer and the bottom layer should be rodded throughout its depth. After top layer has been compacted,the surface of the concrete should be finished level with the top of the mould,using a trowel and covered with a glass or metal plate to prevent evaporation.

Curing Of Specimen

The test specimen should be stored in a place at a temperature of 27° +/- 2°C for 24 +/-  0.5 hrs. from the time addition of water to the dry ingredients. After this period the specimen should be marked and removed from the woulds and immediately submerged in clean fresh water or saturated lime solution and kept there until taken out just prior to the test. The water or solution in witch the specimen s are kept should be renewed every seven days and should be maintained at a temperature of 27° +/- 2°c.Concrete cylinder 15 cm diameter &3 0cm long.

NOTE

Cast 6 cylinders (3 for split test &3 for compression test ).

Procedure

• Take the wet specimen from water after 7 days of curing
• Wipe out water from the surface of specimen
• Draw diametrical lines on the two ends of the specimen to ensure that they are on the same axial place.
• Note the weight and dimension of the specimen.
• Set the compression testing machine for the required range.
• Keep are plywood strip on the lower plate and place the specimen.
• Align the specimen so that the lines marked on the ends are vertical and centered over the bottom plate.
• Place the other plywood strip above the specimen.
• Bring down the upper plate to touch the plywood strip.
• Apply the load continuously without shock at a rate of approximately 14-21kg/cm2/minute (Which corresponds to a total load of 9900kg/minute to 14850kg/minute)
• Note down the breaking load(P)

Calculation

As per IS: 456, 

Split tensile strength of concrete.= 0.7Fck

The splitting tensile strength is calculated using the formula :

Tsp = 2P/ pi DL

Where 

P = applied load

D = diameter of the specimen

L = length of the specimen

Therefore,

P = Tsp x pi DL/2

Expected load = P x f.sRange to be selected is…………..

Split Tensile Strength

T = 2P/ pi DL 

Result

Splitting tensile strength of given concrete =……………….N/mm²