Flexural Strength test of concrete,its Significance Procedure, applications, IS 516-1959

Flexural Strength test of concrete,its Significance Procedure, applications, IS 516-1959
Flexural Strength test of concrete,its Significance Procedure, applications, IS 516-1959

Flexural strength of concrete beam, casted, stored and cured under specified conditions.

Test Standard: IS 516:1959

Applications of flexural test:

  1. Specifying compliance with standards
  2. It is an essential requirement for concrete mix design
  3. It is employed in testing concrete for slab and pavement construction

Factors affecting of Flexural Test results:

  • Concrete specimen preparation
  • Specimen size
  • Moisture condition of the concrete specimen
  • Curing of the concrete specimen
  • And whether the specimen is molded or sawed to the required size

Test appratus : 

  1. Beam moulds of size 150x150x700mm
  2. Tamping rod of steel 2Kg, 40cm long and ramming face of 25mm square
  3. Flexural testing machine
  4. Scoop
  5. Trowel
  6. Balance with accuracy of 1g
  7. Power driven concrete mixer
  8. Table vibration in the case of using vibration to compact concrete in molds

Sample Preparation of Concrete

  1. Determine proportions of materials including cement, sand, aggregate and water.
  2. Mix the materials using either by hand or using suitable mixing machine in batches with size of 10 percent greater than molding test specimen.
  3. Measure the slump of each concrete batch after blending.
  4. Place molds on horizontal surface and lubricate inside surface with proper lubricant material and excessive lubrication should be prevented.
  5. Pour fresh concrete into the molds in three layers.
  6. Compact each layer with 16mm rode and apply 25 strokes for each layer or fill the mold completely and compact concrete using vibration table.
  7. Remove excess concrete from the top of the mold and smoothen it without imposing pressure on it.
  8. The age of the test is 14 days and 28 days and three specimens for each test should be prepared (according to Indian Code, the specimen is stored in water at 24-30oC for 48hours and then tested)
  9. Test specimens stored in water at a temperature of 24 to 30 degree Celsius for 48 hours before testing

Test procedure :

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 7Kg/cm2/min. The permissible errors shall be not greater than ± 0·5 percent of the applied load where a high degree of accuracy is required and not greater than ± 1·5 percent of the applied load for commercial type of use. The bed of the testing machine shall be provided with two steel rollers 38mm in diameter, on which the specimen is to be supported, and these rollers shall be so mounted that the distance from centre to centre is 600mm for 150mm specimens, The load shall be applied through two similar roller mounted at the third points of the supporting span, that is spaced at 200mm centre to centre.
 
The load shall be divided equally between the two loading rollers and all rollers shall be mounted in such a manner that the load is applied axially and without subjecting the specimen to any torsional stresses or restraints.Test specimens stored in water at a temperature of 24 to 30 degree Celsius for 48 hours before testing, shall be tested immediately on removal from the water whilst they are still In a wet condition. The dimensions of each specimen shall be noted before test. No preparation of the surfaces is required. Minimum of three number of beam specimens are required to be tested at any particular age.

 The bearing surfaces of the supporting and loading rollers shall be wiped clean and any loose sand or other material removed from the surfaces of the specimen where they are to make contact with the rollers. The specimen shall then be placed in the machine in such a manner that the load shall be applied to the uppermost surface as cast in the mould, along two lines spaced 200mm apart. The axis of the specimen shall be carefully aligned with the axis of the loading device. No packing shall be used between the bearing surfaces of the specimen and the rollers. 
 
The load shall be applied without shock and increasing continuously at a rate such that the extreme fibre stress increases at approximately 7Kg/cm2/min. The load shall be increased until the specimen fails, and the maximum load applied to the specimen during the test shall be recorded. 
 
The appearance of the fractured faces of concrete and any unusual features in the type of failure shall be noted.
Flexural Strength test of concrete,its Significance Procedure, applications, IS 516-1959
Flexural strength test of concrete

The flexural strength of the specimen shall be expressed as the modulus of rupture (fb) which if ‘a’ equals the distance between the line of fracture and the nearer support measured on the centre line of the tensile side of the specimen in mm, shall be calculated to the nearest 0.05 N/mm2 as:

fb = (p x l)/(b x d2)

When a is greater than 200mm, or

fb = (3p x a)/ (b x d2)

When ‘a’ is less than 200mm and greater than 170mm, if ‘a’ is less than 170mm, results of the tests shall be discarded.

b = measured width in mm of the specimen, d = measured depth in mm of the specimen at the point of failure, l = length in mm of the span on which the specimen was supported, and p = maximum load in N applied to the specimen.

Flexural Strength test of concrete,its Significance Procedure, applications, IS 516-1959
flexural strength of concrete beam, casted, stored and cured under specified conditions.
Flexural strength test of concrete beam

Spread the love

Rajkumar ghagre

Founder & Admin of civilengineeringsolution.com, I am a civil engineer working as a Assistant Engineer (QA/QC).

Leave a Reply

Your email address will not be published. Required fields are marked *