3.1 Unit 3 Destructive Tests on Concrete.pptx

Destructive Tests on Concrete.pptx

1. Destructive Tests on Concrete

2. Compression Test (IS 516, IS 456) ASTM C39: cylindrical specimen ( 150mm in dia. by 300mm in length ) Concrete cube mould: 150mm x 150mm x 150mm Tamping Rod : 600mm long & 16mm diameter Casting of specimens with 3 layers of uniform thickness giving 35 tamps to each layer. After 24 hr keep it for curing in the water tank. Test specimens under CTM of capacity 100T after 3,7,28 days. Determine comp.strength= Max.Crushing load/cross sec.area for sample & take average, MPa C om p r ess i v e st r en g t h de p ends on spe c ime n si z e

3. Sampling frequency Table : Sampling frequency for compression testing Quantity of concrete in the Work, m3 (cum.) Number of samples 1-5 1 6-15 2 16-30 3 31-50 4 51 and above 4 plus one additional sample for each additional 50m3 or part thereof Note: A sample consists of 3 cubes

4. Test Acceptance Criteria The test result of the sample shall be the average of the strength of Three specimens. The individual variation should not be more than +/-15% of the average.

5. Split tension test Measures the tensile strength on concrete (ASTM C496) Cylinder is subjected to compressive load along vertical diame t er at a c o n stant r a t e unt il fat i gue F ailu r e o c cur s alo n g v er t i ca l diame t er du e t o t ension developed in transverse direction Split tension is computed by T = 2p/  LD T = tensile strength, MPa (psi) p= load at failure, N (psi) L = length of specimen, mm (in.) D = diame t er of specime n , m m (in.) Tensile strength varies from 2.5 MPa to 31 MPa (360 psi to 450 psi), about 10% of compressive strength

6. Flexure strength test Used for measuring Modulus of Rupture (MR) Important test for road and airport concrete pavements Beam specimen of square x-section is loaded into a 3-point loading apparatus The standard size of the specimen are 15x15x70 cm. If largest nominal size of the aggregate does not exceed 20mm, specimens 10x10x50 cm may be used. Tamping steel bar: L=40cm, with ramming face of 25mm square. Calculation of MR If the fracture occurs in the middle 1/3 of the span R = PL/(bd^2) Where: R = flexure strength, MPa (psi) P = maximum load applied, N (lb) L = span length, mm (in.) b = average width of specimen, mm (in.) a = a v e r a g e dept h of specimen, m m ( in . ) If fracture occurs further outside the middle third, the results must be thrown out

7. Third- point loading method

8. Thank You