Soundness.pptx

Soundness

1. Applied Mechanics Department Government Polytechnic Rajkot Gujarat, India Concrete Technology Lab Soundness of the Cement Satwik P. Rayjada

2. 2 Concrete Concrete = Cement + Course aggregate & Fine aggregate + Water + Admixtures Cement Aggregate Concrete Reinforced Concrete Existing Concrete

3. 3 Laboratory test of Cement Physical Property Tests Chemical composition test: To compounds such as SO 3 , Chlorides, Alkalies etc. are within the permissible limits Test Significance Fineness Affect rate of reaction. Heat of hydration, rate of gain of strength Setting Time For workability Strength Amount of l oad cement can take Soundness Change in Volume Heat of Hydration Important for majorly for mass concreting Standard Consistency of Cement

4. 4 Soundness of Cement Soundness of cement can be defined as its ability to retain its volume after it gets hardened . It is very important that cement after setting shall not undergo any appreciable change the volume as this produces cracks in the concrete. Unsoundness in cement is due to excess of lime ( CaO ) and excess of magnesia ( MgO ) . Sometimes due to excessive proportion of sulphates .

5. 5 Soundness of Cement Unsoundness of cement does not come to surface for a considerable period of time. Hence, accelerated methods are required to detect it. Autoclave Method Le C hatelier’s Method (IS: 4031 – 1968) The Le Chatelier test detects unsoundness due to free lime only. Autoclave test is sensitive to both free magnesia and free lime.

6. 6 Soundness of Cement : Le Chatelier’s Method The hydration of free lime is accelerated by boiling which causes the expansion of cement. It is this expansion of time which is one of the causes of cracking of cement concrete. This expansion is measured which should not be excessive.

7. d . 7 Soundness of Cement - Le Chatelier’s Method : Apparatus Apparatus Le chatelier’s mould Glass plates Weights Water bath Two trowels Spatula Vernier scale b . a. c. e. f . g.

8. 8 Soundness of Cement - Le Chatelier’s Method : Procedure Take 50g of neat cement sample to be tested and transfer it on a glass plate Add to it 0.78 times the water required to give a cement paste of standard consistency ( P ) and mix thoroughly with the help of two towels . The time of gauging should not be less than 3 minute not more than 5 minutes and gauging shall be completed before any signs of setting occur 50gm 0.78 × P

9. 9 Soundness of Cement - Le Chatelier’s Method : Procedure    

10. 10 Soundness of Cement - Le Chatelier’s Method : Procedure Place the paste in Le chatelier’s apparatus resting on a glass plate. Cover the mould with another glass plate and place a small weight on this covering Glass plate Weight Le Chatelier’s Apparatus

11. 11 Soundness of Cement - Le Chatelier’s Method : Procedure Immediately submerge the whole assembly in water for 24 hours at temperature of 27 º ± 2 ºC . Measure the distance between A-A - distance separating the indicator points ( D 1 ) Weight Le Chatelier’s Apparatus After Water bath

12. 12 Soundness of Cement - Le Chatelier’s Method : Procedure Bring the water to boiling, with the mould kept submerged, in 25 to 30 minutes , and keep it boiling for three hours. Remove the mould from the water, allow it to cool Measure the distance between A’-A’ ( D 2 ) Weight Le Chatelier’s Apparatus After boiling A ’ A ’

13. 13 Soundness of Cement - Le Chatelier’s Method : Procedure Weight Le Chatelier’s Apparatus After Boiling A ’ A ’ Weight Le Chatelier’s Apparatus After Water Bath Difference should be less than 10 mm Distance between A’-A’ ( D 2 ) Distance between A-A ( D 1 )

14. Soundness of Cement - Le Chatelier’s Method : Procedure

15. 15 Soundness of Cement - Le Chatelier’s Method : Observation Table Weight of cement = 50 g ; Consistency ( P ) = 32 % Weight of Water = 0.78 × P × 100 × 50 g= 13 g Sr no. Distance between two pointers Before Boiling( D 1 ) After Boiling( D 2 ) Expansion D 2 - D 1 (mm) Avarage Expansion 1 13 18 5 2 14 23 9 7 3 13 20 7 Soundness of given cement sample is found to be __7__ mm

16. Applied Mechanics Department Government Polytechnic Rajkot Gujarat, India Concrete Technology Lab Soundness of the Cement Satwik P. Rayjada Thank You !!