What are the initial and final setting times of cement ? How are they experimentally determined ?
Initial Setting Time:-
It is regarded as the time elapsed between the moment that the water is added to cement to the time that the paste starts losing its plasticity.
Water added 
85 % of P = 0.85;
Plunger 1 mm sq. plunger (Vicat’s apparatus)
Minimum time 30 mins.
Final Setting Time:-
It is defined as the time elapsed between from adding water to the time that the paste completely looses its plasticity.
Plunger 1 mm circular Plunger.
Maximum time 10 hrs.
What are flaky and elongated aggregates? How can the shape of aggregate influence strength of concrete? Following is the result of a sieve analysis of 500 gm aggregate:
| IS sieve size | 10 mm | 4.75 mm | 2·36 mm | 1·18 mm | 600 micron | 300 micron | 150 micron | lower than 150 micron |
| Weight retained in gm | 0 | 10 | 50 | 50 | 95 | 175 | 85 | 35 |
Find out the 'Fineness Modulus' of the sample
Explain Kelly Ball to measure the workability of concrete. Mention the limitation of the test.
What is an air entraining agents? Give some examples. What is efflorescence in concrete structure?
Give the physical characteristics of 53 grade OPC.
