Earthquake Resistant Building

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EXPERIMENT NO OBJECT: To determine the initial and final setting times of a given cement sample by using Vicat Apparatus. RELEVANT THEORY: Setting Time – In order that the concrete may be placed in position conveniently. It is necessary that the initial setting time of cement is not too quick and after it has been laid, hardening should be rapid so that the structure can be made use of as early as possible. The initial set is a stage in the process of hardening. After which any work that may appear will not re-unite. The concrete is said to be finally set when it is has obtained sufficient strength and hardness. Therefore certain limits for initial and final setting time havbe to specified. APPARATUS REQUIRED: Vicat apparatus with Vicat plunger, Vicat needles and Vicat Mould, Gauging trowel, Measuring Jar (100 to 200 ml) capacity, weighing balance (accuracy 0.05 percent of W), Stop watch, Rice plates, weight box, Rubber gloves and glass plates. PROCEDURE: Initial setting time:- 1. The cement weighing 300 gm. is taken and it is mixed with percentage of water as determined in consistency test. 2. The cement paste is filled in the Vicat mould. 3. The square needle of cross section 1 mm x 1 mm is attached to the moving rod of the Vicat apparatus. 4. The needle is quickly released and it is allowed to penetrate the cement paste. In the beginning the needle penetrates completely. It is then taken out and dropped at a fresh place. The procedure is repeated at regular intervals till the needle does not penetrate completely. The needle should penetrate up to about 5 mm measured form bottom. 5. The initial setting time is the interval between the addition of water to cement and the stage when needle causes to penetrate completely. This time should be about 30 minutes for ordinary Portland cement. Final setting time:- 1. The cement paste is prepared as above

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