1. ER. HIRALAL AGRAWAL EXECUTIVE ENGINEER

2.  Used for determining the Abrasion/LA value of aggregates.  This machine is for determining the resistance to wear off of coarse aggregates/ crushed rock.  This test is alternatively used with Aggregate Impact Value (AIV). But this test is mandatory in case of coarse aggregates used in concrete pavement.  The detail test procedure is covered in IS: 2386 ( Part –IV)

3.  Aggregates which are flaky and/or elongated will often lower the workability of a concrete mix and may also affect long term durability. In bituminous mix, flaky aggregates make for a harsh mix involving extra bitumen and may also crack and break up during compacting/rolling. Hence it is essentially required to check Flakiness Index (FI) & Elongation Index (EI) of coarse aggregates used in various works.  The detailed procedure for determination of FI & EI is given in IS:2386 (Part-I).

4. TEST PROCEDURE

5.  Used for determining standard consistency and setting time of cement.  The standard consistency of a cement paste is that consistency which permit the Vicat Plunger to penetrate to a point 5 to 7 mm from the bottom of the Vicat mould. This parameter is used for finding out initial /final setting time and soundness of cement.  The initial setting time is regarded as the time elapsed between the moment the water is added to the cement, to the time that the paste starts loosing its plasticity. The period elapsing between the time when water is added to the cement and the time at which the Vicat needle fails to pierce the test block to a point 5 +/- 0.5 mm measured from the bottom of the mould shall be the initial setting time.  The final setting time is the time elapsed between the moment the water is added to the cement and the time when the paste has completely lost its plasticity and has attained sufficient firmness to resist certain pressure. The period elapsing between the time when water is added to the cement and the time at which the Vicat needle makes an impression on the surface of the test block while the attachment fails to do so shall be the final setting time.

6. Importance of setting time of cement: In actual construction dealing with cement paste/mortar/concrete, certain time is required for mixing, transporting and placing, during which the mix should be in the plastic condition. Normally a minimum of 30 minutes is given for initial setting time. Once the concrete is placed in the final position, compacted and finished, it should loose its plasticity in the earliest possible time so that it is least vulnerable to damages from external forces. This time, often referred to as final setting time, should not be more than 10 hours.

7.  The compressive strength of hardened cement is the most important property of cement. The strength tests are not made on neat cement paste because of difficulties of excessive shrinkage and cracking. Hence strength of cement is indirectly determined on cement-sand (standard sand) mortar in 1:3 ratio.  The detailed procedure is given in IS: 4031 (Part- 6) – 1988. MORTAR CUBE MOULD VIBRATION MACHINE

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