Care has to be taken to ensure that the sulfur compound is not over-heated, as it will not then develop the required compressive strength. Sulfur caps are allowed to harden for at least 2 hours before applying the load.
5.4 Testing of specimen
5.4.1 Cylinder test for compressive strength
5.4.1.1 Apparatus
The testing machine used to test the compressive strength of concrete cylinder was a hydraulically operated testing machine of 3000 KN capacity. The rate of loading for this test was controlled at the rate of 10 KN/sec.
5.4.1.2 Test procedure
Compressive strength of moist cured specimens was made after removal from the curing basin. For the uniform load distribution over the bearing area of specimen, sulfur capping was used on both the bearing surfaces of each specimen.
5.4.1.3 Placing of specimen
The lower bearing plate was placed with its hardened face up on the table of the testing machine directly under the upper bearing plate [6]. The bearing faces of the test specimen were wiped clear and the test specimen was placed on the lower bearing plate. The axis of the specimen was carefully aligned with the centre of the upper bearing plate.
5.4.1.4 Crushing of the specimen
The load was applied continuously without shock. It was applied at a constant rate of 10 KN/sec. No adjustment was made in the controls of the testing machine while a specimen was yielding rapidly, immediately before failure. The compressive strength of concrete was calculated, dividing the maximum load carried by the specimen by the average cross sectional area of the specimen.
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