ABSTRACT

Reinforced concrete is believed as second most widely used material after water in the world. The fluidity of concrete has made it possible to construct eye catching structures. To ensure serviceability and quality of concrete structures, strength is the one of the parameters which must be checked. For the purpose cubes or cylinders are prepared from the mix being used at site. These cubes or cylinders after proper curing are tested for the strength checking. The standard size of cube is 6"x6", however if unavailable any size of cube mould may be used. If size of cube used is other than standard size, then compressive strength obtained will be different than that of standard size cube. Therefore correction factor must be used to correlate strength of cube being tested with standard size cube.
Therefore an experimental work is carried out to check the effect of various cube sizes and curing age on compressive strength. For this purpose 400 cubes are prepared using I 00 cubes of each size of 4"x4", 6"x6", 9"x9" and 12"x12" cured for 7, 28, 91, and 180 days. The ratio proportions of 1:2:4 with water cement ratio 0.45 is used for all cubes. After completion of curing specimens are tested to determine the compressive strength.
The obtained results of compressive strength are given in tabular and graphical form. In this connection two tables are prepared in for strength correction due to different size (Table 5.9) and curing ages (Table 5.10). These coefficients can be applied to strength results to obtain equivalent strength of cubes of standard size (6"x6") cured
at standard age (28 days).

In both of the tables co-efficient values obtained showed good agreement with theoretical anticipated values except for 9"x9" size cubes which are obtained less than one. On the contrary it must have been greater than one thus might be due less