Preparation of test specimens
2.3.1. Preparation of concrete cylinders
Cylindrical steel molds of required sizes were used for casting of concrete specimens.
Before concreting, all the molds were oiled first and then placed on the
vibration table. After that, concrete mix was prepared according to the mix design
described in Section 2.2.1 and placed into the molds. The casting of concrete was
done in three layers for 150 mm and 100 mm diameter specimens. For 75 diameter
specimens, the casting was done in two layers. In order to achieve proper compaction
of concrete, low speed table vibration for 30 s was used after pouring each layer
of concrete. All 27 specimens were cast from the same batch of concrete mix to
maintain the same strength of concrete. However, three different size specimens
are not compacted at the same time, only similar size specimens were placed on
the vibration table at a time. All the specimens were covered with plastic sheets
after casting of concrete. The specimens were de-molded after 24 h and placed
under water for proper curing. Non-jacketed specimens were cured for 28 days.
However, the concrete cylinders for jacketed specimens were cured for 14 days
only