*2.3. Specimen Preparation*

A 160 kg capacity pan mixer was used to prepare the concrete. The speed of the mixer was 26 rotations per minute. Cube specimens (100 mm × 100 mm × 100mm) were cast in two layers. After casting each layer, the specimens were compacted using a vibrating table. The vibration was carried out until air bubbles stopped appearing on the surface. The frequency of the vibration was 60 Hz. A plastic sheet was used to cover the specimens in moulds, and these were then kept in casting room for 24 h. The temperature of the room was maintained at 20 (±1) ◦C. After 24 h the specimens were demoulded and placed in water bath for 3 days. The temperature of water bath was maintained at 20 (±1) ◦C. After this, the specimens were sealed in polythene sheets and kept in a storage laboratory until the day of testing. The temperature and relative humidity of the storage laboratory was maintained at 20 (±1) ◦C and 65% ± 1%, respectively.
