*3.1. Experimental Variables*

Experimental variables were GGBFS replacement ratio and curing temperature at 0.60 water/binder (W/B) ratio. Details of these ratios are shown in Table 1.


**Table 1.** The experimental variables.

#### *3.2. Materials*

#### Cement and GGBFS

The cement used in the present study was ordinary Portland cement Type I containing 3.14 g/cm3 specific gravity. Blaine specific surface area of cement was 3230 cm2/g. GGBFS was used according to ASTM C 989 [50] with 2.84 g/cm<sup>3</sup> specific gravity. Blaine specific surface area of cement was 4260 cm2/g. The chemical analysis of these materials are given in Table 2. The chemical composition OPC and GGBFS were carried out by X-ray fluorescence (XRF) instrument.


**Table 2.** Chemical analysis of materials. GGBFS, ground granulated blast furnace slag.

#### *3.3. Mixture Proportions*

The concrete mixture proportion is presented in Table 3. Four types of specimens with different GGBFS replacement ratio were prepared. The mortar was prepared by removing less than 5 mm coarse particle as shown the mixture proportion in Table 3 using 600 Am sieve according to ASTM C33 [51] to maintain the quality of the concrete. Different amounts of superplasticizer were used to equalize the workability of GGBFS and OPC concrete. When we have added the high amount of superplasticizer in GGBFS, the workability was reduced (results are not shown). Therefore, it is required to maintain workability. Hence, we have chosen a different amount of superplasticizer. We have taken the high amount of superplasticizer in OPC (without GGBFS) to mix the concrete properly owing to delay the setting time whereas, in case of GGBFS replacement, specimens were mixed properly even at a low amount of superplasticizer.



\* W = water, C = cement, S = sand, G = coarse aggregates, and SP = Superplasticizer.

#### *3.4. Prepared Specimens*

Firstly, 0.1 m<sup>3</sup> of concrete mix was prepared for each batch. Cement, GGBFS, fine aggregate and coarse aggregate were mixed in a screw type mixer for 1 min and 30 s. Thereafter, water and superplasticizer were added, and the mixture was mixed for 3 min and 30 s. In order to obtain the mortar, the fresh concrete was passed through a 5 mm sieve, and cast into a mold (200 mm × 100 mm) for penetration resistance test according to ASTM C403 [52], whereas, compressive strength of a mold (50 mm × 50 mm × 50 mm) according to ASTM C109 [53]. All specimens were cured at 5 ± 2 ◦C, 20 ± 2 ◦C, 35 ± 2 ◦C and 60% (±2.5%) relative humidity. The curing condition was selected according to ASTM C39 [54].
