## 2 Design Methods
### Construction of 1:5-Scaled IBS Components
#### 2.2.1 Materials Properties of the IBS Concrete  
The OPC used complied with the Type I Portland cement, as in ASTM C150-05 [43] and BS12:1991 [44]. Water is one of the most important constituents, and without it, concrete cannot be produced. It should not contain any substance which can be harmful to the process of hydration of cement and the durability of concrete. Water which is acceptable for drinking is also suitable for concrete mixing [45]. Therefore, normal tap water was used to produce the concrete specimens for IBS components casting during the mixing process. Crushed stones obtained from the quarry with a size of less than 5 mm were used as coarse aggregates. According to DOE, the coarse aggregate was air-dried to obtain saturated surface dry conditions to ensure that the water-cement ratio was not affected. Gradation, moisture content, shapes, and texture are some of the characteristics of aggregate, which could affect the workability and bond in the concrete matrix. The gradation was in accordance with the specifications of ASTM C33-03 [46]. Fine aggregate is usually known as sand, which must comply with coarse, medium, or fine grading. The sand used was dried initially in the laboratory oven at the temperature of \(105\pm 5\,^{\circ}\)C. After that, it was sieved accordingly. The sand used was as per the specifications of ASTM C778-02 [47]. The fineness modulus was found to be 2.36 mm. Glenium ACE 388 brand of polycarboxylic obtained from the chemical industry was used as a superplasticizer (SP) for workability, and it was available in the form of a dark-brown liquid. Hence, the amount of Glenium ACE 388 used in this research mixes was 1.2% of the cement volume. The mix design of this research was made to achieve the characteristic strength of 30 N/mm\({}^{2}\) at 28 days of curing for making IBS components. Thereafter, several mixed were made for obtaining the target strength. The materials used were crushed aggregate (4.75 mm), fine aggregate passing 2.36 mm, Ordinary Portland Cement, tap water, and Glenium (Superplasticizer) ACE 388. The concrete mix design proportion was 1: 2: 0.9: 0.42 (cement: aggregate: sand: water). The quantity of Glenium ACE 388 (superplasticizer) used was 1.2% of cement volume. Figure 1(a)-d presents the concrete materials, while Table 1 presents the proportion of concrete materials and the admixture design. It was made based on guidance from the British Research Establishment (BRE). Figure 2: Illustrations of the concrete materials: (**a**) fine aggregate in the oven; (**b**) coarse aggregate; (**c**) Glenium ACE 388; (**d**) mixing process. The downscaled model utilized steel bars with diameters of 6 mm for the main reinforcement and 2 mm as the tie reinforcements. Twelve concrete cylinder samples with the size of 50 mm \(\times\) 100 mm were tested for compressive strength and tensile strength at 7 days and 28 days of curing. Three samples were tested for each material properties test at 7 days and 28 days of curing. The tested samples are shown in Figure 2a-d for compressive strength and splitting tensile strength. Their corresponding properties are tabulated in Tables 2 and 3 as well. The split tensile strength was accomplished according to ASTM C496-96 [48]. The compression and tensile tests were conducted to obtain the concrete's compressive and tensile strength, respectively. Compressive strength was obtained to predict the concrete crush, while tensile strength predicts concrete cracks during laboratory testing. ASTM C39 [49] provides testing procedures to determine the compressive strength and tensile properties of concrete. However, for downscaled models, the selection of smaller-sized control cylinders can have a considerable variation in the compressive strength [50]. The ACI committee 444, Models of concrete structures, recommends the use of 2 \(\times\) 4 in (50 mm \(\times\) 100 mm) cylinders as the standard testing specimen to obtain a characteristic of concrete strength for model studies [51].