## 4 Mechanical Test Results and Discussion
### Tensile Behavior
#### 4.2.2 Tensile Strength and Strain Capacity  
The actual tensile strength and strain capacities are summarized in Figure 11. Furthermore, the actual test parameters do not precisely match the averaged curves shown in Figure 10. Figure 11 shows that the substitution of OPC with silica flour, GGBS, and CKD resulted in higher tensile strength at 7 d, whereas SF decreased the tensile strength. Moreover, the strain capacity of the 7 d and 28 d cured specimens was notably improved by substituting OPC with reactive mineral additives. The specimens A7, B7, and C7, which only constituted OPC as a binder, developed tensile strengths of 9.7 MPa, 10.8 MPa, and 10.2 MPa and strain capacities of 1.7%, 1.1%, and 2.6%, respectively. However, specimens D7 and E7, employing GGBS, had tensile strengths of 13.7 MPa and 10.3 MPa, and their strain capacities were higher than that of specimen A7, measured at 2.9% and 2.6%, respectively. This became more significant for the specimens ranging from F7 to I7, consisting of SF and CKD. The specimens F7 and G7, using SF, exhibited tensile strengths of 8.5 MPa and 6.6 MPa and strain capacities of 4.6% and 2.8%, respectively. Moreover, specimens H7 and I7, containing CKD, exhibited the tensile strengths of 11.6 MPa and 10.5 MPa and very high strain capacities of 7.5% and 5.2%, respectively. It was also noted that an increase in the amount of the mineral additives resulted in a decrease in the tensile performance of the specimens ranging from D7 to I7, consisting of GGBS, SF, and CKD. The specimens D7, F7, and H7, with smaller dosages of GGBS, SF, and CKD, exhibited greater tensile strength and strain capacities than that of specimens E7, G7, and I7, respectively. The tensile strength and strain capacity of specimen D7, which comprised 50% of GGBS, was 13.7 MPa and 2.9%, respectively. However, these values decreased to 10.3 MPa and 2.6%, respectively, as the proportion of GGBS was increased to 100% for specimen E7. Similarly, specimens F7 and H7, which contained 20% of SF and 15% of CKD, exhibited tensile strengths of 8.3 MPa and 11.6 MPa and strain capacities of 4.6% and 7.5%, respectively. These values also decreased to 6.6 MPa and 10.5 MPa and 2.8% and 5.2%, respectively, as 10% of the SF and 15% of the CKD substituted the OPC in specimens G7 and I7, as shown in Figure 11.  
Figure 10b also shows the tensile stress-strain curves for the same specimens cured for 28 d in the 40 \({}^{\circ}\)C water tank. Figure 11b summarizes the tensile strength and strain capacities of the five specimens for each variable. All the specimens ranging from A28 to G28 and consisting of OPC, silica flour, GGBS, or SF exhibited considerably improved tensile behavior as compared to the 7 d cured specimens except for specimens H28 and I28 using CKD. The strain-hardening behavior of the specimens ranging from A28 to E28 was extended by over 6.0% and exhibited tensile strengths ranging between 8.2 MPa and 11.6 MPa. Moreover, it is notable that even specimen A28, which only comprised OPC as a binder along with silica sand, attained fine strain-hardening behavior. The specimen  
Figure 10: Tensile stress–strain curves of (**a**) 7 d and (**b**) 28 d cured specimens. A28 exhibited a tensile strength of 11.6 MPa and a strain capacity of 6.2%, respectively. Subsequently, specimens B28 and C28 comprising silica flour had tensile strengths of 8.5 MPa and 10.1 MPa and strain capacity of 6.6% and 7.3%, respectively. Specimens D28 and E2, using GGBS, exhibited a tensile strength of 10.2 MPa and 11.3 MPa and strain capacities of 6.9% and 6.6%, respectively. Specimens F28 and G28, using SF, exhibited relatively low tensile strengths of 8.2 MPa and 8.7 MPa, but high strain capacities of 7.2% and 6.0%, respectively. Moreover, the tensile performance of specimens H28 and I28, using CKD, was also high, exhibiting tensile strengths of 9.7 MPa and 9.6 MPa and strain capacities of 6.8% and 6.9%, respectively.