PSI - Issue 47

Noorsuhada Md Nor et al. / Procedia Structural Integrity 47 (2023) 732–743 Md Nor et al./ Structural Integrity Procedia 00 (2019) 000–000

739

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of the specimen was 5.33 N/mm 2 and 2.45 N/mm 2 for solid and one- hollow concrete blocks respectively. This means that the higher ultimate load indicates that the block can withstand greater external forces and loads, which is crucial for the longevity and safety of the structure. From these values it can be seen that the strength of the solid block is higher than that of the one-hollow interlocking block. This is because the void in the middle of the block reduces the ultimate load and the strength of the block. Furthermore, the presence of voids in a hollow block reduces its overall stiffness and makes it more susceptible to bending under load. The difference between the two blocks is 54.13%. Although the difference in strength is very large when comparing the two, the one-hollow interlocking block is very useful for the purpose of the partition wall, which has a low load-bearing capacity compared to other parts of the building. Fig. 8 shows that the ultimate load of the concrete block increases with the age of the block. Similarly, as can be seen in Fig. 9, the flexural strength increases as the composite block ages. Similar results were also obtained by Uygunog lu et al. (2012), who found that the strength of composite blocks with fly ash increased with increasing age of the block up to 28 days. Fig. 10 shows the relationship between strain and deflection for solid and one-hollow interlocking blocks at 7, 14 and 28 days of age. It is clear from the figure that the maximum deflection of the one-hollow interlocking block is higher than that of the solid interlocking block. The maximum deflection after 7 days was 0.048 mm and 0.072 mm for the solid and hollow blocks, respectively, with a difference of 50% (Fig. 10 (a)). The deflection increased at 14 days with a value of 0.097 mm and 0.142 mm for solid and hollow blocks with a percentage difference of 46.40% (Fig. 10 (b)). Deflection increased at the optimum age of 28 days with a value of 0.39 mm and 0.492 mm for solid and one-hollow blocks respectively as shown in Fig. 10 (c). The percentage difference at the optimum age is 26%. This phenomenon indicates that the deflection is due to the bending or sagging of the interlocking block under load, which is influenced by a variety of factors such as the material properties, geometry and boundary conditions of the block. The main difference between solid and hollow blocks lies in their geometry. Hollow blocks have empty spaces or voids inside them, while solid blocks are completely filled. The presence of these voids in the single-hollow interlocking blocks can lead to higher deflection compared to solid interlocking blocks for several reasons. First, the void reduces the overall stiffness of the block, making it more susceptible to bending under load. Secondly, the presence of the cavities can lead to stress concentrations in the block, which can cause local bending and deflection. Finally, the hollows in the centre of the block along the depth can also reduce the ability of the block to resist shear forces, which can also contribute to deflection. In summary, the higher deflection of hollow interlocking blocks compared to solid interlocking blocks is primarily due to their lower stiffness and lower ability to resist shear forces caused by their voids.

Table 1. The average strength of the interlocking concrete block containing 50% of RCA.

Performance

Interlocking concrete block

Age of specimens (days)

7

14

28

Ultimate load (N)

Solid

6085.32 2095.31

5912.16 6023.40

14455.23 6630.21

One hollow % difference

65.57

1.80 2.18 2.22 1.83

54.13

Flexural strength (N/mm 2 )

Solid

2.24 0.77

5.33 2.45

One hollow % difference

65.63

54.03