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

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1. Introduction Most of the world's daily solid waste is attributed to the construction industry, with concrete waste making up a significant proportion of this waste. Reportedly, the construction industry in Japan produces about 20% of the total industrial waste in the form of concrete waste (Eguchi, 2007). According to Begum (2006), the construction industry in Malaysia generates a significant amount of solid waste every year, which has a negative impact on the environment and causes social problems in the surrounding communities.

Nomenclature RCA

recycled concrete aggregate

w/c

water cement ratio

This waste is estimated to be about 27068.4 tonnes, with concrete and aggregate waste accounting for the largest share of 17820 tonnes or 65.8% of the total construction waste generated. It is increasing every year as 326 tonnes (equivalent to 326,000 kg) of construction waste was disposed of in illegal dumpsites in Kuala Lumpur, Malaysia alone in 2022, which accounted for 94.6% of the total illegal waste generation of 344.3 tonnes in the city (Malaymail, 2023). Excessive generation of construction waste not only causes environmental and social problems, but also leads to depletion of natural resources. Therefore, it is important to manage and reduce the amount of construction waste generated by adopting sustainable waste management practises such as waste reduction, reuse and recycling. This not only benefits the environment and surrounding communities, but also promotes a more sustainable and responsible construction industry. Furthermore, this approach can lead to three major benefits: First, it reduces the demand for new resources; second, it reduces the costs associated with transport and production energy; and third, it enables the use of existing resources. The crushing of construction waste from construction and demolition waste has proven to be a successful method for obtaining recycled aggregates. These recycled aggregates can then be used as substitutes for natural aggregates in the production of new concrete, resulting in the production of recycled concrete aggregates (RCA). RCA is widely regarded as an environmentally friendly or green alternative that offers several benefits, such as reduced negative environmental impact, lower energy consumption and lower construction costs. Several studies have been carried out looking at the use of construction waste such as recycled concrete aggregate at different percentages. For example, Fauzi et al. (2021) conducted a mathematical model to determine the optimum RCA value in the production of controlled low strength materials. Gueneyisi (2023) has used RCA for the fabrication of recycled aggregate filled tubular steel columns (RACFST). It is found that the model based on gene expression programming approach specifically developed for square/rectangular cross-section columns of RACFST is considered a reliable model with consistently high accuracy, stability and repeatability. The RCA has been used for the production of interlocking concrete blocks (Uygunog  lu et al., 2012) and wall panel (Ruslan et al., 2021). Nováková and Mikulica (2016) studied the use of RCA for the production of precast elements and found that 20% RCA as a partial substitute for natural aggregate has no negative impact on the physical and mechanical properties of concrete. Sharma and Singla (2014) studied the properties of recycled aggregates and their similarities and differences with natural aggregates. It was found that the replacement of 100% natural aggregate in concrete may affect chloride ion resistance. However, when the water-cement ratio of the recycled aggregate is reduced, an improvement in tensile strength and modulus of elasticity is observed. Similarly, Shah et al (2021) had studied the replacement with recycled aggregates at 0%, 25%, 50% and 75%. It was found that 33% of recycled aggregate reduces the compressive strength of concrete. Although RCA reduces strength, it can still be beneficial in other applications as the construction industry is constantly looking for new and innovative ways to improve performance and application, such as in the production of interlocking concrete blocks. Interlocking concrete blocks have gained popularity in recent years due to their simple design, structural integrity and cost effectiveness. The interlocking concrete block has been used for various applications, such as pavements (Rathan and Sunitha, 2022; Jamshidi et al., 2019; Olofinnade et al., 2021), as an alternative for brick masonry (Guojue et al. 2017), and as a wall panel (Jeslin and Padmanaban, 2020). The shape of interlocking concrete blocks can greatly