# Effect of Aggregate Type on the Shear Behavior of Reinforced Lightweight Concrete Beams
## 1 Introduction  
Lightweight aggregate concrete (LWAC) has been widely utilized in various structures, including floating bridges, oil storage facilities, and offshore structures [1; 2; 3; 4]. The use of LWAC in these applications offers notable benefits, such as enhanced buoyancy-due to the reduced density of the concrete-along with improved durability, soundproofing, and increased fire resistance [5; 6; 7; 8; 9; 10]. Numerous experimental studies have examined the mechanical properties and durability of LWAC, aiming to develop high-strength LWAC suitable for real-world applications in civil structures [4; 11; 12; 13; 14; 15; 16]. Research has shown that using locally produced lightweight aggregates (LWAs) in Brazil as coarse aggregates (CAs) enables the production of LWAC with a compressive strength higher than 50 MPa [4]. The same authors also highlighted the high material efficiency ratio and ductility of LWAC, despite its lower compressive strength compared to normal-weight concrete (NWC). Replacing a lightweight CA with an oil palm boiler linker has been demonstrated to produce LWAC with a compressive strength exceeding 45 MPa [13]. Importantly, similar crack resistance behavior was reported based on comparisons with prestressed NWC beams [13]. Using basalt pumice as a replacement LWA produces structural LWAC with a compressive strength of around 45 MPa [14]. They confirmed the necessity of adding supplementary cementitious materials (SCMs) to ensure suitable properties and recommend using a ternary mixture considering strength development and exposure conditions. The inclusion of lightweight fine aggregate (FA) in concrete can enhance durability, including resistance to water penetration and carbonation, while maintaining strength comparable to concrete containing conventional normal-weight aggregate [11]. As itsapplications expand, LWAC has transitioned from nonstructural to structural uses, proving particularly effective in applications such as increasing the number of stories in high-rise buildings, extending bridge spans, and enhancing the corrosion resistance of offshore platforms [15; 16]. Furthermore, various countries are exploring the production of LWAC using recycled construction wastes and aggregates such as plastics, fly ash, bottom ash, pumice stone, and geopolymers. This trend can be further accelerated by environmental concerns, economic factors, and sustainable development considerations [17; 18; 19]. On the other hand, some studies have pointed out the limitations of using LWAC, highlighting several considerations for practical applications [20; 21]. These limitations can be attributed to the high original porosity of lightweight aggregates (LWAs), which may absorb more water than originally designed or expected. LWAs are typically divided into natural and synthetic types, with expanded slate, shale, and clay being the primary choices for floating concrete structures [22]. However, the use of LWAC requires careful attention to structural design due to its inherent brittleness and in concrete production due to the high water absorption rates of LWAs. There are several existing codes and standards that define LWAC based on measured concrete strength and/or density [23; 24; 25]. For example, ACI 318 classifies LWAC based on a measured compressive strength greater than 17.0 MPa and a density ranging from 1120 to 1920 kg/m\({}^{3}\)[23; 24]. According to EN 1992, on the other hand, LWAC is categorized based solely on density, defined as any concrete with a density of less than 2000 kg/m\({}^{3}\)[25]. In the case of structural applications, reduction or modification factors should be considered depending on the type of structures [23; 24; 25; 26]. Numerous experimental studies have been conducted to investigate the shear behavior of LWAC beams [27; 28; 29; 30; 31; 32]. [PERSON] et al. conducted experiments on the shear ductility of reinforced LWAC beams with concrete strengths ranging from 30 to 90 MPa [27].