# Effect of Aggregate Type on the Shear Behavior of Reinforced Lightweight Concrete Beams
## 4 Experimental Tests
### Materials and Specim Preparation  
Table 3 shows the concrete mix proportions considered in this study. As summarized in Table 4, Type I ordinary Portland cement (OPC; Sampyo Cement, Seoul, Republic of Korea) and silica fume (SF; Elkem 940U; Elkem, Oslo, Norway) were used to prepare the samples. SF, containing approximately 97% SiO\({}_{2}\) and with a density of 2.27 g/cm\({}^{3}\), was incorporated at a constant replacement ratio of 10% to focus on the impact of different types of lightweight CAs. A polycarbonate-based high-range water-reducing superplasticizer (SP; Flowmix 3000 U; Dongnam, Gyeonggi-do, Republic of Korea) was also utilized. Figure 2 presents the SEM images, and Figure 3 displays the particle size distributions and XRD results of the raw materials.  
Concrete mix proportions for specimen preparation were established by considering the water absorption of LWAs and ensuring the repeatability of targeted properties. The desired strength and density were set at 30 MPa and 1600 kg/m\({}^{3}\), respectively. Both coarse and fine lightweight aggregates were pre-soaked for over 24 h to prevent additional water absorption during mixing and casting, thereby maintaining the expected properties. Excess water was removed from the aggregate surfaces using a dry towel to achieve surface-saturated dry (SSD) conditions. Concrete casting and fresh density measurements were conducted repeatedly to refine the mixtures until they achieved the designed density and ensured proper workability. The total mixing time was set at 5 min based on findings from a previous study [46]. The following details outline the concrete mixing procedure adopted in this study:  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Constituent (\%)** & **OPC** & **SF** \\ \hline CaO & 61.40 & 1.54 \\ SiO\({}_{2}\) & 21.23 & 96.90 \\ Al\({}_{2}\)O\({}_{3}\) & 5.64 & 0.29 \\ Fe\({}_{2}\)O\({}_{3}\) & 3.38 & 0.15 \\ MgO & 2.20 & 0.18 \\ SO\({}_{3}\) & 2.25 & – \\ K\({}_{2}\)O & 1.15 & 0.64 \\ Na\({}_{2}\)O & 0.11 & 0.16 \\ Cl & 0.06 & – \\ MnO & – & 0.03 \\ P\({}_{2}\)O\({}_{5}\) & - & 0.05 \\ Loss of Ignition & 2.58 & 0.05 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Chemical characteristics (in mass %) of raw materials.  
Figure 3: (**a**) Particle size distributions and (**b**) XRD patterns of raw materials.  
Figure 2: SEM images of raw materials: (**a**) OPC and (**b**) SF.  
1. Pre-soaking lightweight coarse and fine aggregates for over 24 h to ensure adequate water absorption and stability.
2. Removing surface water from the aggregates using absorbent cotton towels to achieve SSD conditions.
3. Loading all prepared and measured materials into a drum-type mixer in the following sequence: CAs first, then cement and silica fume, and, finally, sand.
4. Initiating the mixing process by blending for 60 s with half of the total water to ensure an even distribution of moisture.
5. Adding the remaining water along with a high-range water reducer (HRWR) and continuing the mixing for an additional four minutes to achieve the desired consistency and workability of the concrete mix.