# Precast Bridges of Bamboo Reinforced Concrete in Disadvantaged Village Areas in Indonesia
## Materials and Methods  
### Materials  
The bamboo used was the petung bamboo (_Dendrocalamus asper_), aged 3-5 years [13; 23]. For the petung bamboo, the bamboo shoots are purplish-black, covered with hairs that are velvety brown to blackish. Petung bamboo is large, with a segment length 40-50 cm, diameter 12-18 cm, and a stem height of up to 20 m. The nodes are surrounded by aerial roots. The wall thickness of the bamboo internode is between 11 and 36 mm, as per [PERSON] (2008) in Wikipedia Indonesia (2016) [2]. The mechanical properties of petung bamboo are shown in Table 1. The tensile test for bamboo petung was based on ASTM D 143-94 [40]. The bamboo part that is taken was 6-7 m from the base of the bamboo stem. The bamboo was cut and split into a bamboo reinforcement size of \(15\times 15\) mm\({}^{2}\). The bamboo to be used must be treated with the following steps: (a) the bamboo must be cut and split close to the size of the bamboo reinforcement to be used, namely 15 mm \(\times\) 15 mm \(\times\) 2000 mm for bridge beam reinforcement, and 15 mm \(\times\) 15 mm \(\times\) 3160 mm for the lower side truss bridge reinforcement. Meanwhile, the reinforcement for the vertical truss is 15 mm \(\times\) 15 mm \(\times\) 1100 mm, the top stem is 15 mm \(\times\) 15 mm \(\times\) 1100 mm, and the diagonal stem is 15 mm \(\times\) 15 mm \(\times\) 1300 mm; (b) the bamboo must be soaked in water for 1-2 months to remove the sugar content and prevent termites and insects, as shown in Figure 3 [9]; (c) it should be dried in free air until the moisture content is approximately 12%, as shown in Figure 4; (d) the bamboo reinforcement should be trimmed with a grinding machine according to the specified size, as shown in Figure 5; (e) one should provide a waterproof layer to reduce the occurrence of the hydrolysis process between the bamboo and concrete, as shown in Figure 6; \begin{table}
\begin{tabular}{c c} \hline \hline
**Mechanical Properties** & \\ \hline Tensile strength (MPa) & \(105\pm 8\) \\ Modulus of elasticity (GPa) & \(26\pm 5\) \\ Elongation of fault (\%) & \(16\pm 1\) \\ Flexural strength (MPa) & \(153\pm 11\) \\ Hardness (VHN) & \(5\pm 1\) \\ Impact strength (J/mm\({}^{2}\)) & \(0.15\pm 0.7\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mechanical properties of petung bamboo [41]. (f) do sand sprinkling to modify the roughness of the bamboo reinforcement, as shown in Figure 7; and (g) stringing the bamboo reinforcement, as shown in Figure 8.  
[PERSON] (2005) [1] and [PERSON] et al. (2014) [13] concluded that the best waterproof layer is Sikadur 32 Gel. [PERSON] (2019) [8] treated bamboo with Sikadur(r)-752 and a hose clamp. The test results show that the adhesion strength increases up to 200% and the beam capacity increases 164% when compared to untreated bamboo reinforcement. The waterproof or adhesive layer used here was Sikadur(r)-752, produced by PT Sika Indonesia [8,27]. Sikadur(r)-752 is a solvent-free, two-component, super-low viscosity liquid, based on high strength epoxy resins--especially for injecting into the cavities and cracks in concrete. Usually used to fill and seal cavities and cracks in structural concrete, Sikadur(r)-752 is applied to the bamboo reinforcement to prevent water absorption. The effectiveness and durability of Sikadur(r)-752 adhesives require further research. The specifications of Sikadur(r)-752 are shown in Table 2. The coating was carried out in two stages. The second waterproof layer was applied to perfect the waterproof layer of the first stage. The thermal effect of Sikadur(r)-752 on bamboo reinforcement can be prevented by the moisture content of 12% in bamboo. In determining the strength of the bamboo, a 12% moisture content in the air-dry condition has been considered as a reference standard [42], and the temperature does not significantly affect the loss of stiffness [43]. Chemical treatment of bamboo helps increase the durability of the bamboo fibers and reduces the moisture absorption of the bamboo fibers [44].