Rigid polyurethane (RPU) foams as roof insulation have become increasingly popular in Southeast Asian countries and have been extensively used for absorbing sound and reducing noise because of their good sound damping, viscoelasticity, and low density. In this study, the RPU foam composite reinforced bamboo fiber was investigated by physical characterization by SEM, TGA, and FTIR, and the sound absorption was measured by the Impedance Tube Test. The morphology result of the RPU foam composite indicates the size of the diameter pore influenced the sound absorption by adding bamboo fiber as a filler. The thermal degradation of the presence of lignin in the bamboo fiber at the temperature range of 400 °C to 500 °C and the total weight loss is 76 % at 429 °C temperature. FTIR spectrum shows that the peak at 2890 to 2935 cm-1 are indicated –CH stretching vibrations and characteristics for bamboo fiber can be used in polymer composites. The sound absorption of RPU 25 foam composite reinforced bamboo fiber was found 0.74 absorbance at a frequency of 1250 Hz. RPU foam reinforced bamboo fiber as a filler has the highest transmission loss RPU 35 is 21 dB at a frequency range of 1600 Hz. The findings indicate by increasing the content of bamboo fiber as filler, the diameter of the open pore of RPU 25 and RPU 35 foam composite had the potential for sound absorption to absorb at low frequency to achieve greater sound absorption for roof insulation.

The performance of roof insulation such as polyurethane decreased due to problems such as insufficient absorption and poor thermal insulation performance, especially during rainstorms. The aims of this study are to investigate the physical property and its potential reinforced material such as rigid polyurethane doped with treated and untreated bamboo fiber composite (RPU-BF) at different ratios of 0, 25, 30, 35, and 40% of bamboo fibers as an insulation material for roof applications. The bamboo fibers were treated by using silane coupling agent treatment. The rigid polyurethane composite samples were prepared and then laminated bamboo fiber to overcome the sound problem in roofs. The physical characterization was investigated by Water Contact Angle (WCA), the morphological by Scanning Electron Microscopy (SEM), Thermo-gravimetric Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR) Analysis. The results showed that the treated bamboo fiber had a 192.5° water contact angle as a super hydrophobic property due to the presence of the chemical bonds Si-O-Si and Si-O-C in the silane coupling agent treatment. The morphology showed that 30% ratios of RPU-BF-T30 give the smallest pore diameter size. The peak of thermal degradation temperature of untreated and treated bamboo fiber was increased from 320°C to 350 °C with a weight loss of 80% to 50%. The treated bamboo fiber exhibited peaks at 3010–3040 cm-1 were associated with stronger Si-O-Si bonding, indicating the formation of new chemical bonds between bamboo fiber and silane coupling agent due to the ester bond from the cellulose, lignin, and hemicellulose. Thus, there was a similar trend peak in the functional chemical group in the FTIR spectrum of the RPU-BF composite. This result shows that RPU-BF composite had the potential of the optimum ratio of bamboo fiber as an insulation material for local communities and beneficial to the bamboo industry.

This study investigates the shear behavior of reinforced concrete beams constructed with high-calcium fly ash-based Ultra-Low Carbon Concrete (ULCC) as a sustainable alternative to conventional Portland Cement Concrete (PCC). The objective is to assess ULCC’s structural performance under shear and its potential as a low-carbon substitute. Using a dry-mix method with dry activators, six beams (five ULCC, one PCC) of identical dimensions (150 × 250 × 1800 mm) were tested under four-point bending, with variations in shear reinforcement, flexural reinforcement, and shear span-to-depth (a/d) ratios. Digital Image Correlation (DIC) was employed to monitor crack propagation and strain development, while Finite Element Modeling (FEM) provided numerical validation. Results show that increasing shear reinforcement enhanced capacity by 12.05%, whereas higher (a/d) ratios decreased it by 22.63%; increased flexural reinforcement improved shear resistance by 31.27%. FEM closely matched experimental outcomes, with a load-deflection ratio of 1.01. ULCC outperformed PCC in shear capacity and exceeded ACI 318-19 predictions. The integration of DIC and FEM offers a comprehensive analysis framework, and the findings demonstrate ULCC’s viability as a structurally efficient, environmentally sustainable alternative for shear-critical applications.

NUMERICAL ANALYSIS STUDY OF THE EFFECT GEOPOLYMER CONCRETE COMPRESSIVE STRENGTH ON DUCTILITY OF REINFORCED CONCRETE BEAMS

Desa Sumberrejo menghadapi dua permasalahan utama yakni, akses jalan yang buruk dan dampak limbah dari PLTU Paiton. Akses jalan yang tidak layak memerlukan renovasi, sementara limbah Fly Ash dan Bottom Ash (FABA) dari PLTU menyebabkan masalah lingkungan dan kesehatan. PLTU Paiton menghasilkan 75% fly ash dan 25% bottom ash dari pembakaran 250 ton batu bara per jam, yang berdampak pada kerusakan hasil panen serta berpotensi menimbulkan masalah kesehatan. Meskipun demikian, uji karakteristik FABA menunjukkan bahwa limbah ini termasuk dalam kategori Limbah Non B3 Terdaftar dan aman digunakan sebagai pengganti semen dalam pembuatan paving block. Penggunaan FABA dalam paving block dapat meningkatkan kekuatan, mengurangi konsumsi air, dan berdampak positif bagi lingkungan. Rencana optimalisasi pemanfaatan FABA mencakup sosialisasi dan pendampingan kepada masyarakat Desa Sumberrejo untuk mengolah limbah menjadi paving block. Inisiatif ini dapat memberikan pengetahuan untuk mengatasi masalah akses jalan, meminimalisasi dampak FABA, dan meningkatkan perekonomian desa. Studi lebih lanjut diperlukan untuk memahami karakteristik FABA, terutama terkait konduktivitas panas sinar matahari. Dengan upaya ini, Badan Usaha Milik Desa Sumberrejo (BUMDes) dapat memanfaatkan limbah PLTU secara berkelanjutan, meningkatkan produktivitas, dan menjaga lingkungan serta kesehatan masyarakat.