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All Journal Civil Engineering Journal
Ekaputri, Januarti J.
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Civil Engineering, Building, Construction & Architecture

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Journal : Civil Engineering Journal

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The Influence of Precursor to Activator Ratio and Curing Temperature on Geopolymer Paste with One-Part Method Widayanti, Ari; Ekaputri, Januarti J.; Amini, Iqlima N.; Petrus, Himawan T. B. M.; Putri, Anandita Ade; Soemitro, Ria A. A.; Handayani, Anjas
Civil Engineering Journal Vol. 11 No. 7 (2025): July
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2025-011-07-014

Abstract

Geopolymer is an eco-friendly material that serves as a sustainable alternative to Portland cement in construction. This binder reduces carbon dioxide emissions from cement production. However, its manufacturing process remains complex and requires professional expertise. This study explores an environmentally friendly cement produced through the “One-Part Method” (or the “just add water” method), which simplifies geopolymer application, making it as user-friendly as Portland cement. However, research on the performance of one-part geopolymers with varying activator contents and curing temperatures remains limited. In this study, Class F fly ash was used as a precursor, combined with a dry activator made from geothermal sludge and sodium hydroxide (NaOH). Two compositions were tested with precursor-to-dry activator ratios of 5:1 (OPG-F5F) and 7:1 (OPG-F7F). The compressive strength was significantly influenced by the Si/Al, Na/Si, Na/Al, and water/solid ratios derived from the precursor and activator. Mechanical properties were analyzed at three curing temperatures: ambient, 40°C, and 60°C. Results showed that OPG-F7F achieved the highest strength at 60°C, reaching 76.1 MPa at 28 days. Mineral analysis before and after steam curing revealed no changes in composition, while morphological analysis indicated that higher temperatures produced a denser geopolymer matrix. These findings demonstrate the strong potential of geopolymer cement as a viable Portland cement replacement using the One-Part Method.
Shear Behavior of Small-Scale Continuous Hidden Beams Using Tied and Spiral Stirrups Ahmed , Mostafa; Ekaputri, Januarti J.; Abdalla , Hany; Elgamal , Ahmed; Youssef , Ahmed
Civil Engineering Journal Vol. 12 No. 1 (2026): January
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2026-012-01-06

Abstract

Hidden beams in reinforced concrete (RC) structures are widely used to meet architectural requirements; however, their reduced effective depth limits shear capacity. This study investigates the shear behavior of hidden beams reinforced with innovative rectangular staggered continuous spiral stirrups, addressing the absence of design guidelines for such reinforcement systems. Nine one-eighth-scale continuous beams were tested under two-point loading, with mortar used to reduce scale effects. The influence of the number, geometry, and configuration of spiral reinforcement was investigated. Both conventional and spiral stirrups significantly improved shear performance compared to the reference beam without transverse reinforcement (HB9-No). Beams with normal stirrups (HB1-N20, HB2-N30, HB3-N40, HB4-N50) increased shear capacity by 115%, 82%, 23%, and 4%, while spiral stirrup beams (HB1-S20, HB2-S30, HB3-S40, HB4-S50) achieved corresponding increases of 174%, 144%, 73%, and 27%, respectively. Overall, spiral reinforcement enhanced shear capacity and energy dissipation by approximately 30% and 46%, respectively, compared with conventional stirrups. Prototype capacities estimated using scaling relationships were compared with international design codes, which were found to be conservative. The findings demonstrate the effectiveness of spiral stirrups in improving shear strength and ductility and emphasize the need to include their contribution in future shear design equations for hidden beams.
Co-Authors Abdalla , Hany Ahmed , Mostafa Amini, Iqlima N. Anandita Ade Putri, Anandita Ade Ari Widayanti Elgamal , Ahmed Handayani, Anjas Petrus, Himawan T. B. M. Ria A. A. Soemitro, Ria A. A. Youssef , Ahmed