Effect of NaOH Molarity on Gel Formation at the Geopolymer–Artificial Aggregate Interface for Pavement Applications

Authors

  • Yayan Adi Saputro slamic University of Nahdlatul Ulama Jepara Indonesia
  • Adnan Sarhad University of Science and Information Technology Pakistan
  • Gunawan Mohammad Islamic University of Nahdlatul Ulama Jepara Indonesia
  • Nor Hidayati Islamic University of Nahdlatul Ulama Jepara Indonesia
  • Nando Nilna Muna Islamic University of Nahdlatul Ulama Jepara Indonesia
  • Aprilia Citra Ningrum Islamic University of Nahdlatul Ulama Jepara Indonesia

DOI:

https://doi.org/10.26877/asset.v8i1.3058

Keywords:

geopolymer, interfacial transition zone, alkali activator concentration, hybrid gel formation, artificial aggregate, pavement binder

Abstract

This study investigates the effect of NaOH molarity (10, 12, and 14 M) on gel formation at the geopolymer–artificial aggregate interfacial transition zone (ITZ) for sustainable pavement binder courses. The study focuses on microstructural and chemical characteristics rather than direct mechanical performance. Using XRF, FTIR, and SEM–EDX analyses, the evolution of gel phases from N-A-S-H to hybrid N/C-A-S-H at the interface was systematically characterized. Increasing NaOH molarity enhanced aluminosilicate dissolution and promoted Ca incorporation, as evidenced by the shift of the main Si–O–T band from approximately 1080 cm⁻¹ (10 M) to 960–970 cm⁻¹ (14 M) and the increase in Ca/Si ratio from 0.15 to 0.22. Among the investigated mixtures, the 12 M variant exhibited the most homogeneous and compact ITZ microstructure, characterized by a continuous reaction rim, balanced Si/Al (2.96) and Ca/Si (0.22) ratios, and minimal microcracking observed at the microscopic scale.

Author Biographies

  • Yayan Adi Saputro, slamic University of Nahdlatul Ulama Jepara

    Civil Engineering Program Study, Faculty of Science and Technology, Islamic University of Nahdlatul Ulama Jepara, Jepara, Indonesia

  • Adnan, Sarhad University of Science and Information Technology

    Sarhad University of Sains and Information Technology, Peshawar, 25000, Pakistan

  • Gunawan Mohammad, Islamic University of Nahdlatul Ulama Jepara

    Industrial Engineering Program Study, Faculty of Science and Technology, Islamic University of Nahdlatul Ulama Jepara, Jepara, Indonesia

  • Nor Hidayati, Islamic University of Nahdlatul Ulama Jepara

    Civil Engineering Program Study, Faculty of Science and Technology, Islamic University of Nahdlatul Ulama Jepara, Jepara, Indonesia

  • Nando Nilna Muna, Islamic University of Nahdlatul Ulama Jepara

    Civil Engineering Program Study, Faculty of Science and Technology, Islamic University of Nahdlatul Ulama Jepara, Jepara, Indonesia

  • Aprilia Citra Ningrum, Islamic University of Nahdlatul Ulama Jepara

    Civil Engineering Program Study, Faculty of Science and Technology, Islamic University of Nahdlatul Ulama Jepara, Jepara, Indonesia

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Published

2026-01-30

Issue

Vol. 8 No. 1 (2026): November - January

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Articles

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