The Influence of Physical Properties on the Durability and Compressive Strength of Fly Ash-Based Geopolymer Mortar under Tidal Acidic Exposure

Ratni Nurwidayati; Akhmad Rizalli Saidy; Nursiah Chairunnisa; Henry Wardhana; . Mariamah

doi:10.48084/etasr.14919

Authors

Ratni Nurwidayati Civil Engineering Program, Engineering Faculty, Lambung Mangkurat University, Indonesia | Agricultural Science, Lambung Mangkurat University, Indonesia https://orcid.org/0000-0001-7927-1206
Akhmad Rizalli Saidy Agricultural Science, Lambung Mangkurat University, Indonesia
Nursiah Chairunnisa Civil Engineering Program, Engineering Faculty, Lambung Mangkurat University, Indonesia https://orcid.org/0000-0002-8092-6369
Henry Wardhana Civil Engineering Program, Engineering Faculty, Lambung Mangkurat University, Indonesia
Mariamah Civil Engineering Program, Engineering Faculty, Lambung Mangkurat University, Indonesia

Volume: 15 | Issue: 6 | Pages: 30196-30203 | December 2025 | https://doi.org/10.48084/etasr.14919

Received: 19 September 2025 | Revised: 17 October 2025 | Accepted: 24 October 2025 | Online: 8 December 2025

Corresponding author: Akhmad Rizalli Saidy

Abstract

The rising demand for cement and electricity has increased carbon emissions and produced large volumes of Fly Ash (FA) waste from coal power plants. Converting this waste into geopolymer mortar provides a sustainable alternative to conventional cement. This study used FA from the Asam-Asam Power Plant, activated with sodium silicate (Na₂SiO₃) and 8M sodium hydroxide (NaOH) in ratios of 1:1, 1.5:1, 2:1, and 2.5:1, with superplasticizer (SP) dosages from 0.1 to 0.3%. Mortar specimens were evaluated for water absorption, porosity, and sorptivity at 28 days and for compressive strength at 28 days and after up to three months of exposure to tidal acidic exposure. At 28 days, compressive strength reached 12.61 MPa. Secondary sorptivity was 0.0008–0.0023 mm s^-1/2 for the geopolymer mixes (minimum at SP3–R1.5) and 0.00071 mm s^-1/2 for the cement mortar; the initial 1–6 h segment satisfied the linearity criterion (r ≥ 0.98) only for the cement mortar (Sᵢ=0.049 mm s^-1/2), indicating a divergence between mechanical strength and capillary transport. Geopolymers showed greater resistance to strength loss under tidal acidic exposure.

Keywords:

geopolymer mortar, fly ash, porosity, sorptivity, tidal acidic exposure

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