Comprehensive study of pumice and mica in geopolymer mortar as GGBFS replacement on mechanical, durability, high-temperature, and sustainability performance
Date
2025
Authors
Sadrmomtazi, A.
Gholamhoseinzadeh, S.
Darvishalinezhad, A.
Gholizad, A.
Sheijani, A.R.J.
Khoshkbijari, R.K.
Yahyaee, T.
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Journal article
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Construction and Building Materials, 2025; 494(143410):1-17
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Abstract
Geopolymer mortars offer a sustainable alternative to cement-based materials, utilizing industrial by-products such as ground granulated blast-furnace slag (GGBFS) to enhance strength and durability. The incorporation of pumice and mica as supplementary cementitious materials (SCM) can further improve mechanical properties and durability. This study investigates the effects of pumice and mica powders as partial replacements for GGBFS in geopolymer mortars. Twenty mortar mixtures were prepared with sodium hydroxide (NaOH) concentrations of 4 Mol and 8 Mol, incorporating 5 %, 10 %, and 15 % pumice or mica. Mechanical performance was assessed through compressive, flexural, and direct tensile strength tests at 7, 28, and 90 days, while durability and microstructure of samples were evaluated via water absorption, electrical resistance, thermal resistance (100 degrees C-600 degrees C), microstructural analysis using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Also, environmental and cost analyses were conducted to assess CO2 emissions and material costs. Results showed that 5 % mica substitution enhanced early-age compressive strength by around 5 % compared to the control sample. Mica and pumice also significantly improved the thermal resistance of geopolymer mortars, with residual compressive strength at 600 degrees C increasing by up to 54 % compared to the control sample. Adding mica and pumice, flexural strength increased by 14.7 %, and direct tensile strength followed a similar trend, particularly in higher NaOH concentrations. Additionally, mica and pumice reduced water absorption, whereas electrical resistance tests indicated a denser microstructure in control samples. SEM analysis confirmed the formation of stable Ca-(N)-A-S-H geopolymer phases, supporting the feasibility of pumice and mica as supplementary materials for improving geopolymer mortar performance at ambient and high temperatures. Environmental analysis revealed that incorporating mica and pumice reduced CO2 emissions, while cost analysis demonstrated that pumice substitution lowered material expenses, whereas mica replacement led to higher costs. These findings demonstrate that incorporating pumice and mica can enhance the mechanical and thermal properties of geopolymer mortars while reducing environmental impact, offering a sustainable and costeffective alternative for construction materials.
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Copyright 2025 Published by Elsevier