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This research aims to improve the durability of high-strength concrete in aggressive environments using recycled materials.

May 7, 2026Open Access

Durability and microstructural behavior of high-strength concrete incorporating recycled steel fibers and ultrafine palm oil fuel ash under acidic and sulfate exposure

Key Points

This research aims to improve the durability of high-strength concrete in aggressive environments using recycled materials.
Incorporated 20% ultrafine palm oil fuel ash and 0.35%, 0.70%, and 1.05% recycled steel fibers by binder weight.
Conducted density, water absorption, and compressive strength retention tests after exposure to sodium sulfate and sulfuric acid for 28 and 90 days.
Used X-ray diffraction and FESEM-EDX for microstructural analysis.
Hybrid mixture with 0.70% recycled steel fibers retained 97.7% compressive strength under sulfate exposure after 90 days.
Under acid attack, the same mix retained 32.4% strength compared to 28.5% for the control mixture.
Microstructural analysis indicated reduced deleterious phase formation and denser C–S–H matrix.

Abstract

High-strength concrete (HSC) exposed to sulfate and acid-rich environments is susceptible to durability degradation due to binder decalcification and the formation of expansive secondary phases. Addressing this durability challenge requires eco-efficient strategies that enhance resistance to chemical attack while reducing environmental impact. This study investigates a hybrid waste-based strategy in HSC, incorporating 20% ultrafine palm oil fuel ash (UPOFA) and waste tire recycled steel fibers (WTRSF) at dosages of 0.35%, 0.70%, and 1.05% by binder weight. The experimental program included density and water absorption measurements followed by visual assessment, mass change, and compressive strength retention after exposure to sodium sulfate (Na 2 SO 4 ) and sulfuric acid (H 2 SO 4 ) solutions for 28 and 90 days. Microstructural evolution was examined using X-ray diffraction (XRD) and FESEM-EDX analyses. Results indicate that the hybrid mixture containing 0.7% WTRSF exhibited the best durability performance, retaining 97.7% compressive strength under sulfate exposure and 32.4% under acid attack after 90 days, compared with 81.5% and 28.5% for the control mixture, respectively. Microstructural analyses confirmed reduced formation of deleterious phases and a denser C–S–H matrix. These findings demonstrate that the synergistic effects of UPOFA and WTRSF can improve durability while reducing clinker consumption, providing a sustainable strategy for high-performance concrete in chemically aggressive environments. • HSC durability degrades under sulfate and acidic environments. • UPOFA-WTRSF hybrid delivers enhanced durability with sustainability benefits. • Optimum mix (0.70% WTRSF + 20% UPOFA) retained ∼ 98 % (sulfate) and ∼ 32 % (acid) strength at 90 days. • Synergy of fiber bridging and pozzolanic reaction improved chemical resistance. • XRD/FESEM-EDX confirmed reduced deleterious phases and denser C–S–H

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Habib et al. (Tue,) studied this question.

synapsesocial.com/papers/69fc2b158b49bacb8b347702 https://doi.org/https://doi.org/10.1016/j.scp.2026.102418

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