What question did this study set out to answer?

Assess the flexural behavior and crack development of reinforced geopolymer concrete slabs with voids compared to solid slabs.

May 26, 2026Scientific Reports0 citationsOpen Access

Flexural behavior and crack development of reinforced geopolymer slabs with longitudinal voids: an experimental study

YAYasmin Hefni Abdel Aziz AMAbeer El Malky TETaha A. El-Sayed

Key Points

Assess the flexural behavior and crack development of reinforced geopolymer concrete slabs with voids compared to solid slabs.
Conducted four-point loading tests on seven slabs including two solid (OPC and GC) and five hollow-core GC slabs.
Examined varying void sizes and shear-span-to-depth ratios (a/d) to evaluate cracking and flexural capacity.
Applied traditional flexural theory for analytical predictions and comparisons with experimental data.
The geopolymer concrete solid slab showed better flexural performance than the OPC slab with improved bond properties (p<0.05).
Hollow-core slabs exhibited decreased cracking load and flexural capacity as void ratios increased, impacting stiffness and deflection.
Reduced shear spans enhanced load capacity and stiffness, while longer spans resulted in increased deflection.

Abstract

Abstract Geopolymer concrete, produced from the alkali activation of aluminosilicate-rich by-products such as fly ash, presents a sustainable, low-carbon substitute for standard Portland cement. Despite its acknowledged mechanical and durability advantages, researchers have not thoroughly examined the flexural performance of reinforced GC slabs particularly hollow-core designs. This paper offers a comprehensive experimental and theoretical assessment of reinforced GC solid and hollow-core slabs to fill this gap. Seven slabs were tested under four-point loading tests: two solid specimens (OPC and GC) and five hollow-core GC slabs featuring varying void sizes and shear-span-to-depth ratios (a/d). The investigation concentrated on reaction to cracking, ultimate flexural capacity, stiffness characteristics, and deflection behavior, facilitating a systematic evaluation of both material and geometric effects. The results indicate that the GC solid slab exhibited marginally superior flexural performance compared to the OPC slab, demonstrating advantageous bond properties and material uniformity. In hollow-core slabs, elevated void ratios resulted in significant decreases in cracking load, ultimate capacity, and effective stiffness, whereas alterations in a/d caused pronounced differences in strength and deflection characteristics. Reduced shear spans improved load capacity and stiffness, while extended spans led to a more pliable load–deflection response. Analytical predictions derived from traditional flexural theory closely aligned with experimental outcomes, validating the appropriateness of classical models for GC and voided slab systems. The results show that geopolymer concrete is a structurally sound and environmentally friendly alternative to regular Portland cement (OPC). Its efficacy in both solid and hollow-core configurations facilitate its wider implementation in contemporary low-carbon structural applications.

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