Effect of Retarder on Flexural Properties of Fiber-reinforced Alkali-activated Slag Materials

Abstract

Most research on retarders in alkali-activated slag materials (AASM) has focused primarily on setting behavior, while studies on the flexural performance of fiber-reinforced AASM (FR-AASM) remain limited. However, flexural performance is crucial for the structural design of FR-AASM, especially when retarders are used, as they may not only alter the matrix strength but also the rheological properties, thereby affecting fiber-matrix bond and the distribution and alignment of steel fibers—key factors governing flexural behavior. This study investigates the influence of tetrasodium etidronate (TE) on the flexural performance of FR-AASM to support the accurate design of structural elements incorporating retarders. The rheological performance, setting time, fiber orientation, and compressive strength of FR-AASM made with TE were evaluated. To assess the impact of TE-modified rheology on fiber alignment and distribution, two L-shaped casting molds (90° and 150°) were employed to simulate different flow-induced fiber orientation conditions. The results indicated that using TE reduced the surface charge of ground granulated blast-furnace slag due to the Ca-chelating effects, delaying the crystallization of C-A-S-H in the mixture. This mechanism led to extended setting time and reduced the initial yield stress of FR-AASM. Additionally, compared to conventional casting and 90° L-shaped mold, the 150° L-shaped mold, offering greater flow distance and kinetic energy, significantly enhanced fiber alignment by up to 60 %, resulting in a 42 % improvement in 28-day flexural strength. Furthermore, incorporating 0.3 % TE effectively decreased the yield stress, facilitating improved fiber alignment within the matrix, which in turn enhanced flexural performance. Therefore, when combined with the 150° L-shape-induced casting method, the use of 0.3 % TE significantly promoted fiber alignment along the flow direction, resulting in a remarkable 56 % increase in 28-day flexural strength compared to specimens without TE and cast using the conventional method.

Department(s)

Civil, Architectural and Environmental Engineering

Comments

Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Grant None

Keywords and Phrases

Alkali-activated slag material; Casting method; Fiber orientation; Flexural performance; Rheological property

International Standard Serial Number (ISSN)

2352-7102

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2025 Elsevier, All rights reserved.

Publication Date

01 Oct 2025

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