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A B S T R A C TAlkali-activated ladle slag (AALS) is a promising cementitious material with environmental benefits. However, the brittleness of material has been limiting the use in construction. Therefore, in this experimental investigation, different polypropylene (PP) fibers were employed as a short randomly reinforcement in cementitious matrix in order to improve mechanical performance of the AALS composites.The study reveals that the AALS composite could gain very high ductility with an appropriate fibrous reinforcement. Fracture energy and fracture toughness of PP fiber reinforced AALS mortars increased by approximately 150 and 7.6 times, respectively, compared to the unreinforced material. Additionally, the flexural strength of the composite increased by roughly 300%. Pseudo strain hardening (PSH) behavior was observed along with multiple cracks under uniaxial tensile test. Scanning electron microscope (SEM) images confirmed the local fiber bridging effect, which resulted in the high mechanical performance of the PP-reinforced AALS.

Ladle slag (LS) is a byproduct from the steel industry that is usually reactive on its own and hydrates towards cementitious phases when mixed with water. However, these reaction products are often metastable, leading to micro-structural changes between 7 and 30 days after mixing. To address this issue, in this experimental investigation, a new binder was designed where LS was mixed with gypsum in order to deliver an ettringite-based binder (LSG). The experimental results revealed that the dominant crystalline phase of LSG was ettringite, which 2 remained stable with no conversion at later stages. For better understanding of the ettringitebased binder, mortar characterization, mechanical properties, and durability of LSG were investigated. LSG showed good mechanical properties and excellent freeze-thaw resistance after 300 cycles, which is comparable to other calcium sulfoaluminate cements. Therefore, as a result, the byproduct-based ettringite binder synthesized herein could offer a solution to steelmaking byproducts with a low-CO2 binder, which could be used in a wide range of applications in the construction industry.

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