Browsing by Author "Funda Akbulut, Z."

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The Effects of Waste Iron Powder and Steel Fiber on the Physical and Mechanical Properties of Geopolymer Mortars Exposed To High Temperatures
(Elsevier Ltd, 2023) Funda Akbulut, Z.; Guler, S.; Khan, M.
Geopolymer (GP) concretes have the potential to be an excellent alternative to cement-based traditional concretes for more sustainable concrete production. GP concretes have advantages such as low production temperature, low energy consumption, low carbon dioxide (CO2) emission, and rapid strength gain. However, GP concretes, similar to conventional concretes, lose a large part of their residual strength and durability capacities when exposed to possible high temperatures such as fire due to the deterioration of their internal structures. One efficient way to minimize the loss of strength and durability properties of GP concretes subjected to high temperatures is to use various waste materials and fibers in GP mixtures. This study aimed to improve GP mortar's physical and mechanical properties by adding steel (ST) fiber and waste iron powder (WIP) to GP mixtures. This study fundamentally investigates the spreading diameters (SD), mass loss (ML), external surface changes, residual compressive strength (RCS) and residual flexural strengths (RFS), and microstructural properties of GP mortars reinforced with ST fiber and WIP before and after high-temperature effects. According to the results, although ST fiber and WIP negatively affected GP mortars' workability and reduced GP mortars' SD values, they significantly increased GP mortars' RCS and RFS capacities. At 800 degrees (C), the RCS and RFS capacity reductions of the S0 control sample were 83.30% and 75.27%, respectively. In contrast, the drops in the RCS and RFS capacity of the S6 sample, in which 20% of WIP and 2% of ST fiber were used in hybrid form, decreased by 70.72% and 65.31%, respectively. However, ST fibers and WIP slightly reduced the ML of the GP mortars after the high-temperature effect due to ST fibers and WIP being ineffective in preventing peeling on the sample surface. At 800C, while the ML of the S0 control specimen was 4.47%, the ML values of S1-S6 specimens where WIP and ST fibers were used in single and hybrid forms varied between 4.16% and 4.38%. © 2023 Institution of Structural Engineers
Workability & Mechanical Properties of the Single and Hybrid Basalt Fiber Reinforced Volcanic Ash-Based Cement Mortars After Freeze–thaw Cycles
(Elsevier Ltd, 2023) Guler, S.; Funda Akbulut, Z.
This study examines the workability, mass loss, relative dynamic modulus of elasticity (RDME), residual compressive strength (RCS), and residual flexural strength (RFS) of single and hybrid basalt (BA) fiber-reinforced cement (BAFRC) mortars after freeze–thaw (F-T) cycles. Volcanic ash (VA) was used in all mixtures by replacing 10% with cement. Two micro and one macro-BA fiber were added to cement mortars as single and hybrid forms at 0.5% and 1% volume. All specimens were exposed to 24, 48, and 72F-T cycles in a 3% sodium chloride (NaCl) solution. The changes in the microstructural properties of control and BAFRC specimens after F-T cycles were also examined with scanning electron microscope (SEM) analysis. The results showed significant decreases in all specimens’ mass loss, RDME, RCS, and RFS values after F-T cycles. Although the single and hybrid-BA fibers significantly reduce the workability of the mortars, they are slightly effective in increasing the RCS and RFS capacities of the mortars after F-T cycles. Furthermore, BA fibers contribute a little to reducing the mass losses of the mortar after F-T cycles. In addition, the hybrid use of BA fibers is more effective than single BA fibers in increasing mortars’ RCS and RFS capacities after F-T cycles, as they provide a more robust fiber/matrix interface. © 2023 Institution of Structural Engineers