Browsing by Author "Lachemi, M."

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Effect of Macro Polypropylene, Polyamide and Steel Fibers on the Residual Properties of Scc at Ambient and Elevated Temperatures
(Elsevier Ltd, 2021) Guler, S.; Akbulut, Z.F.; Siad, H.; Lachemi, M.
This paper considers the effect of equivalent macro size fibers of polypropylene (PP), polyamide (PA) and steel (ST) on the properties of reinforced self-compacting concrete (FRSCC) exposed to normal and elevated temperatures. Different fiber concentrations of 0%, 0.3%, 0.6% and 1% were investigated under temperatures of 20 °C, 300 °C, 500 °C and 800 °C. Mass loss, residual compressive strength (RCS), residual flexural strength (RFS), toughness indices (TI), residual strength factors (RSF) and residual toughness (RT) capacities of FRSCCs were studied at hardened state based on their initial results at ambient curing. Meanwhile, slump-flow diameter, T500 time and L-box parameters were also tested at fresh state. In addition, the microstructural changes due to the use of various fibers and temperatures were examined by scanning electron microscope (SEM) analysis. The effect of macro PA and PP was comparable in terms of their minor influence on the mass loss, RCS and RFS of FRSCC compositions. However, macro PA presented greater contribution than PP in preserving the toughness capacity, particularly in the post-peak stage. Unlike PA and PP, the use of macro ST fibers caused noticeable increments in RFS and RT capacities. The superior outcome of using macro ST was confirmed through its higher effect in mitigating the crack formation of FRSCC, especially under elevated temperatures of 500 °C and 800 °C. © 2021 Elsevier Ltd
Enhanced Freeze-Thaw Resilience of Cement Mortars Through Nano-Sio2 and Single/Hybrid Basalt Fiber Incorporation: Assessing Workability, Strength, Durability
(Elsevier Ltd, 2024) Guler, S.; Akbulut, Z.F.; Siad, H.; Lachemi, M.
This study investigated how freeze-thaw cycles (FTC) impact concrete durability and structural integrity, exploring novel approaches like integrating nanomaterials and fibers into concrete compositions. After subjecting the materials to FTC, the study evaluated mortars enriched with nano-SiO2 (NS) and micro- and macro-basalt (BA) fibers. NS was incorporated by substituting 1 % and 2 % of the cement content. Meanwhile, 24 mm in length macro-BA fibers were added individually or in hybrid compositions with 6 mm micro-BA fibers at 0.5 % and 1 % volumetric ratios. The results revealed significant improvements in both the strength and durability of mortar specimens post-FTC, attributed to the enhancing properties of NS. Its capacity to fill voids and substantial pozzolanic activity notably improved the material's performance. However, adding BA fibers adversely affected mortar workability, causing a decrease in flow diameters (FD) as the fiber ratio increased. Nevertheless, BA fibers effectively maintained specimen integrity post-FTC despite leading to decreased residual compressive (RCS) and flexural strengths (RFS). This reduction was linked to the robust bonding between BA fibers and the matrix, impeding crack propagation post-FTC. Interestingly, combining BA fibers in hybrid configurations improved workability and significantly enhanced residual strength characteristics, surpassing singular applications. For instance, after 180 FTC, the K0 control specimen exhibited a 34.17 % and 34.56 % reduction in RCS and RFS, respectively. In contrast, the K10 specimen with 2 % NS and a hybrid combination of BA fibers at a volumetric ratio of 1 % displayed notably lower reduction rates of 23.69 % and 16.99 %, respectively. © 2024 Elsevier Ltd