Browsing by Author "Şahmaran, Mustafa"
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Conference Object Autogenous Self-Healing Assessment in Engineered Cementitious Composites Through Gas Permeability Measurements(2021) Tuğluca, Merve Sönmez; Yıldırım, Gürkan; Öztürk, Oğuzhan; Şahmaran, MustafaBook Part Citation - Scopus: 1Determination of Autogenous Self-Healing Capability of Cementitious Composites Through Non-Destructive Testing(Springer Science and Business Media B.V., 2021) Yıldırım, Gürkan; Öztürk, Oğuzhan; Ulugöl, H.; Hatem, M.; Şahmaran, MustafaUnlike conventional concrete and fiber reinforced concrete, Engineered Cementitious Composites (ECC) display closely spaced multiple microcracks through strain/deflection-hardening response when subjected to tension-based loadings. These multiple microcracks allow ECC to be characterized with inherent autogenous self-healing capability. With the emergence of cement-based composites exhibiting multiple tight cracking, possibility for favoring the intrinsic self-healing behavior increased. Self-healing phenomenon in cementitious composites is being studied extensively nowadays. Although, great number of tests utilized to evaluate the self-healing mechanism in cementitious composites, implementation can be time consuming in some occasions and results from different tests may not always well-suit. Thus, different from other studies in literature, direct electrical impedance (EI) measurements were used in the present study to evaluate the self-healing performance of ECC mixtures along with rapid chloride permeability test (RCPT) and resonant frequency (RF) measurements. Experimental results revealed that EI testing is rather easy to perform and takes very limited time but it seems that the method itself is markedly influenced by anything modifying ionic state of specimens. Therefore, it looks like a hard task to very accurately assess the self-healing performance of ECC specimens considering the fact that both ongoing hydration and calcium carbonate precipitation which are regarded to be the main mechanisms contributing to the autogenous self-healing significantly changes the specimens’ pore solution chemistry. Well-fitting exponential relationship exists between EI and RCPT measurements at different ages regardless of the mixture and specimen type. However, results from RF tests do not correlate either with EI or RCPT results which is attributed to the different parameters having paramount influence on the individual tests. Although results from different tests do not always correlate well among themselves, three different tests used for the present study are capable of monitoring the self-healing behavior with differing efficiencies. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG.Conference Object Determination of Autogenous Self-Healing Capability of Cementitious Composites Through Non-Destructive Testing(2020) Yıldırım, Gürkan; Öztürk, Oğuzhan; Ulugöl, Hüseyin; Balav, Muhammed; Şahmaran, MustafaConference Object Development of Deflection-Hardening Hybrid Fiber-Reinforced Concretes With Large Share of Coarse Aggregates(2021) İlcan, Hüseyin; Yıldırım, Gürkan; Öztürk, Oğuzhan; Şahmaran, MustafaConference Object Gerçek Zamanlı Yapısal Malzeme Sağlık İzleme veya Takibi Uygulamaları İçin Çok Fonksiyonlu Çimento Bağlayıcılı Kompozitler(2019) Öztürk, Oğuzhan; Yıldırım, Gürkan; Keskin, Ülkü Sultan; Şahmaran, MustafaConference Object Nano-Scale Tailoring of Engineered Cementitious Composites for Simultaneous Achievement of Enhanced Healing and Sensing Functionalities(2018) Öztürk, Oğuzhan; Yıldırım, Gürkan; Kul, Anıl; Şahmaran, Mustafa; Keskin, Ülkü SultanAutogenous self-healing can be a handy tool for concrete material to self-repair its own damage. On the other hand, to keep infrastructures in a serviceable state, it is also important to identify and assess any structural damage (cracks) as early as possible, before losing complete and/or sectional integrity. In this regard, efforts can be made to make concrete material work like a sensory material by making its nature electrically conductive (i.e. selfsensing) and responsive to any changes in applied strains. Engineered Cementitious Composites (ECCs) are new-generation ductile concretes capable of favouring autogenous self-healing through the formation of micron-size cracks upon straining. ECCs are also characterized by piezoresistive (self-sensing) response meaning that they exhibit strong dependence of electrical resistivity to the applied loading. Within this context, an attempt has been made here to further nourish both autogenous self-healing and self-sensing capabilities of ECCs by tailoring the matrix properties with different nanomaterials. With the purpose of improving self-healing and self-sensing attributes of ECC material, nano-silica and carbon nanotubes were simultaneously incorporated in mixture compositions, respectively. Tests were performed on sound and pre-loaded (almost-failed) prismatic ECC specimens under four-point bending loading. Both self-sensing and self-healing properties were evaluated before/after the introduction of microcracking and upon exposure to further curing. Results revealed that proposed nano-modification of ECC mixtures significantly improved the autogenous self-healing and self-sensing capabilities simultaneously. Outcomes of this study are believed to make a marked impact on true infrastructural sustainability by not only reducing the frequency of repair/maintenance applications but also making infrastructures much smarter to easily track their own damage.Article Citation - WoS: 84Citation - Scopus: 101Nano-Tailored Multi-Functional Cementitious Composites(ELSEVIER SCI LTD, 2020) Öztürk, Oğuzhan; Yıldırım, Gürkan; Keskin, Ülkü Sultan; Siad, Hocine; Şahmaran, MustafaThis paper explores the effects of single and binary use of nano-additions on the self-sensing and self-healing efficiencies of cementitious composites in achieving a material that combines high mechanical and multifunctional performances. The researchers studied three nano-tailored cementitious compositions incorporating nano-silica (NS), multi-walled carbon nanotubes (CNT) and binary NS/CNT, as well as control composites prepared without nano-additions. The study included compressive strength testing on sound specimens and an evaluation of combined self-sensing/self-healing capabilities with electrical resistivity (ER) measurements conducted before and after preloading and during the self-healing recovery stage. Recovery rates were also evaluated via crack width measurements recorded by video microscope and compared to ER testing results. To account for different self-healing products, microstructural characterization was performed on healed cracks using scanning electron microscopy coupled with EDX (SEM/EDX) and thermo-gravimetric (TG/DTG) analyses. Results show that while the single use of CNT can promote self-sensing and self-healing properties, using binary NS/CNT can significantly enhance these performances. The density and amounts of C-S-H and CaCO3 in healed cracks increased with the addition of nano-materials, especially for the binary NS/CNT.Conference Object Self-Healing Performance of Engineered Cementitious Composites Through the Use of Nano-Silica(2019) Öztürk, Oğuzhan; Yıldırım, Gürkan; Keskin, Ülkü Sultan; Şahmaran, MustafaArticle Citation - WoS: 107Citation - Scopus: 122Self-Sensing Capability of Engineered Cementitious Composites: Effects of Aging and Loading Conditions(ELSEVIER SCI LTD, 2020) Yıldırım, Gürkan; Öztürk, Oğuzhan; Al-Dahawi, Ali; Ulu, Adem Afşin; Şahmaran, MustafaSelf-sensing capability of 7-, 28-, 90- and 180-day-old Engineered Cementitious Composites (ECC) incorporated either with carbon fibers (CF/ECC-CF) at micro-scale or multi-walled carbon nanotubes (CNT/ECC-CNT) and carbon black (CB/ECC-CB) at nano-scale were investigated herein. Mechanical properties (compressive strength, splitting tensile strength/deformation, flexural strength/deformation) of different-age mixtures were evaluated. Control mixture (ECC-Control) without any carbon-based material was also produced and tested for comparison. Depending on the loading condition, equipment utilizing either direct current (DC) or alternating current (AC) was used for self-sensing assessments. Results showed that carbon-based materials generally improve the mechanical properties of ECC-Control specimens depending on the type of carbon-based materials, specimens' age and loading conditions. All specimens sensed different types of damage except 180-day-old ECC-Control specimens loaded under uniaxial compression and splitting tension due to abrupt increments in impedance results exceeding the limits of testing device which revealed the importance of presence of electrically-conductive materials for achieving enhanced self-sensing capability independent of aging, testing configuration/equipment, loading conditions and microcrack characteristics. CF is the best to improve self-sensing capability of ECC-Control specimens for all ages and loading conditions. Self-sensing performances of ECC-CNT and ECC-CB are comparable and utilization of nano-size carbon-based materials is suggested in cases where reversibility in self-sensing is needed. (C) 2019 Elsevier Ltd. All rights reserved.
