Browsing by Author "Yildirim, G."

Now showing 1 - 2 of 2

Citation - WoS: 47
Citation - Scopus: 59
Physical and Chemical Actions of Nano-Mineral Additives on Properties of High-Volume Fly Ash Engineered Cementitious Composites
(Amer Concrete inst, 2016) Al-Najjar, Y.; Yesilmen, S.; Al-Dahawi, Majeed; Sahmaran, M.; Yildirim, G.; Lachemi, M.; Amleh, L.; 17729
Unlike conventional concrete, the material design process for engineered cementitious composites (ECC) involves micromechanics-based design theory, paving the way for the use of high volumes of fly ash (HVFA) as a major component. Using high volumes of fly ash (up to 85% weight fraction of cement) in ECC mixtures enables improved tensile ductility (approximately a 3% increase in long-term tensile strain) with reduced crack widths, although it also leads to significantly reduced early-age compressive and tensile strength and chloride ion resistance. However, nanomineral additives are known to improve mechanical strength and durability of HVFA systems. The study emphasizes the effects of different fly ash (FA)/cement ratios on various properties (hydration and microstructural characteristics, transport and mechanical properties) of ECC mixtures designed with different mineral additives. Experimental results confirm that although different optimum levels can be selected to favor various ECC properties, optimum weight fraction of FA is dependent on the mechanism of nanomodification (that is, type of modifier). The optimum level of fly ash weight fraction that yields the highest rate of improvement through nanomodification of ECC varies for different mechanical and transport properties.
Citation - Scopus: 7
Toward Sustainability: A Review of Analytical Models for Circular Supply Chains
(Emerald Group Publishing Ltd., 2022) Ülkü, M.A.; Yıldırım, Gonca; Skinner, D.M.; Yildirim, G.; 45908; Endüstri Mühendisliği
The earth's carrying capacity cannot withstand the pace of consumption resulting from current economic models, mainly the linear economy (LE) built on a throwaway culture. In the last few decades, the concept of a circular economy (CE), aiming to design waste out of the economy and mimic ecosystems, emerged as a strong alternative to LE. Being at the heart of the economic landscape, supply chains (SCs) need to respond to the necessary shift to CE. In so doing, the planning and execution of circular supply chains (CSCs) require a broader comprehension of CE and more sophisticated and large-scale analytical decision models. This chapter surveys extant literature on available best practices and quantitative models for sustainable supply chains (SSCs) and offers a new definition of CSC. Mapping on the knowledge extracted from this classification, potential gaps and strengths in the literature are identified. Key research papers on the "closed-loop" and "open-loop" ends of CSCs are highlighted. Challenges in developing CSC performance indicators and prescriptive models are emphasized. © 2022 by Emerald Publishing Limited. All rights reserved.