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Öğe Coupled effects of limestone powder and high-volume fly ash on mechanical properties of ECC(Elsevier Sci Ltd, 2018) Turk, Kazim; Nehdi, Moncef L.Owing to its exceptional strain capacity, which can reach hundreds of times that of normal concrete, and its reduced crack width, engineered cementitious composites (ECC) are a very promising solution for mitigating many of the problems that generate colossal backlogs of deteriorated concrete structures worldwide. However, research is needed to develop more sustainable ECC with flexible formulation that uses local materials. This paper investigates the coupled effects of using limestone powder in ECC as partial or total replacement for silica sand aggregate, coupled with using high-volume fly ash as a binder. The compressive and flexural strengths and fracture toughness for the formulated ECCs were examined at 3, 28 and 90 days. The results of this study demonstrate that sustainable ECC for resilient structural applications can be produced. It is aimed that more flexible formulations of ECC using local materials with lower environmental footprint could emerge and contribute to more durable and sustainable civil infrastructure. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Durability of Engineered Cementitious Composites Incorporating High-Volume Fly Ash and Limestone Powder(Mdpi, 2022) Turk, Kazim; Kina, Ceren; Nehdi, Moncef L.This study investigates the effects of using limestone powder (LSP) and high-volume fly ash (FA) as partial replacement for silica sand (SS) and portland cement (PC), respectively, on the durability properties of sustainable engineered cementitious composites (ECC). The mixture design of ECC included FA/PC ratio of 1.2, 2.2 and 3.2, while LSP was used at 0%, 50% and 100% of SS by mass for each FA/PC ratio. Freeze-thaw and rapid chloride ions penetrability (RCPT) tests were performed to assess the durability properties of ECC, while the compressive and flexural strength tests were carried out to appraise the mechanical properties. Moreover, mercury intrusion porosimetry (MIP) tests were performed to characterize the pore structure of ECC and to associate porosity with the relative dynamic modulus of elasticity, RCPT and mechanical strengths. It was found that using FA/PC ratio of more than 1.2 worsened both the mechanical and durability properties of ECC. Replacement of LSP for SS enhanced both mechanical strengths and durability characteristics of ECC, owing to refined pore size distribution caused by the microfiller effect. It can be further inferred from MIP test results that the total porosity had a vital effect on the resistance to freezing-thawing cycles and chloride ions penetration in sustainable ECC.Öğe Flexural toughness of sustainable ECC with high-volume substitution of cement and silica sand(Elsevier Sci Ltd, 2021) Turk, Kazim; Nehdi, Moncef L.This study explores the effects of high-content fly ash and limestone filler partial replacement for portland cement and silica sand, respectively on the flexural toughness parameters of engineered cementitious composites (ECC). Various groups of mixtures having variable fly ash/portland cement ratio and different levels of limestone filler were prepared. ASTM C1609, JSCE-SF4 and the Post-Crack Strength method were employed to appraise the flexural toughness parameters of the ECC mixtures at 3, 28 and 90-d. The results show that according to ASTM C1609, JSCE-SF4 and the Post-Crack Strength method, limestone filler did not significantly affect the flexural toughness, while the flexural toughness of ECC beams decreased when the fly ash content increased. Considering deflection capacity, specimens made with a FA/OPC ratio of 1.2 without limestone filler achieved higher ductility at all curing ages. Owing to its superior crack resistance and toughness compared to normal concrete, ECC with high fly ash content and limestone filler could be a sustainable alternative construction material in diverse civil engineering applications. ECC with enhanced ductility compared to normal concrete could offer increased crack resistance, durability and better resilience. (C) 2020 Elsevier Ltd. All rights reserved.Öğe Hybrid deep learning model for concrete incorporating microencapsulated phase change materials(Elsevier Sci Ltd, 2022) Tanyildizi, Harun; Marani, Afshin; Turk, Kazim; Nehdi, Moncef L.The inclusion of microencapsulated phase change materials (MPCMs) in concrete promotes thermal energy storage, thus enhancing sustainable design. Notwithstanding this advantage, the compressive strength of concrete dramatically decreases upon MPCM addition. While several experimental studies have explored the origin of this compressive strength reduction, a reliable and practical framework for the prediction of the compressive strength of MPCM-integrated concrete is yet to be developed. The current research proposes a deep learning approach to estimate the compressive strength of MPCM-integrated cementitious composites based on its mixture proportions and the thermophysical properties of PCM. Extreme learning machines (ELMs), autoencoders, hybrid ELM-autoencoder, and extreme gradient boosting (XGBoost) models were purposefully developed using the largest pertinent experimental dataset available to date encompassing 244 mixture design examples retrieved from the open literature. The results demonstrate the capability of the hybrid deep learning and XGBoost models in accurately modeling the compressive strength of PCM integrated concrete with favorably low prediction error. Furthermore, a sensitivity analysis identified the most influential parameters on the compressive strength development to assist the mixture design of concrete incorporating MPCM.
