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    The influence of aggregate type on the strength and abrasion resistance of high strength concrete
    (Elsevier Sci Ltd, 2008) Kilic, A.; Atis, C. D.; Teymen, A.; Karahan, O.; Ozcan, F.; Bilim, C.; Ozdemir, M.
    This paper examines the influence of aggregate type on the strength characteristics and abrasion resistance of high strength silica fume concrete. Five different aggregate types (gabbro, basalt, quartsite, limestone and sandstone) were used to produce high strength concrete containing silica fume. Silica fume replacement ratio with cement was 15% on a mass basis. Water-binder ratio was 0.35. The amount of hyperplasticizer was 4% of the binder content by mass. Gabbro concrete showed the highest compressive and flexural tensile strength and abrasion resistance, while sandstone showed the lowest compressive and flexural tensile strength and abrasion resistance. High abrasion resistant aggregate produced a concrete with high abrasion resistance. Three-month compressive strengths of concretes made with basalt, limestone and sandstone were found to be equivalent to the uniaxial compressive strengths of their aggregate rocks. However, the concretes made with quartsite and gabbro aggregate showed lower compressive strength than the uniaxial compressive strength of their aggregate rocks. (c) 2007 Elsevier Ltd. All rights reserved.
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    Investigation of Properties of Engineered Cementitious Composites Incorporating High Volumes of Fly Ash and Metakaolin
    (Amer Concrete Inst, 2012) Ozbay, E.; Karahan, O.; Lachemi, M.; Hossain, K. M. A.; Atis, C. Duran
    This study was carried out to develop engineered cementitious composites (ECCs) incorporating binary blends of high volumes of fly ash (FA) and metakaolin (MK) for the purpose of achieving low drying shrinkage and high composite strength with adequate ductility and improved durability. ECC, an ultra-ductile cement-based composite reinforced with short random fibers, exhibits strain-hardening and multiple-cracking behavior in uniaxial tension and bending. Standard (M45) and high-volume FA ECC mixtures are typically produced by replacing portland cement (PC) with 55% and 70% of FA, respectively (FA-to-cement ratio of 1.2 and 2.2 by weight). In this study, the (FA + MK)/PC ratio was maintained at 1.2 and 2.2 and the FA/MK ratio was maintained at 4.5. Two replacement levels of MK with FA were adopted. The investigation used 10% and 12.5% MK by weight of total binder content, respectively. For the purposes of comparison, standard and high-volume FA ECCs were also studied. To determine the effect of binary blends of FA and MK on the properties of ECC, this study focused on the evaluation of free drying shrinkage, flexural and compressive strengths, porosity and water absorption (WA), sorptivity, and chloride-ion permeability. The experimental results showed that the drying shrinkage, porosity, absorption, sorptivity, and chloride-ion permeability properties were significantly reduced with the use of binary blends of FA and MK, while ECC's ultra-high ductility and strain-hardening properties were preserved at an adequate level.
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    Investigation of properties of engineered cementitious composites incorporating high volumes of fly ash and metakaolin
    (2012) Özbay, E.; Karahan, O.; Lachemi, M.; Hossain, K.M.A.; Duran Atiş, C.
    This study was carried out to develop engineered cementitious composites (ECCs) incorporating binary blends of high volumes of fly ash (FA) and metakaolin (MK) for the purpose of achieving low drying shrinkage and high composite strength with adequate ductility and improved durability. ECC, an ultra-ductile cement-based composite reinforced with short random fibers, exhibits strain-hardening and multiple-cracking behavior in uniaxial tension and bending. Standard (M45) and high-volume FA ECC mixtures are typically produced by replacing portland cement (PC) with 55% and 70% of FA, respectively (FA-to-cement ratio of 1.2 and 2.2 by weight). In this study, the (FA + MK)/PC ratio was maintained at 1.2 and 2.2 and the FA/MK ratio was maintained at 4.5. Two replacement levels of MK with FA were adopted. The investigation used 10% and 12.5% MK by weight of total binder content, respectively. For the purposes of comparison, standard and high-volume FA ECCs were also studied. To determine the effect of binary blends of FA and MK on the properties of ECC, this study focused on the evaluation of free drying shrinkage, flexural and compressive strengths, porosity and water absorption (WA), sorptivity, and chloride-ion permeability. The experimental results showed that the drying shrinkage, porosity, absorption, sorptivity, and chloride-ion permeability properties were significantly reduced with the use of binary blends of FA and MK, while ECC's ultra-high ductility and strain-hardening properties were preserved at an adequate level. Copyright © 2012, American Concrete Institute. All rights reserved.