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Öğe Dual effectiveness of freezing-thawing and sulfate attack on high-volume slag-incorporated ECC(Elsevier Sci Ltd, 2013) Ozbay, Erdogan; Karahan, Okan; Lachemi, Mohamed; Hossain, Khandaker M. A.; Atis, Cengiz DuranThis study investigated the dual effect of freeze-thaw cycles with sodium sulfate solution on the performance of non-air-entrained Engineering Cementitious Composites (ECCs) with high volumes of slag. ECC specimens containing three different levels of slag content as a replacement for cement (55%, 69% and 81% by weight of total cementitious material) were exposed to aggressive sodium sulfate solution under freezing-thawing cycles. The load-deflection response associated with ultimate mid-span deflection and flexural strength/stiffness was determined, along with crack development behavior. For comparison purposes, the freezing-thawing resistance (in water) of control ECC specimens was also evaluated. Modified point count method air-void parameters, compressive strength, porosity, water absorption and sorptivity tests were also conducted on the virgin ECC specimens (those not exposed to freezing-thawing cycles in water or aggressive sodium sulfate solution). The test results for the virgin specimens revealed that increased slag content (S/PC) improved the ductility, hardened air content, water absorption, porosity and sorptivity of ECC, while marginally decreasing the compressive and flexural strengths. Freeze-thaw cycles in water or sodium sulfate solution showed that the ductility of ECC specimens decreased remarkably, irrespective of slag content and applied freezing-thawing process. Reduction in mass loss was at minimal levels and no significant behavior change was monitored between the specimens undergoing freeze-thaw cycling in water and the aggressive sodium sulfate solution. Moreover, the decrease in flexural stiffness was more evident than the reduction of the flexural strength for all ECC mixtures. Crown Copyright (c) 2012 Published by Elsevier Ltd. All rights reserved.Öğe Effect of kaolin waste content on the properties of normal-weight concretes(Elsevier Sci Ltd, 2015) Lotfy, Abdurrahmaan; Karahan, Okan; Ozbay, Erdogan; Hossain, Khandaker M. A.; Lachemi, MohamedThis paper presents the mechanical, transport and drying shrinkage properties of normal-weight kaoline waste (MW) incorporated concretes. Six different concrete mixtures that have a constant water-binder ratio (w/b) of 0.40 and a binder (Portland cement + kaoline waste) content of 400 kg/m(3) were designed with various MW replacement contents (0%, 5%, 10%, 15%, 20% and 25% of Portland cement by weight). Workability, unit weight, compressive and tensile strengths, water absorption, porosity, sorptivity, rapid chloride permeability and drying shrinkage tests were performed on fresh and hardened concretes. Test results were analysed by considering the KW content and it was concluded that use of MW worsened the workability and decreased unit weight irrespective of KW content. MW incorporation affected the compressive strength positively, especially at the 10% and 15% replacement levels beyond 28 days. Replacement of MW up to 15% exhibited virtually identical porosity and water absorption values with the control concrete. Sorptivity values of KW concrete mixtures (at 5% and 10% kaolin waste replacement) were equal or somewhat lower than that of the control mixture. Chloride ion penetration resistance of concretes improved drastically with the increase of MW content. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Effect of metakaolin content on the properties self-consolidating lightweight concrete(Elsevier Sci Ltd, 2012) Karahan, Okan; Hossain, Khandaker M. A.; Ozbay, Erdogan; Lachemi, Mohamed; Sancak, EmreThis paper presents the fresh, mechanical and transport properties of expanded shale aggregate self-consolidating lightweight concrete (SCLC) containing metakaolin assessed by means of slump flow, flow time, V-funnel, L-box, compressive, flexural/splitting/bond strength, water absorption, porosity, sorptivity and rapid chloride permeability tests. Metakaolin content based SCLC mixtures were developed by incorporating 0%, 20%, 40% and 60% of as a replacement by weight of fly ash while keeping a constant cement and mineral admixture content of 450 kg/m(3) and 150 kg/m(3), respectively. These included four mixtures containing 0%, 5%, 10% and 15% metakaolin content as a partial binder replacement. It was observed that expanded shale aggregates SCLC can be produced with the density lower than 2000 kg/m3 which was increased by the addition of metakaolin. Increases in metakaolin content worsened the filling and passing ability of SCLC and by the addition of metakaolin no positive effect on the strength properties on SCLC was monitored. Replacement of 20%, 40% and 60% of metakaolin with fly ash resulted 3%, 8% and 10% decrease in porosity and water absorption with respect to control mixture, respectively. The initial and secondary sorptivity values of SCLC mixtures with metakaolin replacement were equal or lower than the control mixture without metakaolin. Moreover, increases in metakaolin content showed significant improvement in chloride ion penetration resistance of SCLC. (C) 2012 Elsevier Ltd. All rights reserved.Öğe Fresh, Mechanical, Transport, and Durability Properties of Self-Consolidating Rubberized Concrete(Amer Concrete Inst, 2012) Karahan, Okan; Ozbay, Erdogan; Hossain, Khandaker M. A.; Lachemi, Mohamed; Atis, Cengiz D.This paper presents the fresh, mechanical, transport, and durability performances of self-consolidating rubberized concretes (SCRCs). Fresh concrete properties were determined with slump flow, V-funnel, J-ring, and L-box tests. Mechanical, transport, and durability properties were determined by measuring compressive, flexural, and splitting tensile strengths; bond strength characteristics; water porosity; water absorption; water sorptivity; rapid chloride-ion permeability; and freezing-and-thawing and corrosion resistance. SCRC mixtures with a water-binder ratio (w/b) of 0.32; total binder content of 500 kg/m(3) (842 lb/yd(3)); and crumb rubber content of 0, 10, 20, and 30% by fine aggregate volume were produced and tested. Fresh properties testing revealed that the use of crumb rubber as a fine aggregate diminished the filling and passing ability of SCRC. A gradual reduction in mechanical properties was also observed with an increase in crumb rubber content; however, the rate of compressive strength reduction was more evident than that of tensile strength. Despite the fact that water porosity, water absorption, and chloride-ion permeability increased slightly with the use of crumb rubber, a remarkable decrease was observed in the initial and secondary water sorptivity of SCRC. No significant decrease was observed in the freezing-and-thawing and corrosion resistance of SCRC with 10% crumb rubber. Beyond that level, however, durability performance was significantly affected.Öğe Ground Granulated Pumice-Based Cement Mortars Exposed to Abrasion and Fire(Springer Heidelberg, 2017) Karahan, Okan; Hossain, Khandaker M. A.; Atis, Cengiz D.; Lachemi, Mohamed; Ozbay, ErdoganThis study investigates the effect of ground granulated pumice (GGP) on workability, compressive/flexural strength and abrasion/fire resistance of mortars. Mortar mixture was prepared by replacing cement with GGP at five different replacement ratios (0, 5, 10, 15 and 20%). The sand-to-binder and water-to-binder ratios of the produced mortars were 3.0 and 0.50, respectively. Compressive/flexural strength and horizontal Bohme abrasion tests were conducted on mortar specimens at 28 days. Mortar specimens were also exposed to elevated temperatures of 300, 600 and 900 for a duration of 1 h to measure residual compressive strength. Test results showed that the use of GGP reduced the flow/workability of fresh mortars. It was also observed that the use of 10% GGP content slightly improved strength, abrasion and fire resistance of mortars compared to control normal Portland cement mortar.Öğe Influence of activator on the strength and drying shrinkage of alkali-activated slag mortar(Elsevier Sci Ltd, 2009) Atis, Cengiz Duran; Bilim, Cahit; Celik, Oezlem; Karahan, OkanThe development of new binders, as an alternative to traditional cement, by the alkaline activation of industrial by-products (i.e. ground granulated slag and fly ash) is an ongoing research topic in the scientific community [Puertas F, Amat T, Jimenez AF, Vazquez T. Mechanical and durable behaviour of alkaline cement mortars reinforced with polypropylene fibres. Cem Concr Res 2003; 33(12): 2031-6]. The aim of this study was to investigate the feasibility of using and alkaline activated ground Turkish slag to produce a mortar without Portland cement (PC). Following the characterization of the slag, mortar specimens made with alkali-activated slag were prepared. Three different activators were used: liquid sodium silicate (LSS), sodium hydroxide (SH) and sodium carbonate (SC) at different sodium concentrations. Compressive and flexural tensile strength of alkali-activated slag mortar was measured at 7-days, 28-days and 3-months. Drying shrinkage of the mortar was measured up to 6-months. Setting times of the alkali-activated slag paste and PC paste were also measured. Setting times of LSS and SH activated slag pastes were found to be much slower than the setting time of PC paste. However, slag paste activated with SC showed similar setting properties to PC paste. LSS, SH and SC activated slag mortar developed 81, 29, and 36 MPa maximum compressive strengths, and 6.8, 3.8, and 5.3 MPa maximum flexural tensile strengths at 28-days. PC mortar developed 33 MPa compressive strength and 5.2 MPa flexural tensile strength. LSS and SH activated slag mortars were found to be more brittle than SC activated slag and PC mortars. Slag mortar made with LSS had a high drying shrinkage, up to six times that of PC mortar. Similarly, slag mortar made with SH had a shrinkage up to three times that of PC mortar. However, SC activated slag mortar had a lower or comparable shrinkage to PC mortar. Therefore, the use of SC as an activator for slag mortar is recommended, since it results in adequate strength, similar setting times to PC mortar and comparable or lower shrinkage. (C) 2007 Elsevier Ltd. All rights reserved.
