Yazar "Guneyisi, Erhan" seçeneğine göre listele

Listeleniyor 1 - 8 / 8
  • Küçük Resim Yok
    Öğe
    Combined Use of Natural and Artificial Slag Aggregates in Producing Self-Consolidating Concrete
    (AMER CONCRETE INST, 2016) Oz, Hatice Oznur; Gesoglu, Mehmet; Guneyisi, Erhan; Mahmood, Swara Fuad
    This study addresses properties of self-consolidating concrete (SCC), in which natural coarse aggregates had been substituted by artificial slag aggregates (ASAs). For this, 90% groundgranulated blast-furnace slag and 10% portland cement by weight were pelletized in a tilted pan through cold-bonded agglomeration process. Then, the hardened coarse aggregates (ASA) were tested for specific gravity, water absorption, and crushing strength. Thereafter, they were partially used in producing SCCs in which ASA replaced the natural coarse aggregates at 0, 20, 40, 60, 80, and 100% by volume. Therefore, six SCCs with 0.32 water-binder ratio (w/b) were designed and cast using both natural and/or ASA. Hardened concrete properties were tested for compressive and splitting tensile strengths, modulus of elasticity, drying shrinkage, freezing-and-thawing resistance, chloride ion permeability, gas permeability, and sorptivity. Test results indicated that SCCs with ASA displayed better performance than the control mixture in terms of durability-related properties. Incorporating ASA in SCCs increased the compressive strength and elastic modulus (up to 60%) but decreased the splitting tensile strength. However, ASA provided gradual reduction in sorptivity coefficient, chloride ion, and gas permeability especially at 60% replacement level and 56 days.
  • Küçük Resim Yok
    Öğe
    Durability and Shrinkage Characteristics of Self-Compacting Concretes Containing Recycled Coarse and/or Fine Aggregates
    (HINDAWI PUBLISHING CORPORATION, 2015) Gesoglu, Mehmet; Guneyisi, Erhan; Oz, Hatice Oznur; Yasemin, Mehmet Taner; Taha, Ihsan
    This paper addresses durability and shrinkage performance of the self-compacting concretes (SCCs) in which natural coarse aggregate (NCA) and/or natural fine aggregate (NFA) were replaced by recycled coarse aggregate (RCA) and/or recycled fine aggregate (RFA), respectively. A total of 16 SCCs were produced and classified into four series, each of which included four mixes designed with two water to binder (w/b) ratios of 0.3 and 0.43 and two silica fume replacement levels of 0 and 10%. Durability properties of SCCs were tested for rapid chloride penetration, water sorptivity, gas permeability, and water permeability at 56 days. Also, drying shrinkage accompanied by the water loss and restrained shrinkage of SCCs were monitored over 56 days of drying period. Test results revealed that incorporating recycled coarse and/or fine aggregates aggravated the durability properties of SCCs tested in this study. The drying shrinkage and restrained shrinkage cracking of recycled aggregate (RA) concretes had significantly poorer performance than natural aggregate (NA) concretes. The time of cracking greatly prolonged as the RAs were used along with the increase in water/binder ratio.
  • Küçük Resim Yok
    Öğe
    Effect of nano silica on the workability of self-compacting concretes having untreated and, surface treated lightweight aggregates
    (ELSEVIER SCI LTD, 2016) Guneyisi, Erhan; Gesoglu, Mehmet; Azez, Oday Ali; Oz, Hatice Oznur
    This paper presents the fresh properties of self-compacting lightweight aggregate concrete (SCLC) made with cold bonded fly ash (FA) lightweight aggregate (LWA) at a wide range of water-to-binder (w/b) ratios. For this, three concrete series including eighteen SCLCs were designed with w/b ratios of 0.25, 0.37 and 0.50, respectively. Each series have 6 different mixes in which two type of coarse LWAs (surface treated or not) and three nano silica (nS) replacement levels (0, 2.5% and 5.0%) are considered. The properties of SCLCs were observed in terms of slump flow diameter, T-500 slump flow time, V-funnel flow time, and L-box height ratio. The compressive strength test was also conducted to obtain the strength level at 28 days. It is found that the fresh SCLCs have good fluidity, passing ability, uniform aggregate distribution and resistance to segregation. Incorporating treated coarse LWA5 increased the workability characteristics of SCLCs. However, appreciable improvement in the consistency of SCLCs by nS addition was observed. The SCLCs made with treated LWAs and 5% nS were found to be the harder samples in this research. (c) 2016 Elsevier Ltd. All rights reserved.
  • Küçük Resim Yok
    Öğe
    Failure characteristics of self-compacting concretes made with recycled aggregates
    (ELSEVIER SCI LTD, 2015) Gesoglu, Mehmet; Guneyisi, Erhan; Oz, Hatice Oznur; Taha, Ihsan; Yasemin, Mehmet Taner
    This study addresses the properties of self-compacting concretes (SCCs) produced with recycled coarse aggregates (RCAs) and/or recycled fine aggregates (RFAs) compared to SCCs with natural aggregates (NAs). The SCC mixtures were designed with a constant slump flow of 680 +/- 30 mm and two water/binder (w/b) ratios of 0.3 and 0.43. Silica fume (SF) was also used at two replacement levels of 0% and 10%. Hardened properties of the SCCs were evaluated in terms of compressive strength, splitting tensile strength, static modulus of elasticity, and net flexural strength after 56 days of water curing. Failure mechanism of the concretes was also monitored via three-point bending test on the notched beams. The results indicated that failure occurred throughout the recycled aggregates (RAs) which in-turn decreased the mechanical properties of SCCs. However, SCCs with both fine and coarse RAs (RCAs + RFAs) had relatively worse performance than those with only RCAs or RFAs such that the reduction in strength was about 30% as compared to the corresponding reference mixes. Moreover, incorporating SF and decreasing w/b ratio improved the mechanical properties of SCCs. (C) 2015 Elsevier Ltd. All rights reserved.
  • Küçük Resim Yok
    Öğe
    Internal Curing of High-Strength Concretes Using Artificial Aggregates as Water Reservoirs
    (AMER CONCRETE INST, 2015) Gesoglu, Mehmet; Guneyisi, Erhan; Ismael, Ali Nooruldeen Ismael; Oz, Hatice Oznur
    This paper investigates the shrinkage cracking performance of high-strength concrete (HSC) containing artificial fly ash (AFA) and artificial blast furnace slag aggregates (ASAs) used as water reservoirs to provide internal curing. Artificial aggregates (AAs) were produced through cold bonding pelletization of 90% fly ash or slag with 10% portland cement. At a constant water-cement ratio (w/c) of 0.28, a total of nine HSCs incorporating varying amounts of AFA or ASA (0%, 5%, 10%, 15%, and 20%) by total aggregate volume were designed. The hardened concretes were tested for compressive strength, splitting tensile strength, and modulus of elasticity at 28 days for assessment of mechanical properties. Drying shrinkage accompanied by water loss, restrained shrinkage, and autogenous shrinkage were also monitored for a drying period of 57 days. Test results indicated that the highest mechanical properties were achieved for HSC with 20% ASA. Using ASA extended the cracking time of the HSCs and resulted in finer cracks associated with the lower free shrinkage. Moreover, there was a marked decrease in the autogenous shrinkage for all HSCs including artificial aggregates.
  • Küçük Resim Yok
    Öğe
    Self-Consolidating Concretes Made with Cold-Bonded Fly Ash Lightweight Aggregates
    (Amer Concrete Inst, 2017) Oz, Hatice Oznur; Gesoglu, Mehmet; Guneyisi, Erhan; Sor, Nadhim Hamah
    An experimental program was conducted to investigate the mechanical, fracture, and physical properties of self-consolidating lightweight concretes (SCLCs) made with cold-bonded fly ash (FA) aggregates. A total of 17 SCLCs were designed with a water-binder ratio (w/b) of 0.32, in which the natural aggregates were partially replaced with cold-bonded lightweight fine aggregate (LWFA) and lightweight coarse aggregate (LWCA) at different volume fractions of 10, 20, 30, 40, and 50%. Hardened properties of the SCLCs were tested for bond strength, fracture energy, characteristic length, drying shrinkage, weight loss, and restrained shrinkage cracking. It was observed that the SCLCs had relatively lower compressive and splitting tensile strengths with increasing LWFA and/or LWCA in the mixtures. Bond strength of the SCLCs decreased gradually with the replacement level of LWA because the bond strength directly depended on the quality of the cement paste and aggregate. Although SCLCs had significantly poorer restrained shrinkage cracking performance than the control concrete, the time to cracking greatly lengthened as the replacement level of LWA increased.
  • Küçük Resim Yok
    Öğe
    Shear thickening intensity of self-compacting concretes containing rounded lightweight aggregates
    (ELSEVIER SCI LTD, 2015) Gesoglu, Mehmet; Guneyisi, Erhan; Ozturan, Turan; Oz, Hatice Oznur; Asaad, Diler Sabah
    This paper investigates the rheological behavior of self compacting concrete (SCC) made by replacing normal-weight aggregates (NWAs) with cold bonded lightweight fly ash aggregates (LWAs). Dry powder mixture of 90% fly ash and 10% Portland cement by weight was pelletized through moistening in a revolving tilted pan at ambient temperature to produce lightweight fly ash aggregates which were then cured for 28 days. Seventeen concrete mixtures were produced to have a fixed slump flow by using varying amounts of High-Range-Water-Reducing-Admixture (HRWRA). Increasing replacement level for fine and/or coarse LWA simultaneously decreased density and plastic viscosity which made the concretes less susceptible to shear thickening. Meanwhile, the increasing percentage of LWA used reduced the HRWRA needed for gaining constant workability. With full replacement by lightweight fly ash aggregates, 25% reduction was achieved in the fresh density of self-compacting concrete produced. (c) 2015 Elsevier Ltd. All rights reserved.
  • Küçük Resim Yok
    Öğe
    Utilization of cold bonded fly ash lightweight fine aggregates as a partial substitution of natural fine aggregate in self-compacting mortars
    (ELSEVIER SCI LTD, 2015) Guneyisi, Erhan; Gesoglu, Mehmet; Altan, Inan; Oz, Hatice Oznur
    In this study, lightweight fly ash fine aggregates (LWFAs) were used as a partial replacement of natural fine aggregate to investigate the fresh and hardened states of self-compacting mortars (SCMs). For this, a powder mixture of 90% fly ash (FA) and 10% Portland cement (PC) by weight were pelletized in a tilted pan through a cold-bonded agglomeration process. Thereafter, a total of five mixtures of SCMs were prepared in which natural fine aggregate was replaced by LWFA partially started from 0% to 100% by 25% increment. Subsequently, tests carried out on the fresh mortar involved mini-slump flow, mini-V-funnel flow time and viscosity while the hardened properties of SCMs were evaluated using the compressive strength, ultrasonic pulse velocity, gas permeability and sorptivity tests. The hardened characteristics of SCMs were determined at different ages up to 56 days. It was observed that the increased percentage of LWFA improved the workability and the flowability of SCMs. On the other hand, the strength and permeability properties of SCMs had a negative effect due to the substitution of LWFAs for natural fine aggregate, especially at higher replacement level. (C) 2014 Elsevier Ltd. All rights reserved.