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This study contributes to the understanding of the chloride-induced corrosion of steel rebars embedded in various concretes. Concrete specimens were exposed to systematic wetting-drying cycles in real seawater via a platform installed on a pier. Various mixtures were designed using three different cement types and two binder dosages (therefore two water/cement ratios) with and without fly ash. The strength development and electrical conductivity of the mixtures were assessed prior to the cycles. The dimensional stability, flexural strength, compressive strength, and chloride penetration depth of plain concretes were scrutinized during the cycles. The corrosion processes of 360 RC specimens with three different cover thicknesses were monitored. The test results revealed that increasing the dosage of cement, and therefore decreasing the water/cement ratio, was a more effective corrosion-mitigation approach than was the utilization of fly ash or enhancing physical protection.

Reactive powder concrete (RPC) is an ultra-high strength and high ductility cement-based composite. Associated with early-age shrinkage, high cement dosage may reduce the mechanical and durability performance of RPC. This study aims to clarify the influence of high volume mineral admixtures, aggregate restraint and fibre reinforcement on early-age autogenous and drying shrinkage of eco-friendly RPC at early-age (

In several studies, Isophorone diisocyanate (IPDI), a monomeric aliphatic diisocyanate, has been microencapsulated with various polymeric shells for self-healing purposes in polymer-based materials. In this study, for the first time, isophorone diisocyanate was microencapsulated with silica shell via interfacial polycondensation of a silica precursor (TEOS). The shell materials of the IPDI-loaded microcapsules reported in the literature are polymeric (organic). It is known from the literature that silica shell can chemically and physically bonded to cementitious matrices, allowing the microcapsules to remain stable for years without deterioration. Essential parameters such as the amounts of core material (IPDI), shell-forming material, and surfactant as well as the stirring speeds were investigated through yield, optical microscopy, SEM, TGA, and FTIR analyses. Promising results were obtained in the process of microencapsulation of isophorone diisocyanate with silica shell. The optimum core material/shell-forming material, oil phase/aqueous phase, and surfactant/oil ratios were found to be 1.0, 0.18, and 0.08, respectively.

Enhancing and characterization of self-healing ability of ultra high performance concrete (UHPC) is the main aim of this study. The self-healing mechanisms of macro/micro cracks were investigated through different techniques with some novel procedures. Two different mix designs have been considered to increase the amount of unreacted particles in the matrix. In spite of the positive effect of supplementary cementitious materials (SCM) on self-healing ability of UHPC, it was observed that the detected self-healing ratios depend on critical parameters such as damage type/level and the methods used to verify the phenomenon of self-healing. Depending on the composition of the UHPC mixtures, the age of specimens and the assessing method, up to 70-76% recoveries were obtained in the compressive strength and permeability of specimens pre-loaded up to -400% of their corresponding compressive strength. In addition, up to 88-100% crack sealing was observed in the pre-cracked UHPC specimens assessed via various methods. (C) 2021 Elsevier Ltd. All rights reserved.

Reoloji ve büzülme, başarılı bir yerleştirme işlemi gerçekleştirmek ve dayanıklı bir ultra yüksek performanslı beton (UYPB) üretmek için kontrol altında tutulması gereken anahtar özelliklerdir. Yakın gelecekte UYPB'nin yerinde döküm uygulamalarının artması beklenmektedir ve bu yüzden erken yaş özellikleri konusundaki araştırmalar önem kazanmıştır. Ancak hala istenen performansı garanti edebilen standartlaşmış bir karışım tasarımı yöntemi bulunmamaktadır. Yüksek miktardaki çimento içeriği ve düşük su/bağlayıcı oranı, özellikle erken yaşta çatlak riskini yükselten büzülme değerlerini arttırmaktadır. Karışım oranlarının, reolojik davranışı ve büzülme özelliklerini tayin eden temel değişkeni şüphesiz ki agrega hacmi, dolayısıyla da hamur hacmidir. Deneysel çalışma kapsamında kuvars agregası hacminin UYPB'nin reolojik, büzülme ve mekanik özelliklere etkisi araştırılmıştır. Sonuçlar, agrega hacminin arttırılmasının psödoplastik davranışın belirginleşmesine sebep olduğunu göstermiştir. Kendiliğinden yerleşen bir UYPB üretebilmek için agrega hacmi üst değeri %45 olarak bulunmuştur. Gerek bünyesel büzülme gerekse kuruma büzülmesi, agrega hacminin arttırılmasıyla sınırlandırılabilmektedir. Erken yaş bünyesel büzülme ve kuruma büzülmesi, kalıp alımından sonra 90 gün boyunca ölçülen uzun dönemli büzülmelerden kat be kat fazladır. Bu sebeple gerekli önlemler döküm aşamasından itibaren alınmalıdır.

In this study, the effects of recycled glass (RG) and recycled concrete (RC) fine aggregates on the drying-shrinkage, carbonation, high temperature and abrasion resistance of mortar mixtures were investigated comparatively. In addition, durability performance of the mortar mixtures was investigated through micro-structural analysis. For this purpose, 9 different mortar mixtures were prepared by replacing 25, 50, 75 and 100 wt.% of crushed-limestone fine aggregate with recycled glass and recycled concrete aggregates. Except for the abrasion resistance, the RG mixtures showed better durability performance than the control mixture. However, the RC mixtures containing more than 50% recycled aggregate showed lower performance than the control mixture.

Storing healing agents in capsules is one of the most promising self-healing methods in cementitious materials. Because of the considerable advantage of microencapsulation, it has become more interested as compared to the other encapsulation methods. The sodium silicate, which has many advantages as a healing agent in cementitious materials, can be encapsulated through the interfacial polymerization of shell-forming monomer on the aqueous sodium silicate droplets. This study, which is a part of comprehensive project, aimed to produce these microcapsules by optimization of the monomer. The microcapsules were characterized by the yield, SEM, EDS, FTIR, TGA, and XRD analyses. In addition, the fracture behavior of the optimized microcapsule was examined in a cement paste matrix. It was observed that most of the microcapsules seem to be spherical shaped and free-flowing powder. Fracture behavior of optimized microcapsules revealed a sufficient shell-matrix interfacial bond strength which is essential for releasing healing agent into cracks. (C) 2017 Elsevier Ltd. All rights reserved.

Bu calismada, iki farkli baslangic ortaminda bekletilmis lif iceren ve icermeyen ultra yuksek performansli beton (UYPB) karisimlarinin erken yas (ilk 24 saat) buzulme ozellikleri incelenmistir. Erken yasta oldukca yuksek mertebelerde buzulme gosteren karisimlarin kisitlanmis halde bekletilmesi halinde olusan catlaklarin celik donatinin korozyon gelisimine etkisi deneysel olarak belirlenmistir. Kisitlanmis buzulme catlaklarinin celik donati korozyonu uzerinde bazi olumsuz etkiler yarattigi tespit edilmistir. Ancak dusuk su/baglayici oranli UYBP orneklerinin yuzeyinde catlak olusmasina ragmen, donatiyi korumada oldukca iyi performans gosterdigi gorulmustur. UYPB'nin en onemli ozelligi, gecirimsiz yapisi nedeniyle sagladigi ustun durabilite (kalicilik) ozelligidir. UYPB'nin kalicilik ozelliklerinin korunmasi icin erken yas catlaklarinin onlenmesi amaciyla gerekli onlemler alinmalidir. Calisma kapsaminda yapilan analizler, ucucu kul ikamesinin ve mikro celik lif takviyesinin catlak olusumunu azaltarak donati korozyonuna karsi korumayi gelistirdigini gostermistir.

In this study, stirring speeds during the synthesizing process of the sodium silicate/polyurethane microcapsules were optimized. The yield values of microcapsules at different stirring rates were evaluated. Based on the yield values and shape of microcapsules, optimized microcapsules were obtained. The measurements of the shell thickness of microcapsules were performed on the fractured microcapsules by using scanning electron microscopy. The optimized microcapsules were further characterized by means of optical microscopy and nanoindentation. Load vs. displacement and modulus of elasticity vs. displacement characteristics of the microcapsules were obtained. The average modulus of elasticity was found to be 633 MPa. The self-healing efficiency of the optimized microcapsules was evaluated by means of compressive strength tests. The incorporation of microcapsules reduced the compressive strength of fiber-reinforced mortar by 12–22%. However, it was observed that the microcapsules enhanced the self-healing capacity (recovery in compressive strength) of the mortar.

Advances in the science of cement-based materials have resulted in the development of a new generation of material, namely ultra-high performance cementitious composite (UHPCC). The primary improvements of UHPCC are achieved by the removal of coarse aggregate, limiting the water-to-binder ratio and introducing micro fine materials such as silica fume. The present study aimed to investigate the microstructure of UHPCC with and without additional sulfates. For this purpose, two groups of UHPCC were designed at a constant water/binder ratio of 0.174.The first group of UHPCC mixtures was designed with binary blends of Portland cement and silica fume and was reinforced with 2% micro steel fibers by volume. The other group was also designed with binary cementitious blends but without fibers. Each group consisted of five mixes with different SO3 contents of between 0.11% and 4.5% by weight of natural sand. For each mix, the UHPCC samples were either standard cured or steam cured at 80 ˚C over a 48 h. Besides, UHPCs were compared to Portland cement mortars. The microstructures of the UHPC were examined using scanning electron microscopy (SEM). Energy dispersive X-ray analysis (EDX) was also performed. SEM observations showed the existence of non-expansive ettringite in the UHPCC samples containing excessive sulfates.

This study focuses on the early-age shrinkage of ultra-high performance concrete (UHPC) with high-volume mineral admixtures. Two low cement UHPC mixtures, which have similar compressive strength with control mixture, were obtained with high-volume ground granulated blast furnace slag (GGBFS) or fly ash (FA) replacements. The effects of exposure temperature on autogenous shrinkage of sealed specimens and drying shrinkage were studied at early-age (

This study provides a comparative study of the accelerated mortar bar (ASTM C1260-14 and ASTM C1567-13) and RILEM AAR-4 test methods. They were used to evaluate the alkali-silica reaction (ASR) mitigation potential of supplementary cementitious materials (SCMs) and lithium salts. For this purpose, 96 mixtures with two different reactive aggregates were prepared and analyzed by the accelerated mortar bar test (AMBT) and RILEM AAR-4 method. The effect of steam curing was also determined. Despite the factors such as severe test conditions of the AMBT and alkali leaching challenge in the AAR-4, in some cases, meaningful relations were observed between these accelerated test methods. (C) 2018 Published by Elsevier Ltd.

Many tests and methods can be used to assess or verify the self-healing mechanisms of cement-based materials. This study, which is part of wider project, deals with the development and application of a test method for studying the self-healing ability of cementitious composites. The principle of this method lies in the bonding capacity of self-healing products under direct tension loads. A specially designed cylinder specimen was split after 7 days of water curing, and then the two parts of the split specimen were carefully put together immediately. A connector apparatus was designed to keep the surface of each part connected to each other with equal pressure for the "healing" process in water. After 30 days, the specimens were tested by a special direct tension test method to evaluate the bond loads. In addition, the crack-closing ratios were monitored on precracked disc-shaped specimens. The bond loads of 7 different ultra-high-performance concrete (UHPC) mixtures were compared with the crack-closing ratios. The healing process in the novel test, which simulated the self-healing of very narrow cracks, was observed to differ from the crack-closing test method. Considerable bond loads were obtained in both fly ash (308 N) and ground granulated blast furnace slag (GGBFS) (210 N) bearing mixtures. Additionally, the maximum crack-closing ratio (100%) was observed in the GGBFS bearing mixture. (c) 2019 American Society of Civil Engineers.

Yavaş, Altuğ (Balikesir Author), This study investigates the flexural behavior of Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) with hybrid steel fiber referencing the ASTM standard C 1609. Two types of end-hooked fibers in macro fiber concretes and one type short straight fiber in micro fiber concretes were used in mono and hybrid forms. In order to determine the flexural response of UHPFRC, a series of prismatic beam specimens with a dimension of 100 x 100 x 400 mm were tested under the four-point loading and following parameters were compared and discussed in terms of the first cracking load and pattern, flexural strength, deflection capacity, toughness and residual strength capacity under bending loads. The test results showed that as the fiber amount of specimens with the mono fiber increases, in general, better flexural behavior may be ensured. It should be also noted that the hybrid use enhanced the flexural behavior compared to the macro fiber usage.

High temperature resistance is one of the most important parameters which affects the durability and service life of materials. Due to synergistic interaction of different mechanisms, mechanical performance can be lowered especially for the multi-component composite materials exposed to high temperature. Standard or steam cured slurry infiltrated fiber concrete (SIFCON) and slurry specimens were subjected to 300, 600, 750 and 900 degrees C in the scope of present study. Exposing the specimens to 300 degrees C enhanced the mechanical performance, while higher temperatures have detrimental effects on the SIFCON composites such as the loss in the cross section of steel fibers and the destruction of C-S-H structure. Mechanical test results were in accordance with micro-structural and thermal analyses. (C) 2015 Elsevier Ltd. All rights reserved.

Aggregates in many parts of the Middle East are contaminated with gypsum. Therefore, in this study the effects of using gypsum-contaminated natural sand on the compressive strength and expansion of ultra-high performance fiber reinforced cementitious composites (UHPFRCCs) were investigated over a period of one year. Two groups of UHPFRCCs were designed with binary and ternary cementitious blends of Portland cement, silica fume, and/or ground granulated blast furnace slag. Each group consisted of five mixes with different SO3 contents of between 0.11% and 4.5% by weight of natural sand. For each mix, the samples were either water cured or steam cured over a 48 h period. The microstructure of the cementitious composites was also studied by the SEM-EDX. Besides, some findings of UHPFRCCs were compared to those of Portland cement mortars. Test results indicated that UHPFRCCs showed a strength gain, particularly under steam curing and an insignificant expansion even in the presence of excess sulfates, in contrast to the mortars. (C) 2015 Elsevier Ltd. All rights reserved.

The aim of this research is to investigate some of the factors which affect the steel fiber-matrix bond characteristics by means of pull-out test. Ordinary mortar (OM) and reactive powder concrete (RPC) were used as main matrices. The effect of parameters such as end condition of fiber (smooth or hooked-end), embedment length, water/binder ratio, paste phase of RPC, steel-micro fiber, and curing conditions on fiber-matrix pull-out behavior were determined. The fiber-matrix bond characteristics improved as the embedment length of fiber increased, especially for smooth fiber. Low W/C ratio, which enhances the bond strength, reduces the importance of embedment length of the hooked-end fiber. Furthermore, the pull-out peak load and debonding toughness increased as the W/C ratio decreased in the all curing conditions. Microstructural investigation revealed that the congestion of hydration products in fiber-matrix interface improves pull-out behavior remarkably. (C) 2014 Elsevier Ltd. All rights reserved.

Self-compacting repair mortar (SCRM) is a functional material for repair or retrofit applications. Industrial byproducts, such as fly ash (FA) or ground granulated blast furnace slag (GGBFS), can be used to reduce cement dosage and to obtain an eco-friendly material. However, these waste materials may cause durability problems at early ages as a result of curing sensitivity. In this study, the effects of high-volume FA and GGBFS replacement on early-age freeze-thaw (F-T) resistance of SCRM with and without steel microfibers were investigated. The mechanical properties, including fracture energy, were determined after F-T cycles. The fresh state properties and volume stability of the hardened specimens were studied. The results demonstrated that prolonged curing is essential to avoid the loss in mechanical properties due to F-T exposure. SCRM containing high-volume byproducts seem vulnerable to the effect of F-T at early ages, and this negative effect cannot be overcome with steel microfibers.

Steel fibers are commonly used in cement based materials for many applications such as floors, structural elements, repairing works, etc. The chloride-induced corrosion via ingress of seawater may become a risk for performance of the steel fiber reinforced cement based composites. Despite of few studies that have dealt with the corrosion behavior of steel fibers embedded in cement based composites, there are lack of information about the chloride-induced corrosion of steel fibers embedded with sufficient cover in non cracked matrixes, reactive powder concrete, and especially polymer-modified cement based mortars. The open-circuit potential and corrosion current density of single steel fibers embedded in various cement based matrices were monitored after 200, 400, 600, 1200 wetting-drying cycles in 3.5% NaC1 solution. The corrosion and microstructure analyses revealed that the steel fibers can be protected by a well designed mixture, non-cracked matrix and sufficient cover. However, it could be corroded in long terms depending on the type and the dosage of the polymer latex used. In addition, the residual stresses in the deformed regions of the hooked-end steel fibers is critical in terms of the protection against to chloride-induced corrosion. (C) 2017 Elsevier Ltd. All rights reserved.

Çalışmada, betonarme kirişlerde Ultra Yüksek Perfromanslı Lifli Beton (UYPLB) kullanımının, kiriş sünekliği, taşıma kapasitesi, eğilme rijitliği, kırılma şekilleri ve çatlak davranışı üzerindeki etkileri deneysel olarak incelenmiştir. Bunun için dikdörtgen enkesitli 150x250x2500mm boyutlarında test kirişleri kullanılmıştır. Beton içeriğinde düz mikro ve kancalı makro boyutta çelik lifler karma olarak kullanılmış ve ortalama 161 MPa’lık basınç dayanımı elde edilmiştir. Düşük ve yüksek dört farklı çekme donatısı oranına sahip lifli ve lifsiz toplam dokuz adet betonarme test kirişi üzerinde dört noktalı eğilme testleri gerçekleştirilmiş ve salt eğilme davranışları incelenmiştir. Çalışmadan elde edilen sonuçlar, kirişlerde UYPLB kullanımının incelenen parametreler bakımından önemli avantajlar sağladığını göstermiştir.

Ultra-high performance fiber-reinforced concrete (UHPFRC) is a cementitious composite with outstanding mechanical and durability properties. Accordingly, this study focuses on the behavior of reinforced concrete (RC) beams that were strengthened with UHPFRC laminates. Firstly, a preliminary study was carried out at material scale to evaluate the effect of fiber volume on the mechanical properties of UHPFRC, and to select suitable fiber reinforcement ratio for laminate production. In the second step, real-sized laminates were tested to define the bare properties of full-scaled laminate and observe the size effect according to material tests before applying them as a strengthening material. Thereafter, in the final step, flexurally deficient RC beams were strengthened with 30 mm thick UHPFRC laminates using two different bonding methods: gluing with epoxy and mechanical anchoring. In addition, longitudinal reinforcing bars were added into the laminates and their effectiveness was evaluated to improve the success of the applied methods. The results showed that UHPFRC laminate usage, especially in the case of anchorage, is an effective technique to improve the load carrying capacity of RC beams. Moreover, it was observed that adding reinforcing bars into the laminates could improve the efficiency of the applied method remarkably. (C) 2017 Elsevier Ltd. All rights reserved.

In this experimental study, the adverse effect of old cement-mortar composite on self-compacting concrete (SCC) containing recycled concrete aggregate (RCA) were investigated by means of potential aggregate treatment methods so as to promote the maximum RCA utilisation. Although the limited researches focus on the direct utilisation of untreated RCA in SCC, the hitherto unavailable results to the properties of SCCs containing treated RCAs are presented in this paper. Four alternative aggregate surface treatment methods introduced to RCAs are two-stage mixing approach, pre-soaking in HCl solution, water glass dispersion and cement-silica fume slurry. 100% coarse RCA replacement with the natural aggregate was used in SCC mixes having constant cement dosage, fly ash replacement and water-to-binder ratio. The slump flow and T-500 time, V-funnel time, L-box height ratio, viscosity, compressive and splitting tensile strength, and freeze-thaw cycling tests were carried out to identify the effects of these aggregate treatment methods on the key properties of SCC. Test results reveals that self-compactibility characteristics of the concretes are remarkably affected by surface treatment of RCAs. Moreover, the treatment methods of two stage mixing approach and water glass provide more dense and connected microstructures in SEM analysis leading to significant strength improvements compared to the control SCC. (C) 2014 Elsevier Ltd. All rights reserved.

Reactive Powder Concrete (RPC) is characterized by high cementitious material content, very low water to cement ratio and steel micro-fiber reinforcement. This type of cementitious composite has greater ductility, durability and mechanical properties compared to traditional concrete. Abrasion resistance of the composite material is still not well understood, although it has a variety of applications, including bridge deck construction and floor covering. In the scope of this study, three water-to-cement ratios and various micro-fiber volume fractions were investigated. Mechanical properties under steam curing were determined. Cubic specimens with a 71 mm side were prepared for the surface abrasion test by means of Bohme apparatus. In addition, the flexural toughness and Charpy impact tests were performed on unnotched prismatic specimens. A relationship between loss of mass by the Bohme abrasion test and mechanical properties was investigated. Test results indicated that abrasion resistance and mechanical properties can be improved by incorporating steel micro-fiber. The positive effect of fibers can be enhanced by reducing W/C ratio. It seems that RPC has a great potential to use in civil engineering structures subjected to abrasion. Copyright © 2014 VBRI press.

In this study, the effects of recycled glass (RG) and recycled concrete (RC) fine aggregates on acid and sulfate resistance as well as alkali-silica reaction (ASR) expansion of mortar mixture were investigated comparatively. In addition, durability performance of mortar mixtures was supported by microstructural analysis. For this purpose, nine different mortar mixtures were prepared by replacing 25, 50, 75, and 100 wt% of crushed-limestone fine aggregate with recycled aggregates. Except for ASR and acid resistance, the sulfate resistance of mortar mixture improved by using RG aggregate. The performance of mortar in terms of ASR and acid sulfuric resistance increased by increasing RC aggregate replacement level. The ASR expansions in RG mixtures increased by increasing the RG aggregate content up to 100%. The RC mixtures containing more than 50% recycled aggregate, showed better performance than the control mixture in terms of sulfate resistance.

The type and amount of filler are amongst the most important parameters influencing rheological, mechanical and durability characteristics of self consolidating concrete (SCC). Influence of using a limestone powder, the filler portion of reactive basalt filler and a type of class C fly ash on the fresh properties, alkali-silica reactivity and transport properties were investigated in this study. For this purpose, six SCC mixtures having three filler types and two water/powder ratios were prepared. Alkali-silica reactivity was evaluated by conducting RILEM AAR-3 (38 A degrees C) and AAR-4 (60 A degrees C) concrete prism tests. Besides, the mixtures were exposed to permeable void content, sorptivity and chloride ion permeability tests in order to evaluate the transport properties. According to the results, using a high amount of powder from a reactive basalt in SCC mixture led to the highest expansion level and poor transport properties.

The mechanical properties (flexural strength, compressive strength, toughness and fracture energy) of steel microfiber reinforced reactive powder concrete (RPC) were investigated under different curing conditions (standard, autoclave and steam curing). Portland cement was replaced with ground granulated blast furnace slag (GGBFS) at 20%, 40% and 60%. Sintered bauxite, granite and quartz were used as aggregates in different series. The compressive strength of high volume GGBFS RPC was over 250 MPa after autoclaving. When an external pressure was applied during setting and hardening stages, compressive strength reached up to 400 MPa. The amount of silica fume can be decreased with increasing amount of GGBFS. SEM micrographs revealed the tobermorite after autoclave curing. (c) 2010 Elsevier Ltd. All rights reserved.

Mechanical properties (compressive strength, flexural strength, and toughness) of reactive powder concrete (RPC) produced with class-C fly ash (FA) and ground granulated blast furnace slag (GGBFS) were investigated under different curing conditions (standard, autoclave and steam curing) in this study. Test results indicate that, compressive strength of RPC increased considerably after steam and autoclaving compared to the standard curing. On the other hand, it was observed that steam and autoclave curing decreased the flexural strength and toughness. Increasing the GGBFS and/or FA content improved the toughness of RPC under all curing regimes considerably. Furthermore, SEM micrographs revealed dense microstructure of RPC. (C) 2008 Elsevier Ltd. All rights reserved.

Reactive powder concrete (RPC) is an ultra high strength cement-based material. Cement and silica fume (SF) content of RPC are generally rather high compared to the conventional concrete. The aim of this study is to decrease the cement and SF content of RPC using with fly ash (FA) and/or ground granulated blast furnace slag (GGBFS). The effect of these mineral admixtures on compressive strength of RPC has been investigated under autoclave curing. In the first stage, the effect of autoclave time and SF content on compressive strength was determined. In the second stage, SF was gradually decreased and cement was replaced with FA and/or GGBFS at different proportions. The microstructure was investigated by scanning electron microscope (SEM). Test results indicate that, the utilization of FA and/or GGBFS in RPC is possible without significant mechanical performance loss. SEM micrographs revealed the tobermorite having different morphology. (C) 2008 Elsevier Ltd. All rights reserved.

In this study, pulverized fly ash (FA), pulverized granulated blast furnace slag (PS) and silica fume (SF) were quantitatively studied with the incorporation of Portland cement (PC). PC was replaced with FA or PS at specified ratios. Basalt and quartz powder were used as an aggregate in the mixtures. Three different curing methods (standard, autoclave and steam curing) were applied to the specimens. Test results indicate that high strength concrete can be obtained with high volume mineral admixtures. Compressive strength of these mixtures is over 170 MPa. It seems that these mixtures can also be used for reactive powder concrete (RPC) production with some modifications. (c) 2006 Elsevier Ltd. All rights reserved.

Some mechanical and durability properties of composite material produced with by-products of Orhaneli power plant (flue gas desulfurization sludge, fly ash and bottom ash), cement and hydrated lime were investigated. To improve the mechanical properties (compressive and flexural strength) of this material, steam curing was applied and the effect of chemical admixture (high water reducing agent) was investigated. Some physical properties and water resistance of the mixtures were also determined. Furthermore, microstructure of the specimens was investigated using scanning electron microscopy. Finally, to produce construction elements, prototypes of building blocks were manufactured by using some of these mixtures. All kind of power plant wastes (flue gas desulfurization sludge, fly ash, bottom ash) can be utilized with these mixtures, which consist of 90% of coal combustion byproducts. It seems to be a promising material for composite construction elements such as building blocks. (c) 2006 Elsevier Ltd. All rights reserved.

In this study, effects of cement type, cement content and water/cement (W/C) ratio level on the sea water resistance of concrete were investigated. Test samples were exposed to sea water by wetting drying manner. Residual splitting tensile and compressive strength, and chloride penetration depths of specimens after exposure were determined. Besides, energy dispersive spectrometer (EDS) analyses were performed on scanning electron microscope (SEM) images of selected mixtures. Test results indicate that blast furnace slag cement (SC) mixtures have considerably greater resistance to sea water than portland cement (PC) mixtures both from the point of mechanical properties and chloride penetration. (c) 2006 Elsevier Ltd. All rights reserved.

The effects of ASTM Class C fly ash incorporation on mechanical properties and sulfuric acid resistance of concrete has been investigated within the scope of this study. Cement was replaced with fly ash up to 70%. Test results indicate that sulfuric acid resistance of steam-cured concrete could be improved significantly by incorporation of fly ash. Under standard curing conditions, the strength values of high-volume fly ash concretes were satisfactory except 1-day strength. Curing by steam helped to increase the 1-day strength values. However, long-term strength values decreased significantly for concrete mixtures over 30% of fly ash replacement levels. (c) 2005 Elsevier Ltd. All rights reserved.

The effect of steam curing on concrete incorporating ASTM Class C fly ash (FA), which is widely available in Turkey, was investigated. Cement was replaced with up to 70% fly ash, and concrete mixtures with 360 kg/m(3) cementitious content and a constant water/binder ratio of 0.4 were made. Compressive strength of concrete, volume stability of mortar bar specimens, and setting times of pastes were investigated. Test results indicate that, under standard curing conditions, only 1-day strength of fly ash concrete was low. At later ages, the strength values of even 50% and 60% fly ash concretes were satisfactory. Steam curing accelerated the 1-day strength but the long-term strength was greatly reduced. Setting time of fly ash-cement pastes and volume stability of mortars with 50% or less fly ash content were found to be satisfactory for standard specimens. In addition, for steam curing, this properties were acceptable for all replacement ratios. (c) 2004 Elsevier Ltd. All rights reserved.

SIFCON (Slurry Infiltrated Fiber Concrete) can be described as a special type of cement based composite produced with fiber volume fraction values between 5 to 30%. As a result of superior mechanical properties such as compressive, tensile, shear and flexural strengths with extraordinary toughness values, SIFCON can be used in in industrial floors, repair and reinforcement works and military applications such as anti-missile hangers. Mechanical properties of fiber reinforced cement based composites are dramatically influenced by steel fiber–matrix bond characteristics. Many parameters such as fiber type and geometry, matrix strength, curing conditions and properties of fiber-matrix interface affect the fibermatrix bond characteristics. The density of this zone can be increased with supplementary cementitious materials such as metakaolin. In this study the effect of metakaolin and end type of steel fiber on bond characteristics has been investigated. The fiber-matrix bond characteristics were determined by applying single-fiber pull-out test. Utilization of metakaolin has improved the compressive strength and fibermatrix bond characteristics. In addition, hooked-end fiber has a better performance compared to the smooth fiber. ©2014 Usak University all rights reserved.

Reactive Powder Concrete (RPC) is a type of ultra-high performance cement based composite with high strength and ductility. RPC was developed in the 1990s by Bouygues' laboratory in France. It is a special type of concrete which has properly optimized micro grain, binder phase and steel micro-fibers. RPC can achieve compressive strength values between 150–800 MPa, while traditional concrete which is used in current structures usually has 20–50 MPa compressive strength. In addition, its high performance under flexural loads is the most important advantage of RPC in the field of civil engineering. RPC has the potential to compete with steel from the point of aesthetics and structural capability. One of the curing methods to enhance the strength of this composite material is autoclaving. Autoclave curing needs additional SiO2 source to fill micro pores and strengthen hydration products. In the scope of this study, the effect of volume fraction of steel micro-fibers and silica fume dosage as SiO2 source on mechanical properties of RPC under autoclave curing was investigated. High performance cementitious composites were produced with 0%, 1%, and 2% volume fractions of steel micro-fibers. Nine mixtures with three different silica fume dosages were produced. Workability of fresh state and flexural-compressive strengths of hardened specimens were determined. In addition, fracture energies of the mixtures under bending loads were evaluated.

The mechanical properties (compressive and flexural strength) of reactive powder concrete (RPC) have been investigated under autoclave curing and compared with standard water curing condition. Three significant parameters in autoclave curing have been investigated; autoclave temperature, pressure and time. The effects of silica fume and steel microfibers incorporation on mechanical performance were also studied. Test results indicate that;,compressive strength of RPC increases significantly after autoclaving compared to the standard water curing. Autoclave time, temperature and pressure also influenced the mechanical performance of RPC considerably. It can be said that, there is critical duration time for each pressure and temperature conditions. The mechanical properties can be influenced negatively beyond this value. Also, SEM micrographs and mercury porosimetry results revealed the transformation of microstructure of RPC caused by autoclaving process. (C) 2013 Elsevier Ltd. All rights reserved.

Self-compacting repair mortars (SCRM) can flow through the narrow sections without vibration requirement. This study is aimed to search the utilization potential of glass reinforced plastic (GRP) waste powders occurred during repairing ship and vessel. Six mixtures have been prepared with 1%, 2% and 3% GRP waste addition by volume into two different matrices including only cement binder as well as ground granulated blast furnace slag (GGBFS) replaced 50% wt. of the cement binder. Workability of SCRM decreased as a result of GRP waste utilization. GRP wastes have exhibited different mechanical performance and early age autogenous shrinkage depending on the binder. The increment in GRP dosage caused an increase in early age autogenous shrinkage for matrix involving only cement binder while it caused a decrease in autogenous shrinkage value of GGBFS replaced matrix., Kendiliğinden yerleşen tamir harçları (KYTH) dar kesitlerden vibrasyon gerekmeksizin geçebilen ürünlerdir. Tamir ve güçlendirme işlerinde kullanılabilecek nitelikte olan bu harçların yüksek oranda toz içermesi atık değerlendirilmesi açısından fırsat olarak görülebilir. Çalışmada, gemi ve tekne onarımında kullanılan cam lifi takviyeli plastiklerin (CTP) uygulaması sırasında açığa çıkan tozların KYTH içerisinde kullanım potansiyeli araştırılmıştır. Çimento bağlayıcılı ve yüksek oranda (%50) öğütülmüş yüksek fırın cürufu (YFC) ikameli matrislere hacmen %1, %2, %3 CTP katılarak 6 farklı karışım oluşturulmuştur. CTP tozunun KYTH'nın işlenebilirliğini azalttığı, mekanik özelliklere etkisinin ise bağlayıcı matrise göre değiştiği görülmüştür. CTP dozajı arttıkça erken dönem bünyesel büzülmeler sırf çimentolu matriste artarken, cüruf ikameli matriste azalmıştır.

Slurry Infiltrated Fiber Concrete (SIFCON) is a special type of steel fiber-reinforced cement composite! which has superior mechanical properties such as compressive, tensile, shear and flexural strengths with extraordinary toughness values. In this experimental study, the effect of mix proportions of SIFCON matrix (slurry), curing conditions, aspect ratio of steel fiber, embedded length and fiber type on the single fiber pull-out behavior from SIFCON matrix was investigated. Test results indicated that fiber type, embedded length of fiber, curing conditions, fiber end condition, and matrix strength has a considerable effect on fiber-matrix bond. Increasing the diameter of the fiber and improving the curing conditions increased matrix-fiber bond. In addition, increasing bond strength was observed with increasing strength of SIFCON matrix. The pull-out toughness increased by increasing embedded length of fiber. It has been observed that hooked end fibers have shown better interface bond compared to the smooth fibers. (C) 2012 Elsevier Ltd. All rights reserved.

The effect of brass coated steel micro-fiber on mitigating deleterious expansion due to ASR has been investigated in this research. The potentially reactive basaltic aggregate was chosen as a reactive material. Two series of specimens containing different amounts of microfiber were prepared. One of them was cured in 1 M NaOH solution at 80 degrees C, to obtain similar maturity other series were cured in 80 degrees C water up to 120 days. ASR expansion, strength development and toughness properties were observed during 120 days in NaOH solution and results compared with specimens that were kept in water. Test results indicate that steel fibers reduced ASR expansion significantly however it cannot mitigate ASR expansion completely. Furthermore, fibers are effective to prevent the mechanical properties loss due to ASR expansion such as flexural strength, compressive strength and toughness. Micro-structural investigations revealed the reaction products having different morphology (fibrous, rosette type, network appearance, etc.) when the specimens were kept in NaOH solution. (C) 2011 Elsevier Ltd. All rights reserved.

The possibility of producing a reactive powder concrete (RPC) with low cement content was aimed in the scope of this study. Cement was replaced with class-C fly ash (FA) up to 60% for this purpose. Three different curing conditions (standard water curing, autoclave curing and steam curing) were applied to specimens. Two series of RPC composites were prepared with bauxite and granite aggregates. Mechanical properties such as compressive strength, splitting tensile strength, flexural strength and fracture energy of composites were investigated. Test results showed that, compressive strength of 200 MPa can be reached with low cement by using high-volume fly ash. Thermally treated specimens showed compressive strength beyond 250 MPa and high volume fly ash RPC have superior performance. Furthermore, compressive strength values reached up to 400 MPa with external pressure application during setting and hardening stages. © 2011 Elsevier Ltd. All rights reserved., 104I085, This study was supported by the Scientific and Technological Research Council of Turkey (TUBITAK, Project code: 104I085). The authors gratefully acknowledge the TUBITAK. In addition, the authors thank to Mr. Mehmet Yerlikaya from BEKSA-DRAMIX, Mr. Osman Tezel from BASF, Mrs. Nagehan Haldenbilen from MODERN BETON and Mr. İrfan Kadiroğlu from BATI BETON for supplying materials.

The effects of steel fiber alignment and high-volume mineral admixture replacement [Class C fly ash (FA) and ground granulated blast furnace slag (GGBS)] on the mechanical properties of SIFCON (Slurry Infiltrated Fiber Concrete) have been investigated. Ordinary portland cement was replaced with 50% (by weight) FA or GGBS in SIFCON slurriestwo different steel fiber alignments (random and oriented in one direction) were used. Test results showed that FA and GGBS replacement positively affected mechanical properties (compressive and flexural strength and fracture energy) and fiber alignment is an important factor for superior performance. Binary combination of improved matrices (low water/binder ratio and mineral admixture replacement) and proper fiber orientation enhances mechanical performance, particularly flexural properties of SIFCON. Flexural strength and fracture energy of this composite are 138 MPa and 195,815 N/m, respectively. Scanning electron microscope investigations revealed tobermorite-like structures having different morphology such as foiled, fibroushoneycomb with low Ca/Si ratio after autoclaving. Mercury porosimeter tests showed the decreasing of total porosity and pore refinement with FA or GGBS. © 2010 ASCE.

This aricle focuses on the experimental study of the mechanical properties of reactive powder concrete (RPC) that is produced with different aggregates, such as korund, basalt, limestone, quartz, sintered bauxite, and granite. The effects of aggregate type on mechanical properties were investigated under standard, atmospheric, and high-pressure steam curing in this article. The test results indicate that very high compressive strength can be achieved even with low-strength or smooth-surface aggregates; however, superior flexural performance requires high-strength aggregate with rough surface characteristics. A compressive strength of approximately 200 MPa (29 ksi) can be obtained when strong and rough-surface textured aggregate were used under standard curing conditions. Atmospheric and high-pressure steam curing improved the compressive strength significantly. These curing regimes, however, did not considerably improve the flexural performance. Pressure application in fresh state resulted in a great improvement of the compressive strength of RPC, particularly in the case of high-strength and rough-surface textured aggregates. In this way, a compressive strength over 400 MPa (58 ksi) was obtained with bauxite aggregate after pressure application and autoclaving.

The effects of high temperatures up to 900 degrees C on normal strength, water cured and autoclave cured high strength mortars were investigated within the scope of this study. Mechanical properties such as, compressive strength, flexural strength, modulus of elasticity, and weight loss of the specimens were determined. The effect of polypropylene (PP) and steel fibers incorporation on high temperature behavior of high strength mortars were also investigated. Microstructure investigations were also carried out by SEM analyses. Test results indicated that compressive strength of all mixtures increased with increasing temperature up to 300 degrees C. However, above 300 degrees C all specimens showed explosive disintegration except normal strength mortars, and high strength mortars with PP fibers. It seems that, PP fiber inclusion is effective in preventing the explosive spalling behavior of high strength mortars. On the other hand, steel fibers did not improve high temperature resistance. To prevent spalling, minimum PP dosage for autoclave and water cured high strength mortars has been determined as 0.2% and 0.1%, respectively. (c) 2006 Elsevier Ltd. All rights reserved.

In this study, cement has been replaced with a Class C fly ash (FA) in various proportions from 30% to 60%. Durability properties of various self-compacting concrete (SCC) mixtures such as, freezing and thawing, and chloride penetration resistance have been investigated besides mechanical properties within the scope of this study. Similar tests were carried out with the incorporation of 10% silica fume (SF) to the same mixtures. Test results indicate that SCC could be obtained with a high-volume FA. Ten percent SF additions to the system positively affected both the fresh and hardened properties of high-performance high-volume FA SCC. Although there is a little cement content, these mixtures have good mechanical properties, freeze-thaw and chloride penetration resistance. (c) 2007 Elsevier Ltd. All rights reserved.

The effect of incorporating high Volume of Class C fly ash (FA) on mechanical properties of autoclaved SIFCON (slurry infiltrated fiber concrete) has been investigated in this study. Cement was replaced with LIP to 60% FA in SIFCON compositions and three different steel fiber volumes (2%, 6% and 10%) were used. Test results were presented in comparison with the control mix (0% FA and 0% fiber). Mechanical properties were positively affected almost at every FA replacement. Moreover, by increasing the fiber volume, flexural strength and toughness were remarkably increased. This behavior was more pronounced at 10% fiber Volume. At this fiber volume ratio, flexural strength of 55 MPa could be achieved with 60% FA replacement. (c) 2005 Elsevier Ltd. All rights reserved.