THE PERFORMANCE OF DIFFERENT WATER-REDUCING ADMIXTURES IN CONCRETE

Bu çalışmada altı değişik ticari akışkanlaştırıcının betondaki performansları incelenmiştir. Çalışma çerçevesinde değişik akışkanlaştırıcılar ile betonlar üretilmiş ve üretilen betonların çökme, priz başlangıç ve bitim süreleri, hava yüzdeleri ile 3, 7 ve 28 günlük basınç dayanımları belirlenmiştir. Beton üretiminde; dozaj, agrega kompozisyonları ve miktarları, çökme değeri sabit seçilmiştir. Ayrıca elde edilen deney sonuçları ilgili şartnamelerle karşılaştırılmıştır. Çalışmada kullanılan akışkanlaştırıcılar aynı esaslı olmalarına rağmen aynı agrega, aynı çimento ve aynı dozaj ile işlenebilme ve dayanım açısından birbirinden farklı sonuçlar vermiştir. Akışkanlaştırıcı katkılı betonlarda üretimden sonraki saatlerde işlenebilme problemleri ile karşılaşılabileceği de görülmüştür. Bu handikap dışında, bu çalışmada kullanılan katkılar genelde şartnamece aranan nitelikleri sağlamaktadır. In this study the performance of six different commercial water reducing agents in concrete were investigated. The slump, setting times, air content and 3, 7 as well as 28 day compressive strengths of the concrete mixtures both containing admixtures and control ones were determined. In all concrete mixtures, cement content, aggregate content, aggregate grading and slump were kept constant. The test results were compared with related specification requirements. Although the cement content and slump of the concrete mixtures as well as the base of the water reducing agents were same, the behaviour of the admixtures as compared to the workability and strength of the concrete mixtures were different. The slump loss of the mixtures containing water reducing agents was found to be a major problem from practice point of view. Except for the disadvantage of slump loss, other specification requirements for mixtures containing admixtures were observed to be satisfactory

The Portrayal of Force, Fraud, and Coercion Within Northern Ohio Federal Sex Trafficking Trials -- 2010-2013

Human trafficking is often considered to be one of the three largest criminal enterprises worldwide, ranking beside the sale of illegal drugs and illicit firearms (Bales, 2004, 2007 Bales & Doodalter, 2009 Hussein, 2011 Schauer & Wheaton, 2006 Skinner, 2008). National estimates suggest that 100,000-300,000 American, school-aged children are at-risk for sex trafficking (Department of Homeland Security, 2014) while there is only a one percent arrest and conviction record for traffickers (Bales, 2007). This dissertation explored the portrayal of force, fraud, and coercion within federal domestic minor sex trafficking (DMST) trials of Northern Ohio from 2010-2013 so as to gain a greater understanding of the contributing factors that make individuals vulnerable to the phenomenon. DMST occurs when a commercial sex act is induced by force, fraud or coercion, or in which the person induced to perform such act has not attained 18 years of age (U.S. Department of State, 2011). Data were examined via qualitative means by conducting a narrative analysis of existing court documentation of fifteen confirmed DMST cases, guided by critical theory and feminist epistemology. Findings revealed dimensions of individual agency in tension with structural and cultural conditions as well as a complex set of factors contributing to the persistence and legal response to sex trafficking. The examined episodes of DMST were initiated via factors that included fraudulent documents, economic instability, emotional dependency, drug addiction, reliance on an informal/underground economy, and lack of educational attainment. DMST continued through factors including physical force, coercion, indebtedness, feelings of belonging, the leveraging of an intimate relationship, financial arrangements, and the reliance on an informal/underground economy. The episode of DMST was terminated via law enforcement involvement, voluntary departure, familial involvement, ending the use of illegal drugs, and coming into a period of economic stabil

Properties of self-consolidating concrete incorporating coarse recycled concrete aggregate

In this study, the effect of recycled concrete coarse aggregate on properties of self-consolidating concrete was examined. This aggregate was replacing 25%, 50%, 75%, 100% of limestone coarse aggregates. RC aggregate was used in SCC mixtures after 24 hours water saturation and surface dry (SSD). The results have shown that replacement of limestone coarse aggregate with RC aggregate caused the compressive strength decrease. However, the effect on tensile splitting and flexural strength was lower. As a result of this study it was found that it is possible to produce SCC compatible with EFNARC 2002. Moreover; it was observed that the use of RC aggregate in SSD state positively affected the fresh properties of SCC

Çelik lifli betonların darbe direncine agrega maksimum boyutunun etkisi

In this study, the effect of maximum size of aggregate on impact resistance of fiber reinforced concrete were investigated. Using crushed limestone aggregate with 10, 15, 20 and 25 mm of maximum size, 8 different normal-steel fiber reinforced concretes were produced. Water/cement ratio and cement dosage of concrete mixtures are 0.5 and 400 kg/m3, respectively. Hooked-end bundled steel fibers with l/d ratio of 65 and 1.0% fiber volume were used in fiber concretes. After 28 days standard curing, compressive strength, split tensile strength and ultrasonic pulse velocity tests were performed on 150/150/150 mm cube specimens. Additionally, impact resistances of concrete specimens were determined using impact test apparatus described in ACI 544.3R-93. 150x300 mm cylinders were prepared for impact resistance tests. After 28 days curing, these specimens were cut and 150x64 mm special discs were prepared. Impact resistance test were performed on these special discs. Experimental results were evaluated corresponding to presence of steel fiber and aggregate maximum size.Bu çalısmada çelik lifli betonların darbe direncine, agrega maksimum dane boyutunun etkisi incelenmistir. Çalısmada maksimum dane boyutu 10 mm, 15 mm, 20 mm ve 25 mm olan kireç tası kökenli kırma agrega kullanılarak, 8 farklı lifsiz-çelik lifli beton üretilmistir. Üretilen lifli-lifsiz betonlarda; su/çimento oranı 0.50, çimento dozajı 400 kg/m3 olarak sabit tutulmustur. Lifli betonlarda hacimce % 1.0 oranında, narinligi 65 olan, iki ucu çengelli çelik lif kullanılmıstır. Üretilen betonlardan hazırlanan 150 mm ayrıtlı küp örnekler üzerinde, 28 günlük standart kür sonunda tek eksenli basınç, yarmada çekme ve ultra ses deneyleri yapılarak, betonların mekanik özellikleri belirlenmistir. Ayrıca, çalısma kapsamında üretilen betonların darbe testleri ACI 544.3R-93 ‘ce önerilen darbe deney düzeneği kullanılarak gerçeklestirilmistir. Darbe testleri için 150 mm çaplı 300 mm yükseklikli örnekler hazırlanarak 28 gün kür edildikten sonra, çapı 150 mm yüksekliği 64 mm olacak sekilde kesilerek özel diskler hazırlanmıs ve bu diskler üzerinde darbe testleri yapılmıstır. Deneylerden elde edilen sonuçlar lif varlıgı ve agrega maksimum boyutunun değisimine bağlı olarak değerlendirilmistir

Investigation of sulfate resistance and alkali silica reaction in polymer-incorporating mortars

Bu çalışmada, polimer ilaveli harçların sülfat etkisine ve alkali silika reaksiyonuna karşı direnci incelenmiştir. Bu amaçla, bağlayıcı olarak normal portland çimentosu ve stiren-akrilik polimer emülsiyonu kullanılmıştır. Polimer ağırlıkça %0, 5, 10 ve 15 oranlarında çimento yerine ikame edilerek harç karışımları hazırlanmıştır. Hazırlanan harç örneklerinin 28 günlük basınç ve eğilme dayanımları, kılcal yolla su emme, porozite, birim ağırlık gibi özellikleri belirlenmiştir. Ayrıca harç karışımlarının ASTM C1012 standardına göre sülfat direnci, ASTM C1260 standardına göre alkali silis reaksiyonuna karşı direnci saptanmıştır. Polimer ilaveli harçlarda elde edilen sonuçlar kontrol harcı ile kıyaslamalı olarak değerlendirilmiştir.In this study, sulfate resistance and alkali silica reaction in mortars incorporating polymer were investigated. In this aim, normal portland cement and styrene-acrylic polymer emulsion were used. Mortar mixtures were prepared by replacing cement, with 0, 5, 10 and 15% polymer, by weight. 28-days compressive and flexural strength, water absorption and water sorptivity, porosity and unit weight of prepared mortar specimens were determined. Besides, sulfate resistance and alkali silica reaction resistance of prepared mortar mixtures were determined according to ASTM C1012 and ASTM C1260, respectively. Results obtained in polymeric mortar mixtures were comparatively evaluated with control mortar mixture

Farklı kür yöntemlerinin uçucu kül içeren harçların eğilme ve basınç dayanımına etkisi

In this study the effect of accelerated curing on the early flexural and compressive strengths of fly ash mortars were investigated. In the mortar mixtures CEM I 42.5 R type cement and C class C fly ash with different proportions were used. 40/40/160 mm prismatic specimens were prepared from these mortars. The mortar samples cured at 7 different curing conditions. Curing conditions are standard curing, 35 ;deg;C and 85 ;deg;C hot water curing. These curing conditions applied on specimens for different times. Flexural and compressive strengths were performed on the mortar specimens. Obtained test results were comparatively evaluated. The results of this study revealed that, early age strength gain under standard curing conditions due to fly ash inclusion can be compensated by accelerated curing.Bu çalışmada; farklı miktarlarda uçucu kül içeren harçların erken yaşlardaki basınç ve eğilme dayanımlarına hızlandırılmış kür uygulamalarının etkisi incelenmiştir. Harç karışımlarında; bağlayıcı olarak CEM I 42.5 R tip çimento ve değişik oranlarda C sınıfı uçucu kül kullanılmıştır. Üretilen harçlardan 40/40/160 mm ayrıtlı prizmatik örnekler dökülerek 7 farklı kür uygulamasına tabi tutulmuştur. Kür uygulamaları standart kür, 35 °C ve 85 °C'de sıcak su kürü şeklinde ve farklı sürelerde yapılmıştır. Uygulanan kür işlemleri sonrasında harç örnekler üzerinde ortadan tekil yüklemeli eğilme ve eğilme sonrası tek eksenli basınç deneyleri gerçekleştirilmiştir. Elde edilen sonuçlar karşılaştırmalı olarak değerlendirilmiştir. Çalışma sonucunda; standart kür koşulları altında uçucu kül ikamesinin erken yaşta oluşturduğu basınç dayanım kaybının sıcak su kürü uygulaması ile telafi edilebileceği görülmüştür

Effect of elevated temperatures and time on compressive and tensile properties of concretes

23-28In this study, the effects of temperature level and time on the mechanical behaviour of concrete have been investigated. The concrete mixtures are produced using two different water/cement (w/c) ratios: 0.4, and 0.6. 288 cube (100 × 100 × 100 mm) specimens are prepared from these concrete mixtures and cured at 28 days. After standard curing period, specimens are dried in a furnace at 105°C for 4 h. Then the specimens are kept in loboratory for 1 day before exposing to 300, 600 and 900°C for 1, 3, and 5 h. Then compressive strength and split tensile strength are determined. It is concluded that, compressive strength and split tensile strength of the specimens are reduced after the high temperature exposure. Compressive strength losses of tested concretes are reduced with increasing w/c ratio. Remarkable effect is occurred in first 3 h in terms of strength losses