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Investigation of Hydration Temperature of Alkali Activated Slag Based Concrete
Kubilay Akçaözoğlu,Semiha Akçaözoğlu,Abdullah Açıkgöz 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.8
This paper presents the results of an investigation on the effect of activator type, binder amount and sodium dosage on hydrationheats of Alkali-Activated Slag (AAS) concrete. For the slag activation, sodium hydroxide (NaOH) pellets and the mixture ofNaOH+liquid sodium silicate (Na2SiO3) were used at three sodium concentrations, 4%, 6% and 8% by mass of slag. Twenty onedifferent mixtures were prepared for the laboratory tests. In the reference three mixtures, OPC was used as binder and in the otherAAS mixtures Granulated Blast Furnace Slag (GBFS) was used. The binder dosages were 300, 350 and 400 kg/m3 and the waterbinder(w/b) ratio used in the mixtures was 0.50. The compressive strength and hydration temperature of produced concretes weremeasured. The temperature change of specimens measured in every 15 minutes until 120 hours. The test results showed that, thecompressive strengths and hydration temperatures of the mixtures increased depending on increasing binder amount and sodiumdosage. The use of NaOH+Na2SiO3 mixture as activator increased compressive strength but decreased hydration temperature of themixtures. The hydration temperatures of all AAS mixtures were lower than OPC mixtures. Produced AAS concrete with lowhydration temperature can be an alternative in recycled construction material at mass concrete applications.
In vitro shear bond strength between fluorinated zirconia ceramic and resin cements
Merve Çakırbay Tanış,Canan Akay,Turgut Cihan Akçaboy,Murat Şen,Pınar Akkaş Kavaklı,Kadriye Sapmaz 대한치과보철학회 2018 The Journal of Advanced Prosthodontics Vol.10 No.3
PURPOSE. The purpose of this study was to evaluate the efficiency of a gas-phase fluorination method under different fluorination periods through using two resin cements. MATERIALS AND METHODS. 84 zirconia specimens in dimensions of 5 mm × 5 mm × 2 mm were prepared and surface treated with 50 μm aluminum oxide particles or gas phase fluorination for 2 min, 5 min, or 10 min. One specimen in each group was surface analyzed under scanning electron microscope. The remaining specimens were bonded to composite cylinders in dimensions of 2 mm diameter and 3 mm high with Panavia SA Plus or Variolink N. Then, the specimens were stored in 37°C distilled water for 24 hours and shear bond strength test was applied at a speed of 1 mm/min. RESULTS. The highest shear bond strength values were observed in the samples fluorinated for 5 minutes and cemented with Panavia SA Plus. Variolink N did not elicit any statistical differences between surface treatments. Panavia SA Plus resin cement and Variolink N resin cements featured statistically significant difference in shear bond strength values only in the case of 5 minutes of fluorination treatment. CONCLUSION. According to the results of this study, application of 5 minutes of fluorination with 10-methacryloyloxydecyl dihydrogen phosphate monomer (MDP) containing Panavia SA Plus resin cement increased the resin bond strength of zirconia. Fluorination of the zirconia surface using conventional resin cement, Variolink N, did not lead to an increase in bond strength.
A critical review of slag and fly-ash based geopolymer concrete
Tülin Akçaoğlu,Beste Çubukçuoğlu,Ashraf Awad 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.24 No.5
Today, concrete remains the most important, durable, and reliable material that has been used in the construction sector, making it the most commonly used material after water. However, cement continues to exert many negative effects on the environment, including the production of carbon dioxide (CO2), which pollutes the atmosphere. Cement production is costly, and it also consumes energy and natural non- renewable resources, which are critical for sustainability. These factors represent the motivation for researchers to examine the various alternatives that can reduce the effects on the environment, natural resources, and energy consumption and enhance the mechanical properties of concrete. Geopolymer is one alternative that has been investigated; this can be produced using aluminosilicate materials such as low calcium (class F) FA, Ultra-Fine GGBS, and high calcium FA (class C, which are available worldwide as industrial, agricultural byproducts.). It has a high percentage of silica and alumina, which react with alkaline solution (activators). Aluminosilicate gel, which forms as a result of this reaction, is an effective binding material for the concrete. This paper presents an up-to-date review regarding the important engineering properties of geopolymer formed by FA and slag binders; the findings demonstrate that this type of geopolymer could be an adequate alternative to ordinary Portland cement (OPC). Due to the significant positive mechanical properties of slag-FA geopolymer cements and their positive effects on the environment, it represents a material that could potentially be used in the construction industry.