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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.