Resistance of Alkali Activated Water-Cooled Slag Geopolymer to Sulphate Attack

Ground granulated blast furnace slag is a finely ground, rapidly chilled aluminosilicate melt material that is separated from molten iron in the blast furnace as a by-product. Rapid cooling results in an amorphous or a glassy phase known as GGBFS or water cooled slag (WCS). Alkaline activation of latent hydraulic WCS by sodium hydroxide and/or sodium silicate in different ratios was studied. Curing was performed under 100 % relative humidity and at a temperature of 38°C. The results showed that mixing of both sodium hydroxide and sodium silicate in ratio of 3:3 wt.,% is the optimum one giving better mechanical as well as microstructural characteristics as compared with cement mortar that has various cement content (cement : sand were 1:3 and 1:2). Durability of the water cooled slag in 5 % MgSO4 as revealed by better microstructure and high resistivity-clarifying that activation by 3:3 sodium hydroxide and sodium silicate, respectively is better than using 2 and 6 % of sodium hydroxide

Effect of silica fume on the slag cement containing wet cement dust

274-278The present work aims to study the effect of various amounts of silica fume on the physico-mechanical properties of slag cement with 5% raw cement dust. Slag cement is substituted by 4, 8 and 12% silica fume. The results reveal that the increase of silica fume tends to increase the water of consistency. On the other side, 4% silica fume decreases the setting time (initial and final) . 8 and 12% silica fume tend to lengthen the setting time due to the increase of mixing water. The free lime content increases up to 7 days then decreases for all mixes. As the amount of silica fume increases the free lime content decreases. Also, the combined water content increases with the amount of silica fume. The compressive strength of cement paste decreases with silica fume due to the increase of mixing water

Membrane Stabilitiy and Removal of Cobalt from Waste Solution Using Liquid Emulsion Membrane

Abstract: A Liquid Emulsion Mmenrane (LEM) containing Cyanex 301 as a carrier and Span 80 as a surfactant was used for the extraction of Co-(II) from nitric acid solution. Various diluents were tested and cyclohexane was found the most effective diluent in the cobalt extraction. The effect of different factors affecting the permeation of cobalt through LEM (e.g pH of the extrenal phase, type and concentration of stripping internal phase, the equilibrium time, and Cyanex 301 conentration) were investigated. The effects of surfactant types and cocentrations on the stbility of LEM were also studied. It was found that the optimum conditions for cobalt extraction using 8% Cyanex 301 were as follows; 3M HCl as an internal phase, 4% span 80 as a surfactant and by using the best conditions 10 ml of prepared LEM can extract about 96.86% of 1 gm/l of cobalt in Nitric acid solution after 5 min. in the reactor tank

دراسة عملية التأدرت لأسمنت خبث الأفران العالية والأسمنت الحديدي باستخدام ظاهرة موسباور

Mossbauer spectra have been measured for the hydrated blast-furnace slag cement and Portland cement pastes at different times of hydration of 1. 3. 7. 28 and 90 days. The spectra showed the existence of iron atoms, Fe3 (T) and Fe3 (0) states of iron. It was found that, as the time of hydration was increased, the Fe3 (0) content decreased, while the Fe3 (T) content increased. The Fe' (T) /SFe34" percentage was calculated for the two types of cement as a function of the time of hydration. A correlation has been found between this ratio and the compressive strength of the hardened cement paste.تم في هذا البحث دراسة أطياف موسباور لكل من عجائن أسمنت خبث الأفران العالية والإسمنت البورتلاندي بعد التأدرت لفترات زمنية مختلفة (يوم ، ثلاثة أيام ، سبعة أيام ، ثمانية وعشرون يوما ، تسعون يوما) ولقد أظهرت نتائج تحليل بارامترات موسباور لأطياف هذه العجائن أن هناك نقص في محتوى أيونات الحديديك في المواقع ثمانية التأذر وزيادة أيونات الحديديك في المواقع رباعية التأذر وذلك بزيادة زمن التأدرت . وقد تم حساب النسبة المئوية لمحتوى أيونات الحديديك رباعية الترابط إلى المحتوى الكلي لأيونات الحديديك عند أزمنة التأدرت المختلفة لكل من نوعي الإسمنت تحت الدراسة ، وأمكن إيجاد علاقة بين قوة تحمل الضغط الميكانيكي للعجينة المتصلدة وقيم درجة التأدرت المحسوبة من هذه النسبة المئوية (ح+3/ مجموع ح +3)

Physico-mechanical properties of high performance concrete using different aggregates in presence of silica fume

Heavy weight high performance concrete (HPC) can be used when particular properties, such as high strength and good radiation shielding are required. Such concrete, using ilmenite and hematite coarse aggregates can significantly have higher specific gravities than those of concrete made with dolomite and air-cooled slag aggregates. Four different concrete mixes with the same cement content and different w/c ratios were designed using normal dolomite aggregate, air-cooled slag by-product and two different types of iron ore aggregates. High performance concrete (grade-M60) can be achieved using superplasticizer to reduce the water/cement ratio; the effect of SF on the performance of concrete was studied by addition of 10% silica fume to the total cement content. The physico-mechanical properties of coarse aggregates and hardened concrete were studied. The results show that, Ilmenite coarse aggregate gives higher physical and mechanical properties than the other aggregates. Also, addition of 10% silica fume developed a stronger and a denser interfacial transition zone (ITZ) between concrete particles and the cement matrix. Crushed air-cooled slag can be used to produce a high-strength concrete with better mechanical properties than corresponding concrete made with crushed hematite and ilmenite. Heavy density concrete made with fine aggregates of ilmenite and air-cooled slag are expected to be suitable as shielding materials to attenuate gamma rays

Studies of Surface Area and Pore Structure on Portland Cement Produced in Bajil and Amran, Yemen

Portland cement pastes of various porosities were prepared using water/cement ratios of 0.30, 0.35, 0.40, 0.45, 0.50 and 0.55; and were hydrated for various time intervals ranging from 0.021 to 28 days.  Pore structure and VL–t plots (plots of volume vs. thickness) of the hardened cement pastes were measured using nitrogen gas as the adsorbate. The results were found to be related to the mechanism of hydration as controlled by the pore system of the hardened pastes. Type ІІ adsorption isotherms of nitrogen were obtained for all hardened cement pastes. The adsorption-desorption isotherms indicated the existence of closed hysteresis loops for most of the investigated samples and in some other cases, these isotherms were fully reversible