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۱CONTRADICTORY EFFECTS OF SILICA FUME CONCRETES IN SULFURIC ACID ENVIRONMENTS
اطلاعات انتشار: سومین کنفرانس بین المللی بتن و توسعه، سال
تعداد صفحات: ۱۴
In certain industrial activities sulfuric acid is used during the production process, which may cause degradation of concrete structures. Another important phenomenon where sulfuric acid is responsible for concrete corrosion is biogenic sulfuric acid corrosion, which occurs often in sewer systems. Therefore, researchers used sulfuric acid solutions to simulate of such aggressive environments. Also, they used suitable cement replacement materials such as silica fume to improve acid resistance of concretes. But some researchers reported lowest
susceptibility of concrete containing silica fume to corrosion at such environments while the other groups reported unsuitable performance of silica fume. In this paper, control specimens and specimens containing 8% silica fume as cement replacement materials were immersed in sulfuric acid solutions with pH of 1.0 and 2.0. The dense packing of siliceous aggregates and cementitious materials
were used to achieve low porosity concretes. They were periodically examined for appearance and measured for mass change up to 315 days. Total porosity of samples at the age of 90 days was measured. Results show that the porosity plays an important and twofold role in the mass loss of mortar specimens immersed in sulfuric acid solutions. In low pHs such as 1.0 corrosion rate of low porosity concretes is more than that of high porosity concretes. But, in the high pHs such as 2.0 corrosion rate of low porosity concretes is less than that of the high porosity concretes. In the low and high pHs of sulfuric acid solutions internal and external or surface degradations were observed respectively. Contradictory results were obtained for the concretes containing silica fume because of its effect on the porosity and the production of silica gel at ITZ by reacting of portlandite. Investigations by optical microscopy on thin section samples indicate that the use of silica fume makes mixtures more homogeneous and hence lowers the corrosion rate in sulfuric acid environments.<\div>

۲WORLD RECORD: THE LONGEST CONCRETE PLATE WITHOUT JOINTS, WITHOUT CRACKS
نویسنده(ها): ، ،
اطلاعات انتشار: سومین کنفرانس بین المللی بتن و توسعه، سال
تعداد صفحات: ۱۱
The German electron synchrotron DESY (Deutsches Elektronen–Synchrotron) in Hamburg is a centre for research into the structure of matter. DESY uses the accelerator PETRA (Positron–Elektron–Tandem–Ring–Anlage) as an intense synchrotron radiation sources for a broad spectrum of tests with electromagnetic radiation. The tests must take place on an extremely stiff and smooth concrete plate. The plate had to be 280 m long, 24 m wide and 1 metre thick. The plate should not get any joints and has to remain free of cracks because of the resistance demanded. The plate has to be produced monolithically, that is on behalf of the huge dimensions and properties world record. The positioning of the plate on a sliding bitumen layer and the use of steel fibre concrete have been the prerequisites for a successful performance under such challenging requirements.<\div>
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