Wyniki wyszukiwania - BazTech

1

Self-curing concrete under sulfate attack

Bashandy A. A.

Archives of Civil Engineering

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2016

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Vol. 62, nr 2

3--18

EN

Self-curing concrete SC is a concrete type that can be cured without using any external curing regimes. It can perform by several methods such as using lightweight aggregate or chemical agents. In this research chemical curing agent is used to produce SC. This paper reports the results of a research study conducted to evaluate the effect of sulfates on the performance of self-curing concrete compared to ordinary concrete. Samples are immersed in sodium sulfate Na2S04 solution of 4% concentration. Results are measured in terms of compressive strength, tensile strength, flexural strength and mass loss. It was found that the rate of strength loss is noticed at ordinary concrete compared to SC concrete. Sulfate resistance is improved when using self-curing concrete. This improvement appears to be dependent on using a chemical curing agent.

PL

Niniejsza praca przedstawia wyniki badania przeprowadzonego w celu ocenienia wpływu siarczanów na beton samoutwardzalny, w porównaniu z betonem zwykłym. Beton samoutwardzalny SC, jest typem betonu, który utwardzany jest bez jakichkolwiek zewnętrznych systemów utwardzania. Można to osiągnąć stosując kilka metod, jak użycie lekkiego kruszywa, czy też środków chemicznych. W tym badaniu, do produkcji SC wykorzystano chemiczny środek utwardzający. Przygotowano dwie mieszanki betonu. Pierwszą mieszanką SC był beton samo-utwardzalny oparty na poprzednich badaniach. Próbki zostały odlane przy wykorzystaniu zwykłego cementu portlandzkiego, zgniecionego dolomitu o maksymalnym rozmiarze nominalnym 12,5 mm, sortowanego piasku ze współczynnikiem delikatności 2,40, pyłem krzemionkowym jako 15% zawartości cementu, super-plastyfikatorem "Addicrete BVF" jako 0,07% zawartości cementu, chemicznym utwardzaczem "Glikolem polietylenowym PEG200" jako 2% składniku cementu oraz z wodą kranową do pierwszej mieszanki betonu. Druga mieszanka betonu CC, jest zwyczajnie utwardzaną mieszanką, o tych samych proporcjach co mieszanka samoutwardzająca, ale bez dodatku chemoutwardzacza "PEG200", aby dać możliwość porównania obu mieszanek. Próbki zostały odlane przy wykorzystaniu dwóch użytych mieszanek, SC i CC. Drugą mieszanką betonu była CC, utwardzana przez 28 dni.

2

Repairing and strengthening of elliptical paraboloid reinforced concrete shells with openings

Meleka N. N., Safan M. A., Bashandy A. A., Abd-Elrazek A. S.

Archives of Civil Engineering

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2013

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Vol. 59, nr 3

401--420

EN

This investigation is carried out to evaluate the repair and strengthening the techniques of elliptical paraboloid reinforced concrete shells with openings. An experimental program of several different techniques in repair and strengthening is executed. The materials, which are considered for strengthening, are; Glass fiber reinforced polymers GFRP at different position of the shell bottom surface, steel strip and external tie. They loaded by four concentrated loads affected on the corners of the opening. The initial and failure loads as well as the crack propagation for the tested shells at different loading stages, defl ections and failure load for repaired and shells are recorded. A non-linear computer program based on finite element techniques is used to study the behavior of these types of shells. Geometric and materials nonlinearities are considered in the analysis. The efficiency and accuracy of computer program are verifi ed by comparing the program results with those obtained experimentally for the control shell with opening and strengthened shells.

3

Flexural strengthening of reinforced concrete beams using valid strengthening techniques

Bashandy A. A.

Archives of Civil Engineering

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2013

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Vol. 59, nr 3

275--293

EN

This study aims to evaluate the efficiency of strengthening reinforced concrete beams using some valid strengthening materials and techniques. Using concrete layer, reinforced concrete layer and steel plates are investigated in this research. Experiments on strengthening beam samples of dimensions 100x150x1100mm are performed. Samples are divided in to three groups. Group “A” is strengthened using 2cm thickness concrete layer only (two types). Group “B” is strengthened using 2cm thickness concrete layer reinforced with meshes (steel and plastic). Group “C” is strengthened using steel plates. The initial cracking load, ultimate load and crack pattern of tested beams are illustrated. The experimental results show that for group A and B, the ultimate strength, stiffness, ductility, and failure mode of RC beams, with the same thickness strengthening layer applied, will be affected by the mesh type, type of concrete layer. While for group C, these parameters affected by the fixation technique and adhesion type.

4

Economical reactive powder concrete cast using available materials in North Sinai, Egypt

Meleka N. N., Bashandy A. A., Arab M. A.

Archives of Civil Engineering

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2013

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Vol. 59, nr 2

175--195

EN

In this research reactive powder concrete (RPC) was prepared using sand from North Sinai. The mechanical properties of locally cast RPC were investigated and evaluated by studying the effects of using different cement and silica fume contents and new steel fibers’ aspect ratios as reinforcement for RPC. Specimens’ preparation, curing regimes and testing procedures to evaluate the compressive strength, the modulus of elasticity, the indirect tensile strength and the flexural strength were discussed. A compressive strength of 154.5MPa, indirect tensile strength of 11.98MPa, modulus of elasticity of 45.1GPa and flexural strength of 30.26MPa have been achieved for reinforced RPC contains 800 kg/m3 cement content and silica fume content 30% of cement weight. The test results showed some improvements by increasing cement and silica fume contentsas well as adding steel fibers on the compressive strength, modulus of elasticity and indirect tensile strength.