Building Research Institute, Egypt

Cairo, Egypt

Building Research Institute, Egypt

Cairo, Egypt
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Madani H.,K. N. Toosi University of Technology | Bagheri A.,K. N. Toosi University of Technology | Parhizkar T.,Building Research Institute, Egypt
Cement and Concrete Research | Year: 2012

This study reveals that the nanosilica hydrosols with higher specific surface areas had faster pozzolanic reactivity, especially at early ages; moreover, the results are indicative of the accelerating influence of nanosilicas and silica fume on the hydration of cement. Faster initial and final setting times observed for cement pastes containing nanosilicas are consequence of these mechanisms. However, less hydration degree of cement compared to the plain paste was observed at age of 7 days and after. This can be attributed to the entrapment of some of mix water in the aggregates of nanosilicas formed in cement paste environment, making less water available for the progress of cement hydration. The same mechanism is believed to be responsible for the reduction of flowability of cement pastes. © 2012 Elsevier Ltd.

Jamshidi M.,Building Research Institute, Egypt | Ramezanianpour A.A.,Amirkabir University of Technology
Construction and Building Materials | Year: 2011

Asbestos fibers have been used in cement based materials to improve tensile strength and controlling crack formation and propagation. Asbestos-cement sheets are produced by the Hatschek technique in a number of developing countries. Due to the health and safety issues in the asbestos products, attempts have been made to substitute other fibers using the Hatschek system for cement sheets. The quality and homogeneity of the products depend on the type of fibers and varies substantially in the Hatschek system during production. In this investigation acrylic and glass fibers in separate and hybrid forms were used for manufacture of flat and corrugated sheets. Higher strength and ductility were obtained for the sheets containing glass fibers. Performance was even better when hybrid system of acrylic and glass fibers was used. The hybrid system was used for production of fiber-cement sheets in factory. This system is proposed as an appropriate alternative for substituting asbestos in the Hatschek process. © 2010 Elsevier Ltd. All rights reserved.

Najimi M.,Building Research Institute, Egypt | Sobhani J.,Building Research Institute, Egypt | Pourkhorshidi A.R.,Building Research Institute, Egypt
Construction and Building Materials | Year: 2011

Sulfate attack is one of several chemical mechanisms of concrete deterioration. Exposure of concrete structures in the sulfate environments may lead to detrimental chemical, microstructural, and physical changes in the concrete matrix, resulting in serious deteriorations and service life reduction. Partial replacement of cement with slag is one of the efficient methods for improving concrete resistance against sulfate attack. In this paper the performance of copper slag contained concrete in sulfate solution is investigated. In this regard, an experimental study including expansion measurements, compressive strength degradation and microstructural analysis were conducted in sulfate solution on concretes made by replacing 0%, 5%, 10% and 15% of cement with copper slag waste. The results of this study emphasized the effectiveness of copper slag replacement in improving the concrete resistance against sulfate attack. © 2010 Elsevier Ltd. All rights reserved.

Farahbod F.,Building Research Institute, Egypt | Mostofinejad D.,Isfahan University of Technology
Composite Structures | Year: 2011

The present paper describes an experimental investigation of moment redistribution of continuous beams in 6 two-span RC frames strengthened with CFRP laminates. Design variables were the number of CFRP layers, and the configuration of the laminates. To prevent debonding of the CFRP laminates at the end region and at the beam-column connection, U-shaped CFRP anchorages were provided for all of the frame specimens. Furthermore, mechanical anchorages of steel plate strips and bolts were added to the laminates in one frame of these specimens. Test results showed that a maximum moment redistribution of 56% occurred in the strengthened frames. Furthermore, the load carrying capacities of the strengthened frames increased from 20% to 38%, while the flexural capacities had an increase of 9% to 20% and 35% to 55% at the negative and positive moment regions, respectively. © 2010 Elsevier Ltd.

Najimi M.,Building Research Institute, Egypt | Pourkhorshidi A.R.,Building Research Institute, Egypt
Magazine of Concrete Research | Year: 2011

In this paper, the effects of using copper slag wastes as a supplementary cementitious material on mechanical properties and durability aspects of concrete are studied. To this aim, mixtures are made by employing 5, 10 and 15% copper slag as cement replacement and the strength properties, water penetration, chloride ion permeability, sulfate expansions and alkali-silica reaction are investigated. The results indicate that using copper slag waste decreases mechanical stresses and in turn expansion during exposure in sulfate solution. Additionally, copper slag reduces expansion induced by alkali-silica reactions. These durability improvements are accompanied by an appropriate effect on penetration, with only a minor decrease in mechanical properties. Thomas Telford Ltd © 2011.

Kaveh A.,Iran University of Science and Technology | Shakouri Mahmud Abadi A.,Building Research Institute, Egypt
Journal of Constructional Steel Research | Year: 2010

In this study, cost optimization of a composite floor system is performed utilizing the harmony search algorithm and an improved harmony search algorithm. These algorithms imitate the musical performance process that takes place when a musician searches for a better state of harmony, similar to the optimum design process which looks for the optimum solution. A composite floor system is designed by the LRFD-AISC method, using a unit consisting of a reinforced concrete slab and steel beams. The objective function is considered as the cost of the structure, which is minimized subjected to serviceability and strength requirements. Examples of composite floor systems are presented to illustrate the performance of the presented algorithms. © 2010 Elsevier Ltd. All rights reserved.

Rashad A.M.,Building Research Institute, Egypt
Journal of Cleaner Production | Year: 2015

In this study, cement has been partially replaced with a Class F fly ash (FA) at a level of 70% to produce high-volume fly ash (HVFA) concrete (F70). F70 was modified by partially replacing FA with silica fume (SF) at levels of 10% and 20%, by weight. All HVFA concrete types were compared to the neat Portland cement (PC) concrete. After curing, the specimens were exposed to elevated temperatures ranging from 400 C to 1000 C with an interval of 200 C. Weight and compressive strength before and after firing have been thoroughly explored. The various decomposition phases formed were identified using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated higher relative strength of all HVFA concrete types. F70 exhibited the highest relative strength. The SF blends exhibited good fire performance up to 600 C, then severe degradation in the residual strength was observed at 800 and 1000 C. © 2014 Elsevier Ltd. All rights reserved.

Kaveh A.,Iran University of Science and Technology | Shakouri Mahmud Abadi A.,Building Research Institute, Egypt
International Journal of Civil Engineering | Year: 2011

Cost optimization of the reinforced concrete cantilever soil retaining wall of a given height satisfying some structural and geotechnical design constraints is performed utilizing harmony search and improved harmony search algorithms. The objective function considered is the cost of the structure, and design is based on ACI 318-05. This function is minimized subjected to design constraints. A numerical example of the cost optimization of a reinforced concrete cantilever retaining wall is presented to illustrate the performance of the presented algorithms and the necessary sensitivity analysis is performed.

Karami M.,University of Tehran | Akhavan Bahabadi M.A.,University of Tehran | Delfani S.,Building Research Institute, Egypt | Ghozatloo A.,Research Institute of Petroleum Industry RIPI
Solar Energy Materials and Solar Cells | Year: 2014

Nanofluids are found to have good stability and useful optical and thermal properties as direct sunlight absorbers in solar collectors. The inherent hydrophobic nature of carbon nanotubes was overcome using a new dispersion procedure (treating carbon nanotubes with base media) to prepare nanofluids. To the authors' knowledge, this is the first application of aqueous suspension based on alkaline functionalized carbon nanotubes as an absorber fluid in a sunlight harvesting device. Dispersion stability and optical properties of the nanofluid were estimated. Spectral absorbance analysis confirms the relative stability of prepared nanofluids versus sediment time. The extinction coefficient of aqueous suspensions of functionalized carbon nanotubes shows remarkable improvement compared to the base fluid even at low particle loadings. We also demonstrate thermal conductivity improvements of up to 32% by adding only 150 ppm functionalized carbon nanotubes to water as the absorbing medium. Their promising optical and thermal properties, together with the appropriate stability of nanofluids, make them very interesting for increasing the overall efficiency of low-temperature direct absorption solar collectors. © 2013 Elsevier B.V.

Farmahini-Farahani M.,Building Research Institute, Egypt | Delfani S.,Building Research Institute, Egypt | Esmaeelian J.,Building Research Institute, Egypt
Energy | Year: 2012

In this paper, an exergy analysis is applied to indicate the exergy efficiency and irreversibility of common models of evaporative cooling. Exergy analysis of conditioned air are based on the results of experimental investigations on the direct, indirect, and two-stage indirect/direct evaporative cooling for six cities in Iran, each having various weather conditions. For this purpose, exergy balances of three cooling methods are derived. The results obtained reveal that for a comprehensive efficiency analysis, both the first and second law of thermodynamics should be considered. Furthermore, the direct evaporative coolers work best in temperate and dry climate with estimated exergy efficiency of 20%. The indirect evaporative coolers are more efficient in hot and dry climate with approximate exergy efficiency of 55%. The indirect/direct evaporative coolers are better choice for hot and semi-humid climate with exergy efficiency of about 62%. © 2012 Elsevier Ltd.

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