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- Bakamwesiga, Hilary, et al.
(författare)
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Impact of environmental exposure on concrete strength in highway bridges in Uganda
- 2014
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Ingår i: Proceedings of the First International Conference on Construction Materials and Structures. - 9781614994664 - 9781614994657 ; , s. 861-870
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Konferensbidrag (refereegranskat)abstract
- Deterioration of concrete structures is a worldwide problem. Environmental exposure is known to affect concrete strength in structures. While moisture affects rebound values by lowering them, carbonation does the opposite. The aim of the study was to determine the in-situ concrete strength of three bridge elements, namely, pier, abutment and deck and evaluate the environmental conditions such as moisture and abrasive forces on the near surface of concrete. Acknowledging that destructive tests on concrete are expensive and time consuming, this research used rebound hammer test -a non-destructive test (NDT) method. The easiness, simplicity and portability of the rebound hammer made it possible to cover all 13 highway bridges in a period of two months. All the study sites were under the management of Uganda National Roads Authority (UNRA). The choice of test locations was based on BS 1881: Part 202. Rebound hammer tests were done on main elements of bridges namely, decks, piers and abutments. Where possible a maximum of 3 test points were chosen for every single test location. In addition to the universal machine calibrations, the rebound values were correlated to the standard concrete cube compressive strength using old concrete factors. Preliminary results show that although there is significant variation in concrete strength in both pier and abutment, the variation is relatively more pronounced in latter. The paper recommends a combined methodology involving the use of several NDTs to come up with sufficiently reliable results. In conclusion, the development of a formal Bridge Management System (BMS) to enable collection of data through regular monitoring and inspection programs would facilitate prioritization of Maintenance, Repair and Rehabilitation (MR&R) strategies.
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| 2. |
- Daerga, Per-Anders, et al.
(författare)
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A complete timber building system for multi-storey buildings
- 2014
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Ingår i: Construction Materials and Structures. - : IOS Press. - 9781614994664 ; , s. 1164-1171
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Konferensbidrag (refereegranskat)abstract
- The Masonite Flexible Building (MFB) system is a complete timber building system for commercial and residential multi-storey houses. The system is for tall and large buildings with long floor spans. The MFB system uses prefabricated wall, floor and roof elements which are delivered in flat packages and erected on the construction site. The MFB system might be classified as a panel construction, where the load-carrying structure consists of composite lightweight timber I-beams mechanically integrated with a composite laminated wood panel called PlyBoard T. The I-beams and the panel form a strong and rigid carcass for wall and floor elements, making the system well suited for high rise construction. A key feature of the MFB system is the connection technique which enables swift erection of the system units on site. The PlyBoard T panels are provided with a continuous slot along the periphery. The slot is used as a general connection interface for the joining of the wall elements. The floor elements are suspended and hooked onto the bearing walls using sheet steel hangers, allowing swift assembling of the floor deck and enabling direct vertical wall-to-wall load transfer parallel to grain. The paper presents the construction principles, system components and units, erection technique, functional and architectural aspects of the Masonite Building System.
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| 3. |
- Saeidpour, Mahsa, et al.
(författare)
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Comparison of moisture equilibrium of cement-based materials in presence of slag and silica fume in different wetting and drying cycles
- 2014
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Ingår i: Proceedings of the First International Conference on Construction Materials and Structures. - 9781614994664 - 9781614994657 ; , s. 813-818
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Konferensbidrag (refereegranskat)abstract
- Water vapor sorption isotherms are essential data in models to predict the service life of the cement based structures. The knowledge about sorption isotherms in the presence of supplementary cementitous materials (SCMs) is limited. This study investigates the influence of water to cement ratio (0.4, 0.5 and 0.6), and the presence of two SCMs (70% slag and 10% silica fume) on sorption isotherm in hygroscopic and above hygroscope RH ranges for paste and mortars. Dynamic vapor balance in hygroscopic rang and pressure plates above hygroscopic range are used to generate sorption isotherms. Based on Jennings model (CM-II) for C-S-H structure, desorption isotherms are divided to different parts in which different pores are emptied. The samples with silica fume and slag have higher moisture content than OPC, but, with higher amount of gel pores and lower amount of capillary pores. At low RH intervals all samples have very similar desorption curves and introduction of SCMs induce slightly increase on BET surface area. Above 30% RH, samples have different desorption curves and the initial desorption is higher than following desorption for all samples.
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