Document Type : Research Studies
Authors
1
Associate professor, Construction Research Institute, National Water Research Center, Delta Barrages, 13621, Egypt
2
Professor and Deputy-Director of Construction Research Institute, National Water Research Center, Delta Barrages, 13621, Egypt.
3
Professor and Director of Construction Research Institute, National Water Research Center, Delta Barrages, 13621, Egypt.
Abstract
The design, and sequences for construction with Roller Compacted Concrete Dams, “RCCD” are considerably different from conventional mass concrete construction. This paper describes design mixes, model construction, monitoring system and thermal measurements analysis for RCCD constructed using the available low cost local materials. Trial laboratory concrete mixtures were conducted to define the best different RCCD proportions in the first stage. Twelve mixtures with fly ash of different cement replacement percentages (0%, 50%, and 60%) divided into two groups, each one includes six concrete mixtures that were designed with water/cementitious materials ratio, w/cm of 1.0 and 0.9 for the first and second group respectively, two contents of cement of 150 kg/m3 and 120 kg/m3 were also examined. Tests were performed for determining fresh and hardened concrete properties. In the second stage, based on the laboratory results, RCCD model was then constructed. Descriptions of all construction stages, different instrumentations installed for dam monitoring system and temperature measurements results are also conducted and presented in this research. Test results clarify how fly ash interacts with Portland cement; its effects on the fresh and hardened concrete properties; and how RCCD thermal analysis is affected and proportioned with fly ash. Fly ash, due to its pozzolanic and cementitious properties, is a suitable replacement material for cement to reduce cement usage without invading concrete properties and can contribute to strength gain and may improve performance of fresh and hardened concrete. By using natural pozzolans, fly ash, in the massive concrete dam construction, it is possible to achieve a reduction of the temperature rise without any undesirable effects such as bleeding, tendency to segregate, and tendency to increase permeability. It also reduces the thermal stresses by reducing the heat of hydration. The obtained results indicated that RCC could be effectively produced using the available local Egyptian materials.
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