Super-high cementitious roller-compacted concrete (SHCRCC) that have unit cementitious materials content of 220 kg/m 3 or higher can be recognized as "construction friendly RCC". In this study, the proposition of how to reduce construction costs without sacrificing the workability was investigated. To solve the issue, mix proportions replacing the high volume of cementitious materials, cement, and fly ash with stone powder (SP) were surveyed. Based on exhaustive investigations, it was found that the mix proportion can be realized with sufficient tolerance of workability. In the proposed mix proportion, the cementitious materials replaced with SP up to about 100 kg/m 3 provide a large paste volume of 240 to 260 L/m 3 . In addition, it was verified that the SP plays a sufficient role as an alternative to cementitious materials since the compressive and tensile strengths of the RCC, and the watertightness and bond strength at lift joints are the same as, if not better than high cementitious RCC (HCRCC). Reducing cementitious materials also helps to control the temperature rise of the RCC. In the case of a large-scale RCC dam of 150 m in height and 2 million m 3 volume with 5 zones, it is found that a cost reduction is about 25 to 30% for cementitious materials and chemical admixture, and a placement speed is about 20% faster than that of medium cementitious RCC (MCRCC) thanks to a large workability margin.
The Nam Ngiep 1 (NNP1) Hydropower Project in Lao PDR has constructed a 167 m-high roller compacted concrete (RCC) dam. Class C fly ash (FA) procured from the Mae Moh coal-fired power plant in Thailand has been selected as a supplemental cementitious material for the NNP1 RCC dam, to control hydration heat generation and improve workability. Though rarely used globally for RCC, it was found that the Class C FA was acceptable for the NNP1 RCC because it did not undergo a large temperature rise in its early age and because of the relatively high compressive strength of the concrete as the age in the medium-term and long-term as compared with general features of the concrete with Class C FA. To clarify the reaction mechanism for Class C FA, factors affecting the above features of Class C FA are analyzed and evaluated by observing FA particles and concrete core specimens of NNP1 RCC through a variety of devices, including Field Emission-Electron Probe Micro Analysis (FE-EPMA). This paper clarifies the reaction mechanism of the concrete with Class C FA and demonstrates its applicability for RCC dam and other structures.
Synopsis:The Nam Ngiep 1 (NNP1) Hydropower Project in Lao PDR has constructed a 167 m-high roller compacted concrete (RCC) dam. Class C fly ash (FA) procured from the Mae Moh coal-fired power plant in Thailand has been selected as a supplemental cementitious material for the NNP1 RCC dam, to control hydration heat generation and improve workability. Though rarely used globally for RCC, it was found that the Class C FA was acceptable for the NNP1 RCC because it did not undergo a large temperature rise in its early age and because of the relatively high compressive strength of the concrete as the age in the medium-term and longterm as compared with general features of the concrete with Class C FA. To clarify the reaction mechanism for Class C FA, factors affecting the above features of Class C FA are analyzed and evaluated by observing FA particles and concrete core specimens of NNP1 RCC through a variety of devices, including Field Emission-Electron Probe Micro Analysis (FE-EPMA). This paper clarifies the reaction mechanism of the concrete with Class C FA and demonstrates its applicability for RCC dam and other structures. Herein,
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