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The use of a natural pozzolan to enhance the properties of self-consolidating concrete
The successful production of self-consolidating concrete (SCC) for use in precast concrete is dependant an striking an appropriate balance between the yield stress and the viscosity of the paste. Specially formulated high range water reducers are used to reduce the yield stress to a point to allow the desired free flowing characteristics of the concrete. However, this alone may result in segregation if the viscosity of the paste is not sufficient to support the aggregate particles in suspension. To achieve the desired viscosity it is customary to use either a high cement content, employ the use of a viscosity-modifying admixture, or both. An alternate methodology is to employ the use of a supplementary cementitious material that can increases the cohesion or viscosity of the paste as well as provide the desired early strength. This paper presents a case study an the work conducted at Rotondo Precast in the development of SCC mixtures utilizing a natural pozzolan to enhance both the SCC properties and the subsequent hardened properties of the concrete. The natural pozzolan used is a calcined shale produced by the Lehigh Cement Company under the trade name XPM. The characteristics of the calcined shale were found to improve the cohesion of the concrete mixture and therefore provide better control of Segregation without the necessity of a viscosity-modifying agent. In addition, the total cementitious content needed in the natural-pozzolan-modified concrete was found to be somewhat lower than the portland cement content required for the conventional SCC mixtures. A natural pozzolan content of 30 % was found to be optimum for preventing segregation and achieving sufficient early age strength. Information is presented an the flow characteristics, strength, and air void system developed in the natural-pozzolan-modified SCC as compared to a straight portland cement SCC. In addition, results an the effect an the ASTM C1202 test, reduction in potential for ASR, and increase in resistance to sulphate exposure are presented.
The use of a natural pozzolan to enhance the properties of self-consolidating concrete
The successful production of self-consolidating concrete (SCC) for use in precast concrete is dependant an striking an appropriate balance between the yield stress and the viscosity of the paste. Specially formulated high range water reducers are used to reduce the yield stress to a point to allow the desired free flowing characteristics of the concrete. However, this alone may result in segregation if the viscosity of the paste is not sufficient to support the aggregate particles in suspension. To achieve the desired viscosity it is customary to use either a high cement content, employ the use of a viscosity-modifying admixture, or both. An alternate methodology is to employ the use of a supplementary cementitious material that can increases the cohesion or viscosity of the paste as well as provide the desired early strength. This paper presents a case study an the work conducted at Rotondo Precast in the development of SCC mixtures utilizing a natural pozzolan to enhance both the SCC properties and the subsequent hardened properties of the concrete. The natural pozzolan used is a calcined shale produced by the Lehigh Cement Company under the trade name XPM. The characteristics of the calcined shale were found to improve the cohesion of the concrete mixture and therefore provide better control of Segregation without the necessity of a viscosity-modifying agent. In addition, the total cementitious content needed in the natural-pozzolan-modified concrete was found to be somewhat lower than the portland cement content required for the conventional SCC mixtures. A natural pozzolan content of 30 % was found to be optimum for preventing segregation and achieving sufficient early age strength. Information is presented an the flow characteristics, strength, and air void system developed in the natural-pozzolan-modified SCC as compared to a straight portland cement SCC. In addition, results an the effect an the ASTM C1202 test, reduction in potential for ASR, and increase in resistance to sulphate exposure are presented.
The use of a natural pozzolan to enhance the properties of self-consolidating concrete
Verwendung eines natürlichen Puzzolans zur Eigenschaftsverbesserung von selbstverdichtendem Beton
Ramsburg, P. (author) / Neal, R.E. (author)
2002
6 Seiten, 3 Bilder, 2 Tabellen, 4 Quellen
Conference paper
English
Engineering Properties of Alkali-Activated Natural Pozzolan Concrete
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