Mixing of high performance concrete: effect of concrete composition and mixing intensity on mixing time

Mazanec, Oliver; Lowke, Dirk; Schießl, P

doi:10.1617/s11527-009-9494-y

Cited by 50 publications

(17 citation statements)

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“…The interfacial transition zone (ITZ) between paste and aggregates is also improved [209]. In fresh state the silica fume addition implies a decrease of the workability, a reduction of the stabilization time during the mixing [153] [154] and also higher cohesion/stability due to its high specific surface.…”

Section: Cementmentioning

confidence: 99%

“…Its addition completes the microgranulometrical curve, providing higher compacity to the structure, restricting the space available for the growth of the portlandite crystals (CH) [187]. The rheological effect is an increase of the stabilization time, but also better stability of the mixture [153] [154].…”

Section: Quartz Flourmentioning

confidence: 99%

“…It is generally assumed that UHPFRC requires intensive mixing [206] [153]. Intensive mixers can reach rotor speeds between 1.5 and 20 m/s [154].…”

Section: Mixersmentioning

confidence: 99%

“…For all these reasons the mixture rheological and mechanical properties may vary significantly depending on the different mixer parameters (type, volume, power…) [73], which determines the mixer efficiency. Adequate properties can be reached casting the concrete in inclined drum intensive mixers, or in conventional medium energy mixers mixing for longer times [153].…”

Section: Mixersmentioning

confidence: 99%

“…Also the beginning of the hydration can start, taking water and then decreasing the fluidity. This may imply a reduction of the compressive strengths [153] [154].…”

Section: Mixing Processmentioning

confidence: 99%

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Dosage optimization and bolted connections for UHPFRC ties

Camacho¹,

Efraím²

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No part of this volume may be produced, stored in retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publishers. Los límites son físicos. Las limitaciones, mentales. Summary Dosage optimization and bolted connections for UHPFRC tiesConcrete technology has been in changeful evolution since the Roman Empire time. It is remarkable that the technological progress became of higher magnitude from the second part of the XX Century. Advances in the development of new cements, the appearance of the fibers as a reinforcement for structural applications, and specially the grand progress in the field of the water reducing admixtures enabled the emergence of several types of special concretes. One of the lasts is the Ultra High Performance Fiber Reinforced Concrete (UHPFRC), which incorporates advances of the Self-Compacting Concrete (SCC), Fiber-Reinforced Concrete (FRC) and Ultra High Strength Concrete (UHSC) technology. This exclusive material requires a detailed analysis of the components compatibility and a high control of the materials and processes. Mainly patented products have been used for the few structural elements carried out so far today, but the costs makes doubtful the development of many other potential applications.In accordance with the previously explained, a simplification of the UHPFRC components and processes is needed. This becomes the first main goal of this Ph.D. thesis, which emphasizes in the use of local available components and simpler mixing processes. Moreover, the singular properties of this material, between ordinary concrete and steel, allow not only the realization of slenderer structures, but also the viability of new concepts unthinkable with ordinary concrete. In this field is focused the second part of the Ph.D. thesis, which develops a bolted connection system between UHPFRC elements. This research summarizes, first of all, the subfamilies belonging to the HPC-UHPC materials. Afterwards, it is provided a detailed comparison between the dosage and properties of more than a hundred of mixtures proposed by several authors in the last ten years of technology. This becomes a useful tool to recognize correlations between dosages and properties and validate or no preconceived ideas about this material.Based on this state of art analysis was performed the later development of mixtures, on Chapter 4, which analized the effect of use of simpler components and processes on the UHPFRC. The main idea was use local components available in the Spanish market, identifying the combinations that provide the best rheological and mechanical properties. Steam curing use was avoided since a process simplification is intended. Diferent dosages were developed to be adapted to various levels of performance, and always trying to be as economical as possible. The concretes designed were selfcompacting and mainly combined two fiber types (hybrid), as the flexural performance was of greater relevanc...

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Section: Cementmentioning

confidence: 99%

Section: Quartz Flourmentioning

confidence: 99%

“…It is generally assumed that UHPFRC requires intensive mixing [206] [153]. Intensive mixers can reach rotor speeds between 1.5 and 20 m/s [154].…”

Section: Mixersmentioning

confidence: 99%

Section: Mixersmentioning

confidence: 99%

“…Also the beginning of the hydration can start, taking water and then decreasing the fluidity. This may imply a reduction of the compressive strengths [153] [154].…”

Section: Mixing Processmentioning

confidence: 99%

See 3 more Smart Citations