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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 34 Abstracts search results
Document:
SP288
Date:
October 1, 2012
Author(s):
Editor: V.M. Malhotra
Publication:
Symposium Papers
Volume:
288
Abstract:
This CD contains 33 papers presented at the Tenth International Conference of Superplasticizers and Other Chemical Admixtures in Concrete held in Prague, Czech Republic, in October 2012. Topics include Synthesis, Characterization, and Dispersing Performance of a Novel Cycloaliphatic Superplasticizer; Compatibility between Polycarboxylate and Viscosity-Modifying Admixtures in Cement Pastes; Aspects of Gypsum-Free Portland Cement; A Novel Type of PCE Possessing Silyl Functionalities; and much more. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-288
DOI:
10.14359/51684135
SP288-02
September 14, 2012
Marta Palacios, Robert J. Flatt, Francisca Puertas, and A. Sanchez-Herencia
Superplasticizers and viscosity-modifying admixtures (VMA) are often combined in the production of self-compacting concrete. The former provide high flow¬ability and the latter are being increasingly used to enhance its stability. A deep knowledge of the mechanisms of action of both admixtures is needed for optimizing concrete design and for reducing possible technological problems on site. The aim of the present study is to provide a scientific understanding of the compatibility between a PCE and two different VMA admixtures, starch and welan gum-based. For this, the interaction of both types of admixtures with cement was first studied by determining adsorption isotherms. Rheological tests were also performed and showed that the studied VMAs do not modify notably the plastic viscosity, but they control the stability of cement pastes by increasing the yield stress (up to 100%). Moreover, it was found that the increase of yield stress depends on the mode of VMA addition, reaching higher values when the VMA is added after the PCE.
10.14359/51684218
SP288-18
Christof Schrofl and Viktor Mechtcherine
Superabsorbent polymers (SAP) made of acrylic acid and acrylamide were studied as chemical admixtures for mitigating autogenous shrinkage of high-performance concrete or mortar, respectively. The absorptivity of the particles in saline solutions and in cement pore solution was investigated. Ca2+ in the alkaline solution modified the absorp¬tivity essentially, which closely depended on the polymer structure. Furthermore, the release of internal curing water from SAP particles into the hardening cement-based matrix was monitored by neutron radiography. The kinetics of uptake and release of cement pore solution by SAP and hence, their molecular structure, could be linked with their efficiency in mitigating autogenous shrinkage of a high-strength mortar. Finally, the compressive strength of these mortars was determined. The addition of SAP had no negative effect, but could even lead to an increase in the compressive strength.
10.14359/51684234
SP288-04
Julia Witt and Johann Plank
A series of silylated PCE polymers was prepared by aqueous free radical copo¬lymerization using methacrylic acid, ω-methoxy poly(ethylene glycol) methacrylate ester and N-maleic γ-aminopropyl triethoxy silane (MAPS). The resulting copolymers possess silanol groups from alkaline hydrolysis of the triethoxy silane functionality in cement pore solution and thus can chemically interact with C-S-H phases. It was found that incorpora¬tion of MAPS significantly enhances the dispersing performance of ready mixed type PCEs possessing high grafting density while no improvement was observed for low grafted PCEs common in precast concrete. Adsorption tests revealed that MAPS increases adsorption of highly grafted PCEs, while adsorption of pre-cast type PCEs remains unaffected or even decreases.
10.14359/51684220
SP288-17
Cyril Guerandel, Lionel Vernex-Loset, Gabriel Krier, Michel De Laneve, Laurent Izoret, Christian Pierre, and Jean-Francois Muller
Evidence that materials used by the building industry are not damageable for their environment has become a major issue. In particular, the question of organic admix¬tures released from cement based materials by leaching has to be addressed. This paper presents the results of the work carried out with a leaching test derived from the Soxhlet extractor allowing to accelerate the leaching process of organic admixtures. Studied compound is a Polycarboxylate-co-polyethylene glycol based superplasticizer. Numerous analytical methods have been used in the past to detect traces of this chemical. However, mass spectrometry has not yet been applied for this purpose. The last method has enabled us to demonstrate that during the leaching of concrete samples admixed with usual dosages; organic compounds are not released in the leachates. Additionally, in case of cement pastes with high admixtures dosages, we have shown that the leaching process can be assimilated to surface washing.
10.14359/51684233
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