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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 31 Abstracts search results
Document:
SP262-07
Date:
October 1, 2009
Author(s):
M. Palacios, F. Puertas, M.M. Alonso, P. Bowen, and Y.F. Houst
Publication:
Symposium Papers
Volume:
262
Abstract:
The aim of the present study was to determine the adsorption isotherms of polycarboxylate (PC) superplasticizers with different structures on slag-blended cement pastes (with a slag content between 0-75%). Also, their effect on the rheological properties and hydration process has been evaluated. The results indicate the adsorption of PCs decreases slightly as the slag content in the cement increases; however, their fluidizing properties are significantly higher in the slag-blended cement. This effect is mainly attributed to the content of C3A (mineralogical phase with the highest affinity for the PCs) which decreases in slagblended cement. Consequently, the amount of PCs consumed and adsorbed by this mineralogical phase also decreases. In this way, most of the PC admixtures are absorbed onto the silicate phases of the clinker and onto the slag particles, inducing an electrosteric repulsion and the concomitant reduction in yield stress. The rheological results show that the highest increase of the fluidity is caused by the admixture with highest molecular weight concluded to be due to the higher steric repulsion expected for thicker adsorbed layers. As a consequence of the adsorption of the PCs, a delay of the hydration process of the cement pastes has been observed.
DOI:
10.14359/51663225
SP262-08
R.J. Flatt, I. Schober, E. Raphael, E. Lesniewska, and C. Plassard
The increased performance of polycarboxylate superplasticizers is generally explained by the steric hindrance they are intended to develop between cement particles. In fact, direct evidence of this is relatively scarce. The only direct measurements to date have been made by atomic force microscopy on model surfaces of magnesium oxide. In this paper, we report very recent measurements using the same technique but on surfaces of calcium silicate hydrate that constitute a more realistic model system. Furthermore, it is shown that the measured interfacial behavior of superplasticizers can be quantified by a scaling law approach borrowed and extended from polymer physics.
10.14359/51663226
SP262
Editors: P. Gupta, T.C. Holland, and V.M. Malhotra
This Symposium Publication includes 30 papers selected from a conference that took place in Seville, Spain, in October 2009. Topics include Use of a Supplemental Agent to Improve Flowability of Ultra-High Performance Concrete; Performance of Superplasticizers in Blended Cement Systems; and Multifunctional Chemical Admixture to Reduce Quality Control Requirements of Self-Consolidated Concrete. 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-262
10.14359/51663170
SP262-29
D. Platel
The implementation of cement materials is improved by the addition of a polymer called a superplasticizer. In this presentation, we look for the impact of the polymer architecture on the physico-chemistry properties of cement slurries. Initially, we focus on the adsorption of sodium polymethacrylate grafted by poly(ethylene oxide) chains on different types of cement using macroscopic and microscopic techniques. Finally, we measure the fluidity of different cement slurries with the use of new tools such as helicoidal ribbon geometry to explain how polymer architecture controls the performance concrete formulations.
10.14359/51663247
SP262-30
Z. Zhibin, X. Lingling, and T. Minshu
In order to improve dimensional stability of cementitious materials, synergistic effect of shrinkage reducing admixtures (mixture of glycol ethers and siloxane, SRA) and MgO-based expansive agent (MEA) burned at 850, 950, 1050 and 1200°C (1560, 1740, 1920, and 2190°F) for 1 h on the deformation of cement paste cured in water and sealed by polyethylene sheet at 20, 40 and 60°C (68, 104, and 140°F) was investigated. The results illustrated that combined use of MEA(850~950) and SRA could compensate the shrinkage of cement paste effectively, MEA also could make up for the shortage of SRA whose shrinkage-reducing ratio decreased at later age. Then hydration of MEA in the present of SRA was examined by DSC/TG and gravimetry. The results indicated that the presence of SRA retarded the hydration of MEA because SRA decreased the polarity of solvent and adsorbed on the surface of MEA, but with prolonged curing, the hydration degree of MEA with or without SRA tended to be the same.
10.14359/51663248
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