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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 60 Abstracts search results
Document:
SP178
Date:
June 1, 1998
Author(s):
Editor: V.M. Malhotra
Publication:
Symposium Papers
Volume:
178
Abstract:
SP-178 This Symposium Publication contains the proceedings of the Fourth CANMET/ACI/JCI International Conference held in Tokushima, Japan, in June 1998. Sixty-two refereed papers were accepted for presentation at this conference and for this publication.
DOI:
10.14359/14171
SP178-46
A. Macias, S. Goiii, J. Madrid, J.M. Diez and E. del Castillo
Waste disposal has become a major concern in most industrial countries because of limited sites and strict environmental standards for landfilling. The common cementing material, widely available and used, are normal portland cement, lime and high-calcium fly ashes from coal combustion. Ground granulated blast-furnace slag is also a component in binder formulation of general interest because of its potential for metal immobilization, based on its physical and chemical properties. The present work analyses the immobilization of toxic wastes containing Cd, Pb and Cr in portland cement matrices with 80 % of blast-finnace slag in comparison with plain portland cement matrices. The results show that lower levels of toxic ions in pore solution are obtained for blast-&mace blended cements due to differences in phases formed and the reduction of species to less toxic ones that occurs at the redox potential of slags. Differences in porosity also cause a reduction in metal leaching from slag-blended cements.
10.14359/6014
SP178-47
R.J. Flatt, Y.F. Houst, P. Bowen, H. Hofmann, J. Widmer, U. Sulser, U. Maeder and T.A. Burge
The behavior of superplasticizers has been studied in highly alkaline suspensions of magnesium hydroxide and silica fume, which can be considered as good model system for cementitious systems containing silica fume. Rheology showed that as superplasticizer dosage is increased, suspensions pass from behaving as Bingham fluids to Newtonian fluids. Beyond a critical concentration large dispersed particles sediment due to the absence of yield stress. The critical concentrations required to obtain Newtonian fluids has allowed to elucidate the dependence between adsorption and dispersion. Indeed, dispersion appears to be only linked to adsorbed polymers and can therefore be attributed either to electrostatic or steric repulsion mechanisms. On the other hand, superplasticizer requirement increases with silica fume fraction in particular with the less ionic polymer. This indicates important electrostatic interactions with the surface in the process of adsorption.
10.14359/6015
SP178-48
L. Gatty, S. Bonnamy, A. Feylessoufi, H. Van Damme and P. Richard
Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM) and Chemical Analysis investigations lead to a fine characterization of Reactive Powder Concretes elaborated under different conditions as pressure application during setting and post-set heat treatment. An abrasive thinning method followed by ionic etching allowed for the preparation of 100 nm thick specimens with wide observation surface areas while still avoiding any water or CO2 contact which may cause their alteration. Silica fume distribution and reactivity versus curing processes are studied. The Si diffusion interfacial zone between hydrated products and silica time, clinker particles or crushed quartz is measured in different curing cases. The Ca/Si ratio spatial distribution in hydrated products and its evolution with the curing processes are then analysed and shown to be strongly microheterogeneous.
10.14359/6016
SP178-49
A.C. Courault, A.K. Crumbie, D. Sorrentino and D. Damidot
Concrete samples made with and without blast furnace slag (BFS) and stored in saturated gypsum solutions for 40 years have been studied. After this long period of time, there still remains small amounts of anhydrous cement and unreacted BFS grains. The reacted BFS are easily identified by EPMA analyses by considering the Mg concentration ; Mg does not diffuse away from the BFS grains. On the contrary Al diffuses away from the BFS grains towards the paste, whereas Ca tends to diffuse from the paste towards the BFS grains. The evolution of Ca, Al, Si and Mg concentrations from slag grains to the paste, or to cement grains, can be described by a succession of local equilibria defined in the CaO-Si02 -A12 03 -MgO-S03 -H2 0 system. The formation of different phase assemblages in the presence of BFS may account for the finer pore structure found despite similar total porosities for both concretes. Moreover a calcite layer has been formed : this layer limits sulfate ions ingress into the paste for both concretes.
10.14359/6017
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