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Sustainable materialisation of residues from thermal processes into construction materials : construction materials from stainless steel slags
Authors: ---
ISBN: 9789460188602 Year: 2014 Publisher: Leuven Katholieke Universiteit Leuven

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The amount of slag generated is almost athird of the total stainless steel produced. Owing to its mineralogy, a large partof the slag is produced as fines, which has a very low valorisation potentialand has to be landfilled. The present work is aimed at exploring the potentialof these slags to produce construction materials of higher economic value.To address the issue, two valorisationroutes were applied: 1) alkali-activation initiating binding reactions in theslag by the addition of alkali hydroxides and silicates, 2) carbonation initiating hardening reaction in the slag by the formation of alkalicarbonates. Two stainless steel slags, continuous casting (CtCs) slag and Argonoxygen decarburisation (AOD) slag, were targeted for valorisation.Initiation of hardening reactions in theslag was found to occur only under a combined treatment of alkali (Na and K)hydroxides and high temperature (80 °C) which was provided by steam curing. However,only a moderate strength in the mortar specimens was observed under suchconditions along with appearance of efflorescence with NaOH for molaritiesabove 5 M. The problem of low strength and efflorescence in the mortar sampleswas eliminated by the introduction of silicates in the system along with thealkali hydroxides. The compressive strength of the slag mortars was found toincrease with the increase in the amount of silicates in the activatingsolution and with the increase of the curing temperature. The reaction productfrom the activation was found to be C-S-H as confirmed by thermogravimetric,QXRD, FTIR and 29Si NMR analysis.The slag was also found to develop strengthunder acceleration carbonation conditions which was provided under two environments:i) in a carbonation chamber, maintained at atmospheric pressure, 22 °C, 5 vol.%CO2 and 80% RH; and ii) in a carbonation reactor, where the CO2partial pressure (pCO2)and temperature could be further increased. It was found that in thecarbonation chamber the compressive strength of the samples and the CO2sequestration continued to increase up to 3 weeks whereas in the reactor theoptimum for strength and CO2 sequestration was found at 80 °C, 8 barpressure in 2.5 h. The major reaction product was found to be calcite indifferent morphologies.Three types of masonry blocks were preparedform the slag with the two valorisation routes: alkali-activated solid bricks,perforated carbonated bricks and alkali-activated aerated bricks. Thecarbonated bricks were found to have the best resistance to freeze-thaw,whereas the aerated bricks were found to have superior thermal resistivity values.The LCA showed that the environmental impact of the bricks is lower (negativefor carbonated bricks) than the conventional clay fired bricks and the impactof the aerated bricks was found to be similar to the conventional aeratedblocks available in the market. A SWOTanalysis highlighted the advantage of using these bricks in the form of lowerenergy requirement in its production, reduction of stress on the use of prime materialsand ease of metal recovery from the residual slag.The results of the dissertation show that thebinding potential of the stainless steel slags can be exploited as valorisedapplications in the construction industry by novel thermo-alkali activation andcarbonation processes.


Multi
Interactions between cement and combined concrete admixtures : the influence on cement paste rheology
Authors: ---
ISBN: 9789460188589 Year: 2014 Publisher: Leuven Katholieke Universiteit Leuven

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During the last decades, innovative concrete applications have been the result of technological developments as new processing techniques, the use of concrete admixtures and advanced materials. All these improvements increase the demand for better performing concrete with enhanced workability. However, the lack of reliable engineering tools in traditional concrete production methods has led to some inconsistent control of the workability. Therefore, todays research is increasingly investigating advanced models that capture the flow behavior of fresh concrete as accurately as possible. These models are continuously improving but generally keep facing problems which are linked to the agglomeration of the cement particles and to the implementation of combined concrete admixtures. The objective of this work is to investigate the rheological mechanism in cement paste for the combined use of superplasticizer, retarder and accelerator. In particular, an effect on the particle agglomeration is aimed for in order to contribute to a more fundamental understanding of the concretes flow behavior. Concerning the superplasticizer impact on cement paste, thermodynamic modelling and mineralogy studies led to the conclusion that the superplasticizer can change the hydrate morphology to such an extent that the interparticle contact forces are modified. The extra addition of retarder led to a densified polymer layer at the cement grain surface which contributed to the steric stabilization of the cement paste. An additional electrostatic effect and the induced changes in hydrate morphology are also demonstrated to contribute to the low paste viscosity. With the extra addition of a calcium salt accelerator to the cement paste, an interstitial structure was assumed to diminish the rheological effect of the polymer layer.All the developed conceptual mechanisms were implemented in a coherent agglomeration model, based on measurable parameters. In this model, the internal and external hydrates in a cement agglomerate were defined and quantified. Generally, the cumulative amount of hydrates within the agglomerates influenced the agglomerate stability and the amount of external hydrates determined the reagglomeration rate. For the superplasticizer only, a proportional relation was found between the change in agglomeration rate and the external agglomerate connectivity while, for the extra addition of retarder and accelerator, a reverse relation was found. The latter was attributed to a mechanical contribution of the interstitial volume. On the one hand, the retarder creates a source of slowly hydrating nuclei and particles in that volume and, on the other hand, these particles are expected to coagulate due to the accelerator addition. In the second case, the interstitial volume also delivered a contribution to the stress resistance of the cement paste at rest.This fundamental research combines dedicated analytical methods and conceptual models to improve the understanding of particle agglomeration and contributes to a more extensive insight into the concrete rheology.


Multi
Auteursrecht en informatietechnologie: over de beperkte houdbaarheid van technologiespecifieke regelgeving
Author:
ISBN: 9075727739 Year: 1998 Publisher: Amsterdam Cramwinckel

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Optimization and integration of geo-electrical techniques as a non-destructive assessment for masonry structures
Authors: ---
ISBN: 9789056829568 Year: 2008 Publisher: Leuven Katholieke Universiteit Leuven

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De geo-elektrische technieken uit de geofysica werden aangepast voor gebruik als een niet-destructieve techniek voor het in situ onderzoek van historisch metselwerk. Theoretische beschouwingen en numerieke modellering hebben aangeduid hoe ze omgebouwd konden worden om op metselwerk gebruikt te worden. Daarna werden ze verder ontwikkeld en getest in het laboratorium, en uiteindelijk toegepast op historisch metselwerk on site in twee restauratieprojecten. In deze thesis werd duidelijk aangetoond dat het geo-elektrisch onderzoek van metselwerk een geschikt, niet-destructief middel aan het worden is voor de diagnose van een beschadigde structuur, om de nood aan restauratie te beoordelen en om de efficiëntie van consolidatieinjecties te controleren. The geo-electrical techniques from geophysics have been adapted from for use as a non-destructive technique on historic masonry. Theoretical considerations and numerical modelling have shown how they could be reconsidered for use on masonry. They have been further developed and tested in laboratory, and finally applied on historic masonry in two case studies. This thesis shows that geo-electrical surveying is a cost-efficient, quick, accurate, non-destructive technique for the evaluation of the inner structure of building constructions in general, and masonry walls in particular. The geo-electrical survey of masonry is becoming a suitable, non-destructive tool for the diagnosis of a deteriorated structure, to judge the need of restoration and to control the efficacy of consolidation injections.


Multi
Biogeography of Madagascan Rubiaceae : case studies from the Afro-Madagascan genus Tricalysia and the pantropical genus Ixora
Authors: ---
ISBN: 9789086492688 Year: 2009 Publisher: Leuven Katholieke Universiteit Leuven. Faculteit Wetenschappen


Multi
State dependent effects in labour and foreign exchange markets
Author:
ISBN: 8275531926 Year: 2002 Publisher: Oslo Norges Bank

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Keywords

Money. Monetary policy --- International finance --- Labour economics --- 331.5 <481> --- 339.743 --- Foreign exchange --- -Petroleum --- -Unemployment --- -336.74 --- 339.7 --- 331 --- NO / Norway - Noorwegen - Norvège --- 332.620 --- 332.691 --- 333.450 --- Petroleum --- -Foreign exchange --- -330.05 --- 331.1379481 --- Cambistry --- Currency exchange --- Exchange, Foreign --- Foreign currency --- Foreign exchange problem --- Foreign money --- Forex --- FX (Finance) --- International exchange --- Currency crises --- Joblessness --- Employment (Economic theory) --- Full employment policies --- Labor supply --- Manpower policy --- Right to labor --- Underemployment --- Coal-oil --- Crude oil --- Oil --- Caustobioliths --- Mineral oils --- Arbeidsmarkt. Werkgelegenheid --(algemeen)--Noorwegen --- Wisselkoersen. Wisselkoerspariteiten. Dubbele wisselkoers. Devaluatie. Revaluatie. Zwevende wisselkoers. Muntslang --- Econometric models --- Prices --- -Econometric models --- Geld. Monetaire politiek --- Internationale financiën --- Arbeidseconomie --- Werkloosheid: algemeenheden. Philipscurve. --- Evolutie van de arbeidsmarkt. --- Theorie van het deviezenverkeer. Theorie van de koopkrachtpariteit. --- Theses --- 339.743 Wisselkoersen. Wisselkoerspariteiten. Dubbele wisselkoers. Devaluatie. Revaluatie. Zwevende wisselkoers. Muntslang --- 331.5 <481> Arbeidsmarkt. Werkgelegenheid --(algemeen)--Noorwegen --- Petroleum products --- Unemployment --- 330.05 --- 336.74 --- Mazut --- Hydraulic fluids --- Prices&delete& --- Werkloosheid: algemeenheden. Philipscurve --- Evolutie van de arbeidsmarkt --- Theorie van het deviezenverkeer. Theorie van de koopkrachtpariteit --- Refining

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