Reutilización de residuos vítreos urbanos industriales en la fabricación de cementos alcalinos: Activación, comportamiento y durabilidad
Author
Torres Carrasco, ManuelAdvisor
Puertas Maroto, FranciscaEntity
UAM. Departamento de Química Inorgánica; CSIC. Instituto de Ciencias de la Construcción Eduardo Torroja (IETcc)Date
2015-10-23Funded by
La realización del presente trabajo ha sido posible gracias al apoyo económico prestado a través del proyecto BIA2010-15516 y a la concesión de una beca de Formación de Personal Investigador (FPI, BES- 2011-043554) del Ministerio de Economía y CompetitividadSubjects
Cemento - Fabricación - Tesis doctorales; Residuos urbanos - Aprovechamiento - Tesis doctorales; Vidrio - Residuos - Reciclado - Tesis doctorales; QuímicaNote
Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Faculta de Ciencias, Departamento de Química Inorgánica. Fecha de lectura: 23-10-2015Esta obra está bajo una licencia de Creative Commons Reconocimiento-NoComercial-SinObraDerivada 4.0 Internacional.
Abstract
This study was conducted against the backdrop of the need for alternative
binders, i.e., other than Portland cement, made from industrial by-products
such as alkali-activated blast furnace slag or fly ash. The mortars and concretes
made from such binders are less environmentally harmful and entail lower
energy demands than the respective Portland-based products, while exhibiting
higher mechanical strength and durability.
Solutions containing NaOH, Na2CO3 or sodium silicate hydrates (waterglass)
are the alkalis most commonly used for these purposes. Of the three, sodium
silicate hydrate generates alternative systems with the highest mechanical
strength and durability. Waterglass manufacture, however, is CO2 emissionintensive
and calls for high fusion temperatures. The question that should be
posed, then, is whether recent research on alternative binders has delivered
truly eco-efficient materials globally considered, or whether further study is
required to develop activators other than the ones conventionally used with a
view to minimising the environmental impact of the manufacture of sodium
silicates.
The ultimate aim of the research conducted on the occasion of this PhD. thesis
was to find a way to improve the economic and environmental balance of
alkaline cements by partially or wholly replacing traditional alkaline activators
such as waterglass with urban and industrial waste glass. As an amorphous
material with a chemical composition consisting essentially of SiO2 and Na2O,
such waste may potentially form part of the waterglass family of alkaline
activators.
This primary aim was pursued through a series of partial objectives which
sought to determine the conditions in which blast furnace slag and fly ash
would be most effectively activated with the alternative waste glass solution.
The first such objective was to ascertain waste glass solubility in highly
alkaline media. That information was then used to establish the optimal
conditions for dissolving SiO2 out of the glass and the resulting solution was
applied to activate blast furnace slag and fly ash. The conditions defined were:
mixed glass; particle size, <45 microns; solvent, for blast furnace slag, 50/50
molar NaOH/Na2CO3 solution (5 % NaO2 by slag mass) and for fly ash 10-M
NaOH solution; magnetic stirring time, 6 hours; temperature, 80 ± 2 °C. These
results were corroborated by statistical analysis. The aforementioned optimal
conditions for waste glass solubility were applied to determine the feasibility of
using such solutions as activators in the preparation of alternative pastes,
mortars and concretes. In the study of the performance of these materials, their
mechanical strength was found to be similar to the strength of materials
activated with a commercial sodium silicate. Furthermore, characterisation of
the main hydration products, C-A-S-H gel in the blast furnace slag system and
N-A-S-H gel in fly ash, showed that the gels forming in the systems activated
with the alternative solution were very similar to the ones present in the
sodium silicate hydrate-activated materials.
Lastly, durability studies based on exposure to aggressive media such as
chlorides, carbonation and freeze-thaw showed that alkali-activated slag
concretes performed as well as or better than conventional Portland cement
concrete. The concretes activated with waste glass solutions delivered results
comparable to those for conventionally activated materials, and proved to be
even more resistant to freeze-thaw stress
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