abstract: The alkali activation of aluminosilicate materials as binder systems derived from industrial byproducts have been extensively studied due to the advantages they offer in terms enhanced material properties, while increasing sustainability by the reuse of industrial waste and byproducts and reducing the adverse impacts of OPC production. Fly ash and ground granulated blast furnace slag are commonly used for their content of soluble silica and aluminate species that can undergo dissolution, polymerization with the alkali, condensation on particle surfaces and solidification. The following topics are the focus of this thesis: (i) the use of microwave assisted thermal processing, in addition to heat-curing as a means of alkali activation and (ii) the relative effects of alkali cations (K or Na) in the activator (powder activators) on the mechanical properties and chemical structure of these systems. Unsuitable curing conditions instigate carbonation, which in turn lowers the pH of the system causing significant reductions in the rate of fly ash activation and mechanical strength development. This study explores the effects of sealing the samples during the curing process, which effectively traps the free water in the system, and allows for increased aluminosilicate activation. The use of microwave-curing in lieu of thermal-curing is also studied in order to reduce energy consumption and for its ability to provide fast volumetric heating. Potassium-based powder activators dry blended into the slag binder system is shown to be effective in obtaining very high compressive strengths under moist curing conditions (greater than 70 MPa), whereas sodium-based powder activation is much weaker (around 25 MPa). Compressive strength decreases when fly ash is introduced into the system. Isothermal calorimetry is used to evaluate the early hydration process, and to understand the reaction kinetics of the alkali powder activated systems. A qualitative evidence of the alkali-hydroxide concentration of the paste pore solution through the use of electrical conductivity measurements is also presented, with the results indicating the ion concentration of alkali is more prevalent in the pore solution of potassium-based systems. The use of advanced spectroscopic and thermal analysis techniques to distinguish the influence of studied parameters is also discussed. / Dissertation/Thesis / M.S. Engineering 2013

Microwave curing has become a trend in composite processing due to its efficiency in energy consumption compared to the traditional curing method. However, as commonly found in every composite processing, controlling the microwave curing process remains challenging. The most feasible control method is to build a numerical model. In this report, the numerical model was developed to simulate the microwave heating of cured and uncured glass/epoxy samples. The objective of cured sample simulation was to obtain the average electric field intensity generated in the composite, which was then used in the uncured sample simulation. Meanwhile, three methods of microwave heating to the uncured samples were suggested, i.e. heating with constant electric field intensity, heating with non-constant electric field intensity, and heating with concentrated electric field intensity. The simulation was further expanded by combining microwave heating with contact heating to improve the curing state on the corner section. The simulation showed a reasonable temperature evolution trend for all three microwave-heated methods of an uncured sample. However, they are all different from the experiment result. Meanwhile, a high temperature in the core layer was observed in all simulations with a gradual temperature decline toward the outer layer, as expected from a microwave heated object. Finally, a decent degree of cure was obtained by employing additional contact heating without involving microwaves. / Mikrovågsbaserad härdning har blivit en trend inom komposittillverkning på grund av dess energieffektivitet jämfört med den traditionella härdningsmetoden. Men precis som i all komposittillverkning är det fortfarande utmanande att kontrollera mikrovågshärdningsprocessen. Den mest genomförbara kontrollmetoden är att bygga en numerisk modell. I den här rapporten utvecklades en numerisk modell för att simulera mikrovågvärmning av härdat och ohärdat glas/epoxiprover. Målet med simuleringen av de härdade proven var att få fram den genomsnittliga intensiteten av det elektriska fältet som genereras i kompositen, vilket sedan användes i simuleringen av de ohärdade proven. Samtidigt föreslogs tre metoder för mikrovågshärdning av de ohärdade proven, nämligen uppvärmning med konstant intensitet av det elektriska fältet, uppvärmning med varierande intensitet av det elektriska fältet och uppvärmning med koncentrerad intensitet av det elektriska fältet. Simuleringen utökades sedan genom att kombinera mikrovågshärdning med kontaktuppvärmning för att förbättra härdningsgraden i hörnsektionen. Simuleringen visade en rimlig temperaturutveckling för alla tre metoder för mikrovågsuppvärmda ohärdade prov. Dock skiljer de sig alla från experimentresultatet. Samtidigt observerades en hög temperatur i kärnskiktet i alla simuleringar med gradvis temperatursänkning mot ytterlagret, vilket förväntas hos ett mikrovågsuppvärmt objekt. Slutligen uppnåddes en acceptabel härdningsgrad genom mot sluret addera kontaktuppvärmning utan mikrovågor.