More sustainable and efficient degumming methods are required to extract finner bast fibres, especially from agro-industrial waste streams such as stalks from hemp for food purposes. For this reason, in this study, two urea-based treatments were evaluated as degumming alternatives for unretted hemp fibres from residual streams, one at cold and alkaline conditions (CUA) and the other in combination with microwave radiation (MWU). Both approaches reduced fiber bundles diameter, decreasing 61% at -7°C 5 minutes, 12%Urea-5%NaOH, and 44% for microwave-30%urea for 30 minutes. Although both methods resulted in considerable fibre bundle diameter reduction, they resulted in a lower reduction than the 74% obtained for a traditional alkali (TA) degumming. Shorter fibres were obtained after the treatments. CUA and TA treatments obtained similar fibre lengths, while MWU resulted in longer than the other treatments. The chemical and thermal analysis showed that the highest removal of no cellulosic components was achieved by the TA treatment, followed by CUA and MWU. The treatments were applied to nonwovens produced by needle punching, showing no significant differences in tenacity and flexural rigidity compared to non-treated nonwovens. An increase of mass per unit area was identified for the CUA-treated fabrics, attributed to crimp generated in the treatment. Both urea-based treatments showed potential as more sustainable alternatives for degumming unretted hemp fibre bundles extracted from agro-waste.

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Alkali activated materials are a promising generation of binders, which can be significantly recognized by having lower carbon footprint, being waste originated, and having unique chemistry and thermodynamics. It appears that alkali activated materials can be engineered to exhibit high-tech and intelligent performances with less effort compared to Portland cement-based binders, if appropriately formulated. In addition, alkali activated materials have several inherent properties such as adjustable microstructure and strength, and heat and chemical resistances. Based on these explanations, the focus of this doctoral thesis was on the fabrication and characterization of multifunctional and smart alkali activated nanocomposites. The investigated alkali activated system was composed of fly ash, ground granulated blast-furnace slag (GGBS), and sodium-based silicate and hydroxide. Carbon nanotubes (CNTs) were incorporated into the alkali activated matrix to constitute a functional complex nano system. Multi-walled carbon nanotubes (MWCNTs) were utilized for colloidal, mechanical and microstructural studies and single-walled carbon nanotubes (SWCNTs) applied for electrical, thermoelectric and sensing assessments. The colloidal and mechanical performances and microstructural characteristics have been assessed for the alkali activated nanocomposites, which were fabricated by a dispersion of MWCNTs (0.05 wt.%) into sodium-based silicate and hydroxide solutions and their combination. The highest MWCNTs’ dispersibility and in-solution stability and smallest dimension of agglomerations were observed in the sodium silicate dispersion media. Accordingly, the highest compressive and flexural strengths were accomplished for mentioned nanocomposites, ≈60 MPa & ≈10 MPa, respectively. The reason for the mechanical improvement was the effective reinforcement of MWCNTs when dispersed in sodium silicate. The MWCNTs were more functional in pore refinement and crack propagation control of the nanocomposites’ microstructure. Thermoelectric properties and thermoelectric power generation performances have been studied for the alkali activated nanocomposites and the resultant generator device. SWCNTs were used for the alkali activated thermoelectric generator fabrications. A single piece of nanocomposite with SWCNT content of 1 wt.% could achieve a Seebeck coefficient of ≈16 μV·K-1 and power factor of 0.4 μW·m-1·K-2. The thermoelectric generator device consisted of 10 serially interconnected alkali activated thermoelements (p-type elements). The highest generated thermoelectric voltage and power with inclusion of 1 wt.% of SWCNTs in the nanocomposites were ≈7 mV and ≈0.7 µW, respectively at ΔΤ of 60 K. In the last phase of this doctoral research the idea of ion discrimination and the potential of being a sensor have been conceptualized and demonstrated for SWCNT alkali activated nanocomposites. The alkali activated sensors were produced by incorporation of 0.1 wt.% of SWCNTs based on the results of conducted percolation study. The sensors displayed an ion discrimination potential by transmitting signals with a detectable difference in geometry and magnitude in exposure to the introduced analytes. The discrimination criteria were analytes’ type, concentration, and volumetric quantity. The SWCNT alkali activated sensors showed a higher magnitude of relative resistance in exposure to the sulphuric acid compared to the magnesium sulphate. In addition, the obtained signals in sulphuric acid exposure had a curvature shape but the signals of magnesium sulphate were rectangular. The introduced sensors were applicable for the sulphuric acid concentration detection in a range of 0.001 to 0.1 M. The sensors did not have any upper threshold limit, however the lower threshold limit for sulphuric acid concentration detection was 0.001 M. There was a direct relation between the exposed quantity of sulphuric acid and relative resistance of the alkali activated sensors. The finding of this doctoral research can be utilized for development of alkali activated nanocomposites with industrial implementations. That may include nano reinforced structural elements, thermoelectric generators for green energy production and sensors for structural health monitoring of concrete infrastructures.:Chapter 1. Motivation and innovation 1 1.1. Introduction 1 1.2. Alkali activated materials and geopolymers 1 1.3. Mechanical properties 2 1.3.1. Challenge 2 1.3.2. Novelty 4 1.4. Thermoelectricity 5 1.4.1. Challenge 6 1.4.2. Novelty 6 1.5. Sensing concept 7 1.5.1. Challenge 8 1.5.2. Innovation 10 1.6. Aim 10 1.7. Strength and shortcoming 11 1.8. Structure 11 Chapter 2. Methodology 17 2.1. Materials 17 2.1.1. Carbon nanotubes 17 2.1.2. Surfactants 18 2.1.3. Precursors 19 2.1.4. Activators 20 2.1.5. Analytes 20 2.2. Methods 21 2.2.1. Two-part activation technology 21 2.2.1.1. MWCNTs and naphthalene sulphonate concentrations 21 2.2.1.2. Fabrication methodologies of nanofluids and nanocomposites 21 2.2.1.2.1. Na2Si3.5O9 based nanofluids and nanocomposites (strategy I) 22 2.2.1.2.2. NaOH based nanofluids and nanocomposites (strategy II) 22 2.2.1.2.3. Combined (Na2Si3.5O9+NaOH) nanofluids and nanocomposites (strategy III) 23 2.2.1.3. Dispersion of nanofluids 23 2.2.1.4. Mixing of nanocomposites 24 2.2.2. One-part activation technology 24 2.2.2.1. SWCNTs and SDBS concentrations 25 2.2.2.2. Fabrication methodology of nanofluids 25 2.2.2.2.1. Thermoelectricity 25 2.2.2.2.2. Sulphate sensing 25 2.2.2.2.3. Sulphuric acid sensing 25 2.2.2.3. Fabrication methodology of nanocomposites 26 2.2.2.3.1. Thermoelectricity 26 2.2.2.3.2. Sulphate sensing 26 2.2.2.3.3. Sulphuric acid sensing 26 2.3. Characterizations 27 2.3.1. Optical microscopy 27 2.3.2. Integral light transmission (ILT) 27 2.3.3. Scanning electron microscopy (SEM) 27 2.3.4. Transmission electron microscopy (TEM) 28 2.3.5. Fourier-transform infrared spectroscopy (FTIR) 28 2.3.5.1. Alkaline nanofluids 28 2.3.5.2. Chemiresistor nanocomposites 29 2.3.6. Mercury intrusion porosimetry (MIP) 29 2.3.7. Roughness measurements 29 2.3.8. pH measurements 29 2.3.9. Mechanical properties 29 2.3.10. Thermoelectric acquisitions 30 2.3.11. Thermoelectric generator acquisitions 31 2.3.12. Sensing and discriminating acquisitions 31 Chapter 3. Dispersion of CNTs 33 3.1. Introduction 33 3.2. MWCNTs dispersibility 33 3.3. MWCNTs dispersion stability 36 3.4. MWCNTs and naphthalene sulphonate interactions 38 3.5. Potential physisorption 42 3.6. Conclusion 44 3.7. Perspective 44 Chapter 4. Microstructure refinement 45 4.1. Introduction 45 4.2. Mechanical reinforcement 45 4.3. Reinforcement mechanism 49 4.3.1. Morphology 49 4.3.2. Porosity 55 4.4. Conclusion 60 4.5. Perspective 61 Chapter 5. Thermoelectricity 63 5.1. Introduction 63 5.2. Thermoelectric properties 63 5.3. Thermoelectric generator 65 5.3.1. Power output 65 5.3.2. Stability performance 69 5.4. Mechanical properties 70 5.5. Multifunctional behaviour 71 5.6. Conclusion 73 5.7. Perspective 74 Chapter 6. Sulphate discrimination 77 6.1. Introduction 77 6.2. Percolation threshold 77 6.3. Sulphate discrimination 80 6.4. Concentration differentiation 84 6.5. Quantity differentiation 86 6.6. Conclusion 88 6.7. Perspective 89 Chapter 7. Sulphuric acid sensing 91 7.1. Introduction 91 7.2. Electrical properties 91 7.3. Morphology of the SWCNTs’ conductive network 92 7.4. Sensing properties 96 7.4.1. Exposure to ultrapure water 96 7.4.2. Exposure to sulphuric acid 97 7.4.2.1. pH influence 100 7.4.2.2. Surface composition change 103 7.4.3. Sensor sensitivity 106 7.5. Microstructure dependency 109 7.5.1. SWCNTs and matrix interactions 109 7.5.2. Matrix porosity 113 7.5.3. Matrix roughness 115 7.6. Conclusion 118 7.7. Perspective 119 Summary 121 References 123 Publications from this doctoral research 151

Biomass represents an important sustainable energy resource, with biomass-coal cofiring representing among the most effective and cost efficient CO2 reduction strategies. Fly ash generated during coal combustion represents a technically advantageous, inexpensive, and environmentally beneficial admixture in concrete production, partially replacing cement. However, strict interpretation of American Society of Testing and Materials (ASTM) and American Concrete Institute (ACI) standards prohibits use of fly ashes from any source other than coal in concrete production; therefore, fly ash from biomass coal cofiring is excluded from use in concrete. This dissertation discusses biomass impacts on concrete properties through experiments conducted on several combinations of blended and pure biomass fly ash in concrete mixtures to determine the effects on freshly mixed concrete, strength and durability of hardened concrete, and implication for long-term material properties. The results show that the performance of biomass and blended biomass-coal fly ash is comparable to that of traditional (neat) coal fly ash. Pozzolanic reactions occur simultaneously but not necessarily proportionally to strength development. Mixtures of biomass and coal fly ash in all proportions mitigate alkali-silica-reaction-based (ASR-based) expansion in concrete. Biomass-specific results indicate that biomass-containing fly ash samples can generate 3-6 times the strength of some neat coal fly ash samples in terms of pozzolanic reactions and that biomass-containing fly ash samples have better or comparable ASR mitigation performance relative to neat coal fly ash. Biomass fly ash applications in concrete production involve pozzolanic, cementitious, and ASR reactions in combination with mixture compositions and preparation techniques to dictate ultimate properties. In these practical applications, biomass fly ash demonstrates no consistent improvement or deprecation of concrete properties relative to coal fly ash. Quantitative pozzolanic reaction mechanism and kinetic analyses indicate biomass and coal fly ashes exhibit comparable reaction rates and react by similar mechanisms. The general conclusion from the experiments is that biomass-containing fly ash, when used in concrete, performs comparable to or better than similar neat coal fly ash preparations in most respects; Substantial efforts were made to ensure samples represent typical commercial samples. Therefore, there exists no reason to exclude biomass from cofiring applications on the basis of fly ash performance in concrete and the related standards should be revised.

Pressure is mounting in the concrete industry to adopt eco-efficient methods to reduce CO₂ emissions. Portland cement (PC), an essential concrete ingredient, is responsible for over two-thirds of the embodied energy of the concrete, generating about 8% of global greenhouse gas emissions. Extraction and transportation of aggregates and raw materials that comprise concrete mixes are also directly linked to their embodied energy; thus, recycled concrete aggregates (RCA) have been proposed as a promising alternative to increase sustainability in new construction. In this context, many studies have been conducted over the past decades on the properties of RCA concrete. Recent studies have shown that suitable fresh (i.e., flowability) and short-term hardened (i.e., compressive strength) properties might be achieved when the unique microstructural features of RCA are accounted for in the mix-design process of the recycled concrete. However, manufacturing RCA from construction demolition waste (CDW) or returned concrete (RC) presents its unique challenges. Amongst others, the variation in the source of RCA and the presence of damage due to several deterioration mechanisms causes major concern. Due to the presence of reactive aggregates in many quarries in Canada, alkali-silica reaction (ASR) is one of the most common deterioration mechanisms. The durability and long-term performance of RCA concrete are not fully understood and should be further investigated, especially in regards to a) the potential of further (secondary) deterioration of recycled concrete bearing coarse and fine alkali-silica reactive aggregates b) the impact of the severity of the initial reaction on mechanical properties and kinetics of expansion in recycled concrete and c) the impact of using sound and alkali-silica reaction (ASR) affected RCA on the chloride diffusivity (and thus corrosion initiation) of concrete. This work aims to appraise the durability performance of RCA concrete made of 100% coarse RCA, particularly two families of RCA selected (i.e., returned concrete RCA, demolished concrete RCA) to represent waste currently being generated. Furthermore, two types of reactive aggregates are selected to investigate the impact of the source of the reaction (i.e. reactive coarse aggregate as original virgin aggregate - OVA and reactive sand within the residual mortar - RM) within the RCA. ASR is the distress mechanism used to introduce damage to the manufactured RCA. A new mix design technique was used to produce recycled concrete mixtures to increase eco-efficiency, improve fresh-state properties, and reduce cement use in RCA concrete. In conclusion, the initial reaction's location and severity significantly impact the compressive strength, SDT parameters, chloride diffusion rate, and shear strength of concrete specimens. Specifically, the location of the initial reaction can influence the distribution and extension of damage within the various parts of recycled concrete, while the severity of the initial reaction can affect the overall integrity of the aggregates as well as the availability of silica and alkalis for secondary reaction. These results demonstrate the importance of assessing the severity of the initial reaction and its source in order to ensure the durability and long-term performance of recycled concrete made with reactive RCA.

The current trend concerning the thinning of solar cell devices is mainly motivated by economic aspects, such as the cost of the used rare-earth elements, and by the requirements of emergent technologies. The introduction of ultra-thin absorber layers results in a reduction of used materials and thus contributes to a more cost-effective and time-efficient production process.However, the use of absorber layers with thicknesses below 500nm gives rise to multiple apprehensions, including concerns regarding light management and the absorber’s quality.Therefore, this experimental work presents a novel solar cell architecture that aims to tackle the issues of optical and electrical losses associated with ultra-thin absorber layers. To that end, a Hafnium Oxide (H f O2) rear side passivation layer was introduced in-between the copper indium gallium (di)selenide Cu(In, Ga)Se2, CIGS-based absorber layer and the Molybdenum (Mo) back contact. Then, the proposed Potassium Fluoride (KF) alkali treatment successfully established point contacts on the ALD-deposited oxide layer, resulting in a passivation effect with minimum current blockage.The established cell architecture showed significant improvements regarding both open circuit voltage (Open-Circuit Voltage (Voc)) and efficiency when compared to unpassivated reference devices. The used solar cell simulator (SCAPS) attributes the observed improvements to a reduced minority carrier recombination velocity at the rear side of the device. Moreover, the provided photoluminescence (PL) results report a higher peak intensity and lifetime for passivated devices.Furthermore, the overlay of the given external quantum efficiency (EQE) spectra with the performed simulations show that the HfO2 passivation layer improves the optical reflection from the rear contact over a wavelength interval ranging from 500 to 1100 nm, resulting in a short circuit current (Jsc) improvement. An increased quantum efficiency observed throughout almost the entire measurement range, confirms that the enhance in Jsc is also due to electronic effects.Here, a produced solar cell device including a 3nm-thick HfO2 rear passivation layer and a 500nm-thick 3-stage CIGS absorber, achieved a conversion efficiency of 9.8%.Further, the approach of combining an innovative rear surface passivation layer with a fluoride-based alkali treatment resulted in the development and successful characterisation of a 1-stage, 8.6% efficient solar cell. Such result, mainly due to a short circuit current (Jsc) enhancement, supports the introduction of more straightforward production steps, which allows a more cost-effective and time-efficient production process. The produced device consisted of a 500nm-thick CIGS absorber, rear passivated with an ultra-thin (2nm) HfO2 layer combined with a 0.6M KF treatment. / Den nuvarande trenden när det gäller solcellsanordningar huvudsakligen motiveras av ekonomiska aspekter, såsom kostnaden för att använda sällsynta jordartsmetaller, och av kraven i ny teknik. Införandet av ultratunna absorptionsskikt resulterar i en minskning av använda material och bidrar därmed till en mer kostnadseffektiv och tidseffektiv produktionsprocess.Användningen av absorptionsskikt med tjocklekar under 500 nm ger emellertid upphov till flera bekymmer, beträffande ljushantering och absorptorkvalitet.Därför presenterar detta experimentella arbete en ny solcellarkitektur som syftar till att ta itu med frågorna om optiska och elektriska förluster förknippade med ultratunna absorberlager. För detta ändamål infördes ett Hafnium Oxide (H f O2) bakre sidopassiveringsskikt mellan kopparindiumgallium (di) selenid Cu(In, Ga)Se2, CIGSbaserat absorberande skikt och Molybdenum (Mo) kontakt. Sedan upprättade den föreslagna kaliumfluorid (KF) alkali-behandlingen framgångsrikt punktkontakter på det ALD-avsatta oxidskiktet, vilket resulterade i en passiveringseffekt med minimal strömblockering.Den etablerade cellarkitektur visade signifikanta förbättringar avseende både öppna kretsspänningen (Voc) och effektivitet i jämförelse med opassiverad referensanordningar. Den använda solcellsimulatorn (SCAPS) tillskriver de observerade förbättringarna till en minskad minoritetsbärares rekombinationshastighet på enhetens baksida. Dessutom de tillhandahålls fotoluminescens (PL) resultat rapporterar en högre toppintensitet och livslängd för passive enheter.Dessutom visar överläggningen av det givna externa kvantitetseffektivitetsspektrumet (EQE) med de utförda simuleringarna att passiveringsskiktet HfO2 förbättrar den optiska reflektionen från den bakre kontakten över ett våglängdsintervall från 500 till 1100 nm, vilket resulterar i i en kortslutningsström (Jsc) förbättring. En ökad kvantverkningsgrad observerats i nästan hela mätområdet, bekräftar att öka i Jsc är också på grund av elektroniska effekter.Här, en producerad solcellsanordning innefattande en 3 nm-tjock HfO2 bakre passiveringsskikt och ett 500 nm-tjock 3-stegs CIGS absorber, uppnått en omvandlingseffektivitet på 9.8%.Vidare resulterade tillvägagångssättet att kombinera ett innovativt bakre ytpassiveringsskikt med en fluoridbaserad alkalibehandling i utvecklingen och framgångsrik karaktärisering av en 1-stegs, 8.6% effektivitet solcell. Ett sådant resultat, främst på grund av en kortslutningsström (Jsc) förbättring, stöder införandet av mer enkla produktionssteg, vilket möjliggör en mer kostnadseffektiv och tidseffektiv produktionsprocess. Den framställda anordningen bestod av ett 500 nm-tjock CIGS absorber, bakre passiverad med en ultra-tunn (2 nm) HfO2-skikt kombineras med en 0.6M KF behandling.

yes / Test results of thirty six ground granulated blast-furnace slag (GGBS)-based mortars and eighteen fly ash (FA)-based mortars activated by sodium silicate and/or sodium hydroxide powders are presented. The main variables investigated were the mixing ratio of sodium oxide (Na2O) of the activators to source materials, water-to-binder ratio, and fine aggregate-to-binder ratio. Test results showed that GGBS based alkali-activated (AA) mortars exhibited much higher compressive strength but slightly less flow than FA based AA mortars for the same mixing condition. Feed-forward neural networks and simplified equations developed from nonlinear multiple regression analysis were proposed to evaluate the initial flow and 28-day compressive strength of AA mortars. The training and testing of neural networks, and calibration of the simplified equations were achieved using a comprehensive database of 82 test results of mortars activated by sodium silicate and sodium hydroxide powders. Compressive strength development of GGBS-based alkali-activated mortars was also estimated using the formula specified in ACI 209 calibrated against the collected database. Predictions obtained from the trained neural network or developed simplified equations were in good agreement with test results, though early strength of GGBS-based alkali-activated mortars was slightly overestimated by the proposed simplified equations.

Yes / In this study, the main emphasis is placed on the development and characterization of alkali-activated binders completely produced by the use of mixed construction and demolition waste (CDW)-based masonry units as aluminosilicate precursors. Combined usage of precursors was aimed to better simulate the real-life cases since in the incident of construction and demolition, these wastes are anticipated to be generated collectively. As different masonry units, red clay brick (RCB), hollow brick (HB) and roof tile (RT) were used in binary combinations by 75-25%, 50-50% and 25-75% of the total weight of the binder. Mixtures were produced with different curing temperature/periods and molarities of NaOH solution as the alkaline activator. Characterization was made by the compressive strength measurements supported by microstructural investigations which included the analyses of X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX). Results clearly showed that completely CDW-based masonry units can be effectively used collectively in producing alkali-activated binders having up to 80 MPa compressive strength provided that the mixture design parameters are optimized. Among different precursors utilized, HB seems to contribute more to the compressive strength. Irrespective of their composition, main reaction products of alkali-activated binders from CDW-based masonry units are sodium aluminosilicate hydrate (N-A-S-H) gels containing different zeolitic polytypes with structure ranging from amorphous to polycrystalline.

Waste-fired boilers suffer severely from corrosion of critical components such as superheater tubes. In this work the high temperature corrosion of candidate superheater alloys have been investigated by detailed laboratory studies and controlled field exposures in full-scale boilers. In a laboratory study the detrimental effect of gaseous hydrochloric acid (HCl) on three  different ground surface and preoxidised austenitic stainless steels was investigated. Exposures were conducted in an environment comprising N2-10O2-5H2O-0.05HCl at both 400 °C and 700 °C. A positive effect of preoxidation is evident when the alloys are exposed at 400 °C. Oxide layers formed during preoxidation effectively suppress chlorine ingress and lower the corrosion rate for all three materials while accelerated corrosion and chlorine accumulation at the metal/oxide interface is detected for ground surface specimens. The positive effect of preoxidation is lost at 700 °C and corrosion resistance is dependent on alloying level. At 700 °C metal chloride evaporation contributes significantly to the material degradation. Based on the results, high temperature corrosion in the presence of gaseous HCl is discussed in general terms.  In two different waste-fired boilers measures for counteracting superheater corrosion were investigated. In a grate-boiler the deposit formation and high temperature corrosion of some candidate superheater materials were studied. Metal loss measurements showed unacceptably high corrosion rates for the lower alloyed ferritic steels 13CrMo44 (Fe-1Cr-0.5Mo) and HCM12A (Fe-11Cr-2W), as well as for the austenitic Super 304 (Fe-18Cr-9Ni-3Cu). The corrosion attack for these alloys was manifested by the formation of mixed metal chloride/metal oxide scales. A different type of behaviour was seen for the higher alloyed austenitic steels and nickel-base alloys, which were able to form a chromium-enriched oxide next to the metal. However, the alloys suffered from localised pitting attack. Since analyses of the deposit revealed appreciable amounts of low melting salt mixtures such as ZnCl2-KCl, PbCl2-KCl, FeCl2-KCl and NaCl-NiCl2, oxide dissolution in these molten salts is the probable reason for pitting attack. In a waste-fired boiler ammonium sulphate solution was added to the flue gas and the effect on flue gas and deposit composition was evaluated. It was evident that the sulphur-rich additive reduced the amount of alkali chlorides in both the flue gas and the deposit. Results also indicated that the initial corrosion rates were lowered with the use of ammonium sulphate. It was concluded that using the additive could be a possible strategy for changing the flue gas chemistry so that superheater corrosion is mitigated. / <p>QC 20110414</p>

With the rapid development of concrete 3D printing for construction projects, it is crucial to produce sustainable 3D-printed cementitious composites that meet the required fresh and hardened properties. This study investigates the application of cellulose-based nanomaterials (CN) (i.e., abundant natural polymers) that can improve the mechanical properties of cement-based materials – in 3D-printed cementitious composites of ordinary portland cement (OPC) and alkali-activated materials (AAMs). A combination of low calcium fly ash and ground granulated blast-furnace slag was used as the precursor in AAM systems. This work examines the 3D-printed mixtures with varying binders and mixture proportions and with different dosages of cellulose-based nanomaterial known as cellulose nanocrystals (CNC) to optimize the formulation for the production of sustainable high-performance 3D-printed elements. A suite of experimental techniques was applied to study the impact of CNC on the fresh and hardened properties of the 3D-printed samples. The buildability of the alkali-activated mixtures was improved by increasing the CNC content, suggesting that the CNC performs as a viscosity-modifying agent in AAMs. The inclusion of CNCs up to 1.00% (by volume of the binder) improves the overall mechanical performance and reduces the porosity of 3D-printed OPC and heat-cured AAM samples. Further, the addition of CNC (up to 0.30%) in sealed-cured AAM samples improves their flexural strength due to the crack-bridging mechanism of CNCs. The addition of CNC densifies the microstructure of OPC samples by increasing the degree of hydration, however, no significant impact on the microstructure of AAMs is noticed. The OPC sample with CNC has approximately 25% increase in the degree of hydration at inner depths which can be attributed to the internal curing potential of CNC materials. The initial water absorption rate of heat-cured AAM samples is lower than the sealed-cured AAM samples and comparable to the OPC system. The developed printable “alkali-activated-CNC” composites can provide an overall reduction in the environmental impacts of the 3D-printed cementitious composites by eliminating/reducing the need for different chemical admixtures to improve 3D-printed material consistency and stability, and replacing 100% of portland cement with fly ash and slag. / Civil Engineering