The aim of this work was to develop an alkali activated matrix based mainly on fly ash, to determine the ability to fix lead in these matrices, the impact of added lead on mechanical properties and to reveal the way of lead fixation in these matrices. The matrices consisted mainly of fly ash (four from fluidized bed combustion, one pulverized coal combustion) with an admixture of blast furnace slag and sodium silicate as an activator. Lechates were prepared on the basis of the ČSN EN - 12457-4 standard, lead concentrations in them were measured using an atomic emission spectrometer with inductively coupled plasma. The strengths of the samples were measured after 28 days. Images, element maps and element spectra were taken to determine the structure using a scanning electron microscope with an electron dispersion spectrometer, the samples were analyzed on an infrared spectrometer with a Furier transform, X-ray diffraction analysis and electron spectroscopy for chemical analysis were also used. The individual measurements showed that lead is accumulated in the form of hydroxide. The impact of lead doping on strength of the matrix was different for individual samples. Matrices from both types of fly ash released minimal amounts of lead into leachates, so it is possible to use them to fixate lead.

Alkali activated binders have the potential to become an alternative construction material to ordinary portland cement binders. This thesis concentrates on durability testing of alkali activated blast furnace slag and fly ash based concrete. The chosen aspects of durability included sulfate resistance, acid resistance, carbonation, freeze-thaw resistance, frost-salt resistance and porosity. Microstructural changes and formation of new crystalline phases were observed using XRD and SEM-EDX analysis. Potential application of the tested material from the durability point of view was evaluated by comparison with a reference ordinary portland cement based concrete.

This master thesis is concerns the preparation of Alkali Activated Materials, specifically Alkali Activated Slag (AAS), with the addition of fiber reinforcement. Alkali Activated Materials have great potential for use in construction practice. However, their use is limited by certain undesirable properties, which can be diminished by adding fiber reinforcement. This thesis deals with the influence of carbon fibers (2 % by weight of the binder) and carbon nanotubes (0,2 % by weigh of the binder) on the mechanical properties, microstructure and shrinkage of AAS. The results of the experiments which were carried out correspond with the literary research. Conclusions of this thesis agree with research published in original scientific papers.

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

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.

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

No / The presence of free water in mortars destined for silo or bagged storage can lead to the degradation of the binder phase. Such water may be present as a result of using wet, as-delivered sand or as a consequence of prior processes such as de-activation of Roman cement. Thus, water must be removed from the system prior to storage. Part 1 of this paper describes the control of a technique by which quicklime is added to the wet system which principally dries it by both slaking the quicklime and evaporation as a consequence of the exothermic slaking reaction. Two examples of mortars are presented in which excess water is removed from the system by the inclusion of quicklime. In the first, the water is present in the as-delivered sand and the binder is a combination of the slaked lime and ggbs. In the second, the water remains after pre-hydration of a Roman cement which is a process to retard its rapid setting characteristics. It is shown that optimally dried mortars are not subject to degradation following storage of both mortar types. (C) 2015 Elsevier Ltd. All rights reserved.

Alkali activated materials have great potential to be a material that could compete with Portland cement. Compared to concretes based on Portland cement they often exhibit greater durability and resistance to aggressive agents such as sulphates. Also their resistance to high temperature is substantial. This work is devoted to research on behavior of alkali-activated materials, particularly fly ash activated by sodium water glass and sodium hydroxide, exposed to these extreme conditions. The evaluation of properties was performed based on the detection of physico-mechanical parameters and microstructure examination by RTG diffraction analysis and scanning electron microscopy (SEM).

The purpose of this project was to produce a “greener” cement from granulated ground blast furnace slag (GGBS) using non-Portland cement activation. By eventually developing “greener” cement, the ultimate goal of this research project would be to reduce the amount of Portland cement used in concrete, therefore reducing the amount of carbon dioxide emitted into the atmosphere during cement production. This research studies the behavior of mineral binders that do not contain Portland cement but instead comprise GGBS activated by calcium compounds or fluidized bed combustion (FBC) bottom ash. The information described in this paper was collected from experiments including calorimetry, which is a measure of the release of heat from a particular reaction, the determination of activation energy of cement hydration, mechanical strength determination, and pH measurement and identification of crystalline phases using X-ray diffraction (XRD). The results indicated that it is possible to produce alkali-activated binders with incorporated slag, and bottom ash, which have mechanical properties similar to ordinary Portland cement (OPC). It was determined that the binder systems can incorporate up to 40% bottom ash without any major influence on binder quality. These are positive results in the search for “greener cement”.