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The high-temperature transformations and crystallization of K-based inorganic polymers made from FeO-SiO2 and FeO-SiO2-Al2O3 iron-rich model slags were investigated, with particular focus on the effect of the Al/K and Si/K molar ratios. Upon firing to 1100 °C, the main crystalline phases were hematite and (iron) leucite. Addition of corundum decreases the crystallization rate of leucite. Increasing the Al/K molar ratio increased the thermal stability due to the substitution of Al3+ for Fe3+ in leucite. The Si/K molar ratio impacted the crystallization of leucite. Upon firing to 1100 °C and 1350 °C there was a linear correlation between the amount of leucite and the Si/K molar ratio. Higher Si/K molar ratio resulted in ceramics with higher glass content and lower thermal stability. Thus, the phase assemblage can be adjusted by changing the amount of activator.

Discrete spacers allow to transversally connect planar textiles and to transform them into pseudo-3D architectures. These 3D textiles can provide the optimal reinforcement in cement composites as the concrete casting process is enhanced and the textile placement within the mould is well-controlled. This research investigated the effect of discrete spacer connections on the flexural properties and cracking behaviour of TRCs and performed a comparison with equivalent 2D TRC systems (same in-plane textiles but without connections) and with knitted 3D textiles. Additional investigated parameters were the material of the reinforcement (glass, carbon) and the density of the textile (fibre volume fraction of the composite). A four-point bending experimental campaign was conducted on four different textile configurations containing (i) no connections (ref), (ii) four spacer connections distributed over the shear zone, (iii) nine spacer connections distributed over the entire length between the supports (both shear and constant moment zone) and (iv) 3D knitted connections. The spacer connections resulted in a pronounced post-cracking stiffness increase and a positive influence on the crack formation of the TRC. Their influence was however dependent on the fibre volume fraction (Vf) of the in-plane reinforcement; configurations with a higher Vf required a higher degree of connections to showing a post-cracking stiffness increase.

Although concrete is a prominent building material in nearly all construction applications, it is also known for its reinforcement corrosion and thus material degradation due to crack formation. These severe durability issues ignited the use of microorganisms to self-heal concrete cracks in a biological way by promoting the precipitation of CaCO3 on their cell walls. Filamentous fungi have recently emerged as high-potential self-healing agents because of their ability to grow in large mycelial networks providing abundant nucleation sites for CaCO3 precipitation. Based on the extensive research already conducted on bacteria-based self-healing concrete, protection of the microbial spores in the concrete mix is key to the survival of the microorganism. This research therefore applied a natural encapsulation technique derived from bacteria-based literature on fungal spores. The fungus Trichoderma reesei, already known in the field of self-healing concrete, was used to prepare the capsules. First results showed that the fungus was able to withstand the encapsulation process, yet could not survive when embedded in cement due to its harsh conditions. The possibilities to optimize the procedure are however discussed in the paper and give rise to a broad range of research opportunities.

The pursuit of low-CO2 technologies has led to a surge in research on alternative cementitious materials, of which alkali-activated materials are a large family. In recent years alkali-activated materials have expanded to encompass Fe-rich precursors in addition to the more commonly employed aluminosilicate precursors. The formation mechanism of alkali-activated materials from two Fe-rich synthetic slags has been assessed by employing in-situ X-ray total scattering and subsequent pair distribution function analysis. The evolution of the local atom-atom correlations reveals three reaction stages. After the dissolution of Fe-silicate clusters from the slag, a binder phase is formed with Fe in both Fe2+ and Fe3+ oxidation states. The Fe2+ state is present in the form of trioctahedral layers, similar to those in Fe(OH)2, while the Fe3+ is likely located in the polymerized silicate network. Exposure to air causes the Fe2+ species to transition to the Fe3+ state. ispartof: Cement and Concrete Research vol:122 pages:179-188 status: published

The molecular structures of CaO–FeOₓ–SiO₂ slags and their inorganic polymer counterparts were determined using neutron and X‐ray scattering with subsequent pair distribution function (PDF) analysis. The slags were synthesized with approximate molar compositions: 0.17CaO–0.83FeO–SiO₂ and 0.33CaO–0.67FeO–SiO₂ (referred to as low‐Ca and high‐Ca, respectively). The PDF data on the slags reasserted the predominantly glassy nature of this iron‐rich industrial byproduct. The dominant metal‐metal correlation was Fe–Si (3.20‐3.25 Å), with smaller contributions from Fe–Ca (3.45‐3.50 Å) and Fe–Fe (2.95‐3.00 Å). After inorganic polymer synthesis, a rise in the amount of Fe³⁺ was observed via the shift of the Fe–O bond length to shorter distances. This shortening of the Fe–O distance in the binder is also evidenced by the apparent rise of the Fe–Fe correlation at 2.95‐3.00 Å, although this feature may also suggest a potential aggregation of FeOₓ clusters. In general, the atomic arrangements of the reaction product was shown to be very similar to the precursor structure and the dominance of the Fe–Si correlation suggests the participation of Fe in the silicate network. The binder was shown to be glassy, as no distinct atom‐atom correlations were observed beyond 8 Å. ispartof: JOURNAL OF THE AMERICAN CERAMIC SOCIETY vol:101 issue:12 pages:5846-5857 status: Published online

Bisphenol A based polyester is commonly used in the industry as a binder, or tackifier, to produce cost-saving preforms in Liquid Composite Moulding processes such as Vacuum Assisted Resin Transfer Moulding (VARTM). However, it is often reported that the presence of these polyesters has a detrimental effect on the mechanical properties of the resulting composite laminates. This study shows that interlaminar toughness can be increased without negatively affecting other properties by a applying a bisphenol A based polyester binder. Both polyester modified epoxy resin as well as polyester modified glass/epoxy laminates are studied. It is shown that the presence of the polyester has a profound effect on the curing characteristics and glass transition temperature of the epoxy resin. Furthermore, fracture toughness experiments (Single Edge Notch Bending) show that there is an optimum polyester concentration which leads to a toughened epoxy matrix. Composite laminates are produced from binder coated glass fibre plies with VARTM. Double Cantilever Beam fracture experiments show that the polyester binder increases the Mode I interlaminar toughness by 60 %. Three point bending experiments show that the flexural properties were not negatively affected by the presence of the polyester in the interlaminar region between plies.

Most of the effort in electrospinning has been spent on the spinning of various single polymer-solvent systems. However, the high demand for materials with specific properties indicates the need to electrospin polymer blends. Electrospinning of blends containing a synthetic and a natural polymer enables us to combine the favourable characteristics of both (e.g. biocompatibility and sufficient mechanical strength) into one material, which is often necessary in for example medical applications. A morphological characterization of these blend nanofibres is however crucial because there is a broader range of polymer properties influencing the resulting nanofibres. In this work, chitosan/polycaprolactone (CS/PCL) solutions were electrospun using an acetic acid/formic acid solvent system to create antibacterial biodegradable blend nanofibres. The fibres were characterized and the parameters influencing the stability of the production process were analysed. The fibre characterisation includes techniques such as SEM,thermal analysis (using differential scanning calorimetry and dynamic mechanical analysis) and vibrational spectroscopy (infrared spectroscopy). It was found that by adding CS to a PCL electrospinning solution, the fibre diameters and deviations can be lowered because of two possible causes. The first is the presence of more charges due to the polycationic nature, possibly reducing the diameter by more extensive jet splaying. The second effect of CS is a significant increase in viscosity, enabling the production of electrospinnable solutions with a lower total polymer concentration. Also other specific blend fibre properties, identified by a variation of techniques, can be linked to the CS addition. Their analysis illustrates the influence of polymer blends on the electrospinning process and the nanofibre morphology.