Inkjet printing of ceramic materials is a shaping process of interest for building micrometer-sized components. It consists of depositing droplets of colloidal inks according to a printing pattern designed to obtain a given final part. Improving the printed part properties, e.g., thermal or electrical, requires to tailor the printed material's local structure and orientation. Electric field is an efficient external stimulus to control particle orientation. A major challenge is to efficiently couple the effects of electric field and those of capillary, viscous, and evaporation phenomena occurring during inkjet printing. In this paper, the effect of an external electric field on the structuration of inkjet deposits is investigated. Suspensions of mica platelets dispersed in binary mixtures of chloroform and silicone oil are ejected on demand on a glass plate. An electric potential difference is applied by means of a set of electrodes below the glass substrate, separated by a small gap in order to maximize the electric field on the surface of the plate. A cartography of splat morphology and structuration for different inks as a function of applied field is performed. Promising experimental conditions display particle arrangement and limited splat deformation, whereas others lead to fingering. This paves the way to a novel additive shaping process by adding another smaller scale of structuration to inkjet printed parts.

This work investigates the grinding of a mica powder in an organic medium in order to make the particle size compatible with the inkjet process using a high-energy ball mill. A detailed protocol leading to size reduction without altering structural properties of interest of this material has been successfully developed. Two steps are necessary, namely dry grinding and wet grinding in ethanol. The final particle size obtained was D90 = 1.9μm which is very close to the size requirement of the inkjet process related to the printing nozzle diameter (52μm). The mica morphology in the form of platelets was shown to be conserved by means of scanning electron microscope observations. X-ray diffraction confirmed that the mica did not undergo any change in its crystallographic structure. The decrease in particle size was revealed by the broadening and intensity drop of the diffraction peaks. Thermogravimetric analyses highlighted a shift of dehydroxylation reactions towards lower temperatures, which is also coherent with platelet size reduction.

The housing sector today uses elaborate materials such as cement, iron, sand, often prohibitively expensive and whose production generates a strong environmental impact (scarcity of resources, transport, greenhouse gas greenhouse, etc.).In order to meet the challenges of sustainable development, earth construction is experiencing a resurgence of interest these days.Despite its many advantages, raw earth material has drawbacks, in particular its low mechanical resistance and its loss of geometric characteristics in the face of water, which slow down its development.As part of this study, the mechanical characteristics and durability of raw earth were improved by using residual water from the processing of Parkia Biglobosa (nere) and Vitellaria Paradoxa (shea) nuts in order to optimize its use for the construction of modern buildings.To this end, the decoctions resulting from the artisanal transformation of the nut of the Parkia Biglobosa into African mustard and of the Vitellaria Paradoxa into shea butter were added to the raw earth according to volume proportions of 25%, 50%, 75% and 100% of the aqueous solution to obtain the projected composites.Thus, mechanical characterization and durability tests were carried out on the composites obtained.The results revealed that the decoctions of Vitellaria Paradoxa and Parkia Biglobosa improve the compressive strength of the material by up to 90% and 260%, respectively.Furthermore, these decoctions improved the resistance to water penetration of the 100% additive composite by 1.5 times for Vitellaria Paradoxa and 5 times for Parkia Biglobosa.This study shows that it is possible to use decoctions as raw earth stabilizers to build modern, ecological buildings at lower energy costs.However, more in-depth studies on surface wettability and long-term durability are planned to better characterize the geomaterial.

In the mining district of the Abitibi region (Canada), several underground mines use cemented paste backfill (CPB) for ground support.The binder typically used is a blend of 20% general use Portland cement (GU) and 80% ground granulated blast furnace slag (GGBFS), and qualified as the reference binder (RB).Using the RB always allows CPB to achieve the unconfined compressive strengths (UCSs) targets required.Due to its relatively high price, limited GGBFS availability and the high carbon footprint attributable to GU manufacturing, the search for alternative binders becomes imperative.Alkali-activated binders (AABs) made of GGBFS, and type F fly ash (FAF) activated using NaOH, were tested at the laboratory scale.This activation process achieved similar UCSs of CPB prepared with the RB.Unfortunately, the economic and environmental assessment of these AABs suffers from the high costs of NaOH, its high carbon footprint and GGBFS dosage, which is still significant.Consequently, the industrial application of these AABs in mine backfilling becomes challenging.Sorel-Tracy (Quebec, Canada).This byproduct was successfully tested in a CPB formulation.Moreover, FAF and fine glass powder (FGP) are proposed as partial replacement to GGBFS.The results show that at 28 days the UCS values of CPB prepared with the GGBFS/CDSD mixtures are comparable to the ones of the RB.At 7 days, satisfactory UCS are obtained and can reach the same UCS of the CPB prepared with the RB by adding only 5% clinker to the GGBFS/CDSD mixture.In addition, several mixtures have shown comparable and even higher UCSs to the RB with lower costs and smaller carbon footprints (CO2eq).The results are promising and encouraging for a future industrial application. The proposed alternative to NaOH consists of using circulating dry scrubber dusts (CDSD) from the desulfurisation process of Rio Tinto Iron and Titanium operations at

Luminescent, transparent nanocomposites incorporating very tiny crystals in glassy host matrix are a strategy to control a local structure with low phonon energy and/or adjustable band structure, and the charge‐transfer state of luminescent centers such as rare‐earth ions, resulting in their high photoluminescence (PL) efficiency and controllable absorption–emission route mechanism. For this purpose, it is important to know how many luminescent dopants can be incorporated into the nanocrystal domains. Herein, Eu3+‐doped ZrO2–SiO2 nanocomposites are considered as a test case, together with the starting gel thermal evolution. The progressive sol–gel chemistry enables the preferential introduction of Eu3+ ions into the ZrO2 nanocrystals. An analytical method using the Eu3+ PL decay curves quantitatively reveals for the first time that the number of Eu3+ ions doped in the ZrO2 crystalline nanodomains, which is obtained above 900 °C, exceeds 60%, and increases to 76% when the thermal treatment temperature is 1100 °C. The fractional number of Eu3+ ions and the local asymmetry ratio of Λ = I(5D0 − 7F2)/I(5D0 − 7F1) for each region are estimated as Λ = 2.1–2.9, Λ ≈ 15, and Λ = 4.6–7.4 for the ZrO2, boundary, and SiO2‐rich glass phases, depending on the heat‐treatment temperature.

The aim of this study is to improve the sustainability of cement and concrete mixes. To do so, the fine recycled aggregates (FRA) from construction and demolition wastes (CDW) were used in cement raw meals (CRM) to produce recycled clinker and cement to be used in the mix design of new concretes. About 7000 tons of clinker containing 1000 tons of FRA were generated at industrial scale, in a cement plant. Clinker was then incorporated into CEM I and CEM II recycled cements. The findings of this study confirm the feasibility of producing clinkers and cements with FRA, meeting the industry's required performance, and at the same time reducing resource depletion in the cement industry. These cements were also incorporated in new ordinary and high performance concretes. The results show slight differences in mechanical and durability properties, when recycled cements are used. From a performance approach viewpoint, the high performance concretes (conventional and recycled) are ranked as highly durable, while the ordinary concretes are ranked as low-medium durable ones, regardless the presence of FRA in cements.

The partial substitution of Portland cement by a mixture of calcined clays and limestone fillers offers a promising way to reduce the environmental impact of concrete while improving its long-term mechanical performance and durability properties. However, the literature shows that calcined clays can display a higher water demand than Portland cement, which implies the use of additional mixing water or superplasticizer to maintain appropriate workability. This study aims to determine the optimal proportion of ternary mixes, i.e. cement, calcined clays and limestone fillers, in order to obtain the highest possible packing density influencing the water demand. The associated experiments were conducted with one CEM I, two metakaolins (calcined clay) and three limestone fillers. Optimization was performed using the Compressible Packing Model of granular mixtures, which notably considers the grain size distribution and virtual packing densities (beta(i)) of the various materials. In conjunction with this model, the tests carried out on pastes of normal consistency controlled by the Vicat apparatus or the spread of mortars show that the type and amount of metakaolin used have a high impact on compactness given their particularly low virtual packing densities (beta(i)). Moreover, this study demonstrates that the addition of limestone fillers improves packing density, but the grain size distribution proves not to be the key parameter, especially in mortars. Lastly, when the water demand of the metakaolin is high, a large limestone proportion (30% vol.) allows significantly enhancing the spread and manufacturing mortars with a compressive strength of close to 32.5 MPa at 28 days.

Studies on recycling of deconstruction concrete into new concretes show that it is difficult to integrate fine recycled concrete aggregates in new concrete due to the high proportion of cement paste in the fine fraction which is porous and absorbs a lot of water. A way to upgrade this fraction is to use it in ground form as a main constituent of cement. Four types of fine recycled concrete aggregates were ground and added to an ordinary Portland cement type with a substitution rate of “25% wt%” in order to form Portland cement type CEM II/B. The mechanical strengths of the mortars with these composite cements were performed at 2, 7 and 28 days. The study shows that these ground fine aggregates do not act only as fillers but also have a binding property. This is due to their carbonate content which comes either from the natural aggregates used for the manufacture of concrete or from the carbonation of portlandite released during the cement hydration.

In cemented paste backfill (CPB), tailings are commonly bound with Portland cement (GU) blended with ground granulated blast furnace slag (GGBFS) and/or fly ash (FA). Instead of using GU, alkali activation of GGBFS and FA is possible; this alternative has been intensively investigated in the concrete field. However, the development of an alkali-activated binder (AAB) recipe suitable to CPBs is still challenging, especially due to the specificities of the mine tailings. This study presents a methodological approach to formulate suitable AAB for CPB at the laboratory scale. First, potentially reactive mine tailings were substituted with fine siliceous sand to investigate the mechanical properties related to the binders; the new CPB was called simulated cemented paste backfill (S-CPB). Secondly, mixtures and pure pastes were created to investigate reaction kinetics and microstructural properties of such binders by various techniques. This methodological approach allowed the optimization of the binder composition and mechanical properties independently of the mine tailing characteristics. Once satisfac-tory formulations were elaborated, they were applied to the CPB and were evaluated economically and envi-ronmentally in terms of CO2-eq. Results showed that 75GGBFS/25FA_F activated by NaOH within a [0.5 N; 1 N] concentration interval can be used as a binder in CPB instead of the traditional GU/GGBFS blended binder. These findings and methodology are promising and could help to promote new eco-friendly binders in CPBs. However, the cost of NaOH and the CO2-eq footprint are still significant, so further considerations and research are needed to apply AAB in CPB at an industrial scale.

Materials containing ground granulated blast furnace slag (GGBFS) display a transient green-blue color after demolding. This greening effect has been investigated for leaching behavior and ecotoxicological impact. Color of concretes and pure pastes containing GGBFS was assessed with a portable spectrophotometer, and samples were then submitted to a tank monolith leaching test. Ecotoxicological tests were conducted on reference sample and a green concrete sample at both natural and adjusted pH of 8.1. Main results support that the temporary greening effect of GGBFS-containing materials has no particular impact neither on the chemistry of leachates, nor ecotoxicity. Additionally, alkaline leachates are the main issue of leached cement or GGBFS based materials with pH around 11.5-12.5. Alkaline pH is a preponderant factor of ecotoxicity to sensitive organisms such as Daphnia magna, immobilization assay (48 h) resulting in 5.10 Toxic Units (TU) for reference sample at pH 12.50 against 1.38 TU at pH 8.10. Furthermore, sulfides are a specific issue of GGBFS materials concentrated up to 0.94 mmol m(-2) in leachates, having an ecotoxic impact on living organisms at all trophic levels. At pH 8.10, green concrete leachates have 4.85 TU for Raphidocelis subcapitata growth assay (sulfides concentration of 0.63 mmol m(-2)) against 3.0 TU for green concrete sample. However, sulfides are easily removed from natural solution by oxidation or evaporation. (c) 2021 Elsevier B.V. All rights reserved.

This paper discusses the comparative biolcolonization of cementitious pastes made with two Portland Cements and two Calcium Sulphoaluminate Cements exposed for 18 months in an actual urban sewerage network at five different sites. After an incubation period of about 18 months all the cement pastes were found to be colonized by suphooxidizing bacteria in the 5 environments studied. The results obtained show that the cementitious nature is not a determining factor and that the conditions of the moment actually favour the accumulation of secondary phases on the surface due to the presence of sulphur that appears because of bacterial activity. (c) 2021 Elsevier Ltd. All rights reserved.

Carbonation is one major alteration process of cementitious materials. It can be monitored through several methods, all destructive. In this study, some preliminary investigations were conducted to monitor the carbonation process of pure portlandite with an in situ and non-destructive spectroscopic method. This complementary approach was motivated by a literature review indicating the benefits of Raman spectroscopy, but requiring innovative approaches for data acquisition and analysis. The material was selected to validate this spectroscopic monitoring, coupled with chemometrics tools to allowing an early detection of the carbonation reaction through a structure identified in the spectra data population. The carbonation occurred abruptly, and spectra analysis indicated the occurrence of phases synonymous of microstructural evolutions. Varying the atmospheric percentage of CO2 (0.04% - 4%) conducted to an appreciation of the kinetics of the carbonation front through the same thickness of portlandite.

Incorpoaration of recycled aggregates (RAs) into cement raw meals (CRMs) can be a complementary application for construction and demolition wastes (CDWs) preserving natural resources. However, the variability of CDW chemical composition and cement plant specifies require to adapt the incorporation rate on a case-by-case basis. This study presents a chemical and mineralogical characterization (X-Ray diffraction/fluorescence and thermal analyzes) of eight CDWs from different categories and origins. Laboratory clinkers syntheses show that these recycled materials affect slightly the raw meal burnability and the clinker composition mostly likely due to their mineralogical composition (quartz and feldspars contents). These results supplemented by literature review allow discussing the incorporation rates depending on three parameters: the RAs composition, the cement type and the cement quarry composition. This paper provides new insights concerning the use of recycled aggregates in cement raw meal, and shows that the maximum incorporation rate is mainly between 10-20% (50% of the 180 raw meal calculations), occasionally lower than 5% (13%) or higher than 30% (17%). Given the RAs incorporation effect (marl replacement, quartz proportion, etc.), it is even recommended to keep a rate below 10%.

The "greening effect" refers to hardened concrete containing Granulated Blast-Furnace Slag (GBFS) that displays a vivid blue-green color after removal of formwork. This temporary coloration effect, which fades within a few days to weeks, has raised concerns about its potential impact on the environment. Three types of leaching tests were conducted to assess different potential release scenarios: a sprinkling test, a static monolith tank test and a batch test on crushed samples. Slag content was linked to a higher release of sulfur anions in the leachates, in the form of sulfides, thiosulfates and sulfates. Most of these anions came from the GBFS, where sulfur is mainly in the form of sulfides with thiosulfates and sulfates as the main products of sulfide oxidation. Sulfate levels, however, were lower than threshold limit values for both inert waste and alternate materials reused in road construction. Moreover, no chromium, or other hazardous metals, were detected in the leachates.

Geopolymers are aluminosilicate materials geosynthesized by alkaline activation of aluminosilicate minerals and/or industrial byproducts. This study seeks to understand the geopolymerization processes that could occur in Al/Si-rich mine tailings for producing geopolymer paste backfills (GPB). To do so, the alkaline dissolution of fifteen, commonly encountered pure aluminosilicate minerals was investigated. Different relationships of alkaline dissolution extents were investigated. This revealed that the dissolution extent of the involved mineral depends primarily on its crystallization conditions as well as its chemical composition. Preliminary geopolymerization tests were conducted on conventional mine tailings from the Abitibi region of Quebec, Canada. These tests suggested that GPBs could be obtained with appreciable compressive strengths (UCS) (from 79 to 318 kPa) at low alkalinities ([NaOH] <= 1 mol/L) in the long term (beyond 28 days). However, in the short term (<= 7 days), the use of more soluble aluminosilicate materials is mandatory to ensuring the required target UCS for a GPB.

•A rational method is proposed for the mix design of plant aggregates concrete.•The volume of air trapped in this type of concrete is very important.•We cannot ignore such a quantity of air in any formulation process.•The volume of air depends only on the mixing time and the mode of implementation.

Granulated or ground granulated blast furnace slags (GBFS and GGBFS, respectively) are common products used as hydraulic binders (sand 0/2) in road construction or after grinding as an addition to clinker or as an addition in concrete formulations. In road construction, the pavement structure layers are described by the EN 14227-2 standard. The reactivity of the GBFS is defined by the alpha coefficient (α) which is the product of the specific surface of the fines by the sand friability (EN 13286-44). The higher the α coefficient is, the better the reactivity of the slag. Based on the physico-chemical characterization of 28 samples of GBFS produced at the same plant, this study shows that the α coefficient is variable whereas the others characteristics such as chemical compositions or water content are constant. This variability is essentially due to the specific surface of fines, which represent only a very small fraction of GBFS. In order to control the mechanical performance of road granular mixtures, addition of different proportion (0, 1, 2.5 and 5 wt%) of GGBFS has been investigated for 1 year. This article shows that an addition of 2.5 or 5 wt% of GGBFS can be used to improve the mechanical performance of the hydraulic bound mixtures and modulate the α coefficient variations.