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The present work is a review concerning the previous investigations on the vitrification behaviour of clays containing kaolinite, feldspars, muscovite (illite/sericite) and pyrophyllite. These clays are silico-aluminous and have interesting properties as raw materials for structural ceramics. The mineralogical and chemical composition were determined. Then, the vitrification in these clay samples using pressed bodies was investigated by few researchers in the temperature range 800 - 1350 ºC with 0.5 - 5.5 h of soaking times. The effect of heat treatments on the degree of vitrification in these clays was characterized by bulk densities of the ceramic bodies at the fired stage. It was found some variations of bulk density values for all these clays fired in the range 1000- 1150 ºC, with marked decreases of the values obtained at 1200 ºC and 1300 ºC. A first order reaction kinetics was applied to the analysis of vitrification of the ceramic bodies under isothermal heating. The method is based on experimental data of bulk densities, being proposed for the estimation of the relative degree of vitrification resulting from different firing schedules. The analysis considered the temperature dependence of the rate of vitrification following Arrhenius behaviour. Thus, the vitrification activation energy can be obtained. The activation energies for the physical process of vitrification in these clays ranged from 45 to 151 kJ/mol. The relative rates of vitrification or degree of vitrification attained during heating and soaking were calculated. The results suggested that the contribution of vitrification due to heating in all these clays was relatively small compared to the vitrification during soaking. However, it was evidenced that the influence of the particle sizes in the thermal behaviour of these clays cannot be neglected. The vitrification rate equations, as deduced in these previous studies, can be useful tools to estimate the optimum firing conditions of these clays, allowing the extension of this method to other clay types., This work was supported by Junta de Andalucía through Research Groups TEP 204 and AGR107. The authors acknowledge helpful dis- cussions on kinetic models with Dr. F.J. Gotor, Research Scientists of CSIC.

The aim of this work is to investigate the possibility of reusing ashes obtained by the calcination of industrial sludge from the oil refining industry (ORSA) as a secondary raw material in the manufacture of alkaline activated cements or geopolymers. The incorporation behavior of 5–20 wt.% of residue in binary mixtures with rice husk ash (RHA) or chamotte (CHM) was evaluated. The cements were activated with a sustainable alternative activating solution obtained from NaOH (10 M) and diatomaceous earth. The specimens were cured at room temperature. Physical and mechanical properties were determined, and the reaction products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM-EDX). The results indicate that the addition of ORSA (5–20 wt.%) to RHA and CHM improves the mechanical strength of alkaline activated cements with maximum compressive strengths of 30.6 MPa and 15.7 MPa, respectively, after 28 days of curing, with the incorporation of 20 wt.% waste. In these mixtures, the sludge acts as a source of aluminum, promoting the formation of a higher amount of geopolymer gel N-A-S-H in materials using RHA as a precursor and also (N)-(C)-A-S-H gel in cements using CHM.

Calcium phosphate (CaP) with several chemical compositions and morphologies was prepared by precipitation using aqueous solutions of L-Glutamic acid (H2G) and calcium hydroxide, both mixed together with an aqueous solution (0.15 M) of phosphoric acid. Plate-shaped dicalcium phosphate dihydrate (brushite) particles were obtained and identified at a lower concentration of the solution of the reactants. The Ca/P ratio deduced by EDS was ~1, as expected. The nanoscale dimension of carbonate apatite and amorphous calcium phosphate, with variable Ca/P ratios, were revealed by X-ray diffraction (XRD) and scanning electron microscopy and energy dispersive X-ray spectroscopy analysis (SEM-EDS). They were characterized in medium and high concentrations of calcium hydroxide (0.15 M and 0.20 M). The equilibria involved in all the reactions in aqueous solution were determined. The thermodynamic calculations showed a decrease in the amount of chelate complexes with an increase in pH, being the opposite of [CaPO4−] and [CaHG+]. This fluctuation showed an evident influence on the morphology and polymorphism of CaP particles obtained under the present experimental conditions, with potential use as a biomaterial.

The biggest challenge for our society, in order to foster the sustainable circular economy, is the efficient recycling of wastes from industrial, commercial, domestic and other streams. The transition to a circular economy is the goal of the European Commission’s Circular Economy Action, which was first launched in 2015. In 2020 the above action plan announced initiatives along the entire life cycle of the product, with the aim to make sustainable products the norm in the EU. Therefore, it is anticipated that the above action will result in an increase in Europe’s economic competitiveness, sustainability, resource efficiency and resource security. Within this context, the suitability of ferroalumina as a raw material in the blast furnace is investigated. Ferroalumina is the product of the high-pressure filter press dewatering process of the Greek red mud generated during the production of alumina by means of the Bayer cycle. Ferroalumina is a low-cost raw material and its possible charging in the blast furnace and/or steelmaking aggregates is a step towards industrial symbiosis, where the wastes, namely by-products, of an industry or an industrial process, become the raw materials for another. In the present work the effect of ferroalumina addition as a raw material was examined by smelting ferroalumina, blast furnace-slag, lime and scrap at 1550°C in a graphite crucible and a constant slag basicity. The increase of the alumina content in the slag improves the desulfurization capacity. Moreover, the silicon exchange between slag and metal was examined. The results indicate that the alkalis’ capacity of the slag increases with the addition of ferroalumina. The analysis of the finally obtained slag suggests that it could be suitable for utilization in slag-cement production.

The present research studied a set of phyllite clays from several deposits in southeast Spain. These phyllite clays have traditionally been used as sealing material to impermeabilize roofs, embankments, ponds, construction and waste landfill, with recent applications in the preparation of new mortars. However, studies on thermal behaviour and ceramic properties of phyllite clays have been scarce. The present research showed a summary of previous characterization studies on representative phyllite clays from these deposits with additional results. Mineralogical, by X-ray diffraction, and chemical, by X-ray fluorescence characterization of these samples were summarized. Thermal analysis methods (DTA–TG and thermal diffractometry) were applied to achieve a more complete mineralogical characterization. Several phyllite clay samples were selected for a ceramic study by firing pressed powdered samples up to 1300 °C. Sintered or vitrified materials, with porosities almost zero, were obtained from these phyllite clays after firing at 1100–1200 °C, with apparent densities between 2.1 and 2.4 g cm−3. Higher firing temperatures (> 1250 °C) produced deformation and expansion of the ceramic bodies. These results allowed obtain the vitrification temperature (Tv) and the temperature of the maximum bulk density (Td). According to the previous mineralogical and chemical characterization and the values of these parameters, the phyllite clay samples were classified in three varieties, as follows: (1) Micaceous, characterized by predominant layer silicates, mainly muscovite or illite, alkaline elements (mainly K2O higher than 3.5 mass%) and lower values of both Tv and Td, (2) Quartzitic, with predominant quartz and SiO2 and intermediate values of Tv and Td, and (3) Carbonaceous, characterized by predominant dolomite, medium contents of CaO and MgO and higher values of both Tv and Td. These results are interesting for the application of these phyllite clays as ceramic raw materials.

Two series of six wet torrefaction tests were performed using a pressurized batch reactor in order to upgrade almond-tree pruning (a largely available agricultural waste in Mediterranean areas) as a fuel. The assayed maximum temperatures were in the range of 175–300 °C, held for either 10 or 60 min. Raw almond-tree pruning and wet-torrefied solid products were systematically characterized through a wide range of analytical procedures, such as bulk density, particle size, structural and elemental composition, ash content, heating values, moisture uptake, FTIR spectra and SEM micrographs. The effects of temperature and time on the wet torrefaction process of almond-tree pruning were simultaneously evaluated through the severity factor. Higher temperatures and longer holding times brought the fuel properties of wet-torrefied solid products closer to those of sub-bituminous coal. The most severe operating conditions (i.e., 300 °C held for 60 min, or a severity factor equal to 7.68) allowed achieving an energy densification ratio of 1.67. However, the optimal processing conditions in terms of energy yield, which were found at a severity factor of 5.78, led to 57.1 wt% solid yields, with a higher heating value of 24.0 MJ/kg and an energy densification ratio of 1.36.

The cement manufacturing industry is one of the main greenhouse gas emission producers and also consumes a large quantity of raw materials. It is essential to reduce these emissions in order to comply with the Paris Agreement and the principles of the circular economy. The objective of this research was to develop different types of cement clinker blends using industrial waste and innovative design to produce low-energy cement. Several types of waste have been studied as alternative raw materials. Their main characteristics have been analyzed via X-ray fluorescence (XRF), X-ray diffraction (XRD), Attenuated total reflectance Fourier trans-form infrared spectroscopy (ATR-FTIR), thermal analysis (TG-DTG-DSC) and scanning electron microscopy and energy dispersive X-ray spectroscopy analysis (SEM-EDS). The results obtained from the experimental work carried out in this research focused on the study of crude blends for low-energy cement created from industrial waste. The effect of the addition of different industrial waste types, as a substitution for raw materials, in the production of low-energy cement with high dicalcium silicate content has been investigated. Thus, the dosage design has been performed using modified Bogue equations and quality indexes (LSF, AM, and SM). The calculations of both the modified Bogue equations and quality indexes necessitate knowledge of the weight percentages of CaO, SiO2, Al2O3, and Fe2O3, determined via XRF. In this theoretical design of the different blends, it has been established that a dicalcium silicate ratio of 60–65 wt % and an LSF of 78–83% as the limit are values common to all of them. The calculation basis for the crude blends has been based on calcined materials. Therefore, the chemical composition was established, following this premise. Thus, it was possible to develop cement clinker blends with compositions of 50 wt % and 100 wt % using industrial wastes. This research has shown that the clinkerization process is one of the main options for the valorization of waste and its consideration for inclusion as a raw material within the circularity of the cement industry’s production process. Thus, waste is used as a raw material for the production of a more useful substance, taking into account the fundamental principles of the circular economy.

This Special Issue has presented the most recent advances in some of the key aspects of mining and metallurgical waste valorization [...]

Drying kinetics of olive stone and olive-tree pruning, two important biomasses from olive culture, was experimentally assessed at six different temperatures (from 343 K to 393 K) and four sample thicknesses (from 15 to 50 mm). Analysis of the drying curves revealed that Page's model was suitable for predicting the drying characteristics of both solid biofuels. From this analysis, two new mathematical equations to describe the dependence of moisture ratio with temperature and drying time were also proposed. The values of effective water diffusivity, calculated at the falling rate period by using Fick's second law of diffusion, increased when increasing drying temperature and sample thickness. Diffusivities for olive-tree pruning (3.41 × 10−8 – 32.5 × 10−8 m2/s) were almost twice higher than those for olive stone (1.87 × 10−8 – 16.4 × 10−8 m2/s).

In this study, a calcined illite clay from Bailen, Jaen, Spain, was valorized as a substitute of metakaolin in the synthesis of new geopolymeric materials. The raw materials, raw clay and c...

In this research, the use of olive pomacefly ash(OPFA) as an alkaline source for the activationof calcined clays (CC) from Bail en (Ja en, Spain) was studied. The optimal composition was obtained for 70 wt % CC and 30 wt % OPFA. The physical,mechanical and thermal properties of control geopolymers that usewater as a liquidmediumhave been studied and comparedwith geopolymers that use additional activating solutions as sodiumor potassiumhydroxide solutions (8M), or amixture of alkaline hydroxide and alkaline silicate solution (NaOHeNa2SiO3 or KOHeK2SiO3). The results showed that OPFA can be used as an alkaline activator, showing mechanical properties slightly lower than those obtained when additional alkaline hydroxide activating solutions were used. The best compressive strength was obtained for geopolymers that use alkaline silicates as an activating solution. However, the best thermal insulation properties were obtained for control geopolymers. The microstructural characteristics of the geopolymers were evaluated by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Scanning ElectronMicroscopy (SEM-EDS) that corroborate the formationof geopolymeric gel inall the specimens, beingthe amount of gel formed greater insamples using commercial potassiumactivating solutions. These results demonstrate the feasibility of using this type of waste, OPFA, as activating reagents in the manufacture of geopolymers or alkaline activated materials. The manufactured geopolymers can be used as compressed earth blocks for walls and partitions, since the specimens pursue mechanical properties that comply with current regulations, presenting better thermal insulation properties.

The sintering behaviour of a pyrophyllite clay has been investigated. The mineralogical composition by X-ray diffraction (XRD) of this sample was ∼35 wt.% pyrophyllite, ∼25 wt.% sericite/illite, ∼15 wt.% kaolinite and ∼20 wt.% quartz. The chemical composition was consistent with these results, with a total flux content of 4.18 wt.%. Prismatic bars were prepared by dry pressing using this sample and fired in the range 800–1500 °C with 0.5–5 h of soaking times. Sintering diagrams were obtained using the results of linear firing shrinkage, water absorption capacity, bulk density and apparent porosity determined in the ceramic bodies as a function of firing temperatures. It was found a trend of slight variations of bulk density values firing in the range 1000–1150 °C, with marked decreases of these values for these bodies fired at 1200 °C and 1300 °C. The temperature of maximum bulk density was determined as ∼1200 °C and the vitrification temperature was ∼1300 °C where the apparent porosity becomes almost zero. The vitrification process of the pyrophyllite clay sample was investigated using a method previously described in the literature, which considered an Arrhenius approach under isothermal conditions and a first order kinetic. It was determined an activation energy (Ea) of ∼45 kJ/mol with a linear correlation coefficient of 0.998. The relative rates of vitrification were calculated. It was found that the contribution of vitrification due to the heating was relatively small compared to the vitrification during soaking. Mullite and quartz are forming the ceramic bodies besides a vitreous or glassy phase. The thermally treated pyrophyllite clay showed a dense network of rod-shaped and elongated needle-like crystals, being characteristic features of mullite as a dense felt. The vitrification rate equation, as deduced in this study by first time, can be a useful tool to estimate the optimum firing conditions of the pyrophyllite clays applied as ceramic raw materials., En el presente trabajo se ha estudiado el comportamiento de sinterización de una arcilla con pirofilita que posee una composición mineralógica (% en peso), deducida por difracción de rayos X, de ∼35% de pirofilita, ∼25% de sericita/illita, ∼15% de caolinita y ∼20% de cuarzo. La composición química fue consistente con estos resultados y mostró un contenido total de fundentes de 4,18% en peso. Se prepararon probetas conformadas como barras prismáticas mediante prensado uniaxial, en seco, de la muestra original para estudiar su comportamiento en cuanto a sinterización en el intervalo de temperaturas 800-1.500 °C, con tiempos de permanencia desde 0,5 a 5 h. Se obtuvieron los diagramas de sinterización utilizando los resultados de contracción lineal por cocción, capacidad de absorción de agua, densidad y porosidad aparente determinadas en las probetas tratadas térmicamente en función de la temperatura. Se ha encontrado una tendencia a presentar variaciones no muy importantes de los valores de densidad de las probetas cerámicas en el intervalo 1.000-1.150 °C, con un marcado descenso de estos valores cuando se trataron térmicamente a 1.200 °C y 1.300 °C. La temperatura del máximo de densidad se produce a ∼1.200 °C y la temperatura de vitrificación ∼1.300 °C, a la cual la porosidad aparente llega a alcanzar valores casi nulos. El proceso de vitrificación de esta arcilla con pirofilita se ha investigado utilizando una metodología descrita en la bibliografía que considera una aproximación de tipo Arrhenius, bajo condiciones isotérmicas, y una cinética de primer orden. Con la aplicación de dicha metodología se determinó una energía de activación Ea ∼ 45 kJ/mol y un coeficiente de correlación lineal de 0,998. Se calcularon las velocidades relativas de vitrificación durante el tiempo de permanencia a varias temperaturas. Con la realización de este análisis se encontró que la contribución de la vitrificación debida al tratamiento térmico es relativamente pequeña comparada con la vitrificación originada por el tiempo de permanencia a cada temperatura. En las fases cristalinas, la mullita y el cuarzo constituyen los cuerpos cerámicos obtenidos, además de la fase vítrea. Esta materia prima sometida a tratamiento térmico dio lugar a un denso entramado reticular de cristales alargados, formando agujas características, de mullita como denso fieltro. La ecuación de velocidad de vitrificación que se ha deducido en este estudio, por primera vez, puede ser una herramienta de cierta utilidad para estimar las condiciones óptimas de cocción al emplear este tipo de arcillas con pirofilita y sericita como materias primas cerámicas.

In this research, the feasibility of using bottom ashes generated by the combustion of biomass (olive pruning and pine pruning) as a source of aluminosilicates (OPBA) has been studied, replacing the metakaolin precursor (MK) in different proportions (0, 25, 50, 75, and 100 wt.% substitution) for the synthesis of geopolymers. As alkaline activator an 8 M NaOH solution and a Na2SiO3 have been used. The geopolymers were cured 24 h in a climatic chamber at 60 &deg, C in a water-saturated atmosphere, subsequently demoulded and cured at room temperature for 28 days. The results indicated that the incorporation of OPBA waste, which have 19.7 wt.% of Ca, modifies the characteristics of the products formed after alkaline activation. In general terms, the incorporation of increasing amounts of calcium-rich ashes results in geopolymers with higher bulk density. The compressive strength increases with the addition of up to 50 wt.% of OPBA with respect to the control geopolymers, contributing the composition of the residue to the acquisition of better mechanical behavior. The results indicate the potential use of these OPBA waste as raw material to produce unconventional cements with 28-day curing strengths greater than 10 MPa, and thermal conductivities less than 0.35 W/mK.

The main objective of this research was to obtain calcium silicate units from alternative raw materials, such as the bottom ashes from the combustion of wooden boards (WBA), as a source of silica, and GeoSilex (G), a by-product with low energy and environmental costs generated in the manufacture of acetylene, as a source of lime. Once the raw materials were physically, mineralogically and chemically characterized, calcium silicate units were obtained by mixing different amounts of WBA residue (90&ndash, 20 wt%) and G by-product (10&ndash, 80 wt%). The mixtures were compressed at 10 MPa and cured in water for 28 days. The calcium silicate units were subjected to a wide experimental program that included the determination of physical properties (bulk density, apparent porosity and water absorption), mechanical properties (compressive strength), and thermal properties (thermal conductivity). Optimum values are obtained for calcium silicate units that contain a 1/1 WBA/G weight ratio, which have an optimal amount of SiO2 and CaO for the cementation reaction. The 50WBA-50g units have compressive strength values of 46.9 MPa and a thermal conductivity value of 0.40 W/mK. However, all calcium silicate units obtained comply with the European Standard EN 771-2: 2011 to be used as structural building materials.

This paper describes the use of industrial wastes arising from different production processes of the ceramic and marble industries as raw materials for the design and formulation of new cement clinkers with a high content of dicalcium silicate (Belite). The aim was to reintroduce these wastes in the industrial sector and take advantage of them for a greater environmental benefit, as indicated by the principles of the circular economy. Formulations containing 2.5, 5 and 10 wt% of chamotte and marble sludge, respectively, and a waste‐free formulation have been designed to obtain clinkers with a content of dicalcium silicate higher than 60 wt%. The different blends have been studied up to a maximum temperature of 1390°C by Thermal Analysis. Other techniques such as XRD, XRF, Modified Bogue Equation, Quality Indexes (LSF, AM, SM) and Optical Microscopy have been used for the study and characterization of industrial wastes, the raw materials and the high belite‐type cement dosages. The results indicate that this type of cements can be designed using different types of wastes and in this way reduce the environmental impacts caused by the extraction of raw materials and the deposition of the wastes in landfills, improving the circular economy of the construction industry.

In the present study, residue from olive groves has been used for the manufacture of clay ceramic bricks as a new environmentally-friendly solution. For this purpose, waste products of olive cultivation, such as olive prunings, leaves and wood, were ground to obtain a particle size of 0-2 mm; 7.5%, 15% and 25% of olive waste was added to the clay, clay bodies were moulded in pastes with the incorporation of 7.5, 15 and 25% by volume of waste; and finally, the green bodies were fired at 850 degrees C. The influence of the type and ratio of waste on the physical and mechanical properties of waste clay bricks was studied and compared with clay bricks without waste following standard procedures. Ceramic samples were characterized using a series of technological tests, such as linear shrinkage, bulk density, apparent porosity, water absorption, suction, compressive strength and thermal conductivity. The best results were obtained from the samples containing 7.5% olive waste showing that these organic pore-forming wastes have the potential for producing lighter bricks that could be marketed as low density clay masonry units with adequate mechanical properties and higher thermal insulating capacity. (C) 2019 Elsevier Ltd. All rights reserved.

Construction and Demolition Wastes (CDW) with low contents in Al2O3 (4–6%) and amorphous phase (16–27%) have been investigated for geopolymerization. The proportion of alkaline activators (NaOH and sodium silicate (SS)), the temperature and time of initial treatment, the curing conditions (dry, wet or sealed) and the addition of Portland cement were assessed. The low reactivity of the samples has been especially evident in those rich in carbonate aggregate, something that is not only reflected in the low compressive strength obtained (6–8 MPa), but also in the appearance of efflorescence. Temperature application (60°C–90 °C) and dry/sealed curing have generally improved results. In the case of the siliceous CDW, 28-day compressive strengths of 11–15 MPa have been reached in 20 mm-side cubic specimens and 21.5 MPa in brick prototypes. The optimum was estimated at SS/NaOH = 3.6 and 37.9% activator. FTIR, SEM and Rietveld-refined XRD analyses have corroborated the geopolymer gel formation.

The objective of this study is the stabilization of two heavy metals Pb and Zn wastes resulting from the treatment by flotation of Pb/Zn ore. The Pb/Zn wastes are encapsulated in Na- geopolymer based on Algerian metakaolin. However, various amount (0, 5, 10 and 15 wt%) of wastes are introduced within geopolymers paste. Leaching test show that Lead is untraceable in all levels of waste content up to 15 wt% because lead content of the waste is very low and its presence in the leachate is below the level of detection by Atomic Absorption Spectroscopy. In the other hand, traces of Zinc were detected in the various leaching solutions. The geopolymers 28 days ages and 10 wt% give the better results due to more stable geopolymer matrix. Leaching is increased when 15 wt% of waste was added due to limited capacity of geopolymers for the heavy metals and deterioration of the structure.

Geopolymers are a new class of non-Portland cements produced using an alumino-silicate material (natural minerals, waste and/or industrial by-products) and an alkaline activator to be subsequently cured at relatively low temperatures. The aim of this work is to produce a new type of geopolymer using metakaolin (MK), rice husk ash (RHA) and red mud (RM) by alkaline activation containing sodium silicate and sodium hydroxide (NaOH). Four different geopolymer compositions were prepared at various Si/Al molar ratios (3.85, 4.30, 4.45 and 5.30). A metakaolin based geopolymers were synthesized as a reference. Specimens were characterized by XRD, ATR-FTIR and SEM/EDS. The study revealed that geopolymerization products exhibit an amorphous homogeneous structure with acceptable mechanical properties. RMRHA1 geopolymers shows the best mechanical characteristics (30 MPa) after 60 curing days. MK-RHA-RM based geopolymers obtained seem to offer a feasible alternative to conventional Portland cement contributing to the valorization of the wastes.

In this research the effect of the incorporation of black steel slag (BSS) (25, 50 and 75 wt%) into biomass bottom ash (BBA) as precursor in the synthesis of alkali-activated materials was studied. The alkali-activated pastes were cured at two temperatures, 60 and 20 °C. Thermal curing at 60 °C produced an increase in mechanical properties at early curing ages obtaining similar properties at older ages of 90 days. The addition of up to 50 wt% of BSS resulted in alkali-activated cements with increased compressive and flexural strengths. The increase in mechanical properties could be due to the formation of a higher amount of calcium aluminosilicate gel (C-A-H-S) with respect to potassium aluminosilicate gel (K-A-H-S) or to the synergistic formation of C-K-A-S-H gel. Therefore, these specimens can be used as a binding material for concrete production to replace Portland cement, which can lead to significant environmental and socio-economic improvements by reducing CO2 emissions and consumption of natural resources.

The main objective of this investigation is to study the effect of the substitution of metakaolin (MK) (from calcined industrial kaolin) by four different calcined natural Southern Spain clays traditionally used in the brick and tile sector, as well as by the biomass bottom ash residue (BBA) from the combustion of a mix of olive and pine pruning on the synthesis of geopolymer with physical, mechanical and thermal properties comparable to those of classic construction materials. As alkaline activator , a 8 M solution of sodium hydroxide and sodium silicate have been used. Raw materials, metakaolin; Spanish clays: black clay (BC), yellow clay (YC), white clay (WC), red clay (RC) and BBA were characterized by chemical analysis (XRF), mineralogical analysis (XRD), and particle size analysis . Control geopolymers containing only metakaolin, and batch of geopolymers were formulated containing equal proportions of metakaolin, BBA and each of the four types of clay. After the curing period, at 60 °C for 1 day geopolymers were demolded and stored 27 days at room temperature. Geopolymers were characterized using Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS), XRD and Attenuated Total Reflectance- Fourier Transform Infrared Spectroscopy (ATR-FTIR). Their physical, mechanical and thermal properties have also been studied. The addition of BBA and different types of calcined clays to metakaolin gives rise to geopolymers with higher mechanical properties increasing the compressive strength of the control geopolymer containing only MK (24.9 MPa) by more than 50% for the GMK-BBA-WC geopolymers (38.5 MPa). The clays act as fillers and/or promote the precipitation of calcium-rich phases (Ca)-A-S-H-G gel that coexists with the (Na)-A-S-H gel type. The relevant results of physical, mechanical and thermal properties obtained in this research demonstrate the potential of Spanish clays and BBA as binders and substitutes for metakaolin.

The mineral composition of raw materials and the type of alkali cation plays an important role in the acidic resistance of geopolymers. This paper focuses on the study of chemical durability in hydrochloric acid of potassium and sodium based geopolymers. The study was carried out on two Algerian kaolins and compared with a kaolin from Charente (France). The acid degradation was studied using X-ray Diffraction, Fourier-Transform Infrared and Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy. The samples based on Algerian kaolins seems to have the lowest loss in mass for formulations based on potassium due to the presence of secondary minerals (quartz and muscovite). They could have occupied the pores avoiding the release of alkali cations into the acidic solution. Regarding to sodium geopolymers, the best behavior was observed with the kaolin from Charente, which can be attributed to a more stable aluminosilicate cross-linked polymer structure formed for this material, which was corroborated with the Fourier-Transform Infrared analysis.

In this communication, it is reported the first relevant results on a broad study on the preparation of calcium carbonate as precipitated nanoparticles of the polymorphs vaterite and calcite. The inorganic precursors are calcium nitrate tetrahydrate and sodium hydrogencarbonate, and the organic additive is sucrose in aqueous solution. The crystalline phases are studied by X-Ray powder diffraction, using a quantitative method, and the particle morphologies using scanning electron microscopy. When the organic additive is not used, calcite as the most thermodynamically stable polymorph is precipitated as nanocrystalline predominant phase (83%) mixed with vaterite. Using a high concentration of the organic additive (67%), vaterite is precipitated as the nanocrystalline predominant phase (> 98%). Using the additive in variable proportion produces the precipitation of the 2 polymorphs, being vaterite always the predominant phase. The morphology of the precipitated calcium carbonate shows nanospherical uniform particles with irregular contourns of vaterite and characteristic rhomboedral particles of calcite when this phase is present. According to the biocompatibility, this material shows interest in applications as biomaterial in bone implants. En esta comunicación se presentan unos primeros resultados de interés relevante sobre la obtención de carbonato de calcio precipitado como nanopartículas de los polimorfos vaterita y calcita. Se parte de precursores inorgánicos, nitrato de calcio tetrahidratado y bicarbonato de sodio, en presencia de sacarosa empleada como aditivo orgánico en disolución acuosa. Las fases cristalinas formadas se estudian mediante difracción de rayos X con un método cuantitativo y la morfología de las partículas obtenidas, mediante microscopia electrónica de barrido. Cuando no se emplea el aditivo orgánico se consigue la precipitación de calcita, polimorfo más estable termodinámicamente, como fase nanocristalina predominante (83%) mezclada con vaterita. Con una alta concentración del aditivo (67%) se obtiene vaterita como fase mayoritaria (> 98%). La utilización del aditivo en distinta proporción produce la formación de los 2 polimorfos de carbonato de calcio, siendo vaterita la fase predominante. La morfología de las partículas obtenidas muestra la formación de partículas nanoesféricas uniformes con contornos irregulares que se asocian a vaterita, así como partículas romboé- dricas de calcita cuando está presente, con potencial interés por su biocompatibilidad para su aplicación como biomateriales en implantes óseos Junta de Andalucía TEP 204

In this work, the use of waste dust filter of secondary aluminum industry (DFA) to obtain geopolymer foams has been studied. The waste was used as source of alumina and foaming agent. As precursor and principal reactive silica supplier rice husk ash was used. Precursors were chemically activated by means of a sodium hydroxide aqueous solution and a commercial sodium silicate solution. The influence of the DFA content or Si/Al molar ratio (4–7) were determined by keeping the Si/Na molar ratio of 0.7 M constant and the concentration of sodium hydroxide in the activating solution equal to 8.5 M. The geopolymer foams obtained were studied by X-ray Diffraction (XRD), adsorption/desorption of nitrogen, infrared spectroscopy (FTIR), and scanning electron microscope (SEM) techniques. The results indicated that geopolymer foams presented low values of bulk density (643–737 kg/m3) high values of apparent porosity (62–70%), low, but sufficient values of compressive strength (0.5–1.7 MPa) and good values of thermal conductivity (0.131–0.157 W/mK). Lower values of thermal conductivity were obtained for Si/Al = 4 and 5 M ratios, due to the highest apparent porosity and the highest total pore volume. These geopolymer foam materials have similar properties to other construction materials sector such as gypsum boards, foamed concrete, or insulating materials. In addition, its use in other applications of interest such as catalyst support or gas filtration materials could be investigated.

The aluminum recycling industry produces aluminum filter dust (AFD), a waste byproduct of the aluminum recycling process composed mainly of aluminum oxide in a percentage between 60&ndash, 70%, 8% calcium oxide, almost 15% sodium chloride, and between 5&ndash, 10% potassium chloride. Due to its aluminum content, this waste can be used as a raw material in the manufacture of ceramic bricks, at the same time reducing the environmental impact produced in landfill. In this work, the partial substitution of a clay mixture (40% black, 30% red, and 30% yellow clay) by different proportions of AFD in the range 0&ndash, 25 wt % for the production of fired clay brick was studied. The raw materials, clays, and waste were characterized by XRF and XRD. The brick specimens were fired at 950 &deg, C and their physical and mechanical properties, such as water absorption, water suction, loss of ignition, linear shrinkage, bulk density, and compressive strength, were analyzed. The more relevant results were obtained with the addition of up to 20 wt % AFD, obtaining bricks with physical properties comparable to pure clay-based bricks used as a reference and better compressive strength and thermal conductivity due to the balance between the melting and pore-forming effects of the waste. These sustainable bricks also comply with the regulations of heavy metals leached to the environment, as indicated by the leaching test.

El ladrillo cerámico como material de construcción industrial contribuye negativamente al deterioro del medioambiente, tanto por el agotamiento de los recursos naturales como por la elevada cantidad de energía necesaria para su fabricación, que se traduce en emisiones de CO2. La incorporación de productos residuales o subproductos procedentes de diversos procesos industriales ha dado lugar a los denominados «ecoladrillos». En este trabajo de investigación se estudia el comportamiento de ladrillos cerámicos con la incorporación de diferentes biomasas residuales con la función de generar una red porosa que modifique sus propiedades para adaptarlos a los requerimientos técnicos actuales. Para ello se han fabricado 19 tipos de ladrillos con la incorporación de 6 subproductos biomásicos: cascarilla de arroz (C), cáscara de almendra (CA), hueso de aceituna (HA), hoja de olivo (HO,) leña de olivo (LO) y poda de olivo (PO). Las biomasas se han incorporado a una arcilla convencional en tres proporciones en volumen (7,5 %, 15 % y 25 %), con tres tamaños de distribución de partícula (0/1 mm, 1/2 mm y 0/2 mm). Los resultados obtenidos muestran que el tamaño de partícula no ha condicionado el comportamiento físico y mecánico de los ecoladrillos, no así la proporción de biomasa, aunque en ningún caso se ha comprometido la normal funcionalidad de los mismos. Por el contrario, se ha observado una mejora considerable en la conductividad térmica de los ecoladrillos fabricados, fundamentalmente, con los menores porcentajes de reemplazo.

The use of coal fly ash (CFA) as raw material for the manufacture of two construction materials, fired clay bricks and silica-calcareous non-fired bricks, was investigated. Fired clay bricks were manufactured using a commercial clay and different waste ratios (0–50 wt%), moulded at 10 MPa and fired at 1000 ºC (4 h). Silica-calcareous non-fired bricks were prepared using two wastes as raw material: CFA and “geosilex”(G), a hidrated lime residue which comes entirely from acetylene industry waste. Different proportions CFA (80–30 wt%) – G (20–70 wt%) were investigated. Raw materials were moulded at 10 MPa and cured in water at room temperature during 28 days. The results indicated that the incorporation of up to 20 wt% of CFA produced fired clay bricks with physical and mechanical properties similar to control bricks without waste. However, additions of a higher amount (30–50 wt%) of residue resulted in a more pronounced decrease in mechanical properties (between 25–50%) due to an increase in open porosity. The technological characterization of the silica-calcareous non-fired bricks showed a reduction in the values of bulk density and water absorption when the coal fly ash content decreases. Silica-calcareous non-fired bricks containing between 40 and 60 wt% of CFA had the highest values of compressive strength in the range 46–43 MPa. These silica-calcareous non-fired bricks, 60CFA-40 G, 50CFA-50 G and 40CFA-60 G, presented the optimum amount of pozzolanic materials (SiO and AlO) in the coal fly ash and calcium hydroxide in the geosilex to give rise to the formation of calcium silicate hydrates and calcium aluminate hydrates, the phases responsible for the mechanical resistance increase of the construction materials. Therefore, CFA-clay fired bricks and silica-calcareous CFA-Geosilex non-fired bricks presented optimal technological properties that attain the quality standards., This work has been funded by the Project “Valuation of various types of ash for the obtaining of new sustainable ceramic materials” (UJA2014/06/13), Own Plan University of Jaen, sponsored by Caja Rural of Jaen. The authors thank the companies “Thermal Power Plant Litoral SS” and “Geosilex Trenza Metal S.L.” for supplying the ashes and geosilex, respectively. Technical and human support provided by CICT of Universidad de Jaén (UJA, MINECO, Junta de Andalucía, FEDER) is gratefully acknowledged.

Geopolymers are a new class of non-Portland cements produced using an alumino-silicate material and an activating solution, which is mainly composed of sodium or potassium and waterglass to be subsequently cured at relatively low temperatures. Those can be formulated by adding natural minerals, waste and/or industrial by-products. The study investigates the microstructural properties of geopolymers synthesized from metakaolin (MK) and the admixture of fly ash (FBA) and aluminium industry slags (AIS) at different ages of curing. Five different geopolymer compositions were prepared and characterized by XRD, ATR-FTIR and SEM/EDS. The study revealed that geopolymeric gels are identified, which show mainly glassy microstructures, in agreement with the X-ray amorphous diffraction patterns, broad FTIR features and confirmed by SEM/EDS, with promising results prior to an industrial scale., This work has been funded by the Project “Valuation of various types of ash for the obtaining of new sustainable ceramic materials” (UJA2014/06/13), Own Plan University of Jaen, sponsored by Caja Rural of Jaén.

Thermal analysis of some sericite clays, from several deposits in Spain, which are not exploited at this time, has been studied. The samples have been previously characterized by mineralogical and chemical analysis. Sericite clays have interesting properties, with implications in ceramics and advanced materials, in particular concerning the formation of mullite by heating. According to this investigation by differential thermal and thermogravimetric analysis (DTA-TG), the sericite clay samples can be classified as: Group (I), sericite–kaolinite clays, with high or medium sericite content, characterized by an endothermic DTA peak of dehydroxylation of kaolinite with mass loss, which overlapped with dehydroxylation of sericite, and Group (II), sericite–kaolinite–pyrophyllite clays, with broader endothermic DTA peaks, in which kaolinite is dehydroxylated first and later sericite and pyrophyllite with the main mass loss, appearing the peaks overlapped. X-ray diffraction analysis of the heated sericite clay samples evidenced the decomposition of dehydroxylated sericite and its disappearance at 1050 °C, with formation of mullite, the progressive disappearance of quartz and the formation of amorphous glassy phase. The vitrification temperature is ~ 1250 °C in all these samples, with slight variations in the temperatures of maximum apparent density (2.41–2.52 g mL−1) in the range 1200–1300 °C. The fine-grained sericite content and the presence of some mineralogical components contribute to the formation of mullite and the increase in the glassy phase by heating. Mullite is the only crystalline phase detected at 1400 °C with good crystallinity. SEM revealed the dense network of rod-shaped and elongated needle-like mullite crystals in the thermally treated samples. These characteristics are advantageous when sericite clays are applied as ceramic raw materials., This research is supported by Junta de Andalucía through Research Groups TEP 204 and AGR107.

It is reported the synthesis of CaCO3 vaterite as stable nanoparticles and submicron-sized by a simple and relatively rapid procedure. XRD, SEM and FTIR techniques have been used to characterize the precipitated products. The synthesis is based on chemical precipitation of inorganic salt precursors, calcium nitrate tetrahydrate and sodium bicarbonate, and using the disaccharide sucrose as an additive in aqueous medium. The role of the disaccharide sucrose is to control the vaterite precipitation after nucleation and growth. It has been found that an increase in sugar concentration promotes the crystal precipitation of vaterite with spherulitic morphology, as revealed by SEM, and changed the surface of the precipitated particles. There is a significant difference between CaCO3 precipitation in the absence and presence of sucrose. Addition of 0% of sucrose leads to 83% of calcite as identified by XRD methods. In contrast, addition of 67% of sucrose in aqueous medium produces 100% vaterite. The present results may be useful to provide a quick, simple, inexpensive and novel method for the controlled synthesis of new advanced biomaterials based on vaterite particles without hazardous chemicals and inert atmosphere, with great possibilities for industrial scale production

The industrial activities are responsible for the production of large amounts of solid wastes, which, so far, have found scarce reuse alternative. Clay-based materials show a natural forgiveness towards the incorporation of a wide variety of wastes. This study reported the changes in technological properties of clay-based mixture normally used in the production of bricks, due to the additions of a spent diatomite earth (SDE) discarded by the beer filtration process in the brewing industry. Samples containing 0-10 wt % SDE were extruded and sintered in air in an electric furnace (950 °C, for 3 h). SDE thanks to their organic substances content, during their combustion, act as pore forming agent and providing an energy support in the brick firing process. Also, the waste, because of its high silica content can act as a silica carrier. The results obtained showed that SDE, added in a percentage of 3 wt % to a brick formulation, had better influence with respect to control bricks containing only clay, improves the mechanical properties (compressive strength around 45 MPa) with a bulk density reduction of about of 2%. However, the incorporation of waste in percentage of 7 and 10 wt % had a negative effect due to increased porosity fundamentally open pores generated in the clay body by the combustion of SDE waste, leading to water suction, water absorption and compressive strength values that do not fall within the range specified by bricks UNE standards. Therefore, SDE can thus advantageously used in lower amounts (3 wt %) as silica carrier and in lower proportion as pore agent in clay bricks, with the potential to reduce fuel and natural ceramic raw material consumption, as well as, landfill costs.

The present study evaluates the suitability of several types of biomass bottom ashes [wood bottom ash (WBA), pine-olive pruning bottom ash (POPBA), olive stone bottom ash (OSBA), and olive ...

In Mediterranean greenhouses, wood is the most widespread structural element, although it is currently being replaced by galvanized steel. This substitution is not compatible with the change of a productive-constructive model, which seeks to leave a viable environment for the future generations by not exceeding the Earth’s carrying capacity, which is one of the fundamental worries of the humanity. In this sense, the present work examines the possibilities of material application of the bamboo species guadua (Guadua angustifolia), considered as a valid and sustainable alternative for greenhouse design. This initiative consists of analysing the possibilities of guadua as structural material for the “parral” type greenhouse of Almeria. For this characterization, it has been necessary to review the works related to the use of the above-mentioned bamboo species as a building material.

This investigation deals with the possibility of incorporating effluents resulting from olive oil extraction activity, as wastewater from olive-washing stage (OW) or wastewater from olive-oil washing stage (OOW), in the brick-making process. The feasibility of replacing mixing fresh water (FW) by OW or OOW of the extraction process of olive oil, in the process for manufacturing clay bricks, has been studied. FW, OW or OWW (22 wt%) was added to the clay in order for it to acquire enough plasticity to the stage of molding by extrusion. Samples containing OW or OOW were found to be comparable in extrusion performance to a control product that used FW. Once extruded, test specimens were dried at 110 °C (24 h) and fired at 850 or 950 °C (3 °C/min) for 4 h. The influence of replacing fresh water by wastes on the technological behavior of fired bricks was assessed by linear shrinkage, bulk density, water suction, water absorption and apparent porosity. Their mechanical and microstructural properties were also investigated by compressive strength and scanning electron microscopy (SEM), and thermal behavior by thermal conductivity. Results indicated that replacement of FW by OW or OOW produced slight improvements in the physical, mechanical and thermal properties of bricks. This may have been due to porosity generated by these wastes mainly closed pore type. Therefore, the use of these residues can alleviate the environmental impact generated by the industry of extraction of olive oil and, at the same time, represent an economic and water saving for the ceramic industry.

This paper studies the effect of adding bottom ash from the combustion process of biomass plants to calcium-silicate samples for use as construction material with thermal insulating properties. After a process of physical, chemical and mineralogical characterization of the raw materials, calcium-silicate samples were manufactured by mixing bottom ash (CF) with different sources of lime (calcium oxide-OC and calcium hydroxide-HC) and Portland cement (CM). The amount of bottom ash added ranged from 10% to 90% of the dry weight of the mixtures. The experimental program included a wide range of testing methods of the developed material such as water absorption, mechanical strength, porosity, microstructure, freeze–thaw and thermal conductivity. The optimal values are those containing a 1:1 ratio of SiO2/CaO, with compressive strength ranging from 25.21 MPa (CF/HC) to 61.11 MPa (CF/CM) and thermal conductivity from 0.564 W/m K (CF/OC) to 0.773 W/m K (CF/HC). The initial results obtained make it possible in principle to obtain calcium-silicate samples with low thermal conductivity according EN standard 771-2:2011.