The use of Mount Etna volcanic ash in the production of bricks with good physical-mechanical performance: converting a problematic waste product into a resource for the construction industry

Volcanic ash emissions are responsible for serious damage to buildings. They can also affect vehicle traffic, cause airport closures and may be hazardous for human health. To verify the effects of the potential addition of this residue to the mixture used in the production of bricks, a detailed study of the clayey material, the volcanic ash and the bricks fired at 800, 950 and 1100 ºC was conducted, assessing chemical, mineralogical, physical, mechanical and durability aspects. The addition of 10 to 20 wt.% of volcanic ash delayed the appearance of new phases during brick firing and made them less porous. The bricks maintained their orange colour and became more compact as the firing temperature increased due to sintering and vitrification processes. The addition of volcanic ash reduced the strength of the bricks although the values were always above the limits recommended for construction work with ceramic materials. Bricks with added volcanic ash increased their resistance to decay due to salt crystallization and the general behaviour of the bricks improved when they were fired at high temperatures.Grupo de Investigación RNM 179 de la Junta de Andalucí

Technical quality of solid bricks made using clayey earth with added coffee grounds and fly ash

This paper analyses the effects of the addition of organic (coffee grounds) and inorganic (fly ash) residues to a clayey soil rich in quartz and other silicates used as a raw material in brick production. To this end the mineralogy, texture, durability and physical and mechanical properties of solid bricks fired between 800 and 1100 ºC were studied. The results show that as the firing temperature increased, the phyllosilicate content decreased and mullite appeared. The matrix became less birefringent due to gradual vitrification of the samples, especially after 950 ºC. Vitrification resulted in more compact, less porous samples. The addition of residues did not affect the mineralogy, but it did alter certain physical parameters such as colour and porosity. The largest colour differences were detected after the addition of fly ash, which usually caused a whitish patina to develop on the surface of the fired bricks, while the highest porosity values were detected in bricks with coffee grounds, significantly reducing the bulk density. The increase in firing temperature improved the mechanical resistance and durability of all the bricks regardless of their composition.Grupo de Investigación RNM179 de la Junta de Andalucí

Roman brick production technologies in Padua (Northern Italy) along the Late Antiquity and Medieval Times: Durable bricks on high humid environs

Production technologies of Roman to Medieval times bricks on the city of Padua were addressed by means of a multi-analytical approach, consisting in Spectrophotometry, X-Ray Fluorescence (XRF), Powder X-Ray Diffraction (PXRD), Polarized Optical Microscopy (POM) and Scanning Electron Microscopy (SEM- EDS). The Early-Christian (5-6 th centuries) and Romanesque (12-13 th centuries) areas of the Basilica of Saint Justine of Padua (5/6-16 th centuries), and the remains of the Roman necropolis (1-3/4 th centuries) still preserved under the basilica, were selected to collect the bricks in order to define possible differences between the materials used for the various building phases. The walls are mainly shaped by yellow (with pale and dark hue) and beige colored bricks with an overall good conservation state. The ceramic bodies of this type of bricks showed the development of high-temperature phases but a low sintering degree was achieved. Moreover, secondary phases such as zeolites and calcite were formed, within almost the pale-yellow bodies and intensively precipitated through the groundmass of the beige bricks, respectively. Mg-rich calcareous clays and chloritic-illitic clays were used, firing temperatures of or over 900 °C were reached and more porous ceramic bodies were produced when higher was the carbonate content on the raw clays. A lesser carbonate content of the base clays and/or the decrease in the firing temperatures were the main technological modifications progressively accomplished, leading to color changes on the ceramic bodies from yellow to beige hue. The Roman production technologies might be largely inherited by the brick makers during the Late Antiquity and Medieval times in the city and the reuse of more an- cient bricks during the Medieval Times was confirmed. Such reuse operations have allowed to observe that under high humid conditions the yellow hue bricks have been rather good preserved, while when exposed to insolation and fluctuations of the environmental conditions a significant granular disaggrega- tion -with the concomitance darkening of the color pastes- is developed. The color of bricks may entail an identifier of a specific construction period of the city and durable bricks from local clays, especially suitable for high humidity areas and that may preserve the aesthetical values of the city of Padua, may be currently produced.European Union's Horizon 2020 Research and Innovation Programme, under the Marie Sklodowska-Curie Individual Fellowship 836122Junta de Andalucia RNM17

Chemical, mineralogical and physical study of Late Iron Age ceramics from Nditam: Cameroon (West central Africa)

This paper studied Late Iron Age ceramic fragments from Nditam village (Centre Region, Cameroon), the technological features and deduced the type of the raw materials used to produce them by combining different analytical techniques based on X-ray fluorescence, powder X-ray diffraction, thermogravimetry, polarized optical microscopy, spectrophotometry and hydric tests. Macroscopic observations suggest the existence of three types of ceramics according to their colour, black, greyish and red, in the two opposite surfaces, outer (or external) and inner (internal). The chemistry indicates that non-calcareous clayey material was used for ceramic production. The correlation between mineralogy, petrography and the geology of the region suggests a local production of ceramics. Moreover, the chemistry of the samples confirms the existence of the three macroscopic groups and suggests the use of local raw materials for their production. From the mineralogical point of view, quartz, feldspar and mica (biotite and muscovite) were identified in all the samples, while kaolinite and amphibole were detected in some of them. The differences in the mineralogy may indicate some variations in the firing temperature, being lower in the ceramics containing kaolinite compared to the other samples. All the samples have similar water absorption behaviour. According to the colours of the ceramics, a prevalence of oxidising firing conditions was present in the kilns. However, partial reducing and short duration firing conditions were also possible. Comparative study with the mineralogy of ethnographic ceramics from southern Cameroon shows some similarities and suggests a continuity in the use of different local clay pits in this region over time.Junta de Andalucía Research Group RNM179Research Project B-RNM-188-UGR20 of the Regional Ministry of University, Research and Innovation of the Junta de Andalucía and FEDER (Spain), a way of making Europ

Growth of metastable phases during brick firing: mineralogical and microtextural changes induced by the composition of the raw material and the presence of additives

Research Project MAT2016-75889-R Junta de Andalucía Research Group RNM179 Departamento de Mineralogía y Petrología (Universidad de Granada) Departamento de Didáctica de las Ciencias Experimentales (Universidad de Granada) Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR) Grupo de Investigación HUM613 (Didáctica de las Ciencias Experimentales y de la Sostenibilidad)We thank Cerámica Castillo Siles for providing the raw material used to prepare and fire the bricks and Cervezas Alhambra S.L. (Granada) for providing the calcined diatomite sludge with yeast. We are grateful to Nigel Walkington for his assistance in translating the original text.Mineralogical and textural changes experienced by solid bricks made without additives and others made with added halite or with added calcined diatomite sludge, and fired in an electric oven at 800, 950 and 1100°C have been studied. Different analytical techniques (x-ray fluorescence, thermogravimetric analysis, x-ray diffraction, polarized optical microscopy and scanning electron microscopy) were used to reconstruct the changes that took place inside the bricks from a mineralogical and textural point of view. These changes are similar to those that take place in nature during pyrometamorphism. Carbonates decompose and react with silicates to form gehlenite, diopside and wollastonite. Plagioclase enriches in calcium and quartz concentration diminishes. Clay minerals favour the melting of matrix and the appearance of mullite. K-Feldspar changes from microcline to sanidine. The extent of vitrification increases in line with the increase in the firing temperature. When halite is added, new silicates appear earlier at lower firing temperatures and molysite is formed. Calcined diatomite sludge contains cristobalite, which becomes part of the mineralogy of the bricks. The newly-formed phases contain certain chemical elements that are not normally found in their standard chemical composition.This study was funded by Junta de Andalucía Research Group RNM179 and by the Research Project MAT2016-75889-R

Effect of iron and organic matter on mineralogy and texture of replacement bricks for heritage conservation: The case of the Alhambra Formation soil (Granada, Spain)

Throughout history, bricks have been an important part of monumental and vernacular architecture but often suffer alteration due to physico-chemical weathering and require replacement. Local soil could be used to fabricate compatible replacement bricks with similar physico-chemical characteristics as historic ceramics. Here the mineralogical and textural evolution of bricks prepared with local soil containing iron-oxyhydroxides and organic matter and fired between 800–1100 ºC are evaluated. The study provides direct evidence for solid state formation of anorthite in contact with carbonate grains and sheds light on the fate of iron compounds under oxidizing and reducing conditions (induced by the presence of organic matter) and their influence on the textural evolution of fired bricks. Brick durability and compatibility are discussed based on their hydric and mechanical performance. The findings of this study further the understanding of temperature-induced soil mineral changes and have practical implications for the design of compatible bricks for heritage conservation and new construction.Spanish Government grant PID2021.125305NB.I00 funded by MCIN/ AEI /10.13039/501100011033 and by ERDF A Way of Making EuropeUnidad de Excelencia “UCE2018-01 - Ciencia en la Alhambra” (UGR)Unidad Cientifica de Excelencia “UCE.PP2016.05″ (UGR)Research Group “RNM0179″ (Junta de Andalucía)Funding for open access charge: Universidad de Granada / CBU

Production Technologies of Ancient Bricks from Padua, Italy: Changing Colors and Resistance over Time

Representative and very uneven texturally bricks having yellow/beige or pale or dark red colors from the Renaissance walls (16th century) of Padua, Northeast Italy, were studied by means of colorimetric, petrographic (MOP), chemical (XRF), mineralogical (PXRD) and microstructural analysis (FESEM-EDS). Starting from the color measurements of the ceramic bodies, the manufacturing technologies and their influence on the physical behavior and durability of the bricks were established. The porous system was characterized by means of hygric tests and mercury intrusion porosimetry; the compactness and structural anisotropy were defined through ultrasound velocity; the uniaxial compressive strength was determined; and durability to salt crystallization and frost action of the bricks was assessed. Mg- and Ca-rich illitic clays fired at temperatures ≥900 ◦C were used to manufacture the beige hue bodies, while the pale red bricks were made out with Ca- and Fe-rich illitic clays fired at 850–900 ◦C. A lower carbonate content on the base clays and a lower firing temperature were the main causes responsible for the changing colors from beige to red hue. The increase of the red color was associated to higher silicate inclusions content and lower development of reaction rims around grains. The low sintering degree achieved yielded highly porous bodies with diverse porous systems, leading to differential physical performance and durability of the bricks that may turn out beneficial for the conservation of the historic walls.Marie Sklodowska-Curie grant agreement No 836122CLAYONRISK ProjectResearch Group of the Junta de Andalucía RNM179MSC Actio

Use of recycled carbon fibre as an additive in the manufacture of porous bricks more durable against salt crystallization

Within the framework of the Sustainable Development Goals of the Agenda 2030, the circular economy is being promoted as a means of ensuring a sustainable use of resources and a reduction in the amount of waste produced. The aim is to reduce the demand for often scarce raw materials through the continuous reuse, recycling and regeneration of materials and products. This paper explores the use of carbon fibre from wind turbine blades as an additive in the production of new efficient bricks. Clay mixes with 0, 5 and 10 wt% additive were fired at three temperatures (800, 950 and 1100 ºC) and the fired bricks were analysed from mineralogical and physical points of view to determine their suitability for use in the construction industry. The results show that carbon fibre improves the durability of the bricks, which became 16 % more porous as the firing temperature increased. However, the compressive strength of the bricks with 10 wt% carbon fibre was about 50 % lower than that of the control bricks made without additive. It is interesting to note that the distribution of the carbon fibres within the brick varies considerably and that they are shorter and wider in the core of the samples. These results could offer an alternative line for new product development in the brick industry. The bricks tested here are an example of a circular economy in which waste from one industrial process (wind turbine blades) is reused as an input in another (brick manufacture). The environmental benefits achieved are twofold: reduced demand for clay and recycling of decommissioned turbine blades, which are currently amassed in wind turbine graveyards.Funding for open access charge Universidad de Granada/CBUA.Junta de Andalucía Research Group RNM179Research Project B-RNM-188-UGR20 of the Regional Ministry of University, Research and Innovation of the Junta de Andalucía and FEDER, a way of making Europ

Durability tests on lime-based mortars from the historic built heritage of Catania (Eastern Sicily, Italy): An experimental study

Supplementary data to this article can be found online at https://doi.org/10.1016/j.jobe.2023.108137Mortars, like any other natural and artificial stone materials, are subject to atmospheric weathering agents which affect their durability according to the intrinsic characteristics of the material, such as mineralogical composition, texture and pore structure. This paper aims to investigate the physical-chemical durability of lime-based mortars made with two different volcanic aggregates, locally known as azolo and ghiara, peculiar of the historic built heritage of Catania (Eastern Sicily, Italy). An experimental approach has been used, based on the reproduction in laboratory of historic mortars by using ancient recipes. The experimental samples have been characterized from a physical point of view and then subject to accelerated aging tests. Specifically, the samples have undergone: i) mineralogical investigations through X-ray diffraction (XRD); ii) thin section analysis by polarized optical microscopy; iii) pore structure analysis through mercury intrusion porosimetry (MIP); iii) water absorption by capillarity; iii) water vapor permeability test; iv) accelerated aging test by salt crystallization; v) decay by sulfur dioxide. Results obtained highlight that the higher microporosity which characterizes the ghiara mortars is certainly responsible for their greater water absorption by capillarity as well as for their lower resistance to salt crystallization and exposure to sulfur dioxide, with respect to azolo-based ones.PNRR project PE5 “CHANGES - Cultural Heritage Active Innovation for Sustainable Society” – Spoke 5 (CUP E63C22001960006)EU-funded PON REACT project (CUP E65F21002200005)RNM 179 of the Junta de Andalucía (Spain

Pomace from the wine industry as an additive in the production of traditional sustainable lightweight eco-bricks

This study has been funded by Junta de Andalucía Research Group RNM179 and by Research Projects PPJIB2022-17 and B-RNM-188- UGR20 of the Regional Ministry of University, Research and Innovation of the Junta de Andalucía and FEDER, a way of making Europe. We are grateful to Nigel Walkington for his assistance in revising the English text of the manuscript and to three anonymous reviewers for their helpful suggestions. We also thank Bodegas Navarro (www.bodegasn avarro.es), who supplied the wine pomace, and Ceramica Castillo Siles (www.ceramicacastillosiles.es), who provided the raw materials from Viznar and Guadix. We are also grateful to Junta de Andalucía Research Group HUM629.This research examines fired clay bricks made with waste pomace from the wine industry as an additive in brick production. To this end, we analyse and discuss the chemical, mineralogical, textural and physical-mechanical behaviour of fired bricks made with three concentrations of wine pomace (2.5, 5 and 10 wt%) and at three different firing temperatures (800, 950 and 1100 degrees C) and evaluate their durability to salt crystallization. Variations in colour were also examined. The firing process resulted in the decomposition of phyllosilicates and carbonates, the crystallization of Fe oxides and the appearance of high-temperature Ca- (and Mg-) silicates phases such as gehlenite, wollastonite, anorthite and diopside. The bricks made with added wine pomace had very similar mineralogy to the control samples made without it. The bricks made with added wine pomace were lighter than the control samples and underwent less linear shrinkage during the drying process. Particles in the wine pomace were consumed during firing, leading to the appearance of voids. The bricks made with this additive had higher levels of water absorption and poorer mechanical strength. The greatest colour differences were detected after increasing the amount of waste, which generally resulted in yellower bricks. The increase in firing temperature resulted in an improvement in mechanical resistance regardless of the composition of the bricks. However, bricks fired at 1100 degrees C made without additive are more resistant to damage caused by salts than those made with wine pomace.Junta de Andalucia RNM179Regional Ministry of University, Research and Innovation of the Junta de Andalucia PPJIB2022-17, B-RNM-188- UGR20European Union (EU) Spanish GovernmentFEDERJunta de Andalucía Research Group HUM62