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

The effect of local pozzolans and lime additions on the miner-alogical, physical and mechanical properties of compressed earth blocks in Argentina

Funding: This research, carried out in the laboratories of the Universidad Tecnológica Nacional, Facultad Regional Santa Fe (Argentina) and the Department of Mineralogy and Petrology of the University of Granada (Spain), was possible thanks to funding granted by the Ministry of Education of the Argentine Republic through BECAR 2020 program, by the Spanish Service for the Internalization of Education (SEPIE), and by the National Scientific and Technical Research Council (CO-NICET) of Argentina.The purpose of this research is to evaluate the mineralogical, physical and mechanical properties of compressed earth blocks (CEBs) stabilized with lime and mineral admixtures easily obtained in Argentina: natural pozzolans and brick powder. The mineralogical composition and pozzolanic potential of the admixtures were determined, as well as the devel-opment of hydraulic phases upon reaction with calcium hydroxide (lime), adding emphasis on the formation of hydrated cementing compounds. Samples with different percentages of lime and mineral additions were prepared to assess their compressive strength, wet erosion resistance and water absorption, and the results were contrasted with those of their counterparts, stabilized exclusively with lime or cement. The results obtained imply that both the brick powder and poz-zolans used have pozzolanic properties and that, in combination with calcium hydroxide, they form amorphous phases of C-(A)-S-H. However, the use of small amounts of both additions in combination with hydrated air lime in the manufacture of CEBs adversely affected their physical and mechanical properties, compared to CEB samples stabilized only with hy-drated air lime.Ministry of Education of the Argentine Republic through BECAR 2020 programSpanish Service for the Internalization of Education (SEPIE)National Scientific and Technical Research Council (CO-NICET) of Argentin

Carbonation mechanisms and kinetics of lime-based binders: An overview

The reaction of slaked lime with atmospheric CO2 in the presence of humidity leads to the formation of cementing carbonate phases in traditional aerial lime mortars and plasters. This carbonation reaction also affects the setting and degradation of hydraulic lime mortars and modern cement. Here, we present an overview of the existing knowledge on carbonation of lime-based binders, which are experiencing a revival as compatible material for the conservation of the built heritage and new sustainable construction. First, the carbonation reaction is defined and its importance in a range of technical and natural processes is outlined. This sets the ground for presenting a review of existing mechanistic models for the carbonation of lime-based materials, including the recent interface-coupled dissolution-precipitation model, and the understanding of carbonation in terms of non-classical crystallization theory. Kinetics models and experimental results for carbonation of lime-based binders (crystals and powder, as well as mortars/plasters) and its acceleration are presented and discussed. Finally, conclusions and future research directions are indicated.Spanish Government grant PID2021-125305NB-I00 funded by MCIN/ AEI /10.13039/ 501100011033ERDF A way of making EuropeJunta de Andalucía research group RNM-179 and grant P20_00675University of GranadaUnidad Científica de Excelencia UCE-PP2016-05European Commission, H2020 Programme, Marie Skłodowska-Curie Action European Training network – Innovative Training Network (ETN-ITN), SUBlime (grant agreement # 955986)Funding for open access charge: Universidad de Granada/CBU

Silica-Functionalized Nanolimes for the Conservation of Stone Heritage

The relatively recent development of nanolimes (i.e., alcoholic dispersions of Ca(OH)2 nanoparticles) has paved the way for new approaches to the conservation of important art works. Despite their many benefits, nanolimes have shown limited reactivity, back-migration, poor penetration, and lack of proper bonding to silicate substrates. In this work a novel solvothermal synthesis process is presented by which extremely reactive nanostructured Ca(OH)2 particles are obtained using calcium ethoxide as the main precursor species. Moreover, it is demonstrated that this material can be easily functionalized with silica-gel derivatives under mild synthesis conditions, thereby preventing particle growth, increasing total specific surface area, enhancing reactivity, modifying colloidal behavior, and functioning as self-integrated coupling agents. Additionally, the formation of calcium silicate hydrate (CSH) nanocement is promoted by the presence of water, resulting in optimal bonding when applied to silicate substrates, as evidenced by the higher reinforcement effect produced on treated Prague sandstone specimens as compared to those consolidated with nonfunctionalized commercial nanolime. The functionalization of nanolimes is not only a promising strategy for the design of optimized consolidation treatments for the cultural heritage, but may also have important implications for the development of advanced nanomaterials for building, environmental, or biomedical applications

Unveiling the secret of ancient Maya masons: Biomimetic lime plasters with plant extracts

Ancient Maya produced some of the most durable lime plasters on Earth, yet how this was achieved remains a secret. Here, we show that ancient Maya plasters from Copan (Honduras) include organics and have a calcite cement with meso-to-nanostructural features matching those of calcite biominerals (e.g., shells). To test the hypothesis that the organics could play a similar toughening role as (bio)macromolecules in calcium carbonate biominerals, we prepared plaster replicas adding polysaccharide-rich bark extracts from Copan’s local trees following an ancient Maya building tradition. We show that the replicas display similar features as the organicscontaining ancient Maya plasters and demonstrate that, as in biominerals, in both cases, their calcite cement includes inter- and intracrystalline organics that impart a marked plastic behavior and enhanced toughness while increasing weathering resistance. Apparently, the lime technology developed by ancient Maya, and likely other ancient civilizations that used natural organic additives to prepare lime plasters, fortuitously exploited a biomimetic route for improving carbonate binders performanceSantander Program for the Research and Conservation of Maya Sculpture, at the David Rockefeller Center for Latin American Studies(DRCLAS), Harvard UniversitySpanish Government RTI2018-099565-B-I00 PID2021.125305NBMCIN/AEIERDF Away of making EuropeJunta de AndaluciaUniversity of GranadaUnidad Cientifica de Excelencia UCE PP2016-05Horizon 2020Marie Sklodowska-Curie Action European Training network-Innovative Training Network (ETN-ITN), SUBlime 95598

Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation

We acknowledge funding by the Santander Program for the Research and Conservation of Maya Sculpture, at the David Rockefeller Center for Latin American Studies (DRCLAS), Harvard University; the Spanish Government grant RTI2018-099565-B-I00, the Junta de Andalucia research groups RNM-179 and BIO 103, and the University of Granada, Unidad Cientifica de Excelencia UCE-PP2016-05. We thank the Instituto Hondureno de Antropologia e Historia (IHAH) and the local Santander team at the Maya Sculpture Conservation Laboratory (LACEM) in Copan including Hector Eliud Guerra, Karina Garcia, Adelso Canan, Rufino Membreno, Luis Reina, and Isuara Nereyda Alonso for their help and continuous support, as well as for providing access to this Maya archaeological site and their contribution to the documentation, sampling, and treatment application process. We also thank architectural conservator Laura Lacombe for sampling support, Fulvio di Lorenzo for his help with Rietveld analysis of XRD results, George W. Scherer for his insightful comments on clay swelling damage, and the personnel of the Centro de Instrumentacion Cientifica (CIC) of the University of Granada for their help with TG/DSC, XRD, FRX, mu-CT, FESEM and TEM analyses. We also thank Aurelia Ibanez Velasco for her help with the expansion tests, as well as with the porosity and water absorption analyses, and Jean Battini from Micromeritics France S.A.R.L., for the MIP analyses.Much stone sculptural and architectural heritage is crumbling, especially in intense tropical environments. This is exemplified by significant losses on carvings made of tuff stone at the Classic Maya site of Copan. Here we demonstrate that Copan stone primarily decays due to stress generated by humidity-related clay swelling resulting in spalling and material loss, a damaging process that appears to be facilitated by the microbial bioweathering of the tuff stone minerals (particularly feldspars). Such a weathering process is not prevented by traditional polymer- and alkoxysilane-based consolidants applied in the past. As an alternative to such unsuccessful conservation treatments, we prove the effectiveness of a bioconservation treatment based on the application of a sterile nutritional solution that selectively activates the stone ' s indigenous bacteria able to produce CaCO3 biocement. The treatment generates a bond with the original matrix to significantly strengthen areas of loss, while unexpectedly, bacterial exopolymeric substances (EPS) impart hydrophobicity and reduce clay swelling. This environmentally-friendly bioconservation treatment is able to effectively and safely preserve fragile stones in tropical conditions, opening the possibility for its widespread application in the Maya area, and elsewhere.Santander Program for the Research and Conservation of Maya Sculpture, at the David Rockefeller Center for Latin American Studies (DRCLAS), Harvard UniversitySpanish Government European Commission RTI2018-099565-B-I00Junta de Andalucia RNM-179- BIO 103University of Granada, Unidad Cientifica de Excelencia UCE-PP2016-0

Damage of porous building stone by sodium carbonate crystallization and the effect of crystallization modifiers

Salt crystallization is an aggressive weathering mechanism affecting porous building materials. The extensive use of Portland cement, a source of alkalis, in modern buildings and restoration interventions makes sodium carbonate salts important weathering agents. Herein, we study salt damage to a porous stone commonly used in the Andalusian built heritage (Santa Pudia limestone) due to stress generation associated with the precipitation of natron (Na2CO3⋅10 H2O). We performed cyclic crystallization tests combined with thermodynamic and poromechanical calculations to determine salt crystallization pressure and effective tensile stress suffered by the material. The outcome reveals that in-pore natron crystallization during cooling/evaporation generates stresses exceeding the tensile strength of the wet substrate, leading to extensive damage by fracturing and material loss. Damage is reduced using aminotris(methylenephosphonic) acid (ATMP), a common phosphonate-based crystallization modifier that induces non-damaging efflorescence growth as opposed to damaging subflorescence growth, which takes place in its absence.Campus of International Excellence in Heritage, PatrimoniUN10 (project CEI14-PATRIM-1)Junta de Andalucía (Research Group RNM-179 and project P20_00675)University of Granada, UGR (Research Excellence Unit UCEPP2016-05 "Carbonates")Spanish Ministry of Science and Innovation through the research project PID2021-125305NB-I0

Application limits of Q-Switched Nd: YAG laser irradiation for stone cleaning based on colour measurements

The application limits of the laser-cleaning technique for different types of building stones have been investigated by measuring colour variations. The selected stones differ in their chemical and mineralogical composition, colour, texture and crystallinity degree. The experimentation was carried out with a Q-switched Nd:YAG laser. The colour variations on stones associated with different operative fluences were measured using a colorimeter. Further, surface morphological changes were examined under SEM. From the calculation of colour differences, a damage threshold fluence was established for each stone type. The response of the stones to laser radiation at a particular fluence was found to be mainly conditioned by their chemical and mineralogical composition and, to a less extent, by their textural characteristics

Changes in traditional building materials: the case of gypsum in Northern Spain

The rural and monumental architecture of Northern Spain gives testimony of the wide-ranging constructive possibilities of traditional gypsum for exterior and structural applications. However, today, gypsum is only used for finishing purposes. By combining a bibliographic review with local visits/interviews and experimental gypsum calcinations, we were able to document traditional processing methods and analyze the factors responsible for the decline of exterior and structural gypsum use. Obtained results are also valid for other European countries and contribute to a better understanding of the technical peculiarities of traditional gypsum, hopefully reviving traditional processing techniques to produce compatible and sustainable conservation materials

Portraits of women in selected novels by Virginia Woolf and E. M. Forster

Female characters in novels by Virginia Woolf and E.M. Forster are studied in their relationships as wives, mothers, daughters and prospective brides. The novels selected are those where the writers are concerned with families dominated by Victorian ideals. Virginia Woolf: The Voyage Out (1915), Night and Bay (1919), Mrs Dalloway (1925), To the Lighthouse (1927). E.M. Forster: Where Angels Fear to Tread (1905), The Longest Journey (1907) , A Room with a View (1908), Howards End (1910).The socioeconomic, religious and ideological origins of the Victorian ideals are traced, esp. as they are related to the writers' family background in the tradition of English intellectual life. The central theme of the four novels by Woolf is the mother-daughter relationship which is analyzed in its components of love and resentment, often revealed in an interior monoloque. Forster's novels usually present a widowed mother with a daughter and a son. It is shown how the plot, dialogue and authorial intrusions are used to depict a liberation from the constraints of the Victorian ideals of family life. The mothers in the novels of both writers are shown to be representative of various aspects of the Victorian ideal of womanhood. The attitudes of men towards women vary from those typifying Victorian conceptions of male superiority to more modern ideals of equality and natural companionship.digitalisering@um