Natural Cement in Portugal: Context in Cement Production and Architectural Use

Natural cement, also known as “Roman cement”, was used across Europe during a historic period, mainly in many building facades, due to its hydraulic properties and aesthetic qualities. In Portugal, the use of natural cement occurred in buildings from the second half of the 19th century to the beginning of the 20th century, a period during which the use of lime binders decreased and before the massive use of Portland cement. Recent conservation and rehabilitation actions resulting from necessary interventions in heritage buildings from this period have played an important role in revealing evidence of the use of natural cement and clarifying the lacunae of information about this material. Due to the inadequate use of reparation materials in previous conservation and rehabilitation interventions, this study summarizes the historical production, study, and use of natural cement in Portugal. Natural cement results from the calcination of clay-rich limestone (marlstone) without any compositional changes after extraction, distinguishing itself from hydraulic lime due to its higher clay content and allowing for the formation of higher quantities of hydraulic reactive phases without free lime. Although this topic has been approached at a European level, mainly focusing on the production and use of natural cement in Central Europe, in Portugal, it is still necessary to produce and disseminate information on this specific subject. Therefore, this study focuses on the evolution of cement production in Portugal and an analysis of the existing knowledge of the binders used in architectural heritage based on the scientific and historical bibliography

Mortars for Conservation of Late 19th and Early 20th Century Buildings—Combination of Natural Cements with Air Lime

With the availability of commercial Natural cements (NC) for the conservation purposes raises a fundamental question about the compatibility between historic and repair mortars. The properties of Natural cements are dependent on the geological location of the raw material extraction and also on the production parameters, both having an impact on the final properties of the mortars produced from each distinct. Therefore, the significance of preservation of 19th and 20th century heritage and selection of the proper binder compatible with the original materials necessitate the study of existing NCs, that nowadays are produced by several manufacturers. This work provides a complex study of the mortars prepared from three NCs available in the market: Groupe Prompt Vicat, France (NCPV); Cemento Collet Marfil (NCM) and Cemento Natural Tigre (NCT), both from Spain. Various mortar sets based on individual NC containing different binder/aggregate ratios and air lime additions were analyzed after 28, 60, and 90 days of curing with the focus on their mineralogical composition (XRD), morphology (SEM), mechanical (flexural and compressive strength), and physical properties such as water absorption by capillarity, water vapor permeability, and water vapor diffusion resistance. Mortars prepared from NCPV, NCM, and NCT show distinct physical-mechanical properties with varying binder/aggregate ratio and air lime addition. This study shows that the NC variability should be taken into consideration when selecting materials for the conservation and rehabilitation of historic renders and plasters. Based on the comparison with original NC mortars, several NC mortars developed in this study show adequate properties for conservation of the buildings from late 19th and early 20th century in terms of compressive strength (>12 MPa), water absorption by capillarity (−2·h−0.5), water vapor permeability (−10 kg·s−1·m−1·Pa−1), and water vapor diffusion resistance (<28) values

Recovery of Fatty Acids from Mineralogic Mars Analogs by TMAH Thermochemolysis for the Sample Analysis at Mars Wet Chemistry Experiment on the Curiosity Rover

International audienceThe Mars Curiosity rover carries a diverse instrument payload to characterize habitable environments in thesedimentary layers of Aeolis Mons. One of these instruments is Sample Analysis at Mars (SAM), whichcontains a mass spectrometer that is capable of detecting organic compounds via pyrolysis gas chromatographymass spectrometry (py-GC-MS). To identify polar organic molecules, the SAM instrument carries the ther-mochemolysis reagent tetramethylammonium hydroxide (TMAH) in methanol (hereafter referred to as TMAH).TMAH can liberate fatty acids bound in macromolecules or chemically bound monomers associated withmineral phases and make these organics detectable via gas chromatography mass spectrometry (GC-MS) bymethylation. Fatty acids, a type of carboxylic acid that contains a carboxyl functional group, are of particularinterest given their presence in both biotic and abiotic materials. This work represents the first analyses of asuite of Mars-analog samples using the TMAH experiment under select SAM-like conditions. Samples analyzedinclude iron oxyhydroxides and iron oxyhydroxysulfates, a mixture of iron oxides/oxyhydroxides and clays,iron sulfide, siliceous sinter, carbonates, and shale. The TMAH experiments produced detectable signals underSAM-like pyrolysis conditions when organics were present either at high concentrations or in geologicallymodern systems. Although only a few analog samples exhibited a high abundance and variety of fatty acidmethyl esters (FAMEs), FAMEs were detected in the majority of analog samples tested. When utilized, the TMAH thermochemolysis experiment on SAM could be an opportunity to detect organic molecules bound inmacromolecules on Mars. The detection of a FAME profile is of great astrobiological interest, as it couldprovide information regarding the source of martian organic material detected by SA