On the Use of Sodium Chloride and Calcined Diatomite Sludge as Additives to Improve the Engineering Properties of Bricks Made with a Clay Earth from Jun (Granada, Spain)

Solid bricks manufactured out of clayey earth from a quarry near the city of Granada (Spain) were studied and compared with others to which two additives were added during the kneading of the raw material: Calcined diatomite sludge and sodium chloride. Samples with and without additives were fired at 800ºC, 950ºC, and 1100ºC. New mineral phases were formed in the bricks after firing. These included gehlenite, diopside, and plagioclase, which is gradually enriched in calcium, and microcline, which is transformed into sanidine. Mullite and molysite also appeared in the bricks made with added salt. Porosity increased substantially in the bricks that contained diatomite sludge, while the addition of sodium chloride accelerated the mineralogical transformations and caused sintering at relatively low temperatures of 800ºC. The bricks became more compact and less anisotropic as the firing temperature increased. This behaviour was less evident in the bricks with added diatomite sludge, which alters the orientation of the phyllosilicates. The bricks fired at 1100º C had the best physical parameters. However, the bricks with added sodium chloride fired at 800º C reached hygric and compactness values that were at least similar to bricks from the other groups fired at 950º C.This study was funded by Junta de Andalucía Research Group RNM179, by Research Project MAT2016-75889-R and by the Eureka SD project (agreement number 2013-2591), which is supported by the Erasmus Mundus programme of the European Union

Consolidation with ethyl silicate: how the amount of product alters the physical properties of the bricks and affects their durability

We evaluated the consolidating capacity of ethyl silicate in three types of bricks fired at 800, 950 and 1100 °C. We chose two concentrations of product, at 25% and 50%, diluting the product in white spirit to estimate whether greater dilution enables the product to penetrate deeper into the bricks, or whether a higher concentration leads to better consolidation of bricks. The application of ethyl silicate caused bricks porosity to decline and their compactness to increase. These changes were more accentuated as the concentration of the product increased. The pore size distribution not changed substantially except that there were fewer of the smallest pores. The color and the lightness of the pieces changed after application of the consolidant, albeit slightly. The durability of bricks improved as manifested by the results of the salt crystallization test. In general, the longest-lasting pieces were those treated with 25% ethyl silicate.Se ha evaluado la capacidad consolidante del silicato de etilo en tres tipos de ladrillos cocidos a 800, 950 y 1100 °C. Se eligieron dos concentraciones de producto, al 25% y 50%, diluyéndolo en white spirit para estimar si más dilución favorece una penetración más en profundidad del producto o si una mayor concentración produce una mejor consolidación de los ladrillos. El silicato de etilo ha causado una disminución de la porosidad y un aumento de la compacidad de los ladrillos, acentuándose estas modificaciones con mayor concentración de producto. La distribución porométrica no ha cambiado de forma sustancial, disminuyendo los poros más pequeños. Color y luminosidad de las piezas han modificado ligeramente tras la aplicación del consolidante. Los ladrillos consolidados han mejorado su durabilidad frente al envejecimiento acelerado producido por las sales. En general, las piezas más duraderas han resultado ser las tratadas con el 25% de silicato de etilo.This study was financially supported by Research Group RNM179 of the Junta de Andalucía and by Research Project MAT2016-75889-R

The protection of marble surfaces: the challenge to develop suitable nanostructured treatments

Marbles have been extensively used in historical architecture owing to their good mineralogical and microstructural properties, durability, and aesthetic quality. Nevertheless, the protection of historical marbles in outdoor conditions is a difficult task, mainly because of their low open porosity. An overview of nanostructured protective treatments based on the use of SiO2, TiO2, ZnO, and Ag nanoparticles to confer superhydrophobic, self-cleaning, and antifouling properties to the surface is proposed. Particular attention is devoted to the development of photocatalytic nano-TiO2-based treatments. In this regard, advantages, drawbacks, and critical issues in the use of nanocomposites are covered. Recent advances using modified innovative TiO2 nanoparticles, in dispersion and as nanocomposites, are reported. Nanocomposites based on suitable TiO2 nanoparticles seem very promising, and a comparison of the results obtained in controlled lab conditions and on real deteriorated surfaces is also presented