The aim of this study is to develop new air lime mortars with enhanced photocatalytic depolluting and self-cleaning abilities. Nanosilica, as pozzolanic mineral admixture, was used to improve the strength of mortars, whereas nanotitania (TiO2) was added to impart photocatalytic properties. At the same time, five different dispersing admixtures -superplasticizers- were added in bulk to the mortars to enhance the photocatalytic activity by reducing the rate of charge carrier recombination. Four polycarboxylate-based derivatives and a polynaphthalene sulfonate were tested aiming to achieve an efficient charge separation. In order to increase the lasting of the mortars subjected to water movements, sodium oleate was also added as a water repellent agent. Since the photoinduced hydrophilicity, responsible for the self-cleaning effect, might be affected by the water repellent, the compatibility between this admixture and the photocatalytic performance of the nanotitania was also investigated. Results showed that photocatalytic activity was improved due to the action of the superplasticizers as indicated by an average 33% increase of NO degradation, which is significant to the depolluting activity of these mortars. Furthermore, these mortars also showed a greatly reduced release of intermediate toxic compounds, mainly NO2: the selectivity factor (NOx/NO) reached values up to 87%.

The present work presents focuses on the use of different admixtures for the development of rendering lime-based mortars with improved adhesion and durability, as well as reduction of cracking. To this aim, combinations of an adhesion improver (ethylene-vinyl acetate copolymer, EVA), a water repellent agent (sodium oleate), a viscosity enhancer (a starch derivative) and a mineral admixture (pozzolanic addition of nanosilica or metakaolin) were tested. The renders were applied on four different substrates (sandstone, limestone, granite and brick) to assess their performance. The influence of the admixtures¿ combination on fluidity, stiffening time, adhesion, cracking, compressive strength, pore structure, frost resistance and durability against magnesium sulfate attack was evaluated. The EVA admixture was seen to enhance the adhesion when used in combination with oleate, metakaolin and starch. This combination also led to a minimized cracking. Opposite trends between adhesion and cracking were observed as a function of the porosity of the substrates and of the presence of small-sized capillary pores. The interferences with the carbonation accounted for the drops observed in compressive strength for the nanosilica-free tested renders; nanosilica-containing renders showed good compressive performance, due to the filling effect of the admixture and to the C-S-H formation.

This paper presents the experimental procedure to develop air lime-based injection grouts including polymeric superplasticizers, a water repellent agent and pozzolanic agents as additives. Research focuses on the development of grouts to improve various characteristics simultaneously combining different additions and admixtures. Aiming to improve the injectability of the grouts, in this study different polymeric superplasticizers were added, namely polycarboxylated-ether derivative (PCE), polynaphthalene sulfonate (PNS) and condensate of melamine-formaldehyde sulfonate (SMFC). Sodium oleate was also used as a water repellent agent to reduce the water absorption. The enhancement of the strength and setting time was intended by using microsilica and metakaolin as pozzolanic mineral additions. Compatibility between the different admixtures and action mechanism of the different polymers were studied by means of zeta potential and adsorption isotherms measurements. Diverse grout mixtures were produced and investigated assessing their injectability, fluidity, stability, compressive strength, hydrophobicity and durability. This research leads to several suitable mixtures produced by using more than one component to enhance efficiency and to provide better performance of grouts. According to the results, the grout composed of air lime, metakaolin, sodium oleate and PCE was found the most effective composition improving the mechanical strength, injectability and hydrophobicity.

Unique multifunctional coatings, comprising a 3D superhydrophobic agent and two nanostructured photocatalysts (solar-light sensitive 50/50 and 10/90 TiO2-ZnO nano-heterostructures), compatible with the inorganic substrates of the Built Heritage, have been designed. The synthesized nanoparticles showed an enhanced photocatalytic activity (tested by NO degradation) as compared with the raw TiO2 and ZnO materials. Dispersing agents were used to optimize the coatings, avoiding agglomeration of the photocatalytic nanoparticles and increasing the stability of the suspensions. Four distinct dispersions were optimized and applied as coatings onto stony materials used in the Built Heritage, such as sandstone, lime mortar, granite and limestone. Their effectiveness was assessed by assessing hydrophobicity of the surfaces (static water contact angle), photocatalytic activity and self-cleaning as well as water vapour permeability of the treated specimens. These transparent coatings demonstrated high compatibility with the construction materials of the Architectural Heritage and showed a synergistic effect rendering a minimized water absorption, self-cleaning ability evidenced by the reduced adsorption of soiling deposits and a reasonable degradation of any trace that might be adsorbed, as well as a protecting hydrophobic environment for the photocatalyst.

A new range of grouts prepared by air lime and metakaolin (MK) as a pozzolanic admixture has been obtained by using as dispersing agents two polymers, namely poly-naphthalene sulfonate (PNS) and lignosulfonate (LS), with the aim of improving the fluidity of the fresh grouts. Fluidity and setting times of the grouts were assessed. Differences in the molecular architecture and in the anionic charge density explained the different adsorption of the polymers and the different performance. The higher anionic charge of PNS and its linear shape explained its better adsorption and effectiveness. The pozzolanic reaction was favoured in grouts with PNS, achieving the highest values of compressive strength (4.8 MPa after 182 curing days). The addition of PNS on lime grouts slightly decreased the frost resistance of the grouts (from 24 freeze-thaw cycles for the polymer-free samples to 19 or 20 cycles with 0.5 or 1 wt % of PNS). After the magnesium sulphate attack, grouts were altered by decalcification of hydrated phases and by formation of hexahydrite and gypsum. A protective role of portlandite against magnesium sulphate attack was clearly identified. Accordingly, the polymer LS, which preserves a significant amount of Ca(OH)2, could be an alternative for the obtaining of grouts requiring high sulphate attack resistance.

Active coatings to be applied onto hardened surfaces of lime rendering and masonry mortars and stones of the Built Heritage were developed. Nano-heterostructures of TiO2/ZnO (50:50 and 10:90) were obtained by Flame Spray Pyrolysis as photocatalytic agents with expanded sensitivity towards solar light, instead of the restricted UV dependence of the pure TiO2 or ZnO. A superhydrophobic medium was simultaneously prepared and photocatalytic nanoparticles were added to obtain the coatings. The active products were expected to prevent the water absorption of the substrates and the subsequent degradation effects as well as to allow the stones and mortars to act as self-cleaning materials, reducing the dirt deposition and the biological colonization. Dispersions were applied onto the surface of lime mortars and siliceous stone. Measurements of the photocatalytic oxidation activity of the coatings were carried out by means of the NO degradation, showing a very good efficiency of the nanoparticles even at long term tests (values of NO oxidation of ca. 35%). Water contact angle assessment evidenced a strong hydrophobization of the treated surfaces, with WCA values higher than 140º. The results proved the synergistic effect of these coatings with respect to the durability of the treated substrates, giving rise to a promising way of preventive conservation for building materials of the Cultural Heritage.

This work reports the obtaining of lime-based grouts as repairing materials. Microsilica was added as pozzolanic additive to enhance the compressive strength of the hardened grouts. Sodium oleate, as water repellent admixture, and different superplasticizers (SPs) were also incorporated to reduce the water absorption and to enhance the injectability of the grouts. Polycarboxylate ether (PCE), polynaphthalene sulfonate (PNS), melamine sulfonate (MMS) and polyacrylic acid (PA) were tested as SPs. Regarding the fluidity of the grouts, PCE was seen to improve the injectability, followed by PNS, MMS and PA. However, PCE addition was also accompanied by a severe delay in the setting time. The other three superplasticizers did not provoke significant delays in the hardening of the samples. The water contact angle underwent an increase pointing to an effective hydrophobization of the surface as a consequence of the water repellent admixture. The combination with PCE was the most effective in keeping the water repellency in comparison with the control sample (lime grout + oleate). MMS yielded high compressive strengths and durability of the mortars, in the face of freezing-thawing cycles, was enhanced.

Different rendering mortars were prepared by mixing air lime and air lime-pozzolanic nanosilica with TiO2 and sodium oleate as, respectively, photocatalytic and water repellent agents, added in bulk. The aim of the work was to design and obtain new rendering mortars with improved durability focusing in the reduction of the water absorption of these materials and in their self-cleaning and biocide effect. To achieve a better distribution of the TiO2 particles, which was expected to enhance their efficiency, different dispersing agents were also incorporated to the fresh mixtures. Four diverse polycarboxylate ethers superplasticizers and a poly-naphthalene-sulfonate were tested. Workability and fluidity of the fresh rendering mortars were determined to guarantee the applicability of the final products. Water contact angle was monitored with the aim of assessing the hydrophobicity of the mortars lent by the water repeller. The biocide effect was studied by means of the culture of a strain of Pseudomonas fluorescens. The colonization of the mortars¿ surface was analyzed by determining the number of colonies forming units (CFU) after several days subjecting the samples to suitable T and RH conditions. At the same time, the surface of the mortars was irradiated with solar light to activate the photocatalyst. Results showed the efficiency of the sodium oleate in reducing the water uptake of the rendering mortars.

El presente trabajo tiene como principal objetivo estudiar las interacciones que se producen cuando se adicionan separadamente dos superplastificantes (PNS ¿sulfonato de polinaftaleno- y LS ¿lignosulfonato-) a un conglomerante aéreo (cal aérea Cl 90-S) y a uno hidráulico formado por cal aérea a la que se le ha añadido metacaolín como material puzolánico, y los efectos que dichas adiciones tienen en las propiedades de los sistemas. Para la fabricación de los morteros, se empleó árido calcáreo. Adicionalmente, se efectuaron ensayos de durabilidad en morteros con la composición citada, sometiéndolos a ciclos de hielo-deshielo y a ataque con sulfatos. Aunque se realizaron algunas medidas con las pastas en estado fresco, la mayoría de los experimentos (resistencia a compresión y a flexión, TG-ATD, DRX, FTIR-ATR, porosimetría de intrusión de mercurio) se realizaron tras períodos de fraguado del mortero de 7, 28, 91, 182 y 365 días. Se detectaron fases silicatadas y silicoaluminatadas en los morteros estudiados, a pesar de que las experiencias se realizaron a temperatura ambiente y con un bajo porcentaje de material puzolánico (¿20 %). La presencia de LS impidió el proceso de carbonatación, lo que a su vez provocó un decrecimiento en los valores de resistencia mecánica cuando se trataba de morteros hidráulicos. Se observó asimismo una mayor porosidad y un mayor tamaño medio de poro en el caso de sistemas con LS. La durabilidad (ciclos hielo-deshielo) de los morteros mejoró notable

Los morteros de relleno o inyección, especialmente destinados a reparación de cavidades y defectos de albañilería, deben fluir adecuadamente en estado fresco y combinar resistencia y durabilidad. Para conseguir algunas de estas características pueden utilizarse aditivos químicos: superplastificantes, para mejorar la fluidez; adiciones puzolánicas, para conseguir resistencias adecuadas en ambientes con limitado acceso de CO2 y una mejora de la durabilidad; e hidrofugantes, de manera que, sin perjudicar la permeabilidad de estos materiales al vapor de agua, se evite la penetración de agua por capilaridad mejorando la durabilidad. Sin embargo, en la mayor parte de los casos, toda la información disponible se circunscribe al efecto de un único aditivo, sin contemplar el posible efecto conjunto o incluso sinérgico de las combinaciones más interesantes de dos o más aditivos y/o adiciones puzolánicas. El estudio de las sinergias entre estos componentes ofrece posibilidades muy interesantes de avance científico-técnico. Precisamente este es el objetivo del trabajo: diseño de nuevos morteros de inyección de cal que puedan ser utilizados para la restauración del Patrimonio Edificado mediante combinación adecuada de aditivos superplastificantes (éteres de policarboxilato, condensados de naftaleno-formaldehído, sulfonato de melamina y ácido poliacrílico), hidrofugante (oleato sódico) y adiciones minerales puzolánicas (microsílice y metacaolín).