Combination of polymeric superplasticizers, water repellents and pozzolanic agents to improve air lime-based grouts for historic masonry repair

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

Lime-based rendering mortars with photocatalytic and hydrophobic agents: assessment of the water repellency and biocide effect

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. Good compatibility between the water repellent agent, the pozzolanic additive and some of the polycarboxylate superplasticizers was observed. The presence of the photocatalyst was found to be very effective in preventing microbiological colonization

Combination of polymeric superplasticizers, water repellents and pozzolanic agents to improve air lime-based grouts for historic masonry repair

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

Improvement of the depolluting and self-cleaning abilities of air lime mortars with dispersing admixtures

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 self-cleaning ability, studied through dye degradation, of the mortars with SPs was also enhanced around 1.2 times. Three of the polycarboxylate-based superplasticizers enhanced the photosensitization of the dye under visible light irradiation, resulting in faster decolouring kinetics. In connection with the self-cleaning performance, these same SPs preserved the photoinduced hydrophilicity of the lime mortars, reaching good wettability of the surface of the mortars (water contact angles of ca. 10º), even in the presence of the sodium oleate, proving the compatible characteristics of the admixtures and allowing obtaining a new range of actively depolluting lime mortars

Improvement of the depolluting and self-cleaning abilities of air lime mortars with dispersing admixtures

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 self-cleaning ability, studied through dye degradation, of the mortars with SPs was also enhanced around 1.2 times. Three of the polycarboxylate-based superplasticizers enhanced the photosensitization of the dye under visible light irradiation, resulting in faster decolouring kinetics. In connection with the self-cleaning performance, these same SPs preserved the photoinduced hydrophilicity of the lime mortars, reaching good wettability of the surface of the mortars (water contact angles of ca. 10º), even in the presence of the sodium oleate, proving the compatible characteristics of the admixtures and allowing obtaining a new range of actively depolluting lime mortars

Lime-based rendering mortars with photocatalytic and hydrophobic agents: assessment of the water repellency and biocide effect

Different rendering mortars were prepared by mixing air lime and air lime-pozzolanic nanosilica with TiO2 and sodium oleate as photocatalytic and water repellent agents, respectively, 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 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. 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 colony 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. Good compatibility between the water repellent agent, the pozzolanic additive and some of the polycarboxylate superplasticizers was observed. The presence of the photocatalyst was found to be very effective in preventing microbiological colonization

Development of multifunctional coatings for protecting stones and lime mortars of the Architectural Heritage

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

Development of multifunctional coatings for protecting stones and lime mortars of the Architectural Heritage

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