Application of Silica-Aerogel-Fibre-Based Thermal Renders for Retrofits in Building Walls: A Comparative Assessment with Benchmark Solutions.

The current climate change context raises the demand for reducing energy and environmental impacts while keeping an economic balance and building users' comfort. Thermal insulation solutions are potential allies in ensuring the adequacy of existing buildings for challenging sustainability requirements. In this scenario, silica-aerogel-fibre-based thermal renders are innovative solutions for which integrated approaches still lack information, and they should be compared with benchmark multilayer solutions, such as those based on expanded polystyrene (EPS), extruded polystyrene (XPS), mineral wool (MW), and insulated corkboard (ICB), to evidence their prospective economic, environmental, and energy benefits. This paper quantifies the optimum insulation thicknesses, life cycle savings, payback periods, and environmental impacts of innovative thermal renders compared to conventional thermal insulation materials when applied as a retrofit in existing facade walls. The results show that cost-optimised thermal renders with sisal fibres led to the best overall performance. Higher heating needs led to higher optimum render thicknesses and life cycle savings. With a 0.02 m thickness, aerogel-fibre-based thermal renders outperformed other materials in terms of heating-degree days (HDD) from 1000 °C·day onwards; they can save approximately EUR 60∙m-2, 1000 MJ∙m-2, and 100 kg CO2 eq∙m-2 while presenting a U-value 13% lower throughout their 30-year lifetime when compared with the second-best multilayer solution with XPS.

Integrated Performance Evaluation of Aerogel-Based Fibre-Enhanced Thermal Renders Applied on Building Walls.

In this work, aerogel renders were enhanced with fibres for use in new building walls, emphasising a Mediterranean climate. The main novelty of the study relies on an integrated evaluation of the aerogel-based fibre-enhanced thermal renders from environmental, energy and economic approaches. Therefore, optimum insulation thicknesses, life cycle savings, payback periods, abiotic depletion potential from fossil fuels (ADP-ff) and global warming potential (GWP) impacts were quantified as a function of the energy consumption. The cost optimisation of aerogel-based renders enabled a reduction from 2477.4 to 1021.7 EUR∙m-3 for the reference formulation, and the sisal-optimised render led to the best-integrated performance. A higher DD* (degree-days equivalent) led to higher optimum thicknesses (the Azores required 0.02 m and 0.01 m and Bragança 0.06 m and 0.03 m for cost-optimised and non-optimised thermal renders with sisal fibre, respectively). The optimum thickness related to the ADP-ff and GWP impacts was higher, 0.04 m for the Azores and 0.09 m for Bragança. A steeper decrease in the annual energy consumption occurred for thermal renders up to 0.02 m in the Azores and 0.04 m in Bragança. Aerogel-based fibre-enhanced thermal renders had benefits, mainly from 600 DD* onwards.

Effectiveness and durability of anti-graffiti products applied on ETICS: towards a compatible and sustainable graffiti removal protocol.

External Thermal Insulation Composite Systems (ETICS) are widely used constructive solutions which aim at enhancing the building thermal performance. Nevertheless, ETICS can often present anomalies (e.g., stains and microcracks) throughout their service life, and vandalism actions, as in the case of graffiti, are rather common in urban areas. The removal of undesired graffiti is generally carried out through invasive chemical-mechanical methods, which may affect the durability of the ETICS. The adoption of anti-graffiti products can be a feasible protection method; however, no comprehensive studies were already addressed on these substrates. This study aims at evaluating the effectiveness, compatibility, and durability of three anti-graffiti products (with permanent, semi-permanent, and sacrificial properties) when applied on different ETICS. The removal of aerosol graffiti paints was carried out with a low-invasive and eco-friendly removal method (i.e., low-pressure steam jet). The water transport properties, as well as color, gloss, and roughness, were evaluated before and after graffiti removal. The durability of the anti-graffiti was also assessed by artificial aging cycles. Results showed that graffiti removal was rather efficient on ETICS with acrylic-based finishing coats and when using (semi) permanent anti-graffiti products (with ΔE*ab < 5, i.e., not macroscopically visible, when comparing cleaned and reference surfaces), although these products can reduce their effectiveness after aging. Conversely, unsatisfactory graffiti cleaning was observed on ETICS with lime-based or silicate-based finishing coats (with ΔE*ab > 5), with considerable alteration also of the water transport properties (reducing water absorption and slowing down the drying kinetic).

X-ray microtomography applied to mortars: Review of microstructural visualization and parameterization.

The objective of the present work is to review the main applications of X-ray microtomography in the microstructural study of mortars, based on a literature search related to the subject, and to enable the development of more innovative and sustainable mortar formulations. This three-dimensional non-destructive microscopy allows qualitative visualization down to micrometric scales, visualization of the spatial distribution of the interior of samples of objects relatively opaque to visible light and the measurement of quantitative microstructural parameters. Furthermore, the combination of X-ray microtomography with other microstructural and compositional techniques can result in data at different scales of observation. Particularly, in the study of mortars, there are benefits in using this technique to better characterize materials in terms of the spatial structure of pores and other voids, aiding in the formulation of new mortars and in the characterization of mortar behavior, for example, after leaching and carbonation processes. This paper intends to contribute to the discussion of the potentials and drawbacks of this advanced technique, allowing a better characterization of mortars and enabling the development of more innovative and sustainable formulations.

Durability of a New Thermal Aerogel-Based Rendering System under Distinct Accelerated Aging Conditions.

The widespread application of innovative thermal enhanced façade solutions requires an adequate durability evaluation. The present work intends to assess the durability of a new aerogel cement-based rendering system through the adaptation of different accelerated aging cycles, such as heating-freezing, freeze-thawing, and heat-cold. Several mechanical properties and also capillary and liquid water absorptions were tested for uncoated and coated specimens. A decrease in the mechanical strength, especially after freeze-thaw cycles, was observed. However, the water action promoted the late hydration of the cement paste contributing to the densification of the matrix and, consequently, the increase of the adhesive strength. Additionally, a decrease in the dynamic modulus of elasticity and an increase in the Poisson's ratio were observed after aging, which indicates a higher capacity of the render to adapt to substrate movements, contributing to a reduction of cracking.

Durability of Thermal Renders with Lightweight and Thermal Insulating Aggregates: Regranulated Expanded Cork, Silica Aerogel and Expanded Polystyrene.

Following the trend of energy-efficient construction, renders with thermal insulation properties have been studied for replacing conventional renders. However, there are still few studies on the durability of these renders that may become a barrier for their implementation. In this study, the performance of lightweight renders for thermal insulation to accelerated aging cycles and freeze/thaw cycles is discussed. For this purpose, renders with regranulated expanded cork (GEC), silica aerogel (SA), and expanded polystyrene (EPS) were produced and tested for compressive strength, ultra-sound velocity, Young's modulus, and thermal conductivity before and after accelerated aging cycles (hygrothermal, IR and freeze/thaw cycles). With this study, a comparison between the influence of different aggregates on renders is carried out in order to understand their effect on different properties of renders.

Evaluation of side effects of mechanical cleaning with an anionic detergent on granite cladding tiles.

One of the aims of Goal 11 of the UN's 2030 Agenda for Sustainable Development is to make human settlements sustainable. Some effort should therefore focus on developing maintenance strategies for buildings. Polished granite cladding tiles are very popular for use as flooring material in private and public buildings. These tiles are often treated by mechanical cleaning with detergents and scrubbers, and anionic detergents without chelating agents are usually used to prevent damaging the material. In this study, the anionic detergent Teepol® was applied to granite tiles in order to determine the effect of the treatment on the surface properties of this stone, i.e. appearance, colour, gloss, roughness and hydrophobicity. The results obtained were explained by scanning electron microscopy observations, which enabled characterisation of the microtexture of the surfaces, chemical contamination and any damage to the different granite-forming minerals. The results were compared with those obtained for tiles cleaned by the same mechanical procedure but with tap water in place of detergent and for tiles treated by immersion in water without any mechanical action. In summary, the properties evaluated were affected by the extraction of the typical oxyhydroxylated iron forms that fill cracks in the granite and by the formation of new cracks due to the mechanical action. Moreover, colour changes and the chemical contamination (C-rich deposits with Na, S, Cl, Ca and Mg) hindered the effectiveness of the cleaning procedure.

Use of Polycarbonate Waste as Aggregate in Recycled Gypsum Plasters.

The use of gypsum as an indoor coating material for buildings is very extensive. This means that huge amounts of gypsum waste are generated daily worldwide. Therefore, many researchers in the last years have been working on the generation of new gypsum-related materials and products that incorporate recycled gypsum waste as a replacement for the commercial one. On the other hand, trying to reduce the large amounts of plastic generated globally each year, several studies have used different types of plastic waste as aggregates for the development of new construction and building materials. However, up to now, no previous studies have been found in which any type of plastic waste has been used as an aggregate in a recycled gypsum matrix. This paper presents a study in which two different types of waste were mixed for the development of new gypsum plasters: unheated gypsum waste from industrial plasterboard production (GPW) and polycarbonate (PC) waste from rejected compact discs (CDs) and digital versatile discs (DVDs). In this sense, the mechanical and thermal performance of plasters was evaluated. Finally, in order to evaluate the changes in the microstructure of the composites, a scanning electron microscopy (SEM) analysis was conducted. The results showed a good performance of the new composites when both types of waste were combined in the mixes. New lightweight eco-efficient plasters, completely recycled, with enhanced flexural strength (by 14.8%), compressive strength (by 26.8%), and thermal conductivity (42.8% less), compared to the reference material, were achieved.

Methodology for the Assessment of the Ecotoxicological Potential of Construction Materials.

Innovation in construction materials (CM) implies changing their composition by incorporating raw materials, usually non-traditional ones, which confer the desired characteristics. However, this practice may have unknown risks. This paper discusses the ecotoxicological potential associated with raw and construction materials, and proposes and applies a methodology for the assessment of their ecotoxicological potential. This methodology is based on existing laws, such as Regulation (European Commission) No. 1907/2006 (REACH-Registration, Evaluation, Authorization and Restriction of Chemicals) and Regulation (European Commission) No. 1272/2008 (CLP-Classification, Labelling and Packaging). Its application and validation showed that raw material without clear evidence of ecotoxicological potential, but with some ability to release chemicals, can lead to the formulation of a CM with a slightly lower hazardousness in terms of chemical characterization despite a slightly higher ecotoxicological potential than the raw materials. The proposed methodology can be a useful tool for the development and manufacturing of products and the design choice of the most appropriate CM, aiming at the reduction of their environmental impact and contributing to construction sustainability.

Parametric Analysis to Study the Influence of Aerogel-Based Renders' Components on Thermal and Mechanical Performance.

Statistical models using multiple linear regression are some of the most widely used methods to study the influence of independent variables in a given phenomenon. This study's objective is to understand the influence of the various components of aerogel-based renders on their thermal and mechanical performance, namely cement (three types), fly ash, aerial lime, silica sand, expanded clay, type of aerogel, expanded cork granules, expanded perlite, air entrainers, resins (two types), and rheological agent. The statistical analysis was performed using SPSS (Statistical Package for Social Sciences), based on 85 mortar mixes produced in the laboratory and on their values of thermal conductivity and compressive strength obtained using tests in small-scale samples. The results showed that aerial lime assumes the main role in improving the thermal conductivity of the mortars. Aerogel type, fly ash, expanded perlite and air entrainers are also relevant components for a good thermal conductivity. Expanded clay can improve the mechanical behavior and aerogel has the opposite effect.