http://repositorio.lnec.pt:8080/jspui/handle/123456789/329 Sat, 04 Apr 2026 20:59:30 GMT 2026-04-04T20:59:30Z http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018373 Novel nanomaterials with high solar reflectance for energy efficient envelope systems. Veloso, A. Exposure to weathering conditions requires selecting and applying solutions with appropriate durability to preserve façades without the need for frequent extensive rehabilitation actions. The consequent heat gain from solar radiation exposure accelerates the degradation of the most exposed façade layer, reducing their service life. An attractive solution to mitigate this overheating is the incorporation of functional nanomaterials in the façades finishing coatings, which reflect a part of the solar radiation in the near-infrared region. This solution may have an even higher influence on dark-coloured coatings, whose use has been increasing by architects and final consumers. To design more energy-efficient buildings, applying thermal insulation systems, such as External Thermal Insulation Composite Systems (ETICS), is necessary. These systems experience significant surface temperature fluctuations (amplified by the dark colour application), causing dimensional variations and naturally leading to cracking. Therefore, this Doctoral Thesis proposes a strategy combining these two façade solutions: dark-coloured finishing coatings applied on ETICS, aiming to improve solar reflectance and reduce the surface temperature. The study focused on developing new dark-coloured formulations with reflective nanomaterials, without excessively changing the visual aesthetics. A systematic study of their intrinsic properties was performed to understand and predict the nanomaterials' behaviour and ability to reflect or absorb. Subsequently, a commercial TiO2 Rutile and a newly developed nanocomposite, combining two nanomaterials, were included in a dark-coloured commercial finishing coating for ETICS and the surface properties were evaluated. The thermo-optical properties revealed an overall total reflectance increase for the two samples (15% and 20%) compared to only 12% of the non-modified finishing coating, providing a similar visual aesthetic. The reflectance improvement observed with the incorporation of nanomaterials certainly impacted the surface temperature, as the modified finishing coatings showed better performance and durability, as evidenced in the accelerated ageing test as thermal oscillations responsible for fractures are reduced. From these results, this strategy could emerge as a promising solution for low-cost dark reflective coatings that can be easily applied on building façades Mon, 01 Jan 2024 00:00:00 GMT http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018373 2024-01-01T00:00:00Z http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018186 Eco-efficient Plasters for Increased Indoor Air Quality and Comfort Ranesi, A. Indoor walls and ceilings are often coated with plasters. Due to the large surface in contact with indoor air, the plasters can passively contribute to moisture regulation and pollutant removal. The work presented intends to better understand this contribution, while enhancing, when possible, the plasters formulations for the purpose. The first step was to analyze the hygroscopic response of traditional and modern binder-based plasters. To do so, a first study was run to quantify the relative humidity fluctuations indoor. Then, the methods fitting the most the real indoor microclimates were selected for testing. The campaign was run along with bibliographic research, to match laboratory results with those ones present in literature. The compatibility with the preexisting materials and products and the eco-efficiency of the plasters are two parameters that were kept in mind during the work. According to that, clay and gypsum based plastering mortars were selected as the most promising materials. Both, in fact, are present in traditional architecture, besides being suitable solutions for new construction, and have low embodied energy. However, while the clay-based plasters showed a high hygroscopic behavior, the gypsum-based ones showed a lower one. For this reason, the latter was modified through the addition of biomass and the clay-based plasters were kept as a benchmark along the study. The plant selected for the scope is Acacia dealbata, an invasive species that plays a role in the spread of wood fires in Portugal. The biowaste addition was aimed at enhancing the moisture buffering of gypsum-based plasters without jeopardizing other properties or their carbon footprint. Good results were obtained, increasing the moisture buffering ability of the gypsum plaster up to double, even if still lower than the clay-based ones. The ozone reactivity and primary and secondary emission rates (VOCs) of the innovative gypsum-based plaster and the clay-based ones were also analyzed. The ozone removal ability of the gypsum-based plaster was improved by the biomass addition, the primary emissions increased a little, but the secondary ones were very low. Clay-based plasters overall confirmed their low emissions and ozone removal activity. Mon, 01 Jan 2024 00:00:00 GMT http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018186 2024-01-01T00:00:00Z http://repositorio.lnec.pt:8080/jspui/handle/123456789/1017382 Avaliação da eficiência de tintas térmicas em períodos de arrefecimento em edifícios Chiraze Assane M. A presente dissertação teve como objetivo avaliar, por meio de abordagem experimental, o desempenho térmico de tintas térmicas em comparação a tinta convencional, quando aplicadas nas superfícies interiores e exteriores de paredes no período de arrefecimento. Após prospeção e recolha junto de empresas em Portugal, foram caracterizadas três tintas térmicas brancas e um primário térmico, comparativamente a uma tinta convencional branca. Inicial-mente onze provetes revestidos com as tintas e os sistemas em estudo foram submetidos a ensaio laboratorial para avaliação da refletância. As tintas térmicas estudadas são caracteriza-das por apresentarem alta refletância à radiação solar, quando comparadas às tintas brancas convencionais disponíveis no mercado nacional. Aplicaram-se os sistemas de pintura no revestimento interior das parede oeste e norte de uma célula experimental localizada no Laboratório Nacional de Engenharia Civil (LNEC), e monitorizou-se na estação de arrefecimento a temperatura superficial através de termopares instalados nas paredes. Foram aplicadas as mesmas tintas em estudo na fachada exterior sul da mesma célula experimental, para avaliar o desempenho térmico através de termografia de infravermelhos na mesma estação. Os resultados obtidos na avaliação do desempenho térmico das tintas no interior da célula experimental demonstram que as tintas térmicas não apresentam vantagens significativas em comparação com a tinta convencional. Entretanto, quando aplicadas na superfície exterior sul da célula e expostas à radiação solar incidente, as tintas térmicas revelaram desempenho térmico superior comparativamente à tinta convencional, na estação de arrefecimento. Wed, 01 Nov 2023 00:00:00 GMT http://repositorio.lnec.pt:8080/jspui/handle/123456789/1017382 2023-11-01T00:00:00Z http://repositorio.lnec.pt:8080/jspui/handle/123456789/1014701 The influence of natural aggregates on the performance of replacement mortars for ancient buildings: the effects of mineralogy, grading and shape Lopes dos Santos, A. R. The importance of the selection of the type of aggregates and their effects on the modification of mortar properties is widely recognized. However, despite recent scientific advances on the effect of aggregates on the properties of mortars and concretes, few studies show how the characteristics of aggregates affect the microstructure and consequently, the final quality of mortars. Moreover, in general, existing studies show that there is an approach mostly related to the use of Portland cement, which several researchers have already shown that have adverse effects, when it is used in rehabilitation works of ancient buildings. In the context of rehabilitation, this factor is particularly relevant, since the main objective is to obtain mortars with specific characteristics and performances compatible with those that exist in old masonry. The aggregate, as an integral part of mortars, and in some cases defined as their "skeleton", has a direct influence on the microstructure of mortars, which, in turn, influences the physical, chemical and mechanical properties, as well as the finishing and the final appearance of the renders, especially in the case of lime mortars. Therefore, the present study intends to contribute to a better knowledge of the influence of mineralogical and physical characteristics (grain size distribution and shape) of the natural aggregates on the mortars’ pore structure and, consequently, on their physical-mechanical behaviour and their durability, in particular for the rehabilitation of old buildings. This knowledge will allow, in a substantiated way, optimizing the various parameters and defining repair solutions for different fields of application. To achieve these goals, an extensive laboratory characterization methodology was developed: parameters like the workability and water retentivity of fresh mortars; mechanical strength, adhesion to the substrate and hygric properties of hardened mortars; as well as the performance of the mortars subjected to salt crystallization and freeze/thaw cycles, were used. Furthermore, a chemical, mineralogical and microstructural characterization was also performed in order to relate the physical and mechanical results with the microstructural changes, namely concerning dimensions and volume of pores, during the carbonation and/or hydration processes. The results show that the aggregates characteristics have a relevant influence on the microstructure of mortars, namely in air lime mortars. However, different ranges of pores influence different properties of mortars, regardless the type of binder or aggregate used in their composition. Generally, a reduction in macroporosity leads to higher mechanical strength, namely compressive strength. However, the reduction in the diameter of the macropores can lead to an increase of capillary porosity and microporosity, which tends to compromise the durability. Wed, 26 Jun 2019 00:00:00 GMT http://repositorio.lnec.pt:8080/jspui/handle/123456789/1014701 2019-06-26T00:00:00Z