Key Engineering Materials Vol. 634

Abstract: In a society with a high growth rate and increased standards of comfort arises the need to minimize the currently high energy consumption by taking advantage of renewable energy sources. The mortars with incorporation of phase change materials (PCM) have the ability to regulate the temperature inside buildings, contributing to the thermal comfort and reduction of the use of heating and cooling equipment, using only the energy supplied by the sun. This paper aims to contribute to the study of mortars incorporating PCM. The main characteristics of the material and the mortars doped with PCM, will be presented. It also aims to clarify the differences in the physical and mechanical characteristics of mortars doped with different types of PCM.

Abstract: High reflective paints (cool paints) can reduce solar heat gains, improving thermal comfort and energy efficiency in buildings in summer period. To evaluate the thermal performance of different reflective paints applied in façades (over ETICS like solution) a research study is being developed at LNEC using full-scale test cells built in LNEC’s campus.For this purpose, non-destructive infrared thermography method is being used. This method allows knowing the temperature distribution on façades by measuring infrared radiation emitted from its surfaces. Thermocouples placed on wall outside surfaces support thermographic diagnosis.Optical properties of cool paints (reflectance and emittance) used in this research study were achieved by additional laboratory tests.Comparative analysis between thermal performance of a white cool paint and a white conventional paint is presented in this paper. This research study also shows the potential of infrared thermography in the assessment of thermal performance of cool paints.

Abstract: In a society with a high growth rate and increased standards of comfort arises the need to minimize the currently high energy consumption by taking advantage of renewable energy sources. The mortars with incorporation of phase change materials (PCM) have the ability to regulate the temperature inside buildings, contributing to the thermal comfort and reduction of the use of heating and cooling equipment, using only the energy supplied by the sun. However, the incorporation of phase change materials in mortars modifies its characteristics. The main purpose of this study was the production and characterization in the fresh and hardened state of mortars with incorporation of different contents of PCM in mortars based in different binders. The binders studied were aerial lime, hydraulic lime, gypsum and cement. For each type of binder, different mortars were developed with different content of PCM. The proportion of PCM studied was 0%, 20%, 40% and 60% of the mass of the sand. It was possible to observe that the incorporation of PCM in mortars caused differences in properties such as workability, microstructure, compressive strength, flexural strength and adhesion.

Abstract: The industry of construction is responsible for the high consumption of raw materials, energy and waste production. As such, it becomes imperative to develop and study new constructive solutions with greater sustainable value. The mortars with incorporation of phase change materials (PCM) have the ability to regulate the temperature inside buildings, contributing to the thermal comfort and reducing the use of heating and cooling equipment, using only the energy supplied by the sun. However, the incorporation of phase change materials in mortars modifies its characteristics. The main focus of this study was the durability of mortars with PCM incorporation based in different binders. The binders studied were aerial lime, hydraulic lime, gypsum and cement. For each type of binder, different mortars were developed with different content of PCM. The proportion of PCM studied was 0% and 40% of the mass of the sand. It was possible to observe that the incorporation of PCM in mortars caused differences in properties such as water absorption by capillarity, water absorption by immersion and degradation after freeze-thaw cycles.

Abstract: The incorporation of lightweight aggregates in cement-based coating mortars contributes to a better performance of some of their physical properties, influencing their hygrothermal behaviour. This paper analyses the effect of some lightweight aggregates (expanded clay, granulated cork and silica aerogel) on the following mortars’ characteristics: porosity, bulk density, capillary water absorption coefficient, drying index and water vapour permeability. The experimental results showed that low percentages of incorporation of lightweight aggregates led to more porous mortars with lower bulk density, higher capillary water absorption coefficient and greater drying facility, relative to the reference cement-based mortar. The incorporation of silica aerogel in cement-based mortars resulted in major differences in terms of water resistance, with significant benefits in terms of the drying process due to their porous structure.

Abstract: Flat roofs are particularly unfavourable to the thermal performance of single family houses and apartments of the the upper floor of multifamily buildings. Often these housing typologies are too hot during summer, when incident solar radiation affects the roof more than any other element of the building envelope.Recent developments have given rise to many high reflectance products. However, thermal performance of these products has not yet been thoroughly quantified, when applied to flat roofs under real weather conditions. Performance assessment of innovative solutions must consist in the evaluation under real exposure conditions and analytical modelling.Two full-scale experimental cells under weathering conditions, located in Laboratório Nacional de Engenharia Civil (LNEC) campus, were used in this study. The experimental cells have identical dimensions, constructive characteristics and thermal behaviour.Initially, the two cells (C5 and C6) presented the same APP modified bitumen waterproofing solution, finished on the top layer with natural slate granules (XN). Subsequently, simulating a rehabilitation intervention, it was introduced in C5 an improved reflectance APP modified bitumen membrane surfaced with thermally coloured white slate granules (XB).After a coexistence period of solutions XB (C5) and XN (C6), it was applied over C6 XN a high reflectance white paint (XN/PB).The characterization of the thermal performance under real weather of each tested solution was based on the analysis of the values of the following parameters recorded under free-floating operation and controlled regime: temperature of the flat roof’s upper and lower surfaces, indoor temperature and electric consumption under controlled regime.

Abstract: The developed system corresponds to multifunctional prefabricated modular elements that combine an insulation layer with a cast coating material for exterior that can imitate stone or concrete. These systems need auxiliary elements of fixing to connect them mechanically to the structural wall of the building, in order to ensure its stability, using anchorage, profiles, rails, among others. The use of these systems connected to the coating interrupts the continuity of thermal insulation, causing additional heat losses through linear and point thermal bridges, having an detrimental effect on thermal performance of the system. The development of fixing of present multifunctional panels was based on the evaluation and adoption of appropriate solutions in order to minimize thermal bridges and reinforce the stability of the panel. For evaluation purposes some models are evaluated, with different connecting systems, configurations and different materials such as aluminium, stainless steel, galvanized steel and Glass Fibre Reinforced Polymer (GFRP) profiles. The quantification of thermal bridges, for evaluation of thermal performance, has been made using computing programs, HEAT2 and HEAT3. The evaluation of a system developed in this research work, i.e. incorporating profiles in thermal insulation, shows a good thermal resistance contributing significantly to the thermal insulation and energy conservation in building.

Abstract: Production of active rice husk silica (ARHS) in bubbling fluidized bed boiler of a thermoelectric unit (TEU) and its addition to high performance concrete (HPC) with a compression resistance of 90 MPa was developed in the last 10 years. A first factory in Brazil was established at Alegrete town, RS, and other factories are under planning. Data of ARHS production, specification and HPC trace are presented. Design of parabolic solar collector coverage (PSCC) for air heating for biomass drying in a special silo of the TEU is presented as well. Cost of HPC/ARHS is 10 times less than steel (USD 200/ton vs. USD 2000/ton, specific mass 2.5 vs. 7.6 g/cm³, respectively). Those characteristics allow simultaneous solution of four ecological problems: large span coverage, rain water collection, daily solar energy collection and storage, and drying of biomass. The integration of those characteristics results in decrease of biomass consumption maintaining the same UTE efficiency. Tracking parabolic solar collector can be avoided between Cancer and Capricorn Tropics, and it is sufficient its eastern-western orientation with inclination to the Equator by the latitude angle. Coverage of the area occupied by TEU is sufficient to dry its biomass consumption. Preheating of boiler water with solar energy is possible decreasing biomass consumption in sunny days; biomass is partially consummed at night and cloudy days. Coupling the above technologies with high pressure steam TEU and fast-growing short-rotation forest gives to the biomass electrical energy generation a competitive economical position with hydraulic, coal, natural gas, and aeolic energy generation.

Abstract: The world’s demand for construction aggregates has been increasing over the last years, mainly due to the rapid economic growth of countries such as Brazil, China and India. Naturally, this growth stimulates the development of construction and demolition activities, thereby generating increasing amounts of waste. This paper presents a state-of-the-art review of the experimental research on the effect of incorporating aggregates of different types and shapes, sourced from construction and demolition waste. This review also covers studies on the incorporation of waste materials coming from industrial activities, emphasising those performed in the Instituto Superior Técnico, of the University of Lisbon, Portugal.