Search Results (16)

This paper presents the development of two solutions for sandwich panels composed of a thin-layer alkali-activated composite (AAc) layer and a thicker insulation layer, formed by extruded polystyrene foam or expanded cork agglomerate (panels named AP_XPS or AP_ICB, respectively). The AAc combined ceramic waste from clay bricks and roof tiles (75%) with ladle furnace slag (25%), activated with sodium silicate. The AAc layer was further reinforced with polyacrylonitrile (PAN) fibers (1% content). The mechanical behavior was assessed by measuring the uniaxial compressive strength of cubic AAc specimens, shear bond strength, pull-off strength between the AAc layer and the insulation material, and the flexural behavior of the sandwich panels. The thermal performance was characterized by heat flux, inner surface temperatures, the thermal transmission coefficient, thermal resistance, and thermal conductivity. Mechanical test results indicated clear differences between the two proposed solutions. Although AP_XPS panels exhibited higher tensile bond strength values, the AP_ICB panels demonstrated superior interlayer bond performance. Similar findings were observed for the shear bond strength, where the irregular surface of the ICB positively influenced the adhesion to the AAc layer. In terms of flexural behavior, after the initial peak load, the AP_XPS exhibited a deflection-hardening response, achieving greater load-bearing capacity and energy absorption capacity compared to the AP_ICB. Finally, thermal resistance values of 1.02 m² °C/W and 1.14 m² °C/W for AP_ICB and AP_XPS were estimated, respectively, showing promising results in comparison to currently available building materials. Full article

Toxic cyanobacterial blooms are a growing environmental problem, persisting in freshwater bodies globally, and potentially hazardous to populations that rely on surface freshwater supplies. Nature-based solution units (NBSUs) are effective and sustainable approaches for water treatment, with sorption being an important process. The purpose of this study was to evaluate unmodified agro-based waste materials (rice husks, olive pulp pomace pellets (OP), cork granules) and the benchmark NBSU substrates (biochar, light expanded clay aggregate (LECA), and sand) for their microcystin-LR (MC-LR) and cylindrospermopsin (CYN) sorption potential. The kinetics and sorption mechanism of the two best sorbent materials were studied for future incorporation into NBSUs. Pre-screening of the sorbents showed highest sorption with biochar (>86% MC-LR and >98% CYN) and LECA (78% MC-LR and 80% CYN) and lower sorption with rice husk (<10%), cork (<10%), and sand (<26%). Leaching from OP made them unsuitable for further use. The sorption of both the cyanotoxins onto biochar was rapid (8 h), whereas onto LECA it was steadier (requiring 48 h for equilibrium). The pseudo-second-order kinetic model fit the sorption of both cyanotoxins onto biochar and LECA (R²: 0.94–0.99), suggesting that the sorption rate is limited by chemisorption. The sorption of MC-LR and CYN to biochar and LECA fit the Freundlich and D–R models better, suggesting multilayer sorption, high heterogeneity, and porosity in the sorbents (which was also confirmed by SEM/EDS). The sorption capacity was observed to be higher for biochar (K_f: MC-LR = 0.05, CYN = 0.16) than LECA (K_f: MC-LR = 0.02, CYN = 0.01). Full article

The cork oak (Quercus suber L.) woodlands, known as montados in Portugal, hold significant economic, cultural, social, and environmental value. They are found in the Mediterranean Sea basin, particularly in the Iberian Peninsula, and sustain various activities like silvopastoralism, with cork being a primary product. Despite its economic significance, challenges such as climate change threaten its sustainability. This study aimed to analyze the edaphoclimatic variables affecting cork yield, thickness, price, and gross income in the Alentejo region of Portugal. A total of 35 farmers were selected for the data collection included in this study. Multivariable linear regressions were performed to establish relationships between cork yield, thickness, price, and gross income as dependent variables, various edaphoclimatic factors, and tree densities. A higher tree density correlates with an increased cork yield but a decreased cork thickness. Soil pH affects cork yield and thickness, with a lower pH favoring higher cork yields but thinner cork. A higher clay and silt content in horizon soil C enhances cork thickness and raises the price but reduces the cork yield. Higher accumulated precipitation and temperatures contribute to higher yields and thicknesses of cork. It is concluded that the relationships between the dependent and the independent variables are complex but partially explainable. Understanding these relationships is paramount to ensure sustainable management practices are adopted that are capable of addressing issues raised in the current context of climate change. Full article

The European Climate Law mandates a 55% reduction in CO₂ emissions by 2030, intending to achieve climate neutrality by 2050. To meet these targets, there is a strong focus on reducing energy consumption in buildings, particularly for heating and cooling, which are the primary drivers of energy use and greenhouse gas emissions. As a result, the demand for energy-efficient and sustainable buildings is increasing, and thermal insulation plays a crucial role in minimizing energy consumption for both winter heating and summer cooling. This review explores the historical development of thermal insulation materials, beginning with natural options such as straw, wool, and clay, progressing to materials like cork, asbestos, and mineral wool, and culminating in synthetic insulators such as fiberglass and polystyrene. The review also examines innovative materials like polyurethane foam, vacuum insulation panels, and cement foams enhanced with phase change materials. Additionally, it highlights the renewed interest in environmentally friendly materials like cellulose, hemp, and sheep wool. The current challenges in developing sustainable, high-performance building solutions are discussed, including the implementation of the 6R principles for insulating materials. Finally, the review not only traces the historical evolution of insulation materials but also provides various classifications and summarizes emerging aspects in the field. Full article

Reducing energy consumption in the building sector has driven the search for more sustainable construction methods. This study explores the potential of cork-modified mortars reinforced with basalt fabric, focusing on optimizing both mechanical and hygroscopic properties. Six mortar mixtures were produced using a breathable structural mortar made from pure natural hydraulic lime, incorporating varying percentages (0–3%) of cork granules (Quercus suber) as lightweight aggregates. Micro-computed tomography was first used to assess the homogeneity of the mixtures, followed by flow tests to evaluate workability. The mixtures were then tested for water absorption, compressive strength, and adhesion to tuff and clay brick surfaces. Adhesion was measured through pull-off tests, to evaluate internal bonding strength. Additionally, this study examined the relationship between surface roughness and bond strength in FRLM composites, revealing that rougher surfaces significantly improved adhesion to clay and tuff bricks. These findings suggest that cork-reinforced mortars offer promising potential for sustainable construction, achieving improved hygroscopic performance, sufficient mechanical strength, internal bonding, and optimized surface adhesion. Full article

This study explores the potential of natural and recycled materials to enhance the fire behavior of eco-friendly intumescent coatings, compared to a traditional ammonium polyphosphate (APP)-based one. To achieve this, cork, halloysite clay, and recycled glass were evaluated as natural fillers and sustainable components within the coating formulation. The aim was to reduce the reliance on synthetic materials and minimize the environmental impact while maintaining fire performance. Fire exposure tests were conducted to assess the in situ char formation and its relationship to the heat source and char foaming process. The results highlighted that all functionalized coatings exhibited suitable intumescent behavior. The best results were evidenced by cork-filled coating that evidenced an intumescent capacity about 40% higher than the traditional ammonium polyphosphate (APP)-based one. This provided valuable insights into the coating’s real-time response to fire, determining its suitability for various fire-resistant applications. Full article

The world is currently grappling with the two critical issues of global warming and climate change, which are primarily caused by the emission of greenhouse gases. The construction industry and buildings significantly contribute to these emissions, accounting for roughly 40% of the total greenhouse gas emissions. In response to this pressing issue, environmental organizations and governments have pushed the construction industry to adopt environmentally friendly practices to reduce their carbon footprint. This has led to a greater emphasis on designing and planning sustainable buildings that are in line with the principles of sustainable development. Hence, it is imperative to evaluate buildings in terms of their greenhouse gas emissions and explore ways to reduce them. This research examines the impact of material selection on the carbon footprint of reinforced concrete buildings, aiming to reduce embodied carbon. For this purpose, two reinforced concrete buildings are designed for their embodied carbon to quantify their environmental impact. The first building employs commonly used materials such as ceramics, clay bricks, stone, and plaster. In contrast, the second building incorporates sustainable materials such as cork, plywood, and rockwool. According to the findings, using sustainable materials in the second building leads to a 41.0% reduction in the carbon footprint of the construction process. Additionally, using sustainable materials can mitigate pollution levels in the three categories of endangerment to human health, ecosystem pollution, and resource consumption by 31.4%, 23.7%, and 33.3%, respectively. Full article

The effect of the addition of Fe⁰ and Fe³⁺ on the formation of expanded clay aggregates was studied using iron-free kaolin as an aluminosilicates source. Likewise, the incorporation of cork powder as a source of organic carbon and Na₂CO₃ as a flux in the mixtures was investigated in order to assess its effect in combination with the iron phases. An experimental protocol, statistically supported by a mixture experiments/design of experiments approach, was applied to model and optimize the bloating index, density, absorption capacity, and mechanical strength. The process of expansion and pore generation and the associated decrease in density required the addition of iron, such that the optimum mixtures of these properties presented between 25 and 40 wt.% of Fe⁰ or Fe³⁺, as well as the incorporation of 3.5–5 wt.% of organic carbon. The addition of Fe³⁺ produced a greater volumetric expansion (max. 53%) than Fe⁰ (max. 8%), suggesting that the formation of the FeO leading to this phenomenon would require reducing and oxidizing conditions in the former and the latter, respectively. The experimental and model-estimated results are in good agreement, especially in the aggregates containing Fe⁰. This reinforces the application of statistical methods for future investigations. Full article

The water ingress plays an important role in building materials’ degradation. The use of lightweight aggregates is interesting in terms of sustainability, because they reduce the density of cement-based materials, among other advantages. The development and use of new lightweight aggregates, such as cork granulates, is a current research topic. In the present work, water ingress performance of sustainable mortars which combined expanded and natural cork aggregates and cements with slag, fly ash and limestone has been studied. Mortars produced with sand and expanded clay were also prepared. Bulk density, water absorption, drying capacity and gel and capillary pores were studied. Tests were carried out at 28 days and 1 year. A good behavior has been generally observed when an addition was incorporated to the binder, especially slag or fly ash. Regarding the new non-standardized lightweight cork aggregates, mortars with natural cork showed lower water absorption and lower volume of permeable pore space in the long term than mortars with expanded cork. At one year, natural cork mortars had an adequate water absorption performance compared to those with expanded clay, which may be due to the high volume of small capillary pores (100 nm–1 µm) in natural cork mortars. Full article

The use of lightweight aggregates in construction materials is a good solution for increasing the contribution to sustainability of civil engineering works, such as maritime ones. In this regard, the possibility of using cork granulates and expanded clay is a current research topic. The combination of eco-friendly cements with lightweight aggregates could provide solutions for developing new building materials. In this work, it has been studied mortars prepared with sustainable cements and the lightweight aggregates of natural cork and expanded clay. These cements incorporated slag, limestone and fly ash. Reference mortars with only sand as aggregate were also made. The total porosity and pore size distributions were obtained. The non-steady-state chloride migration coefficient and compressive and flexural strengths were also determined. The tests were performed at 28 days and 1 year. The differences in the total porosity between the natural cork and expanded clay series were not high, depending on the binder. Natural cork mortars showed similar or slightly higher migration coefficients than the reference and expanded clay mortars at 1 year. This adequate chloride resistance and the low mechanical strengths observed for the natural cork mortars recommend the possible use of this new aggregate in non-structural cement-based materials for civil engineering works exposed to maritime environments. Full article

This study aimed to investigate the possibility of recycling cork scraps derived from the production of agglomerated bottle caps containing organic additives (glues and adhesives) in addition to virgin wood. The study involved pyrolysis treatment followed by the use of char to obtain lightweight material prototypes. The scrap was pyrolysed in order to achieve the thermal degradation of unwanted molecules with decomposition temperatures lower than the pyrolysis temperatures, but also to achieve the reduction in mass and size of the starting material. The substitution of 15% by weight of weight-lightening agent (char from pyrolysed cork, or half char and half spent coffee grounds) into the clayey matrix made it possible to obtain lightweight aggregates with pH and conductivity values that could be exploited in an agronomic context. The substitution of clay with of 5 to 15% by weight of pyrolysed cork char in the production of specimens pressed at 25 bar and fired slowly at 1000 °C led to lightweight ceramics with particularly interesting porosity (from 41 to 68%) and bulk density (850–1600 kg/m³) values. Full article

Climate change and resource and energy depletion are already impacting ecosystems and societies around the world. As a result, environmental sustainability has become one of humanity’s priority challenges. This study aims to use ecological multilayer material in order to reduce the impact of carbon and energy needs of heating in severe climates in which people die each year from cold. The combination of the investigated multilayer material gives a low thermal transmittance (U = 0.361 W·m⁻²·K⁻¹). A simulation using the software TRNSYS was established to estimate the yearly heating and cooling needs in the building with the developed multilayer material in a semi-arid climate. The yearly energy demands for heating and cooling were compared to a normal wall with conventional bricks; 47% of energy was saved by the use of the multilayer material wall. The use of the multilayer material permits a low ratio of energy needs of 24 KWh/m²/year for cooling needs and 43 KWh/m²/year for heating. Full article

The application of Life Cycle Assessment in the construction sector can be a very useful tool to reduce the environmental impact generated by the sector. In order to quantify the improvement in environmental terms with the use of artificial lightweight aggregates (LWA) manufactured with waste, in this work, we conducted a comparative evaluation of the life cycle of LWAs for a total of five different scenarios: LWAs obtained in a traditional way, i.e., using exclusively clay in their manufacture (Spanish blond clay, Portuguese red clay and Portuguese blond clay), and LWAs manufactured with four different wastes, with a partial substitution of 2.5% for each of the clays per waste (almond and hazelnut shells, sludge from the purification of paper money, cork dust and coffee grounds). The functional unit was set as the production of 1 kilo of lightweight aggregates and the CML 2000 methodology and the SimaPro software were used. The results obtained in this research allow us to conclude that the addition of organic wastes showed a slightly higher environmental performance than the conventional system, the ALAs manufactured with almond and hazelnut shells being the most environmentally friendly option, with reductions of more than 30% in some cases, followed by the LWAs manufactured with coffee grounds. On the other hand, the addition of paper sewage sludge and cork dust represents minimal environmental optimization. Full article

Thermal mortars incorporating insulating aggregates are a possible solution to ensure good thermal performance and thermal comfort in buildings due to their low thermal conductivity coefficient. Under some circumstances, namely for particular in-service conditions in industrial applications and/or accidental actions (such as fire), it is important to quantify the retention of their properties after exposure to elevated temperatures, however this information is not yet available in the literature. This study aims to characterize the physical and mechanical behavior of thermal mortars incorporating expanded clay, granulated expanded cork and silica aerogel as aggregates after exposure to elevated temperatures. To this end, five types of mortars were produced in laboratory conditions—three thermal mortars, one reference sand mortar and one sand mortar with admixtures—and then exposed to different elevated temperatures (from 20 °C to 250 °C) in a thermal chamber. After thermal exposure, the following properties were assessed: bulk density; ultrasonic pulse velocity; dynamic elasticity modulus; dynamic shear modulus; Poisson coefficient; compressive strength; and thermal conductivity. The results obtained show that residual properties present a very high dependence on the reactions that take place in the cement paste when the mortars are exposed to elevated temperatures. After such exposure, all mortars with thermal insulating aggregates were able to maintain their insulating characteristics, but experienced internal damage and degradation of their mechanical properties. Results obtained also showed that insulating aggregates allowed to produce mortars with higher aggregate-cement paste compatibility at elevated temperatures compared to conventional mortars, resulting in less micro-cracking of the mortar, and leading to lower reductions in thermal conductivity with increasing temperature. Full article

The paper deals with the use of vibro-compressed units with bio-natural components on construction. The proposed mix design of vibrated blocks consist of cork granules and/or hemp shives, with the aim to substitute polymeric elements or expanded clay, together with the use of natural hydraulic lime (NHL) as binder. An experimental campaign is presented, with mechanical tests to evaluate the influence of each component on flexural and compression behavior. The proposal is also investigated from a productive point of view, considering how it can be harmonized in the productive process of lightweight aggregate concrete units without modifications in the productive process. The tested elements could perform a certain reduction of the carbon impact, maintaining interesting mechanical properties. The application of the proposed units in several contexts, as separating elements joined with structural components, is considered to improve rehabilitation or to obtain higher performances in buildings. Full article