Débora Macanjo Ferreira

The utilization of wood and wood derivatives are growing in building construction, mainly due to sustainability and circularity reasons, despite the inherent flammability of wood. Woodworking often requires bonding elements with adhesives, which are prone to degradation under fire. A potential solution to improve the fire resistance of wood joints and their derivatives involves incorporating fire retardants into the adhesive compositions. This study explores the adhesion properties of bonded joints of medium-density fibreboard and pinewood panels using resins based on urea and polyurethanes derived from diphenylmethane diisocyanate (MDI). Various proportions of ammonium polyphosphate, borax, and expandable graphite were incorporated as fire retardants. Shear testing was conducted on lap joints under both room and elevated temperatures to evaluate their adhesive performance. At room temperature and 100°C, the predominant failure mode was panel tear failure, while at higher temperatures, cohesive failure became more prevalent. The results indicated a reduction in bonding strength and displacement with increasing temperature. In particular, the MDI-based resin demonstrated higher shear resistance at elevated temperatures in comparison to the urea-based resin. The addition of fire retardants, particularly ammonium polyphosphate, improved the shear strength of MDI joints at 100°C and 200°C. Furthermore, the determined shear modulus per meter evaluated the decreasing rigidity of the bonding joint with increasing temperature. In the reference case of urea without fire retardants, the rigidity of the bond decreased by approximately 100% at 200°C compared to room temperature. In contrast, the MDI cases with ammonium polyphosphate and borax experienced a more moderate decrease of around 60% at 230°C, indicating improved thermal stability.

This study uses waste materials, specifically diatomaceous earth (DE) that is rich in aluminum and silica, as a sustainable source for aluminosilicate precursors in geopolymers to replace conventional cement in mortar applications. While the use of DE shows promising results, it lacks sufficient alumina content, thereby demanding the introduction of alumina powder. However, the effectiveness of this addition is limited, as unreacted alumina particles were observed in the X-ray diffraction and SEM analyses. This could potentially impact various geopolymer properties due to the incomplete achievement of the desired silicon/aluminum (Si/Al) ratio. Achieving the appropriate Si/Al balance remains crucial for geopolymers to realize their potential as environmentally friendly alternatives to Portland cement.

The main goal of this study is to assess the behaviour of soil–cement blocks with incorporation of organic wastes. The problem of waste accumulation exists worldwide and has become a concern in today’s society, leading to enormous environmental damage. One of the possibilities for reducing their environmental impact is the reuse of these wastes in new materials. However, incorporating waste changes the mechanical, physical and thermal properties of the new material. In order to evaluate the potential use of waste in blocks composition, laboratory tests were conducted and the results were analysed. This article presents the fire behaviour of ecological soil–cement blocks with waste incorporation. Therefore, an experimental programme was performed using samples of wall panel with soil–cement blocks. The wall specimen under fire conditions was also analysed by a non-linear transient finite element numerical model, in time and temperature domains, and the numerical and experimental temperature fields were compared.

A research work focused on studying earth render for tabique application purposes is presented. Initially, a brief description of the tabique building technique is provided. The relevance of the application of this traditional building technique is also highlighted. Different compositions of earth render are experimentally analyzed and the respective performance is evaluated. Flexural and compressive strengths, workability, drying shrinkage cracking, and water resistance are the material properties assessed. A simple earth render is selected as being adequate for tabique building applications and it is applied on the manufacturing of a tabique wall sample. This wall sample is monitored in terms of thermal insulation ability and its thermal transmission coefficient is estimated. Taking into account that there is still a lack of published technical information related to this topic, this article may contribute to solve this limitation and to give some guidance in future repairing processes of tabique construction. The technological benefit of adding lime or cement with earth is researched. Real tabique timber structure samples are applied in order to validate the obtained experimental results.

Tabique is a traditional Portuguese building technique using timber and earth and was intensively applied until the 20th century. There is an impressive tabique heritage that requires maintenance and rehabilitation interventions. Taking into account the facts that technical and scientific publications related to this particular technique are lacking and that the technique is also applied worldwide, this research work is a very relevant one. This study aims at studying the thermal insulation behaviour of tabique walls and in particular, tabique walls coated using metal corrugated sheets and thermally reinforced with an insulation material. This type of building component is initially characterized and some building details concerning the metal corrugated sheet coating are described. An experimental work was conducted to determine the thermal transmission coefficient of the tabique wall samples. It was concluded that providing the tabique wall coated with metal corrugated sheets with a 3 cm extruded polystyrene board results in a thermal insulation improvement of 61%. These results revealed that the thermal insulation reinforcement of tabique walls is possible and it may be a straightforward building procedure because it can be achieved using the thermal insulation building materials that are currently being used. Therefore, the thermal insulation reinforcement of tabique walls seems feasible. Furthermore, the thermal insulation parameters obtained in this study are similar to the ones obtained for currently applied walls solutions in new buildings. This technical fact may provide guidance for the possibility of using solutions used in old buildings to meet the thermal comfort requirements expected in today’s times. The knowledge gained will also be useful to support future proposals of energy rehabilitation solutions. Practical implications: In this article, tabique construction and its relevance worldwide are discussed. This article highlights the building details concerning the use of metal corrugated sheet coating on tabique walls and evaluates the thermal insulation behaviour of this wall system. The outcomes indicate that it is possible to improve the thermal insulation of a tabique wall. The data obtained in this study may be valuable for repairing tabique walls and may also inspire innovative building solutions in modern industrial practice.

Concrete columns requiring strengthening intervention always contain a certain percentage of steel hoops. Applying strips of wet layup carbon fiber-reinforced polymer (CFRP) sheets inbetween the existent steel hoops might, therefore, be an appropriate confinement technique with both technical and economic advantages, when full wrapping of a concrete column is taken as a basis of comparison. To assess the effectiveness of this discrete confinement strategy, circular cross-sectional concrete elements confined by distinct arrangements of strips of CFRP sheet are submitted to a direct compression load up to the failure point. The influence of the width of the strip, distance between strips, number of CFRP layers per strip, CFRP stiffness, and concrete strength class on the increase of the load carrying capacity and ductility of concrete columns, is evaluated. An analytical model is developed to predict the compressive stress-strain relationship of concrete columns confined by discrete and continuous CFRP arra...