Suchergebnisse

This work has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 778045, as well as from Portuguese funds from FCT/MCTES through grant UID/AMB/04085/2019. J. Almeida acknowledges Fundação para a Ciência e a Tecnologia for her PhD fellowship 560 PD/BD/135170/2017. ; Resources efficiency regarding the decrease of residues generation and disposal are important steps towards a cleaner production in the construction and mining industry. Minning processes generate huge amounts of residues, and some deposits have accumulated them over hundreds of years, causing environmental and public health problems. However, mining residues can be recovered as secondary supplies for construction materials production due to its physical, chemical and microstructural properties. This study presents a critical review on sustainable strategies researched to introduce mining residues in the construction sector. The gaps and barriers of these strategies and final products are discussed, concerning a safe and sustainable inclusion of mine residues in construction materials production ; authorsversion ; published

PTDC/EPH-PAT/4684/2014 ; In many countries, earth was a very common construction material until the middle of the 20th century, being rammed earth one of the most widespread construction techniques. Nowadays, there are still a large number of constructions with this traditional technique, from vernacular dwellings to monuments. Therefore, rammed earth constructions integrate cultural, historical, technical and architectonic recognised value and the constant neglect of this type of constructions, without maintenance and conservations measures over time, or with inadequate interventions, presents a worrying reality. This paper aims to contribute towards increasing the knowledge on materials from 12th century Paderne castle, located in Algarve, south of Portugal. Data from interventions performed on the castle in the 20th and 21st centuries were gathered. Samples from the rammed earth castle tower and walls and mortar from a more recent chapel were collect during the 21st century interventions and characterised, mainly by microstructural and mineralogical techniques. Most of them present calcareous and siliceous aggregates in their composition, except for samples collected from the wall where no siliceous aggregates were detected. Rammed earth samples present a brownish colour being the binder a mixture of clayey earth and lime, and the coarse aggregate mostly limestone. Iron oxide/hydroxide and clay minerals, very common in earth composites, are detected and a lime + clay binder/aggregate ratio of 1:1.5 in volume is the most frequently found. The large amount of calcite in all rammed earth samples is an indication of the use of carbonate gravel mixed with a high content of air lime. The presence of white nodules in the earthen matrix induces that the lime was probably applied as quick lime and, afterwards, hydrated by mixing with the moistened earth. The lime was used as a stabiliser (technique called "military" rammed earth) to promote a hardening process by carbonation and increase durability to weathering. Therefore, characterisation results obtained in this study allow to draw conclusions about the materials and construction techniques used in the past, in order to support future compatible, effective and reversible interventions in this and in similar historic military rammed earth constructions. ; authorsversion ; published

The Fernandina old fortress of Lisbon started to be built in 1373. It is composed by 76 towers and 35 entrances along the fortress that is closed with an extension of 4.69 km, having two main sections: East, limited between St. George's Castle and Terreiro do Trigo Street, and West, starting also in the St. George's Castle and finished at Misericórdia Street. The construction technology of those sections is mainly rammed earth with an average height of 8 m. Some sections seem to be totally homogeneous but there are other composed of two parallel stone masonry walls with a nucleus filled with compacted earth. The thickness of the fortress wall is variable between 1.75 and 2.20 m. To build with rammed earth technique, humid excavated earth was placed in layers on a wood formwork and manually compacted reducing the thickness of each layer. A succession of compacted layers completed the formwork, which was laterally displaced to build the next rammed earth block. After completing the rammed earth level, the formwork was displaced to the upper level and the same cycle continues up to the top level of the wall fortress. Sometimes, particularly in defensive structures, air lime was added to stabilize the humid earth, obtaining the so called "military rammed earth". In the other case, the humid earthen materials were placed in layers and compacted inside the two parallel masonry walls that acted as formwork. The fortress is nowadays completely "emerged" and surrounded by the city. Several interventions mainly performed on old buildings confining with, or including, the old fortress have been held in the last years. Some of the sections present renders and repointing mortars that are not originals. Nevertheless, so far there is a lack of information on the materials, originals and applied in the history of interventions. Therefore, this study intends to present the characterization made in situ by visual observation and non-destructive techniques and in laboratory on samples that was possible to obtain from some sections of the old fortress walls. It is expected that the information from the material characterization will be useful to support decisions on future interventions, namely on the definition of repair mortars that need to be compatible and assure efficient conservation of sections that are being accessible of the old wall. ; authorsversion ; published

One of the biggest challenges currently faced by Society is climate change, leading to the need of mitigation of carbon dioxide (CO2) emissions, among other consequences. The construction sector is responsible for a large part of these emissions. In addition, this sector is also responsible for a significant part of all waste globally produced, about one third in the European Union. The use of construction and demolition wastes (CDW) as aggregates in mortars and concrete has been the objective of several studies. This incorporation reduces the volume of natural aggregates used in these construction products, decreasing the depletion of natural resources, while increasing the life cycle of the incorporated by-products. It thus contributes to the reduction of the environmental impacts of the construction sector. Nevertheless, recycled aggregates are not often incorporated in mortars and concrete due to their higher porosity and lower strength compared to natural aggregates. Jointly with the Portuguese cement industry, this research intends to produce more sustainable mortars and concrete by using CDW aggregates as a carbon capture and storage source. This not only reduces the global greenhouse emissions of concrete but also potentially improves the CDW aggregates' properties. To this extent, different types of CDW aggregates will be subjected to forced and accelerated sequestration of CO2, contributing to the capture of part of the CO2 emissions of the Portuguese cement industry, providing it with more sustainable processes. As a result, this study intends to contribute to the reduction of non-renewable natural resources, in the form of natural aggregates, while reusing CDW and capturing part of the CO2 released by the production of cement. This article presents the characterization of three CDW from different origin and treatments, regarding the analysis of their carbonation potential. ; publishersversion ; published