Carbonation potential of recycled aggregates from construction and demolition waste

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.publishersversionpublishe

Mortars with cdw recycled aggregates submitted to high levels of co2

Funding Information: Funding: This research was funded within the research project WP10B by c5Lab (CoLab 4/2018-CemLab).Construction and demolition wastes (CDW) are generated at a large scale and have a diversified potential in the construction sector. The replacement of natural aggregates (NA) with CDW recycled aggregates (RA) in construction materials, such as mortars, has several environmental benefits, such as the reduction in the natural resources used in these products and simultaneous prevention of waste landfill. Complementarily, CDW have the potential to capture CO2 since some of their components may carbonate, which also contributes to a decrease in global warming potential. The main objective of this research is to evaluate the influence of the exposure of CDW RA to CO2 produced in cement factories and its effect on mortars. Several mortars were developed with a volumetric ratio of 1:4 (cement: aggregate), with NA (reference mortar), CDW RA and CDW RA exposed to high levels of CO2 (CRA). The two types of waste aggregate were incorporated, replacing NA at 50% and 100% (in volume). The mortars with NA and non-carbonated RA and CRA from CDW were analysed, accounting for their performance in the fresh and hardened states in terms of workability, mechanical behaviour and water absorption by capillarity. It was concluded that mortars with CDW (both CRA and non-carbonated RA) generally present a good performance for non-structural purposes, although they suffer a moderate decrease in mechanical performance when NA is replaced with RA. Additionally, small improvements were found in the performance of the aggregates and mortars with CRA subjected to a CO2 curing for a short period (5 h), while a long carbonation period (5 d) led to a decrease in performance, contrary to the results obtained in the literature that indicate a significant increase in such characteristics. This difference could be because the literature focused on made-in-laboratory CDW aggregates, while, in this research, the wastes came from real demolition activities, and were thus older and more heterogeneous.publishersversionpublishe

Global Performance of Sustainable Thermal Insulating Systems with Cork for Building Facades

Rehabilitation of facades may be carried out with the application of External Thermal Insulation Systems (ETICS). Their main contribution is the increase of the energy efficiency of buildings. In the literature, hygrothermal, impact and fire performance studies have been carried out on several systems with different insulation materials, such as expanded polystyrene, mineral wool and extruded polystyrene foam insulation. Due to the growing concern with the environment, systems are being developed with more sustainable and ecological materials, such as ICB (expanded cork). These type of boards are responsible for a negative impact in global warming potential, significantly improving the environmental benefits of their use. As these systems were recently introduced to the market, applications on site are very recent and their behaviour over time still unknown. In this research, the durability and global performance of more sustainable systems (with ICB) were analysed through an experimental campaign and compared with EPS (expanded polystyrene) systems. The results show that the systems with ICB obtained satisfactory global behaviour comparable with the EPS systems. The ICB sustainable systems analysed stood out in acoustic performance

Carbonation Potential of Cementitious Structures in Service and Post-Demolition: A Review

The construction sector is responsible for a great environmental impact. The cement industry, which is included in this sector, emits about 650 to 800 kg of CO2 per each tonne of cement produced, being one of the most polluting industries in terms of greenhouse gas emissions. The cement manufacturing process releases about 7% of the total worldwide CO2 emissions. However, concrete and cement-based materials present CO2 uptake potential during their service life and post-demolition through carbonation processes. The carbonation reactions rate depends on several factors, namely type and content of cement, porosity of concrete, temperature, relative humidity and exposure conditions area. Therefore, to estimate the CO2 capture of concrete during its life cycle is not a straightforward calculation. Some studies have been developed using different methodologies in order to evaluate the CO2 potential of cementitious elements in service and post-demolition. This paper reviews the documented approaches that quantify the CO2 uptake of concrete over time, summarizing the assumptions adopted for each previous work. Overall, it was concluded that part of the CO2 emissions released during cement production are reabsorbed by concrete products during their life cycle, which partially offsets the environmental impact and reduces the CO2 footprint of the cement industry

Carbonation Potential of Cementitious Structures in Service and Post-Demolition: A Review

The construction sector is responsible for a great environmental impact. The cement industry, which is included in this sector, emits about 650 to 800 kg of CO2 per each tonne of cement produced, being one of the most polluting industries in terms of greenhouse gas emissions. The cement manufacturing process releases about 7% of the total worldwide CO2 emissions. However, concrete and cement-based materials present CO2 uptake potential during their service life and post-demolition through carbonation processes. The carbonation reactions rate depends on several factors, namely type and content of cement, porosity of concrete, temperature, relative humidity and exposure conditions area. Therefore, to estimate the CO2 capture of concrete during its life cycle is not a straightforward calculation. Some studies have been developed using different methodologies in order to evaluate the CO2 potential of cementitious elements in service and post-demolition. This paper reviews the documented approaches that quantify the CO2 uptake of concrete over time, summarizing the assumptions adopted for each previous work. Overall, it was concluded that part of the CO2 emissions released during cement production are reabsorbed by concrete products during their life cycle, which partially offsets the environmental impact and reduces the CO2 footprint of the cement industry

Rendering Mortars with Low Sand and Cement Content. Incorporation of Sanitary Ware Waste and Forest Biomass Ashes

The incorporation of wastes in new materials and products is an emerging trend, reducing virgin materials’ consumption and landfill deposition and the associated environmental impacts. Cement-based mortars can encapsulate some wastes, with the benefits stated above. In three previous researches, it was found that forest biomass bottom ashes (up to 15% by volume of cement), powder of sanitary ware (up to 20% by volume of sand) and sanitary ware particles above 2 mm (100% by volume of sand) can be incorporated in rendering mortars, replacing cement or sand. Several tests were performed, and it was found that each waste’s incorporation presents advantages and limitations, when compared with a reference mortar. In this research, the aim was to take advantage of the best features of each waste, combining them in order to optimize the new mortars’ characteristics. Therefore, mortars with one, two and three wastes were analysed in this research. The ternary mix mortar had a volume of wastes equal to 83%, resulting in a mortar with 15% less cement (by volume) and without any natural aggregate (all replaced with the sanitary ware wastes). The fresh, water and mechanical behaviour of the mortars with and without wastes are presented in this research. It was concluded that it is possible to take advantage of the best features of each waste and achieve mortars simultaneously with high volume of wastes and a better performance than the reference mortar (without wastes)

Concrete-Based and Mixed Waste Aggregates in Rendering Mortars

This paper presents a study of incorporation of two types of construction and demolition waste (CDW) in rendering mortars, as aggregates at 0%, 20%, 50% and 100% (by volume). Recycled concrete aggregate (RCA) and mixed recycled aggregate (MRA) were used. The former is mainly composed of cementitious waste and the latter consists of a mixture of non-segregated wastes. The performance of the cement mortars with recycled aggregates was evaluated through an extensive experimental programme. The analysis comprised workability, mechanical strength, water absorption, shrinkage, open porosity and the evaluation of durability by permeability to water under pressure after an artificial accelerated ageing test. The results are considered positive, although as the incorporation of recycled aggregates (both MRA and RCA) increased the mechanical strength, the modulus of elasticity and bulk density decreased, which leads to the production of lighter mortars that are less susceptible to cracking. The modified mortar with 20% of MRA presented the best performance, in terms of mechanical behaviour

Reduction of the Cement Content by Incorporation of Fine Recycled Aggregates from Construction and Demolition Waste in Rendering Mortars

The construction sector is responsible for one third of the total wastes produced in the EU. Finding solutions for the reuse or recycling of these wastes is one of the major environmental concerns of modern times. The replacement of sand or cement in specific construction materials, such as concrete or mortars, is a possible solution for these wastes’ management. By using construction and demolition wastes in construction materials, namely on buildings, the cycle of circular economy is closed, increasing the life cycle of the wastes in the same sector. In this research, a reduction of cement content in rendering mortars is analysed. This reduction is achieved by a decrease of the cement/aggregate ratio simultaneously with the incorporation of very fine recycled aggregate from construction and demolition waste. Two recycled aggregates were studied: recycled concrete aggregate (RCA) and mixed recycled aggregate (MRA). The fresh and hardened state properties of the mortars were analysed. Several tests were carried out to evaluate the mortars’ performance, such as mechanical strength tests, water absorption tests, drying tests and shrinkage. It was noticed that the incorporation of RCA led to a better behaviour than in the reference mortar, in terms of mechanical strengths and protection against water

Life Cycle Assessment of Mortars with Incorporation of Industrial Wastes

The production of waste is increasing yearly and, without a viable recycle or reutilization solution, waste is sent to landfills, where it can take thousand to years to degrade. Simultaneously, for the production of new materials, some industries continue to ignore the potential of wastes and keep on using natural resources for production. The incorporation of waste materials in mortars is a possible solution to avoid landfilling, through their recycling or reutilization. However, no evaluation of their “sustainability” in terms of environmental performance is available in the literature. In this sense, in this research a life cycle assessment was performed on mortars, namely renders, with incorporation of industrials wastes replacing sand and/or cement. For that purpose, eight environmental impact categories (abiotic depletion potential, global warming potential, ozone depletion potential, photochemical ozone creation potential, acidification potential, eutrophication potential, use of non-renewable primary energy resources, and use of renewable primary energy resources) within a “cradle to gate” boundary were analyzed for 19 mortars with incorporation of several industrial wastes: sanitary ware, glass fiber reinforced polymer, forest biomass ashes, and textile fibers. Sixteen out of the 19 mortars under analysis presented, in all environmental impact categories, an equal or better environment performance than a common mortar (used as a reference). The benefits in some environmental impacts were over 20%

Mortars with construction and demolition waste recycled aggregates after CO2 exposure

CoLAB 4/2018-CemLabO aquecimento global é causado pela quantidade crescente de gases com efeito de estufa na atmosfera, assumindo-se como uma das maiores ameaças ambientais a nível mundial. Assim, têm surgido esforços globais para a sua mitigação, nomeadamente através da redução das emissões de gases, particularmente do dióxido de carbono (CO2). Diversas estratégias de captura e armazenamento do CO2 emitido têm sido estudadas e vindo a ser implementadas. Os resíduos de construção e demolição (RCD) são gerados em grande abundância e têm um potencial diversificado no sector da construção, que é a indústria que os gera e tem maior responsabilidade na sua gestão. Não obstante os estudos já desenvolvidos, a sua utilização em materiais de construção, como argamassas, é ainda limitada. Esta incorporação reduz o volume de matéria-prima natural utilizada nestes produtos, abrandando assim o esgotamento de recursos naturais, ao mesmo tempo que reduz a energia que incorporam e aumenta o seu ciclo de vida. Complementarmente, muitos RCD têm potencial para captação de CO2 produzido pela indústria, por processos químicos ou físicos. Este artigo visa apresentar os primeiros resultados de um estudo de avaliação de desempenho de agregados reciclados após submissão a carbonatação forçada e acelerada, com o objectivo de contribuir para a captação de CO2. São estudadas argamassas cimentícias fabricadas com agregados naturais (argamassas de referência) e com agregados reciclados antes e após carbonatação, com um traço volumétrico de 1: 4 (cimento: agregado). Pretende-se, desta forma, contribuir para a captação de parte das emissões de CO2 da indústria cimentícia Portuguesa, dotando-a de mecanismos que permitam torná-la mais sustentável em termos energéticos e ambientais. Adicionalmente, pretende-se contribuir para a diminuição da extracção de recursos naturais não renováveis, na forma de agregados naturais, por parte do sector de construção.authorsversionunpublishe