Revista Ingeniería de Construcción

3D printed concrete as a source of recycled aggregates: potential for multi-recycling and CO2 sequestration

Iván Navarrete — 2024-12-30

Additive manufacturing of concrete (3D printed concrete, 3DPC), is an emerging technology with numerous possible applications and benefits for the digital transition of the construction industry. At the same time, there remain open questions about the environmental suitability of 3DPC. One such aspect is its circularity, i.e. recyclability. Therefore, in this study, the viability of recycling 3DPC is studied on normal- and high-strength 3DPC concretes produced with 0–100% of fine recycled aggregate (fRA). After testing for basic mechanical properties, the specimens were crushed and new (2nd generation) fRA were obtained and tested. The results point to a high potential for recyclability of 3DPC and fRA conducive to multi-recycling and CO₂ uptake through carbonation.

CO2 mineralization in the production of sustainable concrete

Igor De la Varga — 2024-12-30

As the concrete industry continues to grapple with the challenge of reducing its carbon footprint, CO₂ mineralization technologies offer a practical and scalable solution. These technologies enable the integration of CO₂ as a valuable raw material, transforming waste emissions into durable mineral compounds during the concrete production process. This study investigates the implementation of CO₂ mineralization in fresh concrete, analyzing its effects on key material properties such as strength and durability. Experimental results reveal that the process not only ensures equivalent compressive strength of concrete with a reduced cement content, but also contributes to reductions in embodied carbon compared to traditional methods. Furthermore, the study underscores the role of this approach in supporting the industry's decarbonization efforts, aligning with global sustainability goals. The findings highlight CO₂ mineralization as a pivotal step toward the creation of more sustainable construction materials, offering both environmental and economic benefits. These conclusions demonstrate the transformative potential of this technology in advancing the sustainability of concrete production while addressing the pressing demand for eco-friendly construction practices.

Decarbonization of Materials and Construction Processes

Marcelo González — 2024-12-30

The construction industry, responsible for 39% of global greenhouse gas emissions, faces an urgent need for decarbonization to meet Net Zero Emissions by 2050. Addressing this challenge in the context of issues like structural fragmentation and complex value chains requires innovative solutions and accelerated implementation. This special issue of the Revista Ingeniería de Construcción presents contributions from academics and practitioners across multiple countries, exploring critical decarbonization trends in the industry.

Featured topics include low-carbon materials, recycling innovations, material design and performance, use of industrial by-products, and infrastructure quality assurance and preservation.

The findings underscore the need for collaboration, innovation, and research to advance sustainable practices, aligning the construction sector with global decarbonization goals. This work invites stakeholders to contribute to transforming construction towards a more sustainable future.

Design approaches for sustainable concrete mixes and structural components

Harald S. Müller — 2024-12-30

Changes in the current use of concrete materials and design approaches are mandatory in order to comply with the requirements imposed on future sustainable concrete structures. Before this background the article indicates the design of sustainable concrete mixes (green concretes or eco-concretes) and the structural components made from them. Such concretes are characterized by a pronouncedly reduced CO₂ footprint compared to conventional structural concretes made purely with Ordinary Portland Cement (OPC).

After an introduction to the sustainability problems of today's structural concretes, the basic approaches for the development of sustainable concretes are presented. The specific parameter Concrete Sustainability Potential is introduced, which combines the main effecting parameters such as environmental impact, service life (durability) and performance (strength). An overview in possibilities available today for producing sustainable concrete mixtures is given. For good reasons, emphasis is placed on such sustainable concretes, in which a large proportion of the OPC is replaced by rock powders.

Finally, a new and innovative relationship for sustainability design is introduced. This concept is equally applicable to concrete as a material and to components made from it. The article concludes with considerations on the implementation of this new concept in practice.

Advancements in low carbon emission cements for 3D printing

Laura Silvestro — 2024-12-30

Concrete production, heavily reliant on Ordinary Portland Cement (OPC), is a significant contributor to global CO₂ emissions, responsible for about 8% of human-related emissions. While past efforts to reduce the carbon footprint of cement focused on improving energy efficiency and incorporating supplementary cementitious materials (SCMs), recent innovations have shifted towards low-carbon binders like calcium sulfoaluminate (CSA) cement, limestone calcined clay (LC3) cement, and geopolymers. These alternatives offer considerable reductions in CO₂ emissions during production. However, the adoption of these materials faces challenges, particularly in 3D-printed concrete (3DPC), an emerging construction method that demands specific rheological and mechanical properties. Research into these low-carbon binders shows that CSA cement provides rapid strength development, LC3 mixtures offer promising environmental benefits and structural integrity, and geopolymers achieve high compressive strength but require optimization for durability. This study summarizes a review of the effects of these binders on the fresh properties, mechanical performance, and durability of concrete, emphasizing their potential for use in 3DPC. The findings underscore the importance of optimizing material properties for enhanced performance and sustainability in the construction industry.

Use of Artificial fine aggregates from copper tailings in mortar

Felipe Vargas — 2024-12-30

The construction and mining industries are among the most impactful on the environment. A significant issue in the mining industry is the generation of mine tailings, with copper tailings being among the most voluminous. One potential way to utilize them is as a replacement for fine aggregates, although they are extremely fine. Through an alkaline activation process, it is possible to agglomerate them and use them in mortar mixtures. This research used copper tailings to produce an artificial fine aggregate (AFA) through an alkaline agglomeration process and assessed its impact on mortar mixtures. The results demonstrate that it is feasible to manufacture an artificial fine aggregate by alkaline agglomeration using the proposed methodology. Also, it is shown that replacement levels up to 45% show improvements in the mechanical performance of the mortar mixes. Additionally, a decrease in the density of the mixtures was observed.

The influence of Interground limestone fines and metakaolin on the electrical resistivity of portland-limestone concrete

Zichun Xia — 2024-12-30

The critical climate change has raised concern about the decarbonization of the cement and concrete industry, which is responsible for 8% of global CO2 emissions. Portland limestone cement (PLC), which is made by partially replacing the clinker with up to 15% interground limestone fines (LFs), has been recognized as a viable solution for its feasibility to match the engineering properties of ordinary portland cement (OPC). However, with the necessity of further increasing the LFs contents to meet the desired eco-efficiency, the dilution effect brought by less ultimate hydration products may be detrimental to the long-term performance of reinforced concrete structures, such as chloride-induced corrosion. Thus, this research explores the potential of combining PLC and alumina-rich supplementary cementitious materials (SCMs) to improve the resistivity of the concrete. Concrete specimens were fabricated with PLCs from two sources of three LFs replacement ratios (15, 20, and 25%). MK (8%) is used as the source of alumina. The bulk and surface resistivity results showed that combining PLC with MK can notably improve concrete resistivity even in mixtures with lower amounts of cement. Additionally, compressive strength demonstrated poor correlation with electrical resistivity, which highlights the significance of performance-based design.

Effect of Biochar Type in the Performance of Biochar-Modified Binder

Xiomara Sanchez — 2024-12-30

Biochar is obtained from the thermochemical conversion of biomass and stores carbon in a stable form. Adding biochar to asphalt could enable carbon offsetting. Biomass sources and pyrolysis technologies yield biochar with different chemical and physical characteristics. This study investigated the effect of two types of wood biochar on the binder characteristics. 5% and 10% biochar were added to a PG 58S-28 asphalt. Four biochar-modified binders and one control were characterized using rotational viscosity, penetration, frequency sweep tests, and Fourier-transformed infrared spectroscopy (FTIR). The results indicate that biochar increases the viscosity and reduces the penetration. The rheological analysis suggests that biochar could increase the rutting resistance but decrease the cracking resistance. Additionally, biochar alters the oxidative ageing of the binders. This study demonstrated that the biochar type impacts the binder performance, and source and content should be considered to understand the effect and determine the dosage of biochar to asphalt.

Use of reclaimed fly ash for the production of sustainable cementitious composites

Tomás Delgado García — 2024-12-30

This study analyzes the use of reclaimed fly ash (RFA) as an alternative cementitious material in engineered cementitious composites (ECC) mixtures. The performance of RFA-ECC is assessed by evaluating the tensile properties at 7 days, for two replacement levels of ordinary portland cement (OPC) (50% and 70%) and three polyethylene (PE) fiber contents (1.5%, 1.75%, and 2% by volume fraction). Results showed that RFA-based ECC can produce strain-hardening behavior and reach high tensile stress and strain. RFA-ECC with 50% OPC replacement and 1.5 vol.% PE fiber content exhibits average tensile strength and strain of 6.4 MPa and 8.9%, respectively. Furthermore, at 28 days, the ductile behavior remains. The study shows that RFA can be considered an alternative low carbon constituent to replace OPC in ECC mixtures, to reduce their carbon footprint, hence leading to a more sustainable cementitious composite.

The potential of using chilean biomass to develop insulating biocomposite material

Alejandro Ignacio Rios Jaqui — 2024-12-30

The rise in greenhouse gas emissions, particularly CO₂, has significantly contributed to global warming, with the residential and commercial building sectors playing a key role. Improving building energy efficiency through enhanced insulation is a crucial strategy for reducing CO₂ emissions. However, conventional insulation materials have a high embodied carbon footprint, which limits their effectiveness in mitigating climate change. Biocomposites have emerged as an eco-friendly alternative to conventional materials. Countries like Chile, with their abundant agricultural fibers, show significant potential for fabricating biocomposites. This paper identifies the most produced fibers in Chile, including eucalyptus bark, wheat straw, rice husk, corn stalks, and walnut shells, and explores their potential use in the creation of sustainable biocomposite insulation materials.

Sampling and testing for quality assurance of pavement preservation and treatments

Peter Sebaaly — 2024-12-30

Pavement preservation is essential to maintaining viable road infrastructure, slurry seal and microsurfacing, referred to as “slurry system” are widely used as cost-effective techniques for preserving asphalt concrete pavements. However, there is a need for better quality assurance (QA) tools to ensure compliance with approved job mix formulas. This research aimed to devise a field sampling procedure for slurry systems and develop a reliable and accurate QA system to determine the water content and asphalt residue content present in slurry mixes. To be deemed adequate, sampling techniques must satisfy three main criteria: sufficient amount of sampled mixture to determine asphalt residue content, safety of the sampler, and uniform and consistent collected samples. The utility cover sampling technique involves placing a non-absorptive material over a utility cover, as the mix spreader applies the mixture, the cover gets coated with a layer of slurry. This study found that asphalt felt was the most successful material for slurry mix sample collection from utility covers. The study concluded that the oven evaporation method is effective in determining the water content and the ignition oven test is effective in determining the asphalt residue content in slurry mixes.