Viviana Letelier

Durability of clay-based mixes is often considered a limitation for their use in modern construction projects, especially in those involving additive manufacturing techniques. This study focuses on developing sustainable extrudable cob mixes and investigating the effect of sand particle grading, curing regime and mix composition on compressive strength, flexural strength, stress–strain response, capillary water absorption, wetting-drying cycles effect, and abrasion resistance. Results showed a significant positive impact of fine-sized sand addition into the mix on the mechanical strength and durability, due to better compaction and denser final cob mixes. Extending oven curing improves the compressive and flexural strength of all mixes due to the accelerated strength development from the higher temperature exposure. Lastly, the addition of high clay content allows for improving the compressive and flexural strength at prolonged curing aging under normal air-drying conditions. These mixes also exhibit low water absorption. Conversely, results revealed that the lime content plays a crucial role in reducing surface wear, with lime-rich mixes exhibiting lower erosion rates than the other mixes. Lime-stabilized cob mixes also demonstrate improved durability under cyclic wetting and drying.

The construction sector undeniably has an impact on sustainability in its three dimensions: economic, social, and environmental. In this context, 3D concrete printing (3DCP) has emerged over the last decade as an attractive technology for transforming this sector. It enables the manufacture of construction elements while saving time, reducing waste, and eliminating the need for molds. However, assessments of the environmental performance of implementing this technology are limited, particularly under representative production conditions. This study evaluates the footprint family indicators, carbon footprint (CF), ecological footprint (EF), and water footprint (WF), of different mixtures of 1 m3 of 3D-printed concrete, with 1m of a high printed wall. These mixtures were made with a proportion of fresh solid aggregates; brick and concrete rubble (as demolition waste (CDW) materials) were used as partial replacements for cement. In addition, the environmental impact of using two printing technologies, gantry and robotic arm systems, is analyzed. The results show that materials are the main source of environmental impacts; the replacement of some of the cement reduces CF and EF by up to 20% and 19%, respectively, while preserving printability and buildability, as demonstrated by the stable fabrication of 1 m-high printed wall elements. However, moderate increases in WF were observed, which were associated with the electricity consumption of waste processing. These results confirm the potential for valorizing CDW in 3D printing mixtures. This environmental assessment under full-scale printing conditions supports sustainability-oriented decision-making in the construction industry.

Emission reduction in the steel industry has become a challenge due to its high environmental impact, being responsible for 7% of anthropogenic emissions. Several strategies have emerged to mitigate its carbon footprint; among them, carbon capture and storage (CCS) has become a promising long-term alternative. In this work, two low-energy mineral carbonation methods—aqueous and semi-dry—were considered for the processing of a commercial slag derived from electric arc furnace (EAF) steelmaking. These methods were selected for their lower energy and water requirements, as they operate at atmospheric pressure, moderate temperatures, and involve minimal use of chemical additives. Variables such as temperature, time, and the use of sodium carbonate were analysed. Aqueous carbonation favoured a higher carbonate precipitation compared to semi-dry carbonation. However, this process also led to an increase in microcracks on the surface. With respect to the theoretical sequestration rate, carbon dioxide fixation was relatively low, reaching values close to 3%. Nevertheless, when evaluating the overall impact of carbonation on the final material properties, the results suggest that low-consumption mineral carbonation, particularly under simplified operational conditions, is a promising strategy for industrial application. In addition to contributing to CO₂ sequestration, this process improves physical properties, which reinforces its potential in carbon capture and storage strategies.

Currently, the use of recycled aggregates (RA) in new concrete is allowed by several international regulations, although their replacement is limited to low percentages of the coarse fraction. In order to increase the percentage of RA, several authors have studied different processes to improve the microstructure of its surface. Therefore, it is necessary to analyze whether the current standards simulate the structural behavior of concretes with high percentages of RA. For this purpose, beams with 0%, 50% and 100% RA replacement coated with recycled binder paste (RBP) were made and their behavior was compared with the equations of the Eurocode 2 and ACI 318-19 code. As a result, we found that when 100% coated RA was used, the reduction in compressive strength was only 12.73%, with similar cracking patterns observed in RA beams across all series. In addition, the load capacity of the beams with RA was higher than the theoretical values provided by the codes. Finally, the experimental critical deflection was higher than that calculated by the code equations. Thus, it is recommended that these higher deflections be taken into account at the time of design.

This article focuses on the research of gas emissions in two types of brick kilns located in the Maule Region, Chile. One of them is an artisanal brick kiln known as a “chonchón” (AKC), while the other is a semi-artisanal brick kiln with an improved design. The latter is referred to as the Ecokiln. This study focuses on the assessment of the emission profiles of key pollutants such as particulate matter (PM), CO, CO₂, SO₂, and NOx. The emission measurements of gasses, temperature, and flow were conducted during the operation of the kilns. These measurements were carried out following the protocol established by Chilean standards. The Ecokiln’s design facilitates optimal fluid dynamics. In direct comparison to the AKC, it exhibits reduced fuel consumption, shorter operation periods, an increased brick processing capacity, decreased burnt brick losses, and notably lower emissions, with a concentration of SO₂ that is 83% less than that of the AKC, NOx emissions, 58% lower than the AKC, and a remarkable 74.3% reduction in PM10 emissions. Moreover, the Ecokiln reduces pollutant emissions, improving the well-being of brickmakers and their communities. These results offer insights into the environmental impact of local brick production and support sustainable manufacturing practices.