International Concrete Abstracts Portal

The ecological and health issues of construction and demolition waste (CDW) accumulation, as well as the depletion of virgin raw materials from the increased use of concrete are pushing the drive for the reuse of this waste in more construction-related applications. The objective of this study is to investigate the production of geopolymer mortars (GM) prepared with maximum amounts of CDW materials such as concrete, red clay bricks, and ceramic tiles, along with smaller contents of supplementary cementitious materials like Fly ash C, ground granulated blast-furnace slag, and metakaolin. The study also examined the effects of concrete waste aggregates (CWA) on the flowability and compressive strengths of GM prepared with CDW- binders and exposed to three exposure conditions of ambient environment, water immersion, and high temperature. An algorithmic mixture design method was used to determine the ideal composition ratios of silica oxide to alumina oxide, sodium oxide to silica oxide, and liquid to solid binders. Although the use of concrete waste aggregates resulted in lower compressive strengths compared to silica sand and natural sand, it was possible to achieve appropriate structural strengths and dimensional stability for highly sustainable mortars combining both CDW-binders and CWA-aggregates.

Concrete has played a pivotal role in shaping the modern world’s infrastructure and the built environment. Its unparalleled versatility, durability, and structural integrity have made it indispensable in the construction industry. From skyscrapers to long-span bridges, water reservoirs, dams, and highways, the ubiquitous presence of concrete in modern society underscores its significance in global development. As we stand at the crossroads of environmental awareness and the imperative to advance our societies, the sustainability of concrete production and utilization is becoming a new engineering paradigm. The immense demand for concrete, driven by urbanization and infrastructure development, has prompted a critical examination of its environmental impact. One of the most pressing concerns is the substantial carbon footprint associated with traditional concrete production. The production of cement, a key ingredient in concrete, is a notably energy-intensive process that releases a significant amount of carbon dioxide (CO2) into the atmosphere. As concrete remains unparalleled in its ability to provide structural functionality, disaster resilience, and containment of hazardous materials, the demand for concrete production is increasing, while at the same time, the industry is facing the urgency to mitigate its ecological consequences. This special publication investigates the multi-faceted realm of concrete sustainability, exploring the interplay between its engineering properties, environmental implications, and novel solutions, striving to provide an innovative and holistic perspective. In recent years, the concrete industry has witnessed a surge of innovation and research aimed at revolutionizing its sustainability. An array of cutting-edge technologies and methodologies has emerged, each offering promise in mitigating the environmental footprint of concrete. Notably, the integration of supplementary cementitious materials, such as calcined clays and other industrial byproducts, has gained traction to reduce cement content while enhancing concrete performance. Mix design optimization, coupled with advanced admixtures, further elevates the potential for creating durable, strong, and eco-friendly concrete mixtures. Concrete practitioners will gain an advanced understanding of a wide variety of strategies that are readily implementable and oftentimes associated with economic savings and durability enhancement from reading these manuscripts. The incorporation of recycled materials, such as crushed concrete and reclaimed aggregates, not only reduces waste but also lessens the demand for virgin resources. Furthermore, the adoption of efficient production techniques, along with the exploration of carbon capture and utilization technologies, presents an optimistic path forward for the industry. This special publication aspires to contribute to the ongoing discourse on concrete sustainability, offering insights, perspectives, and actionable pathways toward a more environmentally conscious future.

In this study, the behavior of a calcined mixed clay (CMC) exhibiting a particularly high metakaolin content (~51 %) in composite cements (substitution rates 0–50 wt. %) was studied. It was found that CMC much decreases workability and substantially increases the water demand due to its higher fineness as compared to OPC. Furthermore, the water demand of pure calcined clays was investigated, and the order as follows was established: meta muscovite ≫ meta illite ≫ metakaolin > meta montmorillonite. Additionally, the dispersing effectiveness of a series of precast-type PCEs selected from the groups of MPEG, HPEG, and IPEG polymers was tested in blended cements holding 0–50 wt. % of the CMC. According to this, the HPEG PCE disperses these composite cements best, followed by the IPEG and the MPEG PCEs. Generally, the presence of CMC prompts significantly higher PCE dosages (up to 800 % more for the 50:50 OPC/CC blend). Furthermore, it was found that in OPC/CMC blended cements slump retention is much more difficult to achieve than in OPC. As such, an industrial ready-mix type HPEG PCE or its combination with sodium gluconate failed to provide flowability retention times which are commonly required by the ready-mix industry. Our study concludes that while such low carbon calcined mixed clay blended cements offer significant ecological advantages, they demand higher superplasticizer dosages which negatively affects their cost-effectiveness and at the same time poses significant technical challenges, particularly in ready-mix concrete applications. It should be mentioned that the problems pointed out here will be less severe for CMCs of lower metakaolin content.

Sponge city is also called “water-elastic city” because of its good flexibility in adapting to environmental changes and coping with natural disasters caused by rain. When it rains, the water can be absorbed and stored, and when needed, the stored water can be released and used. Sponge city can not only solve the outstanding problems such as waterlogging disasters, rainwater runoff pollution, and water resource shortages, but also help to restore the urban water ecological environment and bring comprehensive ecological environmental benefits, is one kind of ecology sustainable development city pattern. In the construction of sponge city, the concrete material with high water absorption and water storage is an extremely important building material. In this paper, the effects of different superplasticizer and foaming agents on the properties of porous water-absorbing and water-storing concrete materials are studied, and the influence of the interaction between superplasticizer and chemical foaming agent on its pore structure, compressive strength, and water absorption and water holding capacity was analyzed.

Ultra-High Performance – Fiber Reinforced Cementitious Composites (UHP-FRCC) show excellent mechanical performances, and therefore can be effectively used to retrofit concrete structures. Similarly to the traditional Reinforced Concrete (RC) jacketing, also when a layer of UHP-FRCC is applied on an existing column a sort of confinement can be obtained. Accordingly, the purpose of this study is to investigate the performances of plain concrete cylinders, confined by UHP-FRCC and subjected to uniaxial compression. In some of the layers, high volume fly ash has also been used to replace part of the cement and reduce the environmental impact. As a result, the compressive strength of the concrete core can be enhanced by the presence of UHP-FRCC layer, but when partially using fly-ash, the confinement effect of the jacket reduced. To determine the best solution among the different proposed options, the eco-mechanical analysis was also carried out.