Special Issue on “Recycling Waste in Construction Materials, Volume II”

Recycling plays a key role in decreasing present-day waste. The reduction in and reuse of waste can assist in maintaining an ecological economy via the substitution of crude material contributions to, and diverting waste yields out of, the monetary framework. Indeed, the recycling of waste materials is an effective strategy to develop sustainable construction materials. By implementing these strategies, the environmental impact of the construction industry can be minimized, and humanity can move towards a more sustainable and circular economy. Reduction is the first step in sustainable waste management. The primary goal is to reduce the amount of waste generated and the quantity of raw materials used in the manufacturing process. Additionally, we should aim to designing buildings and structures that require fewer materials or select materials that are more durable and long-lasting. By reducing waste at the source, the need for disposal can be minimized and a more sustainable and efficient system can be created. Reuse is another effective strategy for developing construction materials. By reusing waste materials, the demand for virgin resources is reduced and the amount of waste sent to landfills decreased. Finally, the recycling process is the most well-known strategy for waste management, and it is particularly effective in construction materials. By recycling waste materials, the amount of waste sent to landfills is reduced, the natural resources are conserved, and a more sustainable and circular economy is implemented. By improving the way in which products are produced and used, and volume of raw materials required is minimized, and moves can be made towards the more efficient reuse, repair, and recycling of components.

Due to the growing amount of residual waste, we must develop a waste hierarchy to provide viable alternatives to managing waste, and begin efficiently using resources to move towards a low-carbon economy. This includes the development of sustainable alternatives that can reuse different kinds of waste by formulating them into secondary materials. Human activities, such as construction, impact the environment. Recycling waste reduces disposal costs and carbon emissions. It also helps to comply with environmental legislation and landfill restrictions. In this sense, it is important to find appropriate alternatives to ordinary Portland cement (OPC) in the field of construction.

This Special Issue aimed to collect scientific contributions and subjects about:

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Sustainable development and production, considering management, instruments, methods, and processes.

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Innovation processes and methodologies related to improving the productivity of waste/by-products and resource management practices.

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Life-cycle assessment and management of waste/by-products to improve efficiency and productivity.

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Construction and demolition waste (CDW); the properties and applications of recycled aggregates from construction and demolition waste.

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Development of construction material from nontraditional concrete including waste/by-products.

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Geopolymers and alkali-activated materials (AAM).

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Magnesium phosphate cement.

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Repairing materials.

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Lightweight materials and aggregates.

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Reliability studies of formulations including waste/by-products.

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Aggressive environments: damage and fracture.

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Long-term behavior.

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Environmental assessments of construction materials including waste/by-products.

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Recycling and reuse.

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Landfill disposal.

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Economic analysis.

A total of nine research papers in different fields were presented and published in this Special Issue. Each submission centered on the use of waste in construction field. Devaraj et al. [1] explored the effects of fresh sand substitution with crushed waste glass and developed concrete mix design. Giro-Paloma et al. [2] reported that it is possible to use CSP (a glass residue currently disposed of in landfills) to developing more ecologically sustainable binders by employing a circular economy strategy. The main application of this is as a non-hydraulic binder for specific purposes such as prefabrication, decoration, insulation walls, or flooring material. Moreover, Bih Numfor et al. [3] used pulverized low-density polyethylene (LDPE) waste as a source to reinforce and improve the compressive strength and reduce the water absorption of geopolymer ceramics formulated from metaclay and metakaolin aluminasilicates. Another study was that of Ibáñez-Gonsálvez et al. [4]. They studied the effects produced in the long term by ternary binders. The authors consider the impact of the additions of blast furnace slag, fly ash and limestone in the microstructure, durability, and mechanical performance of mortars, compared to mortars without additions and mortars made with binary binders. The best compressive strength result was achieved with a ternary binder with both slag and fly ash, and this result was probably produced by the synergetic effects of slag hydration and fly ash pozzolanic reactions. On the other hand, Pahlavan et al. [5] synthesized air lime mortars via the addition of two types of sesame cooking oil. These were cured in the laboratory and natural climatic conditions of the Pasargadae and Persepolis World Heritage Sites. Espuelas et al. [6] investigated the ability of insulation cellulose fiber powder to be pelletized for its valorization as biomass fuel. Salas et al. [7] scaled the introduction of large amounts of industrial inorganic into fired clay cycles up to industrial production without significantly altering the technical properties of products. Furthermore, Piccolo et al. [8] developed AAM-exploiting biochar, a secondary raw material coming from pyrolysis/gasification processes, for the improvement of soil fertility and reduction of CO₂ emissions because of the carbon sink process. Because of the promising technical results obtained, the AAM can be used for insulating panels or lightweight materials for houses and gardens in terraces and balconies. Finally, Malchiodi et al. [9] studied a sustainable alternative to managing cork waste from bottle caps to avoid delivering it to waste-to-energy plants. In the study, the authors demonstrate the feasibility of using the manufacturing waste from cork bottle caps to produce green construction materials, thus upgrading it from waste to a secondary raw material.

Although submissions for this Special Issue closed on the 10th of February 2022, more in-depth research in the field of waste use in the construction sector continues to address the challenges we face today, such as climate change, alternative sustainable materials, and energy crises.