Additive Manufacturing of Concrete for Sustainable Construction using Locally Developed Materials
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abstract
Nearly all civil engineering projects still rely on decades-old concrete production methods รข a lack of innovation on the part of the construction industry that limits production efficiency and has made the industry one of the primary contributors to greenhouse gas emissions. Concrete - the second most consumed material in the world after water, despite its durability, when conventionally produced using Portland cement deteriorates over time under the influence of mechanical and environmental impacts. Thus, the goal of the proposed research is to leverage additive manufacturing (AM) technologies with a view to breaking this stagnation and enable production of innovative concrete mixtures for custom applications. AM, often referred to as 3D printing, is a smart manufacturing method, which often involves a layer-by-layer deposition of material to build 3D structures. AM applications in concrete manufacturing have the potential to reduce material and labor waste, drive down cost; minimize operator exposure to safety hazards, improve construction efficiency, while concurrently offering greater design flexibility. The custom applications considered in the proposed project revolve around improved thermal, mechanical and acoustic properties of concrete structures suited to environmental conditions in the State of Qatar and Turkey. The proposed project seeks to optimize the 3D printing process through an approach that involves designing a 3D printer nozzle to suit any given building design or retrofitting application. The effects of print speed, time gap between layers, and nozzle standoff distance on the various properties of printed materials will be investigated. The project also aims to manufacture from recycled materials novel concrete mixtures that are suitable for retrofitting applications including cladding, addition of aesthetic features and improvement of the thermal insulation of buildings. Hence, the following specific tasks will be carried out to achieve the goals of optimizing the 3D printing process and manufacturing from recycled materials novel green concrete mixtures that reduce CO2 emissions. The design, development and process optimization of 3D printing platforms for laboratory and field use will be implemented. The currently unutilized portion of construction and demolition wastes (CDW) (waste concrete/glass and wall/roof members) will be maximized for cement-free concrete production (100% geopolymeric binding phases) by taking advantage of the geopolymerization technique (i.e. chemical reaction between solid alumino-silicate oxides and alkali silicates). This will involve improving the quality of the interfacial transition zone (ITZ) between binding phases and different-size CDW-based aggregates. Rheological properties as well as the thixotropic and workability characteristics of the green geopolymeric concrete will also be investigated. Further, a life cycle, sustainability and manufacturing assessment will be conducted to determine the effect of the use of local materials and CDW in concrete mixture design for the 3D printing process on the supply chain in construction operations in Qatar and Turkey. Ultimately, the performance characteristics of the aforementioned concrete mixtures related to the 3D printing process such as extrudability, buildability, open time.........
