Abstract
The construction industry is being buffeted by winds of change, balancing the urgent need to remedy deteriorating infrastructure in the developed world and the push to build new infrastructure in emerging economies whilst devising means to better its catastrophic carbon footprint. Much of the deleterious environmental impact of construction results from the utilization of concrete as well as inefficiencies across the construction process that result in considerable waste and energy expenditure. Additive manufacturing methods stand poised to substantially transform the industry by enhancing automation, enabling economy of materials use, and allowing for unprecedented fusion of form and function; however, reliance on concrete as the extrusive material of choice has the potential to greatly compound mounting environmental challenges. In this perspective, we discuss our efforts to develop an altogether new palette of naturally sourced construction materials based on natural soils, which are reconfigured into extrudable formulations compatible with additive manufacturing. We furthermore delineate a roadmap bringing together soil chemistry with composite science, modeling of mesoscale phenomena, rheological studies of extrudable soil “inks”, generative design, post-synthetic modification, and the development of robust structure—function correlations relating atomistic and mesoscale structures as well as geometry of the architectures to load-bearing capabilities and mechanical response. We illustrate this approach using a naturally harvested burlewash clay sample crosslinked through formation of a siloxane framework, which has been 3D printed into a load-bearing structure. The need for an integrated life cycle assessment approach is emphasized to ensure development of a new palette of sustainable construction materials.
Highlights
The construction industry serves as one of the primary bulwarks of the global economy; global construction spending is estimated to be 13% of GDP, and some estimates suggest that about 7% of the world’s working age population is employed in activities related to construction (Barbosa et al, 2017)
The building sector is responsible for over 48% of global energy consumption each year including for building construction and operation, thereby accounting for over 40% of global carbon emissions (Copiello, 2016; Dixit, 2017, 2018)
As an example of the practical feasibility of harvesting local soils and plant fibers to build load-bearing structures, we have recently reported a method for preparing a densified composite material suitable for use in roadworks from muskeg fibers and wood chips sourced from Northern Alberta that are cross-linked using soluble silicates and functionalized cellulose (Waetzig et al, 2017)
Summary
The construction industry serves as one of the primary bulwarks of the global economy; global construction spending is estimated to be 13% of GDP, and some estimates suggest that about 7% of the world’s working age population is employed in activities related to construction (Barbosa et al, 2017). As such, building materials play a substantial role in the total energy and carbon embodied within a building Both direct and indirect impacts of construction can be potentially mitigated to a large extent by adopting altogether new structural materials and efficient construction methods that allow for economy of materials use and reduction of waste generation. An urgent imperative is a rigorous life cycle assessment and embodied energy accounting of natural materials and their reconstitution processes to serve as a blueprint and provide guiding principles for the design of novel structural materials Such accounting will further enable a clear contrast to be drawn with the utilization of concrete. In order to incorporate clays within conventional geopolymer formulations and concrete without compromising rheology and mechanical strength of the 3D printed material, appropriate surface modification schemes have to be designed to facilitate compatibility and to potentially engender pozzolanic reactions
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