A research team in the US are investigating the use of soil as an alternative to concrete in 3D printed buildings. If successful, they say it will help the construction industry develop more sustainable building methods and could provide “dignified” homes in poorer regions.
Using local materials such as soil would reduce energy requirements to manufacture the concrete, cut transport requirements and increase opportunities to recycle materials. Whilst there is a carbon cost to using soil – which can lock up carbon over both short- and long-term timescales, making it an important storage mechanism – it will be far lower than the carbon and environmental cost of using concrete.
The researchers have investigated the use of different soil horizons (layers), which are made of different materials. The top layer is made mainly or organic material, and below this are increasing levels of mineralisation that include sand, silt and clay until bedrock is reached. The researchers combined collected material with an environmentally-friendly additive so that it would bind and could be used in a 3D printer. The aim, they said, was to create a chemistry toolkit that can be used in locations that have a different soil make up.
Globally, about 39% of energy-related and process-related carbon dioxide emissions come from construction. It is estimated that 7-8% of total CO2 emissions are associated with cement production. However, professionals in the industry have said that 3D printing buildings does open the opportunity for greener production methods and the use of alternative materials.
Speaking to the UK’s Guardian, Sarbajit Banerjee, professor of chemistry and materials science and engineering at Texas A&M University, said “We envision a new paradigm of construction that uses naturally sourced materials. Using such materials will further pave the way for building designs that are specifically adapted to the needs of local climates, instead of cookie-cutter houses.”
Load-bearing capabilities of the soil needed to be improved if its use is to become more widespread. Here, a zippering technique has been used to prevent water absorption and expansion, which allowed the material to hold twice as much weight as the unmodified mixture.
The use of novel and recycled materials has been highlighted as a needed advance for construction. Coupled with 3D printing, it would enable buildings to take shapes not possible – or difficult to achieve – using traditional construction methods, and reduce emissions associated with the industry.
Speaking at the Construction Technology Forum last September, Prakash Senghani, Director, Head of Digital Delivery at JLL told the audience: “We have focused on concrete because as an industry we are very comfortable with it – we know how it works and understand its properties. The real value will come with some of the exotic materials and material science in 3D printing, such as bio-based materials, and that is the next wave of 3D printing that will accelerate its adoption.”