An ingredient commonly used in ice cream may help scientists transform ordinary dirt into a new generation of environmentally friendly building materials.
Researchers at the University of Colorado Boulder have discovered that sodium alginate, a substance made from seaweed and often used to improve the texture of foods, can make natural materials like clay and sand much easier to 3D print into strong structures.
Their findings could eventually help reduce construction waste and lower the environmental impact of building projects.
Humans have used earth as a building material for thousands of years.
Traditional structures such as adobe homes were built from clay, sand, and other natural materials. In nature, many animals also rely on earth-based construction.
Termites build towering mounds, wasps create complex nests, and honeycomb worms make reef-like structures along coastlines.
These creatures do not use cement. Instead, they rely on natural substances called biopolymers, which act like glue and hold soil particles together.
Inspired by these natural builders, the research team wanted to find out which biopolymers could help turn soil into a material suitable for modern 3D printing.
The scientists tested five food-grade biopolymers. Some are already used in products such as salad dressings to keep ingredients from separating. Others come from seaweed or are made through sugar fermentation.
One of the substances, called locust bean gum, bonded soil particles tightly together and created a strong material. However, it also made the mixture too thick and difficult to push through a 3D printer.
Sodium alginate behaved very differently. Instead of acting like glue, it changed the electrical charges on clay particles. The particles then repelled each other, much like two magnets with the same poles pushing apart.
This effect allowed the clay and sand particles to stay evenly suspended in the mixture while still flowing smoothly through the printer. The result was a material that could be printed quickly and easily.
The researchers discovered that only a tiny amount of sodium alginate was needed. They added just 0.12% of the substance to soil collected from a granite quarry in Colorado. The mixture became both stronger and easier to print. It could withstand about 25% more pressure than untreated earth and could be printed about 33% faster.
Using the new formula, the team created a thin wall only 8 millimeters thick. The wall remained stable even when tilted at an angle of 60 degrees, which is much steeper than the famous Leaning Tower of Pisa.
The researchers say earthen building materials offer several additional benefits. Earth can help regulate indoor moisture, absorb some air pollutants, and provide natural insulation, helping keep buildings cooler in summer and warmer in winter.
Construction projects often generate huge amounts of excavated soil while digging foundations, basements, and parking areas. Much of this material is thrown away and ends up in landfills.
The researchers believe their new approach could allow builders to reuse soil directly at construction sites instead of discarding it.
Since clay and sand are among the most abundant materials on Earth, this simple seaweed-based ingredient could one day help create more sustainable and environmentally friendly buildings around the world.
