Strengthening soils sustainably with bio-based stabilisers

– Souptika Das

Exploring bio-stabilisation methods for sustainable ground improvement and use of natural additives for environmentally responsible development (Image: Ripsa Rani Nayak)

Cement industries have been categorised as highly polluting by the Central Pollution Control Board of India, and studies also show that they are among the top contributors to CO2 emissions. Besides being a key construction material, cement is also widely used to stabilise soil before construction, to prevent geotechnical mishaps.

To address this challenge, researchers from the Department of Civil Engineering and Centre for Sustainable Technologies at IISc have investigated low-carbon, eco-friendly alternatives to cement. Their recent study, published in Scientific Reports, highlights a promising sustainable approach – using biopolymers and bioenzymes instead of traditional cement and lime to stabilise soil.

In controlled experiments, researchers mixed sand with 15% kaolin clay and treated the blend with varying amounts of two bio-additives – TerraZyme (bioenzyme) and Xanthan gum (biopolymer). After curing for 30 days, the mixtures were subjected to stress and compression tests to evaluate physical, chemical, and mechanical properties. The results were striking: both additives significantly increased the soil’s shear strength by up to 2.5 times compared to untreated samples.

The team found that TerraZyme alters the surface chemistry of soil particles, improving compaction and grain bonding, while Xanthan gum forms a gel-like network that binds soil particles, creating stronger internal cohesion. Kaolin also played a crucial role in increasing the reactivity and bonding effectiveness of both biomaterials.

The study confirms that biopolymers and bioenzymes can significantly enhance soil stability. The effectiveness of TerraZyme as a soil stabiliser has been further put to test and shown to be successful in building roads under the Pradhan Mantri Gram Sadak Yojana (PMGSY) scheme.

Research team 

REFERENCE:

Thomas G, Nayak RR, Gupta NK, Latha GM, Strength and microstructural behaviour of sand Kaolin mixtures stabilized with terrazyme and Xanthan gum, Scientific Reports (2026).
https://doi.org/10.1038/s41598-026-38011-x

LAB WEBSITE:
https://civil.iisc.ac.in/~madhavi/