Corn Cob Ash and Ferric Chloride Stabilize Expansive Soil, RSM Study Finds

Expansive soils, which swell and shrink markedly with moisture changes, pose a persistent threat to pavements, foundations and other civil infrastructure. A new peer-reviewed study, published open access in Discover Applied Sciences on 28 October 2026, reports that combining Corn Cob Ash (CCA), a waste agricultural product, with the chemical additive ferric chloride (FeCl3) can substantially improve the engineering behaviour of these difficult geomaterials.

The research team, led by Thaneti Lilly Rani and Chappidi Hanumantha Rao with Anuja Charpe and N. Venkata Sairam Kumar, adopted a historical data design within the Response Surface Methodology (RSM) framework. The experimental matrix consisted of 36 predefined mixtures in which CCA content ranged from 0 to 15 percent, FeCl3 dosage from 0 to 2 percent, and soaking duration was set at 0, 7 or 28 days.

Four responses were used to evaluate the stabilized soil: the Plasticity Index (PI), the Free Swell Index (FSI), the Maximum Dry Density (MDD) and the California Bearing Ratio (CBR). According to the abstract, PI and FSI were significantly reduced, while MDD and CBR improved significantly, as the content of the stabilizers and the length of the soaking duration increased.

The optimum stabilization condition identified by the models was approximately 13.14 percent CCA, 1.43 percent FeCl3 and 22.82 days of soaking. This combination yielded a Plasticity Index of 15.57 percent, a Free Swell Index of 51.81 percent, a Maximum Dry Density of 1.71 g/cm3 and a California Bearing Ratio of 6.93 percent, with a desirability value of 0.958.

The predictive quality of the developed quadratic models was reported as very good, with R2 values greater than 0.95. The models were validated against three independent experimental mixtures, and the agreement between predicted and experimental responses was described as good, with prediction errors of less than 5 percent, which the authors say indicates the reliability and predictive capability of the models.

Beyond the laboratory results, the study frames the approach as a sustainability measure. Using agricultural waste derived CCA alongside FeCl3 is described as an effective method of stabilization for expansive soils, one that can be sustainable in terms of utilizing agricultural wastes and reducing the use of conventional stabilizing materials.

Readers should note that the article is being shared early to provide faster access to peer-reviewed, accepted research; it is citable and carries a permanent DOI, but this version is subject to further edits and will be replaced by the final Version of Record. The reported findings come from laboratory testing of a single soil treated with specified dosages, and the abstract does not report field trials or long-term performance data.

Subject of Research: Stabilization of expansive soil using Corn Cob Ash and ferric chloride optimized with Response Surface Methodology

Article Title: Sustainable stabilization of expansive soil using Corn Cob Ash and Ferric chloride through experimental investigation and RSM optimization

Article References: Rani, T. L., Rao, C. H., Charpe, A., & Kumar, N. V. S. (2026). Sustainable stabilization of expansive soil using Corn Cob Ash and Ferric chloride through experimental investigation and RSM optimization. Discover Applied Sciences. https://doi.org/10.1007/s42452-026-09728-1

Image Credits: AI Generated

DOI: 10.1007/s42452-026-09728-1

Keywords: expansive soil, soil stabilization, Corn Cob Ash, ferric chloride, Response Surface Methodology, California Bearing Ratio, Plasticity Index, Free Swell Index, Maximum Dry Density, agricultural waste, geotechnical engineering, Sustainable