Color Changes In Clay Indicate Soil Stability

Scientists have found that soil-atmosphere interactions result in modifications of soil micro-structure, and that this is accompanied by a color change.

AsianScientist (Mar. 7, 2014) – Scientists have found that color changes can be used to indicate the suitability of soil for construction purposes.

Although much research has focused on the harmful effects of fog and haze on human health, a new study shows that interactions with the atmosphere also impact the structural stability of soil, which in turn can have serious implications on engineering and construction.

Scientists from the Chinese Academy of Sciences investigated the mechanisms driving change in the characteristics of clay under ambient temperature and pressure. Specifically, they studied the color changes of Zhanjian clay, which changes from grayish green to yellowish brown when exposed to the atmosphere. They found that the changes were driven by a reaction of oxides of iron in the clay. The oxidation of the iron oxides reduced the plasticity, sensitivity and structural yield stress of soil.

This transformation of soil properties by the atmosphere was not due to inherent changes of minerals, but motion effects and chemical reactions of the water–soil–electrolyte–atmosphere system which caused the remodeling of micro-structures in soil particles, the study found.

Considering the potentially adverse effect of prolonged oxidation on soil stability through a reduction of structural strength, this research shows that it is necessary for geotechnical engineering to monitor the effects of physical and chemical factors in the environment. The results obtained provide theoretical foundation for future assessments of soil stability in construction projects.

The article can be found at: Zhang and Kong. (2014) Research on variability characteristics of micropore of Zhanjiang clay under ambient temperature and pressure, normal atmospheric (in Chinese).

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Source: Science China Press; Photo: cobalfish/Flickr/CC.

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