A comparative study on the long-term microstructure of soil stabilisation with calcium and magnesium-based binders.
الملخص
Abstract: Analytical and microstructure investigations such as x-ray diffraction (XRD), derivative thermogravimetric (DTG), and scanning electron microscopy (SEM) among others, are typically used by researchers to detect and quantify the amount of formed minerals including ettringite minerals in gypseous soil treated with lime or cement. However, the detection of ettringite crystals is sometimes difficult, suggesting that the appearance of ettringite under the microstructure analysis is also dependent on the curing and experimental procedure. Therefore, a series of soil mixtures designed by use of two different soils (pure kaolin soil and artificial gypseous kaolin soil) and stabilised with 10 wt% of lime-L, cement-C and MgO-M, were investigated using multi-scale investigations including XRD, DTG and SEM. Accordingly, the result revealed that, under 90-days of moist curing, the key minerals detected in gypseous kaolin stabilised with calcium-based stabiliser are kaolinite, calcium silicate hydrate, portlandite, and ettringite, whereas only kaolinite, gypsum, brucite and magnesium silicate hydrate were detected in gypseous kaolin stabilised with magnesium oxide. However, under 200-days of water soaking period, no trace of gypsum, ettringite and portlandite were detected in the XRD of 10L- and 10C-based specimens, accompanied by the indication of new minerals (hemihydrate, anhydrite, calcite, and aragonite), suggesting the carbonation of ettringite during the soaking in water.