Microfabric and mineralogical studies on the stabilization of an expansive soil using cement by-pass dust and some types of slags

This paper describes the microfabric and mineralogical aspects of the expansive soil of Al-Khod (northern Oman) treated with cement by-pass dust (CBPD), copper slag, slag-cement, and granulated blast furnace slag (GBFS). First, the engineering properties and chemical and mineralogical composition of the untreated soil were determined. The soil was then mixed with the additives at 3, 6, and 9% of the dry weight of the soil. The microfabric and mineralogical characteristics of the treated soil were determined. The high amounts of calcium ions and calcium oxide, which produces calcium ions, react with the clay particles through a cation exchange process resulting in the formation of aggregations and reduction of the swell potential of the soil. Mineralogical tests on the treated samples indicated a general reduction in all clay minerals peak intensities, particularly in the case of CBPD treated samples. The fabric of the untreated soil is composed of dense clay matrices with no appearance of aggregations or ped formations with increasing amounts of pore spaces. However, aggregations and few connectors were formed due to the addition of the stabilizers. Aggregations and bindings were formed for all of the soils treated with GBFS and for those with 9% additions of CBPD and slag-cement. The mineralogical and microfabric results were correlated with the swell percent and swell pressure of the treated samples. The formation of aggregations and reduction in clay minerals peak intensities resulted in the reduction of the swell pressure and swell percent values.Key words: microfabric, mineralogy, stabilization, expansive soils, SEM, XRD.