Geochemical, Index, and Strength Appraisals of Granite-derived Residual Soils

This research work examined the geochemical, index, and strength properties of lateritic residual soils from granitic parent rock in Akure, southwestern Nigeria. The aim is to underscore the potential use of such soils as engineering fills materials. The geochemical method involved the use of X-Ray Fluorescence (XRF). The major oxides determined from this analysis were used for the geochemical quantifications of the soils. Analysis of soil index properties involved consistency limits, grain size distribution and specific gravity tests, while the strength analysis involved compaction and unconfined compressive strength (UCS) tests. Results obtained from the index analysis classified the soil profile into behavioral groups VII and VI. These indicates that the soils are of high to intermediate plasticity and compressibility. The UCS values vary from 272.6 to 377.2 kPa while the shear strength values range from 138.8 to 188.6kPa, indicating good bearing capacity. The geochemical results revealed iron-oxide variations as the major influential constituent within the soil profile. Furthermore, the more lateriterizad zones correspond with the more competent horizons. The residual soils from the study area are found to be suitable materials in engineering construction works as Sanitary landfills and Subgrade materials.

The Effect of Chemical Composition of Ultramafic and Mafic Aggregates on Their Physicomechanical Properties as well as on the Produced Concrete Strength

This study examines how the chemical composition of ultramafic and mafic rocks effects their physicomechanical properties and therefore how influences the concrete strength of the produced concrete specimens. For this scope, ultramafic (Group I) and mafic rocks (Group II) derived from the Veria–Naousa and Edessa ophiolite complexes (Greece) were selected in order to identify their chemical composition and their engineering properties according to international standards. Additionally, representative rocks were used as concrete aggregates in order to produce concrete specimens, whereas their mechanical strength was calculated. A geochemical index (Ga) was proposed and correlated with the engineering properties of the examined rocks as well as with the widely used alteration degree LOI (loss on ignition). Correlation diagrams between engineering properties and the proposed geochemical index (Ga) have showed that these properties were strongly influenced by the alteration processes expressed via Ga index. More particularly, mainly serpentine in ultramafic and chlorite in mafic rocks, minerals indicators for the alteration of ultramafic and mafic rocks, respectively, seem to determine their engineering properties. Concerning the mechanical strength of the produced concrete specimens, the results have showed that the increasing values of Ga index negatively effect concrete strength.