Calcium leaching from cementitious materials into bentonite is a key process for the long-term alteration of cement–clay interfaces engineered barrier systems. Strong chemical gradients between cement and clay drive precipitation minerals such as calcium silicate hydrate (C–S–H) calcite. To analyze mineralogical porosity evolution at interface, composite specimens consisting paste mixed with va...

This study aims to use natural carbonated Tunisian clay as an aluminosilicate precursor for the elaboration of phosphate-based geopolymers, which yields valorization this common material in Tunisia. In addition, presence calcium carbonate allows investigation associated mineral’s effect on properties geopolymeric materials. To achieve these purposes, several experimental techniques were used, n...

Attention has been focused recently on the use of Moroccan black oil shale as the raw material for production of a new type of adsorbent and its application to U and Th removal from contaminated wastewaters. The purpose of the present work is to provide a better understanding of the composition and structure of this shale and to determine its natural content in uranium and thorium. A black shal...

X-ray phase analysis of clays is difficult because these materials generally consist of a mixture of different phases, i.e., mixed-layer minerals, individual clay minerals (non mixed-layer), and associated minerals, such as calcite and quartz. The analysis requires knowledge that presently is incorporated in a computer-based expert system. This expert system is capable of a) identification of a...

Soils often show supersaturation with respect to calcite. This study was undertaken to test alternative methods of measuring Ca2+ and COjactivities to assess their effects on measured ion-activity products (IAP) of calcite in soils. Soils were reacted with atmospheric CO,(g) and distilled H 2 0 for 1,3, and 7 d. The soil extracts were analyzed for pH, electrical conductivity (EC), cations, anio...

The geochemical composition of foraminiferal tests is a valuable archive for the reconstruction of paleo-climatic, -oceanographic and -ecological changes. However, dissolution of biogenic calcite and precipitation of inorganic calcite (overgrowth and recrystallization) at the seafloor and in the sediment column can potentially alter the original geochemical composition of the foraminiferal test...

The evolution of fluid chemistry and mineral alteration around a potential waste emplacement tunnel (drift) is evaluated using numerical modeling. The model considers the flow of water, gas, and heat, plus reactions between minerals, CO(2) gas, and aqueous species, and porosity-permeability-capillary pressure coupling for a dual permeability (fractures and matrix) medium. Two possible operating...