Radiation effects in calcite

Direct Experimental Evidence for Differing Reactivity Alterations of Minerals following Irradiation: The Case of Calcite and Quartz

“…On the other hand, calcite, which shows no change in n c , independent of radiation exposure, correspondingly shows little, if any change in its dissolution rate. The slight reduction that manifests in calcite dissolution rates, for irradiated calcite, is likely due to: (a) rapid dissolution of the surface exposed to solution such that distortions of CO 3 2− groups, may render their removal easier, or (b) may be related to observations of a slight increase in calcite hardness, and hence stability following irradiation 29 56 . If the former mechanism is operative, facilitated surface dissolution (i.e., an increase in the CO 3 2− abundance in the solution, in proximity to the dissolving surface) would lower the driving force for calcite dissolution, an effect which would slightly reduce its dissolution rate (see Fig.…”

“…Such mechanical damage resulting from expansion of the aggregates affects the structural properties of the concrete far more dramatically than direct irradiation effects on the cement paste itself. The effects of radiation damage on quartz and calcite (i.e., common minerals in aggregates in concrete) have been described in terms of changes in physical properties, such as density, optical properties, hardness, conductivity, etc 28 29 30 . Of these, volume change is thought to be prominent in quartz, but less significant for calcite even for neutron fluence reaching 1.0 × 10 20 n/cm 2 (E > 0.1 MeV) 31 32 .…”

The effect of irradiation on the atomic structure and chemical durability of calcite and dolomite

“…This is why radiation damage in carbonates, even if induced, presents a reversible character. 32 The resistance to irradiation-induced structural alteration is controlled by the competition between covalent and ionic bonds in the system, and the ability for a structure to recrystallize to its thermodynamically most favored state depends mostly on its ionic nature. Conversely, recrystallization is hindered in structures that are covalently bonded, whose directional character inhibit structural reorganizations, thereby retaining structural defects.…”

“…This is postulated to be on account of ion implantation, at the energies and fluence implemented herein inducing the reorganization of existing dislocations in the crystal structure in an effect similar to annealing, 31 which would result in a consequent reduction in the dissolution rate (and elsewhere, has been observed to result in an increase in calcite's hardness). 32,33 This effect is more prominent in the case of calcite, i.e., rather than dolomite on account of the calcite being a pure and oriented single crystal as compared to the natural dolomite sections. In the case of dolomite, irradiation appears to impose no effect on its dissolution rate.…”

“…Thus, it can be concluded that irradiation affects carbonate mineral dissolution rates in a much more limited manner than observed for silicates. 32,34 For example, quartz, albite, and almandine have shown increases in their dissolution rate upon irradiation by a factor of 1000 times, 20 times, and 2 times, respectively. 7,9,10 Effect of irradiation on the atomic structure of carbonate minerals Irradiation can significantly affect the crystal structure of minerals by altering: (i) coordination numbers, (ii) bond lengths, (iii) bond angles, and/or (iv) their medium-range order.…”