Micro-topographic change on calcarenites,grand Cayman Island,West Indies

Changes in micro-topography, as a result of varying erosion rates, have been monitored on a calcarenite ridge on Grand Cayman Island, West Indies, using a traversing model of the micro-erosion meter. Erosion takes place through the solution of a calcitic cement and ‘solutional disintegration’ results in a rapid change of micro-relief. Where a protective crust is present, surface lowering is slower and also more uniform; thus the original relative relief is maintained.     

Application of the needle penetration test to a calcarenite, Maastricht, the Netherlands

In this paper, first, the needle penetrometer test is briefly presented and experience gained, mainly in Japan and Turkey, with a model manufactured in Japan is reviewed. Second, the needle penetrometer test is used successfully to distinguish qualitatively carbonate sands from very weak and weak calcarenites in borehole cores recovered for cut-and-cover tunnel projects in Maastricht. Third, the relation between UCS and needle penetration resistance (NPR) for the Maastrichtian limestones is further analyzed. Needle penetration tests are conducted with the help of a loading frame. Results suggest that there is a statistically significant relationship between the UCS and NPR, that leaves however to high predictive uncertainty. During testing, very high compressive and shear stresses develop under the needle and stresses normal to the needle shaft increase. Microscopic observations show the extent of grain crushing and compaction ahead and around the needle. Nevertheless, resistance to needle penetration and UCS values are somehow related. The needle penetrometer is recommended as an index test rather than a way to determine accurately the UCS of the Maastrichtian limestones.     

Superficial alteration and soluble salts in the calcarenite weathering. case study of almohade monuments in Rabat: Morocco

This work analyzes the stone superficial deterioration of some monuments in Rabat city. The rock is a calcarenite with porous texture, rich in calcium carbonates and fossils. The techniques used to study the surfaces altered by blackening or black crusts, are the SEM equipped with EDX microprobe, the X-ray diffraction, and the analysis of the soluble salts by ionic chromatography for anions and flame spectrometer for cations. They reveal significant contents of calcium sulphates, mainly gypsum, often associated with sodium chlorides. These salts known to have a destructive effect on the calcareous stones seem to be originated from the contamination by atmospheric pollutants, particularly sulfur dioxide, and by the marine sprays.