Geologia, caratterizzazione mineralogico-petrografica, fisico-meccanica e prove di durabilità della pietra serena.

Il capitolo tratta le caratteristiche geologiche, minero-petrografiche, fisico-meccaniche e la durevolezza della pietra serena

Tilmen Hoyuk: petrographic and geochemical investigation on lithic remains from the palace area

Within the Tilmen multidisciplinary project (director N. Marchetti) this paper study the lithological nature of samples, both natural and derived from human activity, collected in the Tilmen Hoyuk site (Turkey

A case study of alkali-silica reactions: petrographic investigation of paving deterioration

Alkali-silica reactions are one of the most common causes of deterioration of concrete. This paper presents a petrographic study of a damaged paving situated in Bologna (North Italy) where alkali silica reactions produced diffused pop-out of cm-sized chips. Siliceous limestone, chert and flint present in the aggregate did not show any reactivity; alkali-silica reactions developed only from fine-grained silica rich marls. Reactive grains show an evident zonation with fractured cores and more compact rims. ASR produced mobilization of alkalies towards the interior of reactive grains coupled with mobilisation of Ca2+ ions wichre-precipitate and react with alkali-silica rich fluids to produce a hard rim. The final effect is the cracking of the grain due to accumulated gels inside. Alkali-silica reactions developed only on the flooring exposed to capillary rise of water. A further proof of the reactivity of these fine-grained marly grains is the late-stage formation on their surface of Na-carbonate

Natural radionuclides content and radiological hazard of commercial ornamental stones: an integrated radiometric and mineralogical-petrographic study.

Twenty samples of natural building materials commonly employed as ornamental stones in the international market have been investigated for natural radioactivity. External (gamma), as defined and used by the European Commission, and internal (alpha) hazard indexes were calculated and radon specific exhalation rate and emanation fraction were measured. The radiological investigation was complemented by an integrated mineralogical-petrographic and rock characterization approach. The most common radioactive accessory minerals occurring in the investigated samples are apatite, zircon and allanite, with minor monazite, thorite, thorianite, REE and Zr-oxides. Significant correlations with total activity concentration have been observed for K2O, Th and Ce concentrations. The emanation fraction is also influenced by both total porosity and porosity distribution. Radon exhalation rate and emanation fraction are very variable ranging from 0.0011 to 0.64 Bq kg1 h1 and from 0.2 to 62%, respectively. Most of the materials have radiological hazard indexes that do not exceed the European Commission limit values when used as ornamental or paving or flooring stones. However, three volcanic (Tufo Giallo Riano, Tufo Grigio Riano and Peperino Viterbese) samples could cause significant exposure both from excess radon indoor concentration (>200 Bq m3) and from gamma radiation (>1 mSv y1) when used as structural materials. This study further indicates that limit values for hazard indexes based on natural activity concentration and Rn emanation should take into account the lithological properties and use of the materials