The GEOCISTEM project was focussed to look for an inexpensive natural glassy alkaline substitute of chemical reagents used in a trade registered cement. A complete survey for european resources made up for fragmentary (pyroclastic) alkali-rich glassy volcanic rocks (Na 2O+K 2O > 10 %, K>>Na) was done in several european volcanic regions (in Italy, Greece and Spain). Up to 100 samples were analysed (main constituents by XRF; petrographic and XRD characterisation) and 10 of them were used in the developing of a silicate-based cement (laboratory and semi-industrial scale).The result was a set (ten) of cements characterised by high compressive strength of the plain cement phase (50-60 MPa after 28 days), with high resistance to chemical corrosion and non alkali-silica-aggregate reaction, very indicated for toxic waste encapsulation. Furthermore a great economy in energy and a significant reduction of K-silicate consumption (up to 1/3-1/4 of the formulation in the original trade registered cement) in the process of production was achieved. The chemical-mineralogical study carried out shows that the original formulation of the cement was too restrictive, as well as that the mineralogy reached during natural devitrification processes in the rock strictly controls the performance of this new european resource during the development of the cement. The anhidrous rocks mainly constituted by alkali feldspars and silica crystalline phases (obtained by devitrification at temperatures under magmatic ones) are more interesting than the zeolitised ones, allowing to skip the calcination process and thus providing energetic economy
Desarollo de un cemento de base silicatada a partir de rocas volcanicas vitreas alcalinas: interpretation de lor resultados preindustriales basada en la composicion quimico-mineralogica de los precursores geologicos
Cara S;
2003
Abstract
The GEOCISTEM project was focussed to look for an inexpensive natural glassy alkaline substitute of chemical reagents used in a trade registered cement. A complete survey for european resources made up for fragmentary (pyroclastic) alkali-rich glassy volcanic rocks (Na 2O+K 2O > 10 %, K>>Na) was done in several european volcanic regions (in Italy, Greece and Spain). Up to 100 samples were analysed (main constituents by XRF; petrographic and XRD characterisation) and 10 of them were used in the developing of a silicate-based cement (laboratory and semi-industrial scale).The result was a set (ten) of cements characterised by high compressive strength of the plain cement phase (50-60 MPa after 28 days), with high resistance to chemical corrosion and non alkali-silica-aggregate reaction, very indicated for toxic waste encapsulation. Furthermore a great economy in energy and a significant reduction of K-silicate consumption (up to 1/3-1/4 of the formulation in the original trade registered cement) in the process of production was achieved. The chemical-mineralogical study carried out shows that the original formulation of the cement was too restrictive, as well as that the mineralogy reached during natural devitrification processes in the rock strictly controls the performance of this new european resource during the development of the cement. The anhidrous rocks mainly constituted by alkali feldspars and silica crystalline phases (obtained by devitrification at temperatures under magmatic ones) are more interesting than the zeolitised ones, allowing to skip the calcination process and thus providing energetic economyI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
