Assessment of technological properties of calcareous and non-calcareous clays used for the brick-making industry of Zaragoza (Spain)
The granulometric, mineralogical, and geochemical features of two different types of clayey raw materials (carbonated clays, CC; and non-carbonated clays, NCC) used for the brickmaking industry near Zaragoza (Spain) have been studied. Their particle-size distribution suggests that they may be classified as silty clays and are suitable for use as thin-walled hollow bricks. For technological testing, prismatic bars obtained by extrusion under vacuum conditions from raw materials were fired from 800 to 1050 °C. Technological determinations, such as linear shrinkage, bulk density, hydric tests, and an accelerated decay test, indicate that both CC and NCC are suitable to be used as bricks for building, although bricks made of NCC would be of better quality. In addition, pore-size distribution suggests that the durability of the highest temperature fired products will be higher because of an increase both in the dominant pore access radius and in the percentage of larger pore sizes.
Clay materials for ceramic tiles from the Sassuolo District (Northern Apennines, Italy). Geology, composition and technological properties
Abstract In the Sassuolo area (northern Italy) there is the largest tilemaking district in the world, which has practically served over the past years as an industrial scale laboratory for assessing the technological properties of clays and their suitability for the production of wall and floor tiles. The local clays are recovered from different geological units and distinguished in two principal types, with clearly differentiated compositions and technological properties: “marly clays” and “red shales”. These local clays, which 20 years ago constituted the sole mineral resource of the Sassuolo District, now supply only 40% of the demand. This trend is largely connected with both process innovation (wet grinding, fast firing, etc.) and product changes (from red to white bodies). Overall, approximately 2 million tpa of clay materials are used in coloured bodies: marly clays for wall tiles (majolica, “birapida”, “monoporosa”) and red shales for both floor tiles (glazed red stoneware) and wall tiles (“monoporosa”).
Quantitative interpretation of mineralogical composition from X-ray and chemical data for the Pierre Shale
-----------------------------------------Introduction.-------------------------------------X-ray analysis ________ --_--_--_----_________ ------Sample preparation and treatment _______________ _ Interpretation---------------------------------Whole rock data ___________________________ _ Carbonate minerals.--------_____ -----_ Disordered cristobalite _________________ _ Total clay minerals __ -------__________ _ Clay fraction data_------------__ ------__ _ Clay minerals present __ ----------------Comparison of X-ray peak sizes _________ _ Estimation of kaolinite and chlorite ______ _ Examples of interpretation __________________ _ ReproducibilitY------------------------------------Long-term reproducibility----__________________ _ Accuracy-comparison with chemical analyses _________ _ Sulfide, sulfate, and carbonate minerals ___________ _ Page