Evolution of Nervous Control from Primitive Organisms to Man A Symposium organized by the Section on Medical Sciences of the American Association for the Advancement of Science, and presented at the New York Meeting on December 29–30, 1956. Edited by Allan D. Bass. Pp. vii + 231. (Washington, D.C.: American Association for the Advancement of Science; London: Bailey Bros. and Swinfen, Ltd., 1959.) 52s.

The Central Nervous System

Porous Materials Water in Porous Materials Flow in Porous Materials Unsaturated Flows Unsaturated Flow in Building Physics Composite Materials Evaporation and Drying Topics in Water Transport Appendices Symbols Used Properties of Water Minerals, Salts and Solutions Other Liquids Other Data

Water Transport in Brick, Stone and Concrete

Mineralogical, textural and chemical analyses of clay-rich materials following firing, evidence that initial mineralogical differences between two raw materials (one with carbonates and the other without) influence the tex- tural and mineralogical evolution of the ceramics as T increases from 700 to 1100° C. Mineralogical and textural changes are interpreted considering local marked disequilibria in a system that resembles a small-scale high- T meta- morphic process ( e.g., contact aureoles in pyrometamorphism). In such conditions, rapid heating induces significant overstepping in mineral reaction, preventing stable phase formation and favoring metastable ones. High- T transfor- mations in non-carbonate materials include microcline structure collapse and/or partial transformation into sanidine; and mullite plus sanidine formation at the expenses of muscovite and/or illite at T ‡ 800° C. Mullite forms by mus- covite-out topotactic replacement, following the orientation of mica crystals: i.e., former (001) muscovite are ^ to (001)mullite. This reaction is favored by minimization of free energy during phase transition. Partial melting followed by fingered structure development at the carbonate-silicate reaction interface enhanced high- T Ca (and Mg) silicates formation in carbonate-rich materials. Gehlenite, wollastonite, diopside, and anorthite form at carbonate-silicate interfaces by combined mass transport (viscous flow) and reaction-diffusion processes. These results may add to a better understanding of the complex high- T transformations of silicate phases in both natural ( e.g., pyrometamor- phism) and artificial ( e.g., ceramic processing) systems. This information is important to elucidate technological achievements and raw material sources of ancient civilizations and, it can also be used to select appropriate clay com- position and firing temperatures for new bricks used in cultural heritage conservation interventions.

https://hera.ugr.es/doi/15010478.pdf?origin=publication_detail

Carbonate and silicate phase reactions during ceramic firing

The changes in brick porosity upon firing (700 up to 1100 � C) and its relation to the mineralogical composition are examined. Two types of raw clay with a composition representative of that used in brick-making industry were selected to manufacture the bricks: one contains notable amounts of carbonates, with a grain size of under 1 mm, and the other is predominantly quartzitic and lacking in carbonates. We demonstrate that the presence or absence of carbonates strongly influences the porosity development and, therefore, the brick texture and physical-mechanical properties. The carbonates in the raw clay promote the formation of fissures and of pores under 1 mm in size when the bricks are fired between 800 and 1000 � C. The absence of carbonates results in a continuous reduction in porosity and a significant increase in the pore fraction with a radius (r) > 1 mm as the firing temperature rises and smaller pores coalesce. Porosity and pore size distribution results obtained from the combined use of hydric tests (HT), mercury intrusion porosimetry (MIP) and digital image analysis (DIA) of scanning electron microscopy photomicrographs are compared. A clear correlation between the water absorption and drying behaviour of the bricks and the porosity plus pore size distribution is observed. DIA discloses the evolution of size, shape and connectivity of macropores (r > 1 mm) and evidences that MIP results underestimate the macropore content. Conversely, MIP gives a good estimate of the open porosity and of the distribution of pores with r <1 mm. It is concluded that the combined use of these complementary techniques helps to fully characterise the pore system of bricks. These results as well as the study of the evolution of the speed of ultrasound waves vs. time yield useful information to evaluate the bricks physical–mechanical behaviour and durability. The relevance of these findings in the conservation of historic buildings is discussed. # 2003 Elsevier Ltd. All rights reserved.

Influence of mineralogy and firing temperature on the porosity of bricks

1 Archaeology, archaeological science and microarchaeology 2 Information embedded in the microscopic record 3 Completeness of the archaeological record 4 Common mineral components of the archaeological record 5 Biological materials: bones and teeth 6 Biological materials: phytoliths, diatoms, eggshells, otoliths and mollusk shells 7 Reconstructing pyrotechnological processes 8 Biological molecules and macromolecules: protected niches 9 Ethnoarchaeology of the microscopic record: learning from the present 10 Absolute dating: assessing the quality of a date 11 Reading the microscopic record on-site 12 Infrared spectroscopy in archaeology

Microarchaeology: Beyond the Visible Archaeological Record

An approach to the dynamics of clay firing

Firing process of natural clays. Some microtextures and related phase compositions

Thermal, microscopic and X-ray diffraction studies on some ancient mortars

Glass finds from the Medieval Val Gargassa glasshouse (Genova, Italy) were investigated by chemical and spectroscopic techniques (colorimetric analysis and X-ray absorption spectroscopy) with the aim to obtain information on the ancient glass production technique. Sampling covers all the typologies of archaeological findings unearthed by the digging, as well as fragments of finished glass-wares. The results indicated that the samples are soda-lime based glasses. The color variability was exerted by the glassmakers by both controlling the kiln atmosphere and/or adding MnO2 as decoloring agent. In both cases, the Fe2+/Fe3+ ratio was modified at a specific step of the production cycle.

Maria Pia Riccardi

Papers

An approach to the dynamics of clay firing

Firing process of natural clays. Some microtextures and related phase compositions

Thermal, microscopic and X-ray diffraction studies on some ancient mortars

The ancient glass production of the Medieval Val Gargassa glasshouse: Fe and Mn XANES study

Metakaolin as a precursor of materials for applications in Cultural Heritage: Geopolymer-based mortars with ornamental stone aggregates.