noun
definition
A type of volcanic ash used for mortar or for cement which sets under water.
Examples of pozzolana in a Sentence
The igneous formation of which the greater part of the Roman Campagna is, in its superior portion, composed, contains three strata known under the common name of tufa, - the " stony," " granular," and " sandy " tufa, - the last being commonly known as pozzolana.
Lava is much used for paving-stones in the neighborhood of volcanic districts, where pozzolana (for cement) and pumice stone are also important.
The mineral wealth of the Cyclades has hitherto been much neglected; iron ore is exported from Seriphos, manganese and sulphur from Melos, and volcanic cement (pozzolana) from Santorin.
According to modern physicians it is impossible to live many days in the caves of pozzolana in which many of the catacombs are excavated."
C. i is on the earliest dwellings of man; C. 2 on systems of Thales, Heraclitus, Democritus, &c.; c. 3 on bricks; c. 4 on sand; c. 5 on lime; c. 6 on pozzolana; c. 7 on kinds of stone for building; c. 8 on methods of constructing walls in stone, brick, concrete and marble, and on the materials for stucco; c. 9 on timber, time for felling it, seasoning, &c.; and c. to on the fir trees of the Apennines.
The matter transported consisted of soil of various kinds - sand, ashes, fragments of lava, pozzolana and whitish pumice, enclosing grains of uncalcined lime, similar in every respect to those of Pompeii.
In the part of Herculaneum already excavated the corridors in the upper portions of the theatre are compactly filled, up to the head of the arches, with pozzolana and pumice transformed into tufa (which proves that the formation of this stone may take place in a comparatively short time).
Its mineral baths are frequented in summer; and the volcanic pozzolana earth (also found near Rome), used now as in Roman times for making cement and concrete, derives its name from the place.
In the older districts there is a countless variety of narrow gloomy streets, many of them steep. The houses are mostly five or six storeys high, are covered with stucco made of a kind of pozzolana which hardens by exposure, and have large balconies and flat roofs.
In 1866 primitive structures were discovered in the island of Therasia by quarrymen extracting pozzolana for the Suez Canal works; and when this discovery was followed up in 1870, on the neighbouring Santorin (Thera), by representatives of the French School at Athens, much pottery of a class now known immedi ately to precede the typical late Aegean ware, and many stone and metal objects, were found and dated by the geologist Fouque, somewhat arbitrarily, to 2000 B.C., by consideration of the superincumbent eruptive stratum.
Six centuries elapsed before the accidental discovery of a sepulchral chamber by some labourers digging for pozzolana earth (May 31, 1578) revealed to the amazed inhabitants of Rome " the existence," to quote a contemporary record, " of other cities concealed beneath their own suburbs."
Yet it is in this stratum, and in this alone, that the catacombs are constructed; their engineers avoiding with equal care the solid stone of the tufa litoide and the friable pozzolana, and selecting the stratum of medium hardness, which enabled them to form the vertical walls of their galleries, and to excavate the loculi and cubicula without severe labour and also without fear of their falling in.
The strength of the renowned Roman concrete is largely due to the use of pozzolana (see Puteoli), which also is found in plenty in the Campagna.