Calcareous materials

Because calcium oxide comprises about 65% of Pordand cement, these plants are frequendy situated near the source of their calcareous material. The requisite silica and alumina may be derived from a clay, shale, or overburden from a limestone quarry. Such materials usually contain some of the required iron oxide, but many plants need to supplement the iron with mill scale, pyrite cinders, or iron ore. Silica may be supplemented by adding sand to the raw mix, whereas alumina can be furnished by bauxites and Al202-rich flint clays. 

Clays composed of mixtures of clay minerals having from 20—50% of unsorted fine-grain nonclay materials are most satisfactory. Large amounts of iron, alkaHes, and alkaline earths, either in the clay minerals or as other constituents, cause too much shrinkage and greatiy reduce the vitrification range thus, a clay with a substantial amount of calcareous material is not desirable. Face bricks, which are of superior quaHty, are made from similar materials but it is even more desirable to avoid these detrimental components (see Building materials, survey). 

The calcareous materials contain calcium carbonate or calcium oxide. Typical raw calcareous materials are as follows ... 

Five E-W and N-S transects were selected for the GPR survey. These were located below the flanks of a low hill strewn with silcrete and silicified weathered bedrock cobbles and gravels. Previous limited drilling indicated that the thickness of exotic sandy cover was about 5 m and that calcareous materials may be patchily distributed. 

Loss of NHj from calcareous subsurface media is considerably greater than from noncalcareous media and involves production of (NH )3C03 or NH HCOj The fate of (NH )jSO added to calcareous material is expressed by the reaction between (NH )3S0 and CaCOj, and as a result, volatile ammonia is produced according to the equation... 

Brokerhof, A.W. and van Bommel, M. (1996) Deterioration of calcareous materials by acetic acid vapour a model study. Preprints of the 11th Triennial Meeting of the International Committee for Conservation ICOM-CC, Edinburgh, UK, Vol. 2, pp. 769-75. 

Bamboo corals can be identified by the occasional, dark brown, gorgonin nodes that regularly intersperse the calcareous material, dividing the branches into sections (Figs 11.11 and 11.12). 

PORE-SCALE COMPLEXITY OF A CALCAREOUS MATERIAL BY TIME-CONTROLLED MERCURY POROSIMETRY... 

Pore-scale complexity of a calcareous material by time-controlled mercury porosimetry... 

Marble and limestone surfaces were exposed to atmospheric conditions at four eastern U.S. sites and were monitored for changes in surface chemistry, surface roughness/re-cession, and weight. The effect of acid deposition, to which calcareous materials are especially sensitive, was of particular interest. Results are described for the first year of testing, and aspects of a preliminary equation to relate damage to environmental factors are discussed. Thus far, findings support that acid deposition substantially damages marble and limestone surfaces. 

Also called hardpan an opaque, reddish-brown-to-white calcareous material, which occurs in layers near the surface of stony soils in arid and semiarid areas. 

Mention type of calcareous material if identified. Examples Foram calcareous ooze (Ca Oz) and nannofossil calcareous ooze (Ca Oz)... 

At present there is no engineering method that is specifically capable of classifying calcareous materials. A variety of parameters have been proposed to characterize the engineering properties of marine carbonate sediments, refer to Table 7.5. Some of these characteristics are listed as follows ... 

In general, it appears that all the above methods taken together provide an excellent means of characterizing a calcareous material. In a similar fashion, engineers might use several existing classification systems to adequately characterize the properties, behavior, and expected performance of calcareous soils, since it is unlikely that any single system will perform all of these functions. 

Skin friction was shown by Nauroy and Le Tirant (1983) to be less for calcareous sands as compared to siliceous sands. The skin friction available for calcareous materials decreased as the compressibility of the materials increased as shown in Figure 10.11. In addition, the skin friction of closed-ended model piles was also shown not to be greatly affected by the increasing confining pressure (Nauroy and Le Tirant, 1983). 

Rendzinas (E) Other soils having a mollic A horizon which contains or immediately overlies calcareous material with a calcium carbonate equivalent of more than 40% (when the A horizon contains a high amount of finely divided calcium carbonate the color requirements of the mollic A horizon may be waived) ... 

The patented process (European Patent N° 8410186) on which the K-TECH process is based consists in producing an active synthetic base through thermal activation under controlled atmosphere of clayed-calcareous material of specific composition and in producing hydrauhc binder by mixing that base with Portland cement clinker or other activators. 

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