The Elements of economic geology

Bibliographic data

Monograph

Identifikator:: 1773832379

URN:: urn:nbn:de:zbw-retromon-172798

Document type:: Monograph

Author:: Gregory, John W. http://d-nb.info/gnd/11683014X

Title:: The Elements of economic geology

Place of publication:: London

Publisher:: Methuen

Year of publication:: 1928

Scope:: XIV, 312 S.; graph. Darst.

Digitisation:: 2021

Collection:: Economics Books

Usage license:: Get license information via the feedback formular.

Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part III. Earthy minerals

Collection:: Economics Books

BUILDING STONES AND ROAD METALS 177 equal to the blow of a ten-ton hammer per square inch of surface. Repeated variations of temperature in a rock of which the constituents expand unequally when heated produce cracks parallel to the surface; this ** spalling” in the tropics breaks granite into thin slabs, and they peel off leaving dome-shaped hummocks. Spalling is in some countries used in quarrying ; as the sudden chilling by water of a hot rock surface breaks it into slabs; their thickness varies with the treatment. Stones are also attacked by organic agencies. Bacteria contribute largely to the decay of rock debris into soil, and they doubtless also affect building stones. A block of stone may suddenly decay at one point; if unchecked the process will spread like an infection, but it may be stopped if the decayed material be removed and the part sterilized. Tests oF BuiLping StoNe—The test of the durability of building stone most often used is the crushing strength; rectangular blocks 2 inches square by 3 inches high, are crushed by a machine which records the breaking pressure. Weaker stones are tested in 4-inch or 6-inch cubes. The value of this test is in the main indirect, for practically all stones withstand much higher pressure than they are subject to in buildings. The crushing strength of granites is from 850 to 1300 tons per square foot; of sandstone from 200- 1000 tons; of limestone from 100-1000 tons, and dolomites from 300-600 tons. In an ordinary building no stone is sub- ject to a greater load than about 10-12 tons per square foot; the greatest load in the Washington Monument, which is 555 feet high, is only 22-26 tons per square foot. Stones that best resist crushing generally best resist weathering. The value of this test is lessened by its variability; the crushing load may vary 30 to 40 per cent. in material from the same quarry, and great variation may occur in samples cut from the same block. The resistance to shearing, which is especially important in building material, is tested by a rod pressing against samples of a standard size of 6 inches by 4 inches by 2 inches. Granite has a resistance to shearing of from 65 to 200 tons per square foot, sandstone from 65-85 tons per sq. foot, and marble about 100 tons per square foot. The tensile strength is usually about one-fifth of the 12

Access restriction

Copyright

fullscreen: The Elements of economic geology

Monograph

Chapter

Table of contents

Download

Monograph

Chapter

This page

Image fragment

Citation links

Citation recommendation