Russian local government during the war and the Union of Zemstvos

The Elements of economic geology

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Monograph

Identifikator:: 1794855874

URN:: urn:nbn:de:zbw-retromon-179223

Document type:: Monograph

Author:: Polner, Tichon I. http://d-nb.info/gnd/172311195

Title:: Russian local government during the war and the Union of Zemstvos

Place of publication:: New Haven

Publisher:: Yale Univ. Press

Year of publication:: 1930

Scope:: XXV, 317 S.

Digitisation:: 2022

Collection:: Economics Books

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

Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Chapter IX. Relief of refugees

Collection:: Economics Books

ECONOMIC GEOLOGY crushing strength, and indicates durability and resistance to frost. The specific gravity of a building stone shows its weight and its porosity, which is an important factor in durability. Porosity is often expressed by the weight of water absorbed by a stone divided by the dry weight of the stone. The test of soakage in water for 24 hours usually gives too low a poros- ity, as many of the pores are not filled. Soaking for a longer time or under pressure gives more reliable results. The nature of the porosity must also be considered ; for a stone with open pores loses water readily and thus is less likely to be injured by frost. The former test of weakening by freezing was to boil a sample in a saturated solution of sodium sulphate, and hang it up to dry. The crystalliza- tion of the salt breaks off fragments of the stone which are washed, dried, and weighed. In Hirschwald’s method a piece is thoroughly soaked with water and frozen and thawed twenty-five times during a month; the tensile strength of the stone is measured before and after this treatment and the difference is the weakening by freezing. Some rocks are seriously weakened by saturation with water, especially those with a clay cement. This quality may be tested by the ratio of the crushing strengths before and after 28 days’ soaking. This ratio may vary in sandstones from ‘I to ‘0, and no stone in which the ratio is lower than -6 should be used in a damp frosty locality. The tests of building stones have been condemned as valueless because they are little used in British practice, where architects and builders have the experience of centuries to guide them. That much value is attached to the crushing strength may be inferred from its frequent statement in trade advertisements ; and tests are advisable for new stones or new conditions. Building stones which appear of good quality sometimes fail through some unsuspected weakness. The most important practical tests are the crushing strength, the weakening of the cement by water, and the porosity. The weakening by water may be judged roughly by placing a piece of the stone in water for 24 hours, then stirring the water and observing the extent of the muddy streaks which arise from the stone. The porosity can be tested by placing a squared sample on wet blotting paper .78

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