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Measurement of elastic strains in concrete structures
Nov., 1928.]
U.
S.
B U R E A U OF STANDARDS NOTES.
697
September 14 and September 29 , I928, the a u t u m n a l equinox period. At certain times on four different days the natural and artificial daylight were in practically perfect color match. At other times the natural daylight was slightly yellowish, purplish, or bluish, relative to the standard. S t a n d a r d artificial daylight is thus available, accurately reproducible from specification, and m a y be readily prepared in any laboratory. T h e specifications of this filter are sifiailar to those of other Davis-Gibson filters. T h e exact proportions of the ingredients are as follows: A. Copper sulphate (CuSO4.5H20) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mannite (C6Hs(OH)8) Pyridine (C~HsN) Water (distilled) to make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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B. Cobalt ammonium sulphate (COSO4. (NH4)~SO4.6H~O) . . . . . . . . . Copper sulphate (CuSO,.sH20) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sulphuric acid (Sp. gr. 1.835) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Water (distilled) to make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.125 3.125 30.0 IOOO.O
grams grams ml. ml.
25.470 25.000 IO.O IOOO.O
grams grams ml. ml.
One centimeter of each of solutions A and B are contained in a double cell having three plates of borosilicate crown glass (refractive index, D line = 1.51) each 2. 5 mm. thick. Complete spectrophotometric d a t a will be sent upon request. M E A S U R E M E N T OF ELASTIC STRAINS IN CONCRETE STRUCTURES.
a TEST has been made recently to determine the practicability of a m e t h o d which could be used in field tests of concrete structures, for distinguishing between the elastic strains produced by stress and those resulting from changes in t e m p e r a t u r e and h u m i d i t y and from plastic flow or yield. In this m e t h o d small blocks of concrete are cut out of the structure, measurements are made of the elastic recovery which takes place in these blocks as they are relieved from the forces acting when in the mass. T h e changes in strain accompanying the removal of the blocks were determined readily by means of a hand strain gauge. To facilitate the removal of the blocks it was suggested t h a t each should be cast in a U-shaped trough or form. T h e principal object
698
U . S . BUREAU OF STANDARDS NOTES.
[J. F. I.
of the test was to determine whether the presence of the form material would appreciably affect the strains in the block and whether the block could be cut out without injury to the gauge lines. A concrete prism 3o by 3o inches in cross section and 36 inches in height was made for the test. The prism contained one removable block near the mid-point of each of the four lateral faces. Each block was in the form of a prism 5 by 5 inches in cross section and 2o inches in height. One of the forms for shaping the blocks was made of sheet metal about .o3 inch in thickness. The other three were made of wall board of three different thicknesses. All were given a thin coat of paraffin to prevent bonding with the concrete. Plugs were set in the concrete for use in taking strain gauge readings in three gauge lines on each lateral face of the prism, one gauge line being in the removable block and the other two midway between the edges of the block and the prism. The prism was placed in a testing machine and a compressive load of 6oo lbs./in 2. applied. After taking strain readings one of the blocks was removed by cutting the concrete along each end of the block. Although this required a cut about 5 inches in length and 5 inches in depth along each end of the block these were made easily with a small air drill. The load on the prism was then released and strain gauge readings were made. The same operation was followed in removing another block from the prism. The results of the tests indicate that the blocks, when separated (except at the ends) from the prism by thin forms, were cut out without a noticeable injury to the gauge lines. It was found, however, that the strain in the block cast into the sheet steel form was only about 7o per cent. of the average strain in the adjacent gauge lines, whereas for the blocks cast into wall board forms the strains were on the average about 3o per cent. greater than in the adjacent concrete. These results indicate that some provision should be made when using metal forms to prevent the steel form taking such an appreciable amount of stress as to affect the strain in the concrete block. They show further that wall board on account of its greater thickness and lack of rigidity is not a suitable material for such forms. Apparently, the method
Nov., 1928.1
U.
S.
BUREAU
699
OF S T A N D A R D S N O T E S .
can be made practicable for separating the elastic from the inelastic strains measured in concrete. REPORT OF S T A N D A R D ZETTLITZ KAOLIN TEST.
A'r its Copenhagen meeting, the International Union of Pure and Applied Chemistry voted to undertake the preparation and distribution of an international standard sample of Zettlitz kaolin and charged the Ceramic Society of CzechoSlovakia with the duty of carrying out this resolution. This society established a permanent committee to prepare, distribute, and to act as custodian for this standard sample. Samples of this standard may be secured by application to The Ceramic Society of Czecho-Slovakia, Prague, CzechoSlovakia. Samples of this standard have been distributed to the countries belonging to the Union for analysis and test, and it is hoped that a comparative study of the results obtained will lead eventually to the adoption of international methods for the analysis and testing of clays for ceramic purposes. The present report contains the results obtained in the study of the standard kaolin at the Bureau of Standards made in accordance with the methods adopted by the American Ceramic Society and also other methods in use at the bureau. CHEMICAL ANALYSIS. Silica (Si02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alumina (A1203) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ferric oxide (Fe~03) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P h o s p h o r o u s pentoxide (P~O~) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Titania (Ti02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zirconia (ZrO~) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Manganese oxide (MnO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Calcium oxide (CaO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M a g n e s i u m oxide (MgO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B a r i u m oxide (BaO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S t r o n t i u m oxide (SrO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chromic oxide (Cr203) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V a n a d i u m trioxide (V203) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P o t a s s i u m oxide (K~O) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sodium oxide (Na~O) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S u l p h u r trioxide (SO,) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Loss on ignition (lO5O-11oo ° C.) . . . . . . . . . . . . . . . . . . . . . . . . . . . Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Per Cent. 46.9o 37.4o 65 08 18 oo7 007 29 27 02 0o6 o15 0o2 84 44 03 12.95 lOO.O87
U.
S.
B U R E A U OF STANDARDS NOTES.
697
September 14 and September 29 , I928, the a u t u m n a l equinox period. At certain times on four different days the natural and artificial daylight were in practically perfect color match. At other times the natural daylight was slightly yellowish, purplish, or bluish, relative to the standard. S t a n d a r d artificial daylight is thus available, accurately reproducible from specification, and m a y be readily prepared in any laboratory. T h e specifications of this filter are sifiailar to those of other Davis-Gibson filters. T h e exact proportions of the ingredients are as follows: A. Copper sulphate (CuSO4.5H20) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mannite (C6Hs(OH)8) Pyridine (C~HsN) Water (distilled) to make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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B. Cobalt ammonium sulphate (COSO4. (NH4)~SO4.6H~O) . . . . . . . . . Copper sulphate (CuSO,.sH20) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sulphuric acid (Sp. gr. 1.835) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Water (distilled) to make . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.125 3.125 30.0 IOOO.O
grams grams ml. ml.
25.470 25.000 IO.O IOOO.O
grams grams ml. ml.
One centimeter of each of solutions A and B are contained in a double cell having three plates of borosilicate crown glass (refractive index, D line = 1.51) each 2. 5 mm. thick. Complete spectrophotometric d a t a will be sent upon request. M E A S U R E M E N T OF ELASTIC STRAINS IN CONCRETE STRUCTURES.
a TEST has been made recently to determine the practicability of a m e t h o d which could be used in field tests of concrete structures, for distinguishing between the elastic strains produced by stress and those resulting from changes in t e m p e r a t u r e and h u m i d i t y and from plastic flow or yield. In this m e t h o d small blocks of concrete are cut out of the structure, measurements are made of the elastic recovery which takes place in these blocks as they are relieved from the forces acting when in the mass. T h e changes in strain accompanying the removal of the blocks were determined readily by means of a hand strain gauge. To facilitate the removal of the blocks it was suggested t h a t each should be cast in a U-shaped trough or form. T h e principal object
698
U . S . BUREAU OF STANDARDS NOTES.
[J. F. I.
of the test was to determine whether the presence of the form material would appreciably affect the strains in the block and whether the block could be cut out without injury to the gauge lines. A concrete prism 3o by 3o inches in cross section and 36 inches in height was made for the test. The prism contained one removable block near the mid-point of each of the four lateral faces. Each block was in the form of a prism 5 by 5 inches in cross section and 2o inches in height. One of the forms for shaping the blocks was made of sheet metal about .o3 inch in thickness. The other three were made of wall board of three different thicknesses. All were given a thin coat of paraffin to prevent bonding with the concrete. Plugs were set in the concrete for use in taking strain gauge readings in three gauge lines on each lateral face of the prism, one gauge line being in the removable block and the other two midway between the edges of the block and the prism. The prism was placed in a testing machine and a compressive load of 6oo lbs./in 2. applied. After taking strain readings one of the blocks was removed by cutting the concrete along each end of the block. Although this required a cut about 5 inches in length and 5 inches in depth along each end of the block these were made easily with a small air drill. The load on the prism was then released and strain gauge readings were made. The same operation was followed in removing another block from the prism. The results of the tests indicate that the blocks, when separated (except at the ends) from the prism by thin forms, were cut out without a noticeable injury to the gauge lines. It was found, however, that the strain in the block cast into the sheet steel form was only about 7o per cent. of the average strain in the adjacent gauge lines, whereas for the blocks cast into wall board forms the strains were on the average about 3o per cent. greater than in the adjacent concrete. These results indicate that some provision should be made when using metal forms to prevent the steel form taking such an appreciable amount of stress as to affect the strain in the concrete block. They show further that wall board on account of its greater thickness and lack of rigidity is not a suitable material for such forms. Apparently, the method
Nov., 1928.1
U.
S.
BUREAU
699
OF S T A N D A R D S N O T E S .
can be made practicable for separating the elastic from the inelastic strains measured in concrete. REPORT OF S T A N D A R D ZETTLITZ KAOLIN TEST.
A'r its Copenhagen meeting, the International Union of Pure and Applied Chemistry voted to undertake the preparation and distribution of an international standard sample of Zettlitz kaolin and charged the Ceramic Society of CzechoSlovakia with the duty of carrying out this resolution. This society established a permanent committee to prepare, distribute, and to act as custodian for this standard sample. Samples of this standard may be secured by application to The Ceramic Society of Czecho-Slovakia, Prague, CzechoSlovakia. Samples of this standard have been distributed to the countries belonging to the Union for analysis and test, and it is hoped that a comparative study of the results obtained will lead eventually to the adoption of international methods for the analysis and testing of clays for ceramic purposes. The present report contains the results obtained in the study of the standard kaolin at the Bureau of Standards made in accordance with the methods adopted by the American Ceramic Society and also other methods in use at the bureau. CHEMICAL ANALYSIS. Silica (Si02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alumina (A1203) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ferric oxide (Fe~03) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P h o s p h o r o u s pentoxide (P~O~) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Titania (Ti02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zirconia (ZrO~) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Manganese oxide (MnO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Calcium oxide (CaO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M a g n e s i u m oxide (MgO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B a r i u m oxide (BaO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S t r o n t i u m oxide (SrO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chromic oxide (Cr203) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V a n a d i u m trioxide (V203) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P o t a s s i u m oxide (K~O) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sodium oxide (Na~O) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S u l p h u r trioxide (SO,) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Loss on ignition (lO5O-11oo ° C.) . . . . . . . . . . . . . . . . . . . . . . . . . . . Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Per Cent. 46.9o 37.4o 65 08 18 oo7 007 29 27 02 0o6 o15 0o2 84 44 03 12.95 lOO.O87