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The cementing qualities of the calcium aluminates
668
U. THE
S. BUREAU OF STI\R.DARDS NOTES.
CEMENTING
QUALITIES
OF THE
[J. F. I.
CALCIUM
ALUMINATES.” By P. H. Bates.
THE four calcium aluminates, 3CaO.A1,0,, 5CaO.3Al,O,, CaO.AI,O,, and 3Ca0.5Al,O,,, which are the only anhydrous compounds of lime and alumina, were prepared in a pure condition by heating together the proper proportion of these compounds. After microscopic examination had shown that homogenous compounds had been formed, the products were finely ground and their cementing qualities when gaged with water were determined. The two compounds higher in lime reacted very energetically with the evolution of much heat, acquiring practically instanhigher in alumina reacted with tanelous set. The two compounds water more like Portland cement, but showed higher strength at earlier periods than the latter. It was thought desirable therefore to prepare these in larger quantities and containing such impurities as silica, iron oxide, and magnesia, which would generally be present in lime and alumina of natural origin. The two compounds CaO.Al,O, and 3Ca0.5Al,O, were consequently burned in a 2 by 20 foot rotary kiln, varying their composition so that the silica, iron oxide, and magnesia reached limits of 17.38, 3.10, and 3.66 per cent., respectively, as maxima in a series of eight cements. The process, of manufacture was entirely similar to that used in the production of Portland cement. The ground cements were used in making the usual small tension and compressive test pieces and 6 by 12 in. gravel concr&e The striking cylinders of I : 1.5 : 4.5 and I : 3 : 9 proportions. feature of the data obtained from testing these at different periods up to and including three years was the very high z4-hour strength. The rich concretes prepared from four of the cements developed in 24 hours strengths in excess of 2800 pounds per square inch, and the lead concretes from two of the cements gavel strengths beyond 1500 lb. at the same period. Consistent gain in strength was obtained up to one year, when one’ of the cements in the rich concrete gave a strength of 8220 pounds per square inch. ’Technologic Paper No. 197.
ITo\,., 1g21.1
U. S. Eu~r~\lu OF STANDARDS NOTES.
669
Test pieces stored in water tended to show retrogression in strength with age. This was also noted with test pieces stored in the damp clos&, but to a much less degree. This action may be explained by the fact that the products of the hydration of all the aluminates are a hydrated 3CaO.A1,0, and hydrated alumina (except in the case of the1 anhydrous 3CaO.A1,0:,, when no hydrated alumina is produced). This latter is the cementing agent in these products, and, being colloidal, it is very susceptible to moisture changes. Large amounts of moisture are taken up in the presence of the latter with consequent swelling of the colloid and reduction in strength.
HOW
TO
GET
BETTER
SERVICE
IN DOMESTIC
WITH
LESS
NATURAL
GAS
GAS APPLIANCES. [ABSTRACT.]
THIS paper gives the principal conclusions from the laboratory and field investigations of the Bureau on the correct use of It is estimated that it would take a natural gas in the home. million dollars worth of artificial gas each day to replace the waste in natural gas appliances, and it is certain that unless this waste is halted, it will be but a short time when most of the more than two thousand small communities depending on natural gas will have to go back to solid fuel with its many inconveniences, since most of them are not large enough to maintain manufactured plants. .\bout one-half of the cities in the United States have natural gas, and the consumers number over two and one-half million. Most of the natural gas stoves have the burners placed two and one-half inches or more below the top of the grid or the solid top which many of them have. This has made it necessary to burn a large volume of gas, supplied with a high pressure and has resulted in a great waste of gas, and very poor service during the winter when the pressure happened to be low. Tests have shown that by removing the solid top and raising the, burners close to the vessel, it is possible to reduce the gas consumption to one-fourth that required with the low set, solid top stoves, and also to improve the service very much. ‘Circular No. 116.
U. THE
S. BUREAU OF STI\R.DARDS NOTES.
CEMENTING
QUALITIES
OF THE
[J. F. I.
CALCIUM
ALUMINATES.” By P. H. Bates.
THE four calcium aluminates, 3CaO.A1,0,, 5CaO.3Al,O,, CaO.AI,O,, and 3Ca0.5Al,O,,, which are the only anhydrous compounds of lime and alumina, were prepared in a pure condition by heating together the proper proportion of these compounds. After microscopic examination had shown that homogenous compounds had been formed, the products were finely ground and their cementing qualities when gaged with water were determined. The two compounds higher in lime reacted very energetically with the evolution of much heat, acquiring practically instanhigher in alumina reacted with tanelous set. The two compounds water more like Portland cement, but showed higher strength at earlier periods than the latter. It was thought desirable therefore to prepare these in larger quantities and containing such impurities as silica, iron oxide, and magnesia, which would generally be present in lime and alumina of natural origin. The two compounds CaO.Al,O, and 3Ca0.5Al,O, were consequently burned in a 2 by 20 foot rotary kiln, varying their composition so that the silica, iron oxide, and magnesia reached limits of 17.38, 3.10, and 3.66 per cent., respectively, as maxima in a series of eight cements. The process, of manufacture was entirely similar to that used in the production of Portland cement. The ground cements were used in making the usual small tension and compressive test pieces and 6 by 12 in. gravel concr&e The striking cylinders of I : 1.5 : 4.5 and I : 3 : 9 proportions. feature of the data obtained from testing these at different periods up to and including three years was the very high z4-hour strength. The rich concretes prepared from four of the cements developed in 24 hours strengths in excess of 2800 pounds per square inch, and the lead concretes from two of the cements gavel strengths beyond 1500 lb. at the same period. Consistent gain in strength was obtained up to one year, when one’ of the cements in the rich concrete gave a strength of 8220 pounds per square inch. ’Technologic Paper No. 197.
ITo\,., 1g21.1
U. S. Eu~r~\lu OF STANDARDS NOTES.
669
Test pieces stored in water tended to show retrogression in strength with age. This was also noted with test pieces stored in the damp clos&, but to a much less degree. This action may be explained by the fact that the products of the hydration of all the aluminates are a hydrated 3CaO.A1,0, and hydrated alumina (except in the case of the1 anhydrous 3CaO.A1,0:,, when no hydrated alumina is produced). This latter is the cementing agent in these products, and, being colloidal, it is very susceptible to moisture changes. Large amounts of moisture are taken up in the presence of the latter with consequent swelling of the colloid and reduction in strength.
HOW
TO
GET
BETTER
SERVICE
IN DOMESTIC
WITH
LESS
NATURAL
GAS
GAS APPLIANCES. [ABSTRACT.]
THIS paper gives the principal conclusions from the laboratory and field investigations of the Bureau on the correct use of It is estimated that it would take a natural gas in the home. million dollars worth of artificial gas each day to replace the waste in natural gas appliances, and it is certain that unless this waste is halted, it will be but a short time when most of the more than two thousand small communities depending on natural gas will have to go back to solid fuel with its many inconveniences, since most of them are not large enough to maintain manufactured plants. .\bout one-half of the cities in the United States have natural gas, and the consumers number over two and one-half million. Most of the natural gas stoves have the burners placed two and one-half inches or more below the top of the grid or the solid top which many of them have. This has made it necessary to burn a large volume of gas, supplied with a high pressure and has resulted in a great waste of gas, and very poor service during the winter when the pressure happened to be low. Tests have shown that by removing the solid top and raising the, burners close to the vessel, it is possible to reduce the gas consumption to one-fourth that required with the low set, solid top stoves, and also to improve the service very much. ‘Circular No. 116.