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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 11 Abstracts search results
Document:
SP32-06
Date:
July 1, 1972
Author(s):
Julie C. Yang
Publication:
Symposium Papers
Volume:
32
Abstract:
Curing of asbestos-cement products by high-pressure autoclave, including saturated steam and superheated steam conditions is dis-cussed and compared. The binder produced under the various conditions were characterized by x-ray diffraction, DTA, microscopic point-count estimation of composition, pore spectra, uncombined Ca(OH)2 analysis, density, and strength determinations. The desired high-strength binder was essenti-ally tobermorite and some CSHn gel. Al-substituted tobermorite and CSHII) may be present in small amounts, but C2SH, Al2O3, Fe2O3, and S03-bearing hydrous phases were not detected. Superheated steam conditions should be avoided at all time, and saturated steam autoclaving can be carried out usually at pressures around 100-l 10 psig (7.0 - 7.7 kgf/cm2) for times of about 16 hr Curing in saturated steam, utilizing a water spray technique, is recommended because it permits the desired binders to be formed over a broad pressure range and also reduces significantly the autoclaving time. An optimum autoclaving cycle is recommended that uses stepwise curing at two pressure levels in the presence of water spray: 5.5 hr at 115 psig (8.1 kgf/cm2 followed by a 3.0 hr at about 130 psig (9.1 kgf/cm2).
DOI:
10.14359/6602
SP32-09
C. James Gulde
of the materials used in autoclaved block and beick manufacutre contribute to the color, but piin ents contribute the most. Mineral pigments and some others are satisfactory, but all are not effective, and some contain undesirable contaminants. For many colors it is possible to duplicate, in masonry units, any combination of hue, value, and chroma. Versatility in color production and reproduction requires a simple color laboratory and the es-tablishment of a library of color specimens made with the masonry ingredients used by the plant. One patented procedure is based on the introduction of a fluidized color mix onto one face of the machine mold box immediately before each filling of the mold box.
10.14359/6605
SP32-02
James C. Bailey and Ernest C. Clay
Automation in the block industry is at a primitive stage compared to some other industries. Within the block manufacturing process, the greatest advancement of automation has developed in proportioning and mixing. Those plants constructed in recent years that have been the most automated have all utilized single-stage autoclaving in some form. The efficiency of autoclave production depends on using a maximum portion of each 24 hr for curing, and a minimum I for loading and unloading the autoclave. Thus, efficient and b rapid movement of block from one end of the flow diagram to the other is important. It may be accomplished either by using transfer cars in a shuttle system or by using trains that operate over curved tracks and switches. Disadvantages of these systems suggest the desirability of a completely circular system if technical difficulties could be surmounted.
10.14359/6598
SP32-03
Sergey A. Mironov, Liarisa A. Malinina and Svetlana Cheryachukina
The disruptive expansion of concrete which is experienced with either early or rapid application of heat in the autoclave is caused almost entirely by the expansion of the air and water vapor enclosed within the concrete. Deformations in concretre speciments caused by this gaseous expansion during autoclaivng have ben measured. It has been found that if external steamair environment presure is applied properly, these deformations can be prevented. Te method used is to seal the autoclave immediately after introduction specimens, and not vent the air during steaming. The result is that the pressure buildup inside the specimen is actually offset by the couter-pressure of the environment. Higher strenghs were obtained on 10-cm cubes cured in this manner thatn those cured in the usal way. An additional benefit of the method is aht mositure is "locked into" the specimen. Apparently the lack of air migration toward the exteriro helps retain moisture, as indicated by the lower moisture loss meaused when curing with steam-and-using a pressure of 1 atmosphere of air show that pressure reduces moisture loss and increases strength.
10.14359/6599
SP32-08
Y. M. Butt, V. V. Timashev, and V. S. Bakshutov
The phase compositions and crystal forms of calcium silicate hydrates and calcium aluminate hydrates formed during autoclaving are dependent on temperature, pressure, stoichiometric relationships, and the concentration of Ca2+, Na+, K+, and li+ ions in solution. Most crystals and crystal aggregations are of a characteristic type. Some crystal intergrowth occurs, mainly interpenetration and agglomeration. Illustrations are shown.
10.14359/6604
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