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International Concrete Abstracts Portal

Showing 1-5 of 11 Abstracts search results

Document: 

SP32-05

Date: 

July 1, 1972

Author(s):

W. V. Friedlaender and F. V. Camarda

Publication:

Symposium Papers

Volume:

32

Abstract:

The influences of superheated steam on the strengths of autoclave cured cement mortar specimens and asbestos-cement compositions were examined. The test results show that superheated steam, apparently because it acts as a desiccant, generally causes reduced strengths that can be related to functions of the cured weight after autoclaving as well as a factor involvinggthe length and degrees of superheat. If super-heated steam is present during the early stages of the curing cycle it causes greater adverse strength effects.

DOI:

10.14359/6601


Document: 

SP32-03

Date: 

July 1, 1972

Author(s):

Sergey A. Mironov, Liarisa A. Malinina and Svetlana Cheryachukina

Publication:

Symposium Papers

Volume:

32

Abstract:

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.

DOI:

10.14359/6599


Document: 

SP32-04

Date: 

July 1, 1972

Author(s):

Thomas B. Redmond, Jr.

Publication:

Symposium Papers

Volume:

32

Abstract:

The report data are from three investigations on autoclave curing of block-type concrete mixes. Variables were presteaming time, heating time, heating rate, and time at maximum temperature and pressure of laboratory and plant-manufactured specimens of three aggregate types. The principal finding was the high strength and low drying shrinkage generally obtained with two hours of curing at 365 F. A one-hour cure at 400 F produced optimum strength in the test series investigating higher temperatures. With the industry trend to faster rail charging systems, data indi-cate the feasibility of four curing cycles per autoclave per day. However, author recommends that time at maximum temperature should not be shorter than five hours unless long-term individual plant tests have consistently demonstrated good results.

DOI:

10.14359/6600


Document: 

SP32-02

Date: 

July 1, 1972

Author(s):

James C. Bailey and Ernest C. Clay

Publication:

Symposium Papers

Volume:

32

Abstract:

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.

DOI:

10.14359/6598


Document: 

SP32-07

Date: 

July 1, 1972

Author(s):

A. V. Satalkin, P. G. Komokhov, and I. P. Kromin

Publication:

Symposium Papers

Volume:

32

Abstract:

Autoclaved concretes using lime-silica binders can be made with strengths of 500-600 kgf/cm2 (7000-8500 psi) or more. Higher strengths are obtained with crushed stone than with sand and gravel aggregate, but concretes without coarse aggregate are more commonly made in the USSR. Although state standard specifications for autoclaved aproducts require that the limes used contain not more than 1 percent MgO, such pure limes are not available throughout the USSR. Concretes have been made in the laboratory using limes with MgO contents as high as 25 percent. Strengths of such concretes are lower, but with additives such as MgC12, CaC12, and NH4Cl these low strength levels can be improved considerably. Concretes made with magnesian limes have withstood more than 200 cycles of freezing and thawing. Reinforcing steel sometimes requires a protective coating to prevent cor-rosion.

DOI:

10.14359/6603


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