Shorter Autoclave Cycles For Concrete Masonry Units


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Title: Shorter Autoclave Cycles For Concrete Masonry Units

Author(s): Thomas B. Redmond, Jr.

Publication: Special Publication

Volume: 32


Appears on pages(s): 57-98

Keywords: autoclaving; compressive strength; concrete block; concretes; curing; drying shrinkage; expanded shale aggregates; expanded slag aggre-gates; heating; high temperature;

Date: 7/1/1972

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.