INITIAL RATE OF ABSORPTlON / IRA
The weight of water absorbed expressed in grams per 30 sq. in. of contact surface when a brick is partially immersed for one minute. Also called suction. See ASTM Specification C67
Originally the IRA was limited by the BIA standard (Building Code Requirements for Engineered Brick Masonry, Brick Institute of America, McLean, Virginia, August 1969.). It limited the IRA of brick at the time of laying to a maximum .025 oz per sq in. per min (approximately 20 g /30 sq in./min). Since then, the ASTM C 62 and ASTM C 216 have been changed and now recommend that the limit on IRA be 30 g /30 sq in./min. This IRA determination may be made either in the laboratory on oven-dry brick, or at the construction site as a field test.

in·ter·ac·tion/in-t&-'rak-sh&n/
Function: noun
Date: 19th century
Mutual (or reciprocal) action or influence.

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