DELETERIOUS EFFECTS OF FORM LUMBER ON CONCRETE SURFACES.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS
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Deleterious effects apparently produced by form lumber in contact with freshly placed concrete have been experienced in the field on several occasions. Literature concerning the chemistry of wood indicates that a number of wood constituents may be deleterious to concrete. Laboratory tests have indicated that the failure of a concrete surface to harden when in contact with a wood form is directly dependent upon 1 The concentration of the woods reactive constituents, such as polysaccharides, tannins, and aliphatic and fatty acids. 2 The availability of mixing and curing water. 3 The temperatures of the concrete and of the wood forms. It is recommended that suspect lumber, such as lumber produced from trees cut in the spring, be tested by casting mortar against samples of the lumber to determine whether a deleterious reaction will result. Lumber suspected of containing a concentration of deleterious reactive constituents should be treated with one or more applications of limewater, to reduce the concentration of the reactive constituents, prior to its use as form lumber. This precaution is particularly important if the concrete is to be water-cured. Form oils should be throughly applied to all wood forms, particularly in the joints of each form. Author
- Ceramics, Refractories and Glass