Field and laboratory tests conducted by the Corps of Engineers indicate that the failure of a concrete surface to harden when cast against a wood form is directly dependent upon: (1) the concentration of reactive constituents in the wood; (2) the availability of mixing and curing water; (3) the ambient temperatures and the concrete temperatures. The difficulties can be corrected by reducing or counteracting the concentration of reactive agents in wood or by rejecting lumber containing high concentrations of reactive substances. Generally speaking, however, it is not economical to run chemical tests on each piece of lumber to determine high and therefore reactive concentrations. The Corp's report suggests that wood be treated and rendered usable for forms only when problem lumber is encountered or suspected.