Q.: Can I use aluminum channel successfully to make 10-foot straightedges for finishing concrete flatwork, or must I stick with magnesium? I know about the trouble with low strengths from entrained hydrogen gas when aluminum pipe was used to pump concrete, and I don't want to use aluminum if it's going to weaken the surface.

A.: We don't think there is any problem in using aluminum for this purpose. The aluminum is not in contact with the concrete for as long as aluminum would be if used in a pipeline, and any gas that does form should escape immediately from the concrete surface. So-called paver's straightedges made of aluminum are being sold, and we have not heard of any problems caused by using them.