metallic grou

huangyhg

metallic grout
can somebody explain to me why one would use metallic grout? often times in specs i see "use non-shrink metallic grout". i think i can see why one would not use a metallic grout, due to possible staining issues, but what are the benefits of using a metallic grout.
thanks
in our office recently we had a presentation by a grout manufacturer, he said don't use metallic grout because its an old product, and the disadvantage is the expansion of the gruout during set up is not very well controlled at all.  this is a very undesireable quality:  you'd want that expansion to be very controlled in order to pass the necessary astm tests.
imo, this outweighs any advantage that might be had from using metallic grouts.  but like you, i don't really know what those advantages are.
regards,
chichuck
in my experience and training (more training and older engineers experience), metallic grout is in fact grout using aluminum as an admix... essentially the free rise of hydrogen gas, which then counteracts shrinkage, is the key issue.
al+ reacts with calciums and other components of concrete (particularly uncontrolled, as aggregates often introduce additional free chemical components of the reaction).  the use of metallic grout is much less of concern than the use of metallic expansive cements, which have been widely discredited, but it seems that the engineering comunity has forgotten the "why" of this dismissal... sadely i have seen two properties with the 35 year petrosky effect due to the use of metallic admix.
this has been discussed previously on eng-tips, and i believe it was mike m who does not even permit aluminum tools on site!  i completely agree, and similarly stipulate an aluminum free site.
hope that's a little more clarity,
cheers,
ys
b.eng (carleton)
working in new zealand, thinking of my snow covered home...
as youngstructural noted, most metallic grouts had finely divide aluminum powder added to cause slight expansion, overcoming the inherent shrinkage of portland cement.  further, some premixed grouts used a portion of metallic aggregate in the mix to further allay shrinkage.
neither of these is popular anymore, particularly with the advent of epoxy grouts and cement-filled epoxy grouts.
metallic grouts can cause lots of issues, particularly advancing the corrosion of embedded items.   
there are also metallic grouts used in reactor construction for radiation sheilding   
intrusion prepakt /marineconcrete.com