grout instead of concrete

huangyhg

grout instead of concrete
has anyone ever replaced concrete with grout for an elevated slab?  contractor on my project did.  said his grout hog couldn't pump concrete..aggregate too big.  the application is a stair landing in a stair tower.  the design called for 5" thick concrete slab spanning 7.5'.  2" metal deck form was used.  he used 5000 psi grout when 3500 psi concrete was specified.  i don't think it will be a problem, but am not 100% sure.  seems more expensive.  what if it was masonry grout?
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get the mix design or truck ticket copy, and repost.  typical masonry grout will have too high a water content since almost all of the water over a 3" slump gets absorbed into the cmu block unless it was made fluid by plasticizers and not heavy water.  i've seen a 2" pump concrete mix installed many times for stair landings/risers.  
i think grout shrinks more that the regular concrete, unless shrinkage is mitigated by speciality admixture or cement.  also, since there is no coarse aggregate, concrete will not contribute anything to the shear capacity (shear capcity may not be any problem for your case).
will the 2" steel deck carry the load on its own?  if so, no worries.
next time have the gc submit a pumpable design mix developed by his ready mix supplier.
maybe he should hire the engineer to stamp his mistake
i believe grout is more porous than concrete so it wont provide the same level of corrosion protection.
csd
did you have cylinders taken?
the sampling and testing procedures for concrete are different than for for grout.
5000 psi grout in a concrete cylinder form may not test 3500 psi because of the sample preparation and curing conditions. shrinkage will be much greater because of the greater cement content and the excess water that cannot be absorbed by surrounding materials.
apparently, the contractor did not have the appropriate equipment or did not chose to make it work for the specified application.
dick
grout will generally have more cement than a concrete mix. you should have a copy of the mix and cubes or some indication of design strength. be careful to  cure well to prvent cracking. cracking is generally not a structural problem.