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Re: [SEAOC] MASONRY GROUT

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Prisms were also taken on the job by the special inspector.  That's when the 
problem started.  The 1400 psi @ 28 days was based on the prisms.  Since 
then we have taken about 20 cores which produces about 1800 psi average at 
which time the grout is was about 60 days old.

Portland cement was used in the mix.  The mix design by the supplier shows 
about 6000 lbs. of cement and 5000 lbs of fly-ash.  I think they are 
sweating a little now.  I did not become aware of the mix design until the 
problems started.

The owner has sent two samples to Commercial Technology Labrotories for a 
chemical and petrographic analysis.  Hopefully we'll see what was really 
supplied.

What I haven't been able to locate, is the minimum grout strength based on 
coring.  I have a 1967 masonry code showing 1500 psi for cores and 2000 psi 
for prisms... but is outdated. 

Jeff Spence
Spencej(--nospam--at)mako.com

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>What about the special inspection? It would have been prudent to have prisms
>taken before construction began. Also, only Portland cement should be used
>for grout, not pozzolans.
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>At 07:05 AM 2/16/96 -0800, JEFF SPENCE wrote:
>>Looking for information to a construction problem located in Northern 
>>California regarding masonry walls... specifically grout.  I have designed 
>>18' tall masonry walls.  Supported @ the top, f'm=1500 psi, special 
>>inspections, 8" thick.  Temperatures have been cool but not cold.  Recent 
>>grout tests are showing a low compressive break.   500 psi @ 7 days and 1400 
>>psi @ 28 days.  1991 UBC code requires 2000 psi minimum.  After some 
>>investigation, I found the mix design calls for 5,000 lbs. of type F 
>>fly-ash.  Is this even possible???  The total numbers add up to 12 yds in a 
>>9 yd truck.  Core samples have also been taken resulting in a 1750 psi 
>>average strength.  Since this flyash has been noticed, different grout 
>>supplier has been selected.  Using the same design without the flyash... his 
>>7 day breaks have been around 1800 psi.
>>        The only place I can find reference to masonry grout cores is title 
>>24 of the UBC which is not in effect for this building.
>>        Question.... What short-term/long-term effects will fly-ash have on 
>>grout?  What other references are available regarding masonry grout cores?  
>>Currently the building official is leaning towards tearing down 3,000 sq. 
>>ft. of wall and maybe an additional 20,000 sq. ft. more.  Any suggestions or 
>>help would be appreciated.
>>
>>        Thanks !!
>>
>>        Jeff Spence, PE
>>        Spencej(--nospam--at)mako.com
>>
>>...
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