Low compressive strength for grout
Low compressive strength for grout
(OP)
I have a low 56-day grout break. What investigative services can be done other than windsor probe (which is not exactly deependable)?
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
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Low compressive strength for grout
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RE: Low compressive strength for grout
Too often, a high grout strength can end up being specified since someone erroneously thinks stronger is better.
There are applications where the grout strength should be lower than the compressive strength of the masonry units.
What sampling and testing procedure was used? - ASTM C1019?
Dick
RE: Low compressive strength for grout
RE: Low compressive strength for grout
do you have submitted breaks for the CMU's by the supplier?
Are you the testing firm, contractor, grout supplier, egr?
What state are you located in?
RE: Low compressive strength for grout
You may be faced with trying to acheive 3000 psi grout in a 1900 psi (net) block strength where the gorout is only intended to bond the rebar to the masonry, since the compression strength of the block is probably the critical item.
Mortar strengths are a minor factor in the compressive strength of most masonry. If you use higher strength grout to acheive a required prism strength, someone is making a very big error.
Cardboard forms can give misleading results with some different types of masonry units (unit density and absorption can vary widely).
If you are just testing the materials, give the results to the engineer, so he can decide if the materials are adequate for the design in the big picture.
RE: Low compressive strength for grout
The first method dealt with in 2105.2, is the unit strength method and the second method is the prism test method.
In addition to testing masonry units, compliance with f'g is required when the unit strength method is used. The f’g must be equal to f’m but must not be less than 2,000 psi. It seems that the unit strength method is the approach you followed. No?
If compliance with f'm is by the unit strength method, what are the f'm, type of mortar used, and the required net area compressive strength of the CMUs? Do you have test results for compressive strength of the masonry units?
Well, what are the options if compliance with f’m is not achieved with either the UNIT STRENGTH METHOD or the PRISM TEST METHOD? The code (IBC 2105.3) does permit for determining compliance with f'm by testing prisms cut from masonry. If you want to utilize an NDT method as an alternate, it will be prudent to first discuss this approach with the EOR and AHJ/BO in order to seek approval of the NDT method proposed.
RE: Low compressive strength for grout
RE: Low compressive strength for grout
of course the SER is god in the issue since it's his/her spec.
Watch out for NDT on the walls. just b/c there is an ASTM test for saw-cutting and compression testing the sample doesn't mean it is easy or that your break machine can handle the load. Windsor probing is not meant for what you're doing.
As far as the rebar and the grout spacing goes, this has been a problem with this test every time it's been done NDT, would you agree. I had to take samples to the university to break them. The samples were truly pains in but to cap too (had to build molds and it was still awkward ~1 hr per sample. There is an old Uniform Building Code method that involves horizontal coring the wall and testing the core that appears easy to perform.
I've been using NDT loosely here, obviously coring or saw-cutting samples are DT. I am unaware (and very skeptical of it if one exists) of any true NDT test for masonry construction in this application, but i don't see a problem with what you've presented anyway.
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RE: Low compressive strength for grout