Windsor Probe for Grout Correlation

[dmoler]

Windsor probe is for concrete, but is there a way to check grout strength with it? Is there a published reference somewhere that someone can give me to correlate the probe with grout? Is there a published reference where results of research says that correlations are not possible?

 

[jheidt2543]

Why not correlate the probe yourself on some test batches of grout the same as you would with concrete?

 

[dmoler]

ummm....yes, that is the intent of the original question restated, which is basically is this a waste of time or reliable way based on published studies. Where would a published reference be that states this is acceptable (ie. ACI manual does not provide this that I could find, nor any other reference.) This cannot be some groundbreaking idea, there must be back-up, which I simply cannot find.

 

[jheidt2543]

Well, I guess I'll take another stab:

First, I would call the Windsor probe manufacturer and get their take on it. They would certainly have the best information.

Secondly, although I've never done it myself and the best way to calibrate the probe is to have it done at the factory, you could run trial batches just as you would for concrete and compare the beam compression tests with the Windsor probe tests. That is certainly an acceptable engineering method, although time consuming.

When you think about it, the probe doesn't "know" if it is testing concrete or grout. They are basically the same material with different size course aggregate.

 

[samdamon]

Dmoler, Don't think the windsor probe can be used for reviewing as-built grout strength. No correlation between the probe results and grout strength has been published to my knowledge, and anyway, why do you want to check the grout strength? ASTM standards for grout generally establish a mix design at the start of the job, based on either LAB tests or proportions of the ingredients. My understanding is that neither approach is meant to be used as a benchmark or standard for comparing to field tests of as-built grout. Grout is not tested and controlled during the job like concrete, at least inb my experience. Instead the testing lab should simply be making sure that whatever grout mix design was settled on at the start of the job, by whichever means, is actually being followed on the job site.

If the quality of grouted masonry is questionable there are other means availbale to test besides the Windsor probe, include cutting out prisms and breaking them, or using a flatjack. However, both those methods are obviously destructive, can be expensive and can also be innaccurate for a variety of reasons.

What issues are you concerned about?

Regards

 

[henri2]

dmoler,

What type of grout....grout for masonry, post-tensioned stressing pockets, non-shrink grout beneath base plates?

 

[dmoler]

There was several columns, 5000 psi concrete, and for some reason large patches were needed. Apparently something happend where patches from perhaps 6 inches to 18 inches in diameter and from only about 3 inches to as much as 6 inches deep were needed in the columns. Columns were max 3 feet wide. This was after most elements of the building were in place including the roof, masonry walls, and even some interior finishing was beginning.

The GC decided to take it upon himself, without consulting the Structural Engineer, to tell some masonry grout people to patch the columns. Then he called my field guys out to test it with the WP. When I got the test report, and found out what was happening, I told him to generate an RFI to have the Structural submit the patching requirements with a testing/quality control requirement. Of course he didnt want to, tried to get me to submit something that said the patches and columns were ok, and I told him to forget it.

I told him that the ASTM specifically says that the test if for hardened concrete only, not grout. But I also told him that we just tested this per his request, and the Structural Engineer makes decisions about what is acceptable, it is not my decision, and to submit it for his review.

I dont usually get involved in structural remedies for this type of thing, and in the past I cored columns after high strength epoxy was injected into columns and the outside patched with this, and the Structural Engineer visually inspected the cores and I believe they might have been compressively tested for strength, with epoxy 'planes' in the core.

I was just curious about this particular problem. I only do geotech but get involved in materials testing from time to time.

 

[samdamon]

dmoler- Suggest you verify the materials used in the patches before doing anything else. Grout doesn't sound like the right fix for your situation. A proprietary vertical/overhead repair mortar (Available from a variety of manufacturers) might be more appropriate. The thickness of patch you describe may require several lifts of repair material. (Different repair materials will have different requirments in this regard). Do the columns have just plain reinforcing?

Regards

 

[ArneG]

Let the Engineer of Record provide direction for the remedy and then assist him in specifying testing options after he's specified the remedy.

If he used masonry grout, the grout is probably just an aesthetic patch due to the shrinkage in relation to the already set concrete and the lack of bond strength between the materials.

Its quite possible that with 3' columns the EOR doesn't need the patches to do anything structurally at all - but thats what he gets paid to say.

 

[henri2]

I concur with the views of those who say that masonry grout should not be used for this repair because there are other factors to contend with apart from compressive strength of the masonry grout.

There are products developed by companies like Sika, Grace, and Master Builders for this type of concrete repair. Preferably, a product which has been evaluated and listed by an organization like ICC-ES should be utilized.