Slab-on-ground joint filler 1

[sbw]

I am hoping someone may be able to clarify why ACI 360R-06, section 5.4 suggests that semi rigid epoxy provides sufficient shoulder support for joints subjected to wheeled traffic and discourages the use of elastomeric joint filler? Any knowledge gained from practical experience would also be greatly appreciated.

To expand on this question, I understand that even with delayed installation of the joint filler, say 90 days after concrete placement, the floor slab will continue to shrink. With semi-rigid epoxy filler this can and often does leed to filler separation. I have seen written that the consensus of the industry is that separation void of the filler of 1/32" or less is considered acceptable. Wouldn't the slab shrinkage after joint filler installation (and prior to joint filler separation) actually induce tension in the shoulder effectively making it more susceptible to spalling? Furthermore, once the joint filler has separated and even being within the 1/32" tolerance, it's not clear to me why this would be considered a supported joint shoulder.

The general concept of using a filler that has a more compatible stiffness to the concrete makes sense; however, actual practice and performance does not seem to support this rationalization. Based on this, the elastomeric joint filler would seem to be a better choice because, if nothing else, it reduced maintenance (no joint separation to deal with). Your feedback will be much appreciated.

 

[hokie66]

I think this is the one JAE was trying to post. See if it works now.

http://www.metzgermcguire.com/PDFs 2008/MM-80 Tech Data T-1 2009.pdf

 

[JAE]

That's the one....thank you hokie66.

 

[hokie66]

Some interesting reading on the subject, representing probably the same two points of view expressed in our discussion.

http://www.concreteconstruction.net/industry-news.asp?sectionID=986&articleID=483111

 

[JAE]

hokie66,

Did you read both articles and side with one guy or the other?

I thought the response by Weiss was insufficient to counter the issue of hard wheel loads on joint edges that Tarr put forward.

I can't see how a polyurea material with that much flexibility would do anything to help the joint spalling under hard wheels.

 

[hokie66]

JAE,

I have mixed feelings about the two viewpoints. Weiss has made his points well, but has a proprietary interest. On the other hand, Tarr just seems to me to be parroting the ACI position, and I believe that ACI now gets into a lot of things they know little about. I would not specify a system which has a track record of separating. As Tarr says, there is no ideal material which serves as both a joint support and as a filler.

I think there is still an argument for armouring joints, not with angles as was the historical practice in industrial floors, but with flat bars or proprietary preformed epoxy bars. The attached is a system widely used in Australia for floors where the owner is serious about joints.

http://www.lesasystems.com.au/products/joint_protection/lesastrip.aspx

 

[sbw]

I recieved a response from ACI this morning and I must say I am rather dissapointed. I feel the response is fairly "canned", without specific thought given to the subject. The question I posed it pretty much verbatim what I posted on this forum. Here's the response:

-----

ACI publishes codes, specifications, and reports for the concrete user. This message is in response to your technical question/inquiry.

Below find the response (with minor modification) as received from the committee addressing your question:

Elastomeric sealants are inherently inappropriate for floors supporting hard wheeled vehicles because the relatively soft sealant (typically Shore A45-65) will deflect under load, thus leaving the joint edges vulnerable to impact. To support hard wheel traffic, especially small 4" diameter hard wheels such as those on pallet jacks, a filler must have a minimum Shore hardness of A80 or it too will deflect under load. A80 has been an industry standard for 35+ years and is thus proven successful.

The inquirer's comment about a semi-rigid filler inducing tension in the joint shoulder would be correct IF the filler had adhesive strength that see it tearing the shoulder off as the joint opens during slab shrinkage. But a properly formulated filler should have a lower adhesive and tensile strength, thus ensuring it will separate at its bond to the concrete OR within itself before it tears concrete. There are broad range of both epoxy and polyurea fillers in the industry all have low range strengths.

If one looks at a filler after typical joint opening he will usually find the filler bonded to the concrete only on one side. If the filler has been installed to the proper depth in a saw cut, a cross-section view would show that in effect the filler is a bar of solid rubber sitting on a concrete shelf for support. This bottom-basing
concept is the key to the success of semi-rigid fillers.

If the inquirer will go to any of the manufacturers' websites; i.e., (

http://www.metzgermcguire.com),

(

http://www.euclidchemical.com),

(

http://www.daytonsuperior.com)

or equal, will find relevant information their. For example, Metzger McGuire's website has a sketch shown on sheet T1 that makes the concept of semi-rigid fillers clear.

 

[BAretired]

sbw,

There is too much divergence of opinion on this issue to get a good answer from ACI or anyone else. Armoring the joints as hokie suggested may be the only sure way to guard against damage from hard wheels.

BA