Joint between hardened concrete surfaces 1

[AminSaalaar]

We are building a 30-foot underground concrete trench box for a utility service with dimensions of 3'x3'. We will have a monolithic pour for slab-on-Grade and walls. The top slabs will be precast and lowered on top of the walls at the end of project. A notch will be provided on top of walls so that when precast lids are lowerd on top of them, they can be locked in place. Do I need to provide any type of expansion joit board or membrane between walls and precast lids? Also, should I provide any expansion board between the three precast lids, and what material do I use to waterproof these joints?

Thank you in advance

 

[BigH]

Don't think that I would. After you lower in the top slabs and they are in place, you can grout the void to form a monolithic structure. Just make sure you have a means of preventing the loss of grout into the closed box. We never used expansion boards or whatever in many concrete box culverts we built in China that were construted in the same way.

 

[AminSaalaar]

I guess I was just a bit concerned about the contact surfaces between precast lids and top of walls. I'm worried that the concrete finishers don't provide a perfect contact surface and I will have to provide some type of cushion between the two to prevent concrete damages. However, I think using expanding grout should do the trick in terms of sealing. It's easy to do. The only drawback is that If I need to access the utility I would need to chip off all the grout to lift the lids.

 

[hokie66]

Neoprene pads?

 

[AminSaalaar]

Is there any specific type or grade of neoprene pad for this application. I guess the strps can be screwed to the top of walls to keep'me in place before lowering the precast lids.

 

[AminSaalaar]

Is there a website I can read about or see examples of?

 

[hokie66]

There are lots. Just Google. Here is one.

http://www.tamparubber.com/product_pages/gaskbrgp.htm