Replies

1. 
   popawheelie | Dec 19, 2009 06:10pm | #1

   I just use rebar dowels about 12" apart.

   If you use the right concrete bit the rebar will go in with a big hammer. It's a friction fit.

   I use 1/2" rebar.

1. 
   cwcjr09 | Dec 19, 2009 06:26pm | #2

   ok.thanks

   only dowles or do they get tied into mesh or rebar in the new slab?

   should i use a bonding agent on the old slab face to help join the two?

1. 
   popawheelie | Dec 20, 2009 03:13pm | #6

   I second what Calvid said. I used bonding agent the last time i did it. It helps to have someone applying it ahead of the person placing the concrete. It dries out pretty quickly. I also wet the sides before I place the concrete with a slurry taken from you concrete. Use gloves and get the joint wet.

   I spray the sides for a few hours before the pour. The concrete is dry and keeps sucking up the water.

   I might have tied the two sides together. Can't remember. Couldn't hurt.

   I went down the sides of the trench with a magic marker and layed out the dowels so they were opposing eachother.

   It's a pain to level it off. Concrete gets under tour trowel or board. You have to keep wiping/scraping off the concrete that gets on your old slab because it throw off the level. I think I use a big masons/tile sponge.

   As you lay it keep pulling the mud off the slab and into the hole so your level is right. It would really help to have a helper placing the concrete in front of you so you can stay down on knee pads getting it right and scooching down the line.

   As you can tell, I like to get it right.

2. 
   calvin | Dec 19, 2009 06:51pm | #3

   Concentrate some effort on the base. Using the old cinders would be ok, the clay I would eliminate. You've expanded that clay with digging (all of it would never fit in the hole). Fill and tamp with stone-in lifts in your trenches. Crossing the stubbed out bars with rod tied to it would sure help keeping them aligned. Concrete glue on the clean slab edge is cheap insurance. (I've had patches on top of sidewalks last, the glue was part of the process).

   Since you're tiling you don't want a straight line settling crack to ruin the job. It's all in the details. An isolation membrane placed over the joints would be recommended too.

   Best of luck.

3. 
   DanH | Dec 19, 2009 11:36pm | #4

   Yeah, you definitely want an isolation membrane over that puppy.

1. 
   cwcjr09 | Dec 20, 2009 11:11am | #5

   How long would you wait after the pour to start framing and finishing?