help

labormates

pouring my first concrete slab i need to know a few things. it is 12 by 9 it butts up against the exsisting patio and also against a side walk on 2 sides of it. does something go between the exsisting concrete and the new pour slab and what type of reinforcement should i use

axel

Pouring your "first" concrete slab opens the door to a lot of information. I expect you have done some research on the product and the requirements for proper placement. The product is sensitive to environmental conditions, proper proportions and handling. The tools and workmanship of the trade are specialized.

To address your specific questions:

You do not need any special preparation to the surface the slab abuts. And I would suggest a fiber additive to the mix, or use wire mesh to reinforce it.

2pyrs

If you are trying to pour a block 12 foot by nine foot get a pro to do it. If you are doing a walking path consider plastic form to pour your cement in to make cobblestone or squares from or patio blocks.
When I poured my 5’x5’ block for front door entrance all I did was take some 2”x 6”s on three sides and made it to the shape/size I wanted and took a level to it. Digging the dirt out to make it the height I wanted. And then poured stone in and placed some chicken wire in about and 2 inches down from the edge of the box form. I placed a piece of felt paper against the house where new cement would touch. As for the other sides they sell a felt strip you can place against the old walk. I am not sure but I thought the reason for the strips was for movement and freezing so as not to crack the other cement. As for tools all I used and still have was a trowel $6.00 and edge trimmer $5.00, shovel, hoe to mix cement in wheel barrel. Job done and still there 10 years old and no cracks. If I new how to post a photo I could show of my handy work. Now then how do I move it since I moved front door to other side of the house?

2pyrs

mighty anvil

A compressible joint filler should be placed between a concrete slab edge and any vertical surface to avoid bonding and to allow for expansion. If the concrete is to exposed to the weather it should be "air-entrained" for greater durability. A sheet of 6x6 - 10/10 (6" square openings, 10 gague wire) welded wire mesh will help prevent cracking if it is placed at the mid point of the slab depth. Hold it up with concrete supports made for that purpose, don't lift it after the pour. Don't add water to the initial mix. The biggest mistake made by DIY'ers is to trowel the bleed water back into the slab which causes a weak surface which will usually result in a condition called scaling. After the initial sceeding either remove the bleed water or let it evaporate before finishing the concrete. It should be covered and/or kept wet while curing.

labormates

thanks for all the help i pour it last summer no cracks yet