Concrete Slab with Fiber Mesh or Wire Mesh Reinforcement
Q. I enjoy your show. I am planing on having a patio put in. I want to do all that I can to help it not crack. The installer said he would use Fiber mesh cement. Would it be a good idea to also use that reinforceing wire along with this Fiber mesh cement and should he also put what they call those soft cuttings in it too? The patio would be approximately 11 by 12 in size. Will appreciate your answer.
A. I advise welded wire fabric (6x6x10x10 mesh - 6"x6" pattern with #10 gauge wire both directions), low slump concrete which means poured pretty dry (not a lot of water mixed in), 3,000 psi concrete, air entrained (little air bubbles in the cured concrete allowing water freeze expansion to fill the air bubbles instead of expanding inside the concrete causing stress, and soft cuttings (meaning weakening the concrete with tools in a straight line inviting the concrete to crack in a predetermined, usually straight, line when it cracks. Better yet is to use both the steel rebar with the fiber mesh. The rebar is placed where loads are heavy like at the drive curb near the street where heavy trucks might turn into your drive. also put the rebar in the other heavy load areas like down the driveway for extra support. The fiber mesh strengthens the concrete and the steel rebar reinforces the extra load areas.
All concrete cracks. All concrete shrinks. Soft cuts allow the installer to plan the event rather than have some random, angled crack which looks like a mistake. You can add the fiber mesh too for added insurance and it will strengthen the slab. I would rather you use the wire mesh, low slump concrete, and soft cuts. Your 12x12 is pretty small for more than this. Fiber mesh can adversely affect the finish depending on whether you want a swirl finish, boom finish or exposed aggregate stone finish. The fiber mesh is good stuff but can stick up above the concrete surface and look fuzzy. This causes the finisher to try to finish a fuzzy blanket and makes the finish more difficult to achieve.
I suggest you invest in a 4" crushed stone, compacted base under the slab. This is the true strength of any pavement. If the sub-grade or rock under the slab is done correctly ... then the concrete behaves solidly. Many homeowners worry about the concrete, which is the skin, and miss the opportunity to make the crushed stone base (structure) the solid structure beneath the slab (skin). It sounds like you have some pretty good advise coming from your concrete installer. Ask about these things and I believe you will come to a good result. Remember ... all concrete cracks .... soft cuts define where they crack.
For a 12x12 exterior slab ...I advise 4" of compacted stone sub-grade, wire mesh, no fiber, low slump concrete, air entrained, 3,000 psi mix, and soft cuts creating a four-square pattern. The slab will definitely crack on the four-square lines but you will have done all you could. The rest is up to mother nature.
Good luck. I wish you many wonderful times enjoying your new concrete space.