cracks in newly poured concrete slab?

Question

cracks in newly poured concrete slab?

Answer 1

Concrete does 2 things: It gets hard and it cracks. Concrete will ALWAYS ALWAYS crack.



Here is an example:

Look at a sidewalk and you see it's normally grooved into 4x4 or 5x5 squares. A typical sidewalk is 4 inches thick, so either while finishing or after (depending on the style) the contractor will place cuts in it about 1 inch deep. These are placed to weaken the concrete in a straight line to encourage it to crack in a straight line.



Your floor should be similar. The average floor should be cut into 10'x10' squares to weaken the concrete to encourage it to crack in straight lines. There is NO guarantee that concrete will not crack in other areas, all one can do is encourage it to crack where it is cut.



Now, if your floor doesn't have any cuts in it, then that's the contractor's fault. Ideally a finish floor is cut the same night it's poured with a soft-cut saw, or first thing the next day with a saw cart. The floor WILL crack within it's first 24 or so hours so it's imperative that he cuts it as soon as possible.



Also, an 8" thick floor is ridiculously thick for a basement floor. Typical residential floors are only half that thick.

Answer 2

It is very typical to get surface cracking in concrete especially if it was poured in hot weather and no curing agent applied. These surface cracks are typically very shallow and do not extend down the full depth of the concrete.Over time, a crack may emerge from the bottom of the slab that merges with a surface crack, but the surface crack will not cause a failure. The top of the slab will be loaded with a compressive force and concrete stands up very well to compressive forces, but it is very weak in tensile strength.

Answer 3

I would get a different (professional) opinion from someone. Could be poor ground or tree roots or a number of many things causing this. You don't want to spend all that money then have a house on top of it and have I gut the basement out to re-do concrete. There are construction forums on the Internet with professionals that can help you if you just post pictures and a question.

Answer 4

working as a mason i found there are 2 types of concrete

1: concreat that has cracked

2: concrete that hasn't cracked yet



all concrete cracks due to the expansion and the weather so don't worry