New patio concrete cracks

JR's Avatar (by Gravatar) by JR in  Masonry » Concrete 

I hired a licensed concrete contractor to place a 4 1/2" thick reinforced patio slab and a 55' long 6' high reinforced concrete masonry wall along my property line. The first indication that I hired a dishonest contractor was when I looked down the cells of the masonry wall and saw they placed a mesh barrier above the horizontal rebar to stop the grout from flowing to the base of the wall. (I should have fired him on the spot ,instead I made sure he removed the barrier). The contractor decided to grout the wall and place the concrete in one day that way he only had to rent a pump once. On the day of the pour the grout arrived first I watched to make sure they vibrated the wall to the bottom of each cell . While I was watching the laborer vibrate the wall they drug the pump hose to the back patio slab and proceeded to place in the forms approximately 2 yards of grout mix approximately 2 1/2" thick on the bottom of the new slab when I finally got to the back yard and saw what they were doing yelled stop. I told the contractor this is not an acceptable practice , heres the worse part there was a 2 plus hour wait time before the same concrete truck round tripped back with the new concrete mix. So now there is 2 1/2" thick of hardened grout creating a horizontal cold joint throughout the slab in a slab that is only 4 1/2" thick plus the obvious Two completely different mix designs on top of each other 4 1/2" thick . Well,,, within a span of 12 hours the slab sirface had numerous Cracks. Here is my questions... Did the slab crack because of the different shrinkage rates of the different mix designs? Does grout shrink more or less than concrete ? The attached pictires show the pump hose placing fresh concrete over already set grout a,other pictures show cracks already appearing in fresh green concrete slab surface.. ...as of today the time of this post I have filed a complaint with the contractors license board and with his bonding insurance company. The contractor wants to place a concrete topping over the slab to hide the cracks ,But I contacted the topping mix engineering department they told me if the slab is cracking and moving the topping will crack. The only fix I know of is completely remove the slab and replace it. I do have one more question... Does any one know of a product or fix other than removal and replace?

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