question about concrete??

[welddigger]

I,ve dug two pits now that were concrete lined down to about three or four foot and then I hit a concrete slab. Both I stopped at the slab thinking they were too new. After reading Baltbottles new digs I was wondering if this is what he is talking about when he talks of concrete. So, should I go back and bust out the crete and dig deeper or just keep looking for another pit. Both houses are from the middle 1800,s

 

[tigue710]

Id look for other pits, but it is possible they filled in a pit or used to a point and then poured the slab and concrete. Some areas had laws that would of made them do this. I would drill a hole through the slab and probe it first if anything....

 

[ajohn]

weldigger,
If you find concrete below grade at that level there could be only two possible reasons:
1) It is a continuous slab poured as part of a building or dwelling,as Patio slabs didn't become popular until 50's.Check for size(try to find an edge)Check for elevation,if they are at the same elevation,very high odds it is a continuous slab and was graded over with soil for a new dwelling or building.(Usually only in hilly areas)
2).It is what your looking for,and you have some hard work ahead of you.Concrete has a half life of 100yrs.+(Which means it will continually get harder for at least that much time)All which depends on the mixture being correct.70 to 100 year old concrete will break like glass,when it does break.If you punch a hole through it,depending on it's thickness.the bottom of the hole will be about 10 times the diameter of that on top.(It will break in a conical shape like glass.ie;shooting a BB through a window.when breaking up old concrete be careful,the edges will be SHARP like glass(Older concrete usually breaks at a sharper angle)
Hope this helps. Anthony-John