|
Posted by Matt Whiting on June 30, 2005, 5:40 pm
RicodJour wrote:
> Bob Morrison wrote:
>
>>In a previous post Matt Whiting says...
>>
>>>>CF&SG is correct in that rebar and lower water content will improve
>>>>structural performance. However, only the latter will have any effect
>>>>on crack control.
>>>
>>>Yes, but rebar will help prevent problems is there is a soft spot in the
>>>ground under the slab that settles a little. It can also prevent cracks
>>>from opening up or shifting vertically.
>>
>>Quite true. However, I tell the contractors to spend their time and
>>effort on subgrade preparation. It's easier to do than correctly
>>placing rebar, and with the current price of steel may even be cheaper.
>>
>>A good unreinforced slab on properly prepared subgrade with adequate
>>crack control should not have any problems.
>
>
> NY Code for concrete cover of reinforcing
>
> TABLE 1907.7.1
> MINIMUM CONCRETE COVER
>
>
> MINIMUM
>
> COVER
>
> CONCRETE EXPOSURE inches
>
>
>
> 1. Concrete cast against and permanently exposed to earth 3
>
> 2. Concrete exposed to earth or weather
>
> No. 6 through No. 18 bar 2
>
> No. 5 bar, W31 or D31 wire, and smaller 1-1/2
>
>
> If I'm reading that right, and you can figure out a way to cast the
> driveway above grade and then lower it into place (!), you can go with
> as little as a 3" slab. Otherwise you need 6" if it's cast in place
> and reinforced.
>
> Weird thing. If you _reinforce_ it, code requires a thicker slab!
>
> Bob's got it right, the slab doesn't move unless something underneath
> it does. Preparation - drainage, compaction, etc. - is the key.
Absolutely correct, but the problem is that you can't guarantee that
something won't move. Thus a little reinforcement is, IMO, cheap insurance.
Matt
| 
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap