JTM wrote:

You are wrong about the wood. Wood 2x4's are commonly used
to fill expansion joints in new concrete driveways. The
main problem is shrinkage and warpage of the wood. You
don't see crushed wood and you don't see spalling caused by
the pressure

Just because someone uses a hammer to drive a scew doesn't make a good practice.
I see evidence of improper installations and poor workmanship all the time, but
it doesn't matter how many times something is botched up or the number of people
doing it--it is still shoddy practice. The fact that you don't see evidence of
damage merely means that in the cases you have observed either the temperature
range is not very extreme or the slab is free to move on the opposite end. And
unless pressure treated wood is used the termites would make quick work of it,
at least in my area they would.

Regards,

John

You have a point, however the screw and hammer is not a good
analogy to the wood expansion joint. In some part of the
country wood expansion joints are common and standard
practice, the screw and hammer is neither common nor a
standard practice. Oh, I thing -30 to 110 is a pretty
extreme range temperature range. And, termites are pretty
uncommon here, although based on the termite/pest control
companies a person moving to the area might be mislead. I
have never lived in a house and seen only one house (and
that may be suspect) that had some minor evidence of
termites. Untreated cedar in full contact with the soil or
buried commonly last 15-20 years here, and the untreated
(probably fir) expansion joints of my driveway have lasted
for 25 years and are still solid We just don't have
termites.

OTOH, tar/asphalt as a major ingredient (in fiber board or
other) is much more common for many types of
expansion/contraction joints and is certainly superior to
wood. A new common practice here for driveways is to pour
large surfaces as a block and then cut them with diamond
saws and caulk the saw cut.

All of this is probably minor compare to the common home
construction practice here of not making any provision for
curing concrete. I have regularly watched the construction
practices in subdivisions here and have only occassionally
seen any driveway covered with anything. Footings for crawl
spaces are commonly poured, the concrete not covered, and
the forms removed in 2 days. I have never seen the
foundation walls covered and the forms are often removed in
24 hours, and never left more than 48 hours unless it is a
holiday. Those foundations are poured in weather as hot as
100 degrees and as cold as 25 degrees with no provision for
maintaining moisture or preventing freezing.