concrete is hard and brittle
 

The basement floor and walls of my new house (in Indianapolis) were
poured with a 3500 lb mix = 5.5 bag mix. This sounds normal. So my
question is, what could cause this concrete to be harder and more
brittle than any other concrete I have ever drilled? Moisture starved
while curing? Curing in the winter? Here are 2 phenomena that did
not occur in my last 3 homes:

1) When I drill and install standard wall anchors, and screw in
standard zinc-plated screws, about 40% of the screws break.

2) When I drop something hard and heavy on the concrete, it chips out
a significant chunk.

Thanks,
Jim

"shedmeister" wrote in message
om...
The basement floor and walls of my new house (in Indianapolis) were
poured with a 3500 lb mix = 5.5 bag mix. This sounds normal. So my
question is, what could cause this concrete to be harder and more
brittle than any other concrete I have ever drilled? Moisture starved
while curing?
Looks like it, curing in cold weather will do that to, water evaporates
easily and the concrete never hardens enough. But you don't really care what
caused it, you want to fix it. If it is moisture starved adding water will
fix it. I would try to keep a spot (2' by 2' at least) wet for a few weeks.
A wet rag and keeping it wet will do that, than see if it still chips so
easily. How to fix the whole basement ? Ever wanted an inside swimming pool
?
Curing in the winter? Here are 2 phenomena that did
not occur in my last 3 homes:

1) When I drill and install standard wall anchors, and screw in
standard zinc-plated screws, about 40% of the screws break.
Try a new drill bit and be sure the hole is deep enough. This has nothing to
do with the concrete I think.

2) When I drop something hard and heavy on the concrete, it chips out
a significant chunk.

Thanks,
Jim

"shedmeister" wrote in message
om...
The basement floor and walls of my new house (in Indianapolis) were
poured with a 3500 lb mix = 5.5 bag mix. This sounds normal. So my
question is, what could cause this concrete to be harder and more
brittle than any other concrete I have ever drilled? Moisture starved
while curing? Curing in the winter? Here are 2 phenomena that did
not occur in my last 3 homes:

1) When I drill and install standard wall anchors, and screw in
standard zinc-plated screws, about 40% of the screws break.

2) When I drop something hard and heavy on the concrete, it chips out
a significant chunk.

Thanks,
Jim

This is Turtle.

I'm not a Concrete wizard but all the slab people will tell you that when it is
brittle it did not cure right. It being cured right can amount to most anything
that you do to pour the concrete. If a concrete company pours your slab and it
turns out brittle. Most will replace the slab for nothing. In this part of the
country they will pay to have it removed and poured again.

TURTLE

On 18 Nov 2004 15:44:25 -0800, someone wrote:

The basement floor and walls of my new house (in Indianapolis) were
poured with a 3500 lb mix = 5.5 bag mix.

If you really care about this, it is pretty routine though not
necessarily cheap to get concrete tested. The testing company can
come over and core out a sample. This sort of thing is done on
commercial work all the time.

*IF* the concrete is not up to spec, then you have a case to get it
replaced (or get $ to waive that). But you won't likely get "them" to
pay for it because you *claim* you don't *think* its right. More
like, YOU get it tested (don't you want the testers to work for you,
anyway?), THEN when you have the results go for new concrete plus the
test fee.

But from what I'm seeing, I'm not at all sure there is anything
"wrong" with it. Breaking screws because the concrete is really hard
wouldn't normally be considered a defect, there is no maximum hardness
spec'd. Maybe its a bum box of screws or not drilled deep enough!

Story about testing: (might be industrial legend). Foundary 'tested'
all its locomotive wheel casting by hitting them with a sledgehammer
to see if they rang true; a dull plonk indicated a major defect. One
day they started to get 100% rejects. The scrapeed a lot of new
castings before they realized it was the sledgehammer that had
developed a crack.

Good luck, but there may be nothing actually wrong.

-v.




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