I just finished pouring footings...

Turns out the only day the kid can help me with the slab is tommorrow
P.M. or 48 hours after the footings. I surfed the web to verify this
is enough cure time, tons of stuff about 1 week and longer vs. time,
could find nada about two days.

I wanted to find PSI compressive strength estimate at 48hours.

Anyone know?

On Fri, 22 Aug 2014 11:59:45 -0500, Karl Townsend
wrote:

I just finished pouring footings...

Turns out the only day the kid can help me with the slab is tommorrow
P.M. or 48 hours after the footings. I surfed the web to verify this
is enough cure time, tons of stuff about 1 week and longer vs. time,
could find nada about two days.

I wanted to find PSI compressive strength estimate at 48hours.

Anyone know?

I have no experience with such short times. However, the research
shows that, at 50 hours and 70 deg. F, you have between 1/3 and 2/3 of
maximum strength.

Most mixes show around 40% of maximum strength. Higher-strength
mixtures generally show a higher percentage of strength at 50 hours;
weaker mixes show a lower percentage.

Good luck!

--
Ed Huntress

On Fri, 22 Aug 2014 13:27:03 -0400, Ed Huntress
wrote:

On Fri, 22 Aug 2014 11:59:45 -0500, Karl Townsend
wrote:

I just finished pouring footings...

Turns out the only day the kid can help me with the slab is tommorrow
P.M. or 48 hours after the footings. I surfed the web to verify this
is enough cure time, tons of stuff about 1 week and longer vs. time,
could find nada about two days.

I wanted to find PSI compressive strength estimate at 48hours.

Anyone know?

I have no experience with such short times. However, the research
shows that, at 50 hours and 70 deg. F, you have between 1/3 and 2/3 of
maximum strength.

Most mixes show around 40% of maximum strength. Higher-strength
mixtures generally show a higher percentage of strength at 50 hours;
weaker mixes show a lower percentage.

Good luck!

Thanks Ed. I just did a rough calc of 400 lb/ft2 max force on the
footing for the final pour so I'm in great shape. I had guessed the
number to be three times that. i guess that's why we do engineering.

Sorry about the **** match below.

karl

On Fri, 22 Aug 2014 16:38:31 -0500, Karl Townsend
wrote:

On Fri, 22 Aug 2014 13:27:03 -0400, Ed Huntress
wrote:

On Fri, 22 Aug 2014 11:59:45 -0500, Karl Townsend
wrote:

I just finished pouring footings...

Turns out the only day the kid can help me with the slab is tommorrow
P.M. or 48 hours after the footings. I surfed the web to verify this
is enough cure time, tons of stuff about 1 week and longer vs. time,
could find nada about two days.

I wanted to find PSI compressive strength estimate at 48hours.

Anyone know?

I have no experience with such short times. However, the research
shows that, at 50 hours and 70 deg. F, you have between 1/3 and 2/3 of
maximum strength.

Most mixes show around 40% of maximum strength. Higher-strength
mixtures generally show a higher percentage of strength at 50 hours;
weaker mixes show a lower percentage.

Good luck!

Thanks Ed. I just did a rough calc of 400 lb/ft2 max force on the
footing for the final pour so I'm in great shape. I had guessed the
number to be three times that. i guess that's why we do engineering.

Sorry about the **** match below.

karl

Eh, what else is new? d8-)

Lloyd doesn't usually start off like that. Maybe he had a bad day.

--
Ed Huntress

Ed Huntress fired this volley in
:

Lloyd doesn't usually start off like that. Maybe he had a bad day.

Lloyd had a real bad day... Customer to whom I'm delivering a $250K
machine Monday (this Monday coming) called to say that per the Army the
specs had changed. It'll take about $5K and three weeks to change.
They'll pay... in about five months... but in the meantime, I'm hanging
on the hook for salaries, overhead, and materials for the changes and the
time. And no pay for the machine itself until they 'approve' it, as
delivered.

Sorry for my outburst. That's not me, usually. I'm just generally
****ed today; even at myself.

LLoyd

On Fri, 22 Aug 2014 17:29:19 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Ed Huntress fired this volley in
:

Lloyd doesn't usually start off like that. Maybe he had a bad day.

Lloyd had a real bad day... Customer to whom I'm delivering a $250K
machine Monday (this Monday coming) called to say that per the Army the
specs had changed. It'll take about $5K and three weeks to change.
They'll pay... in about five months... but in the meantime, I'm hanging
on the hook for salaries, overhead, and materials for the changes and the
time. And no pay for the machine itself until they 'approve' it, as
delivered.

Sorry for my outburst. That's not me, usually. I'm just generally
****ed today; even at myself.

LLoyd

Oh, jeez! Bad day ain't the word for it. Sheesh.

Hey, Lloyd, if it makes you feel any better, you can call me some of
the names that Klaus calls me. d8-)

--
Ed Huntress

On Friday, August 22, 2014 6:29:19 PM UTC-4, Lloyd E. Sponenburgh wrote:
Ed Huntress fired this volley in

:

Lloyd doesn't usually start off like that. Maybe he had a bad day.

Lloyd had a real bad day.. Customer to whom I'm delivering a $250K

machine Monday (this Monday coming) called to say...

Lloyd you have a bad day every day. Cut the bullcrap excuses.

So long as you keep it wet, you can also hurry things along by getting
it hotter - so if the sun is shining for you, toss some plastic over it,
with a soaker hose under if needed. "Standard cure temp" is 70F - about
twice as slow at 50 F, about twice as fast at 90F, and darn fast if you
have an autoclave handy...

ie, 3-1/2 days at 90F and 14 days at 50F are both about the same as a
"standard" 7 day cure at 70F - so long as you keep it wet.

--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.

Karl Townsend fired this volley in
:

I just finished pouring footings...

Turns out the only day the kid can help me with the slab is tommorrow
P.M. or 48 hours after the footings. I surfed the web to verify this
is enough cure time, tons of stuff about 1 week and longer vs. time,
could find nada about two days.

I wanted to find PSI compressive strength estimate at 48hours.

Anyone know?

The old manual rule of thumb is 6-6-6-6. Six bags per yard (90lb
Portland), six gallons of water per bag, six percent entrained air, and
six days' wet cure.

At that point, it has to dry enough for the surface to harden. The
compression strength is up by then, but marring of the surface can easily
occur until it's visibly dry. Of course, that's no issue with footers,
only the slab.

Lloyd

Lloyd

On Fri, 22 Aug 2014 13:01:58 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Karl Townsend fired this volley in
:

I just finished pouring footings...

Turns out the only day the kid can help me with the slab is tommorrow
P.M. or 48 hours after the footings. I surfed the web to verify this
is enough cure time, tons of stuff about 1 week and longer vs. time,
could find nada about two days.

I wanted to find PSI compressive strength estimate at 48hours.

Anyone know?

The old manual rule of thumb is 6-6-6-6. Six bags per yard (90lb
Portland), six gallons of water per bag, six percent entrained air, and
six days' wet cure.

At that point, it has to dry enough for the surface to harden. The
compression strength is up by then, but marring of the surface can easily
occur until it's visibly dry. Of course, that's no issue with footers,
only the slab.

Lloyd

Lloyd

I don't know about that "rule of thumb," Lloyd, but concrete hardens
best when it's completely under water. You don't want it to dry at
all. And the surface should harden even when it's soaking wet, if the
mix wasn't too wet to begin with.

Once it dries, the hardening cure stops. It can't be restored. So,
whether it's a couple of days or a couple of years, that's the end of
the road for continued hardening.

Maximum strength is obtained in about three years of continuous
soaking, but the gain after 28 days (a standard for measuring maximum
strength) is very small.

When ferrocement boats were all the rage, back in the '70s, some of
the larger ones were finished and then intentionally sunk and kept
under water for a year. They were made with a standard sand mix, like
some kinds of mortar.

--
Ed Huntress

Ed Huntress fired this volley in
:

I don't know about that "rule of thumb," Lloyd, but concrete hardens
best when it's completely under water. You don't want it to dry at
all. And the surface should harden even when it's soaking wet, if the
mix wasn't too wet to begin with.

You don't read, do you, Ed?

What about "six days' WET cure" didn't you understand?
The surface will not become durable until it dries, but it has to cure
throughout first.

Pay attention. You might learn something -- like how to read.

Lloyd

On Fri, 22 Aug 2014 13:34:56 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Ed Huntress fired this volley in
:

I don't know about that "rule of thumb," Lloyd, but concrete hardens
best when it's completely under water. You don't want it to dry at
all. And the surface should harden even when it's soaking wet, if the
mix wasn't too wet to begin with.

You don't read, do you, Ed?

What about "six days' WET cure" didn't you understand?

Oh, I think I understand it pretty well, Lloyd

The surface will not become durable until it dries, but it has to cure
throughout first.

The surface is "durable" as soon as it cures. It has nothing to do
with "drying," unless you screwed up.


Pay attention. You might learn something -- like how to read.

Ok, Mr. Over-the-Top. For almost 20 years, I studied, wrote about, and
experimented with post-tensioned concrete and ferrocement. I'm well
aware of how Portland cement concrete cures.

Your comments suggest that, like many concrete workers, you're used to
working with overly wet mixtures that are soft on top, NOT because
there was water on top, but because the mix was too wet to begin with
and settled out before it cured, it was poorly mixed, or it was hit
too hard with a hose as soon as it was poured. Portland cement does
NOT harden upon "drying."

Now, you want to challenge that? Go ahead.

--
Ed Huntress

Ed Huntress fired this volley in
:

Portland cement does
NOT harden upon "drying."



It's a pity, that after those decades of 'study' you never learned
anything about surfacing and finishing.

Structural strength is the most important aspect, of course, but you
obviously haven't a clue about what it takes to make 'skating rink'
quality finishes.

A wet portland surface marrs more easily than a dry one.

Even 'burnt' hard-trowled finishes must dry before friction traffic is
allowed on them.

No, I'm not one of those idiots who thinks "concrete has to dry to cure".
I know for a fact that a finished surface on a Portland slab has to dry
to achieve ultimate durability.

"Post-tensioning" and "ferro-cement" are affiliated with structures, not
finishes.

Like I said... you don't read, even about what you 'study' for 20 years.

LLoyd

Ed Huntress on Fri, 22 Aug 2014 14:12:40
-0400 typed in rec.crafts.metalworking the following:
On Fri, 22 Aug 2014 13:01:58 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Karl Townsend fired this volley in
m:

I just finished pouring footings...

Turns out the only day the kid can help me with the slab is tommorrow
P.M. or 48 hours after the footings. I surfed the web to verify this
is enough cure time, tons of stuff about 1 week and longer vs. time,
could find nada about two days.

I wanted to find PSI compressive strength estimate at 48hours.

Anyone know?

The old manual rule of thumb is 6-6-6-6. Six bags per yard (90lb
Portland), six gallons of water per bag, six percent entrained air, and
six days' wet cure.

At that point, it has to dry enough for the surface to harden. The
compression strength is up by then, but marring of the surface can easily
occur until it's visibly dry. Of course, that's no issue with footers,
only the slab.

Lloyd

Lloyd

I don't know about that "rule of thumb," Lloyd, but concrete hardens
best when it's completely under water. You don't want it to dry at
all. And the surface should harden even when it's soaking wet, if the
mix wasn't too wet to begin with.

Ah, that explains why my dad covered the patio with burlap bags
and kept wetting them down.

Once it dries, the hardening cure stops. It can't be restored. So,
whether it's a couple of days or a couple of years, that's the end of
the road for continued hardening.

Maximum strength is obtained in about three years of continuous
soaking, but the gain after 28 days (a standard for measuring maximum
strength) is very small.

When ferrocement boats were all the rage, back in the '70s, some of
the larger ones were finished and then intentionally sunk and kept
under water for a year. They were made with a standard sand mix, like
some kinds of mortar.
--
pyotr filipivich
"With Age comes Wisdom. Although more often, Age travels alone."

On Fri, 22 Aug 2014 12:55:52 -0700, pyotr filipivich
wrote:

Ed Huntress on Fri, 22 Aug 2014 14:12:40
-0400 typed in rec.crafts.metalworking the following:
On Fri, 22 Aug 2014 13:01:58 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Karl Townsend fired this volley in
:

I just finished pouring footings...

Turns out the only day the kid can help me with the slab is tommorrow
P.M. or 48 hours after the footings. I surfed the web to verify this
is enough cure time, tons of stuff about 1 week and longer vs. time,
could find nada about two days.

I wanted to find PSI compressive strength estimate at 48hours.

Anyone know?

The old manual rule of thumb is 6-6-6-6. Six bags per yard (90lb
Portland), six gallons of water per bag, six percent entrained air, and
six days' wet cure.

At that point, it has to dry enough for the surface to harden. The
compression strength is up by then, but marring of the surface can easily
occur until it's visibly dry. Of course, that's no issue with footers,
only the slab.

Lloyd

Lloyd

I don't know about that "rule of thumb," Lloyd, but concrete hardens
best when it's completely under water. You don't want it to dry at
all. And the surface should harden even when it's soaking wet, if the
mix wasn't too wet to begin with.

Ah, that explains why my dad covered the patio with burlap bags
and kept wetting them down.

Yep, that's the common old method, and it's still a good one. You
don't want any water standing on it until it reaches an initial cure
(I forget the stages of cure). After that, keep it as wet as you can
for as long as you can, if you want maximum strength. If it dries out,
curing is done for.


Once it dries, the hardening cure stops. It can't be restored. So,
whether it's a couple of days or a couple of years, that's the end of
the road for continued hardening.

Maximum strength is obtained in about three years of continuous
soaking, but the gain after 28 days (a standard for measuring maximum
strength) is very small.

When ferrocement boats were all the rage, back in the '70s, some of
the larger ones were finished and then intentionally sunk and kept
under water for a year. They were made with a standard sand mix, like
some kinds of mortar.
--
pyotr filipivich
"With Age comes Wisdom. Although more often, Age travels alone."

Ed Huntress fired this volley in
:

Yep, that's the common old method, and it's still a good one. You
don't want any water standing on it until it reaches an initial cure
(I forget the stages of cure).

It's _easy_ to tell when that 'initial cure' has occurred. When the
concrete sucks up all of its surface water, and becomes 'solid' (not dry)
to the touch, the initial cure has occurred. You can scratch it with a
fingernail, but not disturb the surface with the ball of your finger.

At that point, if you're not finishing, let it sit another couple of
hours to make sure the whole of the surface is at the same level of cure,
then gently flood it with water, and keep it that wet for six days.
It'll achieve about 75% of it's ultimate strength in (about) six days.

If you want to finish it, on the other hand, you have mere minutes to get
trowels on the surface before it becomes too hard to move the surface
material around. For 'hard troweling', you may have to do it in steps,
because when you move the cement (not the aggs) around, you break up the
gypsum crystals it's forming; it becomes motile again, and must re-cure
for a time between trowelings.

Lloyd

pyotr filipivich wrote:
Ed Huntress on Fri, 22 Aug 2014 14:12:40
-0400 typed in rec.crafts.metalworking the following:
On Fri, 22 Aug 2014 13:01:58 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Karl Townsend fired this volley in
:

I just finished pouring footings...

Turns out the only day the kid can help me with the slab is
tommorrow P.M. or 48 hours after the footings. I surfed the web to
verify this is enough cure time, tons of stuff about 1 week and
longer vs. time, could find nada about two days.

I wanted to find PSI compressive strength estimate at 48hours.

Anyone know?

The old manual rule of thumb is 6-6-6-6. Six bags per yard (90lb
Portland), six gallons of water per bag, six percent entrained air,
and six days' wet cure.

At that point, it has to dry enough for the surface to harden. The
compression strength is up by then, but marring of the surface can
easily occur until it's visibly dry. Of course, that's no issue
with footers, only the slab.

Lloyd

Lloyd

I don't know about that "rule of thumb," Lloyd, but concrete hardens
best when it's completely under water. You don't want it to dry at
all. And the surface should harden even when it's soaking wet, if the
mix wasn't too wet to begin with.

Ah, that explains why my dad covered the patio with burlap bags
and kept wetting them down.

Once it dries, the hardening cure stops. It can't be restored. So,
whether it's a couple of days or a couple of years, that's the end of
the road for continued hardening.

Maximum strength is obtained in about three years of continuous
soaking, but the gain after 28 days (a standard for measuring maximum
strength) is very small.

When ferrocement boats were all the rage, back in the '70s, some of
the larger ones were finished and then intentionally sunk and kept
under water for a year. They were made with a standard sand mix, like
some kinds of mortar.

Does this mean the stonework I'm doing wood stove pad of 2"+- Arkansas
field stone, then up the wall with same has to be covered with wet burlap
for 6 days ? I sure don't want the concrete to be weak !

--
Snag

On Fri, 22 Aug 2014 18:20:23 -0500, "Terry Coombs"
wrote:

pyotr filipivich wrote:
Ed Huntress on Fri, 22 Aug 2014 14:12:40
-0400 typed in rec.crafts.metalworking the following:
On Fri, 22 Aug 2014 13:01:58 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Karl Townsend fired this volley in
:

I just finished pouring footings...

Turns out the only day the kid can help me with the slab is
tommorrow P.M. or 48 hours after the footings. I surfed the web to
verify this is enough cure time, tons of stuff about 1 week and
longer vs. time, could find nada about two days.

I wanted to find PSI compressive strength estimate at 48hours.

Anyone know?

The old manual rule of thumb is 6-6-6-6. Six bags per yard (90lb
Portland), six gallons of water per bag, six percent entrained air,
and six days' wet cure.

At that point, it has to dry enough for the surface to harden. The
compression strength is up by then, but marring of the surface can
easily occur until it's visibly dry. Of course, that's no issue
with footers, only the slab.

Lloyd

Lloyd

I don't know about that "rule of thumb," Lloyd, but concrete hardens
best when it's completely under water. You don't want it to dry at
all. And the surface should harden even when it's soaking wet, if the
mix wasn't too wet to begin with.

Ah, that explains why my dad covered the patio with burlap bags
and kept wetting them down.

Once it dries, the hardening cure stops. It can't be restored. So,
whether it's a couple of days or a couple of years, that's the end of
the road for continued hardening.

Maximum strength is obtained in about three years of continuous
soaking, but the gain after 28 days (a standard for measuring maximum
strength) is very small.

When ferrocement boats were all the rage, back in the '70s, some of
the larger ones were finished and then intentionally sunk and kept
under water for a year. They were made with a standard sand mix, like
some kinds of mortar.

Does this mean the stonework I'm doing wood stove pad of 2"+- Arkansas
field stone, then up the wall with same has to be covered with wet burlap
for 6 days ? I sure don't want the concrete to be weak !

It depends on what kind of mortar you're using. 'Better follow the
supplier's instructions.

--
Ed Huntress

On Fri, 22 Aug 2014 11:59:45 -0500, Karl Townsend
wrote:

I just finished pouring footings...

Turns out the only day the kid can help me with the slab is tommorrow
P.M. or 48 hours after the footings. I surfed the web to verify this
is enough cure time, tons of stuff about 1 week and longer vs. time,
could find nada about two days.

I wouldn't go near any poured footings for at least a week, Karl.
As important as they are, I definitely wouldn't fool with it.


I wanted to find PSI compressive strength estimate at 48hours.

Less than 50%, as stated by all the concrete guys I've talked with.
I've seen fence post crete jobs broken 2 days, splitting the
cylinder of crete in half when kids went climbing the crossbars before
pickets went up.


Anyone know?

http://www.forconstructionpros.com/a...th-of-concrete

--
The unexamined life is not worth living.
--Socrates

On 8/22/2014 11:59 AM, Karl Townsend wrote:
I just finished pouring footings...

Turns out the only day the kid can help me with the slab is tommorrow
P.M. or 48 hours after the footings. I surfed the web to verify this
is enough cure time, tons of stuff about 1 week and longer vs. time,
could find nada about two days.

I wanted to find PSI compressive strength estimate at 48hours.

Anyone know?

As I recall, just built a 26x70' steel building with 6" nominal floor
and beams and deep wells all around.

The cement guy stated 60% in 48 hours. They were driving a massive
beam fork lift up on it without issue, moving steel beams and heavy
iron. The bolts were tightened, but not hard, had to get the other
steel up in case it had to move a bit - wiggle room...

It depends partly on the formula and such. Mine was 7000 psi cement.
I have a 150 gallon fish tank 12" from the edge of the cement but it
sits on a pier the size of an icebox sideways and standing! My safe
is on a pier that is the size of a freezer downwards. We wanted to get
enough mass that it would not rotate under load.

Martin