# Footing Cure Time?



## fehujber (Feb 7, 2012)

Hi new to the board but BCO for several years, way back when, during my first season, my mentor had me reject a footing as the contractor had started laying block within a 72 hour window after pouring. At the time he rattled off an ACI section and the contractor complied and removed the offending foundation. I have operated unopposed within this premis ever since then and without having to officially support this in black and white .......until now. recently here in PA I had a CONtractor, begin drilling and inserting rods and commence block laying roughly 20 hours after pouring the footings (No it was not High and Early). When I found this I issued a verbal NOV to the owner, who has since contested the NOV. Now comes the problem I have researched the 2009 IRC and the ACI 332-08 and cannot lay my hands on a specific section requiring a specific period of time for various mixes to cure before commencement of further construction. Can anyone assist? Or do I have my foot in my  mouth??:banghd


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## Mule (Feb 7, 2012)

fehujber welcome to the board. I understand what you mean by enforcing a code that you can't find when someone call you out on it!

Unfortunately I can't help you with your question. I just wanted to welcome you! Someone will be along to help you out shortly!

Again welcome~


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## codeworks (Feb 7, 2012)

i dont have it here, but try aci 318, 72 hours seems right. it needs to at least get past the point of "green", set up, harden edges, etc. i've worked for guys that strip the next day, but wait asnother before strating to set formwork


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## fatboy (Feb 7, 2012)

We see contractors around here placing footings one day, strip the next and form walls, place walls the next. Less than 72 hours from excavation to dampproofing.


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## mtlogcabin (Feb 7, 2012)

It will depend on the season. Another jurisdiction adheres to the 72 hours. During the warm month we see 24 hrs then the form work goes up and the walls poured about 48 hours from footing pour. Cold weather requires blankets on the footing for 48 hours minimum.

1905.11 Curing.

The length of time, temperature and moisture conditions for curing of concrete shall be in accordance with ACI 318, Section 5.11.

1905.12 Cold weather requirements.

Concrete to be placed during freezing or near-freezing weather shall comply with the requirements of ACI 318, Section 5.12.

1905.13 Hot weather requirements.

Concrete to be placed during hot weather shall comply with the requirements of ACI 318, Section 5.13.


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## mtlogcabin (Feb 7, 2012)

My understanding from many years ago.

The 72 hours was the average time it took for concrete to reach 25% strength. However that is under normal weather conditions.


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## Papio Bldg Dept (Feb 7, 2012)

fatboy said:
			
		

> We see contractors around here placing footings one day, strip the next and form walls, place walls the next. Less than 72 hours from excavation to dampproofing.


same here.  sometimes the foundation guys are calling their inspections in before the footing.

most of our footing write-ups come on cold-weather and rain pours.


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## fatboy (Feb 7, 2012)

Oh, and welcome to the forum fehujber!


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## righter101 (Feb 7, 2012)

mtlogcabin said:
			
		

> It will depend on the season. Another jurisdiction adheres to the 72 hours. During the warm month we see 24 hrs then the form work goes up and the walls poured about 48 hours from footing pour. Cold weather requires blankets on the footing for 48 hours minimum. 1905.11 Curing.
> 
> The length of time, temperature and moisture conditions for curing of concrete shall be in accordance with ACI 318, Section 5.11.
> 
> ...


ACI 5.11 Provides the following:

"Concrete (other than high-early-strength) shall be maintained above 50 deg. F and in a moist condition for at least the first 7 days after placement, except when cured in accordance with 5.11.3.


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## brudgers (Feb 7, 2012)

Concrete does not need to be fully cured before CMU walls can be erected.

  1000 lbs of loading per square foot is less than 8 psi - i.e. not even 00.5% of final strength for 3000psi concreted

  And of course, type III cement develops most of its strength within 24 hours - if early loading with full structural loads is critical.

  In other words, you have picked up the bad habit of making up code out of whole cloth.

  The best course would, of course, be to just enforce the code as written.


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## Mark K (Feb 7, 2012)

brudgers is on the right track.  You can start building on the concrete as soon as you walk on it as long as you do not damage the concrete in any way that impacts its final performance.

Note the special inspection requirement to verify curing in Table 1705.3 in the 2012 IBC.

The code is focused on performance of the completed construction.


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## mtlogcabin (Feb 7, 2012)

> The best course would, of course, be to just enforce the code as written.


The problem is it is not written in the code as to when concrete has reached sufficient strength to continue with different phases of construction.

The info you provide about type III cement developing most of its strength within 24 hours is not found in the codes.

The 72 hour number was picked up somewhere in some class or rule of thumb for inspectors to use just like some may pick up on your 24 hours with no code section to back it up


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## JBI (Feb 7, 2012)

fehujber - Welcome to the board. As evidenced above, opinions will vary. The answer you seek is indeed not written in the Code itself, but rather in the correct reference standard. ACI 318 is the concrete 'bible', and will contain prescriptive/empirical time frames. Design Professionals can justify reducing those times, as evidenced above albeit gruffly by Ben (aka brudgers). At 72 hours I believe concrete _generally speaking_ achieves 75% of design strength, but could be mistaken.

You made a call in the field, you were mistaken. Stuff happens. Admit your mistake, explain your reasoning, move past it. Just don't repeat the same mistake.

Get your hands on a copy of ACI 318 and do your 'homework'.  An edge-a-muh-cated Code Official is a CON-tractors' worst nightmare and a Contractors' best ally. I have more than once refused to do a wall inspection the day after the footings were cast. Usually a 4PM footing inspection that begins with 'Can you do a wall inspection first thing tomorrow morning?'. "No, I can't" "Why not?" "Because the concrete will be too green to support the forms..." (of course in my head it is a much different conversation). If they're in that big a hurry, get the DPR to document the design change (most plans say 'per ACI 318').


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## brudgers (Feb 7, 2012)

mtlogcabin said:
			
		

> The problem is it is not written in the code as to when concrete has reached sufficient strength to continue with different phases of construction.


  No.  The problem is that when the code is silent on an issue about which a code official was completely ignorant, the code official made something up.

  He then taught another code official that that was the proper procedure.


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## brudgers (Feb 7, 2012)

JBI said:
			
		

> fehujber - Welcome to the board. As evidenced above, opinions will vary. The answer you seek is indeed not written in the Code itself, but rather in the correct reference standard. ACI 318 is the concrete 'bible', and will contain prescriptive/empirical time frames. Design Professionals can justify reducing those times, as evidenced above albeit gruffly by Ben (aka brudgers). At 72 hours I believe concrete _generally speaking_ achieves 75% of design strength, but could be mistaken.   You made a call in the field, you were mistaken. Stuff happens. Admit your mistake, explain your reasoning, move past it. Just don't repeat the same mistake.   Get your hands on a copy of ACI 318 and do your 'homework'.  An edge-a-muh-cated Code Official is a CON-tractors' worst nightmare and a Contractors' best ally. I have more than once refused to do a wall inspection the day after the footings were cast. Usually a 4PM footing inspection that begins with 'Can you do a wall inspection first thing tomorrow morning?'. "No, I can't" "Why not?" "Because the concrete will be too green to support the forms..." (of course in my head it is a much different conversation). If they're in that big a hurry, get the DPR to document the design change (most plans say 'per ACI 318').


  It doesn't need 75% of it's design strength to support a typical masonry wall during construction - or even a quite unusual one.


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## Rio (Feb 8, 2012)

We've stripped forms many times the same day we've placed the concrete.  We do this because the forms are much easier to strip, and also easier to clean.  Once it starts kicking it's not going anywhere.


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## fehujber (Feb 8, 2012)

OK, first things first. Thanks for all the input, many cordial some gruff. To  both please understand my aim is to do things right, by the code as written OR REFERENCED, that is why I asked the question here and did not just stomp my feet and hold my breath and shout "Cause I'm the building inspector and I say so".:inspctr I have and will continue to admit mistakes and even apologize to contractors and homeowners when I am wrong. On the other hand if the IRC references ACI 332, 318, 308 then I will use them as tools to clarify and support my position. I have 332 but neither 318 or 308 and was simply asking if anyone could offer me a quote from either.

I only want to enforce supportable positions on code. :agree


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## Darren Emery (Feb 8, 2012)

brudgers said:
			
		

> No.  The problem is that when the code is silent on an issue about which a code official was completely ignorant, the code official made something up.
> 
> He then taught another code official that that was the proper procedure.


No.

The orginal code official (see post #1) made a call based upon his understanding of an ACI document that provided direction in an area where the code is silent.

Then he taught another code official what he thought was proper procedure.


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## brudgers (Feb 8, 2012)

fehujber said:
			
		

> OK, first things first. Thanks for all the input, many cordial some gruff. To  both please understand my aim is to do things right, by the code as written OR REFERENCED, that is why I asked the question here and did not just stomp my feet and hold my breath and shout "Cause I'm the building inspector and I say so".:inspctr I have and will continue to admit mistakes and even apologize to contractors and homeowners when I am wrong. On the other hand if the IRC references ACI 332, 318, 308 then I will use them as tools to clarify and support my position. I have 332 but neither 318 or 308 and was simply asking if anyone could offer me a quote from either.  I only want to enforce supportable positions on code. :agree


  In so far as I recall, ACI 318 etc. are silent on the issue at hand because the necessary strength for further work is only a Potential design issue relative to a particular project, and under ordinary circumstances it is not an issue because concrete rapidly gains strength during hydration.  What ACI does have is hot and cold weather placement requirements to insure that standard building schedules can be met in different types of weather.

  What ACI does have is curing requirements to insure that the concrete meets it's design strength after 28 days.

  Back when I worked in the precast industry, we used a lot of TYPE III cement so that large structural members poured late in the afternoon could be stripped from the forms early the next morning - i.e. the concrete had to bond sufficiently to the tensile steel to allow the piece to be lifted by crane and stored at it's bearing points within eight hours (4000psi @ 24 hours).

  In my opinion, if you don't actually know what is in ACI 318, you damn well shouldn't be pretending to enforce it.  And regarding my gruffness, you've had ever since "way back when" to obtain a copy (less than $200) and read it.


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## brudgers (Feb 8, 2012)

Darren Emery said:
			
		

> No.  The orginal code official (see post #1) made a call based upon his understanding of an ACI document that provided direction in an area where the code is silent.    Then he taught another code official what he thought was proper procedure.


  Darren, building codes are not some oral tradition.  It's a written one.

  And anyone who doesn't read the codes for theirself, has no business being in a position of responsibility.

  ACI 318 is $160.

  Forcing the public to tear out walls and wait a week before going vertical because someone cannot be bothered to read it, is inexcusable given the relative costs of construction.


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## fehujber (Feb 8, 2012)

Shame is I thought I was dealing with gentlemen here


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## Papio Bldg Dept (Feb 8, 2012)

fehujber said:
			
		

> Shame is I thought I was dealing with gentlemen here


As you graciously stated in a previous post, you came here looking for insight (and code quotes) to assist you in making the correct decision.  Regardless of the manner in which it was given, there has been some helpful direction offered, and it is for you to sift through and derive your next course of action.  From what you have posted, I feel confident you are headed in the right direction, even if you didn't receive the specific code citation you originally hoped for.  In many cases, the code doesn't give us a verbatim holy grail, even though some claim to already have one (silly french).


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## fehujber (Feb 8, 2012)

Please make no mistake. If I am wrong I learn and apologize. If there is no section supporting my position it stops then and there. I have had many instances when I was unable to recall or find a specific code section. I have even suspended enforcement of specifics when I was unable to put my fingers on what I knew was there, but once I find it don't mess with me again. In this case I have been following a standard that was taught to me years ago if it is wrong it is wrong and I will cease enforcement in this direction. No problem. What really agrivates me is a pompous person beating me up for the error of trusting a person who was considered extremely knowledgeable in code. I should add that when this particular point was "taught" to me I disagreed having come out of 40+ years of construction and thousands of feet of footings, retaining walls, endwalls, headwalls, curb and sidewalk, (all of it still standing) but you did NOT question that boss/mentor.  In most of my prior positions I have had the ACI library at my disposal however the Township I am currently in does NOT have it. I figured this would be a good source for some clarity. I did receive many good answers and am grateful for all input, but I don't need 'tude.


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## David Henderson (Feb 8, 2012)

One must have thick skin on this forum just don't take anything personal


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## Papio Bldg Dept (Feb 8, 2012)

fehujber said:
			
		

> but I don't need 'tude.


Agreed.  I was suprised myself how few resources most smaller Building Departments have.  We often pass on (and receive) our "gently" used copies of codes and standards to other jurisdictions through our local Code Officials Association.


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## Mark K (Feb 8, 2012)

The relevant provision of ACI 318 is Section 6.2 dealing with removal of forms, shores, and re shoring.  In this section dealing with removal of forms and shoring they are talking about suspended slabs and not slabs on grade.  Earlier ACI 318 mentions that the code does not apply to typical slabs on grade.

The key point is that for suspended concrete construction you do not remove the shoring until the concrete is strong enough to reach its strength.  If removal is before the implied 28 days then there should be concrete cylinder results.

I believe that there is also a requirement that the concrete strength reach a certain value before application of post tensioning reinforcement but you will not have post tensioning unless there is an engineer involved

The basic rule is that if the design is fully compliant with the IRC there should not be a problem.  If there is an engineer on the project the engineer on the project should make the call when this is important.  Beyond Section 6.2 an inspector without engineering training will not be able to interpret ACI 318 to make a determination.

If there is an engineer on the project and the inspector cannot find any reference to when forms and shores can be removed it would be appropriate to ask that the engineer clarify the documents.

What this points out is that there is a strong oral tradition whereby information is passed down from individual to another and as a result it is often wrong.  When this happens we do things without knowing.  Supervisors are not always right.  This does not mean that you do not do what you are told.

On a related subject if a building is designed by an engineer the plan checker for the structural work should be an engineer.   A building official who takes the attitude that an engineering plan check is not needed because there is a professional engineering stamp is not fulfilling his duty.


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## brudgers (Feb 8, 2012)

fehujber said:
			
		

> Please make no mistake. If I am wrong I learn and apologize. If there is no section supporting my position it stops then and there. I have had many instances when I was unable to recall or find a specific code section. I have even suspended enforcement of specifics when I was unable to put my fingers on what I knew was there, but once I find it don't mess with me again. In this case I have been following a standard that was taught to me years ago if it is wrong it is wrong and I will cease enforcement in this direction. No problem. What really agrivates me is a pompous person beating me up for the error of trusting a person who was considered extremely knowledgeable in code. I should add that when this particular point was "taught" to me I disagreed having come out of 40+ years of construction and thousands of feet of footings, retaining walls, endwalls, headwalls, curb and sidewalk, (all of it still standing) but you did NOT question that boss/mentor.  In most of my prior positions I have had the ACI library at my disposal however the Township I am currently in does NOT have it. I figured this would be a good source for some clarity. I did receive many good answers and am grateful for all input, but I don't need 'tude.


You had that much field experience and didn't know that inspectors are quite often FOS? (just like everyone else)

_Argumentum ad verecundiam_ is typically considered fallacious reasoning, and it is good that you are questioning it.

But the best solution still requires a purchase of the relevant document.

As for attitude, "CONtractor" does not indiate a professional one.


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## brudgers (Feb 8, 2012)

Papio Bldg Dept said:
			
		

> Agreed.  I was suprised myself how few resources most smaller Building Departments have.  We often pass on (and receive) our "gently" used copies of codes and standards to other jurisdictions through our local Code Officials Association.


A professional can always purchase a copy on their own before they require stuff to be torn out and redone.

Sorry, I don't buy the excuse.


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## Papio Bldg Dept (Feb 8, 2012)

brudgers said:
			
		

> A professional can always purchase a copy on their own before they require stuff to be torn out and redone.Sorry, I don't buy the excuse.


An excuse is always an excues.  Yes they can, and should...and I don't believe that excuse is still for sale in this thread.  It is, however, the current reality, and circumstances leading to that reality are irrelevant in terms of what actions are to be taken going forward.  When I came over from the private sector, I was not allowed to bring the firm's library with me, and on the meager salary I received, was unable to afford duplicating that library with one simple amazonian purchase.  Each year I make it a priority to ensure that we assign and spend as much of our budget towards that end, however in the meantime we look to our neighboring jurisdictions to assist us with specific references, much as this forum does, and in some cases turn to specialized professionals for guidance.


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## fehujber (Feb 8, 2012)

Perhaps in my brevity I misled. I did not force the removal, My superior insisted I reject the footing. The contractor questioned and objected, my superior quoted the ACI and had the wall removed. THIS WAS IN 2006!!!! I simply asked (last week) that the contractor wait for adequete strength prior to drilling 8" into fresh concrete and was met with resistance. The story about removal was just for background.


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## gbhammer (Feb 8, 2012)

fehujber welcome, and please don't take offense to the yapping. We all have our crosses to bear and occassionaly "Solum gratia", like simon the people on this forum will help.


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## That Inspector Guy (Feb 11, 2012)

brudgers said:
			
		

> A professional can always purchase a copy on their own before they require stuff to be torn out and redone.Sorry, I don't buy the excuse.


What exactly do you know about being professional? From what I see here, zero!


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## Sandman (Feb 12, 2012)

USACE Specifications for Cast in Place Concrete based on ACI MCP-4 and ASTM C39 (referenced in IBC);

3.3.11 Removal of Forms and Supports

After placing concrete, forms must remain in place for the time periods specified in ACI/MCP-4. Do not remove forms and shores (except those used for slabs on grade and slip forms) until the client determines that the concrete has gained sufficient strength to support its weight and superimposed loads. Base such determination on compliance with one of the

following:

a. The plans and specifications stipulate conditions for removal of forms and shores, and such conditions have been followed, or

b. The concrete has been properly tested with an appropriate ASTM standard test method designed to indicate the concrete compressive strength, and the test results indicate that the concrete has gained sufficient strength to support its weight and superimposed loads.

Prevent concrete damage during form removal. Clean all forms immediately after removal.

3.3.11.1 Special Requirements for Reduced Time Period

Forms may be removed earlier than specified if ASTM C39/C39M test results of field-cured samples from a representative portion of the structure indicate that the concrete has reached a minimum of 85 percent of the design strength.


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## Mark K (Feb 12, 2012)

I assume that ACI MCP-4 refers to the 2004 edition of the ACI Manual of Concrete Practice.   The ACI MCP includes many documents that are not always consistent with each other, some of which are guidelines and others are standards.  Thus from a contractual perspective this reference is almost meaningless.

Putting the validity of the reference asside the concerns they are dealing with are already addressed in ACI 318 as noted above.  The issue is confused by the fact that USACE has decided, as an owner, to get  involved in signing work off before the contractor proceeds.  This approach is not reflected in the IBC.


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## Architect1281 (Feb 12, 2012)

Think Practical! I can pour 10 or 12 feet in height of concrete on a uniform fill form 150 #/cf so 1500 to 1800#s all at once

instant dead load so half that in CMU  dead no live load not an issue


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## Architect1281 (Feb 12, 2012)

It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so.”

 Mark Twain


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## Sandman (Feb 14, 2012)

This is the non-BS answer from ACI (similar to USACE specifications) http://www.concrete.org/FAQ/afmviewfaq.asp?faqid=28:

Technical Questions - ACI Concrete Knowledge Center

Stripping time for forms

--------------------------------------------------------------------------------

 Q. Does ACI provide information on how long to wait before stripping forms?

A. There are some important general requirements related to stripping time in ACI 318-05, Building Code Requirements for Structural Concrete. Section 6.2.1 states:

“Forms shall be removed in such a manner as not to impair safety and serviceability of the structure. Concrete exposed by form removal shall have sufficient strength not to be damaged by removal operation.”

There are additional default requirements contained in 301-05, "Specifications for Structural Concrete," the primary one being in Section 2.3.2.5:

“Unless otherwise specified, leave formwork and shoring in place to support the weight of concrete in beams, slabs, and in-place structural members until concrete has reached fc′…”

ACI 347-04, “Guide to Formwork for Concrete,” Section 3.7.1, gives direction regarding who is responsible for determining when the form stripping operation can begin:

“Although the contractor is generally responsible for design, construction, and safety of formwork, criteria for removal of forms or shores should be specified by the engineer/architect.”

As stated in ACI SP-4, Formwork for Concrete:

“Since early form removal is usually desirable so that forms can be reused, a reliable basis for determining the earliest proper stripping time is necessary. When forms are stripped, there must be no excessive deflection or distortion and no evidence of cracking or other damage to the concrete, due either to removal of support or to the stripping operation. Supporting forms and shores must not be removed from beams, floors, and walls until these structural units are strong enough to carry their own weight and any approved superimposed load, unless provision has been made to allow for anticipated temporary construction loads, as for example in multistory work. In no case should forms and shores be removed from horizontal members before concrete has reached the strength specified by the engineer/architect for form removal.”

ACI 347.2R-05, “Guide for Shoring/Reshoring of Concrete Multistory Buildings,” provides detailed information regarding the practice of stripping formwork and placing reshores in multistory building construction.


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## Mark K (Feb 14, 2012)

ACI 301, ACI 347, ACI 347.2R, and ACI SP-4 are not referenced in the building code and cannot be relied on by the building official unless the Owner's engineer voluntarily referenced them is the construction documents.  There is a difference between ACI providing guidance on a topic and the building official being able to enforce compliance with that guidance.

ACI 347, ACI 347.2R, and ACI SP-4 are guides and are not written in mandatory language.  It is ACI's position that Guides and similar documents should not be referenced in project specifications for these reasons.  This position is clearly printed on the first page of each of these documents.

Thus ACI 318 Section 6.2 is the only thing that a building official can fall back on.  The reality is that for residential projects permitted by the IRC, with no engineer involved, it is very very unlikely that a problem will result from building on young concrete. Two possible areas of concern are concrete trucks driving on green concrete and agressive backfilling retaining walls before the concrete got strong enough.


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## mtlogcabin (Feb 14, 2012)

I was talking to one of our contractors who specilized in concrete work for over 20 years in CA. When I asked him about a requirement to wait 72 hours before stripping forms he said it was a standard practice because the form boards aided in keeping moisture in the concrete and thus helped in reaching the proper strength. Now he was talking multiple story concrete buildings not SFR's


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## Mule (Feb 29, 2012)

Just set the concrete on fire and see if it passes strength tests!


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## David Henderson (Feb 29, 2012)

If anybody has a ASTM book it will probably tell you the answer, don't have mine with me.


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## brudgers (Feb 29, 2012)

Mule said:
			
		

> Just set the concrete on fire and see if it passes strength tests!


  If you can set the concrete on fire, curing time is the least of your problems.


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## KZQuixote (Feb 29, 2012)

brudgers said:
			
		

> Concrete does not need to be fully cured before CMU walls can be erected.  1000 lbs of loading per square foot is less than 8 psi - i.e. not even 00.5% of final strength for 3000psi concreted
> 
> And of course, type III cement develops most of its strength within 24 hours - if early loading with full structural loads is critical.
> 
> ...


I agree, I've poured many footings and then come back after lunch and started setting wall forms. If you can walk on the footing you're good to go. These are not grade beams.

Bill


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## codeworks (Feb 29, 2012)

"and regarding my gruffness", i'm glad i don't deal with you on a daily basis, sir


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## gbhammer (Feb 29, 2012)

codeworks said:
			
		

> "and regarding my gruffness", i'm glad i don't deal with you on a daily basis, sir


I think that the only one getting called out for this was 'McGruff (he is a crime) Dog'


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