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RE: Concrete Wall Shrinkage & Construction Joints

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ACI 350.4R-04 states that the spacing of construction joints "should usually not exceed 60-ft, with 30 to 50-ft being more common" and notes that "extra horizontal reinforcement may be desirable near the base of wall to assist in control of cracks near the base".   Even at these spacings, the restraint at the base of wall due to attachment to the base slab relative to free movement at the top of wall tends to cause some vertical shrinkage cracks in the lower part of the wall.  I generally like to limit construction joint spacing to 40-ft maximum, but this is always a matter of judgment. 
 
Spacing of movement joints is addressed in ACI 350-01 Table 7.12.2.1.  Increased area of reinforcement permits increased joint spacing.  (Non-moving construction joints are not considered for these joint spacing limitations - I often provide the maximum steel percentage in the table and use large spacings for movement joints based on structure configuration.)
 
 
William C. Sherman, PE
(Bill Sherman)
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com
 


From: Rich Lewis [mailto:seaint03(--nospam--at)lewisengineering.com]
Sent: Monday, August 22, 2005 8:42 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Concrete Wall Shrinkage & Construction Joints

Thank you for this information.  I really appreciate it very much.  It pretty much follows the guideline details I have.

 

Is there a recommended or rule of thumb for spacing the construction joints?  I have an old PCA paper that says the shrinkage control joints should not exceed 25 feet.  Is there a practical reason to limit the length of pour of the wall between construction joints?

 

Thanks.

 

Rich

 

 


From: Sherman, William [mailto:ShermanWC(--nospam--at)cdm.com]
Sent: Sunday, August 21, 2005 10:23 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Concrete Wall Shrinkage & Construction Joints

 

I detail 3 general types of concrete joints:

 

1. Construction joints:  These are intended to act like monolithic concrete once complete, so the joint is bonded and reinforcing steel completely extends thru them.  They only dissipate shrinkage insofar as time is allowed between adjacent concrete placements.  

 

2. Contraction or Control Joints:  These are intended to allow shrinkage to occur and a crack to open at the joint.  The reinforcing steel is either fully interrupted or at least 50% of the steel is interrupted.  A bond breaker is applied to the formed joint surface, and smooth dowels may be provided where reinforcement is fully interrupted and if differential out of plane movement is desired to be controlled.  On one side of the joint, the dowel must be coated to prevent bond. 

 

3. Expansion and Isolation Joints:  These are intended to allow expansion or differential movement as well as shrinkage/contraction.  All reinforcing steel is interrupted but smooth dowels may be provided as noted above.  A gap is formed between adjacent concrete joint surfaces and is filled with a premolded joint filler. 

 

For liquid-containing structures, waterstops and joint sealants are also provided - see ACI 350.4R for examples of joints for such structures.

 

William C. Sherman, PE
(Bill Sherman)
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com


From: Rich Lewis [mailto:seaint03(--nospam--at)lewisengineering.com]
Sent: Sunday, August 21, 2005 2:02 PM
To: seaint(--nospam--at)seaint.org
Subject: Concrete Wall Shrinkage & Construction Joints

Does ACI have recommended details for shrinkage and construction joints in walls?  I have a 15” thick basement foundation wall that I want to include some details for.  I have seen some details where the main reinforcing stops and dowels are placed at the joint, both with shrinkage and construction joints.  Is this what most engineers typically detail?

 

Thanks.

 

Rich