Smooth dowels should be utilized to transfer loads between adjacent concrete slabs. This typically occurs where a pool deck abuts a building's foundation.
Required by Codes and Standards
The standards set forth by the American Concrete Institute (ACI) are incorporated in and adopted by almost every building code in the United States.
ACI 302.1R goes into great detail about the proper installation and requirements for doweling adjacent concrete slabs and foundations.
Freedom of Movement
Allowing the dowels to move freely within the slabs is one key requirement. This is why greasing, smooth bars and sleeving are key elements.
Smooth dowels are similar in dimensions to typical deformed reinforcement steel (rebar), except that smooth bars do not have any ridges (deformations) along their length. They are smooth...
Sleeving and greasing are two common methods to ensure that the dowels can slip freely within their cavities (when installed after one slab has hardened).
Dowel chairs (dowels supported on wire baskets) are commonly used when foresight allows their installation prior to the first concrete pour.
Cracking
The improper installation of dowels can lead to transfer cracking of either slab.
These are usually caused by the use of deformed bars, whose ridges grab within the drilled holes.
The transfer of stress, causes the bars to crack one or both slabs. Not a serious problem on a patio, but it can be a problem with building foundations, slab floors, highways and bridge decks. Cracks allow water intrusion and possible corrosion of the reinforcement steel. This is why most smooth bar dowels are epoxy coated.
Following the standard industry accepted methods and practices will prevent a lot of repair expenses later.
Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at:
info@aquatictechnology.com or 408-776-8220.
Visit his website at: www.aquatictechnology.com.
All Contents © Aquatic Technology Pool & Spa, 2013.
All rights reserved.
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Showing posts with label ACI. Show all posts
Showing posts with label ACI. Show all posts
Thursday, September 4, 2014
Monday, September 2, 2013
Concrete Filling Drilled Caissons - Don't just let the concrete fall
Filling drilled caissons with concrete - do not just let the concrete fall!
Free Fall
Recently, I was asked to weigh in on a project where the methods for placing concrete into drilled caissons were under debate.
The concrete contractor insisted that the concrete could be dropped from the surface down into the 40 foot hole. The swimming pool contractor did not feel comfortable with that, but did not know of any standards that dictated otherwise.
American Concrete Institute (ACI)
The ACI publishes a myriad of concrete standards. Most issues regarding concrete, are discussed in their standard ACI 318. ACI 318 has been adopted and incorporated into the International Building Code (IBC) as well as the California Building Code (CBC). The IBC is the basis for building codes relating to concrete, that have been adopted across the nation.
ACI 318 states that concrete should be placed as close to it's intended location as possible. So, in the case of drilled caissons, that means filling the hole from the bottom up. The weight of 40 feet of 3-4" concrete filled hose is unwielding. Usually a crane, backhoe or concrete boom is required to fill such deep holes.
California Building Code
The CBC is a little more compromising. It allows for the concrete to fall no more than 6 feet.
Separation
Why is there any concern at all? Separation.
If the concrete is allowed to fall a significant distance, the aggregate separates from the concrete. A homogenous mix is not delivered to the final resting place. Pumping the concrete from 40 feet also allows the concrete to bounce off of the reinforcing steel, also separating the aggregate from the cement.
To ensure that the specified mix design is delivered as specified, precise placement practices are critical.
Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: info@aquatictechnology.com or 408-776-8220.
Visit his website at: www.aquatictechnology.com.
All Contents © Aquatic Technology Pool & Spa, 2013.
All rights reserved.
Free Fall
Recently, I was asked to weigh in on a project where the methods for placing concrete into drilled caissons were under debate.
The concrete contractor insisted that the concrete could be dropped from the surface down into the 40 foot hole. The swimming pool contractor did not feel comfortable with that, but did not know of any standards that dictated otherwise.
American Concrete Institute (ACI)
The ACI publishes a myriad of concrete standards. Most issues regarding concrete, are discussed in their standard ACI 318. ACI 318 has been adopted and incorporated into the International Building Code (IBC) as well as the California Building Code (CBC). The IBC is the basis for building codes relating to concrete, that have been adopted across the nation.
ACI 318 states that concrete should be placed as close to it's intended location as possible. So, in the case of drilled caissons, that means filling the hole from the bottom up. The weight of 40 feet of 3-4" concrete filled hose is unwielding. Usually a crane, backhoe or concrete boom is required to fill such deep holes.
California Building Code
The CBC is a little more compromising. It allows for the concrete to fall no more than 6 feet.
Separation
Why is there any concern at all? Separation.
If the concrete is allowed to fall a significant distance, the aggregate separates from the concrete. A homogenous mix is not delivered to the final resting place. Pumping the concrete from 40 feet also allows the concrete to bounce off of the reinforcing steel, also separating the aggregate from the cement.
To ensure that the specified mix design is delivered as specified, precise placement practices are critical.
Contact the author, Paolo Benedetti of Aquatic Technology Pool and Spa at: info@aquatictechnology.com or 408-776-8220.
Visit his website at: www.aquatictechnology.com.
All Contents © Aquatic Technology Pool & Spa, 2013.
All rights reserved.
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