Showing posts with label ASA. Show all posts
Showing posts with label ASA. Show all posts

Sunday, February 14, 2016

Sloppy pool construction practices

Which of these sloppy construction practices is your pool builder guilty of using? 

No soils reports (even in differential soils)?
Undermining the foundation of a house by digging too close?


Using flexible PVC tubing (meant for portable above grade spas) because they were too lazy to heat bend pipe?


Only install 2-bar bond beams?
Install reinforcing steel or pins in contact with the forms or earth?


Place your pipes directly on the earth, because trenching to place them below grade is too difficult?


Use the same steel schedule for every single project or utilize generic / mail order engineering without regard to surcharges (soil conditions, building foundations, hydrostatic conditions, wind loads, etc) ?
Use flimsy forms that do not provide a solid surface to shoot against (as required by ACI & ASA) ?



If your pool builder does not know why these practices are forbidden or against industry practices, then they need some training and education. Unfortunately, this is an industry of "on the job training"... but if the people they learned from were doing it wrong... the tradition continues !

Did you know that the International Building Code (IBC) and International Residential Codes (IRC) REQUIRE soils reports, project specific structural engineering (structures must be designed to overcome the anticipated loads) and minimum shell thicknesses? Some states have adopted their own more restrictive building codes (but they are based upon the IBC & IRC - e.g. CA & FL).

Most building departments that do not enforce their adopted building codes, do so, out of ignorance. The liability in the event of a failure, falls on the contractor, as the government has immunity. It is your builders responsibility to know the codes and to follow them.

Just because they have done it that way for 35 years, does not make it RIGHT... SAFE or LEGAL.

You should be constantly learning, something new everyday - then putting that into practice.  If you think that you "know it all," then it is time to retire.

I cannot count the number of times that pool builders in various courses or lectures have come up to me after and said, "You know we've been doing it that way for XX years. I never knew that it was wrong," "That explains why we have that type of failure constantly occurring," "I wish someone would have taught me the correct way years ago. It would have saved me thousands of dollars in remedial repairs."

EDUCATION is cheaper that demolition and lost consumer confidence.

No, I'm not saying all of this because I've been sued or have a vested financial interest in any education programs. I am saying this because I want to elevate the practice of building pools and make this industry better. Anyone who knows me, knows that though there are various techniques, there is only one way of doing something - the RIGHT WAY ! 

How do you know that your pool is being built in compliance with the building codes, if the local building inspector does not know what he is looking at?  Hire an independent inspector or "owner's representative" to ensure that your project is built "per code."

Paolo Benedetti, SWD Aquatic Artist, Watershape Consultant, Expert Witness, International Construction Management 
Contact the author at: info@aquatictechnology.com or 408-776-8220 
"Creating water as art."™ 
Aquatic Technology Pool and Spa© 
©www.aquatictechnology.com 
All rights reserved.

Tuesday, October 22, 2013

Minimum Shotcrete Strengths Pools Watershapes

Shotcrete Strengths for Swimming Pools

The minimum compressive strength for shotcrete (wet mix or dry mix method) shall be 4000 PSI.  The minimum compressive strength of the concrete is fc’=4,000 psi with a maximum water-cementitious material ratio (w/cm) of 0.50.
  
American Concrete Institute
 
The American Concrete Institute’s ACI 318-08 Building Code Requirements for Structural Concrete includes Chapter 4 Durability Requirements. Also contained therein are two applicable tables:
Table 4.2.2 specifies the Requirements for Special Exposure Conditions. 
Table 4.3.1 Requirements for Concrete by Exposure Class defines a Category P1 exposure as concrete “in contact with water where low permeability is required.”   


American Shotcrete Association

The  American Shotcrete Association has also stated that their approved minimum compressive strength shall be 4,000 psi (as stated in the their Position Statement #1).

International Building Code

The IBC also specifies 4000 PSI shotcrete, by making direct reference to the ACI 318 standard.

The IBC (2012) 1910.6 Rebound Removal, also states that all rebound and trimmings shall be removed from the structure.
 
Therefore, all rebound, trimmings and loose debris shall be removed from the structure and shall not be used in any manner within the structure.


Paolo Benedetti, SWD Aquatic Artist, Watershape Consultant, Expert Witness, International Construction Management 
Contact the author at: info@aquatictechnology.com or 408-776-8220
"Creating water as art."™ 
Aquatic Technology Pool and Spa© 
©www.aquatictechnology.com All rights reserved.

Monday, April 1, 2013

Expert Witness Concrete Swimming Pools Watershape Consultant

Wet-mix or dry-mix it's all shotcrete - steel reinforced concrete pools, per the American Concrete Institute (ACI) and American Shotcrete Association (ASA).

Wet-mix vs. Dry-mix

The process of pneumatically applying concrete is called shotcrete.
The differences between the two processes, is the moisture content of the material as it travels through the hose to the nozzle.

Wet-mix shotcrete is delivered pre-mixed with water from a ready mix plant in a cement truck.  Dry-mix shotcrete is blown through the hose dry and water is added at the nozzle.

Though both effectively deliver high strength concrete, the dry-mix process has the potential to deliver stronger psi strengths.  Why?
Less water is utilized to hydrate the cement particles.  Less water equates to greater yield strengths.

Experienced Nozzleman

To achieve a structurally sound shell and high compression strengths, the nozzleman must be experienced.  Not just experienced in holding the hose, but in the application of the material and the science of the process being utilized.

The dry-mix method requires that the nozzleman not add too much water, as this will result in a weaker finished product.

The term is Shotcrete, not Gunite 

Gunite is a company that makes equipment for the dry-mix process.  Like all tissues are not Kleenex, dry-mix shotcrete is not called gunite.
 
Air Lance 

An air lance, also referred to as a blow-pipe, must be utilized during the dry-mix process.  Since the material is drier, the air lance it used to disperse any unsound material from the area where the shotcrete is being placed.  Build up of loose material will result in horizontal stratification voids within the shotcrete.  This loose material is often referred to as rebound, though technically not all of it is actually rebound.

These voids are oftentimes called sand lenses, though they are actually incompetent material that was allowed to accumulate within the wall.  It may be unhydrated cement, sand or aggregate.  Any way you slice it, it is a hollow void that will allow the entrance of water and the eventual corrosion of the reinforcing steel.

Why isn't an air lance always employed, since it is required by the ACI/ASA specifications?  Laziness - the shotcrete crews do not want to employ an additional man to operate the air lance.  It also requires that they have to unroll, clean and roll up an extra hose at the end of the day.

Achieving High PSI Strengths

Either process can yield 7,000 - 9,000 PSI strengths.  It has to do with the mix design, skill of the applicator, supervision of the crew, quantity of mix water and the curing of the finished product.  Per the ACI/ASA standards, the minimum allowable strengths are 4,000 PSI.  Since the ASI 318 and ACI 506 standards are incorporated into the International Building Code (IBC), they ARE THE SHOTCRETE CODES across the United States (except Minnesota, that has yet to adopt the IBC).

Without proper curing of the material, complete hydration of the cement particles will not occur.  The purpose of curing is to keep the water within the concrete, so that the chemical process of hydration can occur.  Keeping moisture in the concrete also helps control the heat that is generated from this process.

Curing can be accomplished through frequent and constant soaking (water curing), covering the shotcrete with a physical barrier (plastic, carpet, burlap, etc.) or the application of a chemical curing compound ( a chemical membrane).  The process utilized is not critical, so long as it is performed per the ACI/ASA standards and the project structural engineers recommendations.

Remember, which ever method is used to cure the structure must also be utilized to cure the test panels.  For example, is not a fair test to apply a chemical curing compound to the structure and then to water cure the samples in a submerged water bath.

Regardless of the shotcrete process employed, high compression strengths are easily achieved when using either process.  It is the skill and knowledge of the applicator and their crew that makes all of the difference.  Nozzleman are certified for either wet-mix or dry-mix processes.  Really competent nozzlemen are certified in both processes.  

Insist that only a ASA Certified Nozzleman operate the nozzle on your project.  
Paolo Benedetti 
Aquatic Artist, Watershape Consultant, Expert Witness 
"Creating water as art."™ 
Aquatic Technology Pool and Spa 
©www.aquatictechnology.com