Epoxy injection of cracks in concrete is like putting a bandaid over skin cancer.... you no longer see it, but it is still there.
It's all great in theory, BUT...
The theory behind epoxy injection of concrete, is to seal cracks and to restore the integrity of the concrete (seal the crack).
Cracks are like people - they come in all shapes and sizes. Unfortunately, tight skinny cracks cannot be effectively sealed.
Fat and wide open cracks are not good candidates for epoxy injection. Why? Because they indicate that there is a substantial structural issue.
Wheels falling off beforee the race even starts
If your brand new pool is full of cracks before it is even plastered - there is a PROBLEM! Do not listen to your pool contractor, something is WRONG.
The bottom line is that swimming pools should not crack. PERIOD. They are designed to hold water. How can they do that when they are full of cracks?
Practical experience tells a different story
Personally,
I have NEVER seen an epoxy injection job that sealed the cracks all of
the way through a shell.
I have cored a number of pools that were
previously epoxy injected, and in none of the cases did the epoxy get
any deeper than an inch or two.
It did absolutely nothing to seal the
cracks on the back of the structure to prevent ground water from
entering the concrete and attacking the reinforcing steel.
The purpose
of complete encapsulation and proper coverage over the steel, is to
protect it from corrosion.
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.
Monday, March 31, 2014
Friday, March 28, 2014
Wine Country Swimming Pool Shotcrete Shrinkage Cracks
I was recently hired by a homeowner in California's Wine Country, to address some shrinkage cracks in their new shotcrete swimming pool.
The term "shotcrete" can refer to either wet or dry mix pneumatically placed concrete.
Possible Causes
1. Thickened shell without additional steel. A single curtain of steel is inadequate in concrete that is 12 inches (or more) thick. There is not enough steel to control shrinkage that naturally occurs when concrete cures. This is why you need a structural engineer to design plans based upon the site's soil conditions.
2. Excess moisture. If the pump operator, ready-mix driver or nozzleman (depending upon wet or dry mix) added too much water, the resulting concrete will not have the proper water/cement (W/C) ratio. Additionally, the structure will be weaker. Remember, in concrete less water is better.
3. Improper curing practices. ACI 318 outlines the acceptable methods of curing concrete (shotcrete included). Physical membrane (plastic), fabric that is kept wet (carpets, burlap, etc), wet curing (keeping wet with soaking or flooding), curing compounds.
Lets face it, carpets and plastic are a hassle. Plastic blows around & what do you do with hundreds of yards of wet carpeting?
Most wet curing is done poorly - the structure is allowed to dry out between the wetting cycles.
Flood curing will ensure that the structure remains wet. But it does not address the horizontal surfaces (tops of beams, cover boxes with drains, etc).
Only using curing compounds will ensure that EVERY SQUARE INCH of the concrete is protected and ensured of a controlled release of the water. And after all, it is the practice specified and employed by most highway transportation departments and the DOT for concrete highways, sidewalks, structures and bridges.
4. Failure to saturate the sub-grade or rock pack prior to the shotcrete placement. The underlying materials will suck water from the shotcrete from the backside. On past projects I've had engineers specify that visqueen be placed on the grade (like is required under slab foundations). This can also provide the structure with some protection from reverse ground water migration.
5. "Bad concrete" - Really, these is no such thing as bad concrete, only poor mix designs. Usually they are incorrect for the project or conditions, excessive transportation or waiting times (from initial mix to placement). Wet concrete experiences "blooms." If it experiences it's second bloom prior to being placed, then you might as well send it back. There are set retarders and additives that can control these times. The mix design can be destroyed simply by the pump operator or truck driver adding more water.
6. Weather conditions - excess heat or high winds can all cause shrinkage cracking by causing rapid evaporation of the water from the concrete surfaces. Again, there are special additives that can be added to ready-mix concrete to assist in combating some of these conditions.
7. A hard freeze - water turns to ice, ice expands, concrete cracks, enough said. ACI 318 has specified parameters for the environmental conditions during and after the placement of concrete. If it's too hot or going to be too cold, you better learn about and employ some protection.
8. Shotcrete installed in horizontal lifts (like layers of a cake), instead of in one thickness from one end of the structure to the other, can result in a compromised shell.
9. The shotcrete company "flashed" the interior of the pool at the end of their job and gave it a pretty broom finish.
What they are really did, was clean out their hoses and hopper by spraying a watered down soupy mix all over the inside of the newly shot pool. The best laid plans are destroyed by this weak and incompetent crust of waste material. Tell them to bring or build a washout bin for this purpose. When doing wet mix shotcrete, some ready mix companies will allow them to washout back into the truck.
10. Incompetent shotcrete placement & finishing techniques. For example: trimmings, rebound and reworked material are placed back into the structure; trimmings and loose materials allowed to accumulate beneath steel; trimmings and rebound allowed to accumulate between layers; improper encapsulation of the steel. Trimmed material from the floor of the spa it thrown by hand into benches, seats and stairs.
11. Poor soil conditions - the pool may be experiencing movement cracks. If the pool was constructed on fill, soil that could not bear the loads or even expansive soils, the pool may be experiencing movement cracks. Add to this, an 18 inch thick structure with a single curtain of steel, and you have a potential problem.
12. Excessive foot and shotcrete hose traffic. This is more commonly seen in dry mix shotcrete (but it can happen in wet mix as well). Excessive foot traffic or the dragging of the hoses around the floor, reworks the concrete. This compromises the initial compaction and placement of the concrete and forces water to the surface. The rapid evaporation of this surface water results in a weakened area of shotcrete.
Any one of these factors can cause shrinkage cracks. Combining a couple of them will surely result in disaster.
Bottom line, there are many possible causes.
Without proper structural engineering, construction specifications (mix designs, special inspections, quality assurance testing), builder supervision, documentation and photographs - there is no means to tell exactly what the cause was.
The only real issue is... the pool builder has an expensive mess on his hands.
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.
The term "shotcrete" can refer to either wet or dry mix pneumatically placed concrete.
Possible Causes
1. Thickened shell without additional steel. A single curtain of steel is inadequate in concrete that is 12 inches (or more) thick. There is not enough steel to control shrinkage that naturally occurs when concrete cures. This is why you need a structural engineer to design plans based upon the site's soil conditions.
2. Excess moisture. If the pump operator, ready-mix driver or nozzleman (depending upon wet or dry mix) added too much water, the resulting concrete will not have the proper water/cement (W/C) ratio. Additionally, the structure will be weaker. Remember, in concrete less water is better.
3. Improper curing practices. ACI 318 outlines the acceptable methods of curing concrete (shotcrete included). Physical membrane (plastic), fabric that is kept wet (carpets, burlap, etc), wet curing (keeping wet with soaking or flooding), curing compounds.
Lets face it, carpets and plastic are a hassle. Plastic blows around & what do you do with hundreds of yards of wet carpeting?
Most wet curing is done poorly - the structure is allowed to dry out between the wetting cycles.
Flood curing will ensure that the structure remains wet. But it does not address the horizontal surfaces (tops of beams, cover boxes with drains, etc).
Only using curing compounds will ensure that EVERY SQUARE INCH of the concrete is protected and ensured of a controlled release of the water. And after all, it is the practice specified and employed by most highway transportation departments and the DOT for concrete highways, sidewalks, structures and bridges.
4. Failure to saturate the sub-grade or rock pack prior to the shotcrete placement. The underlying materials will suck water from the shotcrete from the backside. On past projects I've had engineers specify that visqueen be placed on the grade (like is required under slab foundations). This can also provide the structure with some protection from reverse ground water migration.
5. "Bad concrete" - Really, these is no such thing as bad concrete, only poor mix designs. Usually they are incorrect for the project or conditions, excessive transportation or waiting times (from initial mix to placement). Wet concrete experiences "blooms." If it experiences it's second bloom prior to being placed, then you might as well send it back. There are set retarders and additives that can control these times. The mix design can be destroyed simply by the pump operator or truck driver adding more water.
6. Weather conditions - excess heat or high winds can all cause shrinkage cracking by causing rapid evaporation of the water from the concrete surfaces. Again, there are special additives that can be added to ready-mix concrete to assist in combating some of these conditions.
7. A hard freeze - water turns to ice, ice expands, concrete cracks, enough said. ACI 318 has specified parameters for the environmental conditions during and after the placement of concrete. If it's too hot or going to be too cold, you better learn about and employ some protection.
8. Shotcrete installed in horizontal lifts (like layers of a cake), instead of in one thickness from one end of the structure to the other, can result in a compromised shell.
9. The shotcrete company "flashed" the interior of the pool at the end of their job and gave it a pretty broom finish.
What they are really did, was clean out their hoses and hopper by spraying a watered down soupy mix all over the inside of the newly shot pool. The best laid plans are destroyed by this weak and incompetent crust of waste material. Tell them to bring or build a washout bin for this purpose. When doing wet mix shotcrete, some ready mix companies will allow them to washout back into the truck.
10. Incompetent shotcrete placement & finishing techniques. For example: trimmings, rebound and reworked material are placed back into the structure; trimmings and loose materials allowed to accumulate beneath steel; trimmings and rebound allowed to accumulate between layers; improper encapsulation of the steel. Trimmed material from the floor of the spa it thrown by hand into benches, seats and stairs.
11. Poor soil conditions - the pool may be experiencing movement cracks. If the pool was constructed on fill, soil that could not bear the loads or even expansive soils, the pool may be experiencing movement cracks. Add to this, an 18 inch thick structure with a single curtain of steel, and you have a potential problem.
12. Excessive foot and shotcrete hose traffic. This is more commonly seen in dry mix shotcrete (but it can happen in wet mix as well). Excessive foot traffic or the dragging of the hoses around the floor, reworks the concrete. This compromises the initial compaction and placement of the concrete and forces water to the surface. The rapid evaporation of this surface water results in a weakened area of shotcrete.
Any one of these factors can cause shrinkage cracks. Combining a couple of them will surely result in disaster.
Bottom line, there are many possible causes.
Without proper structural engineering, construction specifications (mix designs, special inspections, quality assurance testing), builder supervision, documentation and photographs - there is no means to tell exactly what the cause was.
The only real issue is... the pool builder has an expensive mess on his hands.
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.
Tuesday, March 25, 2014
Woodside Atherton Swimming Pool Designs
It's Cracking BEFORE it's even finished...
Cracks - everywhere...
Recently a client hired me to inspect a brand new pool that they were in the process fo having built on their estate, on the Woodside - Atherton, CA border.
It seems that the shotcrete that was placed a few weeks ago had developed cracks all over. The pool builder assured them that this was a normal occurrence and that there was nothing to be concerned about.
Many Possible Causes
There were many possible causes.
The gunite company could have used too much water in their mix design. The rapidly evaporating water would have caused shrinkage cracks.
The pool may have been cured improperly, allowing the water in the concrete to depart too rapidly, causing shrinkage cracks.
The gunite could have been mishandled after placement (e.g. walked on), forcing water to the surface. That accelerates the water loss and causes shrinkage cracks.
The gunite crews could have cleaned out their hopper, mixer and hoses by spraying that rubbish all over the inside of the pool & then "broom finishing it."
How bad is it?
After sounding the shell with a "tuning fork," it was determined that there were hollow pockets of concrete.
Only taking core samples of the concrete, directly over some of the cracks, would tell for sure. If the cracks extended through the structure, then someone had a lot of work ahead of them.
That bad
It turned out that the cracks extended through the structure. Since a swimming pool is supposed to be watertight, cracks are unacceptable.
Epoxy injection is equivalent to putting a band aid over skin cancer. It only hides the problem.
The only solution was to demolish the affected areas and to replace the shotcrete.
You would not accept a cracked concrete foundation or bridge... so why would you accept a cracked pool?
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.
Cracks - everywhere...
Recently a client hired me to inspect a brand new pool that they were in the process fo having built on their estate, on the Woodside - Atherton, CA border.
It seems that the shotcrete that was placed a few weeks ago had developed cracks all over. The pool builder assured them that this was a normal occurrence and that there was nothing to be concerned about.
Many Possible Causes
There were many possible causes.
The gunite company could have used too much water in their mix design. The rapidly evaporating water would have caused shrinkage cracks.
The pool may have been cured improperly, allowing the water in the concrete to depart too rapidly, causing shrinkage cracks.
The gunite could have been mishandled after placement (e.g. walked on), forcing water to the surface. That accelerates the water loss and causes shrinkage cracks.
The gunite crews could have cleaned out their hopper, mixer and hoses by spraying that rubbish all over the inside of the pool & then "broom finishing it."
How bad is it?
After sounding the shell with a "tuning fork," it was determined that there were hollow pockets of concrete.
Only taking core samples of the concrete, directly over some of the cracks, would tell for sure. If the cracks extended through the structure, then someone had a lot of work ahead of them.
That bad
It turned out that the cracks extended through the structure. Since a swimming pool is supposed to be watertight, cracks are unacceptable.
Epoxy injection is equivalent to putting a band aid over skin cancer. It only hides the problem.
The only solution was to demolish the affected areas and to replace the shotcrete.
You would not accept a cracked concrete foundation or bridge... so why would you accept a cracked pool?
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.
Monday, March 24, 2014
Sausalito Belvedere Swimming Pool Design Shotcrete Strengths
ACI 318-11 requires that the shotcrete walls on pools be increased in strength and thickness.
For clarification, "Shotcrete" is defined by the ACI as either the wet or dry (incorrectly referred to as "gunite") process of pneumatically placing concrete.
ACI - The American Concrete Institute
ACI is the definitive expert on concrete. So much so, that they publish a myriad of standards that relate to concrete and it's use. The ACI standards are actually adopted by and incorporated into the International Building Code (the building code adopted across the entire United States).
Because ACI Standard 318-11, "Building Code Requirements for Structural Concrete" has been directly incorporated into the International Building Code by the California Building Code. This effectively makes it the law of the land.
ACI 318-11 Changes the Requirements
ACI 318-11 redefined the parameters of the required coverage of concrete required over the reinforcing steel. Prior versions of ACI 318 were ambiguous as to what was actually defined as sulfate or corrosive conditions. It establishes the additional shotcrete protection required when exposed to defined levels of sulfates, water containing chlorides (salts) and permeability.
ACI 318-11, Table 4.2.1 indicates that shotcrete swimming pools are required to meet the criteria for Permeability - P1 (condition defined as: "in contact with water where low permeability is required") AND Corrosion Resistance - C2 (a condition defined as: "concrete exposed to moisture and an external source of chlorides from deicing chemicals, salt, brackish water, seawater, or spray from these sources"). It does not define the PPM level of salt required to create an "external exposure to chlorides."
Those resulting P1 and C2 classifications require specific mix design ratios (ACI 318-11, Table 4.3.1).
ACI 318-11, Table 4.3.1, P1 classification sets a maximum water to cement ratio (w/cm2) of 0.50 and a MINIMUM 28 day compressive strength (f'c) of 4,000 PSI. While the C2 classification establishes a maximum water to cement ratio (w/cm2) of 0.40 and a MINIMUM 28 day compressive strength (f'c) of 5,000 PSI.
Therefore, any swimming pool that is going to be treated with sodium compounds is REQUIRED to have a maximum water to cement ratio (w/cm2) of 0.40 and a designed compressive strength (f'c) of 5,000 PSI. Sodium compounds utilized in swimming pool sanitization include sodium chloride compounds and solutions (chlorine), sodium bromide (bromine) or sodium (salt-electrolysis chlorination). Furthermore, the sodium (salt) levels in pools treated with sodium chloride compounds (chlorine) actually becomes more concentrated over time as the chlorides are consumed.
The C2 classification (Table 4.3.1) further specifies that the requirements of ACI 318-11, 7.7.6 "Corrosive Environments" be met. Section 7.7.6 states that the coverage over reinforcing steel shall not be less than 2 inches for walls and slabs exposed to such corrosive environments.
Structural Engineers & Building Departments often ignore the standards
Many structural engineers and building departments do not abide by the requirements of ACI 318-11. They either attempt to justify design criteria less than the standards, are not versed on the most up to date requirements or simply refuse to comply with the codes.
When there is an issue of structural integrity on a pool, the most recently adopted version of the IBC, CBC or ACI standards will apply in court, whether or not they were followed by the engineer, building department or enforced by the building inspector.
Do you want to be left hanging by a structural engineer who will have to defend his decision to design a structure that was below the requirements of ACI 318-11 and the building codes?
Do you want to take the risk that he will be able to convince a jury of lay people that a weaker and substandard structure was acceptable?
I thought not!
ACI's position is to design to a standard of:
A. A minimum compressive strength (f'c) of 5,000 PSI
B. A maximum water to cement ratio (w/cm2) of 0.40
C. A minimum concrete coverage of 3 inches between the earth and steel
D. A minimum of 2 inches of coverage over the steel (water side).
Therefore, the minimum wall thickness is 3 inches, 2 times the bar diameters (assuming a single curtain of steel bars that cross each other in a grid pattern), plus 2 inches of coverage. For #4 (1/2 inch) bars this would be 3" + 1" + 2" = 6" thick wall.
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.
For clarification, "Shotcrete" is defined by the ACI as either the wet or dry (incorrectly referred to as "gunite") process of pneumatically placing concrete.
ACI - The American Concrete Institute
ACI is the definitive expert on concrete. So much so, that they publish a myriad of standards that relate to concrete and it's use. The ACI standards are actually adopted by and incorporated into the International Building Code (the building code adopted across the entire United States).
Because ACI Standard 318-11, "Building Code Requirements for Structural Concrete" has been directly incorporated into the International Building Code by the California Building Code. This effectively makes it the law of the land.
ACI 318-11 Changes the Requirements
ACI 318-11 redefined the parameters of the required coverage of concrete required over the reinforcing steel. Prior versions of ACI 318 were ambiguous as to what was actually defined as sulfate or corrosive conditions. It establishes the additional shotcrete protection required when exposed to defined levels of sulfates, water containing chlorides (salts) and permeability.
ACI 318-11, Table 4.2.1 indicates that shotcrete swimming pools are required to meet the criteria for Permeability - P1 (condition defined as: "in contact with water where low permeability is required") AND Corrosion Resistance - C2 (a condition defined as: "concrete exposed to moisture and an external source of chlorides from deicing chemicals, salt, brackish water, seawater, or spray from these sources"). It does not define the PPM level of salt required to create an "external exposure to chlorides."
Those resulting P1 and C2 classifications require specific mix design ratios (ACI 318-11, Table 4.3.1).
ACI 318-11, Table 4.3.1, P1 classification sets a maximum water to cement ratio (w/cm2) of 0.50 and a MINIMUM 28 day compressive strength (f'c) of 4,000 PSI. While the C2 classification establishes a maximum water to cement ratio (w/cm2) of 0.40 and a MINIMUM 28 day compressive strength (f'c) of 5,000 PSI.
Therefore, any swimming pool that is going to be treated with sodium compounds is REQUIRED to have a maximum water to cement ratio (w/cm2) of 0.40 and a designed compressive strength (f'c) of 5,000 PSI. Sodium compounds utilized in swimming pool sanitization include sodium chloride compounds and solutions (chlorine), sodium bromide (bromine) or sodium (salt-electrolysis chlorination). Furthermore, the sodium (salt) levels in pools treated with sodium chloride compounds (chlorine) actually becomes more concentrated over time as the chlorides are consumed.
The C2 classification (Table 4.3.1) further specifies that the requirements of ACI 318-11, 7.7.6 "Corrosive Environments" be met. Section 7.7.6 states that the coverage over reinforcing steel shall not be less than 2 inches for walls and slabs exposed to such corrosive environments.
Structural Engineers & Building Departments often ignore the standards
Many structural engineers and building departments do not abide by the requirements of ACI 318-11. They either attempt to justify design criteria less than the standards, are not versed on the most up to date requirements or simply refuse to comply with the codes.
When there is an issue of structural integrity on a pool, the most recently adopted version of the IBC, CBC or ACI standards will apply in court, whether or not they were followed by the engineer, building department or enforced by the building inspector.
Do you want to be left hanging by a structural engineer who will have to defend his decision to design a structure that was below the requirements of ACI 318-11 and the building codes?
Do you want to take the risk that he will be able to convince a jury of lay people that a weaker and substandard structure was acceptable?
I thought not!
ACI's position is to design to a standard of:
A. A minimum compressive strength (f'c) of 5,000 PSI
B. A maximum water to cement ratio (w/cm2) of 0.40
C. A minimum concrete coverage of 3 inches between the earth and steel
D. A minimum of 2 inches of coverage over the steel (water side).
Therefore, the minimum wall thickness is 3 inches, 2 times the bar diameters (assuming a single curtain of steel bars that cross each other in a grid pattern), plus 2 inches of coverage. For #4 (1/2 inch) bars this would be 3" + 1" + 2" = 6" thick wall.
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.
Friday, March 14, 2014
Swimming Pool Construction Design Napa Sonoma California
Are soils reports required by the Napa County Building Department for swimming pool construction permits?
Napa County Memorandum 2013.10.4
The Napa County Memorandum dated October 4, 2013, entitled "When a Geotechnical Report is Required," is ambiguious. In fact it does the citizens of Napa County a disservice.
Quoted below is an excerpt of the memo:
"WHERE REQUIRED
A soils investigation shall be required for all new and replacement structures as well as additions and changes of occupancy within the unicorporated portions of Napa County with the following exceptions:
Exceptions:
...4. Swimming pools which are designed with the assumption of expansive soil."
Expansive Soils - Come in all shapes and sizes
"Expansive soils" is not very descriptive. The expansive index for soils is vast and wide.
Had the above memorandum stated, "soils below 45 PCF," then that would have meant something. It would have placed a quantitative value on the soils that they would not require a report. But, how would you know that value, without a geotechnical report? (back to the chicken v egg quandry).
Simply designing a structure for "mildly expansive soils" (45 PCF) will not be sufficient if a site has "highly expansive soils (120 PCF)."
The question is, "How expansive is expansive?" The truth is, only a geotechnical report will tell you.
Sloping Properties
If the proposed swimming pool is near a slope, then a geotechnical report is required by the State Building Code.
The setbacks and slope stability requirements need to be defined.
So, just because a County Official says it ain't so, does not mean that it "aint so."
Besides, you cannot tell the players (expansive index) without a scorecard (geotechnical report).
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.
Napa County Memorandum 2013.10.4
The Napa County Memorandum dated October 4, 2013, entitled "When a Geotechnical Report is Required," is ambiguious. In fact it does the citizens of Napa County a disservice.
Quoted below is an excerpt of the memo:
"WHERE REQUIRED
A soils investigation shall be required for all new and replacement structures as well as additions and changes of occupancy within the unicorporated portions of Napa County with the following exceptions:
Exceptions:
...4. Swimming pools which are designed with the assumption of expansive soil."
Expansive Soils - Come in all shapes and sizes
"Expansive soils" is not very descriptive. The expansive index for soils is vast and wide.
Had the above memorandum stated, "soils below 45 PCF," then that would have meant something. It would have placed a quantitative value on the soils that they would not require a report. But, how would you know that value, without a geotechnical report? (back to the chicken v egg quandry).
Simply designing a structure for "mildly expansive soils" (45 PCF) will not be sufficient if a site has "highly expansive soils (120 PCF)."
The question is, "How expansive is expansive?" The truth is, only a geotechnical report will tell you.
Sloping Properties
If the proposed swimming pool is near a slope, then a geotechnical report is required by the State Building Code.
The setbacks and slope stability requirements need to be defined.
So, just because a County Official says it ain't so, does not mean that it "aint so."
Besides, you cannot tell the players (expansive index) without a scorecard (geotechnical report).
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.
Monday, March 10, 2014
Cracked glass tile mosaics - Expert
There are a few factors that affect the quality of glass mosaic tiles. Some manufacturers do not have control over their raw materials, while others exercise strict quality control measures.
Cullet
Recycled glass is sorted and ground. The resulting granular material is called cullet. The best quality cullet is utilized for glass lenses and beverage containers.
Lesser qualities of cullet may contain impurities, such as incompatible glass (different colors of glass, pyrex & auto windshields), foreign materials (plastic, paper, metal) or debris (dirt, rocks, contaminates).
Even the Glass Packaging Institute (GPI) says,
"Glass containers for food and beverages are 100% recyclable, but not with other types of glass. Other kinds of glass, like windows, ovenware, Pyrex, crystal, etc. are manufactured through a different process. If these materials are introduced into the glass container manufacturing process, they can cause problems and defective containers."
The slightest bit of impurities can affect the performance of the finished glass tile mosaics. Yet, this lesser quality cullet material is acceptable to many manufacturers. The smallest bit of incompatible glass will wreak havoc on the finished glass tile mosaics.
Glass Recycling - Pass on Inferior Cullet
Manufacturers of glass tiles claim that their raw materials are of the utmost quality. Yet the Glass Packaging Institute states: "Some recycled glass containers are not able to be used in the manufacture of new glass bottles and jars or to make fiberglass. This may be because there is too much contamination or the recycled glass pieces are too small to meet manufacturing specifications.... This recovered glass is then used for non-container glass products. These "secondary" uses for recycled container glass can include tile, filtration, sand blasting, concrete pavements and parking lots."
The glass recycling organizations are saying that contaminated cullet and glass are acceptable to pass onto the glass tile mosaic manufacturers.
Proper Processing
Even when utilizing the highest quality cullet, glass tile manufacturers must ensure that the cullet it thoroughly mixed. Cullet from clear glass will have similar chemical compositions. But the granuales are not exactly the same, as they originated from countless unknown different manufacturers.
To ensure that the finished glass tile mosaics are a homogeneous blend (no pockets of any dissimilar glass), they must follow one of two prescribed processes.
The first acceptable method is to melt the cullet into molten glass. While molten the glass is mixed thoroughly. Statistically this method should work, however, as statistics also prove there are margins of error.
The second method is to melt the cullet and then allow it to cool. The cullet it reground into granules, mixed and remelted. This process has a margin of error so small, that a homogeneous mix is guaranteed.
Guaranteed Performance
While using recycled materials provides warm fuzzies, the liability of installing recycled glass mosaic tiles into an environment where they may be subject to thermal shock is just too great.
Once glass tile mosaics are installed, the manufacturers will blame the installation process for the cracking. The "blame game" starts with finger pointing and the deflection of responsibility.
The cost to remove and replace cracked glass tile mosaics is 5-7 times the cost to install them initially.
Are you willing to put your faith and tens of thousands of dollars of money into a recycled glass product that may or may not perform as it is supposed to?
First Quality Glass
How are first quality glass tile mosaics manufactured? Actually, there are a couple of methods.
The first method is to actually manufacture the glass from the raw materials. This ensures absolute quality control over the chemical composition of the glass mosaic tiles.
The second method is to purchase first quality float glass (panes of glass) from a single manufacturer. The float glass can be used to manufacture fused glass. Or it can be broken into cullet and used to make glass tile mosaics. Because the cullet is from a single source of new glass, the glass tile mosaics are also considered "first quality."
Guaranteed to be free of any contaminates, first quality glass mosaic tiles will ensure a lifetime of trouble free performance.
Why gamble, when there is so much at stake?
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.
Saturday, March 8, 2014
Swimming Pool Low Voltage Lighting
Section
680.23(C) could be changed for the 2014 NEC to permit a special
isolation transformer with a ground shield, similar to the underwater
luminaire transformer, for aboveground low-voltage lighting systems in
proximity to the edge of a swimming pool. Until the change is submitted
and processed, low-voltage lighting must not be located closer than 10
feet horizontally from the edge of the pool or 12 feet above the pool. -
See more at:
http://www.ecmag.com/section/codes-standards/waters-fine#sthash.cDzLMcen.dpuf
Section
680.23(C) could be changed for the 2014 NEC to permit a special
isolation transformer with a ground shield, similar to the underwater
luminaire transformer, for aboveground low-voltage lighting systems in
proximity to the edge of a swimming pool. Until the change is submitted
and processed, low-voltage lighting must not be located closer than 10
feet horizontally from the edge of the pool or 12 feet above the pool. -
See more at:
http://www.ecmag.com/section/codes-standards/waters-fine#sthash.cDzLMcen.dpuf
Low Voltage Lighting is prohibited from being within 10 feet horizontally or 12 feet vertically from the water. Of course, this does not apply to approved underwater low voltage lighting.Prohibited by Building Code
The National Electric Code (NEC) is the building code for the entire United States.
The (2011) NEC 411.4(B) prohibits the installation of low voltage systems within 10 feet of any pool, spa or hot tub, unless specifically permitted by NEC Section 680.
So what IS "permitted" ?
NEC 680.22(C) defines the requirements for low voltage lighting, at any operating voltage, around indoor or outdoor swimming pools.
The only discussion about low voltage lighting around swimming pools is addressed in NEC 680.23(A)(2). It only discusses the underwater light fixtures.
Because these section do not specifically permit the installation of low voltage lighting fixtures adjacent to a swimming pool (as required by NEC 411), it is still prohibited.
Until the NEC is updated or changed, low voltage lighting fixtures are prohibited from being installed within 10 feet horizontally and 12 feet vertically from the water.
Section
680.23(C) could be changed for the 2014 NEC to permit a special
isolation transformer with a ground shield, similar to the underwater
luminaire transformer, for aboveground low-voltage lighting systems in
proximity to the edge of a swimming pool. Until the change is submitted
and processed, low-voltage lighting must not be located closer than 10
feet horizontally from the edge of the pool or 12 feet above the pool. -
See more at:
http://www.ecmag.com/section/codes-standards/waters-fine#sthash.cDzLMcen.dpuf
Section
680.23(C) could be changed for the 2014 NEC to permit a special
isolation transformer with a ground shield, similar to the underwater
luminaire transformer, for aboveground low-voltage lighting systems in
proximity to the edge of a swimming pool. Until the change is submitted
and processed, low-voltage lighting must not be located closer than 10
feet horizontally from the edge of the pool or 12 feet above the pool. -
See more at:
http://www.ecmag.com/section/codes-standards/waters-fine#sthash.cDzLMcen.dpuf
Section
680.23(C) could be changed for the 2014 NEC to permit a special
isolation transformer with a ground shield, similar to the underwater
luminaire transformer, for aboveground low-voltage lighting systems in
proximity to the edge of a swimming pool. Until the change is submitted
and processed, low-voltage lighting must not be located closer than 10
feet horizontally from the edge of the pool or 12 feet above the pool. -
See more at:
http://www.ecmag.com/section/codes-standards/waters-fine#sthash.cDzLMcen.dpuf
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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