Cast-In-Place Concrete Vs. Shotcrete: What's The Difference?
Wednesday, March 13, 2019
Today, the pool shell of a commercial swimming pool can be constructed in several ways. Two of the most commonly used methods are cast in place concrete and shotcrete. The major difference between the two is quite simply the method of placement. At the end of the day, both systems, with proper design and construction, will provide a rock solid pool shell which can last for more than 40 years.
Cast in place concrete construction can be a costly and very labour intensive process. This type of construction requires additional excavation to allow workers room to install an extensive forming system for both the inside and outside of the pool walls, which is used to contain the concrete and shape the pool structure. This working room behind the forming system requires backfilling when the concrete work is complete.
Once the formwork is in place, concrete is discharged from a ready-mix truck, and transferred to the work area by way of boom pump, line pump, buggy, or down the chute directly off the back of the truck. Next, concrete is placed on the ground or in the form work, and then must be vibrated for consolidation & compaction.
Cast in place concrete forming system.
Pouring cast in place concrete.
It’s the most common type of concrete construction.
Cast-in-place concrete will result in a strong and waterproof structure with compressive strengths of 4,000 to 5,000 psi.
When properly designed and constructed, cast in place concrete results in a relatively smooth surface that will require very little surface preparation for the use of epoxy-based pool paint, tile and plaster finishes.
Cast-in-place concrete results in the most uniform surfaces possible.
Over excavation is required to allow working area behind the forming system.
Very labour intensive to form the walls.
Backfilling of the formed walls is required.
It’s harder and much more complicated to form shapes.
Generally more expensive to construct in comparison to a shotcrete pool.
The quality of a shotcrete pool can be comparable to a cast in place pool with one exception. Typically, they do not require extensive forming which often results in cost and time savings. Although the hardened properties of shotcrete are similar to conventional cast-in-place concrete, the nature of the placement process provides additional benefits, such as very fast erection, particularly on complex forms and shapes, including curved walls. Due to the speed of construction and the minimal equipment requirements, shotcrete is a very cost effective building method.
The shotcrete method utilizes concrete that is discharged from a ready-mix truck into a shotcrete pump and then pneumatically “shot” in place against a wood or earth form. To increase the velocity of the material which improves the control of the “shooting” process, accelerators and other admixtures can be added to the nozzle along with air under pressure. Because shotcrete is "shot" up against wood forms or earth, there is generally very little backfilling required.
Pool form ready for shotcrete.
Shotcrete being "shot" into place.
No over excavation required. As a result there is very little to no backfilling required.
The ability to build in very tight spaces and “free form” applications make it very simple to build pools of any shape.
Higher compressive strengths than cast-in-place concrete. Typical compressive strengths of shotcrete are in the 6,000 to 7,500 psi range
Lower construction costs.
There are fewer trained and skilled in the use of shotcrete than that of cast-in-place concrete.
The finished surface of shotcrete is rougher than a finished surface of a cast-in-place concrete pool. Additional surface preparation is required before the application of epoxy paint. As a result most shotcrete pools have a plaster finish.
Comparing James Bond to Pool Bonding may be farfetched, and when thinking about pools, these words would be near the bottom of the list of safety features people may think of. But, like a secret double agent, Pool Bonding acts like an invisible body guard, keeping unsuspecting swimmers safe from the hidden, evil Electrical Shock! And like any good super hero, a trusty side kick is needed, and that’s where “Grounding” comes in. Together, Bonding and Grounding form an invincible super duo, and act as one of the most important aspects to a safe swimming environment when designing and constructing a pool system, secretly keeping the people of the pool safe from the insidious dangers of Electrical Shock.
As mentioned, every Super Hero needs a side kick, and when guarding from harmful electrical currents, this case is no different. “Bonding” and Grounding” each have their own jobs, and each are needed to keep the pool area safe.
BONDING. POOL BONDING.
Bonding’s super power is an important one. It joins all electrical pool components and metal components within five feet of the pool together to a thick copper wire, whether it's a mechanical item such as a recirculation pump, simple deck items such as a grab rail or stanchion post, or even unseen items like reinforcing rod encased within the pools concrete walls, forming a safety loop. This safety loop ensures all items have the same voltage, eliminating the possibility of voltages being transferred from the pool to a swimmer, instead containing them within the safety loop, and directing them back to a panel. If needed, a breaker on the panel will trip, dissipating the harmful current within the loop.
GROUNDING, THE TRUSTY SIDEKICK
Grounding, the trusty, yet just as important sidekick, is also silently keeping the patrons of the pool safe, day after day. Grounding power acts in conjunction with Bonding, using the safety loop created by the bonding process, and adds a connection to the ground. This ground connection ensures that any harmful current within the loop is directed away from the swimmers and into the ground, where it dissipates and disappears harmlessly.
A POWERFUL SUPER DUO
Bonding and Grounding, when properly implemented into the design and construction of a pools system, will continue to act in conjunction with one another, forming one of the most powerful safety duo’s within the pools natatorium, keeping the evil Electrical Shock at bay. Next time you're in a pool, enjoying your swim, listen closely. If you hear a faint tune, it may just be the theme song to the undefeatable super duo of Bonding and Grounding, quietly and courageously continuing the never ending fight with Electrical Shock, keeping the people of the pool safe for years to come!
* This is a guest blog post written by Lee Battams, President of Aqua Plans Aquatic Consultants Inc. The knowledge and experience Lee displays on routine site visits have ensured his clients, including Acapulco Pools, remain confident in his abilities in aquatic design.
There are a lot of considerations when selecting a swimming pool contractor to build your pool. Whether the project is a high-end residential project or a multimillion dollar waterpark, it is important to be very diligent in selecting the builder to avoid delays, cost overruns, improper construction and lots of headaches. But what things should be considered?
WHAT DOES THEIR SAFETY RECORD LOOK LIKE?
The safety record of a company should be a primary consideration. A company with a poor safety record attracts a lot of attention (not the kind they want) and can really bog down a project. In fact, a project can be put on hold for an extended period if there are glaring safety infractions or heaven forbid a serious injury or fatality on the job site. Ask the proponent for a copy of their Health and Safety Policy, and safety record. If they don’t have one, or are unwilling to provide information, move on.
PRICE ISN'T EVERYTHING
Price, while always an important consideration is not everything. We frequently hear our clients say “…I wish we had gone with the more reputable builder. This job has become a nightmare…” The saying “you get what you pay for” could not be truer. If the price seems too good to be true, it is. There is no such thing as an extraordinary $7 bottle of wine, and there is no such thing as an inexpensive Bugatti car. The two things are mutually exclusive. The Bugatti and a K-car will both take you to the store, but the Bugatti will take you to the store for decades (and look really good doing it!), and there is no comparing the quality of the two. The same is true in pools. You can choose a method and a builder that may appear to save you a little coin but suffer endless change orders and additions to the project. Or you can spend that little extra bit of money to hire a thorough and reputable builder and have peace of mind for years to come.
DO THEY HAVE A STRONG FOUNDATION?
Like a strong building, a strong company needs a strong foundation. In the construction business, this foundation is in the form of knowledge that is both deep and wide, and can only be acquired from years of experience specific to the industry. A newer business just doesn’t have the history to be as knowledgeable as a well-established company that has been around for a long time. In the experienced company, there are senior people and younger members of the team. There is a combination of high energy and drive and a deep well of information that was developed over decades of practice. The thing about knowledge is that it is often applicable to a wide variety of applications that help experienced builders provide the best outcome for the client. Hydraulic concepts in pools and water management for example, are often applicable to electricity where Voltage equates to Feet of Head and current flow to velocity. Companies who have a deeper knowledge in their art have a broader understanding of the many things they may encounter in performing their work. Look for contractors who have a broad range of experience over a long period of time, senior people who have “been around the block” a couple of times and young energetic and well educated project people.
DO THEY HAVE INTERNAL SYSTEMS IN PLACE?
It is a great thing to have knowledge, but if it is held by a few individuals it often fails to crystalize in the positive outcome of your project. Good companies develop internal systems that reflect the Best Practices that have been developed out of the knowledge gained from experience. It is these companies who seek to establish a culture of quality and caring expressed in writing the form of standard operating procedures. Ask your potential contractor if they have internal systems in place to support quality assurance, delivery, and value added designs, longevity of the product, and so on. A company with systems is a company that cares about what they do, and who they do it for. Also ask if the company has a Mission Statement. The Mission Statement is the guiding philosophy of the company. A company without a mission is like a pilot without a map. Yes, the plane is flying…but the destination is dicey.
WHAT IS THEIR EXPERIENCE LEVEL?
The Record of Experience speaks volumes about the knowledge base of the company. Obviously, the more pools a company has built, the more experience they have. But it is also important to look at the different types of pools that a company has built. Not all pool builders build all pools, and sometimes for good reason. For example, Company ABC may be an advocate for cast-in-place pools through their limited knowledge and experience; they know how to build them, but nothing else. Concrete pools are really good and are considered the gold standard in the industry, however, there are times when another type of pool is more appropriate than a concrete pool. If the pool is going on the top floor of a high rise, weight may be a limiting parameter. It is important to find a builder who has the experience to recognize and understand your options and what best suits your needs. Ask your potential builders for their list of projects (current and complete) and also for a list of references. If the record of experience is small or limited in scope, you may want to look a little deeper into the company. If the reference list seems small compared to the record of experience, it should raise a red flag! A good contractor doesn’t maintain a specific reference list…every single client should be a reference.
DO THEY USE THEIR OWN FORCES?
If the builder you are looking at using has a lot of subcontractors, it may be worth looking a little further. Dividing the scope into different trade subcontracts (mechanical subs, waterproofing, tile, concrete etc.) dilutes and displaces responsibility of the trades and of the general contractor. When something goes wrong, it’s nobody’s fault, and it’s everyone’s fault. A great deal of time is spent trying to figure out if the waterproofing contractor caused the leak, or if the tile contractor damaged the waterproofing. Or maybe the concrete contractor is at fault. It is best to source a contractor who self-performs the entire pool scope with their own forces from the excavation, to mechanical and electrical work, to tile setting and commissioning and training. When there is only one company performing the entire scope for the work, there is no opportunity to cast blame for problems to others. You only have one phone call to make.
ARE THEY FINANCIALLY STABLE?
The financial stability of the company is also an important consideration. Are they able to completely bond a large project? Often tender documents ensure that this is the case, but private projects may overlook the need. What happens if things go wrong, or the contractor walks off the job or goes bankrupt? Who will finish the job? Who will pay for the work? Also, you want to be sure that the company you select is going to be around tomorrow and for years to come. Of course, there is never a guaranty but the best predictor of the future, is a record of the past. If the company has been building great pools for decades, they are likely to be around for a long time to come.
DO THEY HAVE A SERVICE DEPARTMENT?
Once the pool is built, you are away to the races. But what if something goes wrong with the pool after a few years? Who will close the pool for winter? It is always best of the company you choose to build the pool also has a service department who can deal with any problems and to perform regular maintenance. The service department of the company who built the pool is best equipped to service the pool since they will have an intimate knowledge of the pool from the construction phase. There are many “pool builders” out there who actually have no idea how to best operate a pool, and have no service department. It is best to steer clear of these builders. Once the project is complete, you never see them again.
CAN THEY PERFORM?
Finally, schedule can be critical, especially for commercial projects. Liquidated damages can cripple a business that was counting on opening the pool in December, but it didn’t happen until the following May. There has been more than a few projects abandoned or sold for pennies on the dollar as poor performing contractors drove the owner into insolvency. No builder is perfect or immune to making mistakes…things happen. What sets the premium builder apart from others is how they react to the problems. The only way to know how different builders react is to speak with their past clients. Don’t accept a short list of “preferred references”. It is a lot of work to fully research your builder, but it will pay dividends many times over in the long run.
A well-constructed pool delivered on time and on budget will provide decades of enjoyment, or in the case of a commercial project, revenue generation. The best start to this positive outcome is to balance all of these considerations discussed, and make a good decision.
Every year people die by electrocution, and some of these incidents are associated with pools. In fact, In September 2016, a young girl working as a lifeguard at a swimming pool in North Carolina lost her life when she was electrocuted as she entered the water. So let’s talk a little bit about this, and how we might reduce the risk of electrical injury associated with pools.
Electrical energy acts a lot like other sources of energy in that it moves (flows) from one area to another when there is a “potential difference” in the voltage of those areas. Like a waterfall plummeting from a high point to a low point, so does electricity from a higher voltage (a live wire or battery terminal for example) to a lower voltage (ground).
Electricity generally speaking, needs a “conductor” to move or "flow" through. This flow of electricity is expressed in terms of Amperes or Amps. Some things are better conductors than others. Copper, aluminum and gold are excellent conductors and pass electricity, while things like the human body are less apt as conductors, but can certainly still pass electricity. Other substances like some (but not all) polymers and glass are insulators. Still others are classified as semiconductors (like doped / contaminated silicon). Uncontaminated water is actually an insulator when pure (distilled), but becomes sort of a semiconductor most of the time. In pools, it is usually a pretty fair conductor having been “contaminated” with minerals, chlorine and sometimes salt. The human body is a mediocre conductor, but also a poor insulator. Being that we are largely made up of contaminated water, electricity from a source will pass through our bodies on the way to ground…the lower voltage. On the way through it can interfere with nerve impulses including those activating the heart, and cause damage, seizure or in the worst case death by cardiac arrest.
So how can we make the seemingly unsuitable bed partners of pools and electricity less…shocking?
BONDING AND GROUNDING
Bonding refers to bringing all of the conductors around the pool (the reinforcing steel, handrails, light fixtures, pump cases etc.) to the same electrical potential by connecting them all together with a conductor (a ground wire). This eliminates the possibility of any potential difference between these various items; whatever voltage one item is at, the same voltage will be seen at all of the other items. But bonding alone does not render the items safe. You can’t get a shock between one item and another, but what if a stray voltage is energizing the bonding wire to some higher voltage? Then any of the items could give you a shock if your body is grounded (for example, being barefoot on the deck). To ensure the items are a zero volts, the bonded items have to be grounded. This simply involves running a wire from the bonded loop to the ground lug in the distribution panel.
KEEP ELECTRICAL ITEMS AWAY FROM THE POOL
It is never a good idea to have an electrically powered item near a swimming pool. Things like radios, blenders (for those summer margaritas) if dropped into the pool, can electrically charge the water and potentially shock bathers. Even if the device is away from the pool on the deck somewhere, someone who has recently been in the pool could drip water into the device and create a conductive path with the water from the device, through them to ground…not fun!
USE GFCI DEVICES AND BREAKERS
Ground Fault Circuit Interrupting (GFCI) devices work by comparing the current flow in the hot (supply) wire to the current flow in the neutral (return to ground) wire. In any circuit, the current flow should be the same in both ‘legs’. If it isn’t, it means the current is going somewhere else - like through you! The GFCI device will trip to disconnect the power supply if there is a difference of 6mA (that’s 6/1000 Amps), and does so in a fraction of a second to protect us from being shocked. GFCI devices are a great way to protect people from any electrical device, but are particularly appropriate for things like underwater pool lights where electricity is so close to the water.
PERFORM REGULAR ELECTRICAL REVIEWS
It’s a fact of life on this planet of ours that things change, materials degrade, corrode, erode, oxidize and just plain wear out. Your electrical system is no exception. Electrical distribution boxes and the breakers within become corroded and fail. Plastic wire insulation dries out and cracks, ground points become corroded. Corrosion is exacerbated by exposure to salt water because of its electrolytic properties. Having a reputable electrical contractor visit the site periodically may flag some of these issues before they become a health and safety concern. In addition to a visual inspection, they can perform tests (like high voltage meggering) to assess the condition of various electrical insulators in the system.
Salt Water Chlorination: Is it the Right Option for your Facility?
Wednesday, March 14, 2018
Salt or no salt? That is the question! Or at least one of the most common questions being asked by pool owners and operators these days. Every pool owner has their own set of reasons for wanting salt or not wanting salt. There are many questions regarding the mechanical equipment at the facility, finishes of the pool, uses of the pool, local bylaws, (just to name a few) that must be answered before jumping to any decisions. Additionally, the owner must be aware of the many myths regarding salt water systems and chlorine systems alike before making any decisions. They must also understand that a salt water pool doesn’t mean you will be swimming in ocean water! Windows to the Universe team states that salt water pools typically have 3,000 to 6,000 ppm, while the ocean is about 35,000 ppm.
When changing a liquid chlorine sanitized pool over to a salt water system, or when building a pool destined to be salt water, the mechanical systems must be selected properly. Everything from the pumps, filters and heaters must be designed and approved for use in a salt water pool. If this is not done, manufacturers will not honour warranties, and there will be damaged equipment much prior to their normal lifetime.
The finishes of the pool need to be considered when contemplating a salt water pool as certain finishes do not last as long under salt water conditions. Liners, tile and plaster finishes all have their own issues when it comes to salt, so owners must investigate each option thoroughly and ensure whichever option is chosen is installed properly. As with any sanitation system, monitoring and proper balancing is also very crucial in the lifetime of the finishes.
Fixtures such as hand rails, underwater lighting fixtures, and rope anchors need to be properly chosen when going with a salt water pool as they will corrode faster without being constructed of proper materials and properly maintained. The image above shows a hand rail in a salt water pool that is rusting due to the salt. Think of what salt use on our roads does to our vehicles and infrastructure during the winter months. The same type of damage will happen to a pool that doesn’t have all of its components designed for salt water use.
Primary uses of the pool under consideration for salt water should also be considered. A pool that is primarily for lap and competition swimming where there is high swimmer volume and high exertion may want to shy away from a salt system, as it will require much more monitoring of the chlorine levels to ensure they are in accepted ranges. Yes I said chlorine. Salt water pools still have chlorine in them. They use a chlorine generator system involving a process called electrolysis to produce its own chlorine, rather than adding liquid chlorine directly to the water. A therapy pool with low patron turnover may be a better candidate for salt water, as it will be easier to keep the pool balanced and may increase user comfort.
Local bylaws are another very important item to look into when considering salt water in your pool. Especially for commercial pools, salt is typically not permitted to be the primary source of sanitation. Most municipalities still require salt water pools to have a secondary sanitation system installed, typically liquid or tablet chlorination. Furthermore, when draining the pool, salt (and chlorine) levels usually must be brought down to low levels in order to legally be dumped into the municipal sewage treatment system. Always check local bylaws for your stipulations prior to draining your pool.
Pool owners need to ensure that they do as much homework on salt water chlorination as necessary to ensure that they have made an informed decision. There are too many cases of owners not taking all of the necessary steps required to properly operate a salt water pool, and have a seemingly endless repair bill. As with any large expenditure, always ensure you are working with qualified pool designers and builders when constructing a new pool or doing a renovation, no matter what sanitation system you are going with.
When planning the construction or renovation of your pool, whether commercial or residential, one of the many decisions you will need to make is the pool finish. There are several options available to both commercial and residential pools, there are also many factors to consider when choosing a finish. Cost is usually the first thing on everyone’s mind, when making any purchase. However, there are many other considerations that will often times outweigh the initial cost. The intended use of the pool is an important factor to consider when determining the finish of a pool. Residential pools, which have a lower use, can get away with one of the more budget-friendly options, as there is less wear and tear. A low-cost finish will save some money upfront however, repairs and refinishing will be required much sooner than some of the longer lasting, high-end finishes.
Tile has been used as a pool finish for years and is known to be the most durable finish. When applied correctly, a tiled finish can last for decades before requiring any replacement. Tile offers the pool owner a wide variety of colour options and design possibilities. Due to the preparation and labour required for installation, this high quality finish option comes at a higher initial cost. However, over time it will pay for itself, through the savings on repairs and replacements.
Durability & Longevity: A tiled finish will last decades if applied correctly, and compensate for the higher upfront costs.
Easy to Repair: If there is an issue with isolated delamination of tile, it is very easy to replace small areas of tile and match to the existing, without having to re-finish the entire pool.
High Upfront Cost: Correctly installing tile, comes with heavy labour including; the preparation of the subsurface, laying the tile and grouting the tile.
Deterioration of Grout: Though tile has a very long life span, the grout will deteriorate much quicker. Over time grout will begin to wear out of the joints and discolour. Normally, grout will be required to be replaced much sooner than the tile.
Plaster is one of the most prominent pool finishes around, and has been used for several years; a quicker install than products like tile is the main reason for its popularity. Plaster is shot onto the pool walls, similar to gunite, and then toweled to give it a smooth consistent finish. A plaster finish does require some sort of tile border at the waterline as the waves against the plaster will cause it to deteriorate quickly.
Cost & Durability: Even with the high level of durability a plaster finish offers, the cost is relatively low.
Aesthetically Pleasing: Plaster provides a very nice finish which is smooth and able to form to any shape or design.
Pool chemistry can very quickly deteriorate a plaster finish if not properly maintained; low pH in the water is a big concern and requires experienced supervision.
With age, pool plaster will start to delaminate and cause sections of the plaster to pop off, having to re-plaster a pool is very costly.
Painting a pool is a very inexpensive method of finishing any pool, and is typically used in a commercial application for community or public pools. Though painting a pool is an economical and quick finish option, over several years the paint will chip and need to be repainted. A parge coat is required before painting to ensure all honeycombing of the concrete is filled, leaving the floor and walls smooth.
Low Cost & Project Schedule: The cost of the material and labour required to complete the work is extremely low and can be completed quickly.
Low Risk of Damage: Since paint is applied to a cementations backing, there are no concerns about damaging or puncturing the finish from items in the pool.
Frequency of Repairs: A paint finish will need to be refinished every 3 to 5 years, requiring the existing paint to be blasted off before repainting.
Imprefections: If the subsurface of the pool is not done perfectly any imperfections such as honeycombing or rough parging will show through and can cause injuries to swimmers.
VINYL LINER FINISH
Traditionally Vinyl liners have been a typical residential pool finish, due to the relatively low cost and quick installation. Liners can and have been used for commercial applications however, due to the low durability of a liner it is not very common. Vinyl liners can be used in both stainless steel and concrete pools.
Low Cost: In comparison to other finishes, liners can be an economical alternative. The liner itself is relatively inexpensive, in comparison, and installation labour is a significantly lower cost.
Creates a Water Tight Tank: This benefit can be an efficient solution, saving time and money, to a deteriorating concrete pool, which has started to leak.
Deterioration: Vinyl liners are more susceptible to deterioration caused by harmful UV light and poor water chemistry, resulting in the liner needing to be replaced sooner.
Easy to Damage: Vinyl liners can very easily be damaged from foreign objects, such as tree branches or toys falling into the pool. Punctures in the liner will result in water getting behind the liner, causing the pool to leak and the liner to bubble out.