Shotcrete is an alternative form of concrete very similar to gunite in both the method of application as well as in its versatility in terms of the many functions it can perform. Our regular readers may recall our coverage of gunite. In this article, we will be discussing the benefits and usages of shotcrete.
We at BS Power are industry specialists when it comes to the business of property construction, and we are particularly involved in the retail of concrete mixers and adjacent products. For this reason, we thought you the audience might be interested in our take on this incredibly popular non-traditional type of cement.
What Makes Shotcrete Different?
Traditional cement is typically poured into a mould of whichever shape you need to create. Shotcrete, on the other hand, is concrete that is pneumatically propelled at high velocity onto surfaces to create structures. This is done using a hose controlled by a trained nozzleman. An easy way to think of it is by comparing it as the concrete equivalent of a 3-D printing pen.
This form of concrete laying, much like gunite, is a more effective method of constructing contoured and curved structures such as swimming pools.
Shotcrete mixture is also very effective at quickly adhering to surfaces. Furthermore, the high velocity at which it is applied through the hose allows for the compaction of the concrete. This makes the use of shotcrete a favoured option among construction workers having to apply concrete to vertical surfaces such as walls and slopes and even overhead surfaces like tunnels.
It is important to note, however, that shotcrete is not that different from traditional concrete in terms of composition. The term “shotcrete” refers mainly to the pneumatically powered and nozzle-fed mechanism through which concrete is applied.
The cement you use to create shotcrete can be wet, dry, or anywhere in between. Construction workers merely have to decide upon the most appropriate mix for the task at hand. With the right mix, nozzlemen can then spray out the shotcrete onto a surface, adjusting the direction, spread, and velocity of the spray to form the desired structure.
What Is Shotcrete Useful For?
The several key benefits of shotcrete include design freedom and quick adhesiveness through compaction as aforementioned prior. This makes it the preferred option of concrete in many construction jobs that would otherwise be arduous if pouring cement was used instead.
To give you a scope of how versatile shotcrete is, we will provide you with a list of just a few of its many benefits:
Shotcrete’s popularity among contractors and homeowners alike cannot be understated. Over the past three decades, shotcrete has become one of the most popular materials used in the installation of swimming pools.
From backyards to luxury hotels, shotcrete is used frequently to produce some of the world’s most marvellous swimming pools. Shotcrete pools remain structurally sound much longer than those designed using other materials. Shotcrete pools are known to increase the market value of properties for this reason.
Advantageous application method
The mechanism of compaction which occurs as shotcrete is applied will actually make the structure stronger. Shotcrete structures are essentially made of layers and layers of concrete compacted at high velocities to form dense and strong objects.
Compaction also assists in the adhesion of shotcrete as it is applied to a surface. This allows it to be applied vertically and even completely upside-down on overhead structures.
Shotcrete is also a useful tool in terms of design freedom, as previously mentioned. You are able to articulate nearly any sort of structure with shotcrete, especially when it comes to the installation of pools.
Mix and match
It is even possible for construction workers to put additional materials into shotcrete concrete mixers to alter the mix and protect it from specific environmental hazards that structures might undergo in certain areas and regions.
Much of why shotcrete is so popular in construction has to do with the fact that we can curate the mixture’s qualities and the way in which it is applied to such a specified degree. This degree of control allows workers to apply the perfect sort of concrete for any job.
Certain additives can be poured into a mixture of shotcrete to make it more aqua-phobic. This makes shotcrete perfect for the construction of water-storing structures such as artificial dams and swimming pools.
Other materials can be added to also provide the mix with more structural rigidity when it sets. The ratio of water to cement can also be altered to tailor the adhesiveness and setting time of the concrete.
Fewer moulds and formwork
When concrete is poured, the surface it is being applied to needs some sort of boundary or barrier to accommodate for the concrete’s internal pressure. Without a mould, it is completely infeasible for a poured concrete structure to form or retain its desired shape whilst drying out.
Shotcrete is compacted onto any surface it is sprayed on and its mixture can be altered in the concrete mixers to make it set and harden much faster. Thus, less formwork is required to create shotcrete structures. Pre-existing structures can also be reinforced with shotcrete without the need for formwork at all thanks to its compaction upon making contact with a surface.
Using shotcrete as opposed to regular poured cement allows contractors and homeowners alike to save on two very important resources: money and time. Construction crews working with shotcrete are typically smaller staffed. This is because a shotcrete job requires fewer hands-on deck to complete. This makes the work less labour intensive and thus more affordable.
Construction companies can also increase their contract turnover rate when working with shotcrete. For good reason, projects such as swimming pools, tunnels, and ditches are easier to complete with shotcrete. Companies are thus able to take on more projects at a time and accept new projects faster when working with shotcrete.
How Is Shotcrete Applied?
Shotcrete is applied through a process referred to as guniting. The name comes from gunite, a concrete mix that is also applied using a pneumatically powered hose. The only real difference between the two is that shotcrete can leave the concrete mixers and enter the hopper as either a wet or dry mix.
Shotcrete is first mixed then put inside the hopper. The hopper will serve as the reservoir used to feed the hose as the shotcrete is applied. The hopper will feed the hose as pressurised air is used to propel the shotcrete from the nozzle.
This nozzle should have a valve attached to it that determines the amount of water being added to the concrete mix. This allows constructors to alter the mix as necessary on the job. It also leads to greater versatility since the water ratio can be adjusted to suit different jobs without the need for additional equipment.
It is possible to create shotcrete structures with a 70 MPA yield by creating a shotcrete mix with a 1 – 3 ratio of cement to sand. Getting this yield, however, requires the job to be done by a trained professional.
In many regions of the United States of America, contractors are required to have ACI certification as a shotcrete nozzleman in order to perform this job. As per the conventions of the construction industry, ACI certification makes the shotcrete nozzleman position a specialised job.
In addition to an experienced nozzleman, shotcrete installation teams will also need well-trained pump operators as well as a crew of shapers to smooth out the surfaces of shotcrete as it is being applied.
The Structure of a Shotcrete Gunning Crew
A full shotcrete gunning crew ideally consists of five specialised workers: the nozzleman, blowpipe operator, foreman, mixer operator, and the gunman. The task also requires several additional labourers for the mixing process, the constructing and tearing down of scaffolding, and the moving of the hose.
The nozzleman should have over six months of preliminary training and experience in similar roles. His job is to apply the shotcrete from the business end of the hose. A professional nozzleman will be able to monitor and maintain the flow of shotcrete, ensuring a uniform pressure as the shotcrete is applied.
They should also make sure that proper compaction is occurring during the application process. In terms of gear, they are in charge of monitoring the effectiveness and condition of the nozzle. They must inspect the water jets to make sure they are not clogged and need to check for inconsistencies in the hose connections.
The foreman is typically the most physically hands-off member in a shotcrete construction project. He is, however, primarily in charge of the coordination and overall facilitation of the job. His job is to direct the efforts of the crew and to ensure that every other member is performing their role appropriately.
According to industry standard guidelines, the foreman of a shotcrete project should have roughly two years of work as a nozzleman under their belt. To supplement this knowledge, they must also have experience in and knowledge of the other roles as well.
The gunman is responsible for the steady and uninterrupted supply of shotcrete from the concrete mixers to the nozzle. This involves regular maintenance on the gun before and after jobs and preventing the mix from pulsating during application.
The gunman is also in charge of detailing requirements to the mixer operator. After the hose is no longer in use, it is the gunman’s duty to perform maintenance and cleaning by removing residual substances.
It is their job to ensure that the concrete mixers are clean and operable before and after shotcrete projects. A key role of the mixer operator is to apply materials and compounds to the mix in the exact proportions specified for a particular job.
This is the nozzleman’s right-hand man; they lend assistance to the nozzleman with a valve-fitted blowpipe which they use to remove rebounding particles from the work’s surface and in other hard-to-access spots.
They should make sure that the area surrounding the spray’s location is cleared of rebound. Their job also involves the trowelling of shotcrete where and when necessary. Additionally, it is the blowpipe operator’s duty to keep an eye out for issues such as blockages and leaks.
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Shotcrete is an impressive innovation in the world of concrete. For more information about concrete and its various applications in construction, feel free to browse the many other topics explored in our blog section.
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