6 Common Myths About Shotcrete

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6 Common Myths About Shotcrete

Shotcrete concrete is a relatively new introduction in the field of concrete services. This article clears a few common myths associated with shotcrete services

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The shotcrete method is a relatively new way employed in construction, especially in Edmonton and its neighborhood. While it has surely taken over the conventional cast-in-place method of concrete construction, there are various aspects of shotcrete that you may still be unsure about.

With so many myths floating around you, it is only natural that you feel apprehensive about hiring a shotcrete company for your latest home refurbishing requirements.

This article pinpoints some of the most common myths you might have heard about shotcrete along with the facts to clear out your mind once and for all.

Myth

It is alright for the shotcrete to be shot rough as it is going to be covered by a final layer of plaster anyways.

Fact

In reality, your shotcrete contractor must be careful in finishing the shotcrete layer in uniformity. There will indeed be a final plaster layer deposited on top, but the shotcrete layer must be a watertight layer of symmetrical thickness.

You should keep in mind that the plaster layer that acts as finishing will have mechanical properties that differ from shotcrete’s. It is due to this reason that a uniform shotcrete layer without any gaps or cracks would ensure that there are no weak areas within the final concrete structure.

Myth

As shotcrete is meant to be mechanically shot via a nozzle, it is not necessary to be shot physically.

Fact

The shotcrete method of concrete construction simply uses high velocities to deposit concrete. The benefit of depositing it at such a high velocity mechanically is that it gives the shotcrete consolidation and compaction properties that are much more superior to conventionally placed concrete.

Also Read: Some Common Applications Of The Shotcrete Method?

However, If the concrete becomes too stiff and un-pumpable via a nozzle when it arrives at your construction site, then the shotcrete contractor might deposit it by hand. While this may be unavoidable in some circumstances, it will, however, be not as effective as pneumatically pumped concrete.

Physically deposited concrete will result in a structure with less overall strength, as it is more prone to have gaps.

Myth

Because shotcrete is technically dry-mix, it lacks the optimum freezing and thawing resilience.

Fact

As opposed to common belief, shotcrete has immense freezing and thawing capability. It can perform surprisingly well in climates that account for repeated freezing and thawing conditions.

Air entraining accounts for the exceptional strength that shotcrete has to offer in freezing and thawing environments. Like all concrete, shotcrete is also dependent on adequate air void spacing for the best performance of entrained air.

Furthermore, two core factors for freezing and thawing resistance are strength and permeability. As shotcrete has a decreased water-cementitious material ratio, it has a higher strength, which aids in its ability to withstand repeated freezing and thawing conditions.

However, shotcrete has a reduced permeability due to the use of supplementary cementitious materials like fly ash and silica fume.

Myth

Dampening the shotcrete surface periodically is sufficient for curing.

Fact

Occasionally dampening the shotcrete surface for curing does not serve the purpose of curing very efficiently. For adequate curing, you must keep the shotcrete surface damp continuously for a minimum of seven days at least.

Curing your shotcrete sufficiently has the advantage of preventing moisture loss from the concrete. It also provides supplemental moisture to the cement if required. Ultimately it is the hydration of the concrete that provides the structure with unbreakable strength. Therefore, paying attention to the proper curing of your shotcrete surface is crucial.

Myth

Being dry-mix in nature, shotcrete is more porous compared to wet-mix variants and is therefore not suitable for liquid-containing structures such as concrete swimming pools, etc.

Fact

The porous nature of shotcrete can be countered by being conscious of a few specifications. If your professional shotcrete contractor uses high-quality materials and a good mixture design, the porosity of your shotcrete structure should not be a problem.

Also, the right equipment and professionally trained nozzlemen have a vital role to play in the overall durability of the shotcrete structure. The nozzleman is particularly crucial when it comes to shotcrete porosity. As shotcrete is dry-mix, its water content is entirely dependent on the nozzleman.

A mindful and trained expert will introduce the right amount of water to the shotcrete and hence maintain an optimum porosity for your finished shotcrete structure without any restrictions for liquid-containing structures.

Myth

It makes no difference to leave overspray and rebound material within the shotcrete structure, as everything is touched up with a final coat of shotcrete in the end.

Fact

Leaving overspray and rebound material within your shotcrete structure can result in an eminently weaker overall assembly. The aggregate material that bounces off on impact when shotcrete is shot is termed a rebound.

As this is mostly sand and rock, it is therefore much weaker than concrete. With weaker sections of overspray and rebound material in your structure, it will be more vulnerable to getting cracked over time and having less resistance against extreme weather conditions.

Final Thoughts

Shotcrete has replaced the conventional cast-in-place concrete method in most construction nowadays. With more and more professional shotcrete contractors emerging in the market, it is becoming the norm to use shotcrete in place of conventional concrete.

The dry-mix shotcrete variant has some prominent advantages over the cast-in-place concrete. But because the method is relatively new, it has a plethora of myths and misconceptions attached to it. Gaining clarity about the basics of the shotcrete method will help you make the best choices when it comes to shotcrete services.