Shotcrete

As one of the Front Range’s most respected shotcrete contractors, we have the experience necessary to successfully use shotcrete for a wide variety of applications. Whether you’re interested in basement construction, retaining wall construction, soil nailing, slope paving, retaining wall repair or any structural repair or just architectural walls — our skilled team has the ability to easily execute complex shapes, building structures that not only look great but are built to stand the test of time. Keep reading to learn more about our shotcrete services available in the greater Denver area.

What is Shotcrete?

Shotcrete is pneumatically applied concrete and can be used for many different applications in commercial and residential projects. Shotcrete makes it possible to apply concrete to irregularly shaped surfaces or hard to reach areas that may otherwise make construction difficult and requires a minimum amount of form work compared to cast-in-place concrete.

Why Shotcrete?

Shotcrete offers many advantages over traditional cast-in-place (CIP) concrete and has many applications.

Basement subfloor construction

  • Shotcrete uses earth as the back form and therefore the additional excavation required for form work on the outside of wall is eliminated.
  • Only edge formwork is required to cap the top or ends of wall.
  • If temporary excavation support is required, the shoring system can be designed as a permanent shoring system which reduces the required wall thickness of the planned structure.

Site wall construction

  • Site walls, or retaining walls are used to maximize the buildable footprint of a lot. There are two types of retaining walls, ‘cut walls’ or walls constructed as material is excavated  in ‘top-down’ fashion, and ‘fill walls’ or walls constructed as fill is placed from the bottom upward.  Top-down ‘cut walls’ commonly use shotcrete. 

Slope paving

  • Shotcrete is requires no formwork and is ideal for slope paving to protect erosional features or to construct drainage features.

Retaining wall repair

  • Regardless of the construction material type, retaining walls can easily be repaired utilizing shotcrete.

Structural repair

  • Seismic retrofits (augmenting strength of existing structures to withstand earthquakes)
  • Structural repair of concrete that has deteriorated

Shotcrete Application and Finishes

Shotcrete is pneumatically applied concrete which is typically applied onto a vertical or overhead surface. First conceived in the early 20th century, shotcrete has evolved into an essential facet of the construction landscape, due in large part to its versatility and ease of application.

Shotcrete is often used in conjunction with drilled soil nails to build retaining walls or temporarily shore an excavated face.

Shotcrete is uniquely suited for this application, it is as strong as traditional concrete, can be applied without the use of forms, and it is applied as a liquid, so it takes the shape of whatever it is applied to.

Shotcrete does not require forms to place, in fact, shotcrete can be manipulated and molded into nearly any shape imaginable. Wet application of shotcrete is achieved by pumping concrete through a hose and applying air at the nozzle. The air propels the shotcrete onto a vertical or overhead surface and a team of finishers will smooth the face or sculpt it into whatever shape necessary. Defining the type of finish required for your project is a serious concern, as this can have far reaching design and cost implications. Below are some examples of shotcrete finishes as they relate to soil nail walls.

Pneumatic Gun Finish

The picture above shows a soil nail and shotcrete wall in a shoring application with a pneumatic finish. Pneumatic finishes are mainly used on temporary shoring applications, or any other application that has relaxed aesthetic requirements. While effort is made to apply shotcrete evenly, no controls are in place to ensure uniform application. This is the most cost-effective option as little to no finishing is required and no control needs to be established before applying the shotcrete.

Screed Finish

screed finish

Shotcrete with screed finish can have a similar look to a traditional cast in place wall. Shotcrete is applied to a thickness between 6” – 12” for permanent applications, and as little as 4” for temporary shotcrete applications. Wireline controls are used to ensure shotcrete thickness is uniform along the entire length of the wall.

Soil nails are not visible in this picture. Permanent application of shotcrete will typically encapsulate the nail in shotcrete to prevent the nail from corroding or otherwise degrading over time.

Sculpted Shotcrete

sculpted Finish

Sometimes referred to as architectural shotcrete, sculpted shotcrete can be made to take on the characteristics of surrounding geology. Again, soil nails are used to retain the slope, then shotcrete is applied. Instead of working the surface into a flat, continuous plane, sculpted shotcrete is shaped to resemble rock outcrops and cliff faces. Great care is taken to sculpt the wall in a way that would be present in nature. Thought is put into each line before it is carved. Texture and color are applied afterwards. The result is nearly indiscernible from a natural geological feature.

Choosing the right shotcrete finish can have far reaching implications for a project’s aesthetic as well as its budget. GeoCraft Builders has the experience necessary to help choose the right one.

Shotcrete FAQ’s

Shotcrete is increasingly utilized in below grade structural applications and also is utilized in structural repair. The following addresses a number of common questions about the application and use of Shotcrete.

What is Shotcrete ?

Shotcrete is made of the same components as concrete- aggregate, cement and water, although the proportions are slightly different.  The difference is in the method of application.  Shotcrete is simply pneumatically applied concrete.  A concrete pump delivers the concrete mix through a hose to the end where air, delivered from a large air compressor, is injected forcing the concrete to exit the hose end throught a nozzle at high velocity.

Why is Shotcrete used?

The most common way to place concrete is referred to as  the “Cast-In-Place” or CIP method. Wood forms are erected to frame the concrete shape to be constructed.  The concrete is poured into place directly from a ready-mix concrete truck.

Shotcrete only requires forming one side onto which the concrete is sprayed into place. Shotcrete is commonly used in below grade wall construction because the face of the excavation can be utilized as the backside form for the shotcrete –eliminating the required formwork that Cast-in-Place concrete requires, which is why more than a third of the shotcrete market is below grade structural and underground tunnel construction.  

Just about any aesthetic can be achieved with shotcrete from the traditional flat, trowel finish look of Cast-In-Place concrete to a stamped and stained face of dimension stone or masonry block or even sculpted and stained as natural bedrock outcrop.  PIC or cross-reference other blogs?

Is Shotcrete stronger than concrete?

Shotcrete must be pumpable and have adhesion to stick when applied on vertical and even overhead surfaces.   To achieve this, shotcrete has a greater cement content than a traditional CIP mix.   A typical shotcrete mix will have 6 to 8 sacks of cement per cubic yard of mixed product, compared to a CIP mix which is about 5 sacks of cement per cubic yard.  Shotcrete is stronger and achieves strength much more quickly than CIP concrete.  Successful shotcrete application depends upon the skill of the person at the end of the nozzle (termed nozzleman).  The American Concrete Institute (ACI) publishes guidelines for shotcrete nozzleman and can be found here: https://www.concrete.org/Portals/0/Files/PDF/Previews/506R_16_preview.pdf.

Is Gunnite the same as Shotcrete?

Gunnite and shotcrete are similar, in that they are both pneumatically applied, but the similarity ends there.  Gunnite is ‘dry mixed’, meaning that the cementitious material and aggregate is delivered to the nozzle under air pressure where water is then injected before existing the nozzle.  Shotcrete is supplied as a ‘wet mix’ in a ready-mix concrete truck.  The shotcrete ingredients, cement, aggregate and water are premixed at the ready-mix plant.  The ‘wet mix’ is delivered to the nozzle from a concrete pump and high pressure air from an air compressor is injected into the nozzle, forcing the concrete out the nozzle at high velocity. 

Contact GeoCraft Builders Today

Our team has the resources and technical knowledge needed to install shotcrete safely and effectively. Interested in learning more about the benefits of working with shotcrete for your next concrete project? We are here to help answer any questions you may have and are happy to provide preconstruction service during the design phase of your project to ensure the economy shotcrete offers is fully realized.






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