What is shotcreting in civil engineering?

Shotcrete is a method of applying concrete or mortar pneumatically projected or sprayed with the help of nozzle having high velocity on the prepared surface. Shotcrete is also called Gunite or sprayed concrete. It is typically reinforced by steel, rods, steel mesh or fibres.

What is rebound in shotcrete?

Rebound is the part of the shotcrete that does not adhere to the surface during application, causing some material to ricochet. The loss of material and subsequent clean-up can slow down work on site while increasing costs, so it´s important to minimize it.

What is wet mix shotcrete?

Wet-mix shotcrete is a mixture of cement, aggregates, and water that may contain admixtures, which is hydraulically pumped to the nozzle where compressed air is added to provide high velocity for placement and consolidation of the material on the receiving surface.

What is sprayed concrete called?

Gunite and shotcrete are two trade terms for different types of sprayed concrete. Sprayed concrete was developed as a construction solution for tunnels, underground structures, slope stabilization, structural repairs, and swimming pools.

What is shotcreting explain dry mix process of shotcreting?

The dry mix method involves placing the dry ingredients into a hopper and then conveying them pneumatically through a hose to the nozzle. The nozzleman controls the addition of water at the nozzle. The water and the dry mixture is not completely mixed, but is completed as the mixture hits the receiving surface.

What is the application of shotcreting how it is done?

A shotcrete wall is constructed by using a special mix of high-strength concrete, which is sprayed at high velocity on the wall using compressed air, to form a retaining structure, drain, or wall. shotcrete walls provide a permanent and cost-effective solution for retaining wall construction.

How do you stop rebound in shotcrete?

Viscosity Modifying Effect – to increase thickness of the shotcrete, reduce the amount of layers needed and reducing rebound. Shear-Thinning Effect – improve the pumpability and flow of the shotcrete. Reduction of bleeding, sedimentation and segregation – improve the shotcrete mix leading to easier spraying.

What is the difference between wet and dry mix shotcrete?

Wet process is defined by the ACI as “shotcrete in which all of the ingredients, including water, are mixed before introduction into the delivery hose and compressed air is introduced to the material flow at the nozzle.” In other words, dry process involves blowing powder through a hose and adding water at the nozzle.

What is better shotcrete or gunite?

Gunite generally lasts longer and maintains a higher quality than shotcrete. For instance, gunite tends to dry faster than shotcrete, leading to a much smoother surface and avoiding significant cracks from shrinking. Gunite can also withstand up to 9500 psi, a much higher psi than shotcrete.

Why is it called gunite?

For gunite, water is added to the dry concrete mix at the gun-shaped nozzle opening (hence the name “gunite”). The concrete is made in the air right before hitting its target. Shotcrete is different in that it is trucked to your property wet in a cement truck.

What is involved in the shotcrete process?

Most facets of the shotcrete process are covered, including application procedures, equipment requirements, and responsibilities of the shotcrete crew. Other aspects, such as preconstruction trials, craftsman qualification tests, materials tests, and finished shotcrete acceptance tests, are also discussed.

Why shotcrete a good choice?

Why Shotcrete a. Importance of proper application. Properly applied shotcrete is a structurally sound and durable construction material which exhibits excellent bonding characteristics to existing concrete, rock, steel, and many other materials.

What should be included in a shotcrete item?

Alignment control, joints, and protection of adjacent surfaces are usually included in the shotcrete item. The method of measurement should be specified to eliminate any ambiguities as to the items included or excluded from the method for payment.

What is gunite shotcrete?

Shotcrete, gunite, or sprayed concrete is concrete or mortar that is conveyed through a hose and is pneumatically projected at high velocity on the surface. Shotcrete is a mixture of cement, aggregates, and water that is usually reinforced by conventional steel rods, steel mesh, or fiber.