GOVT. ENGG. COLLEGE, BIKANER

A PRESENTATION ONCONCEPTS OF SHOTCRETE TECHNOLOGY

Submitted by:- Under the guidance of:- Akshay Kumar Mr. Adil Qureshi13EEBCE002

INTRODUCTION

• This innovative technology of shotcrete was introduced to make the work easier and immediate.

• Shotcreting has proved to be the best method for construction of curved surfaces .

• Domes are now much easier to construct with the advent of with this shotcrete technology.

• Tunnel linings are also becoming easy technology.

DEFINITION OF SHOTCRETE

• Shotcrete is a mortar or high performance concrete conveyed through a hose and pneumatically projected at high velocity onto a backing surface.

• Applied mixture of cement, aggregate, and water conveyed through a hose and projected at high velocity onto the application surface.

• It is the force of this spraying action that leads to compaction of the concrete or mortar which then forms layers of concrete to the required thickness.

• Shotcreting has been an acceptable way of placing cementitious material in a variety of applications.

• This mechanism reduces the rebound waste that occurs through the shotcreting process and these fibers also resist plastic shrinkage and cracking through their ability to enhance the early stage tensile strength of concrete.

CLASSIFICATION OF SHOTCRETE

• Classified based on two processes, namely1. Dry process 2. Wet process

• Dry mix shotcrete: Step1:Dry shotcrete components, which may be slightly pre

dampened to reduce dust, are fed into a hopper with continuous agitation.

Step2: Compressed air is introduced through rotating barrel or feed bowl to convey the materials in a continuous stream through the delivery hose . water is added to the mix at the nozzle.

Step3:Then the material is consolidated on receiving surface by high impact velocity.

Simplified sketch of a typical dry mix shotcrete system

Advantages of Dry process

• Water content can be adjusted instantaneously by nozzle man.

• More effective placement in overhead and vertical applications.

• Useful in repair applications.• Control of materials is on site.• Widely used in mining.

Wet mix shotcrete

Step1:Shotcrete components and water are mixed(usually in a truck mounted mixer) before delivery into a positive displacement pumping unit.

Step 2: which then delivers the mix hydraulically to the nozzle where air is added to project the material onto the rock surface.

Step 3: Mostly wet-process shotcreting is done with premixed mortar or small aggregate concrete.

Typical type of wet mix shotcrete machine

Advantages of Wet process

• It produces less rebound, waste and dust compared to dry mix procedure.

• Larger volume can be placed at less time.• Cost effective method for placing concrete.• Ideal for irregular surface applications• Allows for easier material handling in areas with

difficult access.

QUALITY CONTROL

The quality of the final shotcrete product is closely related to the application procedures used.

These procedures include: • Surface preparation• Nozzling technique• lighting, ventilation, communications, and crew

training

APPLICATIONS OF SHOTCRETE

• Highway and railroad tunnels• Mining operations• Slope stabilization• Building foundations• Concrete repair & restoration• Parking garages• Housing

Construction of tunnels

Slope stabilization

• Infrastructure réhabilitation Bridges, parking structures, subway tunnels etc.

ADVANTAGES

• Little or no framework is required.

• Cost effective method for placing concrete.

• Ideal for irregular surfaces application.

• Allows for easier material handling in areas with difficult access.

• Easy start up, shutdown and clean up.

• An increase in load bearing capacity due to redistribution of stresses.

• Excellent corrosion resistance.

DISADVANTAGES• Rain may wash out the cement leaving a sandy surface, or it may

saturate the shotcrete and cause sloughing or sagging

• Strong wind will separate the material between the nozzle and the point of deposit, reducing the strength.

• It requires skilled and experienced labours.

• A greater degree of geotechnical knowledge is required.

• Improperly applied shotcrete may create conditions much worse than the untreated condition.

THANK YOU