066-820-16-99 Shotcreting (concrete spraying) of bridges in Brovary and Obukhov using shotcrete mixture. When performing shotcreting, Torkret mixture was used.
Shotcreting makes it possible not only to restore working characteristics, but also to adapt buildings to the changing natural and technogenic conditions. Our experience and experience gained by foreign companies working in the field of shotcreting attest show that shotcreting has unlimited possibilities as far as its application for general engineering, repair and restoration works is concerned.
Shotcreting, or torkreting (from Latin tectorium – “plaster” + concretus – “compacted”), is formation of a layer of concrete or other building materials (plaster, clay) on the surface of concrete or reinforced concrete structures. Mortar (shotcrete) is applied under compressed air pressure, as a result of which action the cement particles interact with the structure’s surface filling the cracks, cavities and even the smallest pores. As far as its physical nature is concerned, shotcreting is a method of superficial reinforcement of various structures.
The material obtained as a result of shotcreting is called Torkretbeton..
The basic equipment for shotcreting is the shotcreting plant consisting of a shotcrete gun or concrete blower and an air compressor. The shotcrete gun ejects mortar at the speed of 80 to 100 m/s. The air pressure is 150 to 350 kPa. Thickness of the layer obtained in a single shotcreting cycle is 10 to 15 mm.
Shotcreating enables us to obtain exceptionally robust surface which is characterized by increased density – in fact, it becomes a monolithic structure. Buildings constructed with the use of shortcreting technique effectively withstand the impact of aggressive environment; they are water- and frost-resistant.
Although shotcreting becomes a staple technique in the field of construction, it is constantly developing. Lots of new recipes of shotcrete are developed to provide optimal solutions for every specific technological task. Most frequently a cement-sand mixture (in 1:2 to 1:6 proportion) is used as shotcrete. Particle size of the filler is 8 mm. Grade of cement: not lower than 400.
Technical advantages of shotcreting
• Protective concrete layer which is only several centimeters thick, having:
– High mechanical strength (28 days – 40 to 60 MPa);
– Density of 2.4 kg/dm3;
– Frost-resistance of not less than 300;
– Water-resistance of not less than B12;
– High adhesion to surface.
• Physical and mechanical properties of concrete are improved:
– прочность на изгиб на 40% больше;
– Bending strength is 40% higher;
– Compression strength is 15% higher;
– Modulus of rupture is 5% higher;
– Shrinkage is 30% lower.
Economic advantages of shotcreting
• High production capacity.
• Low cost of protection and restoration of concrete as compared to substitution of failed concrete structures.
There exist two main shotcreting methods: dry and wet ones..