Shotcrete is ideal for early ground support after blasting or excavating in mining, providing early strength development. Putzmeister’s mobile shotcrete equipment applies concrete in mines and tunnels all over the world, with concrete output rates of up to 30m³/h and spraying reaches of up to 17m. The common denominator of all Putzmeister machinery is its high performance and reliability in rough working conditions above and under ground.

Putzmeisters most advanced model for concrete spraying in mining is the Sika-PM 4210, a further development of the well-known Sika-PM 4207. The first machine of this new series has been allocated to the German Sachtleben Bergbau, who owns and runs the Clara mine (Grube Clara) in Oberwolfach, situated in the Black Forest of Baden-Württemberg, Germany.

In accordance with highest technical standards, this mining operation has been continuously extracting barium sulphate for more than 100 years, as well as fluorspar for more than 25 years. The sulfates are further processed into high-quality products at the near-by preparation plant. The annual output of raw material amounts to approximately 140,000t, resulting in a salable production of 50,000t of barite and 25,000t of concentrated fluorite.

The Sika-PM 4210 concrete spraying equipment will be used in all of the three main fissures of the mine for structural support in roadway heading as well as special operations in critical situations. According to Sachtleben, the greatest challenges which the machine will be facing are the frequently changing geological conditions of the rock, varying significantly in composition, strength and stability. Therefore, the machine operator needs to be flexible during the shotcreting process as far as concrete output and additive dosage are concerned, depending on the early-strength and drying times requirements of each specific situation.

The new proportional remote-control of the Sika-PM 4210 responds exactly to this customers’ need, as it allows the complete regulation of the concrete output as well as fine adjustments of the preset additive dosage. All other functions of the machine are also available via remote-control, including the automatic start of the spraying sequence (air, concrete and additive).

In addition to this, the reach of the spraying arm has been increased by 1.4m in comparison with the standard model, achieving a maximum vertical spraying reach of 10.5m. Besides, the spraying arm is more agile, with an increase of 25% in the spraying speed at the tip of the arm. The cylinders of all arm extensions are covered for protection, but nevertheless easily accessible for maintenance. Furthermore, new high intensity xenon working lights have been incorporated into the spraying arm.

Other improvements of the Sika-PM 4210 responding to the rough working conditions at the Clara mine are:

  • The incorporation of state of the art heavy duty axles with mining tires
  • A manually released automatic fire extinguishing system which comes into action at six critical spots of the machine at once
  • A heavy duty switchboard made of stainless steel
  • A special low profile concrete hopper with a discharging height of only 1,150mm
  • A strong stainless steel additive tank with a capacity of 450l