Page 51

2014FallShotcreteEMag

Nozzleman Knowledge Fig. 1: Missing auger cannot provide adequate cylinder Fig. 2: Uneven flow (slugging) has displaced in-place filling. Uneven nozzle flow will affect nozzle placement shotcrete. Note signs of sagging below the wire quality reinforcement place material; and cause sagging, sloughing, and sure without altering the mixture. Because high voids within the work. If irregular flow occurs, pressure is required to convey the mixture through the nozzleman should stop placement, investigate the delivery system, wear items within the pump the cause, and correct before continuing. or placement system that leak will allow moisture Regardless of the pumping equipment used, to be squeezed from the mixture and lost. Poor the pump must be calibrated to operate within a seal quality can lead to dry-pack placement line smooth and manageable range. Nozzlemen should blockages, segregation, buildup within the con- choose a flow rate that feels right. Skilled noz- crete pump valves, and placement difficulties. zlemen always work within a speed range so that Skilled nozzlemen should be capable of identi- nozzle thrust does not interfere with the ability to fying excessively worn components and schedule accurately direct the flow. repairs or replacement before excess wear affects Wear items within the pump (cutting rings, placement quality or safety (Fig. 3). wear plates, seating surfaces, and outlet seals) will affect placement quality if excessive wear Nozzles Require Constant has compromised seal integrity. Because wet-mix shotcrete is a combination of cementitious mate- Maintenance rials, aggregates, and water, the pump must be It is the nozzleman’s responsibility to operate able to convey material to the nozzle under pres- and correctly maintain the shotcrete nozzle. But Fig. 3(a): Worn wear components Fig. 3(b): Wear components in Fig. 3(c): Hardened buildup restriction inside the will allow moisture to be squeezed good condition S tube is caused by worn wear components from the mixture during pumping Shotcrete • Fall 2014 49


2014FallShotcreteEMag
To see the actual publication please follow the link above