4
One half-day and one full-day session were designed
to equip the participants with sufficient theoretical back-
ground and understanding within classroom and open-
discussion situations. The first half-day session focused on
refreshing basic concrete/shotcrete terminology, area prepa-
ration, and machine preparation (Figures 4a and 4b). The
second half-day session discussed the roles of admixtures,
accelerator dosage calculation based on the technical data
specification, and spraying application technique and the
impact of the lousy spraying application (Figure 4c).
Finally, the last half was to visit the concrete labora-
tory, batch plant, and field assessment to perform hands-
on practice and evaluation. Open discussion sessions and
written evaluation tests were performed at the end of each
classroom session to evaluate the trainer and participants.
The field support and observation commenced daily to
at least two nozzlemen whether they passed both tests. It is
essential to keep track of all the key nozzlemen and their
rotational shift schedule. This will help further optimize
the continuous operation and support the non-nozzlemen,
such as supervisors/helpers, in improving and providing
constructive feedback on the nozzle’s skills development.
Four aspects of assessment were evaluated: area preparation,
machine/equipment, concrete/material, and spraying tech-
nique. All of these aspects have several standard checklists
as follows:
1. Area preparation:
– Floor/working surface: wet/flooded ground pro-
motes safety hazards to the personnel.
– Ventilation: to ensure good airflow for personnel
and running equipment.
– Mesh condition: regarding campaign shotcrete,
avoid curled mesh that prevents shotcrete from
adhering better to the previous layer.
– Surface washing: to ensure the surface is clean and
free of loose particles, dust, and debris, providing
better adhesion for the shotcrete. Surfaces must
always be damp before sprayed.
2. Equipment:
– Shotcrete pump condition: if there is any hardened
residue that limits its capacity.
– Accelerator pump and dosing: display is readable,
and dosage is controllable with proper calibration.
– Lighting: sufficient to see the surface.
– Safety: emergency kit availability
– Transfer pipe: if any hardened residue limits capac-
ity, it is sometimes clogged and needs immediate
troubleshooting.
– Nozzle condition: pointing correctly to the surface
and not leaking.
– Positioning: good strategic placement of the
machine in a safe working area, on a stable surface,
and no work should start before the hydraulic out-
riggers are firmly placed.
– Form oil: lubricant is sprayed before the machine
operates to avoid shotcrete material buildup at the
end of the shift.
3. Concrete/material
– Slump: to attain proper workability regarding
material flow from the hopper to the sprayer noz-
zle. The nozzleman/helper should never add water
to the mix to correct the slump.
– Fiber: typically causes issues if not mixed thor-
oughly, creating fiber balls, which often delay the
spraying due to clogging.
– Workability issues such as segregation/bleeding
4. Spraying technique:
Figure 4. (a) Quality control for concrete and shotcrete class, (b) hands-on slump testing as part of concrete workability
assurance, and (c) classroom-based presentation and discussion to cover admixture, dosage calculation, and spraying technique
One half-day and one full-day session were designed
to equip the participants with sufficient theoretical back-
ground and understanding within classroom and open-
discussion situations. The first half-day session focused on
refreshing basic concrete/shotcrete terminology, area prepa-
ration, and machine preparation (Figures 4a and 4b). The
second half-day session discussed the roles of admixtures,
accelerator dosage calculation based on the technical data
specification, and spraying application technique and the
impact of the lousy spraying application (Figure 4c).
Finally, the last half was to visit the concrete labora-
tory, batch plant, and field assessment to perform hands-
on practice and evaluation. Open discussion sessions and
written evaluation tests were performed at the end of each
classroom session to evaluate the trainer and participants.
The field support and observation commenced daily to
at least two nozzlemen whether they passed both tests. It is
essential to keep track of all the key nozzlemen and their
rotational shift schedule. This will help further optimize
the continuous operation and support the non-nozzlemen,
such as supervisors/helpers, in improving and providing
constructive feedback on the nozzle’s skills development.
Four aspects of assessment were evaluated: area preparation,
machine/equipment, concrete/material, and spraying tech-
nique. All of these aspects have several standard checklists
as follows:
1. Area preparation:
– Floor/working surface: wet/flooded ground pro-
motes safety hazards to the personnel.
– Ventilation: to ensure good airflow for personnel
and running equipment.
– Mesh condition: regarding campaign shotcrete,
avoid curled mesh that prevents shotcrete from
adhering better to the previous layer.
– Surface washing: to ensure the surface is clean and
free of loose particles, dust, and debris, providing
better adhesion for the shotcrete. Surfaces must
always be damp before sprayed.
2. Equipment:
– Shotcrete pump condition: if there is any hardened
residue that limits its capacity.
– Accelerator pump and dosing: display is readable,
and dosage is controllable with proper calibration.
– Lighting: sufficient to see the surface.
– Safety: emergency kit availability
– Transfer pipe: if any hardened residue limits capac-
ity, it is sometimes clogged and needs immediate
troubleshooting.
– Nozzle condition: pointing correctly to the surface
and not leaking.
– Positioning: good strategic placement of the
machine in a safe working area, on a stable surface,
and no work should start before the hydraulic out-
riggers are firmly placed.
– Form oil: lubricant is sprayed before the machine
operates to avoid shotcrete material buildup at the
end of the shift.
3. Concrete/material
– Slump: to attain proper workability regarding
material flow from the hopper to the sprayer noz-
zle. The nozzleman/helper should never add water
to the mix to correct the slump.
– Fiber: typically causes issues if not mixed thor-
oughly, creating fiber balls, which often delay the
spraying due to clogging.
– Workability issues such as segregation/bleeding
4. Spraying technique:
Figure 4. (a) Quality control for concrete and shotcrete class, (b) hands-on slump testing as part of concrete workability
assurance, and (c) classroom-based presentation and discussion to cover admixture, dosage calculation, and spraying technique