Concrete Kibble Safe Work Method Statement

A loaded concrete kibble weighing up to 5 tonnes creates a massive struck-by hazard throughout its lift cycle from ground loading through to elevated placement and return. Workers can be struck during ground-level loading operations when the kibble swings due to wind or crane movements, during the lift when the kibble passes through intermediate floors with workers present, at the placement level when positioning the kibble for concrete discharge, and during emergency situations requiring rapid kibble movement. The kibble has significant momentum even at slow speeds, and contact causes severe crush injuries or fatalities. Wind loading on the large surface area of a loaded kibble can cause substantial swing, making the load difficult to control even with tag lines. Exclusion zones under lifted loads are legally required but often poorly enforced in the time-pressured environment of concrete placement, with workers entering exclusion zones to perform other tasks or prepare subsequent work areas. Communication breakdowns between the crane operator who cannot always see the placement area, the dogman managing the lift, and concreters receiving the load contribute to incidents, particularly when visual line-of-sight is obstructed and radio systems are relied upon exclusively.

Consequence: Fatality or permanent disability from crush injuries, multiple workers affected simultaneously if kibble strikes scaffold or edge protection systems causing secondary collapse

Concrete kibble discharge gates must contain up to 5 tonnes of wet concrete during lifting and allow controlled release at the placement location. Gate mechanisms are subject to extreme forces from concrete weight and impact loads, with failure causing catastrophic uncontrolled discharge. Gate failures occur due to worn latching mechanisms, concrete buildup preventing proper gate closure, impact damage from previous operations, corrosion of hinge pins and latches, and inadequate maintenance or inspection regimes. The consequences of gate failure during lifting are severe, with falling concrete striking workers below, the sudden weight change causing crane instability or boom movement, and concrete discharge potentially affecting structural elements below that are not designed to receive concrete loads. Emergency gate release mechanisms required for overfilling situations must be designed as deliberate actions rather than accidental triggers, as inadvertent emergency release during lifting has caused fatalities. The high-alkaline nature of concrete accelerates corrosion of gate mechanisms, particularly in marine environments or during winter when de-icing salts are present on construction sites. Concrete buildup on gate sealing surfaces is almost inevitable during operations and must be systematically removed to maintain gate integrity, yet time pressures during concrete pours often result in cursory cleaning that allows buildup to compromise gate function over multiple lift cycles.

Consequence: Fatality from falling concrete striking workers, crane instability from sudden load change, structural damage from concrete discharge onto incomplete structural elements

Calculating total lifted load during concrete kibble operations requires accounting for kibble tare weight (typically 500-800kg), concrete weight (2.4 tonnes per cubic metre), and lifting equipment including chains, shackles, and spreader bars. Concrete density varies with mix design, aggregate type, and admixture content, making visual estimation unreliable. Overloading occurs when kibble capacity is exceeded during filling, concrete density is higher than assumed in lift planning, wet concrete accumulates in kibble from previous loads adding to total weight, or multiple lifts are performed without checking crane load monitoring systems. Tower cranes have load capacity that varies with radius and boom angle, meaning a lift that is within capacity at one radius may exceed capacity when the load is slewed to a different position. Crane load moment indicators provide warnings but can be ignored in time-pressured situations, or may be inaccurate if not regularly calibrated. The practice of "topping up" kibbles to minimize lift cycles creates risk of overloading, particularly when concrete truck capacities vary and batching tolerances allow concrete load variation. Crane operators may not have direct visibility of kibble loading and must rely on communication from ground personnel who may not appreciate the safety criticality of accurate load information. Dynamic loading during kibble pickup and travel adds 10-25% to static load, further reducing available crane capacity margins.

Consequence: Crane structural failure or boom collapse causing multiple fatalities, suspended load drop causing fatalities below, crane overturn affecting site buildings or public areas

Concrete placement from kibbles typically occurs at slab edges or elevated formwork locations where fall protection systems must be installed and maintained while accommodating kibble positioning and concrete discharge operations. Workers lean over slab edges or through barriers to guide kibbles, operate discharge gates, direct concrete flow with shovels and rakes, resulting in compromised fall protection. Edge protection barriers may be temporarily removed to allow kibble positioning, creating unprotected edges during active concrete operations when multiple workers are present and attention is focused on kibble management rather than fall hazards. The dynamic environment during concrete placement with moving suspended loads, workers moving around placement areas, concrete discharge creating vision obscurity, and time pressure to complete concrete placement before initial set all contribute to fall risk. Individual fall arrest systems using harnesses and lanyards are often specified but present practical challenges for concreters who must move continuously around the placement area and may disconnect from anchor points to facilitate movement, leaving them unprotected. Wet concrete and finishing compounds on slab surfaces create slip hazards that can precipitate falls, while concrete buildup on boot soles reduces traction and awareness of edge proximity. Night work during concrete kibble operations is common to avoid traffic restrictions or meet project schedules, with reduced visibility increasing both fall hazards and struck-by risks from kibble movements. Integration of temporary edge protection with permanent building structure requires careful planning to ensure protection systems are adequate throughout construction sequence and can be adapted as permanent elements are installed.

Consequence: Fatality from fall to ground or lower levels, serious injuries from falls into formwork or onto reinforcement steel projecting from incomplete structural elements

Concrete kibble operations involve significant manual handling throughout the process despite mechanical lifting of the kibble itself. Ground crew manually position kibbles for loading under concrete truck discharge, using long-handled tools to direct the truck chute and prevent concrete spillage. After concrete discharge, workers use shovels, rakes, and screeds to spread and level concrete across formwork, performing repetitive bending, reaching, and lifting with loads up to 15-20kg per shovel of wet concrete. Work is performed in awkward postures including kneeling, squatting, and reaching, with workers unable to maintain neutral spine positions while manipulating concrete in formwork. The pace of work is dictated by concrete truck waiting times and concrete workability requirements, preventing natural rest breaks and recovery time between exertion cycles. Kibble cycling typically delivers concrete in waves, with intensive spreading and leveling activity immediately following each kibble discharge, then brief pauses during kibble return and reloading. This work pattern concentrates exertion into short periods without adequate recovery, increasing fatigue-related injury risk. Protective equipment including waterproof boots, gloves, and hard hats adds to physical load and restricts movement, while working on temporary work platforms or incomplete slabs creates unstable working surfaces that increase balance demands and manual handling difficulty. Long shift durations are common during large concrete pours, with operations extending 10-12 hours as concrete trucks arrive continuously and stopping mid-pour would compromise structural integrity, resulting in cumulative fatigue and increased musculoskeletal injury risk throughout the shift.

Consequence: Chronic back injuries from repetitive bending and lifting, acute shoulder and neck strains from overhead reaching, knee injuries from prolonged kneeling on concrete surfaces

Effective concrete kibble operations require continuous coordination between the crane operator in a tower crane cabin potentially 40+ storeys above ground, the dogman managing kibble movements and attachments, concreters at the placement level directing kibble positioning and concrete discharge, ground crew loading concrete into kibbles, the concrete truck driver managing concrete discharge rate, and site supervisors overseeing the overall operation. Communication occurs via two-way radio systems, hand signals per AS 2550, and visual observation of lifting operations, with each method presenting failure modes. Radio communications can be disrupted by distance, building structure interfering with signals, radio battery depletion, or multiple simultaneous radio users causing channel blocking. The crane operator often cannot see the kibble loading area at ground level or the placement location simultaneously, requiring relay of information through intermediary personnel with potential for miscommunication. Standard crane hand signals defined in AS 2550 are effective when line-of-sight exists and personnel are trained in signal recognition, but become ineffective when visual contact is obstructed by building structure or distance exceeds visibility limits. The use of "spotter" or "dogman" terminology can create confusion about role responsibilities when multiple personnel are involved in guiding lifts. Time pressure during concrete placement encourages rushed communications without verification of message receipt and understanding, while the noise environment from concrete trucks, crane operations, and other site activities degrades verbal communication quality. Cultural and language diversity on construction sites can create communication barriers, particularly when workers use non-standard terminology or have difficulty with technical radio communications in English.

Consequence: Suspended load collisions with structure or personnel from misdirected crane movements, dropped loads from premature release commands, crane overloading from incorrect load information, workers in exclusion zones during lifting operations