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Geraldton silos Concrete restoration programme

Constructed from slip formed reinforced concrete, the Geraldton

Silos were designed and constructed in the early to mid 1960s.

The structure consists of 24 interconnected silos in three rows of eight. The void formed between four adjacent cells forms a separate storage area referred to as a star cell. These add a further 14 cells which are used predominately for storage of boutique grains. The main cells are 13m in diameter and 36m in height, resulting in a plan layout of 100m long and around 40m wide. Insufficient hoop reinforcement in the silo walls had resulted in extensive vertical cracking and led to restriction in grain loading and operation. As the silos are also located in a temperate sea side location, 40 years of chloride ingress had also led to significant corrosion to the embedded reinforcement, with resulting in widespread delamination and spalling.

Freyssinet Australia were invited to develop a solution to the restoration of the silos using the company developed silo strengthening system incorporating external post tensioning and proprietary 1X15 anchorages as a design and construct solution. As the other major component of the project was in the field of specialist concrete repair, including both ultra high pressure hydro demolition and dry process gunite reinstatement. In order to verify the Freyssinet techniques for repair and strengthening, initial works included a prototype to an initial three silos. External and internal access was provided using 34 meters of scaffold. Repair areas in these early works were substantial, with around 30% of the surface area reinstated prior to application of protective coatings and external post tensioning.

UHP Solutions has been contacted for 2400 square meters of concrete demolition using a combination of high and ultra high pressure water.

The process requires the concrete removal to be done in all delaminated areas to a depth of between 80 and 120mm without breaking though the 190mm thick concrete cell.

With a limited water supply of just 110lts per minute UHP Solutions has engineered and developed specialised machinery and hand tools to achieve productions rates of removal of up to 14 square meters per day.

A mechanical machine has been developed by UHP Solutions to attach to the existing scaffold and is operated from a safe distance taking away the risk of injury to the operator through flying debris. This machine has been developed in a way that gives UHP Solutions the flexibility to adapt this demolition technique to many different configurations and structures including buildings and bridges.