Temperature monitoring and data logging for thick slab on-site concrete curing

One of Australia’s largest road infrastructure project BrisConnections, involved $4.8 billion Airport Link, Northern Busway (Windsor to Kedron) and Airport Roundabout Upgrade projects, comprising three, linked, road infrastructure projects:

• 6.7km Airport Link toll road (more than 11km of tunnel and ramps) 

• Windsor to Kedron section of the Northern Busway (1.5km tunnel)

• 750m flyover bridge and fast-diamond intersection replacing the airport roundabout.

BrisConnections contracted Thiess John Holland, a joint venture between Thiess Pty Ltd and John Holland Group, to undertake the design and construction of Airport Link, Northern Busway (Windsor to Kedron) and Airport Roundabout Upgrade.

The Requirement:

Thiess John Holland engineers approached Pyrosales to deliver a temperature monitoring and data logging solution to satisfy the Concrete Curing Specification developed for the project.

The Concrete Curing Specification for Thick Concrete Sections applied to any slab 1.8 meters thick or greater. The data monitoring equipment supplied required both visible temperature monitoring for engineers supervising the work, and logged temperature data to provide reports for the project approval process.

The curing temperature had to be monitored at two points at approximately 3m centres, one 50mm below the slab surface and another at the centre of the slab directly below the surface installed temperature element. Depending on the concrete type, the maximum allowable temperature of the curing concrete was between 70-80°C. The maximum allowable temperature differential between the two measurement points was either 20 or 28°C depending on the aggregate used.

Structural Slabs up to two meters thick were poured onto open excavated ground on top of pile driven piers to form the entry and exit tunnel approaches for the project.

Structural Supports were also poured for the Airport Roundabout Bridge Flyover and had to comply with the Concrete Curing Specification.

Supply cost was an important consideration due to the number of sites involved at the same time.

The Environment:

The concrete pouring sites extended across the entire length of the project in five separate locations.

• All locations were open ground with no cover.
• The sites were constantly traversed by heavy road and tunnel construction equipment. Damage to the data logging equipment was a substantial risk.
• Installation of the temperature sensors had to occur during the building of the steel reinforcing grid for  each concrete pour. Each element was sacrificial, remaining in the cured concrete.
• There were multiple sites being poured at the same time.
• The data logging equipment had to be located at a distance from the pour that would not inhibit the construction process.
• All temperature monitoring equipment had to be moveable as the pouring progressed along the site locations.
• The curing temperature data had to be logged for seven days after each pour. 

The Solution:

After several discussions with the client about possible systems that would meet the requirement, Pyrosales supplied the following items:

Temperature Elements and Extension Cable

The elements consisted of a matched resistance thermistor bulb in a waterproof housing and 16 meters of extension cable. Pyrosales maintained stock of the components in ourBrisbanefactory to enable fast production of the elements and security of supply to match the requirements of the project. The cost was reduced through production runs to best utilise the labour input required.

Dual input Data Loggers

These units met the criteria of the application in the following ways: 

• IP68
  
  • Dust and water tight
  • Robust polycarbonate case
  • IEC standard 60529

•  Dual input to monitor the two measurement points required
• Clip mounted and lockable for easy relocation and security during the 7 day logging period
• LCD Display
  • Low battery warning
  • Logging indicator
  • Visual alarm
  • Display alternates between the two channels
  • 10,600 logs per channel
• Low Cost per Unit