Modelling of Early-Age Temperatures for Thermal Control of Massive Pile Caps for the Gateway Bridge

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Title: Modelling of Early-Age Temperatures for Thermal Control of Massive Pile Caps for the Gateway Bridge

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Publication: CIA

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Date: 2/28/2011

Abstract:
The main span pile caps of the New Gateway Bridge are 3.2m thick and high early temperatures were expected during construction due to heat from cement hydration, causing some concerns regarding strength, durability and cracking. To satisfy requirements for strength, durability and crack control, maximum criteria for peak and differential temperatures were established based on published data. A concrete containing 50% GP cement, 29% fly ash and 21% slag was adopted to reduce and delay the heat of hydration. An air cooling pipe system was used and suitable insulation was placed on all pile cap surfaces to reduce peak and differential temperatures. The CIRIA C660 programs were used for temperature modelling with some necessary modifications to suit local materials and conditions. Early-age temperatures in the pile caps were modelled based on heat from cement hydration, concrete placing temperature, insulation characteristics of the pile cap subgrade, side forms and top cover, and estimated air flow rate in the cooling pipes. An air cooling pipe system was designed and installed based on the modelling outputs. Measured temperatures at some key locations during and after the concrete pour were compared with the predictions and were checked against maximum criterion, with satisfactory results achieved.


Concrete Institute of Australia, International Partner Access.

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