Actual Temperature Evolution of Thick Raft Concrete Foundations and Cracking Risk Analysis

Abstract EN

Heat of the hydration-induced temperature evolution of a 3.30 m thick raft concrete foundation for wind turbines at the early ages was monitored in situ through a temperature sensor testing system.

The temperature variation patterns and risk of cracking were studied.

Finite element analysis (FEA) conducted on the temperature fields determined the lower thickness threshold requiring temperature control.

A comprehensive temperature control approach suitable for thick raft foundations was proposed based on a practical engineering project.

Temperature monitoring and analysis results showed that the early temperature field evolution featured two characteristic phases: heat accumulation and heat release.

A remarkable temperature gradient was observed along the vertical direction of the foundation.

The maximum temperature difference between the concrete core and the top surface was approximately 35°C, indicating a risk of cracking.

The accuracy of the FEA was ensured by adopting the concrete heat generation rate obtained from the adiabatic temperature rise test.

A further FEA performed on foundations with various thicknesses demonstrated that a thicker foundation corresponded to a higher vertical temperature gradient.

Moreover, a raft thickness larger than 2.50 m corresponded to a maximum temperature difference between the concrete core and the surface higher than 25°C, above which cracking prevention measures should be taken.

Field test results proved the applicability of a suite of temperature feedback regulation measures proposed herein, including layered pouring, thermal insulation, and in situ real-time temperature monitoring, to thick raft mass concrete structures with relatively small volumes.

Good control of temperature difference was achieved using this approach.