Software Option for Plus versions

Heat of Hydration Analysis

Version 14.2 of LUSAS Civil & Structural and LUSAS Bridge products permit modelling the heat of hydration of concrete for a variety of cement types. Effects due to the addition of fly ash and ground granulated blast furnace slag can also be included. When used in conjunction with Nonlinear, Dynamic, and Thermal software options the heat of concrete hydration can be computed during a thermo-mechanical coupled analysis and the temperatures and degree of hydration can be read in to the mechanical analysis. Currently the mechanical properties of the concrete can only be defined as a function of temperature.

Overview

The concrete heat of hydration facility mplemented in LUSAS caters for cement types I, II, III and V. Effects due to use of fly ash and ground granulated blast furnace slag can also be taken into account. Although the mechanical properties of concrete cannot be directly linked to the degree of hydration, it is possible to define concrete properties that are appropriate for the time when the greatest temperature differential occurs. Typically this occurs between 24 and 48 hours so mechanical properties appropriate for this time interval could be specified to assess any possibility of cracking. The implementation allows you to enter the chemical composition for any cement type should the need arise. Heat of hydration results from LUSAS have been validated against academic research (carried out by Schindler and Folliard) and also against a standalone commercial heat of hydration program.

Heat of hydration example : Test cube

This quality assurance test case, whilst simplistic, illustrates the benefit of using this facility perfectly. A cube of concrete is modelled with an 8x8x8 mesh of HF8/HX8 elements and the concrete curing process is simulated. Temperatures due to the heat of hydration can be obtained by examining the hourly timestep results. From the results it could be seen that the greatest temperature differential occurs at 35 hours. A structural analysis using a concrete cracking model based upon mechanical properties for this time interval is then carried out and cracks can be observed when differential expansion is enough to cause principal stresses that lead to material failure. In this example the external thermal boundary conditions were chosen to emphasize the heat gradient across the concrete block, and in the structural analysis the block is free to expand unrestrained.


Animation of temperature change in mid-section of concrete block

Crack planes at 35 hours

Maximum principal stresses at 35 hours

Application example: Dam construction

Heat of hydration analysis and a semi-coupled structural analysis is carried out on a simple testcase model of a dam that is constructed in three stages. Results for the heat of hydration analysis are plotted on section slices through the model. Structural analysis results include the effects caused by an aging Young’s Modulus as a result of defining concrete creep properties.

Heat of Hydration example : Dam

Maximum temperature differential in first casting stage

Maximum temperature differential in second casting stage

Maximum temperature differential in third casting stage

Semi-coupled Thermal / Structural example : Dam

Maximum surface stress in first casting stage Maximum surface stress in second casting stage Maximum surface stress in third casting stage

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Any modelling and analysis capabilities described on this page are dependent upon the LUSAS software product and version in use.

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