Advanced

Simulering av betong under härdning

Sjöbeck, Henrik (2007) VSM820
Structural Mechanics
Civil Engineering (M.Sc.Eng.)
Abstract
Concrete hardens as a result of chemical reactions between water and cement. Cement is a hydraulic binder, in the reaction the cement binds water-molecules. This is an exoterm process, heat is produced during the reactions. How fast this process proceeds is much depending of the temperature.

The amount of heat produced during the hardening of the concrete is also depending on the thickness of the structure. While heat is produced in the concrete the material will expand but when the concrete is becoming cooler the shrinkage is prevented. This results in tensionstresses at the surface of the concrete. This phenomenon is particularly common in large structures where the temperature-distribution is nonuniform.

There are several measures... (More)
Concrete hardens as a result of chemical reactions between water and cement. Cement is a hydraulic binder, in the reaction the cement binds water-molecules. This is an exoterm process, heat is produced during the reactions. How fast this process proceeds is much depending of the temperature.

The amount of heat produced during the hardening of the concrete is also depending on the thickness of the structure. While heat is produced in the concrete the material will expand but when the concrete is becoming cooler the shrinkage is prevented. This results in tensionstresses at the surface of the concrete. This phenomenon is particularly common in large structures where the temperature-distribution is nonuniform.

There are several measures which can be used to avoid cracks in concrete. One method is to replace some of the concrete’s water with ice and thereby get a material with a decreased temperature. Nowadays there are computer-programs, like Hacon, capable of performing simulations of the temperature and stressdevelopment.

In order to receive a good and reliable result from the computer- calculations it is required to have good knowledge about the concrete used. Every property of the material is in the program described by several parameters. For example the development of the compressive-strength is described by four parameters.

Temperaturemeasurements in newly placed concrete have been carried out at Vattenfall Research and Development AB. On the basis of these measurements parameters that describe the development of the hydration for two types of cement have been calculated.

The temperature-development in large concrete walls have been calculated using Hacon. The result has been compared with measured temperatures and the resemblance is very good. (Less)
Please use this url to cite or link to this publication:
author
Sjöbeck, Henrik
supervisor
organization
course
VSM820
year
type
H3 - Professional qualifications (4 Years - )
subject
report number
TVSM-5146
ISSN
0281-6679
language
Swedish
id
3566841
date added to LUP
2013-08-05 12:08:19
date last changed
2013-10-07 12:13:45
@misc{3566841,
  abstract     = {Concrete hardens as a result of chemical reactions between water and cement. Cement is a hydraulic binder, in the reaction the cement binds water-molecules. This is an exoterm process, heat is produced during the reactions. How fast this process proceeds is much depending of the temperature.

The amount of heat produced during the hardening of the concrete is also depending on the thickness of the structure. While heat is produced in the concrete the material will expand but when the concrete is becoming cooler the shrinkage is prevented. This results in tensionstresses at the surface of the concrete. This phenomenon is particularly common in large structures where the temperature-distribution is nonuniform.

There are several measures which can be used to avoid cracks in concrete. One method is to replace some of the concrete’s water with ice and thereby get a material with a decreased temperature. Nowadays there are computer-programs, like Hacon, capable of performing simulations of the temperature and stressdevelopment.

In order to receive a good and reliable result from the computer- calculations it is required to have good knowledge about the concrete used. Every property of the material is in the program described by several parameters. For example the development of the compressive-strength is described by four parameters.

Temperaturemeasurements in newly placed concrete have been carried out at Vattenfall Research and Development AB. On the basis of these measurements parameters that describe the development of the hydration for two types of cement have been calculated.

The temperature-development in large concrete walls have been calculated using Hacon. The result has been compared with measured temperatures and the resemblance is very good.},
  author       = {Sjöbeck, Henrik},
  issn         = {0281-6679},
  language     = {swe},
  note         = {Student Paper},
  title        = {Simulering av betong under härdning},
  year         = {2007},
}