Samtidig temperatur- och fuktrörelser i ung betong

• Main Author: Eriksson, Nicklas
• Format: Bachelor Thesis
• Language: English
• Published: 2014
• Subjects: Technology; Teknik; Autogen krympning; basic shrinkage; autogenous shrinkage; autogenous deformation; Thermal dilation; young concrete; ung betong; relativ fuktighet; relative humidity; Luleå
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-56456

Basic shrinkage is the free contraction of a concrete body during the hydration of concrete, with exception of the movements caused by thermal dilation and moisture-exchange with the concrete body’s surrounding environment. For concretes with low w/s-ratios (low amount of blending water compared to cement), basic shrinkage is an significant factor concerning crack-risks in young concrete.There exist two models for calculation of basic shrinkage that has been developed at LTU (Luleå University of Technology) based on the maturity concept, but their accuracy can be questioned as they have not been tested against different temperature developments. The goal for this master thesis is, therefore, to control, or give a basis for, if these models are accurate or not, and if the temperature development affects the magnitude of basic shrinkage or not regarding the tested concrete. The used test method itself is also evaluated.To get a understanding for the problem a literature study was done about basic shrinkage, related phenomenon and existing models used at LTU. Tests have then been performed on the new base concrete “BAS2” through measurements of shrinkage and relative humidity done with several different temperature developments. Relative humidity has relevance as self-desiccation is a strongly contributing factor to the magnitude of the basic shrinkage. The existing models are then used to interpret and analyze the measured results. The results from measurement of shrinkage show that the second model that has been developed at LTU works significantly better than the first, and that good individual fitting is possible for all temperature developments individually. However, it is not possible to get one good fitting for all temperature developments, especially at low temperatures. The “bad” fitting seems to be more because of that the thermal dilation shows different properties at the different tests, rather than that the basic shrinkage necessarily is described wrong. Comparison of the basic shrinkage between the ...