Early-age shrinkage control and strength development of concrete

Title: Early-age shrinkage control and strength development of concrete
Author(s): C.R. Braam, H.W.M. van der Ham, E.A.B. Koenders
Paper category : conference
Book title: International RILEM Conference on Volume Changes of Hardening Concrete: Testing and Mitigation
Editor(s): O. M. Jensen, P. Lura, K. Kovler
Print-ISBN: 2-35158-004-4
e-ISBN: 2351580052
Publisher: RILEM Publications SARL
Publication year: 2006
Pages: 185 - 194
Total Pages: 10
Nb references: 11
Language: English

Abstract: Concrete exhibits time-dependent behaviour, mostly referred to as shrinkage and creep. This paper deals with one of the components of shrinkage, namely the deformation of earlyage concrete not caused by external drying of the material.
Concrete having a ‘traditional’ strength (e.g. compressive strength up to about 60 MPa) hardly shows any shrinkage deformation when its drying is prevented, for instance by sealing. The development of high, very high and ultra high strength concretes has shown that these concretes are prone to shrinkage, even when they are prevented to dry. Research has demonstrated that internal rather than external drying was the cause of this phenomenon. It appeared that traditional concretes have such a water-binder ratio, that there is always an overdose of water present. This overdose evaporates from the concrete when it is allowed to dry, causing the well-known ‘traditional’ shrinkage. (Ultra) high strength concretes, however, have a water-binder ratio that low, that there is less water present in the mixture than required to hydrate all binder material. During the hardening process the internal demand for water is higher than the amount of water available. This is called ‘internal’ drying and causes the concrete to shrink (‘autogenous shrinkage’), even when it is sealed [1]. Deformations as such do not have to cause problems for a structure. However, preventing deformations to occur introduces stresses and these might result in damage when the material’s strength is lower than the stresses caused by restrained deformation. To investigate both, tests were performed on prismatic specimens either free to deform or with fully restrained deformation. The time-dependent behaviour of a series of mixtures was compared, ranging from traditional and high strength concrete to ultra high strength steel fibre reinforced concrete.
The specimens were sealed and their deformation was registered as soon as measuring devices could be attached or they were prevented to deform, measuring the force required. Control specimens (cubes) were stored under the same conditions and were tested to obtain information about the actual splitting tensile strength development. In a separate test series the influence on shrinkage of adding a superabsorbent polymer [2] was investigated of which the functioning is based on so-called internal curing [3].

Online publication: 2006-07-30
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/2351580052.020