Development of properties as a function of temperature
A comprehensive test series has
been undertaken in the Expert Centre in order to investigate the
applicability of Freisleben-Hansens maturity concept from 1977 [1]
to modern concretes exposed to aggressive environments. This
involves an examination of the influence of the curing temperature
on the development of properties such as compressive strength and
resistance against chloride ingress.
Preliminary results indicate that
the original maturity function probably needs to be revised in
order to be consistent with the types of concretes used nowadays.
The investigations have also revealed some very interesting and
surprising behaviour regarding to the chloride migration
coefficient (CMC): For pure CEM I concretes, the CMC at similar
maturity increases with increasing curing temperature, whereas the
opposite is observed for the fly ash concretes, i.e. the resistance
to chloride ingress is greatly improved for fly ash concrete by
high-temperature initial curing. These findings have been confirmed
by a series of experiments with heat curing of concrete in isolated
form work.
An extended abstract and two
presentations dealing with the abovementioned results can be seen
here:
Extended abstract from NCR workshop on Durability
Aspects of fly Ash and Slag in Concrete (2012): Influence of curing
temperature on development of compressive strength and resistance
to chloride ingress of concrete with different binder
systems
Development of properties as a function of temperature_NCR workshop
Oslo
Development of properties as a function of temperature_Example of
practical application
Recently, a further investigation have been undertaken at the
Expert Centre with aim of (1) testing the applicability of the
maturity concept to modern concretes and (2) to investigate the
effect of the curing history of laboratory samples cured at
elevated temperatures.
This investigation actually shows that the commonly used
maturity concept is still applicable to modern concretes.
Concerning the impact of curing history, interesting findings
include that at 28 days of maturity, the strengths of concretes
cured at a constant temperature of 60 °C are significantly lower
than the strengths of similar concretes cured at 20 °C. For
concretes exposed to a gradually increasing temperature going from
the curing temperature to 60 °C, only a slight decrease in strength
is observed for the pure cement concretes while the strength of the
concretes with binder systems containing fly ash actually increase.
Results from the investigation can be found here:
Test of maturity concept and influence of curing
temperature on strength development of concretes (in
Danish)
[1] FREISLEBEN-HANSEN P AND
PEDERSEN J, Maturity Computer for Controlled Curing and Hardening
of Concrete. Nordisk Betong, Vol. 1, 19-34, 1977.