Civil Engineering Reference
In-Depth Information
According
to
this
recommendation,
the
following
information
should
be
recorded for each batch of RA:
• The material;
• Recycling centre and carrier material;
• Impurities (wood, ceramics, bituminous materials);
• Details on their origin;
• Any other relevant information such as the cause of demolition, a possible
contamination of concrete by chlorides or concrete affected by alkali-silica
reactions.
Concrete with Recycled Aggregates
It is recommended to use RA in concrete whose strength is limited to 40 MPa. The
following values are prescribed for the relationship between some properties of a
concrete containing RA as 100 % replacement of NA and a conventional concrete
containing natural aggregate only: 0.8 for the modulus of elasticity; 1.5 for
shrinkage; 1.25 for creep.
However, due to the scatter in the quality of the RA, there can be a wide
variability in the values of the properties mentioned, and that is why the execution
of specific tests is recommended. For replacement ratios less than 20 % it is
considered, for all practical purposes, that there are no significant differences
between the concrete with RA and conventional concrete.
7.2.11.6 European Standard
The technical committee, CEN/TC 154, ''Aggregates'' has developed an amend-
ment, currently known as EN 12620:2002/PRA1: 2006. This standard is to be a
European
regulation,
changing
the
current
EN
12620:2002
and
its
national
versions.
The standard is to establish requirements for the composition of the coarse RA,
besides their water absorption and density. Also, the maximum amount of chlo-
rides and sulphates is to be controlled. The acid soluble chlorides content is
measured according to prEN 1744-5e. This test, although overestimating the
chlorides content in concrete, is considered to allow for an additional safety
margin. The prEN 1744-5e also suggests measuring the water soluble sulphates,
which are considered as potentially reactive.
This amendment also includes a clause reserved for alkali-silica reactions,
establishing that all aggregates should be classed as potentially reactive unless it is
specified that they are not reactive. The resistance to freeze-thaw cycles and
alkali-silica
reactions,
volume
stability,
in
particular
the
maximum
drying
shrinkage, will be taken into account.
