Civil Engineering Reference
In-Depth Information
a porosity that allows them to accommodate the product expanding into the
cementitious matrix without causing cracking or affecting the mechanical prop-
erties of concrete.
Finally, it is observed that this standard specifies a maximum content of water-
soluble chlorides, unlike, for example, in Germany or Hong Kong, which suggest
limitations on acid soluble chlorides. Such complacency is explained by the low
level of demand to which the concrete is subjected, where the chlorides concen-
tration and its effects are not so burdensome. However, it should be noted that the
suggested value of 1 % appears very high, considering that it is a percentage by
weight of aggregates.
7.2.2 Germany
In Germany, there are two standards, presented below, the first of which refers to
the requirements of CDW aggregate, while the second proposes rules for the
implementation of these aggregates in concrete.
7.2.2.1 DIN 4226-100 ''Aggregates for Mortar
and Concrete—Recycled Aggregates''
This standard specifies requirements for aggregates with particle density higher
than 1,500 kg/m
3
for use in mortar and concrete. It also specifies the system of
production control and conformity assessment. The particle size must follow the
requirements specified in DIN 4226-1 ''Aggregates for concrete and mortar—
normal density and high density aggregates''.
Classification of Aggregate
In the German norm DIN 4226-100, CDW aggregates are classed into four types:
(1) waste concrete, (2) CDW, (3) Masonry waste, (4) mixed material.
The classification of CDW aggregates is based on their composition and origin.
The first type is mainly composed of waste concrete. Type 2 is slightly more
embracing than type 1, i.e. a scenario of demolition of a concrete building, where
concrete is the major constituent but a portion of masonry may also be included.
Type 3 includes those cases in which masonry is the major constituent, but some
concrete may also be included. Type 4 is somewhat restrictive and can more easily
represent a scenario of a recycling centre where one can see a bit of all materials,
but where concrete and masonry are dominant.
