Pumice concrete for structural wall panels

Structural lightweight aggregate concrete (LWC) has
been used in many civil engineering applications as a very
convenient alternative to conventional concrete. As a matter
of fact its lighter weight permits a saving in dead load
with a reduction in the costs of both superstructures and
foundations. In addition, the better thermal insulation, the
greater fire resistance and the substantially equivalent
sound-proofing properties (in spite of its minor mass compared
to normal weight concrete (NWC) — see e.g. [1])
make it preferable with respect to NWC itself for nonstructural
uses.
In the last five decades the use of LWC has been
extended to structural elements, thanks to the improvement
in performances obtainable (in terms of stiffness, strength
and ductility) by means of appropriate ingredient mix proportions
[2] and appropriate design of the reinforcement.
Naturally, the use of lightweight concrete has been confined
to large structures (where the beneficial influences of
the reduced weight are greater), and, more in particular, to
structures where a high dead load to live load ratio occurs.
Further, the reduced weight may make LWC preferable for
structures in seismic zones, because of the reduced
dynamic actions, and for precast structures, because it
makes it easier to move the elements to be connected.
More recently, lightweight concrete was also applied in
marine structures (offshore structures and ships), and later
for long span bridges, buildings and grandstands [1]. Referring
to buildings, LWC can be used in structural frames,
but it proves to be more suitable for wall system structures,
where the local ductility demand (in seismic zones) and
the required strength of the materials are reduced and the
dead load to live load ratio is very high.
LWC is manufactured by using different kinds of lightweight
aggregates, available in nature or artificially produced,
so that the properties of LWC depend on the properties
of the particular lightweight aggregate being used.
Natural lightweight aggregate sources can be found in
regions characterized by volcanic activity, where porous
rocks (known as pumices), are available. Artificial lightweight
aggregates (like the expanded clay obtained by
thermal treatment of argillaceous materials) are produced
in many countries, the raw materials being very common.
They may exhibit higher resistance than natural
lightweight aggregates, but this favourable result implies
a greater production cost.
Considering the availability of pumice in the world
and its usability as a natural aggregate for concrete, a
research program has been carried out in order to verify
the mechanical properties of the pumice concrete in
relation to the mechanical standards requested by
present-day codes for structural applications, and in
order to observe its behaviour when used for structural
elements. The main results at the actual stage of this
research are presented through the paper. Specifically,
the results of the tests on lightweight pumice stone concrete
(LWPSC) wall panels subjected to vertical and lateral
loads are shown and compared to those obtained
from similar NWC and lightweight expanded clay concrete
(LWECC) wall panels.
Download File