Environmental Engineering Reference
In-Depth Information
lightweight aggregate and lightweight concrete and its application
in the improvement of the thermal properties of volcanic
lightweight aggregate concrete blocks from canary islands
e. Rodríguez cadenas & a. García santos
Innovative and Sustainable Building Techniques Research Group,
Department of Architectural Building and Construction, Superior Technical School of Architecture (UPM),
Madrid, Spain
aBsTRacT: concrete blocks with volcanic aggregates currently produced in the canary islands
(Bhic) have a high coefficient of thermal conductivity. The application of spanish Building and con-
struction Regulations, known as cTe, leads to the need for multilayer construction systems in external
building walls. These systems are less efficient from an economic and environmental point of view. This
paper focus on the improvement of thermal properties of the Bhic, so that the external building walls can
be executed in the islands using single-leaf masonry without having to add thermal insulation.
1
inTRoDUcTion
called Thermocal
TM
in the physical properties of
lightweight concrete.
Mouli & khelafi (2008) have demonstrated the
convenience of using pre-soaked aggregates, in
the case of aggregates with a high water absorp-
tion coefficient like aPe and aPn, in order to
guarantee that the water in the mixture will not
be absorbed by the aggregates. Due to the absorp-
tion of these aggregates, the water absorbed dur-
ing mixing helps to hydrate the cement particles
in the interfacial zone, which also increases the
bond between the aggregate and the mortar phase.
Guigou Fernández (1997) studied lightweight con-
crete with canarian volcanic aggregates. his study
showed that there are two methods to decrease the
density of lightweight concrete: to eliminate the fine
aggregate, or to use only one fraction of aggregate
(monogranular). according to hummel (1966) the
lightweight concrete has its own technology. This
author emphasizes the relationship between poros-
ity, density and the thermal insulation properties
of the materials. among the procedures he pro-
poses in order to achieve low apparent densities, he
appoints the Bhic lightweight concrete, referred
to as “lightweight concrete with clustered pores
and pores in the granules”, which consists of the
employment of porous aggregates bound with a
small amount of blending material so that intersti-
tial pores are formed between large-sized granules.
The blending of the volcanic aggregates is pro-
duced through the welding of the cement paste in
the meeting points between the aggregates. hence
lightweight concrete has its own technology;
the standard regulations for composition, mix-
ture and compaction of normal concrete do not
apply to lightweight concrete. Therefore, there is
not an ideal granular composition for lightweight
concrete, as in normal density concrete. accord-
ingly, an experimental study has been undertaken
in order to better understand the influence of the
granular fraction of different volcanic aggregates
on the thermal properties of the resulting light-
weight concrete.
concrete blocks are frequently used in the
canary islands owing to clay shortage in this vol-
canic region and they are manufactured with vol-
canic lightweight aggregate concrete. The reference
mixture is composed of volcanic materials: lapilli
aggregate and volcanic slag, cement, sand and
water. This lightweight concrete has a dry absolute
density of 1500-1900 kg/m
3
: the first value is for
the island of Tenerife and the second one, for the
island of Gran canaria. all the available informa-
tion on lightweight concrete indicates that the ther-
mal properties of these mixtures can be improved.
This study examines, on the one hand, the influ-
ence of volcanic material additions such as the
expanded perlite aggregate (aPe 0-6 mm) and the
natural pozzolanic aggregate (aPn 0-5 mm) and,
on the other hand, the influence of different gran-
ular fractions of volcanic lapilli aggregate (aeV
0-12 mm and 0-8 mm) and a thermal mortar
