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75
HYPOTHESI S FOR THE STUOY OF NEW BRICK PROOUCTS
GIORGIO CERAGIOLI
GIOVANNI CANAVESIO
FRANCESCO OSSOLA
Politecnico di Torino
Oipartimento di Casa Città
Dipartimento di Ingegneria dei Sistemi Edilizi e Territoriali
Viale Mattioli 39 - 10125 TORINO - ITALY
ABSTRACT
In relation to studies and research that have been carried out in the
domain of production and application problems of brick/block masonry ,
the authors work on the assumption of a " design line " to study new
products based on simplification of building processes as well as on
performance suboptimization of brick products in relation to a set of
performances easily adaptable according to the specific climatic
environment and application requirements .
INTROOUCTION
Research work and studies dealt with in the present paper followed up on
the results of a previous research work , that SI . TE . RICERCHE Srl of
Torino (Italy) had carried out for ROB Spa of Piacenza (Italy) . Such
results had in fact generated some general assumptions that applied to
specific bui l ding requirements typical of industrialized countries :
need to simplify building processes in order to facilitate employment
of less skilled labour and favour self- construction by building
users ; need to suboptimize brick size performance in relation to production
processes and construction systems so as to achieve low energy
content production meeting standard quality specifications;
need to produce brick products meeting a wide range of performance
specifications , easy to adapt and optimize in relation to different
sets of performance requirements (e.g . different combinations of
insulation and thermic inertia) , widening their range of use in
76
different climatic environments and applications.
The present brick masonry market partly satisfies to these needs through
some products such as those that are used in "construction systems" ,
integrating basic elements (blocks) with special components , t h us
ensuring technological building homogeneity and/or improving integration
with other sections of the building. Other recently introduced examples
are "guided-fit" elements featuring significant dimensional accuracy ,
that can be dry- built and then set by casting materiais through t heir
specific hollow sections. Other issues, however , such as specific
material structure and the development of its performance an d functional
specifications do not seem to attract due interest . In particular , the
extremely interesting and still very open issue remains of the as
sumption that , on average , brick products feature a "performance
surplus " in relation to present construction systems and/or ap
plications. This is not such a surprising statement when one considers ,
for instance, the significant strength surplus of a face brick in a
building with reinforced concrete skeleton. Its implications are
certainly relevant to the creation of new lines of brick masonry
products. The first of them is clearly a "targeted" decrease of some
spefications (basica l ly the highest surplus ones) so as to achieve
significant benefits in terms of cost and other issues (e . g . lower
energy consumption in production) . The second consideration , partly
following upon the first , is the need to design brick products f eaturing
different layers , each meeting a different requirement , so as to certify
each layer according to application- specific requirements . This would
ensure product "quality" through a much more in- depth and adequate
relationship between application "requirements" and product
" specifications" or,
" benefit" ratio.
in other words, through a more balanced "cost"-
HYPOTHES IS FOR A NEW PRODUCT
Following alI this, it is possible to assume and research a new line of
brick products consisting of large-sized tiles featuring a large centre
hollow section ready to be fi l led with whatever layer of material best
suits requirements . Such tiles mus t be easily juxtaposed by either dry
method or using binders to build perimetral and some times also inside
walls, so that , once the erection is completed, the centre hollow
sections may be filled with materiaIs meeting the specific functional
requirements of that construction work. Some suboptimizations are thus
feasible , since , even where minimum strength sections are used , this
brick product retains its resistance against externaI agents , thus
supplying the structural base or "she ll". .l\t the same time , i t is
possible
building
filling
to funct ionally design the construction process according
requirements and constraints through an adequate selection
materiaIs , which are e asier to f i nd locally, and that may
to
of
be
..
-
77
either lower cost or lower energy- content products , though they still
meet the specified masonry requirements .
BASIC ELEMENT SPECIFICATIONS
The reference element upon which a first set of theoretical assessments
was ma de consists of a large block (Figure 1) featuring the following
specifications :
. / 3 standard tile, specific weight 1800 Kg m ;
dimensions:
- seam cutting span = 24 cm. ;
- maximum extrusion = 49 cm. ;
- minimum extrusion = to be determined (according to an analysi s of
the different application requirements providing performance
suboptimization) ;
externally pierced tile walls (piercing percentage around 50%),
thickness 4 cm.;
cross inner wa ll - connecting baffles reduced to minimum section needed
to provide adequa te strength;
edges shaped so as to facilitate juxtaposition , interlaying mortar or
~onding agent , or dry building.
Hollow section filling is assumed , in t his initial hypothesis, to use:
a) insulating materiaIs:
1) polysterene foam in situ;
2) urea resin foa m in situ ;
3) e xpanded pearlite aggregate ;
4) light expanded clay aggregate (LECA);
b) other aggregate materiaIs:
5) dry sand;
6) dry graveI;
7) natural pumice;
8) foamed slag ;
c) concrete mix castings:
9) expanded clay concrete;
10) standard concrete .
It is hardly worth stressing that, when standard concrete is used as
filling mater ial, tile hollows take on the typical function as "lost"
formwo rk elements where skeleton pillars are cast, or as elements suited
to antiseismic "reinforced masonry" construction. Expanded clay concrete
castings may also be used in this last application ( provided the
relevant static checks are carried out first) .
externally pi ere ed tile wall
241 em
78
. e ros s inner wall - eonneeting
Figure 1 . Basic block element with hollow section
~
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79
THEORETICAL ASSESSMENT OF PERFORMANCE
Performance of the range of solutions for perimetral walls built by
filling the basic brick element with the above mentioned materials may
be firstly assessed by focusing on the two basic specifications taking
into account stationary and variable heat transmission: unitary
Transmi ttance K (1) and Thermal Time Constant T o T o C o (2) , the latter
being adopted as significant parameter of thermic inertiao Theoretical
results of such initial assessment, supplying fairly clear- cut
information despi te i ts conciseness , are reported in Figure 2 , where
performance has been calculated in relation to overall brick element
thickness from 17 to 37 cmo and surface finishing consisting of outer
plastic plaster and inner cement plaster (overall wall thickness between
20 and 40 cm o ) o
With reference to such assessment, the following should be taken into
account :
1) The purpose of thickness variance is clearly to provide information
upon which to select the most adequa te thickness of the element (to
be finally defined wh en going into production) to meet assumed
application requirements through its range of filling alternativeso
2) Selection of outer plaster type is rather significant, since it must
ensure adequate waterproof features, which cannot be expected from
the 4cm o- thick basic brick element outer layer alone o
3) "Condensate forming " has also been checked, though i t is less
relevant an information than Transmittance and Thermal Time Constant :
it is in fact the result of anomalous environmental conditions , and
it can be avoided by selecting specific filling materials or it can
be controlled by fitting in a specific layer (which can be an outer
layer) o
4) " Thermal bridges", however, raise a problem the solutions to wh ich
have only been partially explored : at the present stage , however ,
some interesting indications point out new construction thermal
bridge- control specifications , which are in fact based on the h ollow
section of the brick element o
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81
CONCLUSIONS
These proposed new brick elements provide some general indications for a
new line of products , saving further in- depth research and operational
testing .
a) Possibility of integrated "dimensioning" of thermal performance by
building walls , for instance , with low Transmittance and Thermal Time
Constant values (or, on the contrary, with high values) , i.e .
relating insulation to thermic inertia according to the climatic
environment of the building (3) , something that is very hard to do
when using other one - purpose application potential technologies .
b) Possibility of achieving different performance values in walls f acing
different environmental climatic conditions, implementing, for
instance , lower transmittance in North- facing walls and highe r
thermic inertia in South-facing walls (since they get more summer sun
radiation). AlI t h is can be achieved by changing the material f il ling
the two walls, without changing the brick element o
c) Possibility to use filling materiaIs such as sand or graveI wh ich,
lacking thermal insulation requirements, are very suitable for Iow
cost construction appIications, sir.ce they are generally:
- easiIy avaiIabIe 10caIly,
- low- cost ,
- very low energy- content.
d) Achievement of optimum insulation and thermic inertia vaIues (see
Figure 2) by means of specific filling materiaIs , such as pumice ,
featuring low thermal conductivity together with an apparent much
larger absolute gravity than that of typical insulating materi aIs .
With reference to pumice , there is t he additional a dvantage of using
natura l material that is extractible and usable through relatively
low- cost and very l ow energy- content processes.
e) Weight r eduction of brick elements produced , bringing about possible
ergonomic benefits , since construction using lighter (and larger)
elements provides better " construction performance", i . e . masons
raising a larger wall surface by unit of time ; this is however a
debatable indication , since filling must follow raising with the
re l evant additional times taken .
Final l y , it is interesting to see how , among the materia I s that can be
used to fil l the brick element hollow section , light expanded clay
aggregate (LECA) allows for high performance leveIs (also with regard t o
thermic inertia) with minimum wall overall thicknes s of 40 em . Th i s is
a rather interesting thing, since clay can be defined as a brick works
type of material . Further investigation may outline suboptimization
leveI s to be ac h ieved through adequa te granulometric selection with the
possible a ddition of sand (filling gaps between clay aggregate grains) ,
thus improving Thermal Time Constant , though at the expense of a
restrained increase in Transmittance.
(1)
(2)
82
NOTES
2 Unitary Transmittance K, expressed in w / m °c , is the heat f10w
going from one f1uid to another through a wa11 under stationary
conditions , mu1tip1ied by wa11 surface sq. mt . and °c of difference
between t he temperature of the two f1uids (UNI 7357 . Ca1cu1at i on of
therma1 requi rement for bui 1d ing heating) .
Therma1 Time Constant, expressed in hours , is the ratio
thermic energy stored in the wa11 per degree of increase
average temperature Qa , and heat f10w K* transmitted per
difference in t he temperature , both r eferred to the front
of the wa11 itse1f . For a wa11 consisting of N 1ayers:
Q
N a.
1 TTC i~l K*
i
where Q 2 p. s cp . (kJ/m °C)
a 1 i 1 i
between
in its
unit of
surface
With reference to Ki ' if t h e 1ayer sequence se1ected is inner to
outer , Ki is the f 10w going through to the i - th Iayer mid section ,
so that :
[ ~" s s s ::J I 1 2 i - 1 1 (m
2 °C/W) + - + - + ..... + -
K* À 1 À, À 2 i i - l
(3) See " Guida aI controllo energetico della progettazione" (Guide to
energy control in design), white book on results achieved in
relation to Subproject "Energy saving in building heating " of the
Energy Finalized Project of the Italian National Research Council .
AIso see Appendix 4 : "Consigli progettuali per l 'edificio e per
I ' impianto . Indicazion i di 15 Iocali tà i taliane " (Design
suggestions for the building and the heating system. Instances from
15 Italian sites) .
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