MACEDO, R. S.; http://lattes.cnpq.br/5207061220848694; MACEDO, Reginaldo Severo de.
Resumen:
The present work is a contribution to the study of raw materiais and red
heavy clay products to be used in buildings, specially as ceramic bricks
produced in the state of Paraíba. A study was conducted to characterize the
raw materiais employed by potteries and small brick factories as well as the end
products - bricks -usually supplied to the market, according to ABNT rules.
For many years, recent quaternary clays have been largely used to
produce red ceramic products, such as bricks and roofing tiles. These products
are not only extremely important for the building industry but also they are the
most largely produced in the state of Paraíba. Most pottery and brick factories
do not have a quality control program to guarantee their products and there are
hardly any systematic studies with this kind of raw material which renders it
difficult to improve these products and, consequently, to introduce new
industries and factories with appropriate standards.
The present research was conducted on rectangular profile specimens
(6,0 x 2,0 x 0,5cm3) which were compression moulded (20 MPa) from semi-dried
mass. This model allowed us to measure the specimens physical-mechanical or
ceramic properties after drying at 110°C and after curing at 900°C, 1000°C and
1100°C. The ceramic properties in the green state and after curing were
compared with the limiting-values recommended by Souza Santos as well by
Barzaghi and Salge.
The results obtained for the clays analysed indicated that, according to
Souza Santos' specifications, only 16% of the samples investigated can be used
as red ceramics and, according to Barzhaghi and Salge's specifications, 72% of
the clays investigated can be used in the production of solid bricks, 44% for
cored bricks and 32% can be used to produce roofing tiles if a curing
temperature of 900°C is considered. This temperature was chosen as the
closest curing temperature actually employed in red ceramic products for the
building industry.
With respect to the bricks, we concluded that none of the 25 samples
investigated comply with ABNT specifications. The results obtained clearly show.
that there is no effective contrai on the praduction step of these bricks. The
large variation obtained on compression strength and water absorption of each
sample indicate praduction problems, mostly with respect to raw material
homogeneity since there is no contrai on clay particle size, disposition of the
blocks in the oven and curing temperature. Most of the blocks tested showed a
characteristic behaviour associated with badly-cured bricks. They noncompliance
to technical specifications makes it difficult to rationalize the building
process as well as to execute it which leads to significant losses to the market
place.