Prediction and Optimization of Heavy Clay Products Quality - Advanced Materials for Agriculture, Food and Environmental Safety - page 89

(SOPs). h e focus of this study was to determine the optimal material
composition and i ring temperature, depending on a i nal usage of the raw
material in heavy clay brick industry. h is approach enables shortening
of all the necessary analyses when exploring brick clay deposits, by pre-
dicting the i nal products' features on the basis of raw material chemical
characteristics. h e optimization algorithm used in this study is concerned
with i nding the maxima of objective functions, subject to constraints.
Described mathematical models, applied together, will be extremely help-
ful in preserving the raw natural resources, and lowering the industrial
waste and energy consumption.

4.2 Materials and Methods

4.2.1 Raw Materials and Samples

Representative 139 heavy clays tested are collected in Serbia from the
new opened brick factory deposits. Prior to sample preparation, all the
raw samples were oven-dried at 105 ° C and then milled following the
usual practice in ceramic laboratories [ 4]. To simulate industrial process-
ing conditions, the heavy clays were moistened, mixed, and milled to the
particle size of 2 mm until homogeneous mass was obtained. Moisture in
the samples was uniformed by resting for 24 hours in sealed nylon bags. A
laboratory vacuum extruder (Händle) was used to produce tiles (120mm
x 50mm x 14mm), hollow blocks with vertical voids (55.3mm x 36mm x
36mm), and cubes (30mm x 30mm x 30mm). At erwards, samples were
slightly dried in the air and in a laboratory dryer at 105±5 ° C [3]. h e
i ring step was done in the computer-controlled oxygen atmosphere fur-
nace, by choosing the slow i ring regime: up to 610 ° C , the average heat-
ing rate was 1.4 ° C/min, while at higher temperatures it was increased to
2.5 ° C/min until the i nal temperature was reached at which the samples
were treated for 2 hours. All tested samples were i red under the same
regime up to the i nal temperatures of 800, 820, 850, 870, 900, 930, 950,
1050, and 1100 ° C. At erwards the samples were furnace-cooled to room
temperature.

4.2.2 Chemical and Technological Features

Heavy clay chemical composition was tested by classical silicate analysis
[11], and the results are presented as average values determined by three
measurements.