Optimization of the production process through response surface method: Bricks made of loess

Loess clays are commonly used to produce bricks. Heavy clays, taken at location near Zrenjanin, Serbia, are used as a representative raw material in this study. The sample, containing about 28% of clay sized particles, is enriched using two more plastic heavy clays from neighboring locations. Chemical and mineralogical content of clays is determined, as well as particle size distribution. Optimization of the processing parameters during the bricks production, i. e. temperature (900–1100 °C), and concentration of 2 clays combined addition (both in the range of 0–10%), is done based on the following independent parameters: compressive strength (CS), water absorption (WA), firing shrinkage (FS), weight loss during firing (WLF) and apparent density expressed as volume mass of cubes (VMC). Developed models showed r2 values in the range of 0.822–0.998, and they were able to accurately predict CS, WA, FS, WLF and VMC in a wide range of processing parameters. The optimum conditions are determined by the response surface method (RSM), coupled with the fuzzy synthetic evaluation (FSE) algorithm, using membership trapezoidal function, with defined optimal interval values, depending on a final usage of the raw material in heavy clay brick industry.