Synergic effect of recycled paper sludge and expanded perlite on the engineering properties of porous clay bricks: A new mathematical modelling approach

Lightweight bricks produced with addition of different additive materials such as expanded perlite (EP) and recycling paper sludge (RPS) waste have been accomplished by a pug mill. Porous fired bricks were produced by using organic and inorganic additives such as paper waste and expanded perlite as pore-makers. In the experimental study, the seventeen mixture sets were prepared with Box-Behnken experimental design procedure of two additive ratios and firing temperatures. The brick samples were produced with shaping by extrusion method and firing at 850, 950 and 1050 degrees C for two hours after drying. Physical characteristics such as bulk density, apparent porosity and water absorption, and also, compressive strength, thermal conductivity and microstructural properties of brick samples were studied. Influences of process parameters on brick properties were investigated with a detailed neuro-regression analysis. In conclusion, the best brick composition (10 % EP + 10 %RPS by weight) in terms of thermal conductivity corresponding to acceptable mechanical properties was optimized. Accordingly, the compressive strength values of all samples are around 10 to 27 MPa. Also, the samples with high additive content (especially 10 %RPS + 5 %EP sample) exhibited the lowest thermal conductivity value (0.432 W/mK) due to the low firing temperature.

Automated summary

Lightweight bricks were produced using different additive materials such as expanded perlite and recycling paper sludge. A total of seventeen mixture sets were prepared with different additive ratios and firing temperatures. The physical characteristics and mechanical properties of the brick samples were studied, and the influences of process parameters were analyzed. The optimized brick composition (10% EP + 10% RPS) showed the best thermal conductivity and acceptable mechanical properties.