Sawdust Recycling in the Development of Permeable Clay Paving Bricks: Optimizing Mixing Ratio and Particle Size

Abstract

The permeable pavement system (PPS) has effectively contributed to stormwater management as a low-impact development (LID) technology. The suitability of clay bricks, consolidated with waste materials, for sustainable PPS applications in urban infrastructure needs further attention. In this study, several series of permeable clay paving bricks samples were prepared by mixing different ratios and particle sizes of sawdust (SD) with clay soil and firing at 900 °C. The raw soil and SD samples were characterized through sieve analysis, X-ray Fluorescence (XRF), X-ray diffraction (XRD), and Fourier-Transform Infrared Spectroscopy (FTIR). The bricks were tested for their compressive strength, bulk density, apparent porosity, water adsorption, permeability coefficient, and stormwater treatment efficiency. The clay soil comprised 17.5% clay/silt with appropriate amounts of SiO2 (50.47%), Al2O3 (19.14%), and fluxing agents (15.34%) and was suitable for brick manufacturing. XRD and FTIR analysis revealed that the soil predominantly comprises quartz, dolomite calcite, feldspar, kaolinite, illite, and chlorites. The SD samples were enriched with amorphous and crystalline cellulose. The compressive strength of the bricks decreased, while the permeability of the bricks increased with an increasing percentage of SD. An optimal percentage of 10% SD achieved a 21.2 MPa compressive strength and a 0.0556 m/s permeability coefficient, meeting the ASTM specifications for PPS. The optimal size of SD, between 0.5 and 1.0 mm, achieved the desired compressive strength of the bricks. The permeable bricks effectively removed the total suspended solids (TSS), turbidity, and BOD5 from the stormwater, which complies with the guidelines for wastewater reuse applications.