Clay influence on lightweight brick's properties: Investigating the impact of waste's nature and amount as secondary variables

The present study aims to examine whether incorporating a specific proportion of a particular waste material consistently yields bricks with favorable properties, regardless of the raw clay type utilized. In this context, different mixtures were produced with a clay named AMD2 and 0 wt%, 5 wt% and 10 wt% addition of two wastes named argan nut shell and wheat straw. A first investigation of the used raw clay material revealed the presence of Quartz as a dominant mineral, along with Orthoclase, Illite, and Hematite. Furthermore, the elaborated bricks have been subjected to a physical, mechanical, and structural characterization including loss on ignition (LOI), linear shrinkage (LS), water absorption (WA), apparent porosity (AP), bulk density (BD), and compressive strength (CS). A comparison between the current study and a previous one using the same waste materials and identical proportions of addition but employing a different clay type revealed notable differences in outcomes. In the previous study, bricks fabricated with AMD1 clay and 5 wt% of argan nut shell displayed excellent characteristics. However, in the current investigation using AMD2 clay, bricks with the same waste addition ratio exhibited less favorable properties. Specifically, bricks made with AMD2 clay and 5 wt% argan nut shell showed a loss on ignition of 7.30 %, a linear shrinkage of 3.7 %, a water absorption of 23.3 %, an apparent porosity of 38.20 %, a bulk density of 1.64 g/cm3, and a compressive strength of 9.90 MPa. These outcomes indicated a water absorption above the specified limit and significantly higher apparent porosity compared to bricks produced with AMD1 and 5 wt% argan nut shell, which met standard specifications. This variation highlights how the mineral composition of clay significantly impacts brick properties, even when using the same waste materials and proportions, confirming the importance of considering the raw clay material's nature in bricks' production, and thus emphasizing the need for a preliminary study before combining clay and wastes in order to achieve excellent results.