Construction of cement composite using walnut shell reinforced with bacterial nanocellulose gel

The effect of nanocellulose on mechanical, physical, and morphological properties of composites made of walnut shell and cement was investigated. The mixing ratio of walnut shell as a lignocellulosic material with cement at three levels (10:90, 20:80, and 30:70) and nanocellulose at three levels (0%, 1%, and 3%, based on dry weight of cement) were considered as the variables. Boards were prepared according to the ISO 11925-2 (2020) specifications for the fire resistance properties and according to the DIN EN 634-1 (1995) specifications for the mechanical and physical properties. Morphological properties of composites and nano distribute were evaluated by scanning electron microscopic (SEM) imaging. The results showed that boards containing nanocellulose increased the mechanical properties compared with cement board without nanoreinforcement. The modulus of rupture, modulus of elasticity, and internal bonding of the boards decreased with increased walnut shell amount, and its maximum value was obtained when using 10% walnut shell. Nanocellulose remarkably reduced the fire resistance of the boards. The results from SEM showed that nanocellulose can fill the pores of the composite and create a uniform structure, and thus improved the strength of the boards.