rice husk and old corrugated container cement boards: performance of nano-sio2 on strength and dimensional stability

in this study the effect of nano sized silica particles (nano-sio2) on the physical and mechanical properties of rice husk and old corrugated container (occ)-cement boards was investigated. modulus of rupture (mor), modulus of elasticity (moe), internal bonding strength (ib), density, water absorption and thickness swelling after 24 hours immersion in water and hardness were measured. results showed that rice husk-cement boards with 2% nano-sio2 demonstrated the best physical and mechanical properties. it is related to better distribution and compaction of particles during compression without particles agglomerating. a higher property of 2%-nano-sio2 content rice-husk-cement boards was confirmed by their higher hydration temperature. addition of 3% nano-sio2 to the mixture reduced the density because of both the substitution of denser cement particles by lighter nano-sio2 particles and air-entrapment in the boards. furthermore, scanning electron microscopy (sem) analyses showed that the optimum amount of nano-sio2 (2%) can fill micro pores and make a uniform structure with a rough surface which improves properties of composite boards.