Composition
Cement boards are mainly cement bonded particle boards and cement fibre. Cement bonded particle boards have treated wood flakes as reinforcement, whereas in cement fibre boards have cellulose fibre, which is a plant extract as reinforcement. Cement acts as binder in both the cases. The fire resistance properties of cement bonded blue particle boards and cement fibre boards are the same. In terms of load-bearing capacity, cement-bonded particle boards have higher capacity than cement fibre boards. Cement particle boards can be manufactured from 6 mm to 40 mm thickness making it extremely suitable for high load bearing applications. These boards are made of a homogeneous mixture and hence are formed as single layer for any thickness. Cement fibre boards are more used in decorative applications and can be manufactured from 3 mm to 20 mm thickness. Fibre boards are made in layers of very thin thickness, making it extremely difficult to manufacture high thickness boards. Many manufacturers use additives like mica, aluminium stearate and cenospheres in order to achieve certain board qualities. Typical cement fiber board is made of approximately 40-60% of cement, 20-30% of fillers, 8-10% of cellulose, 10-15% of mica. Other additives like above mentioned aluminium stearate and PVA are normally used in quantities less than 1%. Cenospheres are used only in low density boards with quantities between 10-15%. The actual recipe depends on available raw materials and other local factors.
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