Flat fiber cement board grasping process
The process of fiber cement board grasping is as follows:
1) Grasping in free air:
In free air grasping system, cement hardening and hydration bounds are formed in free air, as in other cement based products. After 6 to 10 hours from the time that sheets crossed through the heating tunnel with the approximate temperature of 50 to 60 degrees and the moister of nearly 100% the products have the appropriate strength for movement. The products are separated from the mould and are placed for at least 21 days in, damp free air inside a lidded space to reach their ultimate strength. In products produced in this manner poly vinyl alcohol (PVA) fibers ensure the arming of cement to ensure the tensile strength of the product.
2) autoclave grasping:
autoclave process causes basic changes in hydration materials for example high temperatures causes crystal shape silicate hydrate structures. In fact, the grasping system in free air, silicate hydrate crystals are formed but in very high temperatures in autoclave method the crystal structures are changed and the tobermolit structures are formed and can cause an enhancement in the sheets properties. In this system the cement is mixed with sillies with the approximate ratio of 40% cement and 60% sillies. The initial set is like the previous explanatory method in heat house but the ultimate grasping in autoclave and in the approximate temperature of 180 degree and saturated environment is set by the vapor pressure of 12 loads in which the silicate hydrate is formed. The crystal structure formed gives the product good physical properties which it has tensile tension and so the use of PVA is eliminated. The product produces in autoclave method and after passing the dryer is ready to be delivered to the customer.