The Process of Making Cement Asbestos Sheet

The basic methodology of producing the cement asbestos has changed little in the last 100 years.

The Process

  1. Cement and reinforcing fibre (originally asbestos) in a 10:1 ratio are mixed with water to form a thick slurry.  Small quantities of other chemicals, e.g. cellulose is added to aid the manufacture process.
  2. This slurry is transferred into a number of stirred vats to maintain the slurry in suspension.
  3. A rotating cylinder fitted with a sieve cloth is partially immersed in the vat and picks up a thin layer of cement and fibre gradually builds up as the slurry dewaters through the sieve cloth.
  4. A moving belt (Felt) is in contact with the rotating cylinder and picks up the thin primary layers of cement and fibre on the surface of the felt.
  5. The application of vacuum to the underside of the felt aids the dewatering process and gradually an ever increasing thickness of material on the felt.
  6. When the desired thickness is reached the wet sheet is cut and fed off the belt though a series of cross cut knives where the sheet is cut into the required size.
  7. The flat sheets are transferred to an oiled, profiled tin by a pneumatic moulding head and the resultant corrugated sheet is left to cure for 24 hours.  (The tins are oiled to assist with separation after the curing)
  8. Smaller pieces of the cut wet sheet from step 6 are used for hand-moulding.  As the name implies the sheets are hand moulded over preformed glass fibre moulds before being left to cure in the same way as the sheets.
  9. After 24 hours in the tins the finished sheets are inspected, wrapped and transported to the stock yard to complete the curing process for 14 days before leaving the site to the customer.
  10. The standard finished colour is grey but it may be painted either on site or at the factory where water based acrylic paint is spayed onto the preheated (90 deg C) sheets and hand-moulded products.
  11. Finally the equipment must be washed down, thoroughly cleaned and a new felt cloth fitted ready for the production of a new batch of sheets.

The Products

There are a large range of products made at Meldreth, but the most important are:

Profile 3

A corrugated sheet in a varying range of  sizes but all with a 3 inch   distance from crown to crown. This is used for smaller structures.

Profile 6 or BIG SIX

As the name implies, a corrugated sheet of varying sizes but all with a  6 inch distance from crown to crown.  This is used for larger structures.

Flat Sheet

Used for wall cladding

Hand-moulded Goods

Rainwater goods, ventilators, Whaddon tiles, soil goods, bath panels etc. etc.

All of the products come with a 30 year guarantee.

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