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close this bookProduction Guide - Fibre or Micro Concrete Tiles (SKAT, 1992, 67 p.)
close this folder3. Production process
View the document(introduction...)
View the documentMortar preparation
View the documentVibrating and molding
View the documentMold curing
View the documentDemolding
View the documentTank curing
View the documentAir curing, storage
View the documentTransport

Vibrating and molding

Placing the Mortar

Put a clean plastic interface sheet on the vibrating table, close the frame and put the accurate quantity of mortar on the table by the use of a measuring scoop. Spread the mortar roughly with a trowel before vibrating.

Cleanness

The equipment used (especially the plastic interface sheets) must be clean. The vibrating table and the frame must be free of any old mortar.

Free from Defects

The interface sheet must not have any holes.

Fresh Mix

The mortar has to be used within one hour after water is added to the mix.

Accurate Vibration Time

The vibration time depends on the equipment used and the workability of the mortar. It varies between 20 and 50 seconds.

Vibration is sufficient when water starts to appear on the surface, provided the water to cement ratio is correct. At the end of the vibration, there should be:

l

no water film on the surface;

l

no cracks, holes or air bubbles in the matrix;

l

no lumps of fibre;

and the matrix should have:

l

an even thickness and

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a uniform surface.

Too long a vibration leads to a reduction in the quality of the tiles due to the segregation of the mix components.

Nib Molding and Placing of Fixing Device

When the vibration is stopped, the nib is mounted. The nib mold is filled with mortar which is then tightly connected to the tile by another short vibration.

Hereafter the fixing device is inserted and the tile is again vibrated for a few seconds; then the mortar flush to the nib is cut off with a trowel.

When opening the nib frame, the nib has to be kept down by pressing with a finger.

Molding

After vibration the matrix is moved to the mold, where it must be placed exactly in the correct position, otherwise the shape of the tile will not be correct and this could result in a leaking roof. To ensure the correct positioning the molds should have marks.

During this process no cracks should appear on the surface. Fine hair cracks that may appear are closed by a trowel or a brush.

(The photos show the method using the equipment of J.P. M. Parry & Associates).