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Micro concrete roofing tiles
Practical Action
Quality control
To produce a good MCR tile, care needs to be taken in the quality of the sand to make the
mortar. This should have a regular grain-size grading without too much material of one size
and, particularly, without too much fine silty material. If the sand from one source contains
too much material of any one size it should be mixed with a sand of different grading from
another source. In addition, the batching of the quantities of sand, cement, and water needs
to be done accurately to ensure that there is enough cement and that the mix is not too wet.
The tilemaker needs to mould the tile with care and skill, and it is important that the tiles
are properly cured.
With FCR tile production there is some capacity for these quality aspects to be less rigorously
exercised, but with MCR production there is no margin to be lax on quality control if large
numbers of damaged or sub-standard tiles are not to result. If the potential producer cannot
ensure good quality control at all stages of production, then it probably is not a good idea to
produce MCR tiles.
Equipment and materials
The equipment and materials needed to produce MCR tiles are the same as for FCR tiles,
except that no fibre is used and the sand used needs to be of good quality, as noted above.
The essential equipment is:
a tile vibrator
plastic sheets
batching boxes
a water curing tank
a table to work on
The use of a vibrator is essential for MCR
tile production. Vibration helps to
consolidate the mortar mix and removes
air bubbles, which would otherwise cause
weak spots in the hardened tile. The
vibrator unit itself consists of a flat metal
plate which is suspended on dampers and
to which is attached a rotating eccentric
cam. It is the rotation of this cam which
translates into the up-and-down motion of
the plate. A hinged metal cover fits onto
the plate. This defines the sides of the
Figure 1: Place the polythene interface sheet
tile. The vibrator may be driven manually,
electrically with a standard 12-volt truck
battery, or on mains electricity.
Because cement mortar sets slowly and the
tiles need to be left on the moulds at least
overnight before they can be removed, the
producer will need enough moulds to cover a
whole days’ production. A single person
should comfortably be able to make at least
200 tiles per day, and probably considerably
more. (Note: the cost of 200, or more, moulds
should not be underestimated they could
cost more in total than the vibrating unit
itself.) Because it is important that MCR tiles
cure in a damp environment, the enveloping
type of mould needs to be used. These moulds
are stacked one on top of the other and hence
Figure 2: Work the mortar mix under vibration