ALTERNATIVE TECHNOLOGIES                


SURFACE ENGINEERED TILES (Ram Lochan Tiles)



Ram Lochan Tile
The Surface Engineered Block (SEB), with a thin pre-cast tile, can be manufactured in numerous sizes and used in conjunction with diverse materials. It combines a variety of finishes in a manner that brings out the best of the Artist, Architect, Engineer and Artisan - a true reflection of the spirit of Architecture.

The SEB technology is based on a simple rationale; A technology is appropriate, in the true sense of the word, only when it can be adopted for a variety of contexts and can use the local resources to advantage. The SEB was developed after certain aspects of the brick were rationalized and deconstructed as follows:

Soil bearing capacity- 2kg.
Width of foundation- approx. 5 x thickness of wall (cm) @ outset
Strength required at base of wall- 10kg/sq.cm.
Safety factor is 3 x strength required- 30kg/sq.cm.
Brick rating- 100-150kg/sq.cm.
Uniformly distributed load over a 9" wall- 1/3kg/sq.cm/floor.

As can be seen, there is a significant disparity between the performance required of the brick and the rate of compressive strength of the brick. Why is brick rated at 100-150kg/sq.cm? The reason for this is to ensure non-erodibility of the exterior surface not because of load bearing reasons. The SEB meets the criteria for walling material by rationalizing load bearing strength, having non-erodible exterior surfaces and adding aesthetic value to a building.

The SEB technology uses local resources, it is adaptable to a variety of contexts, and meets actual structural and environmental requirements, and therefore is an appropriate technology. By understanding this rationale behind the SEB, anyone can adapt this system to different context specific conditions.

The outer surface of the SEB is a thin tile that can be made with different textures, colours, and materials. The tile is made with a 1:2 mix of cement and marble or stone chips that is cast into a simple mould and de-moulded after about half an hour. (Fig. 1) After 48 hours curing the tile is ready to be used. The tile forms the outer impermeable and permanent surface of a SEB. The composition of the tiles backup block can range from mud, lean concrete etc., to a mixture of flyash, gypsum and lime. A simple mould, (Fig. 2), is used to cast the block. The wedge in the tile ensures bonding between the tile and the backup material to make a pre-finished walling block. The SEB can be used on site after de-moulding and 48 hours curing.

Tile Sizes
The size of the tile can vary but must be durable so that it does not break while being transported or during handling by the mason. The size generally varies from 4.5"(115mm) x 9"(230mm), to 7.5"(190mm) x 15"(380mm), although smaller or larger tiles can also be made. As the size of the tile increases the mixture has to be adequately compacted and uniformly distributed. For this purpose, use of a hand-held vibrator or a table vibrator becomes imperative. Corresponding to the increase in size of the tile, its thickness will also increase.

The thickness of the tile has to be sufficient to prevent warping and ensure non-breakage during handling. The tile thickness can vary from "(6mm) to "(12mm) depending on the size of the tile and the size of the chips being used. For example, a 4.5"(115mm) x 9"(230mm) tile will require a maximum thickness of "(6mm), whereas a 7.5"(190mm) x 15"(380mm) tile would require a thickness anywhere between 1/3"-2/5"(8-10mm). The size of the chips used in the mixture will also be a determining factor in the thickness of the tile. The size of the chips depends on local availability and the kind of aesthetic one wants to develop. Therefore, when locally available chips are large it is more economical to make thicker tiles, rather than spend excessive resources trying to import chips of just the right size.

The width of the wedge should be wide enough for the mixture of cement and chips, to be poured into the mould. The size of the chips being used will be a determining factor in this. The wedge should be durable so that it does not break during handling or transportation. Its depth should be sufficient to ensure a good bond with the backup block material. For instance, if the tile is being used with a Pre-cast hollow-core block then its depth should be less than the thickness of the walls of the block.

The SEB was designed keeping in mind the paradigm that a technology should address engineering principles and simultaneously be aesthetically pleasing and imbibe local talent. Therefore, the SEB can accommodate a variety of finishes that can be integrated while the tile is being cast. The mix of chips and cement, in itself, offers a variety of alternatives. For example, granite or marble chips can be used, or different colour pigments can be added in combination with different coloured and various sized chips (Fig. 4). Another technique involves fixing pieces of glass, bangles, PVC chips, or waste coloured stones etc. on a piece of paper in a pattern. The paper is placed at the bottom of the mould after the mix has been poured in. After the initial setting time, the pieces stick to the tile and the paper can be gently washed off using a wire brush.


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