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DESIGN OF INTERLOCKING BRICKS FOR ENHANCED WALL CONSTRUCTION FLEXIBILITY, ALIGNMENT ACCURACY AND LOAD BEARING

DESIGN OF INTERLOCKING BRICKS FOR ENHANCED WALL CONSTRUCTION FLEXIBILITY, ALIGNMENT ACCURACY AND LOAD BEARING

 

ABSTRACT

The worldwide housing shortage has stimulated a search for appropriate, easy, fast and cost-effective new ways of wall construction. Among many technologies found to have promise is mortarless technology using dry-stack interlocking bricks/blocks.

This thesis is about such mortarless walling technology and in particular: how to improve wall-construction flexibility, the effects of brick irregularities on wall alignment accuracy and wall behaviour (stiffness, strength) when subject to lateral forces.

The flexibility of mortarless technology (MT) has been enhanced by the development of new bricks (centre-half bat and tee brick): the introduction of closer bricks led to the formation of two new bonds (patterns) namely Shokse and Lijuja bonds. It is now possible to construct more than half-brick-thick walls, to attach more than half-brickwide piers (buttresses) onto walls, and, using special bricks, to construct polygonal and curved walls using interlocking bricks.

Three methods (theoretical modeling, physical experiments and computer simulation) were used to analyze the effects of brick imperfections on wall alignment accuracy.

Theoretical analysis confirmed that brick moulders should concentrate on achieving parallel top and bottom faces rather than achieving true square-ness.

Physical column assembly compared three brick-laying strategies namely: “random”, “reversing” and “replace”. The columns assembled using the “reversing” and “replace” strategies realized alignment improvement factors of 1.6 and 2.9 respectively over “random” strategy. The research also revealed that grooving, to prevent bricks making contact near their centre lines, improved column alignment by factor 2.13 and stiffness by factor 2.0, thus allowing construction of longer and higher walls without strengthening measures.

In order to attain alignment accuracy in accordance with BS 5628-3:2005 in a dry-stack mortarless wall, this research recommends using full bricks with top and bottom surface irregularities not exceeding ±0.5mm for un-grooved bricks, and up-to ±0.9mm for grooved bricks.

Further analysis was undertaken with respect to resource-use implications (cement, water, soil) of employing MT. Using MT will save 50% of wall construction cost and 50% cement consumption, which ultimately will reduce 40% of carbon emissions.

 

 

1.2 RESEARCH JUSTIFICATION

Interlocking bricks may be made of fired clay or cement-stabilized soil (sand). They are usually manufactured by a process using presses rather than slop-moulds, in order to achieve greater uniformity. In Africa this would make them uncompetitive with conventional clampfired bricks, were not the latter being adversely affected by growing firewood scarcity, and the high price of the cement for the mortar.

Production and laying of ISSB are labour intensive, making use of unskilled labour. Apart from saving cost, this will create more jobs and empower youth. Moreover building with ISSB reduces the use of industrial products like cement and depends on local resources. It is considered to an environmental friendly technology, because it consumes less production energy, reduces deforestation, reduces the use of non-renewable resources and produce less waste from construction process than the main walling alternatives (fired bricks, cement-sand blocks) Walker, (1995).

 

 

1.3 RESEARCH METHODOLOGY

The research recorded in this thesis employed three main methods, namely:

1. Literature review

2. Survey of existing structures built of ISSB (mortarless bricks) and design of a more (architecturally) flexible form of ISSB.

3. Analysis, and experimentation;

a. Theoretical analysis of dry-stacking of interlocking bricks,

b. Physical testing of using half-scale interlocking bricks and

c. Computer simulation of dry-stacking interlocking bricks into walls and columns.


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