General design principles
5.2 Walling systems
5.2.1 Cast in situ fly ash walls
Using a high fly ash mix comprising cement, lime, fly ash and sand in appropriate proportions, depending on the quality of fly ash with a pre‐measured water: cement ratio, cast‐in‐situ walls can be built. These can be cast to any thickness using a steel shuttering. By using this system 20% economy, quicker construction, good finish on both the sides of the wall and more carpet area can be achieved. Similar walls can be cast using Fal – G cement.
5.2.2 Reinforced and or grouted brick masonry
Grouted masonry is done in two widths of burnt clay brick, concrete block, or the stone units in which the interior joint called the ‘collar joint’ is filled with grout. This bonds the two widths together as well as provides the space wherein the reinforcement can be located and bonded to the surrounding masonry. The thickness of the grout between masonry units and reinforcement should not be less than a quarter
inch except that steel wire reinforcement may be laid in horizontal mortar joints, which are at least twice the thickness of the wire’s diameter. Grout must be placed in a manner that it fills the entire void and does not become segregated due to improper fluidity during placement. This technology is highly suitable for earthquake‐
prone areas and multi‐storied residential construction. The details at the corner are shown in figure.
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5.2.3 Interlocking bricks or Lok bricks
The interlocking soil cement bricks are made in a CINVA‐Ram brick making machine.
The rims and corresponding recesses have been raised on the lower surfaces to receive the projecting rims of the brick below (as shown in the fig).
Placing – They have narrow vertical recesses and vertical reinforcement is poured in the grout holes before pouring the grout. When cement grout is placed into them, the blocks become permanently locked together.
Advantages – These bricks are earthquake‐resistant and allows for multi‐storied construction.
Dimensions – The length is twice the breadth, the length, breadth and height are 250x125x10mm so that right angle corners can be achieved without the use of special corner blocks, and interlocking and alignment are achieved automatically. A typical single and double brick wall construction as shown in the figure.
Figure showing the rims and recesses Lok Brick: single and double brick wall in the Lok bricks for adequate bonding
5.2.4 Reinforced/hollow brick masonry
Reinforced/hollow brick masonry is used as structural members for floors, roofs, and walls and as filler blocks to replace concrete in the tensile zone. The overall dimensions available are 25x27x10.3cm with various configurations of rectangular hollows in it. These blocks are also designed separately as bond beams, joist members as well as filler blocks.
The reinforcement is placed in the hollow and concreting is done over the brick.
Ratio – The maximum thickness to height ratio is 1:25, with the minimum thickness being six inches. Hollow unit masonry is a type of wall construction that consists of hollow masonry is a type of wall construction
that consists of hollow masonry units set in mortar as they are laid in the wall. All units are laid with full face mortar beds, with the head or end joints filled solidly with mortar. The distance from the face of the unit should not be less than the thickness of the longitudinal face. This type of construction can also be reinforced.
Various types of hollow bricks
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5.2.5 Pre cast stone blocks
Stone blocks that are larger than normal bricks are manufactured by using waste stone pieces of various sizes with lean cement concrete, this enables a rationalizes use of locally available materials, saving cement, reducing the thickness of stonewalls and eliminating the use of plasters on internal/external surface. The thickness varies by 4, 6, 8 and 12 inches depending on the design
requirements. Filling the moulds with stones and cementing
5.2.6 Pre cast concrete blocks
These are made of similar dimensions of stone blocks without large size stone pieces, but use coarse and fine graded aggregate with cement. They have excellent
properties as compared to other masonry blocks. Industrial waste like cinders and cut stone pieces can be well utilized.
Load bearings – for load bearing masonry construction, these blocks are suitable for low –rise construction when used with a suitable framed RCC construction they are suitable for high‐rise residential and commercial construction.
5.2.7 Fly ash based lightweight aerated concrete walling and roofing blocks
These are manufactured by a process that involves the mixing of fly ash, quick lime or cement and gypsum, and foaming agents like aluminum powder. These are considered excellent products for walling blocks and prefab floor slabs.
5.2.8 Composite ferro cement system
This is simple to construct and is made of ferro‐cement, i.e rich mortar reinforced with chicken and welded wire mesh. These reduce the wall thickness and allow for a larger carpet area. Precast ferro cement units in a trough shape are integrated with RCC columns.
Ferro cement units serve as a permanent skin unit and as a diagonal strut between columns.
The inside cladding can be done with mud blocks or any locally viable material. The details of the system are given in the figure.
Reference: (1) Sustainable Design Manual ( Volume – 2),
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