Hollow Clay-Flyash Block

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Process for making glazed as well as unglazed hollow blocks using clay and flyash.


In building industry.

Salient Features of Process/Technology

These blocks have nearly 36% hollow area thus reducing clay and fuel requirement. They possess excellent strength and durability. Clay and flyash are mixed with requisite water and extruded in de-airing pug mill. Desired shape is provided through the extruder. The green blocks are dried and fired. For glazing, the fired blocks are provided with a surface spray, dried and fired again. A block of 22.5x10x10 cm weighs 2.0-2.2 kg. The block possesses bulk density: 1.9 g/cm3, water absorption: 17%, compressive strength horizontal: 140 and vertical: 180 kg/cm2. The hollow blocks reduce masonry dead load, eliminate plastering and provide thermal & acoustic comfort.




Minimum Economic Unit Size

100 blocks/day

Indicative investment

Rs. 10 lakh

Equipment and Machinery

Mixer, de-airing pug mill, extruder, kiln, glazing unit.


Raw materials

Clay, flyash



For further information please contact

The Director.
Central Building Research Institute, New Delhi