Dear
First class bricks should be burnt thoroughly without being vitrified and have deep red, cherry and copper color. Regular and uniform in shape and size with sharp and square edges and parallel faces. Must be homogeneous in texture and emit a clear ringing sound on being struck together. Free from flaws, cracks, chops, stones and lime. Should not absorb water more than 20% of its own dry weight after 24 hours, immersion in cold water.
Have a minimum crushing strength of 105 kg per sq. cm when tested according to the test.
The crusing strength of brick can be tested in Presuure test machine,before testing the frog in the brick should be filed with cement coarse sand mortar 1:2 and then after curing, the brick shall be tested in crushing strength test machine.Link for specification of brick is given below.
http://www.gharexpert.com/articles/Bricks-947/Bricks-Quality_0.aspx
K
In my view fly ash bricks are generally used for making curtain and partition walls of the houses/ buildings. Fly ash bricks are used in domestic building in the category of low or middle-income groups mostly have single or two storied dwelling units. Use of fly ash bricks in this type of construction is meant mainly to achieve economy and make profits. PWD-DELHI Issues Circular for Use of Fly ash Brick“The PWD-DELHI department Suggested Experimental Use of Fly ash bricks in Site office, Temporary Accommodation/ Boundary walls”