Development of Draft Protocol for Testing of Structural Components and Systems
(a joint initiative of MoHUPA under technology submission of Pradhan Mantri Awas Yojna & IIT, KANPUR)
Burnt Clay Fly Ash Building Bricks
Burnt Clay Fly ash bricks are primarily composed of cement, sand, fly ash and water. Such bricks are competitive in comparison to conventional clay bricks and provide enormous indirect benefits such as saving in labor cost and less consumption of mortar. Increase in number of thermal power plants has resulted in severe environmental problems such as fly ash. Dumping of fly ash makes atmosphere unhealthy and also devours fertility of land. To overcome these problems, use of fly ash in conjunction with clay for making building bricks has been suggested by different govt. agencies. Specifications of burnt clay fly ash bricks shall conform to IS 13757: 1993, which are as given below:
- Classification Burnt clay fly ash bricks are classified on basis of average compressive strength as given in Table 1.
- General Quality Bricks should be hand or machine molded and made of admixture of suitable soil and fly ash. Optimum proportion of fly ash should be user as per IS 2117:1991. Fly ash employed for manufacturing of bricks should be of grade 1 or grade 2 as per IS 3812:1981. Bricks should be uniformly burnt, free from cracks and flaws such as nodules of stone, black coring and organic matter. Frog dimensions should same for both modular and non modular size bricks. Frog dimension should be either 10 or 20mm for and hand molded bricks of 90 or 70 mm height. No frog is provided for bricks of height 30 or 40 mm and for bricks made by extrusion process. Smooth rectangular faces with sharp corner should be provided to the bricks along with uniform color and shape.
- Tolerance Randomly select 20 bricks (or more according to the size of the stack) from the selected sample. Arrange these bricks on as level surface successively as depicted in 2A, 2B and 2C. Measure overall length of the assembly with a sufficiently long steel tape or with help of some other inextensible measure. If measurement of bricks in one row is not possible for some reason; sample may be divided into rows of 10 bricks and measurement should be done to the nearest millimeter. For modular size bricks (90mm high) the width and height should be 1800±40mm and length should be 3800±80mm. For 40mm high bricks the height should be 800±40mm, width and length should remain same as for 90mm high bricks. For non modular size bricks (70mm high) the length should be 4600±80mm and width should be 2200±40mm and height should be 1400±40mm. For 30mm high bricks the height should be 600±40mm, length and width should remain same.
- Physical properties Bricks should have minimum compressive strength as mentioned in Table 1 for respective class when tested according to IS 3495 (1): 1992. Water absorption (IS 3495 (2): 1992) of bricks should not be more than 20% by weight up to class 12.5 and 15% for higher classes when bricks are immersed in cold water for 24 hours. Efflorescence (IS 3495 (3): 1992) should not be more than ‘moderate’ for class up to 12.5 and ‘slight’ for higher classes.
- Sampling and criteria for conformity: It should be in accordance with IS 5454: 1978.
Table 1: Classes of burnt clay fly ash bricks(As per IS 13757: 1993)
Dimension of modular bricks should be as follows:
Length(mm)        Width (mm)        Height (mm)
190                        90                     90
190                        90                    40
Non modular bricks of following size may also be used:
230                        110                    70
230                        110                    30
Following sizes of non modular brick may also be used to obtain proper bond agreement and modular dimension for brickwork:
70                        110                    70
230                        50                    70
Figure 1(Source: IS 13757: 1993)
For more details, please refer to IS 13757: 1993.