What is the minimum percentage of fly ash required in these bricks?

At least 25 percent by mass (Clause 3.1).

What is the maximum water absorption allowed for fly ash bricks?

Not more than 20 percent by mass after 24-hour immersion in cold water (Clause 6.2 and Table 3).

What are the common compressive strength classes available?

The standard provides classes from 5 to 35, with common classes for general construction being 7.5, 10, and 12.5 (in N/mm²) (Table 1).

What are the standard modular dimensions for these bricks?

190 mm x 90 mm x 90 mm and 190 mm x 90 mm x 40 mm (Clause 4.1).

IS 13757

: 1993

Burnt clay fly ash building bricks-Specification

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This standard specifies the requirements for dimensions, classification, physical properties, and testing of burnt clay bricks containing at least 25% fly ash. It covers crucial quality aspects like compressive strength, water absorption, and efflorescence for bricks used in masonry construction.

Burnt clay fly ash building bricks-Specification

Quick Reference Values

Minimum fly ash content25% by mass

Maximum water absorption (24-hr cold soak)20% by mass

Minimum average compressive strength (Class 7.5)7.5 N/mm²

Efflorescence rating limitModerate

Standard non-modular brick size230 x 110 x 70 mm

Standard modular brick size190 x 90 x 90 mm

Practical Notes

The use of fly ash is an environmentally friendly way to utilize industrial waste, often resulting in bricks with better finish and lower water absorption than traditional clay bricks.

Always verify test certificates from the manufacturer for compressive strength and water absorption, as quality can vary significantly.

For exposed brickwork, it is advisable to specify and select bricks with a 'Slight' or 'Nil' efflorescence rating, even though the standard permits 'Moderate'.