What are the standard sizes of fly ash bricks as per IS 12894?

The standard sizes are 190x90x90 mm and 190x90x40 mm. (Clause 5.1.1)

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

The average water absorption should not exceed 20% by mass after 24 hours of cold water immersion. (Table 1)

What are the common compressive strength classes for fly ash bricks?

The code specifies classes based on average compressive strength, with common ones being Class 10 (10 N/mm²), 7.5 (7.5 N/mm²), and 5 (5 N/mm²). (Table 1)

What is the maximum permissible drying shrinkage?

The maximum drying shrinkage for fly ash bricks should not exceed 0.15%. (Table 1)

IS 12894

: 2002

Pulverized Fuel Ash - Lime Bricks - Specification

CurrentFrequently UsedSpecificationBIMMaterials Science · Masonry and Bricks

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This standard specifies the requirements for pulverized fuel ash (fly ash) lime bricks, which are used as an alternative to traditional clay bricks. It covers the classification, material composition, dimensions, and physical properties like compressive strength, water absorption, and drying shrinkage. The code also outlines the sampling and testing methods to ensure the quality and performance of these bricks in masonry construction.

Specifies requirements for pulverized fuel ash-lime bricks (fly ash bricks) used in masonry construction.

Quick Reference Values

Standard brick size190 x 90 x 90 mm

Minimum avg compressive strength for Class 10 brick10.0 N/mm²

Minimum avg compressive strength for Class 7.5 brick7.5 N/mm²

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

Maximum drying shrinkage0.15%

Maximum efflorescence ratingSlight

Practical Notes

Fly ash bricks have very uniform shapes, which allows for thinner mortar joints and reduced plaster thickness.

Unlike clay bricks, fly ash bricks generally do not require soaking before use, but just light wetting of the surface is sufficient to prevent rapid moisture loss from mortar.

Always insist on a Manufacturer's Test Certificate for each batch to verify compliance with the specified strength class (e.g., Class 7.5, 10) as strength cannot be judged visually.