How is concavity measured on a brick?

By placing a straight edge along the surface of the brick and measuring the maximum gap between the straight edge and the brick using a measuring rule or wedge.

How is convexity measured?

By placing the brick face-down on a perfectly flat surface and measuring the maximum gap between the flat surface and the edges/corners of the brick.

What is the graduation requirement for the measuring rule?

The steel measuring rule or wedge should be graduated in 1 mm divisions.

IS 3495 Part 4

: 1992

Methods of Tests of Burnt Clay Building Bricks: Part 4 Determination of warpage

CurrentFrequently UsedTesting MethodMaterials Science · Masonry and Bricks

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This Indian Standard (Part 4) specifies the testing method for determining the warpage (concavity and convexity) of burnt clay building bricks. It provides the procedure to ensure bricks possess the dimensional uniformity required for optimal mortar joint thickness and structural stability.

Specifies the procedure for determining the warpage of burnt clay building bricks.

Quick Reference Values

sample size10 bricks

straight edge lengthAt least 300 mm

measuring rule graduation1 mm

Practical Notes

Always ensure the reference flat surface used for convexity testing is perfectly level, typically a smooth glass plate or a machined steel plate.

Measurements must be taken at the point of maximum deviation to accurately report the highest warpage.

Excessive warpage leads to thicker mortar joints, which negatively impacts the overall compressive strength of the masonry.