This part of IS 1121 prescribes the standard testing method for determining the compressive strength of natural building stones. It guides material engineers on sample preparation, conditioning, and loading to evaluate the load-bearing capacity of stone used in masonry and civil construction.
Prescribes the method for determining the compressive strength of natural building stones.
Quick Reference Values
specimen dimensions50 mm cubes or cylinders 50 mm diameter x 50 mm height
loading rate14 N/mm² per minute
dry conditioning temp105 ± 5°C
dry conditioning time24 hours
water immersion time72 hours at 20 to 30°C
bearing surface tolerance0.025 mm
Key Formulas
C = W / A — Compressive Strength (where W is crushing load in N, A is area of bearing surface in mm²)
Practical Notes
Stones are highly anisotropic; ensure you test and report strengths both parallel and perpendicular to the bedding planes or rift.
The bearing surfaces of the specimens must be strictly flat and parallel to ensure uniform stress distribution; capping with plaster of Paris may be required if perfectly smooth surfaces cannot be achieved.
Moisture severely affects the strength of natural stone; tests are typically conducted in both completely dry and saturated conditions.