Boiling test for Sonnenbrand signs on basalts

The test is conducted for the determination of Sonnenbrand and is used to test basalt aggregate. 

The test is conducted according to CEN EN 1367-3 (2004) and applies to pieces of rock and graded coarse aggregate. 

The Sonnenbrand effect starts with the appearance of grey/white star-shaped spots. Hairline cracks are then usually generated. They reduce the strength of the minerals and the rock decays into smaller particles. 

The required amount of basalt particles is placed in a steel can containing water, which is boiled for 36 1 h. Sonnenbrand signs, as well as the development of cracks and possible cracking of aggregate particles, are visually determined. The mass loss after boiling, as well as the loss of resistance to strength after boiling, is determined. 

The loss of mass (Mi) is determined as a percentage by weight of the initial sample after sieving through a sieve having an aperture of half the lower nominal size. 

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