Rock Classifications and Brick Technical Standards
Classification of Geological Rocks
Igneous (Eruptive) Rocks
- Plutonic: Granite
- Volcanic: Rhyolite and Basalt
Sedimentary Rocks
Mechanical Sedimentary Rocks
- Disintegrated Rocks
- Compact Rocks: Sandstones
Chemical Precipitation Rocks
Examples include gypsum, limestone, marl, and dolomite.
Metamorphic Rocks
Common types include gneiss, slate, quartzite, and marble.
Technical Specifications for Bricks
Average Value and Dimensional Deviation
We determine the deviation from the nominal value stated by the manufacturer. Depending on the degree of deviation, bricks are classified into different levels: T1, T1 + T2, and T2+ (accurate to the specified deviation).
Range (Route)
The Range is the difference between the largest and the smallest dimension of an individual piece within a travel sample. It is classified as R1, R1 + R2, or R2+.
Water Absorption Test
To measure absorption, 10 pieces are taken and dried at 105°C ± 5°C until they reach a constant mass (no weight variation). They are then submerged in water for 24 hours.
- md: Mass of dry pieces
- mw: Mass of wet pieces after 24 hours
- Formula: Wm = % ((mw - md) / md) x 100
Durability and Frost Resistance
According to the UNE 771 classification, exposure levels are defined as:
- F0 (Passive): Will never be subjected to frost.
- F1 (Moderate): Moderate exposure to frost.
- F2 (Severe): Severe exposure to frost.
Testing Procedure
Part 1: Twelve brick halves are wetted and subjected to 25 freeze-thaw cycles. They are examined visually for defects. If any part is faulty, it is assigned as frost-susceptible (heladizo).
Part 2: A compression test is performed on the 12 tested halves and compared against 12 stored halves. If the difference is less than 30%, they are considered non-frost-susceptible.
Efflorescence and Surface Staining
Efflorescence is a surface stain caused by soluble salts (from the land, mortar, or the brick itself), which presents an aesthetic problem.
Testing and Classification
Seven pieces are used: 6 are tested and 1 is kept as a pattern. The pieces are partially submerged, and evaporation is forced through the side face for 7 days. Visual examination determines the intensity of staining (thin veils, thick veils, or stains) and the affected area (< 5%, 5-25%, or > 25%).
There are 4 classifications: not efflorescing, slightly efflorescing, efflorescing, and very efflorescing.
Flaking and Spalling
Flaking is a surface detachment caused by calcium oxide. When it reacts with water, it increases in volume. While it does not necessarily affect structural resistance, peeling is considered significant if it reaches an average size of 7 cm.