Building Stones: Properties, Types, and Construction Uses
Stone Properties and Applications
This document outlines key characteristics and applications of various stone types in construction.
Rock Durability
A crucial feature of stone is its durability, defined as the ability to withstand weathering without altering its physical and aesthetic properties. A durable rock resists external forces without changing its appearance or structure, ensuring a long effective lifespan for the material in use. It maintains cohesion even when saturated with water.
Key Rock Properties
- Density
- Porosity
- Durability
The Geological Rock Cycle
The geological cycle describes the transformation of rocks:
Magma → Solidification → Igneous Rock → Erosion → Sedimentary Rock → Metamorphism → Metamorphic Rock
Rock Classification
Igneous Rocks (Magmatic)
These rocks originate from the solidification of magma (hard rock). There are three main types:
- Plutonic Rocks: Formed from slow cooling deep within the Earth (e.g., granite).
- Volcanic Rocks: Result from rapid cooling on the Earth’s surface (e.g., pumice).
- Hypabyssal (Philonian) Rocks: Formed when cooling magma is trapped at mid-depth in holes and crevices (e.g., porphyry).
Sedimentary Rocks
Sedimentary rocks are formed from the weathering of existing rocks. Weathering is the alteration caused by external geological and atmospheric agents, leading to the disintegration and breakdown of rock.
Classification by Grain Cohesion
- Loose/Disintegrated: Grains lack sufficient cohesion (e.g., sand, clay, dust).
- Compact: Grains are cemented together.
Metamorphic Rocks
These rocks arise from the metamorphism that takes place within the Earth’s lithosphere.
Stone Processing and Finishes
Stone processing involves various methods, including cutting, grinding, sawing, carving, polishing, and curing.
There are different types of finishes:
- Smooth Finishes: Sawed, honed, polished, bush-hammered, flamed.
- Rough Finishes: Escafilado, acid-washed.
Applications of Natural Stone
Natural rocks are widely used in construction for masonry, paving, roofing, and cladding.
Masonry and Stonework
Stones are utilized as masonry units, ashlar, or rubble stone.
- Requirements: Hardness, adhesion to mortar, frost-resistance, compressive strength > 500 kg/cm², and resistance to atmospheric agents.
- Types of Materials: Limestone, compact tuff, sandstone, granite, silica.
Flooring
Applications include slabs, tiles, steps, curbs, and paving.
- Requirements: Slip resistance, low porosity, fine grain, high resistance to abrasion, bending strength, and resistance to acids and weathering.
Key properties for flooring materials:
- Porosity
- Durability
- Frost Resistance
- Slip Resistance
Types of Materials: Granite, marble, slate, and siliceous basalts.
Roofing (Covers)
Used as slabs or plates of reduced thickness and moderate size.
- Requirements: Low density, impermeability, high resistance to bending, and resistance to weathering.
- Types of Materials: Slate (known for good bending strength, lightweight, waterproof, high chemical resistance, and good workability). Slate is derived from the metamorphism of clays, hence its impermeability.
Cladding
Involves thin slabs cut into square, rectangular, or polygonal shapes.
- Requirements: Waterproof, frost-resistant, low thermal conductivity, impact resistance, and resistance to weathering.
- Types of Materials: Any suitable stone.
- Placement: Anchored to the wall.
Cladding Challenges and Solutions
Problems:
- Degradation from salts.
- Surface water absorption and subsequent freezing.
- Issues with thin-set mortars or fluid applications for the plates, increasing risk of impact damage.
Solutions:
- Use minimum thickness appropriate for the rock type.
- Avoid direct contact with soil.
- Use very dry mortars with low workability.
- Allow for proper water evaporation.