Construction Materials: Stone, Ceramics, Glass & More

Posted on Nov 3, 2024 in Geology

Stone Materials

Rocks

Rocks are natural aggregates of minerals found in the Earth’s crust. They have very little tensile strength but high compressive strength. The most commonly used rocks in construction include:

  1. Granite: Historically used for construction, today it’s primarily used as gravel in concrete.
  2. Gabbro and Diorite: Used for paving roads.
  3. Liparite and Pumice: Used to prepare lightweight aggregates.
  4. Sandstone: Cemented sand used for building and paving.

Other Stone Materials

  • Calcite: Consisting of calcium carbonate.
  • Slate: Used for building coverage.
  • Marble: Consisting of calcium carbonate and easily polished, used in buildings.

Granular materials are used for the manufacture of mortars and concretes.

Ceramics

Ceramics are materials made of clay, which are hydrated aluminum silicates. They are chemically inert and resistant to high temperatures. Ceramic materials can be:

  1. Porous: These have an earthy appearance and are permeable to gases, liquids, and fats. This group includes fired clay, earthenware, and refractory materials.
  2. Waterproof: These materials are harder than porous ceramics. This group includes stoneware and porcelain.

Baked Clay

Baked clay contains a considerable amount of iron oxide. Once modeled, it’s dried and subsequently undergoes a firing process.

China

China is a ceramic material that, once shaped and fired, is covered with lacquer or enamel and subjected to a second firing. It is classified as:

  1. Earthenware: Cooked earthenware with a clear lacquer coating on its surface.
  2. Common Earthenware: Similar to the above.
  3. Fine Earthenware: Has a transparent cover and the paste contains silica, which gives it hardness.
  4. Construction Earthenware: Includes glazed bricks, tiles, and sanitary ware.

Refractory Materials

Refractory materials are clay fired at high temperatures, with subsequent slow cooling to prevent cracks and internal stresses. They are used as refractory bricks and in the manufacture of engines.

Porcelain

Porcelain is obtained by subjecting a material to a double firing with the addition of feldspar. It can be classified as soft or hard porcelain.

Stoneware

Stoneware is a vitrified ceramic material consisting of a paste made of plastic clay and quartz sand. It is used to make objects that are rugged, porous, and refractory.

Glass

Glass is an amorphous, transparent, hard, and brittle material at room temperature. It is resistant to most chemical reagents and has high tensile strength. It is obtained by the fusion of:

  1. Quartz Sand: The main component of glass, providing mechanical strength.
  2. Limestone: Acts as a stabilizer.
  3. Soda: Acts as a flux.

Components such as oxides of sodium, potassium, aluminum, boron, and lead are usually added.

Variety of Glass

  1. Flat Glass: Consisting of soda, quartz, and limestone. Used for windows, mirrors, and tables. It is manufactured using the floatation method.
  2. Hollow Glass: Made of quartz, soda, and lime. Used to make bottles, glasses, jars, etc. It is manufactured through a blowing process, which can be handcrafted or automated. In the handcrafted method, a hollow tube is introduced inside the glass, and it is blown to achieve the desired shape. In the automated method, the glass adapts to the walls of a mold, which then opens to extract the produced part.
  3. Cast Glass: Presented in the form of sheets of different thicknesses and surfaces with different textures. Obtained by casting and rolling methods. The glass is cast in a container and then passed through an iron roller to give it shape.
  4. Pressed Glass: Manufactured by pouring molten glass into a metal mold and then compressing it with a plunger. Used for thick-walled objects, bricks, tiles, etc.
  5. Fiberglass: Made by passing the glass through a die with small holes. Used to manufacture insulating fabrics in roofing, fiber optics for telecommunications and medicine.

Derivatives of Glass

  • Window Glass: Obtained from flat glass, manufactured in different thicknesses. It is transparent to visible light, provides good acoustic insulation, and is highly resistant to atmospheric agents.
  • Wired Glass: Cast glass with a wire mesh introduced during the rolling process.
  • Safety Glass: Flat glass that can consist of one or more layers. Single-layer safety glass is tempered by heating it to about 600°C and then subjecting it to rapid cooling. It is used in tables, doors, porches, balconies, stairs, etc. Multi-layer safety glass has two or more glass layers bonded together with a transparent synthetic material. It is used in windows of jewelry stores, financial institutions, and automobiles.
  • Anti-reflective Glass: Flat glass with a hard and tough coating on its faces that prevents light reflection. It has the same transparency as window glass and is used for tables, cabinets, and showcases.

Agglomerating Materials

These materials have the property to set and harden, allowing them to be used to bind together heterogeneous materials in construction.

Air Binders

These binders do not contain clay and set and harden only upon contact with air. Examples include gypsum and lime.

Hydraulic Binders

These binders contain a considerable amount of clay. Their hardening takes place both in air and in water. Examples include hydraulic lime, pozzolans, and cement.

Gypsum

Gypsum is a mineral that occurs naturally in large compact granular masses. It is extracted from quarries and then cooked. Cooking methods include:

  1. Traditional Procedure: Using wood as fuel, resulting in a grayish material.
  2. Kilns: Filled from the top and emptied from the bottom, producing higher quality gypsum.
  3. Rotary Kilns: The most modern method, allowing for uniform dehydration.

In Spain, gypsum is classified into three categories:

  1. Yesonegro: Used for plaster and unseen plaster works.
  2. Yesoblando: More pure than Yesonegro, used for plaster and stucco walls.
  3. Plaster: High quality, used for trimming and interior finishes.

Gypsum is mixed with water to form a paste or mortar. The lower the proportion of water, the greater the hardness and setting speed. The main disadvantages of gypsum are its low strength and high sensitivity to moisture. It is used for pillars, walls, partitions, plaster, flooring, ceilings, etc.

Air Lime

Air lime, also known as quicklime, comes from the calcination of limestone at 900°C. Slaked lime is hydrated lime. Slaked lime in paste hardens slowly in the air, losing water first and then reacting with CO2.

Hydraulic Lime

Hydraulic lime comes from limestone with clay. It is used in plastering walls, stucco, and coatings.

Pozzolans

Pozzolans are siliceous substances that are reduced to powder and mixed with lime to create hydraulic binders. There are two types:

  • Natural: Must be milled before use.
  • Artificial: Formed by heating clays and shales, rapidly cooling them, and subjecting them to spraying.

Cement

Cement is a powdery material that is mixed with water to form a paste that sets and hardens in the air. The most important type is Portland cement. Its manufacturing process consists of:

  1. Preparation of Raw Materials: Raw materials are crushed and milled.
  2. Calcination: Takes place in a rotary kiln using pulverized coal as fuel, resulting in clinker (hard grains of 3-20 mm in diameter). The clinker is then cooled and stored.
  3. Milling: The clinker is ground with water and stored in silos, then packaged in bags.

Cement is used as a binder in construction, in the form of mortar and concrete.

Cement Mortar

Composed of cement, sand, and water.

Concrete

A mixture of cement, sand, gravel, and water. The amount of cement per cubic meter of concrete determines its mechanical strength and water resistance. Too much cement can cause cracks, so it should not exceed 460 kg/m3. The aggregates impact the concrete’s tensile strength. Additives can be used to improve or modify its properties, such as accelerators, plasticizers, and air-entraining agents. The main drawback of concrete is its low tensile strength, so it is primarily used in structures designed to withstand compressive loads.

Reinforced Concrete

Obtained by adding a framework of steel rods to concrete before it sets. The steel absorbs tensile stresses. Steel is used because its expansion coefficient is equal to that of concrete. The concrete adheres to the steel through friction. The main advantage of reinforced concrete is its adaptability to different forms.

Prestressed Concrete

Reinforced concrete where the steel rods are tensioned before the concrete sets. Once hardened, the steel tries to recover its original length, putting the concrete under compression and improving its resistance to tensile stresses.

Manufactured Products

  • Artificial Stone: Consists of pieces of natural stone bound together with concrete. It is easier to mold and cheaper than natural stone.
  • Bricks: Made by binding slag cement produced in blast furnaces and electric furnaces.

Reinforced Materials

  • Fiber-Reinforced Cement: Asbestos fibers enable cement to withstand tensile and bending stresses.
  • Fiberglass-Reinforced Cement: Provides good insulation against heat and fire resistance.
  • Carbon-Reinforced Concrete: Adding 0.5% carbon increases strength and can create materials that act as sensors.