Building Materials: Stone, Gypsum, Cement, Metals and Wood Explained

Construction Materials: Agglomerants, Stones and Metals

Agglomerant materials are stones, artificial or natural, that have the property of adhering to other materials. Mortars, pastes and concretes are made from these materials. They are molded to shape and finally hardened.

Classification of Agglomerant Materials

Aerial: They harden in air and are not resistant to water (gypsum, metal body, lime).

Hydraulic: They harden in both air and water. Hydrocarbons: lime, cements, Portland cement, hydraulic lime.

Hydrocarbons: These are hydrocarbons like oil or viscous materials that harden by evaporation or cooling (cements, asphalt).

Gypsum Types

Dihydrate gypsum or CaSO4·2H2O (the most abundant).

Hemihydrate gypsum (2CaSO4·H2O).

Anhydrite: CaSO4 (less abundant).

Obtaining Gypsum

Temperature: 140-200 °C, which converts CaSO4·2H2O into (2CaSO4·H2O) or similar.

Gypsum is naturally abundant as dihydrate, so it must be obtained as hemihydrate, which is then used for construction.

Gypsum Manufacturing Process

1. Extraction of gypsum stone: This is done through surface mining or galleries. Preferably, the disposition of the blasting holes is planned, using gunpowder to support fragmentation, reducing flow and making shredding difficult in very plastic material.

2. Crushing: Jaw crushers are used, with two plates placed in a channel: one fixed and the other moving vertically, bent around a fixed joint pin in the upper part.

3. Cooking:

Rustic: Used in practicing soil excavation. The stones are placed in mounds, then stacked in alternating layers.

Industrial processes: Cauldrons and sheet metal. Mechanical, 2 m plate, in which agitators with diameters move, and scrapers. Heat is supplied by combustion of gas, with the compression of petroleum gas on the lateral sides of the parts.

Rotary kilns: These are cement-like cylinders, similar to pipes of large dimensions, about 10 m long and 1.5 m in diameter, used in cooking. The heat is applied by the kiln's burners.

Wrought Iron

Characteristics:

• Wrought: Can be forged or hammered.
• Sweet and ductile: Malleable.
• Puddling: From the English word meaning to stir or shake.
• Wrought iron is a soft, malleable iron with a fibrous structure.
• Its name comes from the fact that it is practically 99% pure iron, with 0.1% carbon.
• Rolling: Can be done hot or cold. It passes through rollers, gradually giving the required profile.

Cold rolled and hot rolled are used to manufacture angles, beams, sheets, plates, etc.

Stretching: Also practiced hot or cold, passing bars through rollers that stretch them longitudinally.

Hot stretching is used in welded and pipe manufacturing. Wire with a diameter of less than 5 mm is also produced.

Forging: Also used to produce parts, shaped by hammering. Hot forging is used for hammer or press work.

Cold forging: Considered punching or drilling with a punch, under pressure, and molded inlays.

Commercial profiles: Angles, T-beams, double T, etc. Also used to manufacture nails, screws, hooks, nuts, wires, etc.

Steel: Malleable iron at a given temperature. It can harden strongly when cooled quickly. The carbon content varies from 0.10% to 1.50%.

Classification of Steel

Steel can be classified by manufacturing method, composition, or carbon content.

By Carbon Content

• Mild steel: 0.10-0.20% carbon
• Medium steel: 0.20-0.40% carbon
• Hard steel: 0.40-0.70% carbon
• Very hard steel: 0.70-1.50% carbon

By Manufacturing Method

Bessemer, Siemens-Martin, electric furnace, duplex, triplex, etc.

Special Alloys

Nickel steel, chromium steel, manganese steel.

Heat Treatment of Steel

Processes: tempering, annealing, cementation, normalizing.

Wood

Wood is one of the oldest and most widely used materials in construction. It is used in the structural framework, as well as in formwork, and has great use as a building material, along with other materials, due to its ability to develop resistant layers.

Classification of Wood

a) Mechanical strength:

1. Very hard woods: 1200-1800 kg/cm² rupture strength. Used varieties include: araguaney, Canaletta, letter wood, cedar, blackberry, pilón, oak, and vera.
2. Semi-hard woods: 600-1000 kg/cm² rupture strength. Principal species include: apamate, mahogany, jabiyo, saman, and PSCAD uses.
3. Hard woods: 1000-1200 kg/cm² rupture strength. Principal species include: angliono, Carrt, Bariya, and orozul.
4. Soft woods: 250-600 kg/cm² rupture strength. Used species include: cedar, balsa, and mijao.

b) Preferred uses:

1. Cabinetry woods: Used for furniture, in construction, and for doors and windows.
   • Fine cabinetry: oak, vera, balsamo, mahogany, barreto, cartan.
   • Ordinary cabinetry: apamate and cedar.
2. Industrial woods: Used to manufacture fiber, paper, etc.
3. Construction woods:
   • Principal use: structural members of buildings such as columns, beams, floors, and roofs. These must be very tough and hard.
   • Used as formwork in construction: shoring and scaffolding that support during the construction period, such as jabiyo, mijao, saman, and saki-saqui.

Wood Characteristics

1. Strength: Affected by specific content, moisture content, and fiber.
2. Durability: Being organic, wood is subject to attack by fungi, insects, etc. It is further affected by environmental conditions and fire.
3. Finishing: Depends on the shape, size, and appearance presented by the wood. It must have good distribution and firm consistency, with suitable dimensions and moisture degree.

Usual Dimensions

• Boards: Thin cross-section. Thickness 2.5 cm - 3 cm, width 20 - 40 cm, length 3-5 m.
• Planks: Similar to boards, with thickness 5 - 10 cm.
• Beams: Cross-sections of 7.5 × 5, 10 × 5, and 10 × 10 cm.
• Sheets: Very thin. Veneers pressed from several wood sheets.

Clays

Clays are sedimentary, disaggregated rocks composed of silicates, alumina, and other minerals, formed by the weathering of feldspar and other atmospheric agents.

Physical Properties of Clays

• Plasticity: Very important. Clay absorbs water to form a cylinder of determined thickness without breaking.
• Strength: Tensile strength, tested in special machines.
• Shrinkage: Important for determining size. Typically between 1 and 10%.
• Fusibility: Indicates the amount of fuel needed to fire a given clay.

Classification of Ceramic Materials

1) Coarse materials:

• Brick: Rectangular or cubic shape, dimensions 25 × 12 × 6.5 cm.
• Panels: Same utility as brick, dimensions 40 × 40 × 4 cm.
• Refractory brick: Made of silica and alumina, resistant to high temperatures up to 1810 °C, dimensions 25 × 12 × 6.5 cm.

2) Fine materials:

• Panels: Used for covering walls and ceilings, dimensions 26 × 26 × 2.5 cm.
• Tiles: Same use, dimensions 20 × 20 × 1 cm.
• Blocks: Used in buildings or concrete structures, providing thermal and acoustic insulation. Dimensions: 20 × 20 × thickness cm.
• Hollow blocks: Used exclusively for filling, allowing easy formwork and reducing costly reinforced concrete work.
• Tejas (roof tiles): Curved in conical shape, about 40 cm long, with one end 20 cm wide and the other 23 cm wide.
• Other ceramic products: Tile, glaze, pipes (bricks, blocks, pipes of various kinds).

Grinding

This operation is performed in any rotary or disintegrating mill. Spinning mills are constituted of two stones, placed horizontally, one above the other, with the upper stone fixed and the lower one mobile.

Lime

Aerial lime: The resultant product of decomposition of limestone.

Classification of lime: Fat lime, lean or dry lime, hydraulic lime.

Cement

Cement is the active component that binds concrete. Its properties and characteristics are influenced by it. Cement is approximately 10 to 20% of the total weight of concrete, while the rest, 80 to 90%, consists of aggregates. Conditions determine the possibility of developing the properties of cements; in practice, the quantity and quality of aggregates are decisive.

Chemical Components of Portland Cement

Components, chemical formulas, abbreviated formulas, and usual composition limits (%).

Metals Used in Construction

Metals used in construction include lead, zinc, copper, and aluminum.

Properties of Metals

• Fusibility: Metals with a low melting point can be processed more easily, becoming liquid and fluid for casting into small molds.
• Forgeability: The ability of a metal to be shaped by hammering, pressing, and rolling without losing cohesion. Some metals cannot be forged easily.
• Malleability: The property of a metal to be altered by ordinary temperature and mechanical actions, such as hammering and rolling. Difficult-to-work metals become brittle in the cold, especially with excess phosphorus.
• Ductility: The property of being drawn into wires or threads. Ductile metals include gold, silver, platinum, aluminum, copper, tin, lead, and zinc.
• Toughness: Resistance to rupture, increased by mechanical treatments, the presence of laminations, and other carbon components, especially in cast metals.
• Hardness: Metals that are very hard are difficult to cut; those that are very soft are easily cut, and lead, for example, is not very hard.
• Weldability: The property that allows two metals to form a single piece when joined.
• Oxidability: Except for noble metals, all metals rust, forming a first layer of oxide or carbonate. If impermeable, this layer protects the metal from further corrosion.

Ferrous Metals (Iron)

Iron, pig iron, and ingots are obtained from mineral ores. Different names are given to iron based on the characteristics of the ores and the impurities they contain. The subsequent processing of these ores produces other ferrous products. The primary ores of iron are:

• Iron ores: Red hematite (Fe2O3), brown hematite, limonite, and magnetite (Fe3O4).
• Iron carbonate (FeCO3).

Blast furnaces: Enormous metal cavities, 20 to 30 m high, lined with refractory bricks. The lower part is simple or strongly constructed, and provides air through tubes called tuyeres, used for combustion.

Cast Iron

Cast iron is produced by casting or founding. It is an alloy with carbon content that is practically variable at any temperature.

Classes of Cast Iron

Gray cast iron: Most of the carbon is precipitated as graphite upon solidification, resulting from the silicon content.

White cast iron: Contains almost all carbon combined in the form of cementite (Fe3C). Due to the high manganese content, it is hard and brittle.

Uses of Cast Iron

The main uses of cast iron are:

• Fumisteria (ovens and chimneys)
• Manufacturing pipes and pieces with medium resistance, as well as high resistance to compression and low resistance to traction.

Mechanical Strength of Cast Iron