Cement Overview and History

Cement Overview

• Cement is a crystalline compound of calcium silicates and other calcium compounds with hydraulic properties.

Cement History

• Lime and clay have been used as cementing materials for centuries.
• Romans are credited with developing hydraulic cement, a significant advancement in construction.
• Roman cement involved mixing volcanic ash from Mt. Vesuvius with lime.
• The Pantheon in Rome is a notable surviving example of Roman construction.
• Joseph Aspdin, from England, invented Portland cement in 1824.

Cement Types

• Cements are considered hydraulic due to their ability to harden with water through chemical hydration.
• Two main types:
  • Pozzolanic cement: This type uses siliceous materials that develop hydraulic properties when mixed with hydrated lime.
  • Hydraulic lime: Used in specialized mortars, made from calcined clay-rich limestones.
  • Natural cement: Commonly known as Roman cement, made from argillaceous limestone or interbedded limestone and clay/shale. Natural cement is largely less common due to poor quality compared with Portland cement.

Portland Cement

• An artificial cement made by mixing clinker with gypsum in a 95:5 ratio.
• Portland-limestone cements: Include significant amounts of ground limestone as a filler (6% to 35%) in Portland cement.
• Blended cements: Mix of Portland cement with one or more supplementary cementitious materials (SCM) such as pozzolanic additives.
• Pozzolan-lime cements: These were original Roman cements, and modern versions are a mix of pozzolans with lime.
• Masonry cements: Portland cement where additional materials are added to improve plasticity (moldability).
• Aluminous cements: Made primarily from limestone, bauxite, and used in refractory applications or where fast hardening is essential.

Raw Materials for Cement Production

• Limestone, marl, chalk, and other calcium carbonate sources.
• Clay, shale, sand, iron ore, and volcanic ash are argillaceous materials.
• Fly ash and industrial byproducts like bottom ash/metallurgical slags can be substitutes for some materials.
• The essential chemical compounds are lime (CaO), silica (SiO2), alumina (Al2O3), and iron oxide (Fe2O3).

Cement Clinker Compounds

• Tricalcium silicate (C3S): Key component, high early strength.
• Dicalcium silicate (C2S): Significant component, high long-term strength.
• Tricalcium aluminate (C3A): Affects setting and heat generation, needs careful control.
• Tetracalcium aluminoferrite (C4AF): Influences clinker properties and setting behavior.

Cement Uses

• Cement is primarily used as a binder in the production of concrete and mortar.
• Modern use cases include building construction (floors, beams, columns, etc.), transport infrastructure, water management projects, civil engineering structures and agriculture.

Cement Production

• World production numbers and clinker capacity are substantial.

Cement Substitutes

• Some alternatives to cement include asphalt, clay bricks, fibreglass, and stone.
• Byproducts like fly ash can be partial cement substitutes.

Cement Resources

• While individual reserves may deplete, cement raw materials are widespread and generally abundant.

Mining Methods

• Limestone commonly extracted through bench mining with blasting.
• Haul trucks are used for transportation of extracted materials.

Cement Processing

• Cement processing involves several stages:
  • Quarrying and blending of raw materials.
  • Proportioning and fine grinding of materials.
  • Kiln system for preheating, cooling, and clinker storage.
  • Finishing grinding and cement shipping

Marketing Considerations

• Effective marketing involves efficient distribution to minimize costs for consumers.
• Key factors are delivered cost, quality, consistency, technical assistance and sales relationship with the user companies.
• Key drivers in the market are economic growth, private and governmental capital investment, and population growth.