History and Development of Portland Cement
– Portland cement developed from natural cements made in Britain in the 18th century
– Named after Portland stone, a building stone quarried in Dorset, England
– John Smeaton experimented with different limestones and additives for construction
– Roman cement was popular but replaced by portland cement in the 1850s
– James Frost and Edgar Dobbs made advancements in cement production
Composition and Manufacturing of Portland Cement
– Portland cement is a hydraulic cement that hardens and forms a water-resistant product
– Consists of hydraulic calcium silicates, calcium sulfate, and other compounds
– Clinkers make up over 90% of the cement, along with minor constituents
– High temperatures cause chemical reactions to form key components of portland cement
– Calcium oxide and belite combine to form alite
– Portland cement clinker is made by heating a mixture of raw materials in a cement kiln
– Fusion temperature of about 1,450°C is required to sinter the materials into clinker
– Alite, belite, tricalcium aluminate, and tetracalcium alumino ferrite are the main components of clinker
– Aluminium, iron, and magnesium oxides act as a flux and contribute little to strength
– Limestone and clay are the primary raw materials used in clinker-making
Types and Uses of Portland Cement
– Ordinary portland cement (OPC) is the most common type of portland cement
– White portland cement is also available
– OPC is grey and named after its resemblance to portland stone
– Different types of portland cement have specific characteristics and uses
– Various standards regulate the composition and properties of portland cement
– Portland cement is a basic ingredient in concrete, mortar, stucco, and grout
– It is widely used in construction due to its low cost and availability
– Concrete, made with portland cement, is a composite material consisting of aggregate, cement, and water
– It provides strength, durability, and versatility to various construction projects
– Portland cement is essential for the development of modern infrastructure.
Cement Grinding, Setting, and Hardening
– A 10 MW cement mill produces cement at 270 tonnes per hour
– Calcium sulfate (usually gypsum or anhydrite) is added to the clinker to achieve desired setting qualities
– The grinding process in a cement mill produces a powder with a broad particle size range
– The specific surface area is used to measure the fineness of the cement
– Cement is stored in silos for one to 20 weeks of production
– Cement sets through a complex series of chemical reactions
– The interlocking of crystals gives cement its strength
– Carbon dioxide is absorbed to convert portlandite into calcium carbonate
– Warm water immersion speeds up the setting process
– Gypsum is added to prevent quick setting
Environmental Impact and Innovation in Cement Manufacturing
– Wet cement is caustic and can cause skin burns
– Cement dust can cause severe eye or respiratory irritation
– Chromium(VI) levels are regulated in some countries
– Cement production has environmental impacts like dust emissions and CO2 release
– Research is ongoing for suitable replacements for Portland cement
– Decarbonation of limestone and kiln fuel combustion are major sources of CO2 emissions in cement manufacturing
– Cement kilns can be used for waste disposal or processing
– Concrete emits less CO2 compared to other modern building systems
– Innovation focuses on reducing CO2 emissions and adopting more efficient processes
– Worker exposure to dust and particulates is a concern in cement manufacturing
– Cement kilns efficiently destroy hazardous organic compounds in waste streams
– The use of supplementary cementitious materials can contribute to a more sustainable cement industry.
This article is about the building product of cement. For the Australian heritage-listed production site, see Portland Cement Works Precinct.
Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th century by Joseph Aspdin, and is usually made from limestone. It is a fine powder, produced by heating limestone and clay minerals in a kiln to form clinker, grinding the clinker, and adding 2 to 3 percent of gypsum. Several types of portland cement are available. The most common, called ordinary portland cement (OPC), is grey, but white portland cement is also available. Its name is derived from its resemblance to portland stone which was quarried on the Isle of Portland in Dorset, England. It was named by Joseph Aspdin who obtained a patent for it in 1824. His son William Aspdin is regarded as the inventor of "modern" portland cement due to his developments in the 1840s. The term portland in this context refers to a material or process, not a proper noun like a place or a person, and should not be capitalized.
Bags of portland cement wrapped and stacked on a pallet.Blue Circle Southern Cement works near Berrima, New South Wales, Australia.
The low cost and widespread availability of the limestone, shales, and other naturally occurring materials used in portland cement make it a relatively cheap building material. Its most common use is in the production of concrete, a composite material consisting of aggregate (gravel and sand), cement, and water.
Definition and Composition of Concrete
- Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures over time.
- It is the second-most-used substance in the world after water.
- Concrete is the most widely used building material.
- Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined.
- When aggregate is mixed with dry Portland cement and water, the mixture forms a fluid slurry that is easily poured and molded into shape.
Hydration Process, Additives, and Reinforced Concrete
- The cement reacts with the water through a process called concrete hydration that hardens it over several hours.
- The hydration process is exothermic, meaning ambient temperature affects the setting time of concrete.
- Additives like pozzolans or superplasticizers are included to improve the physical properties of the wet mix.
- Additives can also delay or accelerate the curing time of concrete.
- The finished material can be modified by adding additives to change its properties.
- Most concrete is poured with reinforcing materials, such as steel rebar, embedded to provide tensile strength.
- Reinforced concrete is a combination of concrete and reinforcement materials.
- The addition of reinforcement allows concrete to withstand tensile forces.
- Reinforced concrete is widely used in construction due to its strength and durability.
- It is commonly used in structures like bridges, buildings, and infrastructure.
Types of Concrete and Historical Significance
- Lime-based cement binders, such as lime putty, were used in the past.
- Portland cement concrete is a common type of concrete that uses Portland cement as a binder.
- Non-cementitious types of concrete exist, such as asphalt concrete with a bitumen binder.
- Polymer concretes use polymers as a binder.
- Concrete is distinct from mortar, which is a bonding agent used to hold masonry units together.
- Concrete floors were found in ancient structures like the royal palace of Tiryns, Greece.
- The Assyrian Jerwan Aqueduct (688 BC) made use of waterproof concrete.
- Mayan concrete at the ruins of Uxmal (850-925 A.D.) is referenced in historical accounts.
- The Nabateans pioneered small-scale production of concrete-like materials.
- The Romans extensively used concrete from 300 BCE to 476 CE, revolutionizing architecture.
Cement, Water, Aggregates, and Admixtures
- Portland cement is the most common type of cement, patented by Joseph Aspdin in 1824.
- Cement consists of calcium silicates, aluminates, and ferrites.
- Water combines with cementitious material to form a cement paste.
- Lower water-to-cement ratio yields stronger, more durable concrete.
- Impure water can cause problems in concrete setting and structure failure.
- Fine and coarse aggregates make up the bulk of a concrete mixture.
- Sand, natural gravel, and crushed stone are commonly used aggregates.
- Recycled aggregates from construction, demolition, and excavation waste are increasingly used.
- Admixtures are materials added to concrete to give it certain characteristics.
- Common admixtures include retarders, accelerators, air entraining agents, and bonding agents.
Use of Alternative Materials, Concrete Enhancements, and Production
- Alternative materials can lower costs, improve concrete properties, and recycle wastes.
- Limestone, fly ash, blast furnace slag, and other materials are being tested and used.
- These developments aim to minimize the impacts of cement use on greenhouse gas emissions.
- Alternative materials contribute to circular economy aspects of the construction industry.
- Crystalline admixtures, pigments, plasticizers, superplasticizers, and retarders are used to enhance concrete.
- Concrete production is the process of mixing water, aggregate, cement, and additives to produce concrete.
- Concrete production takes place in concrete plants, either ready mix plants or central mix plants.
- Design mix ratios, mixing techniques, and curing methods are important factors in concrete production.
Types of Concrete Mixes
- Mix design depends on project requirements, strength, appearance, and local regulations.
- Factors considered include cost of additives and aggregates, slump for mixing and placement, and performance.
- Mix design includes cement, coarse and fine aggregates, water, and chemical admixtures, with specified mixing method and conditions.
- Ingredients vary based on the application, with pre-mixed options available.
- A typical concrete batch includes Portland cement, dry sand, dry stone, and water.
- High-strength concrete has a compressive strength greater than 40 MPa (6000 psi).
- Stamped concrete is an architectural concrete with a superior surface finish.
- High-performance concrete (HPC) exceeds common application standards, not limited to strength.
- Ultra-high-performance concrete (UHPC) has compressive strengths exceeding 150 MPa, possibly exceeding 250 MPa.
- Micro-reinforced UHPC utilizes continuous, multi-layered, three-dimensional micro-steel mesh.
- Low-density structural concrete uses ceramic aggregates with a density below that of water.
- Self-consolidating concrete is cohesive and flowable without mechanical compaction.
- Vacuum concrete is produced by creating a vacuum inside a concrete mixing truck using steam.
- Shotcrete uses compressed air to shoot concrete onto or into a frame or structure.
- Limecrete utilizes lime as a binder instead of Portland cement.
- Glass concrete incorporates recycled glass as aggregate.
- Asphalt concrete uses bituminous materials as the binder.
- Rapid strength concrete develops high resistance within a few hours.
- Rubberized concrete incorporates rubber for improved durability and flexibility.
- Nanoconcrete contains Portland cement particles no greater than 100 μm.
- Foam concrete is a lightweight and highly insulating material.
- Air-entrained concrete incorporates tiny air bubbles for enhanced workability and durability.
- Engineered cementitious composite is a bendable concrete with enhanced flexibility.
- Ferrocement is a reinforced mortar or plaster system with high strength and durability.
- Ready-mix concrete is manufactured in batch plants according to engineered mix design.
Historic Concrete Composition
- Ancient concrete, like Roman concrete, used volcanic ash and hydrated lime.
- Roman concrete was superior to other recipes and they also invented hydraulic concrete.
- Composition stone and artificial stone are terms used for lime-cemented concretes.
- The term 'artificial stone' encompasses various human-made stones, including cemented concretes.
High-Strength Concrete
- High-strength concrete has a compressive strength greater than 40 MPa (6000 psi).
- In the UK, high-strength concrete is defined as having a compressive strength class higher than C50/60.
- Low water-cement ratio (W/C) and silica fume are used to achieve high strength.
- Superplasticizers are added to compensate for reduced workability.
- Careful selection of aggregate is crucial to prevent failure in high-strength concrete.
Stamped Concrete and High-Performance Concrete
- Stamped concrete is an architectural concrete with a superior surface finish.
- High-performance concrete (HPC) exceeds common application standards, not limited to strength.
- HPC can be self-consolidating and compact without segregation.
- HPC exhibits early age strength, long-term mechanical properties, and low permeability.
- Other properties include density, heat of hydration, toughness, volume stability, and durability in severe environments.
- HPC develops a strength greater than 50 MPa (7,300 psi) at specified days and requires well-graded aggregates, cement, fly ash, water-reducing admixtures, and silica fume.
Other Concrete Types
- Ultra-high-performance concrete (UHPC) has compressive strengths exceeding 150 MPa, possibly exceeding 250 MPa.
- Micro-reinforced UHPC utilizes continuous, multi-layered, three-dimensional micro-steel mesh.
- Low-density structural concrete uses ceramic aggregates with a density below that of water.
- Self-consolidating concrete is cohesive and flowable without mechanical compaction.
- Vacuum concrete is produced by creating a vacuum inside a concrete mixing truck using steam.
- Shotcrete uses compressed air to shoot concrete onto or into a frame or structure.
- Limecrete utilizes lime as a binder instead of Portland cement.
- Glass concrete incorporates recycled glass as aggregate.
- Asphalt concrete uses bituminous materials as the binder.
- Rapid strength concrete develops high resistance within a few hours.
- Rubberized concrete incorporates rubber for improved durability and flexibility.
- Nanoconcrete contains Portland cement particles no greater than 100 μm.
- Foam concrete is a lightweight and highly insulating material.
- Air-entrained concrete incorporates tiny air bubbles for enhanced workability and durability.
- Engineered cementitious composite is a bendable concrete with enhanced flexibility.
- Ferrocement is a reinforced mortar or plaster system with high strength and durability.
- Ready-mix concrete is manufactured in batch plants according to engineered mix design.
Types of Cement
- Cement materials can be classified into hydraulic cements and non-hydraulic cements.
- Hydraulic cements require water for setting and hardening, while non-hydraulic cements can set under air.
- Hydraulic cements, such as Portland cement, consist of silicates and oxides.
- The main mineral phases of hydraulic cements are alite, belite, tricalcium aluminate, and brownmillerite.
- Non-hydraulic cement sets as it dries and reacts with carbon dioxide in the air.
- Non-hydraulic cement does not require water for setting and hardening.
- Non-hydraulic cement is resistant to chemical attack after setting.
Chemistry of Cement
- Hydraulic cement hardens through hydration of clinker minerals when water is added.
- The main mineral phases of hydraulic cement are responsible for its mechanical properties.
- The limestone is burned to produce lime in a calcination reaction.
- Lime reacts with silicon dioxide to form dicalcium silicate and tricalcium silicate.
- Lime also reacts with aluminum oxide to form tricalcium aluminate.
- Calcium oxide is obtained by thermal decomposition of calcium carbonate.
- The chemistry of these reactions is still the subject of research.
Ancient Alternatives to Cement
- Bitumen was used by the Babylonians and Assyrians to bind burnt brick or alabaster slabs.
- Ancient Egyptians used sand and burnt gypsum mortar for cementation.
- Ancient Greeks used crushed potsherds as a pozzolan for hydraulic cement.
- Roman engineers used volcanic ash and lime for hydraulic cement.
- Crushed brick or pottery was used as a substitute for pozzolanic ash.
Historical Use of Cement
- Lime was used by the Ancient Greeks and Minoans for cementation.
- The Greeks used volcanic tuff from Thera as a pozzolan.
- Roman engineers used crushed volcanic ash with lime for hydraulic cement.
- The material was called pozzolana and was extracted from Pozzuoli.
- Roman concrete was extensively used in structures like the Pantheon and Baths of Caracalla.
- Hydraulic cement actively used by medieval masons and military engineers in the Middle Ages.
- Structures such as canals, fortresses, harbors, and shipbuilding facilities were constructed.
- Lime mortar and aggregate with brick or stone facing material used in the Eastern Roman Empire and Gothic period.
- German Rhineland utilized hydraulic mortar with local pozzolana deposits.
Development of Cement Techniques
- Tabby, a building material made from oyster shell lime, sand, and whole oyster shells, introduced in the 16th century.
- Concrete formed using tabby.
- French and British engineers formalized technical knowledge for making hydraulic cement in the 18th century.
- John Smeaton's contribution to cement development for Eddystone Lighthouse construction.
- Parkers Roman cement developed by James Parker in the 1780s.
- Louis Vicat identified the principle of combining chalk and clay for cement production in the 19th century.
- Vicat devised a method for intimate mixture of chalk and clay.
- Burning process used in cement production.
- Roman cement replaced by Portland cement in the 1850s.
- Smeaton's work on hydraulic cement apparently unknown to Vicat.
