Cement Types and Production

Types of Cement

• Cement mixes limestone, chalk, marl, or clay, heated and ground into fine powder and is an ingredient of concrete.
• Concrete constitutes cement, water, stone and sand

Early Cement Use

• The utilization of cement materials dates back to ancient times.
• Ordinary lime and hydraulic lime are the origin of cement materials.
• Ordinary lime comprises pure limestone that has been slaked, bonding after water is added.
• Ordinary lime absorbs carbon dioxide and transforms from calcium oxide to calcium carbonate.
• Hydraulic lime forms from calcining impure limestone containing silica, alumina, and iron oxide

Cement Production Phases

• Mixing
• Blending and Mixing
• Grinding
• Fuel
• Calcination, gypsum combined with clinker
• Smelting and Combustion
• Final Grinding
• Exhaust and cold air

Fundamental Elements in Cement

• Cement includes:
  • Oxygen (O2)
  • Silica (Si)
  • Calcium (Ca)
  • Aluminum (Al)
  • Iron (Fe)

Cement Compounds

• Cement compounds include:
  • Calcium Oxide (CaO)
  • Silicon Dioxide (SiO2)
  • Aluminum Oxide (Al2O3)
  • Ferric Oxide(Fe2O3)

Main Compounds in Cement

• Main Compounds:
  • Tricalcium Silicate (C3S)
  • Dicalcium Silicate (C2S)
  • Tricalcium Aluminate (C3A)
  • Tetracalcium Aluminoferrite (C4AF)

Portland Cement

• Increases in silica and decreases in alumina give slow setting cement that resists chemical effects.
• Increased alumina and decreased silica yields quick-setting cement.

Portland Cement Oxide Composition

• Calcium Oxide (CaO) makes up 60-67%
• Silicon Dioxide (SiO2) makes up 17-25%
• Aluminum Oxide (Al2O3) makes up 3-8%
• Ferric Oxide (Fe2O3) makes up 0.5-6%
• Magnesium Oxide (MgO) makes up 0.1-4%
• Potassium and Sodium Oxide (K2O, Na2O) makes up 0.2-1.3%
• Sulfur Trioxide (SO3) makes up 1-3%

Cement Types

• Types vary by ingredient additions and proportion changes and allow uses from construction to sulfate-resistance.
• Cement types are:
  • Ordinary Portland Cement (OPC)
  • Portland Pozzolana Cement (PPC)
  • Rapid Hardening Cement (RHC)
  • Extra Rapid Hardening Cement
  • Sulfate Resisting Cement (SRC)
  • Quick Setting Cement (QSC)
  • Super Sulfated Cement (SSC)
  • Low Heat Cement (LHC)
  • Portland Slag Cement (PSC)
  • High Alumina Cement (HAC)
  • Air Entraining Cement (AEC)
  • White Cement
  • Colored Cement
  • Expansive Cement
  • Hydrophobic Cement

Ordinary Portland Cement (OPC)

• OPC is the most important and common cement type.
• OPC's strength is measured after 28 days and classified into grades.
  • 33 Grade: 28-day strength is not less than 33N/mm2
  • 43 Grade: 28-day strength is not less than 43N/mm2
  • 53 Grade: 28-day strength is not less than 53 N/mm2
• Higher-grade cements are more popular in modern construction

Portland Pozzolana Cement (PPC)

• Pozzolanas include reactive siliceous and aluminous materials that have little to no cementitious properties.
• PPC constitutes OPC clinker + Pozzolana material in 15-35%.
• PPC:
  • Generates low heat of hydration
  • Improves workability and durability of concrete.
  • Is economical and environmentally friendly

Rapid Hardening Cement (RHC)

• RHC develops early strength, and is High early strength concrete.
• RHC contains:
  • Higher C3S
  • Lower C2S
  • Finer grinding of clinker
• 1-day RHC strength equals roughly 3-day OPC strength
• 3-day RHC strength equals roughly 7-day OPC strength
• Ultimate strengths from RHC and OPC are equal.
• RHC is suitable for:
  • Early removal of formwork
  • Emergency repair work
  • Cold weather concreting
  • Precast concrete construction
• RHC is unsuitable for mass concrete constructions due to high Heat of Hydration.

Extra Rapid Hardening Cement

• Extra rapid hardening cement accelerates the setting and hardening process, and is made by adding calcium chloride with RHC.
• Calcium chloride addition should not exceed 2% of the RHC weight.
• The cement must be mixed, transported, placed, compacted, and finished within 20 minutes.
• Do not store more than a month; do not use in prestress concrete, as it induces initial corrosion.
• The strength of extra rapid hardening cement is about 25% higher at 1-2 days and 10-20% higher at 7 days.
• It is suitable for cold weather concreting.

Sulphate Resisting Cement (SRC)

• External sulphate ions react with calcium hydroxide, Ca(OH)2, to form Calcium Sulphate, CaSO4, further reacting with C3A to form ettringite.
• Ettringite causes volumetric expansion and concrete cracking, known as Sulphate Attack.
• SRC is obtained by:
  • Lowering C3A & C4AF content
  • Increasing C₂S and C3S content
  • Limiting C3A content to 5% having a high Silicate Content
• SRC is suitable for:
  • Sewage Treatment Works
  • Marine Structures
  • Foundation Works
  • Canal linings

Quick Setting Cement (QSC)

• QSC sets quickly with reduced gypsum content during clinker grinding and is sometimes known as Gypsum-free cement.
• QSC is suitable for underwater constructions and grouting operations.

Super Sulphated Cement (SSC)

• Super sulphate cement mixes 80-85% granulated slag, 10-15% hard burned gypsum, and 5% Portland cement clinker.
• This cement has low heat of hydration and high sulphate resistance.
• SSC is suitable in:
  • Marine Works
  • Foundations where chemically aggressive soil exists
  • Fabrication of reinforced concrete pipes set to be buried in sulphate-bearing soils.

Low Heat Cement (LHC)

• The high heat of hydration in mass concrete can cause thermal cracks and durability issues.
• Consequently, cement that liberates low heat of hydration at early stages was developed.
• LHC contains:
  • Reducing C3S content
  • Reducing C3A content
  • Increasing C₂S content
• LHC is suitable for mass concreting works like dams.

Portland Slag Cement (PSC)

• Portland slag cement mixes Portland cement clinker, gypsum, and granulated blast furnace slag.
• Blast furnace slag comes from blast furnaces.
• PSC exhibits:
  • Low heat of hydration
  • Low permeability
  • Better resistance to chloride and sulphate attacks
  • Increased durability
• PSC is suitable for:
  • Mass concreting works
  • Marine works
  • Foundations where aggressive chemicals occur in soil.

High Alumina Cement (HAC)

• HAC mixes limestone and Bauxite, and an alumina rich ore.
• The percentage of C3A in HAC is about 35%.
• HAC exhibits:
  • High heat of hydration
  • Quick setting property
  • High ultimate strength in a short period. About 20% of the ultimate strength is reached in one day. and has
  • High refractory properties
• HAC is suitable for cold temperatures, refractories, kilns, chimneys, and other high heat settings.
  • HAC should not be mixed with other cement, or any admixture.

Air-Entraining Cement (AEC)

• AEC mixes small amount of air-entraining agent with ordinary Portland cement clinker at the time of grinding.
• During mixing, the air-entraining agent produces tiny and stable air bubbles, which later create non-connected pores that act for ice expansion.
• Its role includes:
  • Increases resistance to frost action
  • Increases workability
  • Reduces segregation and bleeding
  • Decreasing density and strength of concrete
• AEC is most suitable for colder areas to prevent freeze & thaw effects.

White Cement

• High purity limestone (96% CaCO3 and <0.07% iron oxide) or china clay with ~0.75% iron is utilized.
• White cement properties are similar to OPC.
• It is best used in architectural works.

Colored Cement

• Manufacture colored cement using white or grey Portland cement base.
• Using white cement base is more costly, grey base produces red or brown cement only.
• Coloured cement mixes Portland cement with 5-10% pigment.
  • Chromium oxide gives a green color
  • Cobalt produces blue
  • Iron oxide in varying proportions yields brown, red, and yellow shades
  • Manganese oxide yields black and brown shades

Expansive Cement

• Concrete shrinks with ordinary Portland cement and free water.
• New cement that doesn't change in volume when drying is manufactured with expanding agents (Sulphoaluminates) and stabilizers.
• It is best utilized for grouting.

Hydrophobic Cement

• Grinding ordinary Portland cement mixed with water repellent film-forming substances makes hydrophobic cement.
• These coatings protect cement particles from moisture during storage and transportation.
• The water repellent substances include oleic acid and stearic acid.
• The film breaks down when the cement and aggregates mix, exposing cement particles for normal hydration.
• Hydrophobic cement is best for places with substantial rainfall or moisture.

Properties of Cement

• physical and chemical properties are the foundation to accepting or rejecting usage of cement
• Cement can be tested as:
  • Dry cement
  • Cement paste
  • Cement mortar
  • Cement concrete

Cement Characterization

• Different construction mixes of cement can be characterized by physical properties.
• The physical properties of good cement include:
  • Fineness
  • Soundness
  • Consistency
  • Strength
  • Setting Time
  • Heat of Hydration
  • Loss of Ignition
  • Bulk Density
  • Specific Gravity (Relative Density)

Fineness of Cement

• Particle size, achieved by grinding the clinker, measures the fineness of cement.
• The fineness of cement contributes to the rate of hydration
• Measurement is achieved by way of the Blaine's Air Permeability Method.

Blaine's Air Permeability Method

• The Blaine air permeability method determines cement fineness by the surface area per gram.
• Fineness is known as the specific surface
• Surface areas for particles are measured in square meters per kilogram

Fineness Test Setup

• A manometer.
• A conical socket.
• A stopcock.
• Etched lines to measure the air in the manometer.
• A permeability cell.
• A plunger.
• Rubber bulb
• Compacted Cement bed
• Perforated disc

Fineness Test Measurements

1. Filters are weighed, cemented, and then reweighed
2. The permeability cell is attached to the U-tube manometer.
3. Air is evacuated to a particular level
4. The test is ran and the time is measure for oil to fall from level 2 to level 3

Sieve Method Apparatuss

• Apparatus:
• 90µm Sieve
• Balance capable of weighing 10g to the nearest 10mg
• Glass rod
• Stoppered jar
• Pan and Lid

Sieve Test Method

1. Stir the sample of cement to be tested by shaking for 2 minutes in a stoppered jar to disperse lumps.
2. Stir the resulting powder gently using a clean dry rod in order to distribute the fines throughout the cement.
3. Attach a pan under the sieve to collect the cement passing the sieve-
4. Weigh approximately 10 g of cement to the nearest 0.01 g and place it on the sieve- fit the lid over the sieve-
5. Shake the sieve by swirling, planetary, and linear movement until no more fine material passes through it.
6. Remove and weigh the residu- Express its mass as a percentage (R) of the quantity first placed in the sieve-
7. Repeat the steps 3 to 5 with a fresh sample to obtain R₂.
8. If the results differ by more than 1 percent absolute, carry out a third sieving and calculate the mean of the three values-

Fineness Calculation

• Fineneess can be calculated by:
• R= (R₁+R₂+R₃) / 3 Fineness modulus of cement = R / 100

Cement Fineness Importance

• Importance of Cement Fineness:
• The fineness of cement affects hydration rate, and in turn, the strength-Increasing fineness causes an increased rate of hydration, high strength, and high heat generation-
• Bleeding can be reduced by increasing fineness. However, increased fineness can also lead to the requirement of more water for workability, resulting in a higher possibility of dry shrinkage-
• The increased surface area-to-volume ratio will ensure a more available area for water-cement interaction per unit volume-

Soundness of Cement

• Ability of cement not shrink during hardening is know as soundness
• Ability can measured by:
  • EN-196 (1995): which is based on the Le Châtelier test method
  • Autoclave test (ASTM-C151)
• Cement of good quality retains its volume after setting without delayed expansion, caused by excessive free lime and magnesia.

Type of Sounndness Tests

• Tests:
• Unsoundness of cement may appear after several years, so tests for ensuring soundness must be able to determine that potential
• Le Chatelier Test - This method tests the expansion of cement due to lime. Cement paste is taken between glass slides and submerged in water for 24 hours at 20+1°C. It is taken out to measure the distance between indicators and then returned underwater, brought to boil in 25-30 mins and boiled for an hour After cooling, the distance between indicator points is measured again. In a good quality cement, the distance should not exceed 10 mm.
• Autoclave Test - Cement paste is placed in an autoclave and slowly brought to 2.03 MPa, and then kept there for 3 hours. The change in length of the specimen (after gradually bringing the autoclave to room temperature and pressure) is measured and expressed in percentage. The requirement for good quality cement is a maximum of 0.80% autoclave expansion Standard autoclave test:
• AASHTO T 107 and
• ASTM C 151: Autoclave Expansion of Portland Cement

Le-Chatelier's Apparatus Requirements

• le-Chatelier’s Appartus’ Aim:To find out the soundness of Cement.
• Apparatus:
• Le- Ch-atelier’s Apparatus
• Weighing balance
• Measuring Cylinder
• Trowel
• Mixing pans heater,thermometer.
• Standard Reference:The test is performed as per IS: 4031(Part - 1)-1988

Le-Chatelier's Apparatus - Theory

• The cement of good quality does not contain the impurities like free lime, magnesia and sulphates, so this should be checked before use.
• When it contains the impurities named above, it can expand after reacted with the water, which will result in the unwanted results like, cracking, unwanted expansion of the dimensions and lower strength.
• Le-Ch-atelier’s Apparatus is the standard apparatus prescribed as per IS:5514-1969 to check the presence of the impurities in cement. Cement is said to be sound when the expansion is below 10 mm.

Le-Chatelier's Procedure

• Prepare a cement paste of 78% of standard consistency of the cement, and fill it into the split brass cylinder
• Cover the top and bottom of the cylinder and put it in water at 27 degrees Celsius for 24 hours.
• After 24 hours, measure the separation between the two indicators at their pointed ends.
• Then heat the whole water and immersed cylinder with paste up to a boiling temperature in 30-35 minutes and then boiling for 3 hours
• After cooling it down, again measure the separation between the two pointers

Le-Chatelier's Calculations

• Calculations:
• Let the reading before putting the cement paste into the boiling temperature = L1
• After three hours of hot water immersion = L2
• Expansion = L2-L1
• Result: As the value of expansion (Less/More)…. than 10 mm so the cement is ….(Sound/Unsound)

Consistency of Cement

• Consistency is cement paste's ability to flow, normally tested using vicat test.
• Cement paste has a normal consistency when the plunger penetrates to 10±1 mm in the vicat test.

Cement Consistency with Vicat's Apparatus

• This test finds the fundamental amount of water desired to create a cement paste based on IS Code #4031
• The Vicat plunger is set for 5-7 mm towards the Vicat mould at the end of the experiment

VICAT Tester REQUIREMENTS

• Apparatus Required
• Weighing balance of 1000g with 1g accuracy
• Vicat Apparatus
• Vicat Mould
• Measuring Cylinder 200ml
• Glass Plate
• Precautions
• The test should be conducted at Room Temperature
• The humidity of the room should be+ or – 65+
• The whole process of mixing should be made on GlassSheet

Vicat Test Prodecure

• Take 400 grams of Cement
• Assuming that consistency would be 29.5% since we are taking OPC. This is trial and error method
• Take 29.5% of water that means (400×29.5%) = 118 Grams of water
• Mix the water with cement and wait for 3-5 Minutes. Mix the cement well as shown in the video
• Now fill the Vicat mould with the cement paste
• Ensure to compact the paste well after filling the mould
• Fill the cement paste to the top of the mould Remove the excess paste by the trowel
• Now place the mould at the Vicat apparatus
• Now remove the plunger and allow it to penetrate through the paste
• After Removing wait for 3 seconds
• Note down the reading on the Vicat measuring scale

Knowledge Checks

• CaO is the responsible raw material

• Autoclave method can be used to determine the expansion

• For Ordinary Portland Specific Surface is not less than 2250 cm²/g

• Vicat's Apparatus is used to test Consistency

• Portaland can be tested for expansion through the Soundness test

• The initial setting time for Ordinary Portland cement as per IS specifications should be less than 30 minutes

• Rice cement mortars are more liable to cracking as compared to lean mortars because rich mortars have high shrinkage

• Early attainment of strength in rapid hardening cement is mainly due to finer grinding

• Slow setting cement have higher percentage of Gypsum

• Rapid hardening portland cement contains more C3S

• Lime is the chemical composition that has highest content in OPC

• Excess of lime can cause The cement to expand and disintegrate

• Silica gives strength to the cement

• Alumina supports to facilitate a quick set forthe cement

• Iron Oxide is the pigment that gives the colour to the cement

• Rapid Hardening contains the most C3S and the least C2S

• For underwater applications, select Quick Setting

• In Low Heat formulas try calcium aluminate needs reductio

• Sulphate Resisting is used in Treatment Plants

• Portland Pozzolana is used for age building

• Colored Cement is used for for make artificial marble

• Hydrated to create a bond, Expansive Cement is needed

• When looking to store the type Hydrophobic is perferred

• AEC has increased frost resistance

• To preserve, Waterproof the Cement is used

• Road formers needs Rapid Hardening

• To decrative Coloring the Cement must be employed

• To get the mix, Blast Furnace Slag is applied to Cement

• After applying acid addd water

• Lowest 0.4 is optimal

• Calcium aluminates have increased hydration