2.1. Concrete

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Questions and Answers

Which type of lime is primarily used in masonry mortar and must be slaked before use?

Hydrated lime

Quicklime (correct)

Finishing hydrated lime

Special finishing hydrated lime

What is the main characteristic of finishing hydrated lime?

Great affinity for water

Can be used as a putty immediately

Characteristic whiteness and plasticity (correct)

Contains a high percentage of impurities

What primary method is used to transform gypsum rock into plaster?

Slaking the gypsum with water

Adding pozzolana to gypsum

Mixing gypsum with hydrated lime

Heating to high temperatures to remove water (correct)

Which historical civilization first utilized cement by mixing slaked lime with pozzolana?

Romans Signup and view all the answers

What is the pure gypsum product commonly used in construction?

Plaster of Paris Signup and view all the answers

What effect does adding hydrated lime have on gypsum plaster?

Enhances plasticity Signup and view all the answers

Who is credited with the rediscovery of hydraulic cement in the 18th century?

Smeaton Signup and view all the answers

Which type of plaster is characterized by containing a significant amount of impurities?

Hard wall plaster Signup and view all the answers

In what year was Portland cement invented and patented by Joseph Aspdin?

1824 Signup and view all the answers

What is the primary use of heavyweight concrete?

Walls containing radioactive materials Signup and view all the answers

Which type of concrete incorporates air or bubble gas to provide high insulating properties?

Cellular concrete Signup and view all the answers

What is the main property of porous concrete, also known as pervious concrete?

Allows water to pass through Signup and view all the answers

In which application is polymer-impregnated concrete primarily used?

Bridges and repair projects Signup and view all the answers

Which concrete type is specifically suited for underwater applications?

Tremie concrete Signup and view all the answers

What factor does NOT affect the strength and durability of concrete?

Color of the concrete Signup and view all the answers

What is a characteristic feature of High Alumina Cement?

It has high resistance to hydroxylic compounds. Signup and view all the answers

Which type of Portland Cement is specifically for situations requiring early strength?

Quick-setting high early strength cement Signup and view all the answers

Which component of Portland Cement is primarily responsible for early hardening?

Tricalcium Silicate (C3S) Signup and view all the answers

What is a key characteristic of Pozzolanic Cement?

It consists of lime mortar combined with pozzolanic material. Signup and view all the answers

For which application is White Portland Cement most commonly used?

Marble, granite, and limestone applications Signup and view all the answers

What distinguishes Type IA Portland Cement from Type I Portland Cement?

Type IA contains additives that create air-entrained concrete. Signup and view all the answers

Which of the following cements is generally weaker than other cement types?

Magnesium-OxySulphate Cement Signup and view all the answers

Why is Slag Cement considered a type of pozzolanic cement?

It is made from fine particles of ash from furnaces. Signup and view all the answers

Which cement type is specially designed to resist chemicals found in alkaline water or soils?

Sulphate-resisting Cement Signup and view all the answers

What role does gypsum play in Portland Cement?

It regulates the setting time. Signup and view all the answers

Which type of cement is used primarily in applications requiring rapid strength development?

Type III Signup and view all the answers

What distinguishes Type I (S) cement from Type I (PM) cement?

Type I (S) contains granulated blast-furnace slag. Signup and view all the answers

Which type of cement is best suited for massive structures where heat generation must be minimized?

Type IV Signup and view all the answers

What is the main characteristic of expansive cements?

They increase in volume during setting. Signup and view all the answers

Which of the following is a type of masonry cement classified by ASTM C 91?

Type S Signup and view all the answers

Which type of cement is known for its resistance to sulfate attack and is ideal for marine structures?

Type V Signup and view all the answers

What is a key feature of waterproofed Portland cement?

It reduces capillary water transmission. Signup and view all the answers

Which type of blended cement includes both Portland cement and fly ash?

Type IP Signup and view all the answers

What is the purpose of air-entraining additives in Type IIA cement?

To enhance workability. Signup and view all the answers

Which type of cement is specifically made for use in sealing oil wells due to its slow setting properties?

Oil Well Cement Signup and view all the answers

What is concrete primarily composed of?

Cement, aggregate, and water Signup and view all the answers

How is mortar different from concrete?

Mortar is made with fine aggregate, while concrete is made with large aggregate. Signup and view all the answers

What indicates that cement has been improperly stored?

It has hardened into clumps. Signup and view all the answers

What does the term 'false set' refer to in cement?

The stiffening of the mixture without significant heat generation. Signup and view all the answers

What is the approximate weight of one bag of Portland cement?

94 pounds Signup and view all the answers

Which type of concrete is primarily used for load-bearing and exterior walls?

Lightweight-structural concrete Signup and view all the answers

What is the effect of the heat of hydration on concrete?

It aids in the acceleration of the setting process. Signup and view all the answers

What are lightweight-insulating concrete aggregates typically made of?

Perlite and wood chips Signup and view all the answers

Which type of concrete has a compressive strength between 2,000 and over 8,000 psi?

Normal weight concrete Signup and view all the answers

What should be the maximum height for stacking bags of cement to prevent moisture absorption?

12 sacks high Signup and view all the answers

Study Notes

Lime

One of the oldest building materials used as a mortar and plaster
Quicklime (calcium oxide): Reacts with water; used in masonry mortar.
Slaking/Hydration: Mixing quicklime with water, releases heat.
Hydrated Lime (Calcium Hydroxide): Used for mortar, base coat plaster, and concrete
- Mason's hydrated lime: Made from quicklime, used in mortars, base coat plaster
- Finishing hydrated lime: White and plastic; used in finishing plaster coats
- Special finishing hydrated lime: Becomes more plastic after 30 minutes

Gypsum

Used as plaster by Egyptians, Greeks, and Romans
Gypsum rock: Heated to remove water, turning it into plaster products.
Products:
- Plaster of Paris: Pure gypsum product
- Hard wall plaster: Contains impurities (39.5%)
Hard finishing plaster: All water removed with heating; hardens slowly
- Example: Keene's cement
Plasticity: Can be made more plastic by adding hydrated lime
Fibers: Hemp, sisal, jute fibers/hair added for cohesiveness

Cement

Romans developed cement by mixing slaked lime with pozzolana
Cement knowledge lost after the Roman Empire
Rediscovered by Smeaton in 1756
Portland cement invented by Joseph Aspdin in 1824
Today, "cement" generally refers to Portland cement

Cementitious Materials

Quick-Setting Alumina Cement (Bauxite): Quick-setting cement made from bauxite
High Alumina Cement: Also known as Aluminous Cement and Calcium Aluminate Cement; resistant to hydroxylic compounds; can be used as an accelerator for Portland Cement
Masonry Cements: Portland cement mixed with Hydrated Lime, slag, silica, etc.
Natural Cements: Made from natural materials; sets faster than Portland cement but develops strength more slowly
Pozzolanic Cement: Lime mortar mixed with pozzolanic material (high silica content) like volcanic ash, slag, or pumice
- Slag cement: A type of pozzolanic cement made from slag
- Flyash: Another pozzolanic cement, aluminous and siliceous material reacting with water
Natural and Slag Cements: Used in structures where mass and weight are important

Types of Portland Cement

Portland Cement: Finely pulverized clinker mixed with argillaceous and calcareous materials; gypsum regulates settling time
Portland Cement Components:
- Tricalcium Silicate (C3S): Responsible for early hardening and strength gain
- Dicalcium Silicate (C2S): Responsible for long-term strength gain
- Tricalcium Aluminate (CA): Contributes to initial setting
- Tetracalcium Aluminoferrite (C4AF): Contributes to cement manufacturing, allows lower clinkering temperatures
Types of Portland Cement:
- Slow-setting cement: Used for situations requiring a slower setting time
- Quick-setting high early strength cement: Used when early strength is essential
- Sulphate-resisting cement: Used where the cement needs to resist alkaline water or similar soils
- White Portland Cement: Used for its light color, widely applied today; free of iron; common in marble, granite, and limestone applications
Types conforming to ASTM C-150:
- Type I (Ordinary Portland): General use; used in concrete, pavements, floors, reinforced concrete buildings
- Type IA (Air-entrained): Type I cement with air-entraining additives to create air-entrained concrete

Other Cementitious Materials

Magnesium-OxySulphate Cement: Good binding properties but weaker than oxychloride cement
Phosphate Cement (Quick-Setting): Used for patching, sprayable foamed insulation, and coatings
Waterproof Cement: Used in cementitious waterproofing membranes

Cement Types

Portland Cement Types

Type I: Ordinary Portland Cement

Blended Cement

Portland cement blended with by-product materials (slag, fly ash, silica fume, pozzolans)
Five classes recognized by ASTM C 596, including Portland pozzolan cement (Type IP and Type P)

Special Cements

Masonry Cements: Portland cement, air-entraining additives, and plasticizers; used in mortar for masonry
Expansive Cements: Increase in volume during setting; used for shrinkage control in concrete
Special Cements:
- Oil Well Cement: Slow setting, resistant to high temperatures and pressure, used for sealing oil wells
- Waterproofed Portland Cement: Reduces capillary water transmission
- Plastic Cement: Portland cement and plasticizing agents; for mortar, plaster, and stucco
- Gun Plastic Cement: Similar to plastic cement; applied by compressed air guns
- Block Cement: Similar to Type III, but with controlled color
- Pipe Cement: Specially made for centrifugally spun pipe
- White/Colored Portland Cement: Made from selected raw materials; white or another color instead of gray; used for architectural purposes

Concrete

Definition

A proportioned mixture of cement, aggregate, and water.
Concrete hardens and becomes stone-like with proper proportions.

Cementitious mixtures

Fine aggregate (less than 6mm): Mortar, stucco, or cement plaster
Large aggregate (more than 6mm): Concrete
Steel embedded: Reinforced concrete
No steel: Plain or mass concrete

Regulated Set Cement

Sets in a few hours to one hour

Packaging and Storage of Cement

Packed and sold in bags (1 cubic foot, 94 pounds)
Quantities also expressed in barrels (4 bags, 376 pounds)
Protect from injury and dampness.
Store in a shed with a raised wooden floor
Avoid storing in high piles to prevent moisture absorption

Water-Cement Reaction

Hydration

Chemical reaction between Portland cement and water

Setting

Cement and water form a paste, eventually becoming stiff and hard
Hardening process is called setting
False Set: Stiffening of the mixture with little heat generation

Heat of Hydration

Heat generated during the water-cement reaction

Types of Concrete

Normal Weight Concrete

135–165 lbs/ft³, compressive strength between 2,000 and over 8,000 psi
Used for structural framing, pavements, and floors

Lightweight-Structural Concrete

85-115 lbs/ft³, resistance to heat flow
Used for load-bearing and exterior walls, and prestressed concrete

Lightweight-Insulating Concrete

15-90 lbs/ft³, aggregates like perlite, vermiculite, expanded polystyrene, wood chips, or fibers.
Used to fill over metal roof decks, partitions, and panel walls

Concrete Types

Heavyweight Concrete

Density: 130-290 lbs/ft³
Use: Walls of spaces containing radioactive materials; counterweights

Cellular Concrete

Use: High insulating properties are required (e.g., foundations)
Properties: Air or bubble gas suspended in mortar

Gap-graded concrete

Use: Where aggregate is exposed (e.g., foundations)
Properties: Inexpensive concrete

Shotcrete or Gunite

Use: Where formwork is not desirable
Properties: Pneumatic equipment using dry/wet method

Pre-placed concrete

Use: Special forms/surfaces
Properties: Coarse aggregate placed dry; mortar pumped into it

Pumped Concrete

Use: Concrete placed high above grade or complex shapes

Ferrocement

Use: Containers, bins, boat hulls, etc.
Properties: Mortar with reinforcing wire

Fiber-reinforced Concrete

Use: Slabs on grade, pavements, pneumatically placed concrete, precast, overlays
Properties: Short fibers added to control shrinkage and increase strength.

Other Concrete Types

Nailing: Roof decks; high nail holding strength
No slump concrete: Placed in a consistency of 6mm (1/4"); high strength, low shrinkage
Porous concrete (Pervious concrete): Drainage pipes, walls; allows water to pass through
Permeable pavement: Pavements; high porosity for rainwater runoff
Tremie Concrete: Placing concrete underwater; gravity feed from hopper through vertical pipe
Polymer-impregnated concrete: Surface impregnation of bridge decks; repair; underwater/marine applications; irrigation structures
Polymer-Portland Cement Concrete (PPCC) or Polymer Cement Concrete (PCC) or Polymer Modified Concrete (PMC) or Latex-Modified Concrete (LMC): Bridge deck coverings, floor construction, precast construction, patching compound
Polymer Concrete (PC): Curtain and wall facing panels; polymers replace lime-type cements
Sulphur concrete: Industrial floors, bridge decks, leach tanks, sewer pipes; rapid solidification; strength similar to Portland cement
Reinforced concrete: Various; primary reinforcing may be bar or rods
Prestressed concrete: Various, pretensioned: section is placed in compression using pretensioned steel wires
Posttensioned concrete: Various: section is placed in compression using posttensioned cables after casting

Factors Affecting Strength and Durability of Concrete

Water-Cement Ratio
Cement-Aggregate Ratio
Size of Coarse Aggregates
Ratio of Fine Aggregates to Coarse Aggregates
Type of Cement

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Module 1 - Materials of Construction - Building Technology (Atlas)