Green Tech in Construction: Innovative Cement

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Questions and Answers

What is the primary purpose of adding steel reinforcement to concrete?

To reduce setting time

To increase durability

To improve compressive strength

To improve tensile strength (correct)

What can happen to the reinforcing bar due to plastic settlement?

It can be pushed upwards, creating a void (correct)

It can corrode more rapidly

It can become dislodged from the concrete

It can break under the pressure

Which of the following cements has a high early strength and fast setting time?

Calcium aluminate cement (CAC) (correct)

Portland cement

Geopolymer cement

Silica cement

What is a potential application of Geopolymer cement?

Sustainable construction Signup and view all the answers

What can be a problem due to excessive reinforcement in concrete?

Congestion and increased cracking Signup and view all the answers

What is pre-tensioning in prestressing concrete?

A method of applying tension to the tendons before the concrete is poured Signup and view all the answers

What is the result of plastic settlement in freshly placed concrete?

The mixture becomes denser and loses volume Signup and view all the answers

What is a characteristic of Geopolymer cement compared to Portland cement?

It has a lower carbon footprint Signup and view all the answers

What is the primary difference between quick tests and accurate tests?

Time required Signup and view all the answers

Which type of cement has the highest content of Portland cement clinker?

Type I Signup and view all the answers

What is a potential benefit of moving from prescriptive to performance-based standards in concrete standardization?

Increased innovation Signup and view all the answers

What is a drawback of performance-based standards in concrete standardization?

Increased complexity Signup and view all the answers

What is a benefit of prescriptive standards in concrete standardization?

Reduced variability Signup and view all the answers

What is a potential advantage of using performance-based standards in concrete standardization?

Reduced environmental impact Signup and view all the answers

What is the main benefit of using an innovative photocatalytic additive in concretes?

To reduce pollution Signup and view all the answers

How does bacterial self-healing contribute to the durability of concrete structures?

It allows the concrete to self-repair cracks Signup and view all the answers

What type of information would an investment fund looking to invest in green-tech for the construction sector request from a company selling an innovative cement?

Information about the cement's environmental impact Signup and view all the answers

What is the main difference between a masonry block and a brick?

Their size Signup and view all the answers

What is the primary purpose of a veneer in masonry?

To provide aesthetic appeal Signup and view all the answers

Why are dry-pressed bricks more resistant to freeze-thaw damage than soft mud process bricks?

They are denser and stronger Signup and view all the answers

Why are unreinforced masonry walls not used in seismically active regions?

They are prone to cracking and collapsing during earthquakes Signup and view all the answers

What is the main difference between structural masonry and a veneer?

Their structural purpose Signup and view all the answers

What is the main purpose of adding aggregate to concrete?

To improve the workability of fresh concrete Signup and view all the answers

What is the primary function of prestressing in concrete?

To enhance its resistance to flexural load Signup and view all the answers

What is the term for the process of settlement of fresh concrete?

Plastic settlement Signup and view all the answers

Why is limestone not a pozzolan?

It does not react with cement to produce additional hydrates Signup and view all the answers

What is the main difference between pre-tensioning and post-tensioning?

The time of application of the stress Signup and view all the answers

What is the purpose of a passivating film in concrete?

To prevent corrosion of steel reinforcement Signup and view all the answers

Why is the direct measurement of concrete tensile strength rare?

Because it is a difficult property to measure Signup and view all the answers

Why is a standard cube stronger than a standard cylinder, when made from identical concrete?

Because the cube is subject to more uniform stress Signup and view all the answers

What is the primary purpose of prestressing concrete?

To enhance its resistance to flexural load Signup and view all the answers

What is the difference between pre-tensioning and post-tensioning?

Pre-tensioning involves tensioning tendons before casting concrete, while post-tensioning involves tensioning tendons after casting concrete Signup and view all the answers

What is the role of a passivating film in concrete durability?

It prevents the corrosion of steel reinforcement Signup and view all the answers

What is the impact of inadequate curing on the passivating film?

It damages the film, leading to corrosion of the reinforcement Signup and view all the answers

Which surface of a concrete element is more likely to be affected by plastic settlement?

The top surface Signup and view all the answers

What is the primary reason for the weakness of concrete in tension?

It is a brittle material Signup and view all the answers

What is the purpose of grouting the ducts in post-tensioning?

To transfer the prestress force to the concrete Signup and view all the answers

What can cause the passivating film to be damaged?

Inadequate curing, carbonation, or exposure to acidic environments Signup and view all the answers

Study Notes

Innovative Photocatalytic Additive in Concretes

Reduces pollution by utilizing photocatalytic additives in concretes
Adds value by enhancing durability and sustainability of concrete structures

Bacterial Self-Healing in Concrete

Brings added durability to concrete structures through self-healing properties
Utilizes bacteria to repair cracks and damages in concrete

Investing in Green-tech for Construction

Consider investing in companies selling innovative cements with sustainable properties
Request information on the company's environmental impact, durability, and cost-effectiveness

Masonry Blocks and Bricks

Masonry blocks are larger and heavier than bricks, with different composition (concrete or cement)
Bricks are made from clay, with different sizes and compositions

Structural Masonry and Veneer

Structural masonry supports the weight of a building, while veneer is a non-structural layer for aesthetic purposes
Dry-pressed bricks are more expensive and less porous than soft mud process bricks, making them better resistant to freeze-thaw damage

Unreinforced Masonry Walls

Not used in seismically active regions due to susceptibility to cracking and collapse during earthquakes

Hydrate Products in Portland Cement

Four main types of hydrate products: AFm, AFt, C-S-H, and CH
C-S-H is responsible for setting and final strength
Tobermorite is a natural mineral used as a structural model to describe the C-S-H structure

Pozzolanic Reaction

Chemical reaction involving cement chemistry nomenclature
Limestone is not a pozzolan due to its chemical properties

Concrete Terminology

Paste: mixture of cement, water, and air
Mortar: mixture of cement, water, and fine aggregate
Fine aggregate: small particles such as sand or crushed stone
Coarse aggregate: large particles such as gravel or crushed rock

Aggregate in Concrete

Added to concrete for three reasons: to improve strength, to reduce cement content, and to enhance durability
Excessive water can be undesirable due to three reasons: it can lead to segregation, reduce strength, and increase porosity

Plastic Settlement

Process where solid particles in a freshly placed concrete mixture settle under gravity, causing cracks to form above a reinforcing bar
Illustrated through a sketch

Non-Portland Cements

Two examples: Calcium aluminate cement (CAC) and Geopolymer cement
CAC has high early strength and fast setting time, while Geopolymer cement has a lower carbon footprint and comparable strength and durability

Steel Reinforcement

Does not always make for a 'better' concrete, as excessive reinforcement can cause problems such as congestion, increased difficulty in placement and compaction, and reduced durability
Pre-tensioning and post-tensioning are two methods of prestressing concrete, with different applications and benefits
Prestressing is mainly used to enhance flexural load resistance, but can also enhance compressive strength
A passivating film is a layer of oxide or hydroxide that forms on the surface of steel reinforcement, protecting it from corrosion

Concrete Durability

Plastic settlement is more likely to cause defects on the top surface of a concrete element, especially if it is heavily reinforced or has a high water content
Chloride can cause corrosion problems in reinforced concretes, as explained through a Pourbaix diagram

Concrete Tensile Strength

Direct measurement is rare due to difficulties in testing
Alternative tests and mathematical relationships can be used to determine this material property

Concrete Standards

EN 197-1 cement types have different clinker contents, with Type I having the highest content and Type IV having the lowest
Moving from a prescriptive basis to a performance basis in concrete standardization can bring benefits such as increased flexibility, innovation, and optimization of materials and designs

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Description

This quiz explores the use of innovative photocatalytic additives in concrete to reduce pollution and increase durability through bacterial self-healing. It also considers the investment potential of a green-tech cement company.