Class 5 Concrete Construction Flashcards
what are the main constituents of concrete
Coarse aggregate (>4mm), fine aggregate (<4mm), Portland cement, and water.
Modern concrete may also include supplementary cementitious materials, chemical admixtures, and reinforcing steel.
What makes concrete a composite material?
Concrete consists of different materials combined together: aggregates (coarse & fine) embedded in a cementitious binding medium.
What happens when cement interacts with water?
A chemical reaction called hydration occurs, forming hydration products that bond aggregate particles together into a solid mass.
What are the three key phases in concrete microstructure?
- Cement paste (hydrated cement & pores).
- Aggregate particles (coarse & fine).
- Interfacial transition zone (ITZ) (boundary between paste & aggregate).
What is the difference between paste, mortar, and concrete?
Paste (grout): Cement + water (fills gaps/seals joints).
Mortar: Paste + sand (bonds bricks in masonry).
Concrete: Mortar + coarse aggregate (used for structural elements).
Why is concrete used in so many structures?
Concrete is versatile, durable, cost-effective, and strong in compression. It can be moulded into different shapes and withstands harsh environments.
What are the main advantages of concrete? (7
Widely available materials
Cost-effective
Versatile & flexible
Strong in compression
Durable, fire & water-resistant
Good thermal mass & acoustic insulation
Compatible with steel reinforcement
What are the main disadvantages of concrete?
Weak in tension → Cracks easily.
Difficult to recycle.
Creep & shrinkage over time.
Environmental impact (high CO₂ emissions).
Why is concrete considered environmentally problematic?
Concrete production contributes ~8% of global CO₂ emissions.
Most emissions come from Portland cement manufacturing, which is energy-intensive and releases CO₂ from limestone decarbonisation.
What are some strategies to make concrete more sustainable?(5)
- Use supplementary cementitious materials (e.g., fly ash, slag).
- Develop low-carbon cement alternatives.
- Improve concrete mix designs for efficiency.
- Promote recycling and reuse of concrete.
- Use carbon capture technologies in cement production.
What is embodied carbon in concrete?
Embodied carbon refers to the total CO₂ emissions associated with concrete production, including material extraction, processing, and transportation.
What is the function of reinforcing steel in concrete?
Reinforcing steel provides tensile strength to compensate for concrete’s weakness in tension.
Why is thermal mass an important property of concrete?
Concrete absorbs and stores heat, helping to regulate indoor temperatures and improve energy efficiency in buildings.
Why is concrete compatible with reinforcing steel?
Concrete protects steel from corrosion (alkaline environment).
Steel and concrete have similar thermal expansion rates, preventing cracks.
