Lesson -3 - Cement & Concrete Flashcards
What are the main ingredients of concrete?
Cement, fine aggregate, coarse aggregate and water (+admixtures)
Why is concrete popular as a construction material?
Strong (compression), rigid, durable, easily available, low cost, low technology, versatile use
Why is reinforced concrete used in structural members?
Concrete is strong in compression only & therefore reinforcement is included to resist tensile & shear stresses.
What is cement?
A hydraulic binder that when mixed with water, forms a paste that sets and hardens. After hardening, retains its strength and stability even underwater
What is hydraulic and non-hydraulic cement?
Hydraulic: cement that hardens when the water is added
Non-hydraulic: does not set in wet conditions or under water. It sets as it dries & reacts with carbon dioxide in the air.
What are the roles of cement paste?
- Coats, fills the space between and binds the aggregate particles.
- Provides strength & stiffness to concrete
- Responsible for permeability and time-dependent deformation
What is the most common type of cement in general use around the world?
Portland cement
How is Portland Cement produced?
- Collect raw materials such as limestone, clay, sea sand, shale etc.
- Grind raw materials into a very fine powder
- Mix them in predetermined proportions
- Burn them in a large rotary kiln at a temp. about 1400C when the material sinters and partially fuses into clinker
- The clinker is cooled and ground to a fine powder, with some gypsum added
- REsulting product is Portland Cement
What is calcareous Cement?
Cements that contain calcium carbonate
What is Pozolana?
A hydraulic cement/concrete traditionally made by grinding volcanic origin materials with powdered hydrated lime.
What are the 4 main compounds of cement? And their abbreviations
- Tricalcium silicate (C3S)
- Dicalcium silicate (C2S)
- Tricalcium aluminate (C3A)
- Tetracalcium alumina ferrite (C4AF)
What are the properties of the 4 major compounds of cement?
- Tricalcium silicate (C3S):
Hardens quickly
Heat evolved
Early age strength
Light colour - Dicalcium silicate (C2S):
Hardens Slowly
Less heat evolved
Later age strength
Light colour - Tricalcium aluminate (C3A):
Reacts quickly
Heat evolved
Very early setting and strength gain
Poor resistance to Sulphate
Light colour - Tetracalcium alumina ferrite (C4AF):
Reacts quickly
Heat evolved
Little strength
Dark Colour
What does extra water beyond hydration requirement do to a cement?
- Causes capillary voids
- Increases porosity and permeability
- Decreases Strength
- Decreases durability
