Concrete Flashcards
what are the four ingredients in concrete?
Sand
Cement
Water
Aggregate (rock/recycled concrete)
What does each of the four ingredients in concrete for?
Sand - fills the voids/space between the aggregate
Cement - acts as the glue
Water - hydration chemical reaction (between water and cement)
Aggregate (rock/recycled concrete) - takes up the bulk of the concrete
what is the difference between concrete and cement?
Concrete is the thing that holds it together (outcome of mixing four ingredients)
Cement is the mixture (chemical reaction of hydration when mixed with water)
what is a hydraulic and why is cement considered one?
A hydraulic is a chemical reaction called hydration which uses water to create the cements compound.
Cement in considered a hydraulic because it sets and hardens using water.
What must aggregate be free of?
It must be free of silt and organic matter
What is the purpose of Aggregate and what does it provide?
- Filler/bulk of concrete
- Occupies 60-75% of the volume of concrete
- Provides both strength and shape
What is the difference between Large and Fine Aggregate?
Large Aggregate: provides density (fills space) and strength
Fine Aggregates: fills small voids between large aggregate, increase strength on the cement binder.
What are three chemical admixtures and what do they do?
Accelerator: Speeds up hydration
Acrylic Retarders: Slows Hydration
Water reducing admixture: increases the workability of the concrete.
what are the three states of concrete pouring?
Plastic state
Curing state
Hardening state
What is plastic state?
First mix (like cake mix). It is soft and can be worked or moulded into different shapes (poured into a ‘cake pan’ type of thing)
What is curing state?
Concrete begins to stiffen. Setting takes place after compaction and during finishing.
What is Hardening state?
After concrete has set it begins to gain strength and harden.
How do you test concrete to ensure it is the right consistency?
The Slump test
- it is conducted onsite to ensure concrete is ‘good’
- it tests workability and consistency
What should you avoid mixing in concrete?
Avoid mixing salt water unless unavoidable situations.
What is reinforced concrete?
Reinforced concrete adds steel reinforcing bars, steel fibres, glass fibres or plastic fibres to carry tensile loads.
