Places Concrete

Chapter C8 – Places Concrete

Topic 1 – Concrete mixtures and admixtures

Concrete is used as a construction material because of its:

• Ability to take any shape
• Ability to support a lot of weight
• Durability
• Availability

When Portland Cement mixes with water, air, aggregates and admixtures hydration occurs and concrete is produced. One of the effects of hydration is the production of heat as the cement cures. Under ideal conditions concrete will continue the hydration process gaining strength. If the curing is disrupted hydration will stop and the concrete may not reach its desired strength. Concrete strength is measured in Megapascals (MPa).

For additional information refer to:

• Carpentry “Characteristics of Concrete” Chapter 29
• Principles and Practices of Commercial Construction, “Concrete Work” and “Concrete Admixtures, High Strength Concrete Work”

There are five types of Portland cement manufactured:

1. Type 10 – normal Portland cement
2. Type 20 – modified Portland cement
3. Type 30 – high early strength Portland cement
4. Type 40 -low heat Portland cement
5. Type 50 – sulphate – resistant Portland cement

Source: https://www.geograph.ie/photo/6002426

Aggregate is a mixture of sand, gravel and crushed stone and acts as a filler in the mixture to reduce cost. Aggregate is classified by the size of its largest particles as well as its grade. Admixutres are chemicals that have desired properties for the mix and serve six main functions:

1. Water reduction
2. Delay setting time
3. Early-strength development
4. Workability
5. Air entrainment
6. Corrosion resistance

Review Instruction Sheet (IS) on Brightspace:

CONC 100/122, p. 1 – 14:

• IS 2.2 Portland Cement
• IS 2.3 Aggregates for Concrete
• IS 2.4 Concrete Admixtures

Review Text:

• NBC, section 9.3.1