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Introduction to Concrete

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Presentation on theme: "Introduction to Concrete"— Presentation transcript:

1 Introduction to Concrete
Prepared by: Marcia C. Belcher Construction Engineering Technology

2 Concrete As A Material Concrete, literally, forms the basis our modern life: Roadways/transportation systems Airstrips Infrastructure (bridges, dams, buildings) Harbor protection (breakwalls) Water distribution (pipes & conduit)

3 Concrete has deep roots in history: Wall at Palestrina, Italy, 1st Century BC

4 Roman Aqueduct & Pantheon

5 Concrete The word “concrete” originates from the Latin verb “concretus”, which means to grow together.

6 Advantage of Concrete We have the ability to cast desired shapes
Arches, piers, columns, shells Properties can be tailored according to need (strength, durability, etc.) Ability to resist high temperatures Will maintain structural integrity far longer than structural steel Does not require protective coatings Can be an architectural & structural member at the same time

7 Sculptural Qualities of Concrete at Chapel at Ronchamp (France)

8 Concrete Structural Frame City of Arts and Sciences, Valencia, Spain

9 Properties of Quality Concrete
Workability Durability Strength Chloride Penetration Resistance Abrasion Resistance

10 The Nature of Concrete It is a composite material
Aggregates are 65% - 80% of the volume Fine aggregate: sand Coarse aggregate: stone Cement: General term & applies to any binder Portland cement fly ash ground slag silica fume Water

11 Concrete Microstructure

12 The Purpose Of The Aggregates
Large aggregates: provide density (fill space) provide strength Fine aggregates: fill small voids between large aggregates Increases strength of the cement binder

13 The Cement Matrix Cement: Water produces a crystalline structure
binds aggregates together Water causes chemical reaction to occur water/cementitious “react” produces workability

14 What is Portland Cement?
Raw limestone, clay & gypsum minerals are ground into powder & heated in kiln (1600 ° C) Minerals interact at that temperature to form calcium silicates (clinker) Available in five types, each with varying performance characteristics and uses

15 Portland Cement Manufacturing Process

16 Clinker

17 Hydration Portland cement becomes cementitious when mixed with water
This reaction is referred to as hydration. During hydration, a crystalline structure grows to form bonds Hydration begins as soon as water meets cement Rate of hydration increases with increased cement fineness

18 In Fact……. Concrete does not gain strength by “drying out”
Concrete must have continuous free access to water to achieve its ultimate strength!!

19 Air Entrainment Admixtures
All concrete containes “entrapped” air Large bubbles Large voids are undesirable for durability & permeability Entrained air Bubbles are microscopic in size & distributed through out concrete Increases durability by providing “escape route” for freezing water as it expands

20 Entrapped Air Voids

21 Entrained Air

22 When Do We Use Air Entrained Concrete?
Concrete to be placed in exterior locations requires air entraining (water/freeze/thaw)

23 Water Reducers (Super-Plasticizers)
Increases viscosity Water can be reduced Results in higher strength and more durable concrete due to reduced water

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