Presentation on theme: "Introduction to Concrete"— Presentation transcript:
1 Introduction to Concrete Prepared by:Marcia C. BelcherConstruction Engineering Technology
2 Concrete As A MaterialConcrete, literally, forms the basis our modern life:Roadways/transportation systemsAirstripsInfrastructure (bridges, dams, buildings)Harbor protection (breakwalls)Water distribution (pipes & conduit)
3 Concrete has deep roots in history: Wall at Palestrina, Italy, 1st Century BC
5 ConcreteThe 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, shellsProperties can be tailored according to need (strength, durability, etc.)Ability to resist high temperaturesWill maintain structural integrity far longer than structural steelDoes not require protective coatingsCan 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 WorkabilityDurabilityStrengthChloride Penetration ResistanceAbrasion Resistance
10 The Nature of Concrete It is a composite material Aggregates are 65% - 80% of the volumeFine aggregate: sandCoarse aggregate: stoneCement: General term & applies to any binderPortland cementfly ashground slagsilica fumeWater
12 The Purpose Of The Aggregates Large aggregates:provide density (fill space)provide strengthFine aggregates:fill small voids between large aggregatesIncreases strength of the cement binder
13 The Cement Matrix Cement: Water produces a crystalline structure binds aggregates togetherWatercauses chemical reaction to occurwater/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
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 bondsHydration begins as soon as water meets cementRate 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” airLarge bubblesLarge voids are undesirable for durability & permeabilityEntrained airBubbles are microscopic in size & distributed through out concreteIncreases durability by providing “escape route” for freezing water as it expands