Volume Changes of Concrete - Portland Cement Association

Volume Changes of Concrete - Portland Cement Association

Volume Changes of Concrete Design and Control of Concrete Mixtures Chapter 10

Overview Early age volume changes Moisture changes Temperature changes

Curling and warping Elastic and inelastic deformation Creep Chemical changes and effects

Volume Changes of Concrete

Many reasons for volume changes Understanding volume changes is useful Restraint of volume changes leads to cracking

Early Age Volume Changes Chemical Shrinkage

Autogenous Shrinkage Subsidence

Vertical shrinkage before initial set Caused by bleeding, escaping air, and chemical shrinkage May be a symptom of lack of

consolidation May lead to cracking over embedments Plastic Shrinkage Cracking

Swelling Moisture Changes of Hardened

Concrete Moisture Changes

Moisture Changes Moisture Changes

Moisture Changes Moisture Changes

Moisture Changes Moisture Changes Effect of

Materials Moisture Changes Effect of Materials

Moisture Changes Effect of Materials

Aggregates restrain shrinkage Second greatest influence behind total water content

Quartz, granite, feldspar, limestone, and dolomite produce lower shrinkage Moisture Changes Effect of

Materials Moisture Changes Effect of Curing

Temperature Changes of Hardened Concrete Concrete expands as temperature rises

Average value about 10 millionths per degree Celsius (5.5 millions per degree Fahrenheit) Range: 6-13 millionths/degree Celsius

(3.2-7.0 millionths/degree Fahrenheit) Temperature Changes

Temperature Changes Temperature Changes Low Temps

Subfreezing volume changes depend on moisture content and behavior, aggregate type

Low temperatures also increase strength of moist concrete---little effect on dry concrete

Temperature Changes High Temps Temperature Changes

High Temps Curling and Warping

Elastic and Inelastic Deformation Elastic/Inelastic

Deformation Poissons Ratio

Shear and Torsional Strain Creep

Creep Creep

Creep Chemical Changes and Effects

Carbonation shrinkage Sulfate expansion

Alkali-aggregate expansion Summary Early age volume changes

Moisture changes Temperature changes Curling and warping Elastic and inelastic deformation

Creep Chemical changes and effects Questio

ns ?

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