Properties of Concrete Design and Control of Concrete

Overview n Freshly Mixed Concrete n Hardened Concrete

Properties of Concrete n Fresh properties n Hardened properties n Consistency n Strength n

Freshly Mixed Concrete n Plastic or semi fluid---pliable and capable of being molded n

Hardened Concrete Properties n Curing n Drying rate n Strength n Density n Permeability

Strength n Flexural strength – 0. 7 -0. 8 times sq. root of compressive

Volume Stability and Crack Crontrol n Volume changes due to temperature, moisture, stress –

Durability n Ability to resist weathering, chemicals, and abrasion n More exposure variety than

Summary n Freshly Mixed Concrete n Hardened Concrete

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Properties of Concrete Design and Control of Concrete Mixtures – Chapter 9

Overview n Freshly Mixed Concrete n Hardened Concrete

Properties of Concrete n Fresh properties n Hardened properties n Consistency n Strength n Stability n Durability n Uniformity n Appearance n Workability n Economy n Finishability

Freshly Mixed Concrete n Plastic or semi fluid---pliable and capable of being molded n General must: n Be easily mixed and transported n Be uniform n Have good flow properties n Be compactable n Be segregation resistant n Be finishable

Workability

Consistency

Rheology

Bleeding and Settlement

Bleeding

Bleeding and Settlement

Bleeding

Air Content

Uniformity

Hydration, Setting, and Hardening

Setting and Hardening

Hardened Concrete Properties n Curing n Drying rate n Strength n Density n Permeability and watertightness n Volume stability and crack control n Durability n Aesthetics

Curing

Drying Rate

Strength

Strength n Flexural strength – 0. 7 -0. 8 times sq. root of compressive strength in MPa (7. 5 -10 for psi) n Direct tensile strength – 8%-12% of compressive strength n Torsional strength – related to flexural strength and dimensions n Shear strength – related to compressive strength (ACI 318) n Modulus of elasticity – typically 1 -4 GPa (2 -6 million psi)

Density

Permeability and Watertightness

Volume Stability and Crack Crontrol n Volume changes due to temperature, moisture, stress – 0. 01%-0. 08% n Thermal behavior similar to steel n Elastic deformation and creep n Cracking due to load or volume changes n Reinforcing steel used to reduce crack widths

Durability n Ability to resist weathering, chemicals, and abrasion n More exposure variety than other materials n Most durability concerns involved water in the concrete n Freeze-thaw n Corrosion (chlorides or carbonation) n ASR n Abrasion n Sulfate Attack n Others

Aesthetics

Summary n Freshly Mixed Concrete n Hardened Concrete

Question s ?