Properties of Concrete Design and Control of Concrete Mixtures

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

Overview Freshly Mixed Concrete Hardened Concrete

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

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

Workability

Workability

Consistency

Rheology

Bleeding and Settlement

Bleeding and Settlement

Bleeding

Bleeding and Settlement

Bleeding

Air Content

Air Content

Air Content

Air Content

Air Content

Air Content

Air Content

Air Content

Air Content

Air Content

Air Content

Air Content

Air Content

Uniformity

Hydration, Setting, and Hardening

Setting and Hardening

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

Curing

Curing

Drying Rate

Drying Rate

Drying Rate

Drying Rate

Strength

Strength

Strength

Strength Flexural strength – 0.7-0.8 times sq. root of compressive strength in MPa (7.5-10 for psi) Direct tensile strength – 8%-12% of compressive strength Torsional strength – related to flexural strength and dimensions Shear strength – related to compressive strength (ACI 318) Modulus of elasticity – typically 1-4 GPa

Density

Permeability and Watertightness

Permeability and Watertightness

Volume Stability and Crack Crontrol Volume changes due to temperature, moisture, stress – 0.01%-0.08% Thermal behavior similar to steel Elastic deformation and creep Cracking due to load or volume changes Reinforcing steel used to reduce crack widths

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

Aesthetics

Summary Freshly Mixed Concrete Hardened Concrete

Questio ns ?