TED 316 – Structural Design

1. Construction Materials Concrete & Masonry TED 316 – Structural Design

2. Been used since the Roman Empire Key event in the history of architecture Termed the Roman Architectural Revolution Similar to modern concrete and nearly as strong Did not have reinforcing steel so could not resist tension Often used as core with masonry cladding Concrete

3. Man-made material • Composite consisting of: • Cement (commonly Portland Cenent) • Aggregate • Coarse – gravel or crushed rocks • Fine – usually sand • Water • Chemical admixtures • Mineral admixtures • Reinforcement Concrete

4. Solidifies and hardens after mixing with water Chemical process known as hydration Exothermic reaction (gives off heat) Tremendous compression strength Poor tension strength Wide range of uses Most used man-made material on earth Huge economic impact Concrete

5. Processes vary with available technology • Mixing concrete • Thorough mixing essential • Traditional mixing • Separate paste mixing • Workability • Ability of a fresh mix to fill a form • Measured by the concrete slump test Concrete Production

6. Curing • Determines strength and hardness • Moist and controlled temperatures needed • Sets quickly to become rigid • First three days are most critical • Too rapid curing causes tensile stress and cracking • Ponding to control curing process • 90% of strength in about three weeks • Strengthening may continue for decades Concrete production

7. Compression strength – very high • Tensile strength – much lower • Need for reinforcement • Coefficient of thermal expansion – very low • Cracking • Shrinkage cracking • Tension cracking • Creep Concrete properties

8. Carbon dioxide emissions • 2nd largest industry producer of CO2 • Up to 5% of worldwide man-made emissions • Sources include: • Thermal decomposition of calcium carbonate produces lime and carbon dioxide • Large use of energy – primarily fossil fuels Concrete environmental and health issues

9. Surface coverage – 30-40% in large cities • Surface runoff • Soil erosion • Flooding • Urban runoff (oils, heavy metals, trash, etc.) • Urban heat • Light colored concrete reflects 50% more light than asphalt • Good in summer bad in winter Concrete environmental and health issues

10. Concrete Dust • Biggest concern during demolition or natural disasters • Toxic and radioactive contamination • Handling precautions • Skin contact with wet concrete = chemical burns • Protect eyes, hands and feet • Wash without delay • Gangrene type symptoms Concrete environmental and health issues

11. Durable building material • Superior fire resistance • Long service cycle • Good energy efficiency coefficient • Transportation to site • Construction process • Lifetime of project • Earthquake safety – if reinforced Why use concrete