Sustainability

1. Sustainability Definition: Meeting the needs of the present without compromising the ability of future generations to meet their own needs.

2. Sustainability ASCE: Sustainable development is the challenge of meeting human needs for natural resources, industrial products, energy, food, transportation, shelter and effective waste management while conserving and protecting environmental quality and the natural resource base essential for future development.

3. Sustainability Thomas Jefferson (1789): The earth belongs to each of these generations during it's course, fully, and in their own right. The second generation receives it clear of the debts and encumbrances of the first, the third of the second and so on. For if the first could charge it with a debt, then the earth would belong to the dead and not the living generation. (emphasis added)

4. Resources that are being depleted • Land • Fossil fuels • Food • Clean water (aquifers) • Clean air • Arable land • Etc.

5. What can we do as structural engineers? • Structural Systems – particularly methods of construction • Minimize the impact of the construction process on the environment • Minimize contact with the ground (reduce footings, foundation size, etc.) • Design for deconstruction • Material Selection • Understand environmental costs to manufacture materials • Maximize lifespan/cost ratio – depends on initial environmental load of the material vs material life • Select materials that can be recycled

8. Structural Systems – Example: Linn Cove Viaduct • One of the most complicated concrete bridges ever built • Constructed from 1979 – 1982 ----- Cost: $9.8 million • Part of the Blue Ridge Parkway in North Carolina • Snakes around Grandfather Mountain • 1,243 ft long comprised from 153 weighing 50 T each

9. In order to protect the environment under the bridge, the structure was built as a unidirectional continuous cantilever. • Segments of the bridge were cast 1 mile away and brought in using the constructed road deck. • Most construction activities, equipment, and personal were restricted to the deck of the bridge.

10. Unidirectional Cantilever Design – Design Implications Direction of Construction Negative Moment Positive Moment

13. The greatest challenge of the bridge was geometry control. No two segments of the bridge were alike. The bridge had three sequential horizontal curves, and changes in super-elevation that had to be cast into each segment.

14. Materials: • Concrete • Masonry • Steel • Timber • Exotic Materials (composites) • Natural Materials

15. Concrete • Components of Concrete: • Cement (8-15%) • Water (2-5%) • Aggregates (~80%) • Fine (sand) • Coarse (rock) • Admixtures (0.1%) High Cost, High Environmental Impact Strength Filler Manipulation of Fresh Properties

16. Calcium Silicate in the cement reacts with water to form Calcium Hydroxide Crystal or Calcium Silicate Hydrate

17. 100% 75% 60% 40%

18. Preheater Gases from Kiln used to heat Raw materials Filter Bag Dust removed from kiln exhaust 1000o C Limestone Melts into burnt lime 2000o C Fusion into calcium silicate crystals “clinker” Mixing Bed Crushed Limestone and Clay Cooler Goes to grinder after this Rotating Kiln Cooking and mixing of the raw materials Raw Mill Grinding into powder

19. Worldwide cement production produces ~7% of CO2 emissions. 50 – 60% of the CO2 produced comes from calcination of limestone 40 – 50% of the CO2 produced comes from fuel combustion Calcination: CaCO3 (limestone) + Heat  CaO (quick lime) + CO2

22. Cement Clinker

23. Grinder

24. Inside the Grinder

25. Every ton of cement produced creates about 0.9 tons of CO2 emissions What can be done to reduce this? • Use energy efficient production methods: • dry kilns vs wet kilns • horizontal kilns vs stacks • Use recycled materials for fuel • Add pozzolanic materials with clinker in the grinding process to make blended cements

27. We can also reduce how much cement we use in our concrete: • Concrete strength depends on water/cement ratio • Fresh concrete fluidity depends on water content • To create a fluid, yet strong mix, high cement content must be used • Reduce the water requirement (and thus cement requirement) by using admixtures to achieve fluidity

28. Cement production also creates large amounts of mercury emissions: • Mercury is present in the raw materials (limestone) and many of the recycled fuels used to fire the kiln. • Cement production creates about 8% of Canada’s mercury emissions. • The U.S. only recently set limits on mercury emissions which won’t fully take effect until 2013.

29. Ash Grove Cement Plant in Durkee, Oregon The single worst source of Mercury emissions in the U.S. 2,582 pounds reported emission in 2006. Cement Factories in the U.S.

30. Formwork

31. Formwork – Re-usability • Use repetition of structural shapes and sizes • Use metal or plastic forms which have longer life than wood • Use construction grade lumber which is more durable and can be re-used more often • Use non-toxic form release agents to prevent damage to the form surface • Use formwork connections / attachments that are easily disassembled with no damage to the form material

32. … or use stay-in-place forms Steel decking acts as tension reinforcement for the bottom of a concrete slab

33. Polystyrene Foam acts as exterior insulation for basement concrete basement walls

34. … or use precast concrete

35. Masonry Concrete Masonry Units (CMU) Useful for load bearing elements such as shear walls Brick Used primarily for façades, but can be used for load bearing elements

36. Ancient Masonry Pre-Sumerian Civilization Mesopotamia ~6,000 BC beehive domes

37. Masonry – Typical Construction

38. Clay Masonry - Recycling

39. Autoclaved Aerated Concrete (AAC)