Materials and the Environment (L1): 1. In your own words describe what “Sustainability” means. Name one tool that we have used to quantify (measure) sustainability and describe it in few sentences.
-Ability to satisfy the basic needs of today without compromising the ability of the future generations to satisfy their needs. (L1 S8)
-Characteristics of a process that can be maintained at a certain level indefinitely
-Ability to sustain a way of life indefinitely
-To only utilize nature’s resources at a rate which they can be replenished naturally
-Resources are not limitless Can we grow indefinitely? (L1 S9)
-Measured by: cost, time, maintenance, reuse/recycle, resource consumption (L1 S12)
-Tool- Life Cycle Assessment (L1 S12)
-LCA is to determine the TOTAL cost, energy, consumption, eco-impact, of a structure over its entire life cycle:
Material production, transportation, construction, in service(+maintenance), end of life (disposal or reuse) (L1 S13) -Life cycle cost and societal costs are calculated using similar principles. (S13) 2. What does “Resilience” mean in the context of civil infrastructure?
Infrastructure’s ability to resist effects of the environment and rebound back to its normal state. (ex. Earthquakes, etc.) 3. By giving an example, explain how a material (e.g., steel panels used in automobiles) impacts the environment and our energy consumption during its service life.
Concrete production- during production CO2 is released into the environment from energy use. Service life only requires maintenance with minimal energy consumption. (ex. Personnel to wash off salts, etc.) 4. What is the embodied energy (materials production and processing) of an aluminum soda can weighing 100g? How many 32W compact fluorescent light bulbs can be lit for 1hr using the same amount of energy? Assume energy conversion efficiency (fossil fuels to electric) of 100%.
Al from ore:
Embodied energy: 210 MJ/kg
Processing energy: 11.6 MJ/kg
(100g/1000)=0.1kg x (210 + 11.6)MJ/kg = 22.16 MJ
22.16E6 J/(3600sec)= 6155.6 W
6155.6W/32W=193 light bulbs 5. I’m a concrete sales person and I’m here to sell you a new “Sustainable” concrete. What types of information would you need to assess my claim regarding sustainability of my product?
-Is raw material extraction balanced with available resources?
-How much energy is consumed during production and processing?
-How much CO2 per unit mass is released during production?
-Is there any additional maintenance required?
-What is the end of life process? Is it recyclable, able to be reengineered? 6. Approximately 86% of the world’s current energy needs are supplied by fossil fuels. Name three main sources of fossil fuels. Do all three result in CO2 emission? Which one is the most and which one is the least CO2 intensive on a per 1MJ output energy basis (you may need to review Lectures 6 and 7 to answer the last question).
3 sources of fossil fuels- coal, oil, & natural gas
Yes, all emit CO2
Coal- 0.088 kgCO2/MJ Most
Gasoline- 0.065 kgCO2/MJ (TABLE 6.8 p140)
LNG- 0.055 kgCO2/MJ Least 7. Sustainability is sometime described through a “triple bottom-line” concept. Name these 3 main pillars of sustainability and provide an example for each pillar.
Profit- corporate profit
People- a measure in some shape or form of how socially responsible an organization has been throughout its operation
Planet- measure of how environmentally friendly it has been (p322) 8. What does “infrastructure” mean? Name 4 different infrastructure sectors.
The underlying foundation or basic framework
The basic equipment and structures that are needed for a country, region, or organization to function properly.
Sectors- Chemical, communication, energy, transportation 9. What are 3 strategies to make more sustainable materials for construction and infrastructure?
-Use higher recycling content
-Increase strength to reduce mass (cut transportation costs)
-Reduce embodied energy in production and manufacturing (alternative processing) 10. We have over 5200 structurally deficient (SD) bridges in Pennsylvania. What does this mean?
-More jobs for Penn State civil grads!
-They need to be replaced efficiently while maintaining long service life
Growth, Reserves, and Resource Criticality (L2,3): 11. The size of a country’s economy is often measured in terms of its GDP. What is GDP?
How is GDP related to an economic recession?
Gross domestic product
= consumption + investment + gov. spending + (exports-imports)
In an economic recession GDP slows down or decreases (L3 S) 12. To reduce the national debt, the federal government decides to cut government spending by 20% across the board. What is the direct impact of this action on the GDP (i.e., would GDP go up or down)? Use your economic imagination and elaborate in few sentences.
By looking at the formula it would appear that the GDP would go down due to a decrease in government spending. This does not necessarily mean that consumption, investment, and exports can’t go up. But most likely GDP would decrease. 13. What does the “Rule of 70” predict?
The number of years it take a certain variable to double. The rule of 70 states that in order to estimate the number of years for a variable to double, take the number 70 and divide it by the growth rate of the variable.
Growth rate R=5% (use 5 not 0.05) n=70/R = 70/5 =14 years 14. What does the index of exhaustion of a resource (e.g., crude oil) mean and what is the difference between static and dynamic index of exhaustion?
Predicting when something will run out
Static- predicts resource life but ignores growth: tex,s=R/P R=metric tons ; P=metric tons per year
Dynamic- predicts resource life in regards of growth tex,d=(100/r)ln{(rR/100P)+1} 15. Why have static and dynamic indices of exhaustion not been able to accurately predict the remaining time until we run out of a particular resource (e.g., copper ore)?
A comfort zone exists for the value of the index. Only when it falls below this value is there sufficient incentive to prospect for more. (p36)
You should be able to calculate energy efficiency based on a chain of energy conversion and transmission steps (book: figure 2.9).
Exam 1 Question 3
16. The approximate energy conversion efficiency of natural gas to electric is 38%. How many MJ of gas energy must be used to supply 1kWh of electricity?
3.6MJ=1kWh
(3.6MJ)(0.38)+(3.6)=4.97MJ 17. Explain the difference between “Reserves” and “Resource Base”. Explain why Reserves can grow or shrink by improved technology, environmental legislation, change in demand, and change in price.
Reserve- the part of a mineral’s deposit that can be extracted legally and economically at present time.
- It is the currently accessible amount NOT the total present
-Dynamic quantity: grows and shrinks as technical, economic, legal conditions change
Resource Base- The real amount of that total material in the earth
-fixed quantity much larger than reserves
-its value is not known with certainty
(L3 S6) 18. If you are given the Crossover graph of Discovery vs. Consumption of a resource (e.g., Figs. 2.17 or 2.18 of the book), you should be able to explain what the graph means and what is the significance of the crossover point.
-At first reserves are growing due to increased prospecting and improved extraction technology
-Initially rate of production (exploitation) is less than rate of discovery so we sleep easy
-There comes a point that finding the new reserves or improving technology becomes difficult, so the rate of discover peaks and starts to fall
-Then production rate surpasses the discovery rate.. Trouble!
-Prices rise
(L3 S9) 19. Name the three most abundant material ores in the earth’s crust.
Oxygen, silicon, aluminum 20. You should be comfortable with problems involving exponential growth such as those solved in class or in HW1 and Quiz1.
End of First Life (L4): 21. By providing examples, list some of the factors that would determine a product’s end of first life.
Physical life, functional life, technical life, economical life, legal life, loss of desirability
(L4 S4) 22. Name and describe 5 options available in dealing with materials at the end of their life.
Landfill, combustion, recycling, reengineering, reuse (L4 S2) 23. What are some of the factors that are considered during the design of a modern landfill?
Space availability, weather and climate, leachate and smell control, methane collection 24. Name some of the challenges associated with recycling.
Collection, transportation, processing (separation, washing, cleaning) (L4 S20) 25. Name some of the challenges associated with incineration of solid waste for energy recovery.
Needs separation of combustibles, toxic fume and residue control, moisture(makes less efficient), economics are unattractive (L4 S14) 26. What is the difference between pre- and post-consumer recycling?
Pre- post industrial, materials recycled within manuf. plant
Post- glass, lumber, brick, concrete from demomore difficult
(L4 S18) 27. Practice numerical problems on contribution of recycling to current supply.
LCA Basics (L5): 28. Explain and illustrate with a simple diagram what life-cycle assessment means.
Refer to lecture and Chapter 3 29. Think of a fairly simple product (e.g., your bicycle). Name typical resources consumed and emissions excreted during the life-cycle of this product.
CO2 emitted during steel production
Fossil fuels used for energy for manufacturing process
No emissions or consumption during service life 30. Using an example, describe the importance of clearly identifying the system boundary when performing an LCA study.
It is important to set boundaries because you need to only include what you are focusing on. (p.54-55)
31. What are the four main steps in a full LCA based on ISO 14040? Describe each in few sentences. 1. Define goals and scope 2. Inventory compliance 3. Impact assessment 4. Interpolation
(L5 S7) 32. When comparing alternative products, what does a “functional unit” mean? Give an example.
Unit that an item can be represented by (ex. Gas tank=gallons) (L5 S9) 33. What is the main difference between full LCA and Eco-audit? Why may eco-audit be preferred as a design tool?
Eco audit only studies one resource (energy) and one emission (CO2) 34. Make an engineering judgment on which phase of life is more likely to be the most energy intensive for an airplane, computer monitor, parking garage, etc.
Material processing 35. You should be able to sketch simple LCA flowcharts for different products: e.g., an office chair, an automobile, a cell phone, etc. 36. Review HW2 and Quiz2.
Eco-data of Materials (L6,7): 37. Explain how the energy to produce a material from ore is estimated.
Eco property of embodied energy – enthalpy change
(L6 S7) 38. The average embodied energy of aluminum production from ore (bauxite) is 220MJ/kg with the standard deviation of 20 MJ/kg. What are some of the sources of inaccuracy in this data?
Extraction, transportation, heat lost in furnace, energy lost in scraps
(L6 S7) 39. Study several numerical examples solved during Lectures 6, 7. 40. Carefully study tables provided during chapter 6 of the book. You will need to know how to use them during the exam. 41. What is kWh?
Kilowatt-hour = 3.6MJ 42. What is meant by the “Electric Energy Mix of a country”?
Mix of different sources of energy used in a country (Table 6.8 p141) 43. Looking at the book’s table 6.8, why is there a big variability in the MJ of fossil fuel energy needed to produce 1kWh of electricity from one country to another (e.g., China vs. France)?
Nation’s access to fossil fuels, legislation, etc. 44. You should be able to browse through and extract information from chapter 15 of the textbook (or the Excel database on ANGEL) . 45. What are the factors that determine the energy and CO2 associated with transport/shipment of products.
Modes of transportation (Table 6.9 p142) 46. Review HW3 and Quiz3.
Eco-audits (L8,9): 47. In an eco-audit, the recycling phase can result in a potential end of life (EoL) credit. Why?
Recycling exceeds manufacturing energy 48. You should be familiar with the two methods that can be used to assign recycling credits.
Method 1:
Beginning of Life: R*HRC+(1-R)Hm
End of Life: (1-r)Hd
Method 2:
Beginning of Life: Hm
End of Life: r(Hrc-Hm)+(1-r)Hd
(L9 S3,4) 49. Given sufficient information, you should be able to calculate energy consumption and CO2 emission in each life phase of simple products. Review the 3 examples solved in class during Lectures 8,9: plastic bottle, car bumper, concrete beam. Also, check the case studies in chapter 8 of the book as well as problems at the end of this chapter. 50. You should be familiar with the concept of breakeven point. See car bumper problem in Lecture 9. 51. While performing an eco-audit, what is the need for a “proxy material” and “proxy process”?
Account for components making up 95% of the mass of the product
For the remaining 5% use a generic (proxy) material
(L8 S5) 52. Review HW4 and Quiz4.
Life Cycle Cost Assessment (L10): 53. What does LCCA mean?
Life Cycle Cost Analysis- Studying and tracking a material (or a product or process of structure) during its entire service life and documenting the economical impacts.
(L10 S2) 54. You should be able to sketch a simplified flowchart of life phases for a given product (e.g., an electric space heater) and identify some cost items related to each life phase. 55. You should be able to explain the components of direct and indirect costs. 56. You should be able to calculate the present value of future costs. Review example on slide 8. 57. What are the factors that determine the discount rate?
Rate = cc + fr + pi cc: “real” opportunity cost of capital fr: premium for financial risk pi: price inflation
(L10 S9) 58. What does the “scope of analysis” mean? What is meant by the “residual value”?
Scope of analysis mean what you are analyzing
Residual value 59. Review the bridge LCCA example solved in class. Make sure you are comfortable with all calculations. 60. Explain these terms and their differences: The agency cost, The users cost, and The vulnerability cost.
Agency cost-design, engineering, construction, maintenance, etc.
User cost- traffic delays, accidents, environmental damage
Vulnerability cost- overload, fatigue, collision damage, natural disaster damage, etc.
(L10 S18-21) 61. How is the annual vulnerability cost calculated?
Accident reports 62. What are some of the important factors that are included in calculation of the users cost?
Traffic delay cost (L10 S19)
Strength of Materials Review (L11): 63. You should be comfortable with concepts and definitions of stress, strain, Poisson’s ratio, Hook’s law, elastic modulus, yield strength, ultimate strength, ductility vs. brittleness, measures of ductility, fracture toughness. You also need to know the proper units for each of these parameters.
-Stress-force per unit area (psi)
-Strain-amount of elongation or compression that occurs at a given stress or load (in/in)
-Poisson’s ratio-ratio of the proportional decrease in a lateral measurement to the proportional increase in length in a sample of material that is elastically stretched
(unitless)
-Hooke’s law-principal that states that the force needed to extend or compress a spring by some distance is proportional to that distance
-Elastic modulus-the ratio of the force exerted upon a substance or body to the resultant deformation (psi)
-Yield strength-material property defined as the strength at which the material begins to deform plastically. (psi)
-Ultimate strength-tensile strength, maximum stress that a material can withstand before breaking (psi)
-Ductility-in tension material can be stretched into wire
-Brittleness- do not stretch into wire
-Measures of ductility-fracture strain, strain at which a test specimen fractures during uniaxial tensile test. Another commonly used measure is the reduction of area at fracture
-Fracture toughness-ability of a material containing a crack to resist fracture (psi*sqrt(in)) 64. You should be able to determine the neutral axis and moment of inertia of a given cross section/area (including non-symmetric areas). 65. You should be able to sketch shear and moment diagrams for simple beam problems. 66. You should be able to calculate the magnitude and determine the location of maximum flexural stress in a simple beam in bending. 67. Review HW5 and Quiz5.
Eco-selection of Materials, Materials Indices (L12-13):
For simple materials selection problems, you should be able to: 68. Identify the problem’s constraints, objectives, and free variables. 69. Derive the relevant material index to minimize mass, volume, cost, or embodied energy. 70. Select the best material candidates (i.e., make a short list) using a given bar chart. On the exam you won’t need to construct a bar chart but you will be given few materials in a table and you need to determine which material is the best for the given application. 71. Calculate the scaling factors (e.g., how heavier your beam will be if you go with the second best material instead of the best material choice?) 72. Practice problems at the end of chapters 9 and 10 of the book. 73. Practice HW6 and Quiz6.
Efficient Shapes (L14-15): 74. You should be able to calculate the moment of inertia (I) of different cross sections (rectangle, ellipse, pipe, box, etc.) using Tables 11.2 and 11.3 of the Materials Selection book (also provided in class). 75. You are expected to know the definition of section modulus (Z) and be able to calculate the section modulus based on moment of the inertia (I). 76. You should be familiar with the definitions of stiffness shape factor () and strength shape factor (). You should be able to calculate these shape factors for any given cross section when you have values for moment of inertia (I) and section modulus (Z). 77. Practice with Efficient Shapes: Problem Type 1 78. Practice with Efficient Shapes: Problem Type 2 79. Practice with Efficient Shapes: Problem Type 3 80. Provide example of how micro-shaping can improve mechanical properties of materials. 81. Is there a limit to shape efficiency? Why? 82. Practice HW7 and Quiz7.
Durable Concrete (L16-17): 83. What are the typical environmental impacts associated with the production, use, and disposal of portland cement concrete?
Production is energy intensive and released CO2 (L16-17 S9) 84. Name and explain 3 categories of methods to make more sustainable concrete. 1. Improve durability- less repairs, less costs, less energy/resource use, less emissions 2. Greener materials- reduced embodied energy/CO2, recycled ingredients 3. Improve design- less materials 85. Name four major durability problems of concrete in the order of significance and prevalence. Explain the simplified mechanism of each problem.
Freeze thaw damage, steel corrosion-leads to cracking and spalling, alkali-aggregate reaction- reaction which occurs over time in concrete between the highly alkali cement paste and non-crystalline silicon dioxide which is found in common aggregates
Sulfate attacks (DEF)- water containing dissolved sulfate penetrates the concrete.
DEF- delayed ettringite formation occurs in concrete which has been cured at elevated temperatures. DEF causes expansion due to ettringite formation within paste 86. Why does corrosion of reinforcing steel often result in cracking and spalling of cover concrete?
Rust occupies a great volume. The expansion creates tensile stresses in the concrete which eventually causes cracking, delamination, and spalling 87. Explain how corrosion, alkali-silica reaction, or freeze-thaw damage can be mitigated in new concrete construction.
Reduce chloride and moisture penetrability of concrete (smaller w/c), use larger rebar cover depth, prevent cracking (by shrinkage), use corrosion inhibiting admixtures, use corrosion resistant steel
Recycled Concrete Binders (L18): 88. What are the 4 main oxides present in Portland cement? How is Portland cement different than lime cement? 89. Write down formula for reaction of Portland cement with water. Identify the reaction products and mention which one is desirable and which isn’t, and why. 90. Write down formula for pozzolanic reaction of SCMs in concrete. 91. What is pozzolan? Why do we want to use pozzolans in concrete? 92. How is GGBFS produced? 93. Why is BFS air granulated and why is it subsequently ground? 94. Are there slags other than GGBFS? Can they be used as a replacement for portland cement in concrete? 95. Where does fly ash come from?
Sample Equation Sheet
Exponential growth: Rule of 70:
Cumulative production:
Indices of exhaustion:
Contribution of recycling to today’s supply:
Parallel axes theorem: IRef=IN.A.+Ad2
Beam theory:
For type II problem of Efficient shapes:
