One way to accomplish this is by using a bloomery or a blast furnace see the Additional Multimedia Support section for a link to a blast furnace animation. From pig iron, either "wrought iron" is created by eliminating most of the carbon, or steel is created by eliminating most of the impurities. The many types of steel are called alloys. Concrete is simply a combination of two materials: cement and aggregate. Cement is a powder made of a variety of materials usually certain types of clay and limestone.
When cement is mixed with water a chemical reaction called hydration occurs that causes the cement to harden. Aggregate is a mixture of fine and coarse aggregates. The fine aggregate is typically sand; the coarse aggregate is typically gravel rock. When the cement, aggregate and water are mixed together a hardened mass called concrete results.
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View of fractured surfaces of a concrete core taken from a bridge deck and tested to failure by a huge tensile force. Structural engineers use material properties when designing bridge members. The modulus of elasticity E or Young's modulus of a material is a constant associated with Hooke's Law. The modulus of elasticity indicates the stiffness of a material. Tensile strength is the amount of tensile stress that a material can resist before failing. Compressive strength is the amount of compressive stress that a material can resist before failing.
A material that exhibits ductile properties can be subjected to large strains before it ruptures or fails. A material that exhibits brittle properties shows little or no yielding before failure. Typical stress-strain diagram for steel and concrete. Engineers refer to stress-strain diagrams that graphically display all of these characteristics. In a stress-strain diagram for steel and concrete, the steel curve has a noticeable linear straight region; the slope of this linear region is the modulus of elasticity.
The end points of these curves represent failure. The concrete curve shows a steady increase in strain and stress before it ruptures. Concrete fails with little or no warning; thus, it is considered a brittle material. Just before steel breaks, it experiences a reduction in stress while strain increases. This is seen on the steel curve as the negative sloping section of the curve. When steel fails, it presents some type of warning, typically in the form of large deflections; thus, steel is considered a ductile material.
Watch this activity on YouTube. Think of bridges around your home, and along roadways, bike paths or walking paths that you use. What do the bridges look like? What types of materials were used to construct them? Many types of materials have been used to create modern bridges, including concrete, steel, wood, iron, plastic and stone. Today, we learned that concrete and steel are the most commonly used materials in large modern bridges.
Understanding Tensile Strength and Building Materials
What is an advantage to using steel? Answer: Steel has high strength in both compression and tension. Steel can be bent or shaped easily into different forms. Answer: Concrete can be shaped easily with the use of forms [much like molds]. Concrete is also extremely strong in compression.
How about a disadvantage to steel? Answer: Steel is expensive. Answer: Concrete is very weak in tension.
How to Evaluate Compressive Strength of Concrete | FPrimeC Solutions
Engineers consider all the advantages and disadvantages of materials when deciding which to incorporate into their bridge designs. What are other things that engineers must consider when selecting materials for construction of a bridge? Answer: The strength of the material is usually the most important factor engineers consider. They also think about the cost, availability, speed of construction, and suitability of that material for that particular bridge.
Cement is an ingredient of concrete. Example: Gravel, sand, cement and water were mixed to create our concrete sidewalk. Modulus of elasticity : E Indicates the stiffness of a material. Brainstorming : As a class, have students engage in open discussion. Remind students that in brainstorming, no idea or suggestion is "silly. Take an uncritical position, encourage wild ideas and discourage criticism of ideas. Have them raise their hands to respond. Write their ideas on the board. Ask the students:. The worksheet includes a matching activity to reinforce vocabulary and definitions. The three math problems include solving equations and are of increasing difficulty.
The basic constituents of concrete are cement, water and aggregate.
Assign younger students only the first question. Add the next problem for older students. Assign the third question as a math challenge to advanced students.
- Concrete constituents?
- Modulus of Elasticity in Tension for Concrete and Fibre Reinforced Concrete.
- MPA : Mechanical properties of alkali-activated concrete.
Bridge Alert : Next time students ride in a car or bus, ask them to notice and record on paper the types of materials used in the bridges they cross. Lead a discussion of findings during the next class period. Many types of aggregates — such as sand, gravel, pebbles, glass, vermiculite and rubber - have been used to make concrete. One disadvantage to concrete is that it is weak when a tension force is applied to it and therefore has a very low tensile strength. Concrete has a tendency to crack, and special design precautions are often taken to control the cracking.
Reinforced concrete often has steel embedded in it. Why might there be so many types of aggregates? Discussion points: To achieve different purposes in different applications. Sometimes other materials are added to the concrete mix to give it specific characteristics not typical with plain concrete mixes, making the concrete less brittle, stronger, more durable, a better insulator, or less likely to suffer freeze-thaw damage.
Examples: Incorporate synthetic fibers to improve elasticity, include bits of colored glass for more decorative applications, recycle glass and rubber waste material from recycling collection or old tires. Assign internet research to learn more.
Compressive Strength of Concrete
Lead students in another TeachEngineering activity on the strength of materials, easily relatable to concrete: Engineering for the Three Little Pigs. Watch a four-minute narrated film clip of the wind-induced collapse of the Tacoma Narrows Bridge in Washington in Called "Galloping Gertie," this suspension bridge collapsed four months after it was built. ACI Committee American Institute of Steel Construction, Brain, Marshall. HowStuffWorks, Inc. Accessed October 16, Concrete Basics. Portland Cement Association. EcoSystems — WireBridge Designs.
Ecosystems, Pvt. Hibbeler, R. Mechanics of Materials, Third Edition. Nilson, Arthur H. Design of Concrete Structures, Twelfth Edition.
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However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government. Why K engineering? Find more at TeachEngineering. Quick Look. Grade Level: 8 Lessons in this Unit : 1 2 3 4 5 Time Required: 15 minutes Lesson Dependency Lesson dependency indicates that this lesson relies upon the contents of the TeachEngineering document s listed. Print this lesson Toggle Dropdown Print lesson and its associated curriculum. Curriculum in this Unit Most curricular materials in TeachEngineering are hierarchically organized; i.
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Educators Share Experiences. Summary Students learn about the variety of materials used by engineers in the design and construction of modern bridges. They also find out about the material properties important to bridge construction and consider the advantages and disadvantages of steel and concrete as common bridge-building materials to handle compressive and tensile forces. Engineering Connection When designing structures such as bridges, engineers carefully choose the materials by anticipating the forces the materials the structural components are expected to experience during their lifetimes.
Grades 6 - 8 Do you agree with this alignment? There are systematic processes for evaluating solutions with respect to how well they meet the criteria and constraints of a problem. View other curriculum aligned to this performance expectation. Fluently add, subtract, multiply, and divide multi-digit decimals using the standard algorithm for each operation. Grade 6 More Details View aligned curriculum Do you agree with this alignment?