In the construction of any project the are many factors one must consider when choosing materials other than just strength and availability. One must take into consideration the weight to strength ratio, the flexibility/rigidity, the workability, and the waste properties of the chosen materials. Today we will talk about the waste properties of the materials available for our Bridge construction assignment.

Students will be able to chose materials for their projects based on issues of environmental impact as well as for the availability and strength factors

Students will be able to slate materials into one of three categories in the recycle triangle

Students will have a broader understanding of material properties

Major Message – We as manufacturers MUST Recycle, Re-use, and Reduce

Start by introducing the framework by which the materials will be selected. Then move on to the major message for today’s topic (Recycle and waste management)

On the Board have the recycle triangle and ask what the three R’s of the triangle are.

Read through the procedures

Use the overhead to categorize the three materials into the recycle triangle.

After all materials have been categorized ask questions on each material

Read conclusion to wrap all the materials back together

Overhead projector

Overhead transparencies

Chalk Board

Samples of wood, Plastic, and metal

Read Introduction

Introduce the three R’s Triangle for recycling

Last class we went over the design brief of the bridges that we will be making for the next assignment

One of the main considerations before starting design is Material selection.

In the context of recycling we have to consider where these materials come from and what to do with the waste by-products

The three major material choices are WOOD, METAL, and PLASTIC.

As you remember the only constraints that I have imposed is that your bridge will be weighted, and the weight it supports will be divided by this figure.

\ The structure should incorporate many of the lighter construction materials as well

Lets look at the properties of each of the materials and how they impact on the recycle triangle.

Use overhead to layout the properties of WOOD, METAL, and PLASTICS

After going through the overhead/handout ask questions about Material categories and why.

Read conclusion to tie all together.

The social content of this demonstration is to get students to look at the materials they are using in a broader sense. All the materials are going to yield a certain amount of waste but if we can reduce the unusable waste and work with the recyclable waste then perhaps the world will be better off.

What is the type of plastic that is reusable?

Why are metals easily recyclable?

Where does wood fit into the Green triangle?

So after introducing the ecological aspects of the different materials does it make a difference what you make your bridge out of? I think that when choosing the materials to construct your bridge you must take into consideration more than just the strength of the materials. You should also take into consideration the strength of their impact on the environment.