Engineering Permeable Concrete

Once students understand how the hydrosphere and the geosphere interact to store groundwater, they use that scientific knowledge in this lesson to engineer a permeable concrete material that solves the problem of flooding in urban environments. 

• Engineers can use scientific knowledge about how aquifers absorb and filter water to design solutions to urban flooding and polluted stormwater.  
• Engineers follow a process to help guide them from a problem to a technology that solves a problem.
• The goal of the scientific process is to answer a question, while the goal of the engineering process is to solve a problem.
• Engineers used permeable pavement to solve the problem of flooding. Permeable pavement is permeable and porous. This allows water to absorb into the ground so it doesn’t collect on the surface, leading to flooding. It also filters the water, filtering out pollutants.  
  
  

• How is the scientific process similar to or different from the engineering process?
• Why is it important for engineers to follow an engineering design process?
• Why do engineers design prototypes before they build the actual technology?
• Why do engineers use data gathered from testing when determining whether to revise or replicate a prototype?
• What problem were engineers in Chicago solving when they designed permeable pavement?
• How did engineers use permeable pavement to solve the problem?  
• What makes a material permeable?
• Which materials are most permeable to water: sand, large gravel, or small gravel?  
  
  

Misconception: The energy that people use does not come from natural resources.

Fact: Energy resources come from the environment, including fossil fuels, wind, water, and solar.

Misconception: Science and engineering are completely separate from each other.

Fact: Science and engineering are interconnected. Engineers use knowledge gained from scientists to design technologies that solve problems. Scientists can then use those technologies to ask deeper questions.

Climate: the average weather over a span of 30 years

Engineer: a person who uses scientific knowledge and mathematics to solve a problem by creating new technologies

Flooding: an event that occurs when water overflows onto land that is normally dry groundwater – the supply of fresh water found beneath Earth’s surface in the pores of soil, sand, and rock

Permeability: the ease with which substances such as water move through a material

Porosity: the number of spaces between particles in a substance

Prototype: a scaled-down first draft of a technology

System: a set of connected, interacting parts that form a more complex whole

Weather:  the conditions of the atmosphere (temperature, humidity, wind speed, air pressure, and precipitation) in a particular place at a particular time

Flooding in Chicago

The city of Chicago, Illinois, has 3,057 kilometers (1,900 miles) of public alleys. Years ago, city planners decided to pave the alleys with regular concrete or asphalt.

However, concrete and asphalt are both impermeable. This means that water cannot absorb into them. Instead, the water remains on the surface.

This creates several challenges. During heavy rains, flooding can occur. Flooding happens when water overflows onto land that is normally dry. In urban areas such as Chicago, the water also often becomes polluted. Finally, less water can absorb into the ground. As a result, aquifers cannot be replenished.

Engineers Solve Problems

Engineers in Chicago decided to come up with solutions to reduce the amount of flooding during a big storm. Engineering is different from science, although science and engineering are connected. Scientists use experiments to gain knowledge. Engineers use that scientific knowledge and mathematics to solve a problem by creating new technologies.

Similar to how scientists follow a scientific process to answer a question, engineers also follow a process. Engineers often follow eight steps to guide them as they create new technologies to solve problems.

The engineering process begins with a problem. In Chicago, the problem was flooding that occurred when heavy rains fell on impermeable surfaces in the city. That flooding turned into stormwater runoff that was often polluted. When engineers are defining a problem, they include the criteria. The criteria are the needs the solution must meet. They also include the constraints. Constraints are ways the solution is limited.

Once they have identified the problem, engineers need to research the problem to find out what is known about the problem. For example, engineers need to know that permeable materials allow water to flow through them easily. They also need to know that some materials filter water better than other materials.

After engineers have researched their problem, they survey the available materials. This survey includes a sketch of the material, as well as how much of the material they have available and the properties of that material.

For example, the Chicago engineers needed to think about the porosity and permeability of the materials they were planning to use.

Engineers then come up with possible solutions for how the problem can be solved with the available materials. Possible solutions to flooding include designing permeable materials that can be used instead of impermeable concrete.

For the hands-on activity in this lesson, students use the engineering process to design a permeable concrete material that solves the problem of flooding in urban environments. Students collect and analyze data on the filtration speed of their prototype, looking for patterns that indicate how well the composition of their permeable concrete solved the problem.