Tire Rubber Pyrolysis for Concrete Filler

ISEF Category: Environmental Engineering

Subcategory: Recycling and Waste Management  ·  Difficulty: Advanced  ·  Setup: University Lab  ·  Time: Full Year

The Hook

Old tires do not vanish. They pile up, burn poorly, and keep taking up space. Pyrolysis can turn rubber waste into char, oil, and gas instead of letting it sit in a landfill. You can test how the heating profile changes char yield and whether that char can act as a concrete filler.

What Is It?

Pyrolysis means heating material with little or no oxygen so it breaks apart instead of burning. For waste tire rubber, that can produce char, which is a solid carbon-rich residue, plus liquids and gases. Think of it like cooking something in a sealed pan until it changes into several new products, not just ash.

Your project asks two questions at once. First, how do different heating profiles change how much char you get? Second, does that char work as a filler in concrete? A filler is a small solid added to a mix to change packing, strength, texture, or durability. If the char acts like a useful additive, it could turn a waste stream into a building material input.

Why This Is a Good Topic

This makes a strong science fair topic because you can vary clear inputs, measure clear outputs, and connect your results to a real waste problem. Tire waste is huge, and concrete is one of the most used materials on Earth, so even a small improvement matters. You can learn thermal processing, materials testing, data analysis, and how to compare a waste-derived material against a standard filler.

Research Questions

• How does heating profile affect the char yield from waste tire rubber?
• What is the effect of peak heating rate on char mass, appearance, and particle size?
• Does char from tire rubber change concrete compressive strength compared with a control mix?
• To what extent does tire-derived char change water absorption in concrete samples?
• Which char preparation method gives the best balance between yield and concrete performance?
• How does the amount of tire char added affect workability and setting behavior in concrete?
• To what extent do different tire feedstock types change char yield and filler performance?

Basic Materials

• Waste tire rubber feedstock from a controlled source or pre-cleaned tire chips.
• Small closed steel can or sealed pyrolysis vessel approved by a mentor.
• Ventilated heat source approved for the setup, with fire-safe surroundings.
• Digital balance with 0.01 g or better resolution.
• Metal tongs and heat-resistant gloves.
• Nonflammable trays, crucibles, or sample holders.
• Sieves or mesh screens for particle sizing.
• Concrete mix components for small test cubes or cylinders.
• Molds for standardized concrete specimens.
• Compression test access through a school, maker lab, or mentor site.
• Drying oven or desiccator for consistent sample conditioning.
• Digital caliper for specimen dimensions.

Advanced Materials

• Tube furnace or muffle furnace with controlled temperature programming.
• Gas-tight reactor or closed steel can rated for mentor-supervised pyrolysis.
• Inert gas supply if your approved setup requires oxygen exclusion.
• Crucibles, boats, and high-temperature sample holders.
• Analytical balance with 0.001 g resolution.
• Sieve shaker for char fraction sizing.
• Concrete mixer and standardized molds for test specimens.
• Compression testing machine.
• Scanning electron microscope for char surface imaging.
• X-ray fluorescence or X-ray diffraction access for ash and mineral analysis.
• Thermogravimetric analyzer for thermal behavior.
• Universal testing machine for flexural or split tensile testing.

Software & Tools

• Excel: Organizes yield data, concrete test results, and summary statistics.
• Google Sheets: Tracks samples, labels runs, and builds simple charts.
• R: Runs statistical tests and compares heating profiles across groups.
• ImageJ: Measures particle size and compares char texture from photos.
• GeoGebra: Helps graph trends and fit curves when you compare process variables.

Experiment Steps

1. Define the exact process variable you will change first, such as heating profile, and keep every other condition fixed.
2. Choose how you will measure char quality, not just char mass, so your outcome is more than a yield number.
3. Plan a concrete testing matrix that compares a control mix with several char loading levels.
4. Build a sample naming and drying plan so moisture does not blur your strength and absorption data.
5. Decide which measurements will tell you whether the char helps or hurts the concrete, such as density, workability, absorption, and strength.
6. Map out the statistics before you start so you know how you will compare runs, replicates, and controls.

Common Pitfalls

• Treating the pyrolysis step like a simple burn, which destroys the sample and changes the meaning of the char yield.
• Mixing char from different tire sources together, which makes it hard to link results to one heating profile.
• Skipping particle sizing, which creates uneven concrete filler behavior between batches.
• Testing concrete before samples reach a consistent dry state, which skews strength and absorption results.
• Using too few replicates, which makes small differences look bigger than they really are.

What Makes This Competitive

A strong version of this project does more than report that char exists. It compares multiple heating profiles, quantifies char properties, and links those properties to concrete performance with proper controls. You can raise the level by testing more than one concrete metric, using a clear statistical plan, and connecting structure, yield, and function in one story. That turns a waste study into a materials engineering project.

Project Variations

• Test how char particle size changes concrete strength and water uptake.
• Compare tire-derived char with char from another waste polymer or biomass source.
• Study how pre-washing or sorting tire feedstock changes char yield and ash content.

Learn More

• NOAA Marine Debris Program: Background on waste plastics, rubber pollution, and material recovery ideas, found through NOAA's main site.
• USGS Publications Warehouse: Search for review articles on tire-derived carbon, pyrolysis products, and environmental reuse.
• PubMed: Search for review articles on tire pyrolysis, char properties, and cement or concrete applications.
• NASA NTRS: Search for materials processing papers that explain thermal decomposition and characterization methods.
• MIT OpenCourseWare: Find free materials science and environmental engineering course notes that cover thermal decomposition, ceramics, and composite design.
• Cement and Concrete Research: Search this journal for studies on alternative fillers, carbonaceous additives, and concrete property testing.