Global Eggshell Variability is Negligible for Sustainable Cement Replacement

Why It Matters

This research offers a practical pathway for the construction industry to reduce its environmental footprint by utilizing a readily available waste material. By confirming the uniformity of eggshell properties, designers and engineers can confidently integrate this material into concrete mixes without significant performance compromises.

Key Finding

The study found that eggshells from various parts of the world have very similar properties, making them suitable for use as a partial substitute for cement in concrete. Calcined eggshells performed even better, yielding concrete with strength close to that made with limestone.

Key Findings

• Specific gravity of eggshells varied between 2.02 and 2.39 (average 2.20 ± 0.01).
• CaCO3 content varied between 94.65% and 97.23% (average 96.33%).
• Both uncalcined and calcined eggshells showed acceptable variations in concrete compressive strength.
• Calcined eggshells demonstrated higher compressive strength, comparable to limestone, due to the presence of free CaO and absence of organic matter.
• Variations in basic eggshell properties from different global regions are negligible for use as cement replacement.

Research Evidence

Aim: To assess the suitability of globally sourced eggshells as a sustainable partial cement replacement in concrete by characterizing their physical and chemical properties and evaluating their impact on concrete strength.

Method: Experimental analysis and material characterization

Procedure: Eggshells from sixteen different global origins were collected. Their specific gravity and mineral content (CaCO3) were analyzed using specific gravity tests and thermogravimetric analysis (TGA). Three selected eggshells (highest, medium, and lowest CaCO3 content) were then processed (uncalcined and calcined at 800°C for 3 hours) and used as partial cement replacements in concrete. The compressive strength of the resulting concrete was tested.

Sample Size: 16 eggshell samples, 3 selected for concrete testing

Context: Construction materials, waste valorization, sustainable design

Design Principle

Waste materials with consistent properties can be effectively integrated into new product designs to enhance sustainability and reduce resource dependency.

How to Apply

When designing concrete mixes, consider substituting a portion of Portland cement with finely ground, processed eggshells. The optimal replacement percentage and whether calcination is required should be determined based on desired strength and performance characteristics.

Limitations

The study focused on specific gravity and CaCO3 content; other properties like particle size distribution and pozzolanic activity were not extensively detailed. The long-term durability and performance of concrete with eggshell replacement were not assessed.

Student Guide (IB Design Technology)

Simple Explanation: You can use eggshells from different countries to make concrete stronger and better for the environment because they all have pretty much the same useful stuff inside.

Why This Matters: This research shows how a common waste product can be repurposed to create better, more environmentally friendly building materials, which is a key goal in sustainable design.

Critical Thinking: To what extent does the 'organic part' and 'porous structure' of eggshells, mentioned as reasons for lower CaCO3 than pure limestone, impact their long-term performance and durability in concrete under various environmental conditions?

IA-Ready Paragraph: This research by Maqsood et al. (2023) demonstrates that eggshells from various global origins exhibit consistent specific gravity and calcium carbonate content, making them suitable for sustainable partial replacement of cement in concrete. The study's findings suggest that the variability in eggshell properties across different regions is negligible, enabling designers to confidently incorporate this waste material into construction projects to reduce environmental impact and potentially improve material performance, particularly when calcined.

Project Tips

• When sourcing materials for your design project, consider waste streams that have consistent properties.
• Investigate the chemical and physical properties of potential waste materials to ensure their suitability for your application.

How to Use in IA

• Reference this study when discussing the use of waste materials as substitutes for conventional components in your design project.
• Use the findings on eggshell properties to justify the selection of similar waste materials for your own design explorations.

Examiner Tips

• Demonstrate an understanding of material properties and how they can be influenced by origin and processing.
• Clearly articulate the environmental benefits of using recycled or waste materials in your design solutions.

Independent Variable: ["Origin of eggshells","Calcination of eggshells"]

Dependent Variable: ["Specific gravity of eggshells","CaCO3 content of eggshells","Compressive strength of concrete"]

Controlled Variables: ["Cement type","Aggregate type","Water-cement ratio","Testing conditions (temperature, humidity)"]

Strengths

• Investigated a wide range of global eggshell sources.
• Utilized standard material characterization techniques (TGA, specific gravity test).
• Included practical application by testing in concrete mixes.

Critical Questions

• How would the results differ if eggshells were sourced from regions with different dietary habits or farming practices?
• What are the energy costs associated with calcining eggshells, and how does this affect the overall sustainability of the process?

Extended Essay Application

• Investigate the potential of other common food waste materials (e.g., oyster shells, bone meal) as sustainable replacements for conventional building materials.
• Conduct a life cycle assessment (LCA) comparing traditional concrete with concrete incorporating calcined eggshells to quantify the environmental benefits.

Source

Global Eggshell Properties: Characterizing Variability for Sustainable Partial Cement Replacement in Hong Kong’s Concrete · Preprints.org · 2023 · 10.20944/preprints202310.1834.v2