Assessing Engineering Properties of Concrete Produced with Broken Earthenware as a Partial Replacement of Coarse Aggregate

Technical Summary: Assessing Engineering Properties of Concrete with Broken Earthenware as Partial Coarse Aggregate Replacement

Problem Statement
The construction industry faces significant challenges regarding the rapid depletion of natural resources and the rising costs associated with aggregate extraction. Concrete, the second most consumed material globally after water, relies heavily on aggregates, which constitute 75–80% of its volume. In developing nations like Ghana, excessive quarrying leads to environmental degradation and ecosystem pollution. Concurrently, the ceramic and earthenware industries generate substantial waste; approximately 30% of raw materials in ceramic production and 2% of finished products are discarded as scrap. This waste often ends up in landfills, where it can interact negatively with groundwater. The study addresses the dual need to reduce construction costs and mitigate environmental impact by investigating the viability of using broken earthenware bowls as a partial replacement for traditional coarse aggregates (crushed granite) in concrete production.

Methodology
The research employed an experimental approach to evaluate the mechanical, physical, and durability properties of concrete.

• Materials: The study utilized Ordinary Portland Cement (GHACEM Super Strong 42.5R), pit sand, crushed granite, and broken earthenware bowls. Water met BS EN 1008:2002 standards.
• Mix Design: A target strength of 25 N/mm² was set using a 1:2:4 mix ratio with a water-to-cement ratio of 0.55.
• Specimen Preparation: Concrete specimens were cast in steel cubes (100mm³) and cylinders (100mm diameter × 200mm height). The crushed granite was partially replaced with broken earthenware aggregates at 0% (control), 10%, 20%, 30%, and 40% by weight.
• Curing and Testing: Specimens were cured for 7, 14, 21, and 28 days. Testing included:
  • Density: Measured per BS EN 12390-7:2019.
  • Compressive Strength: Tested using a Universal Testing Machine (UTM) per BS EN 12390-3:2019.
  • Split Tensile Strength: Conducted per BS EN 12390-6:2009.
  • Water Absorption: Determined after 28 days per BS EN 1881-122:2011.
  • Magnesium Sulphate (MgSO₄) Attack: Specimens were cured in MgSO₄ solution for 28 days and subsequently tested for compressive strength per BS EN 206-1:2000.
• Data Analysis: Results were analyzed using Microsoft Excel and One-Way ANOVA to determine statistical significance (P < 0.05).

Key Results

• Density: Density decreased as the percentage of earthenware replacement increased. The control specimen (0%) achieved the highest density (2486.67 kg/m³ at 28 days), while the 40% replacement recorded the lowest (2276.67 kg/m³). The 10% replacement yielded a density of 2432.00 kg/m³, which is 2.2% lower than the control but remains within the normal weight concrete range (1842–2483 kg/m³ per ASTM C138).
• Compressive Strength: Strength increased with curing age but decreased with higher replacement percentages. At 28 days, the control recorded 27.13 N/mm². The 10% replacement recorded 26.39 N/mm² (2.7% lower than control), while the 40% replacement recorded 24.76 N/mm². Despite the reduction, all specimens except the 40% replacement met the target strength of 25 N/mm², and all fell within the acceptable standard for load-bearing masonry units (minimum 13.8 MPa per ASTM C90-22).
• Split Tensile Strength: Trends mirrored compressive strength, decreasing as replacement percentages rose. At 28 days, values ranged from 2.769 N/mm² (control) to 2.487 N/mm² (40% replacement). The split tensile strength remained between 8% and 15% of the compressive strength, consistent with standard concrete behavior.
• Water Absorption: Water absorption increased with higher replacement percentages. The control showed 2.44% absorption, while the 10% replacement showed 2.52% (3.2% higher than control). The 40% replacement reached 3.19%. All values remained below the 5% threshold often cited for high-quality concrete and within the 4–6% optimal range.
• Magnesium Sulphate Attack: Exposure to MgSO₄ caused strength losses across all specimens. Interestingly, the 40% replacement demonstrated the highest resistance, with only a 0.3% strength loss, compared to 2.5% for the control. The 10% replacement showed a 1.6% loss.

Conclusions and Significance
The study concludes that broken earthenware aggregates are a viable partial replacement for coarse aggregates in concrete.

• Standards Compliance: Concrete produced with up to 40% replacement meets the engineering standards set by BS EN 12390:2019 and BS 1881-122:2011 regarding density, strength, and water absorption.
• Recommended Applications: The authors recommend a 10% replacement for standard concrete works, as it offers a balance of strength and durability with minimal deviation from control properties. A 40% replacement is recommended specifically for environments with high magnesium sulphate exposure, as the 40% mix demonstrated superior resistance to chemical attack.
• Economic and Environmental Impact: Utilizing broken earthenware reduces construction costs by substituting expensive natural aggregates with low-cost industrial waste. Furthermore, it promotes environmental sustainability by diverting ceramic waste from landfills and reducing the ecological footprint associated with aggregate extraction.

The research affirms that reusing ceramic waste enhances both cost efficiency and environmental sustainability in the construction industry without compromising the structural integrity required for load-bearing applications.