Main Objective
Evaluate waste clay bricks as a sustainable alternative to natural fine aggregate in concrete.
UNDERGRADUATE STUDENT
INVESTIGATION ON USING WASTE CLAY BRICKS AS A SUSTAINABLE ALTERNATIVE TO FINE AGGREGATE IN CONCRETE
Investigating crushed waste clay bricks as a sustainable replacement for natural sand in concrete, reducing both construction waste and pressure on river-sand resources.
Juba, South Sudan Construction Materials 2026
Project Overview
This study assessed crushed waste clay bricks as a partial replacement for natural fine aggregate in 1:2:4 concrete. Five replacement levels - 0%, 25%, 50%, 75% and 100% by weight of sand - were evaluated through slump, compressive-strength and water-absorption testing. The work addresses waste-clay-brick dumping and sand-mining pressure in Kampala.
RESEARCH PROBLEM
Construction waste and sand depletion are linked challenges.
Rapid urbanisation generates substantial demolition waste while demand for natural sand increases pressure on local resources. Clay brick waste is often dumped rather than recovered. This project investigates whether crushing it into fine aggregate can produce concrete suitable for practical construction.
OBJECTIVES
Research Objectives
Workability
Measure how brick replacement changes concrete slump and water demand.
Strength
Determine compressive strength at 7, 14 and 28 days for every replacement level.
Water Absorption
Assess the durability implications of more porous brick particles.
MATERIALS
Materials Used
Portland Cement
The primary binder for the 1:2:4 nominal concrete mix.
Crushed Clay Bricks
Waste bricks processed to pass a 4.75 mm sieve and used in place of sand.
Natural Aggregates
Natural sand and coarse aggregate used in the control and comparative mixes.
Clean Water
Mixing water adjusted to manage the high absorption of brick particles.
METHODOLOGY
Research Methodology
Concrete cubes were prepared under controlled laboratory conditions and tested at multiple curing ages.
Brick Processing
Waste bricks were cleaned, crushed and sieved for aggregate grading.
Mix Design
Five mixes contained 0% to 100% replacement of natural sand.
Cube Casting
150 mm concrete cubes were cast using the 1:2:4 mix ratio.
Curing
Specimens were cured for 7, 14 and 28 days.
Testing
Slump, specific gravity, water absorption, density and strength were tested.
Comparison
Results were evaluated against C20 concrete performance requirements.
LABORATORY TESTS
Experimental Tests
Slump Test
Specific Gravity
Compressive Strength
Water Absorption
Density
KEY FINDINGS
Research Results
Moderate waste-clay-brick replacement maintained the strength required for C20 concrete, while higher proportions increased absorption and reduced strength.
25–50%
Recommended natural-sand replacement range
22.25 MPa
28-day strength at 50% brick replacement
21.39 MPa
28-day strength at 25% brick replacement
20 MPa
C20 target strength exceeded at 25% and 50%
2.49
Average specific gravity of crushed brick aggregate
5.39 → 11.71%
Water absorption increased from control to 100% replacement
CONCLUSIONS
Major Findings
Resource Recovery
Waste clay bricks can reduce construction-and-demolition waste and demand for river sand.
Best Balance at 25–50%
Moderate replacement produced satisfactory performance for C20 concrete applications.
High Replacement Has Limits
Levels above 50% increased absorption and fell below C20 strength requirements.
RECOMMENDATIONS
Next Steps
Use 25–50% brick replacement for C20 low-rise and pavement applications.
Pre-saturate brick aggregate and adjust water to maintain workability.
Use high-replacement concrete only in lightweight or drainage applications.
Study long-term durability and water-reducing admixtures further.