Main Objective
Investigate the influence of crushed clay roof tiles on concrete performance.
COMPLETED RESEARCH
INVESTIGATING THE INFLUENCE OF CRUSHED CLAY ROOF TILES AS PARTIAL REPLACEMENT OF NATURAL COARSE AGGREGATES ON THE PERFORMANCE OF CONCRETE
Examining crushed clay roof tiles as a partial replacement for natural coarse aggregate to create reduced-density concrete from construction waste.
Kampala, Uganda Construction Materials 2026
Project Overview
This M15 concrete study evaluated crushed clay roof tiles (CCRT) as a replacement for natural coarse aggregate at 0%, 10%, 25% and 35%. It measured slump, compressive strength, density, moisture content, water absorption, specific gravity and aggregate shape. The research turns roof-tile waste into a potential reduced-density construction material.
RESEARCH PROBLEM
Roof-tile waste has value beyond landfill.
Natural aggregate extraction is resource-intensive, while broken clay roof tiles from construction and demolition are frequently discarded. The research tests how much natural coarse aggregate can be replaced without losing the concrete performance needed for practical applications.
OBJECTIVES
Research Objectives
Workability
Assess how CCRT replacement changes the slump of fresh concrete.
Strength & Density
Determine compressive strength and reduced-density potential at each level.
Cost & Suitability
Evaluate whether recycled tiles provide a viable material alternative.
MATERIALS
Materials Used
Portland Cement
The binding material for the M15 concrete mix.
Crushed Roof Tiles
Recycled clay roof-tile particles used in place of natural coarse aggregate.
Natural Aggregates
Fine aggregate and natural coarse aggregate for the control mix.
Clean Water
Mixing water, with pre-soaking recommended for porous CCRT.
METHODOLOGY
Research Methodology
Concrete mixes were cast and assessed under standard laboratory conditions from 7 to 28 days.
Tile Processing
Roof-tile waste was crushed, sieved and characterised for concrete use.
Mix Design
Four mixes replaced 0–35% of natural coarse aggregate by CCRT.
Cube Casting
Concrete cubes were prepared using a 1:2:4 mix and 0.45 water-cement ratio.
Curing
Specimens were cured and measured at 7, 14 and 28 days.
Performance Tests
Slump, strength, density, moisture and absorption were tested.
Comparison
Results were used to find the balance between reduced weight and performance.
KEY FINDINGS
Research Results
CCRT reduced density, but its high porosity reduced workability and strength at higher replacement levels.
10–25%
Optimum CCRT replacement range
24.53 MPa
28-day control strength
19.28 MPa
28-day strength at 35% CCRT
130 → 27 mm
Slump decrease from control to 35% replacement
2.15
Bulk specific gravity of CCRT
16.30%
Water absorption of porous CCRT
CONCLUSIONS
Major Findings
Construction-Waste Recovery
Crushed roof tiles can divert demolition waste from disposal and conserve aggregates.
Moderate Replacement Works
10–25% offered the best compromise between adequate strength and lower density.
Porosity Must Be Managed
Pre-soaking CCRT is essential to control water demand and workability.
RECOMMENDATIONS
Next Steps
Use 10–25% CCRT for lightly loaded and non-structural construction.
Pre-soak roof-tile aggregate before batching.
Avoid use in heavily reinforced structural elements without mix optimisation.
Study long-term durability and supplementary cementitious materials.