Combining the strengths of UMIST and The Victoria University of Manchester
Innovative use of recycled aggregate concrete in reinforced
concrete beams Yong Wang
Professor of Structural and Fire Engineering School of Mechanical, Aerospace and Civil Engineering,
University of Manchester, UK
Combining the strengths of UMIST and The Victoria University of Manchester
Construction waste/scrap tyres • ~200 million tons of construction and demolition waste annually
in EU
- 28% recycled, 72% landfill
• 280 million scrap tyres annually in EU
- 60% recycled
• Main use of recycled waste: low grade filler
• Obstacle preventing use of rubber recycled aggregates (RRA) in wholesome primary loading members: reduction of mechanical properties (~30% ) and durability.
• Can innovative ways be found to use RRA in primary loadbearing members without sacrificing performance?
Combining the strengths of UMIST and The Victoria University of Manchester
Bending of reinforced concrete beam
Mechanical properties of concrete on tension side not considered in calculating design resistance.
Combining the strengths of UMIST and The Victoria University of Manchester
Using RA in bending members without sacrificing performance:
a simple idea
Tension zone
Compression zone
Combining the strengths of UMIST and The Victoria University of Manchester
Experiments
Control beam: all fresh concrete
Two layer beam:
Top 50mm: fresh concrete
Bottom 100mm, RA concrete
Combining the strengths of UMIST and The Victoria University of Manchester
Material properties
Mix type slump(mm)28 days cylinder
strength(MPa)
Density (kg/m3)
Tensile strength (MPa)
Modulus (GPa)
CC 165 40.1 2390 4.11 45 RRAC10SP 170 30.37 2190 2.82 14.5
Combining the strengths of UMIST and The Victoria University of Manchester
Experiments
Control beam: all fresh concrete
Two layer beam:
Top 50mm: fresh concrete
Bottom 100mm, RA concrete
Combining the strengths of UMIST and The Victoria University of Manchester
Comparison of structural behaviour • RA concrete beam
strength slightly lower than fresh concrete beam
• But, RA concrete beam strength above design strength
• Little difference in deflection at service load
0
20000
40000
60000
80000
100000
120000
140000
160000
0 2 4 6 8 10 12 14 16
Load
(N)
Displacement(mm)
Exp-control beam
Exp composite beam
Combining the strengths of UMIST and The Victoria University of Manchester
Conclusion, potential applications and challenges
• Low grade RRA can be used in tension area of reinforced concrete bending members without sacrificing structural performance
• In buildings – benign environmental exposure, durability not critical
• In beams and slabs – use 90%+ concrete
• Precast members – time to allow RA concrete to solidify before casting fresh (stronger concrete) on top
• Possible reduction in cement use in RA concrete because mechanical properties not critical
• Challenges in practical applications?
