Recycled aggregate concrete, stress strain behaviour

1. Stress-Strain Behavior of Concrete made with
Treated Recycled Coarse Aggregate
Srinivasa Reddy Vempada
Department of Civil Engineering,

2. Recycled aggregate
• Advantages
• Disadvantages
• Surface treatments – chemical and physical
• Mineral Admixtures – Industrial waste by-products
• Two stage mixing method
• 100% replacement treated recycled aggregate concrete
• M20, M30, and M40 grade treated recycled aggregate
• 0%, 5%, and 10% silica fume (SF)

3. TREATMENT OF RECYCLED COARSE
AGGREGATE
• Pre-soaking in HCl acid
• rinsed with water
The recycled coarse aggregates from the jaw crusher are left to air dry
for 15 days and soaked in HCl acid.

4. • M20, M30, and M40 grades of blended concrete with silica fume (SF)
at 0%, 5%, and 10%
• the use of chemical admixture was necessary to make up for the
additional water (3 to 6%)
• Chemical admixture - by weight of binder/powder (cement and
mineral admixtures) is 0.20%, 0.30%, and 0.40%.

5. • the compressive strength of concrete made with 100% treated recycled coarse
aggregate decreases by approximately 28–30%
• The fact that some mortar has been adhered to the surface of the recycled
aggregate, increasing the aggregate's capacity to absorb water, is the reason for the
reduction in compressive strength

6. • To strengthen the Interfacial Transition Zone (ITZ) in concrete composed
entirely of recycled aggregate, silica fume, a mineral additive, is added in
place of 5% cement in TRAC concrete
• SF admixed RAC has a higher compressive strength than concrete made
with NA when 5% of the cement is substituted
• The ITZ zone has improved as a result of the pozzolanic activity of silica
fume and the recycled coarse aggregate portion of 20 mm (60%) and 10
mm (40%).
• SF as filler and pozzolan

7. STRESS-STRAIN CURVE

10. CONCLUSIONS
The following conclusions are made considering the research work's major findings and results:
1. Workability was shown to decrease for all grades of concrete mixes made with 100% recycled aggregate because
of water loss from recycled aggregate absorption. The workability of 100% treated recycled coarse aggregate
concrete is improved by superplasticizer.
2. When compared to natural aggregate concrete mixes, the 5% SF blended treated recycled aggregate concrete
mixes had better stress values for the same strain levels, according to the data gathered from stress-strain curves.
3. The modulus of elasticity of concrete mixes including 100% treated recycled coarse aggregate is 5% less than that
of concrete mixes containing natural aggregates. However, adding 5% SF increases the treated recycled aggregate
concrete's modulus of elasticity by 14%.

11. Selected References
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12. Thank you