1. Durability of recycled concrete
drs. ing. Joseph Miquel
prof.dr.ir. Lucie Vandewalle
ing. Luc Boeme
prof. dr. ir. Tom Van Gerven
ir. Caroline Ladang

2. Recycon RecyCon Mission: Sustainable building
- Recycling of Construction and Demolition Waste in Construction
Mission: Sustainable building
- Durable materials
- Energy efficiency
- Reuse of materials after “End of life”
Approach: Industrial Engineering
- focus: economic value, solutions for existing problems and industrial opportunities
- less: fundamental research
Technologiecluster Bouw
Technologiecampus Oostende
Zeedijk 101
8400 Oostende
tel

3. Introduction
Demolition
Crushing plant
Recycled aggregates
Concrete plant
Concrete
In 2012, more than 11 Mt of rubble were processed as recycled aggregates.
Currently, most recycled aggregates are used in low-grade applications such as road foundations and lean concretes.
However, research has shown that recycled debris can replace coarse natural aggregates in several concrete high-end applications
"ValReCon20: Valorisation of
recycled concrete aggregates
in concrete C20/25 and C25/30",
Oostende: Boehme Luc, 2012.
ISBN

4. Current state of the art in Flanders

5. High-end applications
Foundation
Sub foundation …
Road construction
Structural concrete ….
Precast concrete
Architectural concrete
SCC
HPC
Materials for cement ?

6. Abstract Phd
The goal of this investigation is to determine the durability of recycled concrete, more in particular the resistance to acid, chloride penetration and frost/thaw attack. These durability issues present in many cases a determining factor for the use recycled concrete in industrial and civil building applications. The main reason why this concrete reacts differently compared to standard concrete is the presence of a more open pore structure due to the presence of old attached mortar on the surface of recycled aggregates. The study includes modelling of the water absorption, modelling the durability, relating this to the density of RCA and of recycled concrete, W/C- ratio and water content.

7. General introduction and outline Research strategy
Recycled Concrete Aggregates
Amount attached mortar
Water Absorption
Density
Influence aggregate size
Water Management
Concrete
Water absorption submersion
Water absorption capillarity
Resistance Aggressive Environment
Frost/thaw
Chlorides
Acids

8. Recycled Concrete Aggregates

9. Composition of concrete
Fresh Concrete
Hardened Concrete
mass v%
[kg/m³]
[%]
air 6 12
+6%
cement
300 10
cement stone 19
water
hydration 90 9
=>
workability 60
sand
750 30
gravel
975 39
±30% of the amount of cement is used to form cement stone
Additional water evaporates and is replaced by air
Air + cement stone + sand = mortar (±60%)

10. Influence aggregate size
Coarse aggregates
Coarse recycled aggregates
Dmin ≥ 4mm
Dmax <20mm
Wabs <10%
Fine recycled aggregates
Dmin 0mm
Dmax ≤4mm
Wabs >10%
Increased risk of contaminations
All-in aggregates
Fine aggregates

11. Problems with attached mortar
One important difference between CRCA and natural aggregates is water absorption. The high water absorption of CRCA is linked to the presence of old mortar (de Juan and Gutierrez, 2009). Dry recycled aggregates behave like sponges in fresh concrete, thus impacting on the water/cement ratio (w/c) ratio. This ratio represents the water mass to cement mass ratio in a concrete mix, and is used as an indicator of durability and strength development.
Boehme, L., Joseph, M., Anseele, T., Verstraete, S., "Assessment of water reducing admixture in concrete with recycled aggregates", in Central Europe towards Sustainable Building 2013 ( June 2013, Prague), 2013, art. nr. CESB13_1128, pp
Joseph, M., Sierens, Z., Boehme, L., Vandewalle, L., "Water absorption variability of recycled concrete aggregates", Magazine of Concrete Research, vol. 67, no. 11, 2015, pp

12. Influence of the old mortar
The amount of mortar has an exponential influence on the water absorption and particle density of recycled concrete aggregates. (1)
A. Akbarnezhad, K. Ong, M. Zhang, C. Tam en T. Foo, „Microwave-assisted benefication of recycled concrete aggregates,” Construction and Building Materials, vol. 25, pp , 2011.

13. Smart Crusher
WA24 5,2 -> 2,4

14. Simulation Industrial processes in laboratory

15. Lab scale simulation of industrial mortar removal processes

16. Water absorption model for coarse recycled concrete aggregates
Abstract accepted by the CESB16 Scientific Committee

17. Relationship water absorption density – literature & experiments

18. Water absorption model for coarse recycled concrete aggregates
WA(t) = MR5min + (MR1sec - MR5min) * e-kt – Wf
k = f(d;Fl;ρrd)
MR1sec = f(d;Fl;ρrd)
MR5min = f(d;Fl;ρrd)
Wf = f(d)

19. Water Management Concrete

20. Water Absorption model for (recycled) concrete

21. Water Absorption model for (recycled) concrete

22. Evaporation with changing Temperature

23. Resistance Aggressive Environment

24. Resistance to chloride penetration

25. Resistance to (weak) acids
Joseph, M., Boehme, L., Cornelly, C., Anseeuw, I., Declercq, W., Vandewalle, L., "Recycled concrete in weak acidic environments", in Advances in Science and Technology, 2016.

26. Resistance to frost/thaw attack

27. Resistance to frost/thaw attack

28. Thanks for your attention
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