This workshop is a deliverable of TRAC project which has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement Nº777823. Presentation 5: Recycling in construction material: case studies Quoc-Bao Bui, Ton Duc Thang University, Vietnam Dr. Quoc-Bao Bui received his PhD in 2008 at ENTPE (Ecole Nationale des Travaux Publics de l’Etat) Lyon, France. From 2008 to 2011, he continued at ENTPE as Postdoc researcher funded by Filiaterre company. From 2011 to 2016, he worked as Associate Professor at Polytech Annecy-Chambery, University Savoie Mont-Blanc, France. Since 2016, he has joined Ton Duc Thang University (Vietnam) as Associate Professor. His research interests cover non-conventional materials (soil-based materials, recycled materials) and structural analyses (RC structures, dynamic behaviour). He has recently been involved in research activities related to chemical activations, especially alkaline-activated materials. He has published about 60 articles in international journals.

1. International Workshop
Recycling in construction sector – From material characterisation to contribution
in the circular economy
Ho Chi Minh City, 30 December 2020
Recycling in construction material: case studies
Le Hoai-Bao, Bui Quoc-Bao*, Le Duc-Hien, Tran Minh-Tung, Phan To-Anh-Vu
Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam
* E-mail: buiquocbao@tdtu.edu.vn
1

2. SUMMARY
➢ INTRODUCTION
➢ CASES STUDIED
➢ Geopolymer recycled aggregate concrete
➢ Geopolymer adobes
➢ CONCLUSION
2

3. Viet Nam: Thermal Power Plants
(TPP): with charbon
=> wastes (bottom and fly ashes)
Source: VN Ministry of Constructions
▪ Every year: about 15 Mtons (75% fly ash
+ 25% bottom ash)
No enough stocked spaces in TPP
sites
Fly ash and Bottom ash
INTRODUCTION
3

4. Fly ash can be used for cement industry,
But: in numerous TPP: fly ash separation phase not included =>
no satisfying quality for cement production:
 Post-treatment: expensive!
bottom ash and fly ash purely become wastes
serious environmental problem
Source: http://www.baoxaydung.com.vn/
4

5. High cement amount in unburnt bricks (some cases ~ 25% by weight)
 increase the cost and carbon footprint.
Vietnamese government willingness:
replace clayed burnt bricks by more “green”
materials
unburnt BRICKS often proposed
Several difficulties: Economic, Tradition, Environment.
5

6. Recycling demanded
Types of inert wastes
(SOeS, France, 2017)
Total amount (106t)
Concrete 19.1
Bricks, tiles, ceramics 4.2
Glass 0.2
Bituminous mixes 11.2
Unpolluted stones and soils 114.8
Other materials from pavement demolition 37.5
Unpolluted road ballast 2.2
Unpolluted dredging materials 2.8
Other inert wastes 1.1
Mixtures of inert wastes 18.1
TOTAL INERT WASTES 211.2
In general: soil is not recycled for construction materials
=> A possibility to be explorated
6

7. ➢ Using fly and bottom ashes for construction materials
➢ Using recycled aggregates for concretes
➢ Using local soils for construction material production
➢ Reduce the cement amount
DIFFERENT STRATEGIES INVESTIGATED
7
In this presentation, cases studied:
➢ Geopolymer recycled aggregate concrete
➢ Geopolymer adobes (unburnt bricks)

8. Dr. Quoc-Bao Bui 30 December 2020
Recycled coarse aggregate (RCA)
Crushing Washing- Mortar content
- Absorption
- Specific gravity
- Aggregate Crushing Value (ACV)
8
Geopolymer recycled aggregate concrete (GRAC)
Recycled from a old concrete
Characterisation:
Case study 1

9. Dr. Quoc-Bao Bui 30 December 2020
Characterization of recycled coarse aggregate
Specific
gravity
Dry
density
Saturated
density
Water
absorption
ACV
(saturated)
Compressive
strength (MPa)
Natural
aggregate
2.66 2.59 2.61 1.1 15.0 70
RCA 2.60 2.26 2.39 5.8 25.8 34
 RCA: lower quality than natural aggregates due to:
- old mortars bonded on the original aggregate
- Degradation of microstructure during recycling procedure
9

10. Dr. Quoc-Bao Bui 30 December 2020
Compositions investigated
- Low-calcium Class F fly ash (FA)
- RCA: untreated and treated
- River sand (fineness modulus of 1.8)
- Alkali-activated binder (AAS): NaOH and Na2SiO3: different ratios AAS/FA
- LignoSulfonate- based Superplasticizer: without and with
- Curing temperature: ambient and 60oC
10
Geopolymer recycled aggregate concrete (GRAC)

11. Dr. Quoc-Bao Bui 30 December 2020
Geopolymer mortar/paste specimens
For the prediction model: geopolymer strength demanded
11
➢ Geopolymer paste (without sand)
➢ Geopolymer mortar (with sand)

12. Dr. Quoc-Bao Bui 30 December 2020
Results
Workability of GRAC
12

13. Dr. Quoc-Bao Bui 30 December 2020
Results
Compressive strength of GRAC
13
cured at 60°C cured at ambient
with superplasticizer

14. Dr. Quoc-Bao Bui 30 December 2020
Results
Compressive strength of GRAC
14
without superplasticizer
cured at 60°C cured at ambient

15. Dr. Quoc-Bao Bui 30 December 2020
Results (Microscopic analyses)
Development of gels in GRAC Large size FA particles already
reacted; smaller FA particles still
unreacted.
15

16. Dr. Quoc-Bao Bui 30 December 2020
Results (Microscopic analyses)
Correct bonding between
paste and aggregate
a zoom
Aggregate
Paste
16

17. Dr. Quoc-Bao Bui 30 December 2020
Results
Compressive strength of geopolymer mortar/paste
17

18. Dr. Quoc-Bao Bui 30 December 2020
Model of strength prediction for GRAC
Based on classical models for Portland cement concretes
❑ Feret’s model: 𝑓𝑐28 = 𝐾𝑔 𝑓𝑐𝑚28
1
1 +
𝜌𝑐
𝜌 𝑤
𝑊 + 𝜌 𝑤 𝑉𝑎
𝐶
2
❑ De Larrard’s model: 𝑓𝑐28 =
𝑝𝑓𝑐𝑚28
𝑞𝑓𝑐𝑚28 + 1
=> Identifying values of p and q for GRAC
Kg is the Feret’s constant, depending on aggregate quality
18
=> Propose a Modified model to take into account geopolymer => kb

19. Dr. Quoc-Bao Bui 30 December 2020
Results
Modified Feret’s model, at 28 days
Ambient curing
19
Curing with heating
=> Identify kb and Kg

20. Dr. Quoc-Bao Bui 30 December 2020
Results
20
Modified Feret’s model, at different times

21. Dr. Quoc-Bao Bui 30 December 2020
Results
ambient
21
De Larrard’s model, at 28 days :
heating
=> Identify p and q

22. Dr. Quoc-Bao Bui 30 December 2020
Results
22

23. Dr. Quoc-Bao Bui 30 December 2020
23
Adobes technique
(compression by hand)
Results satisfying for load-bearing bricks (for both cement brick and clay burnt
bricks)
=> Optimization to reduce the binder amount
Criteria following ASTM: absorption, compressive strength
Geopolymer: 6 - 20%
Dry density: 1.85 – 2.1
fcm = 6 - 35 MPa
Absorption: 5.2%
Curing 60, 90°C (24h): compressive strength increases 30%
In-situ soil of a construction site
Case study 2

24. Dr. Quoc-Bao Bui 30 December 2020
Conclusion
- The increase of ASS/FA ratio from 0.4 to 0.5 increased the slump and
decreased the compressive strength
- The addition of LignoSulfonate superplasticizer had no significant effect
on the slump and the compressive strength
- The concrete achieves higher strength compressive when cured at 60°C
instead of curing at ambient temperature
24
- correct bonding between the geopolymer gels created and aggregates.
- Modified Feret’s and De Larrard’s models can provide useful information
for the mix design, De Larrard’s model is simpler.
- Promising application of geopolymer adobes

25. Dr. Quoc-Bao Bui 30 December 2020
25
THANK YOU FOR YOUR ATTENTION
Acknowledgement: This project that has received funding from the European Union’s Horizon 2020
Research and Innovation Programme under grant agreement no. 777823