1. Recycling of APC fly ash in a pilot-scale road subbase
R. del Valle-Zermeño, J. Giro-Paloma, J. Formosa, J.M. Chimenos
June 10th, 2015

2. Contents Introduction Objective Experimental Procedure Results
Conclusions

3. Introduction Energy Waste reduction Landfill
Incineration of MSW
Bottom ash
Air pollution control ash (APC)
Energy
Waste reduction
Bottom ash (BA)
APC fly ash
Landfill

4. Weathered BA + APC + Portland cement = Granular material
Introduction
Weathered BA + APC + Portland cement = Granular material
Evaluation of mechanical and environmental behaviour at laboratory scale.
A great quantity of FINES
Real scenarios vs. Laboratory conditions
Temperature
Hydrology
Climatic factors
pH and redox conditions
Time scale
Mass transport rate
Carbonation and oxidation
Water infiltration and saturation
Edge effects

5. Objective
The aim of this study is to assess the mechanical and environmental performance of the granular material formulated with BA and APC fly ash in a field scale road site.

6. Granular material (GM):
Materials
MSW Incineration facility
Mortar: APC + cement
Granular material: BA + Mortar
Granular material (GM):
BA + APC + cement
Tarragona
SPAIN
APC fly ash +
CEM I 52.5R
20% Mortar
Weathered bottom ash
80%

7. Methods Pilot scale test 1 2 3 1 = 100% BOTTOM ASH
Natural ballast
Sub-base: Granular material
Drainage grave: Leachates collection system
Bottom liner
1 = 100% BOTTOM ASH
2, 3 = 100% GRANULAR MATERIAL

8. Methods Preparation of materials
Granular material: 80% Weathered Bottom ash + Mortar
Mortar: 50% APC + 50% Portland cement

9. Methods Leaching collection system Cumulative leachates
Leachates at laboratory and pilot scale:
pH, conductivity
Heavy metals
Chlorides
Sulphates
One-off leachates

10. Methods
Compaction of the road sites

11. Methods Test at pilot scale Irrigation schedule during 4 months
Simulation of drought periods
One-off and cumulative leachates
Mechanical and environmental assessment
Chemical and physical characterization
Compression and abrasion resistance tests
Column percolation tests

12. Results Characterization at laboratory scale Chemical composition:
WBA : Amorphous and vitreous phases (Si, Ca)
Mortar: Cl- and Ca
Granular material: Ranged between the materials
Mechanical characterization
Compressive strength: 14.5 ± 2.3 Mpa
Los Angeles coefficient (abrasion resistance): improvement of the manufacturing process

13. Results Analysis of the results The liquid-to-solid (L/S) ratio
pH and conductivity
Granular material
Concentration release vs. L/S at both scales
Chlorides
Sulphates
Heavy metals: Cu, Pb, Zn, As, Ni and Cr
Column: L·kg-1 (48 h)
Field: ~ 0.1 L·kg-1 (4 months)
Column: pH= ; k=20-40 mS·cm-1
Field: pH= 8-9 (3 roads); k=6 mS·cm-1

14. Results Release of chlorides One-off leachates Wash-out peak ● Field
○ Column

15. Results
One-off leachates
Release of sulphates
● Field
○ Column

16. Results Differential concentration release (DOGC. 2181, 1996) As Zn Ni
One-off leachates
Differential concentration release (DOGC. 2181, 1996) As Zn Ni Pb Cr
Cumulative leachig results: The content of metals should not be attributed to exclusively APC
Exhaustive analysis: Comparison of scales
- Road sites 2 and 3 (granular material): average results
Concentration release increasing over time until stabilizing around a L/S ratio of 0.05 L·kg-1
Pozzolanic effect of cement
Cumulative leachates
Sum of one-off leachates

17. Results
Cumulative release (mg·kg-1) vs L/S at both scales Cu

18. Results
Cumulative release (mg·kg-1) vs L/S at both scales Pb

19. Results
Cumulative release (mg·kg-1) vs L/S at both scales Zn

20. Results
Cumulative release (mg·kg-1) vs L/S at both scales As

21. Results
Cumulative release (mg·kg-1) vs L/S at both scales Ni

22. Results
Cumulative release (mg·kg-1) vs L/S at both scales Cr

23. Results Cu Pb Zn As Ni Cr Differences:
Potential mechanisms of water infiltration
Mass transport rate
Diffusion mechanisms through the layers
Preferential flows
Water runoff, edge effects and lateral inputs
Future immobilization

24. Conclusions
Granular material: WBA and a mortar formulated with APC and Portland cement.
Environmental assessment.
Mechanical properties required to put it in service.
The potential leaching of heavy metals, metalloids, chlorides and sulphates was assessed by monitoring them during 4 months with artificial irrigation.
Pozzolanic effect of the cement mortar.
Differences at both scale.

25. R. del Valle-Zermeño rdelvallez@ub.edu
Thank you very much
R. del Valle-Zermeño