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

Contents Introduction Objective Experimental Procedure Results Conclusions

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

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

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.

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%

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

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

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

Methods Compaction of the road sites

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

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

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: 0.01-2 L·kg-1 (48 h) Field: ~ 0.1 L·kg-1 (4 months) Column: pH=11.8-12.4; k=20-40 mS·cm-1 Field: pH= 8-9 (3 roads); k=6 mS·cm-1

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

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

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

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

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

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

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

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

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

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

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.

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