# Technical and environmental assessment of MSWI Bottom-Ash as secondary raw material in Road Construction

Maria Lorena Gonzalez, Denise Blanc, Christine de Brauer

<figure><img src="image_1.png" /></figure>

## To cite this version:

Maria Lorena Gonzalez, Denise Blanc, Christine de Brauer. Technical and environmental assessment of MSWI Bottom-Ash as secondary raw material in Road Construction. CIGOS 2013 - Construction et Développement durable, INSA LYON, Apr 2013, LYON, France. hal-04002612

HAL Id: hal-04002612

https://hal.science/hal-04002612

Submitted on 23 Feb 2023

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Technical and environmental assessment of MSWI Bottom-Ash as secondary raw material in Road Construction

Lorena Gonzàlez<fnref n="1" />*, Denise Blanc<fnref n="1" />, Jérémie Vercasson<fnref n="1" />, Christine de Brauer<fnref n="1" />

1. INSA LYON, Laboratory of Civil & Environmental Engineering, LGCIE, Bâtiment Sadi Carnot, 9, rue de la Physique, 69621 Villeurbanne Cedex, France.

* Corresponding author: maria-lorena.gonzalez-ramirez@insa-lyon.fr, Phone number: 33 4 72 43 60 84

**Keywords:** Municipal solid waste incineration (MSWI), Bottom ash, characterization, trace pollutants, secondary road materials

## Abstract

Bottom-Ash from municipal solid waste incineration (MSWI BA) has physical and mechanical properties making it suitable as a secondary raw material for road construction. The main goal of this study was the geotechnical and environmental characterization of MSWI BA from a French MSWI plant towards its eventual utilization as self-compacting in pavement sub-layer or coated road shoulders structures. According to French GTR guidelines<fnref n="1" />, bottom ash complied with the technical main criteria requirements for the suitable utilization. Data obtained from leaching and column tests fulfill the French environmental threshold limits for unbounded road base utilization (Type 1)<fnref n="2" />. For road base utilization (Type 2), only Mo and Cl⁻ concentrations exceed the limit values. Addition of cement as a hydraulic binder to the formulated material seems to stabilize these pollutants. The leaching test on monolith (EN 15863) showed concentrations below the threshold limits, according to Netherlands regulations<fnref n="3" />. The obtained formulation which complies with the main criteria for self-compacting material was validated. The compressive strength experiments performed after 28 days of curing were lower than 2MPa. The technical and environmental assessments showed satisfactory results. Therefore, Bottom Ash may be successfully used as substitute aggregate in self-compacting materials.

## 1- INTRODUCTION

Bottom ash is the most significant by-product from municipal solid waste incineration (MSWI). It accounts for 25 - 30% of the solid product resulting from MSW combustion. The annual production of bottom ash in France is estimated between 2.7 and 3.2 million tons (30% by weight of waste incinerated and 10% by volume) [1,2]. Nowadays, the MSWI Bottom ash in France is mainly landfilled or reused as a substitute for natural aggregates in building material for road constructions. However, compared to materials of natural origin, bottom ash has elevated concentrations of both trace metals and salts. Road leachate acts as a transport medium for these pollutants since they are water-soluble and environmental factors influence the extent of metal transported to the surroundings [3]. In France MSWI bottom ash can be recycled when limit values for the total

<footnote n="1">¹ SETRA-LCPC. (2007). Guide technique routier pour la conception et la réalisation de terrassements</footnote>

<footnote n="2">² SETRA- LCPC (2011)</footnote>

<footnote n="3">³ The Netherlands “Soil Quality Decree” of November 22, 2007.</footnote>
element concentration and leaching do not exceed the actual threshold limits depending on the specific recycling option [4]. Leaching of metals from bottom ash and the reduction of its importance has been subject of several investigations. Treatment methods are the way to reduce leaching risk, however they are often expensive. Another way is to stabilize the material chemically and/or mechanically by mixing the bottom ash with a hydraulic binder as cement, creating a dense material, as so called bound material. This type of material is commonly used for road bases and pavement applications [3, 5-8].

This work aims to study an alternative utilization for MSWI bottom ash in self-compacting material for pavement sub-layer or coated road shoulders structures. The study involved three stages. The first one consisted in an environmental assessment based on leaching standard tests to yield information about the degree of dissolution of MSWI bottom ash and its potential environmental impact for the desired use. In the second stage, a technical assessment is performed. Several geotechnical properties of Bottom Ash are measured. Then, a suitable formulation which complies with main criteria for self-compacting material is validated. In the last stage, an environmental assessment is carried out for the formulated material. The environmental impact in a specific scenario is evaluated through a leaching test on monolith (EN 15863).

# 2- MATERIALS AND METHODS

## 2.1. Material

### 2.1.1. Bottom ash

Bottom ashes from MSWI French plant were sampled. One 4-months old sample of 300Kg, 40 mm sieved, ferrous and non-ferrous metals free was collected from a heap. To obtain representative samples, the size of the sample was reduced to 100-150 kg by quartering. Subsequent quartering was carried out to supply samples (10-30kg) for the different characterization tests.

### 2.1.2. Self-compacting material

Bottom ash was used to prepare the self-compacting material. A number of monoliths were prepared and cured in Zippler® cylindrical molds (11cm×22cm). The cement used was a CEM II/ALL 32.5. Test samples were prepared according to the mixing composition indicated in Table 1. An important quantity of water was needed to obtain a correct consistency of material (cf. 3.2.).

<table><caption>**Table 1** Recipe of self-compacting material.</caption><tr><td>Water (kg/m³)</td><td>516</td></tr><tr><td>Cement (kg/m³)</td><td>100</td></tr><tr><td>Bottom Ash (kg/m³)</td><td>1800</td></tr></table>

## 2.2. Methods

### 2.2.1 Environmental assessment

The environmental performance of bottom ash was assessed by means of EN 12457-2 leaching test and EN 14405 column test. These EN tests are applied on < 4mm sieved fraction with deionized water as leachant. The concentrations of major and trace elements in the eluates of leaching and column tests were measured by inductively coupled plasma mass spectrometry (ICP-AES) and Ionic Chromatography for anions species.

**Leaching test:** EN 12457-2 is a single batch leaching test performed at L/S =10 L/kg, agitated for 24h. The eluate was filtered over a 0.45 µm membrane filter. The conductivity and the pH of the eluate were measured immediately. The test was performed in triplicate.
**Column test:** For the EN 14405 test a column (30 cm length, 10 cm internal diameter) is filled with bottom ash previously sieved. The column is percolated with deionized water from bottom to top with a maximum water flow of 15 cm/d. The eluate was collected in several fractions depending on the total liquid to solid ratio (L/S) reached. Seven fractions are collected corresponding with L/S of 0.1, 0.2, 0.5, 1, 3, 5 and 10. The test took about three weeks. Then eluates were filtered over a 0.45 µm membrane filter. The conductivity and the pH of the eluates were measured immediately. The metal and anions concentrations in the consecutive fractions were summed to obtain cumulative leachate concentrations.

**Leaching test in batch:** The dynamic monolithic leaching test with periodic leachant renewal was performed following prEN 15863. The test portion of monolithic waste was placed in a reactor and completely submerged in water. The water is introduced in the reactor up to a given volume of liquid to surface area ratio (L/A ratio = 8), the top of the test portion is at least 2 cm submerged and that the distance between the test portion and the wall of the reactor is at least 2 cm. The water was renewed at predetermined time intervals: 0.08, 1, 2, 8, 14, 15, 28 and 36 days. Each eluate was filtered over a 0.45 µm membrane filter. The conductivity and the pH were measured immediately. The concentrations of major and trace elements in the filtrate were measured by inductively coupled plasma mass spectrometry (ICP-AES) and Ionic Chromatography for anions species.

### 2.2.2 Technical assessment

To obtain a geotechnical characterization of bottom ash, physical and mechanical methods were used.

**Particle size distribution:** Particle size analysis of bottom ash was performed according to NF standards (NF P 94-056). This test is carried out by sieving on a series of successive sieves: 0.08, 0.25, 1, 2, 4, 8, 10 and 40 mm.

**Proctor compaction test:** This test aims to determine the relationship between bottom ash bulk density and water content under specified compaction energy. The test was performed according to NF standards (Standard proctor, NF P 94-093).

**Bearing capacity:** The CBR index (California Bearing Ratio) provides a measurement of the impact resistance of compacted aggregate. It is determined as the ratio between the impact loads causing a given penetration in the samples relative to a fixed pattern. This test was performed according to NF standards (CBR immediate index, NF P 94-078).

**SBV:** Determination of the methylene blue of a soil by means of the stain test (SBV) is an identification parameter that measures the overall quantity of the clayey fraction. According to standard NF P94-068, SBV is in fact correlated with the specific surface area of soil or aggregate particles, which depends mainly on the clayey fraction.

**Mechanical test:** The compressive strength is the most common performance measure used to control the loads which may be applied to a concrete structure. The compressive strength is calculated from the failure load divided by the cross-sectional area resisting the load and reported in megapascals units (MPa). Compression strengths were measured following NF EN 196-1 after 28 days of curing. Six cylinders from the same formulation batch were used to determine the compression strengths.

## 3- RESULTS AND DISCUSSION

### 3.1. Environmental characterization of bottom ash
**Leaching test (EN 12457-2):** As shown in Figure 1, few elements were below the detection limit, As, Cd, Hg and Se. Leaching concentrations of Cu, Cr, Mo and Sb exceeded the SETRA-LPC guidelines limit values for “All utilizations” [4]. The pH-value of the leachate was 11.98 and the solution concentrations of these elements were Cu (13.64 mg/kgDM), Mo (2.99 mg/KgDM), Cr (0.55 mg/kg DM), Sb (0.21 mg/KgDM) and Cl- (3327.7 mg/KgDM). Thus, due to the high pH-value, Cu and Mo were highly enriched in bottom ash leachate. It is already well known that the Cu present in bottom ash leachates is largely bound to dissolved organic matter (DOM) [9-11]. DOM dissolution at pH >11, could enhance the leaching and mobility of highly copper soluble complexes. Likewise, at this pH-value anionic form of Mo (MoO₄²⁻) has low sorption affinity to Fe/Al(hydr) oxides minerals follow-on a higher concentration of Mo in the leachate. [9, 12].

Unlike Copper and Molybdenum, total chromium and antimony were less released. The leachability of these elements often depends on their elemental state as well as many hydroxides and oxides formed by reduces species at high pH are only slightly soluble [12-14]. Moreover, solid solution formation with ettringite (Ca₆A₁₂(SO₄)₃(OH)₁₂ 26H₂O) is suspected to cause a larger reduction in oxyanions (CrO₄²⁻, Sb(OH)₆⁻) mobility due to partial or full replacement of SO₄. [13,15]

<figure><img src="image_3.png" /><figcaption>**Figure 1.** Concentrations of trace elements and salts (mg/kg DM) in bottom ash leachate compared to valorization threshold limits</figcaption></figure>

The major elements concentrations in leachate were also measured (data not shown). Only Cl⁻ concentration exceed the SETRA-LPC guidelines limit value for “All utilizations”. The solution concentration of Cl⁻ was 3327.7 mg/kgDM against “All utilizations” limit of 800 mg/kg DM. The dissolution of Cl⁻ is pH independent and is assumed to be released according to its availability, diffusion control and surface controlled reactions. [19]

Since these results did not comply with the first stage for assessing the environmental acceptability of alternative materials², it was necessary to go through the second stage. A leaching column test was performed in order to approve or deny the bottom ash utilization in road construction.

**Column test (EN 14405):** The results obtained from column test are summarized in Table 2. The leachate pH-value for the first eluate was 12.4 and progressively decreased over time. This strongly alkaline pH can be primarily due to the presence of portlandite Ca(OH)₂ [16,17]. The decrease in pH-value is mainly due to the gradual dissolution of Ca(OH)₂ and to ettringite formation [18]. At the end of the test, pH-value remains close to 11.32.

Molybdenum and Chloride leaching exceed SETRA-LPC guidelines limit value for “Type 2” valorization (Figure 2). The chloride ion is highly soluble, and its transfer is simply controlled by water infiltration. As such it dissolved rapidly an increase in chloride concentration was observed.
<table><caption>**Table 2.** Trace elements and salts cumulative concentrations in bottom ash leachates from column tests – compared to SETRA-LPC valorization threshold limits</caption><thead><tr><th>Paramètres</th><th>LoD (mg/L)</th><th>E1 L/S = 0.1 mg/kg DM</th><th>E2 L/S = 0.2 mg/kg DM</th><th>E3 /S=0.5 mg/kg DM</th><th>E4 L/S = 1 mg/kg DM</th><th>E5 L/S = 3 mg/kg DM</th><th>E6 L/S = 5 mg/kg DM</th><th>E7 L/S = 10 mg/kg DM</th><th>Valorization Type 1 limits mg/kg DM</th><th>Valorization Type 2 limits mg/kg DM</th></tr></thead><tbody><tr><td>pH</td><td></td><td>12.4</td><td>12.21</td><td>12.05</td><td>11.96</td><td>11.87</td><td>11.58</td><td>11.32</td><td></td><td></td></tr><tr><td>Conductivity (µS/cm)</td><td></td><td>ND</td><td>250</td><td>2120</td><td>1940</td><td>1760</td><td>2380</td><td>2570</td><td></td><td></td></tr><tr><td>As</td><td>0.008</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt; LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>0.8</td><td>0.5</td></tr><tr><td>Ba</td><td>0.001</td><td>0.009</td><td>0.015</td><td>0.023</td><td>0.027</td><td>0.03</td><td>0.075</td><td>0.33</td><td>56</td><td>28</td></tr><tr><td>Cd</td><td>0.001</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt; LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>0.32</td><td>0.16</td></tr><tr><td>Cr</td><td>0.002</td><td>0.14</td><td>0.27</td><td>0.55</td><td>0.77</td><td>0.89</td><td>0.93</td><td>0.97</td><td>4</td><td>2</td></tr><tr><td>Cu</td><td>0.002</td><td>3.75</td><td>7.42</td><td>14.3</td><td>19.43</td><td>21.68</td><td>22.18</td><td>22.61</td><td>50</td><td>50</td></tr><tr><td>Hg</td><td>0.003</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt; LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>0.08</td><td>0.04</td></tr><tr><td>Mo</td><td>0.001</td><td>0.58</td><td>1.15</td><td>2.28</td><td>3.16</td><td>3.59</td><td>3.72</td><td>3.86</td><td>5.6</td><td>2.8</td></tr><tr><td>Ni</td><td>0.002</td><td>0.009</td><td>0.02</td><td>0.04</td><td>0.05</td><td>0.05</td><td>0.07</td><td>0.08</td><td>1.6</td><td>0.8</td></tr><tr><td>Pb</td><td>0.015</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt; LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>0.8</td><td>0.5</td></tr><tr><td>Sb</td><td>0.012</td><td>0.008</td><td>0.016</td><td>0.04</td><td>0.09</td><td>0.12</td><td>0.18</td><td>&lt;LoD</td><td>0.4</td><td>0.2</td></tr><tr><td>Se</td><td>0.011</td><td>0.008</td><td>0.016</td><td>0.03</td><td>0.04</td><td>&lt;LoD</td><td>&lt;LoD</td><td>&lt;LoD</td><td>0.5</td><td>0.4</td></tr><tr><td>Zn</td><td>0.001</td><td>0.05</td><td>0.10</td><td>0.25</td><td>0.42</td><td>0.51</td><td>0.59</td><td>1.19</td><td>50</td><td>50</td></tr><tr><td>Cl-</td><td>0.1</td><td>788</td><td>1566</td><td>3090</td><td>4325</td><td>4965</td><td>5469</td><td>5808</td><td>10000</td><td>5000</td></tr><tr><td>SO4<sup>2-</sup></td><td>0.1</td><td>110.5</td><td>218</td><td>418.7</td><td>587.5</td><td>689.9</td><td>734.3</td><td>749.3</td><td>10000</td><td>5000</td></tr></tbody></table>

n.a indicates not analyzed. LoD indicates Limit of Detection

<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /><figcaption>**Figure 2.** Bottom ash cumulative leaching concentrations of Cl- and Mo (mg/kg DM) compared to valorization threshold limits</figcaption></figure>

Cumulative value of Mo was 3.86 m /kg DM. Molybdenum is progressively mobilized when pH-values varies from 12.0 to 7.0 [20]. Mo forms mobile oxy-anions and several mineral phases are supposed to control its solubility: CaMoO₄ and Na₂MoO₄ [20].

Despite these results, bottom ash complied with the SETRA-LCPC limit values for Type 1 Valorization (pavement sub-layer or coated road shoulders structures) without environmental restrictions. For “Type 2” valorization (road embankment and fills), bottom ash needs treatment before utilization. Solidification with a hydraulic binder as cement could be a positively treatment.
## 3.2. Geotechnical characterization of bottom ash

**Particle size distribution:** The size distribution curve is built from the weight fraction of the sample passing through sieves of decreasing size. The obtained particle size distribution confirmed that the percentages passing to 2 mm and 80 µm are about 32% and 2.1% respectively, as shown in Figure 3. These values are lower than percentages specified by GTR guidelines¹ for bottom ash utilization, 50% and 12% respectively.

<figure><img src="image_6.png" /><figcaption>**Figure 3.** Bottom ash particle size distribution</figcaption></figure>

**Proctor compaction test:** This test was carried out with 10 mm sieved bottom ash. The moisture content and density of compacted sample is shown in Figure 4. Maximum dry density (which corresponds to the maximum compaction) reached by bottom ash was 1570.37 kg. m⁻³. This value is close to those determined for bottom ash in different countries (1530 to 1739 kg m⁻³[12]. Optimum moisture content was 12.5%. This optimum improves mechanical properties (reduced permeability, lift improvement and better compression resistant), especially for road sub-bases utilization.

<figure><img src="image_7.png" /><figcaption>**Figure 4.** Bottom ash Proctor compaction curve</figcaption></figure>

**Bearing capacity:** The CBR index is used to evaluate the strength of a compacted material by means of penetration resistance of a piston. The measured penetration and the corresponding load applied allow determining the CBR Index. The CBR index value for the tested bottom ash was approximately 40 and corresponds to proctor density, obtained with the optimal moisture content. According to GTR guidelines¹ the CBR index must be > 20 for considering bottom ash as a potential substitute in granular sub-bases. Tested bottom ash complies with this requirement.

**SBV:** The SBV was determined from a methylene blue test on sand fraction (0-2 mm). The methylene blue quantity was calculated (in grams) per 100 g of adsorbed material. The obtained value was 0.015, which is two times below the maximum value (0.03) recommended for bottom ash road sub-bases utilization.
According to French GTR guidelines, studied bottom ash complied with all geotechnical requirements for F61m class; therefore it can be employed as an alternative material in road construction.

### 3.3. Self-compacting material – technical and environmental assessments

The main purpose of formulation tests was to obtain a bottom ash based self-compacting material with suitable properties. These tests are performed on the formulation previously described (section 2.2). The formulation got an expected slump (160 mm) given by adjusted water amount with Abrams cone. This test is performed to check the workability of freshly made concrete. A mixture with 160 mm slump value is classified within high workability concrete (slump class S4) according to European Standard EN 206-1:2000.

**Compression test:** To validate the self-compacting material, it was necessary to check compressive strength from a representative number of cylinders cast from the same formulation batch. Six cylinders were used to determine the compression strengths at 28 days. The average value obtained was 0.4 MPa, which classifies the material as easy to dig (< 2MPa). This material would be suitable for roadways with traffic class T4 maximum, which corresponds to low traffic roads [14].

**Leaching test in batch (prEN 15863):**

Before utilization in road construction, an environmental assessment must be conducted by a standard long-term release test and compared with the thresholds values for monolithic products in building construction. Nevertheless, in France there are no environmental regulatory threshold limits for building materials. Thus, the results obtained for the monolith leaching test were compared against the Netherlands "Soil Quality Decree" of November 22, 2007.

The obtained values shown in Table 3 are well below the thresholds limits. Furthermore, Molybdenum and Chlorides concentrations which were column leaching test critical are far below the limit value. Only copper showed a significant leached concentration but do not exceed the threshold limit.

Therefore, leaching behavior of bottom ash based self-compacting material seems to be improved regarding non-treated bottom ash. In addition, the cement provides a highly buffered environment that limits the solubility of most trace elements by maintaining a high pH.

<table><caption>**Table 3.** Comparison of the cumulative release of heavy metal elements to the thresholds values of Soil Quality Decree.</caption><thead><tr><th>Parameter</th><th>Thresholds values for cumulative leaching quantities (values determined in 64<sup>th</sup> day in mg.m<sup>-2</sup>)</th><th>Release from Bottom ash self-compacting material (mg.m<sup>-2</sup>)</th></tr></thead><tbody><tr><td><strong>As</strong></td><td>260</td><td>&lt;LoD</td></tr><tr><td><strong>Ba</strong></td><td>1500</td><td>9.57</td></tr><tr><td><strong>Cd</strong></td><td>3,8</td><td>&lt;LoD</td></tr><tr><td><strong>Cr</strong></td><td>120</td><td>24.96</td></tr><tr><td><strong>Cu</strong></td><td>98</td><td>90.68</td></tr><tr><td><strong>Hg</strong></td><td>1,4</td><td>&lt;LoD</td></tr><tr><td><strong>Mo</strong></td><td>144</td><td>37.83</td></tr><tr><td><strong>Ni</strong></td><td>81</td><td>&lt;LoD</td></tr><tr><td><strong>Pb</strong></td><td>400</td><td>&lt;LoD</td></tr><tr><td><strong>Sb</strong></td><td>8,7</td><td>1.76</td></tr><tr><td><strong>Se</strong></td><td>4,8</td><td>&lt;LoD</td></tr><tr><td><strong>Zn</strong></td><td>800</td><td>7.17</td></tr><tr><td><strong>Sulphates</strong></td><td>165 000</td><td>57132.6</td></tr><tr><td><strong>Chlorides</strong></td><td>110 000</td><td>22145.7</td></tr></tbody></table>
## 4- CONCLUSIONS

Several attempts to use MSWI bottom ash as a substitute of aggregates in road construction materials are currently increasing. The restrictive factor for this utilization is usually not the technical properties, but rather the risk of environmental effects. Therefore, technical and environmental assessment is needed to evaluate bottom ash as a secondary raw material.

The new approach of SETRA- LCPC guidelines for assessing the environmental acceptability of alternative materials was accomplished in this study. The first stage corresponding to leaching behavior showed the critical leaching concentrations of Cu, Cr, Mo, Sb and Cl⁻, which exceeded the limit values for “All utilizations”. Nevertheless, they not exceed the limit values for “road utilizations”. For the second stage (column test), only Mo and Cl⁻ cumulative leaching concentrations exceeded “Type 2” valorization limit values. However, bottom ash complies with limit values for “Type 1” Valorization (pavement sub-layer or coated road shoulders structures) without environmental restrictions. These results fulfilled the suitable utilization for our self-compacting material.

Furthermore, the studied bottom ash complies with all geotechnical GTR guidelines requirements for road construction materials. Therefore, it could be considered as a potential substitute of natural aggregates.

Leaching test on monolith and mechanical compression test performed on self-compacting material were also satisfying. Thus, this material can be used for roadways with traffic class T4 and its leaching behavior complies with the Netherlands environmental regulatory threshold limits for building materials.

Moreover, to evaluate the self-compacting material under field conditions, a pilot-scale road must be constructed.

## ACKNOWLEDGEMENTS:

The authors wish to thank SITA- SUEZ, main sponsor of this study. We also acknowledge LGCIE geotechnical team for their facts and technical support.

## REFERENCES

[1] Amokrane, A., Blanchard, J. M., Billard, H., Chatelet-Snidarot, L., Delineau, T., Bourdier, C. (1998). Le devenir des machefers d'incinération d'ordures menageres. Partie 1 :Caracterisation des machefers. Dechets Sciences and Techniques 10, 15-27.

[2] Dabo, David (2008) *Impact environnemental des mâchefer d'incinération d'ordures ménagères (MIOM) valorisés en technique routière : caractérisation, expérimentations multi-échelles et modélisation hydro-géochimique*. Doctorat Hydrologie, hydrogéologie quantitatives, GEOSC-Centre de Géosciences, Paristech > ENSMP p.262.

[3] Aberg, A., Kumpiene, J., & Ecke, H. (2006). Evaluation and prediction of emissions from a road built with bottom ash from municipal solid waste incineration (MSWI). *The Science of the total environment*, 355(1-3), 1-12.

[4] SETRA LCPC 2011. Guide d'acceptabilité de materiaux alternatifs en technique routière- Evaluation environnementale.

[5] Bertolini, L., Carsana, M., de Cassago, D., Curzio, A., & Collepardi, M. (2004). MSWI ashes as mineral additions in concrete. *Cement and Concrete Research*, 34(10), 1899-1906.
[6] Hassan, H.F. (2005). Recycling of municipal solid waste incinerator ash in hot-mix asphalt concrete. *Construction and building materials*, 19(2). P 91-98

[7] Izquierdo, M., López-Soler., A, Vázquez Ramonich, E., Barra, M., & Querol, X. (2002). Characterisation of bottom ash from municipal solid waste incineration in Catalonia. *Journal of Chemical Technology & Biotechnology*, 77(5), 576-583.

[8] Forteza, R., Far, M., Seguí, C., & Cerda, V. (2004). Characterization of bottom ash in municipal solid waste incinerators for its use in road base. *Waste Management*, 24(9), 899-909.

[9] Dijkstra, J. J., Van Zomeren, A., Meeussen, J. C. L., & Comans, R. N. J. (2006). Effect of accelerated aging of MSWI bottom ash on the leaching mechanisms of copper and molybdenum. *Environmental science technology*, 40(14), 4481-4487.

[10] Meima, J. A., Van Zomeren, A., & Comans, R. N. J. (1999). Complexation of Cu with dissolved organic carbon in municipal solid waste incinerator bottom ash leachates. *Environmental science & technology*, 33(9), 1424-1429. American Chemical Society.

[11] Van Zomeren, A., & Comans, R. N. J. (2004). Contribution of natural organic matter to copper leaching from municipal solid waste incinerator bottom ash. *Environmental science technology*, 38(14), 3927-3932.

[12] Cornelis, Geert, Johnson, C. A., Gerven, T. V., & Vandecasteele, C. (2008). Leaching mechanisms of oxyanionic metalloid and metal species in alkaline solid wastes: A review. *Applied Geochemistry*, 23(5), 955-976.

[13] Cornelis, G, Van Gerven, T., & Vandecasteele, C. (2006). Antimony leaching from uncarbonated and carbonated MSWI bottom ash. *Journal of Hazardous Materials*, 137(3), 1284-1292.

[14] Van Gerven, T., Van Keer, E., Arickx, S., Jaspers, M., Wauters, G., & Vandecasteele, C. (2005). Carbonation of MSWI-bottom ash to decrease heavy metal leaching, in view of recycling. *Waste management*, 25(3), 291-300.

[15] Chrysochoou, M., & Dermatas, D. (2006). Evaluation of ettringite and hydrocalumite formation for heavy metal immobilization: Literature review and experimental study. *Journal of Hazardous Materials*, 136(1), 20-33.

[16] Meima, J. A., & Comans, R. N. J. (1997). The leaching of trace elements from municipal solid waste incinerator bottom ash at different stages of weathering, 14, 159-171.

[17] Chimenos, J. M., Fernández, A., Miralles, L., Segarra, M., & Espiell, F. (2003). Short-term natural weathering of MSWI bottom ash as a function of particle size. *Waste management*, 23(10), 887-95.

[18] Meima, J. A., & Comans, R. N. J. (1997). Geochemical Modeling of Weathering Reactions in Municipal Solid Waste Incinerator Bottom Ash. *Environmental Science & Technology*, 31(5), 1269-1276. American Chemical Society.

[19] Bendz, D., Tüchsen, P. L., & Christensen, T. H. (2007). The dissolution kinetics of major elements in municipal solid waste incineration bottom ash particles. *Journal of Contaminant Hydrology*, 94(3-4), 178-194.

[20] Chandler A.J., Eighmy T.T., Hartlén J., Hjelmar O., Kosson D.S., Sawell S.E., van der Sloot H.A. & Vehlow J. (1997). Leaching modelling in Municipal solid waste incinerator residues. Elsevier, Amsterdam, 607-734.1997d.

[21] SETRA-LCPC 1994. Guide technique pour « Remblayage des tranchées et réfection des chaussées » (mai 1994)