USE OF A HYDRAULIC BINDER COMPOSITION IN A METHOD FOR INERTING POLLUTED SOIL

Abstract

A method for inerting polluted soil, comprising adding to a polluted soil a composition comprising: from 40% to 99% of a sulfoaluminous clinker comprising as a phase composition, to the overall weight of the clinker: from 5% to 80% of a calcium sulfoaluminate phase possibly iron-doped corresponding to the formula C4AxFy$z in which x varies from 2 to 3; y varies from 0 to 0.5; and z varies from 0.8 to 1.2; from 0 to 25% of a calcium aluminoferrite phase of a composition corresponding to the general formula C.sub.6A.sub.xF.sub.y; x varies from 0 to 1.5; and y varies from 0.5 to 3; and from 10% to 70% of a belite phase C.sub.2S; and from 1% to 60% of a lime.

Claims

1. A method for inerting polluted soil, comprising adding to a polluted soil a composition comprising: from 40% to 99% of a sulfoaluminous clinker comprising as a phase composition, with respect to the overall weight of the clinker: from 5% to 80% of a calcium sulfoaluminate phase possibly iron-doped corresponding to the formula C4AxFy$z in which x varies from 2 to 3; y varies from 0 to 0.5; and and z varies from 0.8 to 1.2; from 0 to 25% of a calcium aluminoferrite phase of a composition corresponding to the general formula C.sub.6A.sub.xF.sub.y, x varies from 0 to 1.5; and y varies from 0.5 to 3; and from 10% to 70% of a belite phase C.sub.2S; and from 1% to 60% of a lime.

2. The method according to claim 1, wherein the clinker contains from 5% to 60% of a calcium sulfoaluminate phase possibly iron-doped C.sub.4A.sub.xF.sub.y$.sub.z.

3. The method according to claim 1, wherein x varies from 2.1 to 2.9.

4. The method according to claim 1, wherein y varies from 0.05 to 0.5.

5. The method according to claim 1, wherein the clinker contains from 0 to 20% of a calcium aluminoferrite phase C.sub.6F.sub.xF.sub.y with: x varying from 0.65 to 1.3; and y varying from 1.5 to 2.5.

6. The method according to claim 1, wherein the clinker contains from 20% to 70% of a belite phase C.sub.2S.

7. The method according to claim 1, wherein the lime is quicklime.

8. The method according to claim 7, wherein the composition contains from 1% to 30% of quicklime.

9. The method according to claim 1, wherein the lime is slaked lime.

10. The method according to claim 9, wherein the composition contains from 1% to 30% of slaked lime.

11. A composition for inerting a polluted soil comprising: from 70% to 98% of a sulfoaluminous clinker; and and from 2% to 30% of lime wherein the sulfoaluminous clinker comprising as a phase composition, with respect to the overall weight of the clinker: from 5% to 80% of a calcium sulfoaluminate phase possibly iron-doped corresponding to the formula C4AxFy$z in which x varies from 2 to 3; y varies from 0 to 0.5; and and z varies from 0.8 to 1.2; from 0 to 25% of a calcium aluminoferrite phase of a composition corresponding to the general formula C.sub.6A.sub.xF.sub.y x varies from 0 to 1.5; and y varies from 0.5 to 3; and from 10% to 70% of a belite phase C.sub.2S.

12. The composition according to claim 11, wherein it comprises from 70% to 97% of a sulfoaluminous clinker as defined in any of claims 1 to 6.

13. The composition according to claim 12, wherein it comprises from 75% to 95% of a sulfoaluminous clinker as defined in any of claims 1 to 6.

14. The composition according to claim 11, wherein it comprises from 3% to 30% of lime.

15. The composition according to claim 14, wherein it comprises from 5% to 25% of lime.

16. The composition according to claim 11, wherein the lime is slaked lime.

Description

EXAMPLE 1SULFOALUMINOUS CLINKER USED IN THE CONTEXT OF THE PRESENT INVENTION

Example 1.1Alpenat

[0095] The clinker Alpenat from the company Vicat has been used for the tests conducted in the context of the present invention. The chemical and mineralogical compositions of this clinker are reported respectively in the following Tables 1 and 2.

TABLE-US-00001 TABLE 1 ALPENAT Chemical composition Oxides % (w/w) SiO.sub.2 10.55 Al.sub.2O.sub.3 23.46 CaO 45.07 MgO 1.00 Fe.sub.2O.sub.3 9.70 TiO.sub.2 1.29 K.sub.2O 0.27 Na.sub.2O 0.17 P.sub.2O.sub.5 0.11 Mn.sub.2O.sub.3 0.01 SO.sub.3 8.07 SrO 0.06 Cl 0.01 Loss on ignition 0.23

TABLE-US-00002 TABLE 2 ALPENAT Mineral phase Mineral phase % (w/w) C.sub.4A.sub.3$ 54.3 C.sub.6AF.sub.2 1.2 C.sub.2S.sub. 20.8 C.sub.2S.sub.high 8.3 C.sub.3MS.sub.2 4.5 C$ 0.4 Quicklime 0.2 -Fe.sub.2O.sub.3 1.0 C.sub.3FT 9.3

Example 1.2CHC011

[0096] The clinker CHC011 from the company Vicat has been used for the tests conducted in the context of the present invention. The chemical and mineralogical compositions of this clinker are reported respectively in the following Tables 3 and 4.

TABLE-US-00003 TABLE 3 Clinker CHC011 Chemical composition Oxides % (w/w) SiO.sub.2 6.05 Al.sub.2O.sub.3 68.40 CaO 30.65 MgO 0.17 Fe.sub.2O.sub.3 0.09 TiO.sub.2 0.01 K.sub.2O 0.05 Na.sub.2O 0.19 P.sub.2O.sub.5 0.12 Mn.sub.2O.sub.3 0.01 SO.sub.3 11.11 SrO 0.39 Cl 0.01 Loss on ignition 1.96

TABLE-US-00004 TABLE 4 Clinker CHC011 Mineral phase Mineral phase % (w/w) C.sub.4A.sub.3$ 76 C2AS 6.5 C.sub.2S.sub. 12 C.sub.2S.sub.high 4 C.sub.3MS.sub.2 0.5 C$ 0.8 Quicklime 0.2

EXAMPLE 2INERTING COMPOSITION ACCORDING TO THE INVENTION

[0097] Compositions comprising: [0098] 80% of the clinker Alpenat according to the Example 1.1 and 20% of slaked lime (laboratory product: calcium hydroxide for analysis, purity 96%)composition 1; [0099] 75% of the clinker Alpenat according to the Example 1.1 and 25% of quicklimecomposition 2; [0100] 75% of the clinker CHC011 according to the Example 1.2 and 25% of slaked lime (laboratory product: calcium hydroxide for analysis, purity 96%)composition 3; and 75% of the clinker CHC011 according to the Example 1.2 and 25% of quicklimecomposition 4; [0101] have been prepared by mixing the two components in a mortar mixer for 60 seconds at a speed of 140 rpm.

EXAMPLE 3INERTING OF A POLLUTED SOIL

[0102] 3.1Polluted Soil

[0103] In the context of the conducted tests, silt (clayey sand) artificially sulfated so as to increase its sulfate content beyond the limit value of 1000 mg/kg of a dry matter set according to the decree in force (Decree of Dec. 12, 2014 relating to the conditions of admission of inert wastes in plants under headings 2515, 2516, 2517 and in plants for storing inert wastes under heading 2760 of the classified plants nomenclature, JORF No. 0289 of Dec. 14, 2014, page 21032, text No. 11) has been used.

[0104] For this purpose, silt has been mixed with 2% (w/w) of laboratory gypsum (mixing for 5 min at 140 rpm). The obtained composition is reported in the following Table 3.

TABLE-US-00005 TABLE 3 Composition of the soil (gypsum silt) Silt + 2% of Gypsum Limit values Average DMR 105 C._Dry matter rate 85.5 HR 105 C._Humidity rate 16.9 Eluate volume (m) 580 Temperature ( C.) 20.3 pH 8.1 Conductivity (S/cm) 1604 Measured element mg/kg of dry matter (DM) As 0.5 <0.01 Ba 20 0.47 Cd 0.04 <0.01 Cr 0.5 <0.05 Cu 2 <0.05 Mo 0.5 <0.05 Ni 0.4 <0.05 Pb 0.5 <0.05 Sb 0.06 <0.01 Se 0.1 <0.01 Zn 4 1.99 Chloride 800 23.3 Fluoride 10 2.93 Sulfate 1000 12375 Hg 0.01 <0.005 Fraction soluble at 105 C. 4000 16223

[0105] 3.2Inerting Method

[0106] The gypsum silt is dry-mixed with one of the compositions 1 to 4 in a mortar mixer in accordance with the standard EN 196-3 (mixture for 60s at 140 rpm). Afterwards, the (ultrapure) water is added with a water-to-binder ratio equal to 1. Afterwards, mixing is continued for 120s at 140 rpm and then for 120s at 285 rpm.

[0107] The sample thus prepared is stored in a closed plastic bag for the desired maturation time.

[0108] In order to monitor the amount of water in the mixture, a fraction of the sample is crushed so as to be all passing at 4 mm, and then dried at 105 C.

[0109] 3.3Experimental Protocol

[0110] 3.3.1Standard NF-EN-12457-2 (December 2002)

[0111] The leaching tests have been carried out according to the protocol described in the standard NF EN 12457-2, namely: [0112] reduction of the grain-size distribution of the sample (95% of the particles must be smaller than 4 mm), [0113] determination of the dry matter rate and of the humidity rate, [0114] leaching test with stirring for 24 hours in a liquid-to-solid ratio equal to 10, [0115] filtering and analyses of the leachate by ICP, ion chromatography and infrared mercury analysis.

[0116] A leaching test is conducted on the gypsum silt described at item 3.1 non-inert, which allows obtaining a reference point.

[0117] Furthermore, different maturation times (time elapsed between the addition of the binder to the silt and the leaching test which corresponds to the hydration duration of the binder) have been tested in order to check the rapidity and the evolution of the inerting over time.

[0118] 3.3.2 Assessment of the Sulfates Content Found in Leachates

[0119] The sulfates contents in the leachates have been measured by ion chromatography according to the standard NF EN ISO 10304-1.

[0120] 3.3.3 Assessment of the Amount of Chromium Found in Leachates

[0121] The chromium contents in the leachates have been measured by inductively coupled plasma (ICP) spectrometry according to the standard NF EN ISO 11885.

[0122] 3.3.4Results and Conclusions

[0123] The obtained results are reported in FIGS. 1 to 6.

[0124] Note that an addition of 8% of the clinker Alpenat to the gypsum silt allows, after 7 days of maturation, capturing the sulfates (FIG. 1) satisfactorily but the leached chromium content is higher than the admissible limit for allowing classifying a waste as inert.

[0125] However, a further addition of slaked lime (within a proportion of 80% Alpenat/20% slaked limecf. Examples 1 and 2) allows not only obtaining a more effective and more rapid capture of the sulfates (FIG. 1) but also overcoming the problem of chromium release by lowering the leached chromium content to a value below the limit of 0.5 mg/kg of dry matter after 3 days. Furthermore, the conducted experiments prove that the leached chromium content does not increase over time.

[0126] Similarly, a further addition of quicklime (within a proportion of 75% Alpenat/25% quicklime) allows, after 7 days, lowering the chromium and sulfates contents below the authorized limits (FIGS. 3 and 4).

[0127] The addition of 8% of the clinker CHC011 to the gypsum silt does not allow capturing enough sulfates and chromium, after a 7-day maturation time. However, the capture of these pollutants is improved if an addition of slaked lime or quicklime (within a proportion of 75% clinker CHC011/25% quicklime or slaked lime) is performed on this clinker (FIGS. 5 and 6).