NATURAL STONE MUDS AS SECONDARY RAW MATERIALS: TOWARDS A NEW SUSTAINABLE RECOVERY PROCESS

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1 NATURAL STONE MUDS AS SECONDARY RAW MATERIALS: TOWARDS A NEW SUSTAINABLE RECOVERY PROCESS Rossana Bellopede Department of Environment, Land and Infrastructure Engineering POLITECNICO DI TORINO Fifth Prometia Scientific Seminar, Berlin, 13/12/2018

2 (sept sept 2019) is a commitment which aims at generating specific actions against two relevant problems in EU: waste generation in construction industry and access to raw materials, mainly industrial minerals and metals Critical Raw Materials. OBJECTIVES - Joint Research & Innovation Actions - Increase the commitment s impact and creating a stronger network of stakeholders. - Identifying calls related to the commitment mission, mainly in H2020, and developing project proposals.

3 Sludge derives from different processes: quarrying; processing stone. Processing stone are divided in: Volume treatment: Gangsaw; Diamond sawblade; Diamond wire. Superficial treatment: flaming; sanding; polishing.

4 Sludge waste represents the finest part of the waste produced by the cutting and processing of ornamental stones and results to have a composition that depends on: Type of cutting materials Sludge deriving from cutting of: Silicatic rock; Carbonatic rock. Cutting methodologies Gangsaw Metal grit; Diamond tools Diamond sawblade; Diamond wire. Metals concentration: Cr, Mn with Fe in metal grit Alloys Co, Cr, W, Mo, Mn, Ni, Si

5 CUTTING PROCESSES AND TREATMENT OF ORNAMENTAL STONE WHAT THE EUROPEAN DIRECTIVE PROVIDES [Directive 2006/21/CE of 15 March 2006] : - Reduction of generated waste - Decreased use of "Critical Raw Materials" (essential raw materials) - No landfill disposal and reduction of potential soil contamination - Prevention of transport of hazardous waste - Reduction of energy consumption - No impact on air pollution - Cost reduction AIM OF RESEARCH: To find a sustainable way to manage and recover such waste materials, in order to reduce the costs connected to their management and to the potential environmental impacts due to their disposal, and contemporary, producing alternative products which could help to reduce the use of natural resources (resource efficiency).

6 R E G U L A T O R Y F R A M E W O R K

7 M.D. 5 april 2006 n. 186 Leaching test Annex 3 Parameters M.U. Concentration limits NO3 mg/l 50 F mg/l 1.5 SO4 mg/l 250 Cl mg/l 100 Cn µg/l 50 Ba mg/l 1 Cu mg/l 0.05 Zn mg/l 3 Be µg/l 10 Co µg/l 250 Ni µg/l 10 As µg/l 50 V µg/l 250 Cd µg/l 5 Cr µg/l 50 Pb µg/l 50 Se µg/l 10 Hg µg/l 1 Asbestos mg/l 30 COD mg/l 30 Ph 5.5<>12.0 Metals concentration limits Chemical analysis Annex 5 title V part IV D.Lgs. 152/06 Parameters Column A green site Column B industrial public site [mg/kg site [mg/kg ss] ss] As Cd 2 15 Co Ni Pb Cu Zn Hg 1 5 Hydrocarbo ns C> Cr Cr VI 2 15 Asbestos

8 INVESTIGATED MATERIALS SILICATE SLUDGE GSS - Sludge from gangsaw using abrasive steel shot: characterised by a high percentage of Ni, Cr, Cu, etc DSS - Sludge from multi diamond-saw block cutter: characterised by Co and Cu high content MS - Mixed sludge- from gangsaw and block cutter Water treatment plant: residual sludge (wet) Multi diamond wires GSS - Dry Diamond frame saw DSS - Dry Steel-shot Gangsaw 8

9 STONES CHARACTERIZATION CUTTING CLASSIFICATION Identification of the best available techniques for extraction and processing of stones in order to obtain less waste and less pollution, in accordance with the European directive. Zichella et al. 2016

10 MAIN CHALLENGES FOR CORRECT WASTE MANAGEMENT HUGE VOLUME produced in quite limited areas (eg. Ossola Valley or Pietra di Luserna quarry basin, considering Piedmont Region subjects of the present research). Source: Report IRES

11 MAIN CHALLENGES FOR CORRECT WASTE MANAGEMENT Very FINE PARTICLES distribution of the sludge (leads to a silt-clay physical behavior), connected to low permeability and axphyxit condition that make sludge not completely suitable for the production of substrates. DSS: Diamond frame Saw Sludge GSS: Gangue Saw Sludge MS: Mixed Sludge VCO: Verbano Cusio Ossola quarry basin LS: Luserna Stone quarry basin 11

12 MAIN CHALLENGES FOR CORRECT WASTE MANAGEMENT CHEMICAL PROPERTIES of the waste: presence of metals and TPH, sometimes over the threshold values, which can polluted water and soil if residual sludge are not properly managed. 12

13 TREATMENT AND POTENTIAL REUSE OF SLUDGE Eriez Magnetic separator (Kolm-type high gradient magnetic separator.) Source: Oberteuffer, 1974

14 MAGNETIC SEPARATION Magnetic Fraction% Amagnetic Fraction % GSS-VCO GSS-LS DSS-VCO 1 99 DSS-LS MS-VCO MS-LS Magnetic separation shows that the amount of magnetic fraction obtained depends on the cutting technology used, and on the type of cut stone. Gangsaw (GSS) technology produce high percentage of magnetic fraction due to the presence of metallic grit. Diamond saw Blade (DSS) technology produce low percentage of magnetic fraction due to low wear of tools. The chemical composition of the metal matrix of tools directly impact on the efficiency of cutting action. TREATMENT AND POTENTIAL REUSE OF SLUDGE magnetic fraction amagnetic fraction SEM analysis show that in the magnetic fraction, the presence of some minerals such as Biotite (paramagnetic) is found. The amagnetic fraction present some minerals with metallic part due to the very fine particles of the sludge, which creates the problem of packaging. 14

15 TREATMENT AND POTENTIAL REUSE OF SLUDGE IMAGE ANALYSIS (free ImageJ software) Polarized image Crossed nicols image Overlayed image Selection of metal fraction using the RGB thresholding Selection of grain using the RGB thresholding Selection mask of metal fraction

16 PLASTER WITH ECOFILLER REUSE OF SLUDGE WITH LOW METALS CONCENTRATION MIX DESIGN TECHNICAL CHARACTERIASTICS Components kg/m 3 Portland Cement 42,5R 313 Lime Parex NHL 3,5 38 Sand Luserna 0/3 mm 813 Ecofiller Luserna Stone 187 Fiber 0,4 0.3 Total Foam density 70 gr 25.9 Liter 370 Min Water 40% CEM Total water (*) 325 (*) greater dosage of water for the heat temperature Fresh density Dry volume mass Fresh slump test Thermal Conductivity - 15 days Thermal Conductivity - 68 days Thermal Conductivity dry condition: Pull off Compressive strenght Compressive strenght after freeze and thaw Compressive strength class (UNI EN998-2) Compressive strength category (UNI EN 998-1) flexural strength flexural strength after freeze and thaw kg / m kg/m^3 Hargerman cone diameter: 100mm; sample diameter: 100mm W/m*K W/m*K W/m*K 1.55 MPa 11.97MPa MPa M10 CS IV 1.03 MPa 0.93 MPa

17 HYDROSEEDING REUSE OF SLUDGE WITH LOW METALS CONCENTRATION MIX DESIGN Components kg/m3 Topsoil 500 Cellulose 0.3 Ecofiller Baveno 0/ Total Water 20% Total water(*)? (*)higher dosage of water for the heat

18 REUSE OF SLUDGE WITH HIGH METALS CONCENTRATION CLSM Concrete low strenght material Analysis carried out: - Sludge quartz content - Sludge and aggregate distribution size - Sludge metal content with magnetic separation - Sludge and aggregate specific gravity - Flowability - Mix design - Triaxial test - Thermal conductivity - Leaching test

19 REUSE OF SLUDGE WITH HIGH METALS CONCENTRATION P [%] CLSM Concrete low strenght material Mix design Particle size distribution Materials Gangsaw Sludge Mix Diamond tools sludge Quartzite 0-8 mm Quartzite 8-16 mm Portland Cement Additive Description Gangsaw with metal grit Serizzi, beola Diamond saw blade, diamond wire Granitie, serizzi 97% Si CEM I 42,5 R with specific density 3,15 g/cc. ADVA Flow 455 superfluidificant Mix design Cement content [kg/m 3 ] sludge M50 50 M M M G50 50 G G G Aggregatesi Quarzi te 0-8 Quarzi te 8-16 M sludge G sludge 0 0,001 0,01 0,1 D [mm] Specific density [g/cm 3 ) M G Quartzite 8-16 mm Quartzite 0-8 mm 2.552

20 REUSE OF SLUDGE WITH HIGH METALS CONCENTRATION CLSM Concrete low strenght material Metal content Quartz content Sludge % metals concentration M 2,96 G 0,76 Sludge % Quartz M G 46.02

21 REUSE OF SLUDGE WITH HIGH METALS CONCENTRATION CLSM Concrete low strenght material Mix Design determination and preparation Determination of the optimal water content based on: - spreading diameter [22-25 cm]; - absence of bleeding or segregation phenomena. Miscela M50-> A/P 0.85

22 CLSM Concrete low strenght material REUSE OF SLUDGE WITH HIGH METALS CONCENTRATION Thermal conductivity Test 18 days of maturation in dry condition Performed Cylindrical samples 12 samples, 3 for mixing type. Sensor KD-2 Pro Porbe RK-1 lenght 6 cm e diameter 3.9 mm. 3 measures for sample Triaxial cell test with repeated loading

23 REUSE OF SLUDGE WITH HIGH METALS CONCENTRATION M R,m [MPa] CLSM Concrete low strenght material 1000 M50_0.85 Triaxial cell test results with repeated loading 28 days of maturation 1000 M100_0.75 G100_0.75 Sludge type influence G50_0.75 M100_ MR,m [MPa] 100 G100_0.75 Limite inferiore Limite superiore 1000 Cement content influence G50_ ,01 0,10 1,00 q [MPa] 10 0,01 0,10 1,00 q [MPa] M R,m [MPa] 100 G100_0.75 The resilient response of each mixture is found within the typical range of traditional non-binding granular materials 10 0,01 0,10 1,00 q [MPa]

24 REUSE OF SLUDGE WITH HIGH METALS CONCENTRATION CLSM Concrete low strenght material Thermal conductivity results 18 days of maturation Dry condition Oven for 48 h at 60 -> simulate operating conditions w e t d r y w e t d r y w e t d r y w e t d r y CLSM standard-> W/(m*K)

25 From chemical and physical characterization : sludge as such can cause environmental impacts if not properly managed. Magnetic separation can be useful: -to decrement metals content, with a decrement of the impacts associated to them -to obtain a by-product to use in different applications Plaster and hydroseeding: reuse foreseen only if the sludge comes from the cutting with diamond tools and only if the concentration limits of the metals are in accordance with the regulations. CLSM: reuse intended for all kind of stone muds especially if they are characterized by a high metals content: presence of metals, and quartz content, are useful for dissipating the energy produced by the electric cables in the sub-floors of the tunnels.

26 .and what about the metal fraction in the stone muds?

27 Thanks for your attention