Hydraulic binder comprising bivalve mollusc shell powder, mechanochemical activation method and construction material comprising

Abstract

The invention relates to a hydraulic binder composition comprising shell powder of at least one bivalve mollusc and at least one other component selected from the group including slaked lime, quicklime, sulfate source materials, granulated and ground blast furnace slag, ground conversion steel slag, paper mill ash, fly ash, Portland cement and standardized composite cements, crushed pozzolans, crushed calcined shales, crushed calcined clays, limestone fillers, alone or in mixture, wherein said shell powder of at least one bivalve mollusc has a d50 between 15 µm and 50 µm and a D90 less than or equal to 100 µm.

Description

Title of the invention: Hydraulic binder comprising bivalve mollusc shell powder, mechanochemical activation method and construction material comprising Technical field

[0001] The present invention relates to the field of hydraulic binders, in particular road cements and hydraulic binders (HRBs), and materials comprising them, as well as the activation of said road cements and hydraulic binders.

[0002] In particular, the present invention relates to materials and soils treated with road cements and / or hydraulic binders for construction materials, concrete, base and subgrade of pavements, such as road aggregates, composed of natural and / or recycled aggregates and sands (aggregates from bituminous mixes, crushed concrete, incineration bottom ash) and natural soils (silts, sands). Prior art

[0003] The manufacture of clinker and cement requires the calcination of limestone in the presence of an alumina and silica source at high temperatures of 1450 °C. The direct release of CO2 from calcination is responsible for 80% of the greenhouse gas emissions from cement manufacturing. A large portion of the remaining emissions comes from the combustion of fossil fuels for calcination, as well as from excavation, transport, and grinding processes [R. Maddalena et al., 2018]. In France, cement production is responsible for approximately 5% of CO2 emissions into the atmosphere. The manufacture of one tonne of bulk CEM I ready for shipment generates 0.748 tonnes of CO2 [Infociments, January 15, 2024].One of the major objectives in the field of construction is to reduce CO2 emissions related to clinker production and to valorize several waste products into useful products such as fly ash from thermal power plants or biomass (CV), blast furnace slag (BFS) from pig iron production, conversion steel mill slag (CSM) from steel production, mining waste, etc.

[0004] Thus, reducing the impact of human activity on the environment is a major global challenge today. The main action for preserving the environment is to drastically reduce carbon dioxide (CO2) emissions in order to slow the overall rise in global temperature. Another key action is the recycling and recovery of secondary materials (industrial by-products, alternative materials, waste) in order to limit the use of natural resources and thus avoid their scarcity.

[0005] In France, the Energy Transition for Green Growth Act sets out several objectives, including: • Reduce greenhouse gas emissions by 40% between 1990 and 2030 and reduce greenhouse gas emissions by a factor of four between 1990 and 2050, • The scenario of the National Low Carbon Strategy (SNBC) provides for the non-metallic mineral production sector a reduction of emissions of 24% in 2030 and 85% in 2050 respectively compared to 2015. • Reduce the amount of waste sent to landfills by 50% by 2025 and gradually decouple economic growth from raw material consumption, • Reuse, direct towards recycling or other forms of recovery at least 70% of the materials and waste produced on road construction or maintenance sites.

[0006] Road hydraulic binders (RHBs) and standardized cements (EMCs) are major constituents of materials used in public works, civil engineering, and construction. However, the manufacturing processes for these common binders, such as traditional Portland cement (EMC I), generate considerable CO2 emissions. Consequently, alternative, low-carbon hydraulic binders, which emit less CO2 than Portland cement, have been developed and are still being investigated by several cement manufacturers. In particular, co-products from other industries can be used as the main constituent of road hydraulic binders. These co-products include granulated and ground blast furnace slag (BFFS), ground conversion steelmaking slag (CBS), pozzolans, limestone filler, and fly ash (FA) from coal or biomass, and more recently, recycled concrete fines.

[0007] Granulated and ground blast furnace slag, produced from the manufacture of pig iron from iron ore at high temperature (1250°C), has been used for many years in hydraulic binders and standardized compound cements, in addition to clinker. Several technical advantages of LHF have been demonstrated in road construction materials compared to traditional Portland cement (CEM I): slow and continuous setting kinetics, improved workability time, reduced cracking, and better durability. However, the use of granulated and ground LHF in hydraulic binder and cement compositions remains limited since many of them contain only a small proportion of LHF, less than 50%, the remaining constituents being mainly CEM I, which allows for rapid setting kinetics and mechanical performance over time. Furthermore, the tonnages of LHF will decrease in the coming years, with decarbonization and changes in the manufacturing processes of cast iron and steel.

[0008] Consequently, the development of low-carbon binders and cements is recognized as an option for reducing CO2 emissions. Binders such as geopolymers (GP) and alkali-activated binders (AA) represent alternatives to conventional Portland cement. These binders are obtained by the alkali activation of aluminosilicate sources, which are often industrial waste (CV, LHF, etc.) or calcined clays such as metakaolin. The latter have been the subject of much research in recent decades due to their lower environmental impact and higher durability compared to Portland cement-based materials [P. Cong and Y. Cheng, 2021; AZ Khalifa et al., 2020]. Despite the advantages of geopolymers, their formulation seems more difficult to control, which hinders their use [Martin CYR., CAN WE FORMULA A GEOPOLYMER OR AN ALKALI-ACTIVE BINDER LIKE A PORTLAND CEMENT? », NoMaD Conference 2018\.The practical problems associated with handling large quantities of viscous, corrosive, and hazardous alkaline activator solutions, which pose significant health risks, have slowed the development of geopolymers, hence the need to propose new manufacturing methods. The long-term durability of these binders is still poorly understood and controlled.

[0009] There is therefore an important need to develop gentler activation methods that present less risk to the user and have a low impact on the environment.

[0010] The present invention aims to achieve at least one of the following objectives: -01- To propose a hydraulic binder composition with a lower environmental impact than existing compositions. -02- Propose a hydraulic binder activation method that is more environmentally friendly than existing methods. -03- Propose a method for activating hydraulic binders that presents less risk to the user than existing methods. -04- Propose a method for activating a hydraulic binder without solvent, in this case mechanochemical activation. -05- Valorizing waste, such as bivalve mollusc shells, for the manufacture of hydraulic binder compositions. Summary

[0011] At least one of the objectives is achieved through a hydraulic binder composition comprising shell powder of at least one bivalve mollusc and at least one other component selected from the group including slaked lime, quicklime, the sulfate source materials, granulated and ground blast furnace slag, ground conversion steel slag, paper mill ash, fly ash, Portland cement and standardized compound cements, ground pozzolans, ground calcined shales, ground calcined clays, limestone fillers, alone or in mixture, wherein said shell powder of at least one bivalve mollusc has a d50 between 15 pm and 50 pm and a D90 less than or equal to 100 pm.

[0012] According to another aspect, construction materials are offered, concretes, treated materials for road base, for soft mobility, treated soils for earthworks, comprising the composition of cement and hydraulic road binder described above and a mixture of aggregates and sand, natural and / or recycled, as well as natural or excavated soils.

[0013] According to an additional aspect, it is proposed to use a powder of shells of at least one bivalve mollusc, having a d50 between 15 pm and 50 pm and a D90 less than or equal to 100 pm for the manufacture of cement and road hydraulic binder.

[0014] The invention also relates to a method for manufacturing said treated material comprising a cold mixing step, advantageously between 10°C and 40°C, of ​​said road hydraulic binder composition according to the invention and natural and / or recycled aggregates and sand. Brief description of the drawings Fig. 1

[0015] [Fig.1] shows photographs, from left to right, of a whole and washed scallop shell, crushed into sand, ground into powder. Fig. 2

[0016] [Fig.2] shows the particle size curves of a scallop powder according to the invention. Fig. 3

[0017] [Fig.3] shows, according to one embodiment, the mechanical performance (simple compressive strengths) obtained according to the standard NF EN 196-1 (standardized mortars 4x4x16 cm) on CEM II A-LL 42.5 R and on a binary mixture of this cement substituted by different rates of scallop shell powder, ranging from 0% by weight to 50% by weight. Fig. 4

[0018] [Fig.4] shows, according to one embodiment, the mechanical performance (simple compressive strengths) obtained according to the standard NF EN 196-1 (standardized mortars 4x4x16 cm) on CEM II A-LL 42.5 R and on a ternary mixture of this cement substituted by different rates of scallop shell powder and LHF, in equal parts (50-50), ranging from 0% by weight to 90% by weight. Fig. 5

[0019] [Fig. 5] shows, according to one embodiment, the mechanical performance (simple compressive strengths) obtained according to standard NF EN 196-1 (standardized 4x4x16 cm mortars) on two CEM II A-LL 42.5 R cements of equivalent composition but from different origins (North and Normandy) and on two formulations of said hydraulic binder using these cements, LHF, and scallop shell powder. Fig. 6

[0020] [Fig.6] shows the mechanical performance of materials for road base according to their simple compressive strength (Rc) at 3, 7 and 28 days according to standard NF EN 13286-41 on test pieces with a diameter of 10 cm and a height of 20 cm made by vibro-compression according to standard NF EN 13286-52 of materials for road base. Fig. 7

[0021] [Fig.7] shows, the direct tensile strength (Rt) and the modulus of elasticity (E) at 28, 60 and 360 days according to the standards NF EN 13286-40 and NF EN 13286-43 on test pieces with a diameter of 16 cm and a height of 32 cm made by vibro-compression according to the standard NF EN 13286-52 of materials for road base. Detailed description

[0022] The composition of hydraulic binder

[0023] As mentioned previously, the invention relates to a hydraulic binder composition comprising shell powder of at least one bivalve mollusc and at least one other component selected from the group including slaked lime, quicklime, sulfate source materials, granulated and ground blast furnace slag, ground conversion steel slag, paper mill ash, fly ash, Portland cement and standardized composite cements, crushed pozzolans, crushed calcined shales, crushed calcined clays, limestone fillers, alone or in mixture, wherein said shell powder of at least one bivalve mollusc has a d50 between 15 pm and 50 pm and a D90 less than or equal to 100 pm.

[0024] A hydraulic binder is a material that allows granular compounds or soil particles to be bound together by reaction with water so that the final material is cohesive.

[0025] Advantageously, said hydraulic binder is a cement or a road hydraulic binder.

[0026] A road hydraulic binder (RHB) is applicable to the road sector. As specified in standards NF P 15-108, NF EN 13282-1 and NF EN 13282-2, RHBs are intended for the treatment of aggregates and soils for the production of road bases, subgrade and earthworks, stabilized materials.

[0027] A cement, as specified in standards NF EN 197-1, NF EN 197-5, NF EN 197-6 and NF EN 206, is more generally applicable to the field of building and civil engineering.

[0028] In addition, the hydraulic binder composition according to the invention may include one or more of the secondary components as defined in standards NF P 15-108, NF EN 13282-1 and NF EN 13282-2, NF EN 197-1, NF EN 197-5 and NF EN 197-6.

[0029] Powdered shells of at least one bivalve mollusc

[0030] In one embodiment, the bivalve mollusc is chosen from the group including the scallop, the clam, the oyster and mixtures thereof, preferably, said bivalve mollusc is the scallop.

[0031] Advantageously, said bivalve mollusc shell comprises at least 65% by weight of limestone, advantageously at least 75% by weight of limestone and more advantageously at least 95% by weight of limestone.

[0032] Generally, in the hydraulic binder composition according to the invention, the shell powder of at least one bivalve mollusc is present in an amount between 5% by weight and 50% by weight, preferably between 10% by weight and 40% by weight and more preferably between 25% by weight and 35% by weight.

[0033] In a preferred embodiment, said shell powder of at least one bivalve mollusc, in analysis by laser granulometry in water, has a d50 between 15 pm and 40 pm, preferably between 16 pm and 30 pm and preferably between 17 pm and 20 pm, and preferably a d90 less than or equal to 100 pm, more preferably less than 80 pm and even more preferably about 60 pm.

[0034] At least one other component

[0035] In the list of other components above, Portland cement and standardized composite cements, as well as granulated and ground blast furnace slag, alone or in mixtures, are preferred.

[0036] Thus, in one embodiment, the hydraulic binder composition according to the invention comprises up to 45% Portland cement, advantageously between 10% and 40% by weight, more advantageously between 15% and 35% by weight and / or up to 50% by weight of granulated and ground blast furnace slag, advantageously between 10% and 45% by weight, more advantageously between 20% and 40% by weight.

[0037] Applications of shell powder from at least one bivalve mollusc

[0038] As mentioned previously, the invention also relates to the use of a powder of shells from at least one bivalve mollusc, having a d50 between 15 pm and 50 pm and a D90 less than or equal to 100 pm for the manufacture of cement or road hydraulic binder.

[0039] Indeed, the composition according to the invention is particularly suitable when it comes to a hydraulic road binder for the production of treated material for road base courses, subgrade courses, earthworks, and stabilized materials for active transportation. This material may comprise, for road base courses, in addition to the hydraulic binder composition according to the invention, a mixture of aggregates and sand, natural and / or recycled, the aggregates and sand preferably consisting of at least 80% by weight of recycled asphalt, advantageously 100% by weight.

[0040] Treated material for road base

[0041] The material treated according to the invention can be used in the road base course, both as a foundation layer and as a base course.

[0042] The material may advantageously contain recycled asphalt, which may, in particular, come from the milling or crushing of the surface layers (wearing, bonding) and / or the base layer of an old roadway.

[0043] In an advantageous embodiment, the aggregates and sand consist of at least 80% by weight of recycled asphalt, advantageously of 100% by weight.

[0044] In a preferred embodiment, the road hydraulic binder composition according to the invention represents between 3.5% and 5.5% by weight of said treated material for road base, preferably between 4% and 5% by weight, more preferably 4.5% by weight.

[0045] In a particular embodiment, the treated road base material according to the invention further comprises up to 20% by weight of corrective sand. The corrective sand is natural and / or recycled sand and serves to correct the particle size distribution of the material when the latter does not, as is, contain a sufficient number of fine particles.

[0046] Preferably, the road base materials treated with said hydraulic binder according to the invention, exhibit the mechanical resistances corresponding to the standard NF EN 14-227-5 on granular mixtures treated with road hydraulic binders, with a performance class T3 at 360 days of curing.

[0047] Process for manufacturing the treated material

[0048] As mentioned above, the invention also relates to a method for manufacturing said treated material comprising a cold mixing step, advantageously between 10°C and 40°C, of ​​said road hydraulic binder composition according to the invention and natural and / or recycled aggregates and sand.

[0049] The term "cold" means not supplying heat energy; in other words, a cold process is a process carried out at the ambient temperature of the place where it is implemented.

[0050] In a particular embodiment, the process according to the invention is carried out in a mixing plant. In other words, the cold mixing of said binder composition and aggregates is performed at the factory. The resulting material is then transported to the construction site for which it is intended.

[0051] In another embodiment, the process according to the invention is carried out directly on site, during the reprocessing of pavement materials, using a dedicated workshop. This includes spreading said hydraulic road binder composition according to the invention, milling the pavement materials, mixing, optionally adding water, and compacting the treated material. In particular, the process according to the invention can be implemented with the ARC® 1000 (1000 Cv Pavement Reprocessing Workshop) processes of EIFFAGE Route. Examples

[0052] Example 1: Preparation of scallop shell powder

[0053] Scallop shell powder was prepared in the laboratory by following these steps: E1: washing of scallop shells, E2: crushing of the washed scallop shells to obtain a mixture of shell sand, E3: grinding of the shell sand to obtain a scallop shell powder having a d50 of 17 pm and a D90 of 60 pm.

[0054] The main characteristics of the scallop shell powder obtained are listed in Table 1. [Tables 1] Dry matter 99.7% Calcium carbonate 97.2% Calcium 39.97% Arsenic < 0.97 ppm Cadmium 0.22 ppm Mercury < 0.097 ppm Lead < 2.4 ppm dso 17 pm d9o 60 pm

[0055] Example 2: Influence of the percentage of scallop shell powder in a binary mixture of hydraulic binder

[0056] 9 standardized mortars were prepared according to standard NF EN 196-1 (mortars standardized 4x4x16 cm) from a CEM II A-LL 42.5 R to form a binary mixture of this cement substituted by different rates of scallop shell powder obtained in example 1. The first mortar is the CEI counter-example, it is obtained directly with the CEM II A-LL 42.5 R, the 8 other mortars, E1 to E8 present the rate of substitution listed in Table 2. [Tables 2] IEC E1 E2 E3 E4 E5 E6 E7 E8 Substitution rate (% mass) 0 2 5 7 10 15 20 30 50 28-day compressive strength (MPa) (Figure 3) 45.3 42.6 41.7 40.4 40.9 40.0 35.5 34.1 19.6

[0057] Compressive strength decreases with increasing substitution rate compared to 100% of CEM IL II. It should be noted that up to 30% substitution, the formulated binder has a strength class of 32.5 MPa. The compressive strengths of the E8 mortar are sufficiently high for its use, particularly as a hydraulic road binder, with a substitution rate of 50% by weight.

[0058] Example 3: Influence of the percentage of scallop shell powder in a ternary mixture of hydraulic binder.

[0059] 7 standardized mortars were prepared according to standard NF EN 196-1 (mortars standardized 4x4x16 cm) on CEM II A-LL 42.5 R to form a ternary mixture of this cement substituted with different proportions of scallop shell powder and LHF. The first mortar is the counter-example CE2; it is obtained directly with CEM II A-LL 42.5 R. The other six mortars, E9 to E14, have the substitution proportions listed in Table 3. [Tables 3] CE2 E9 E10 Eli E12 E13 E14 Substitution rate in scallop powder (% mass) 0 15 20 25 35 40 45 Substitution rate in LHF (% mass) 0 15 20 25 35 40 45 Global substitution rate 0 30 40 50 70 80 90 Compression resistance at 28 days (MPa) (Figure 4) 47.0 43.4 38.2 36.4 30.6 25.4 21.3

[0060] Compressive strength decreases with increasing substitution rate relative to 100% of CEM II. It should be noted that up to 50% overall substitution, the formulated binder is of strength class 32.5. The compressive strengths of E12, E13, and E14 mortars are sufficiently high for their use, particularly as hydraulic road binders, with high overall substitution rates.

[0061] Example 4: Road base material treated with hydraulic binder according to the invention

[0062] Two road hydraulic binder compositions were prepared by mixing the different components. The characteristics of these two compositions are listed in Table 4 below and the mechanical strengths of these two binders, on standardized mortars prepared according to standard NF EN 196-1, are listed in [Fig. 5] [Fig. 5].

[0063] 100% recycled asphalt aggregates, without corrective sand, were treated with 3% by weight or 5% by weight of each of the compositions LHR 1 and LHR 2, resulting in a first road base material (MAC 13) comprising 97% by weight of 100% recycled asphalt aggregates and 3% by weight of LHR 1, a second road base material (MAC 15) comprising 95% by weight of 100% recycled asphalt aggregates and 5% by weight of LHR 1, a third road base material (MAC 23) comprising 97% by weight of 100% recycled asphalt aggregates and 3% by weight of LHR 2, and a fourth road base material (MAC 25) comprising 95% by weight of 100% recycled asphalt aggregates. % and 5% by weight of LHR 2.

[0064] Test specimens of these four materials were prepared respecting the Modified Optimum Proctor compaction references with 4% binder according to standard NF EN 13286-2 in order to be able to characterize them with the following standardized tests: - Unconfined compressive strength (Rc) at 3, 7 and 28 days according to standard NF EN 13286-41 on test specimens with a diameter of 10 cm and a height of 20 cm prepared by vibro-compression according to standard NF EN 13286-52. - Direct tensile strength (Rt) and modulus of elasticity (E) at 28, 60 and 360 days according to standards NF EN 13286-40 and NF EN 13286-43 on test specimens with a diameter of 16 cm and a height of 32 cm made by vibro-compression according to standard NF EN 13286-52.

[0065] The unconfined compressive strength results shown in [Fig. 6] [Fig. 6] demonstrate that the 1 MPa threshold is reached at 2 days for MAC 15, at approximately 3.5 days for MAC 25, at 5 days for MAC 23, and at 6 days for MAC 13, under laboratory conditions. This minimum strength limit corresponds to the minimum curing time to be observed before allowing construction site traffic on the applied layer, and a fortiori before the application of the top layer.

[0066] MAC 15 and MAC 25 road base materials, with the applied hydraulic binder dosage (5% by weight), belong to mechanical performance class T3 after 60 days of curing. The moduli of elasticity obtained are less than 10 GPa. They are intermediate between a bituminous mix and a cement-treated aggregate, making the treated material much less susceptible to transverse cracking and offering excellent long-term durability. MAC 13 and MAC 23 road base materials, with the applied hydraulic binder dosage, belong to mechanical performance class T2 after 360 days of curing. ([Fig.7] [Fig.7])

Claims

Demands

1. Hydraulic binder composition comprising shell powder of at least one bivalve mollusc and at least one other component selected from the group including slaked lime, quicklime, sulfate source materials, granulated and ground blast furnace slag, ground conversion steel slag, paper mill ash, fly ash, Portland cement and standardized composite cements, crushed pozzolans, crushed calcined shales, crushed calcined clays, limestone fillers, alone or in mixture, wherein said shell powder of at least one bivalve mollusc has a d50 between 15 pm and 50 pm and a D90 less than or equal to 100 pm.

2. Hydraulic binder composition according to claim 1, characterized in that said hydraulic binder is a cement or a road hydraulic binder.

3. Hydraulic binder composition according to any one of claims 1 or 2, characterized in that the bivalve mollusc is selected from the group comprising the scallop, the clam, the oyster and mixtures thereof, preferably said bivalve mollusc is the scallop, preferably said bivalve mollusc shell comprising at least 65% by weight of limestone, preferably at least 75% by weight of limestone and more preferably at least 95% by weight of limestone.

4. Hydraulic binder composition according to any one of claims 1 to 3, characterized in that the shell powder of at least one bivalve mollusc is present in an amount between 5% by weight and 50% by weight, preferably between 10% by weight and 40% by weight and more preferably between 25% by weight and 35% by weight.

5. Hydraulic binder composition according to any one of claims 1 to 4, characterized in that said shell powder of at least one bivalve mollusc has a d50 between 15 pm and 40 pm, preferably between 16 pm and 30 pm and preferably between 17 pm and 20 pm, and preferably a d90 less than or equal to 100 pm, more preferably less than 80 pm and even more preferably about 60 pm.

6. Hydraulic binder composition according to any one of claims 1 to 5 characterized in that it comprises up to 50% Portland cement, advantageously between 10% and 40% by weight, more advantageously between 25% and 35% by weight and / or up to 50% by weight of granulated and ground blast furnace slag, advantageously between 10% and 40% by weight, more advantageously between 25% and 35% by weight.

7. Hydraulic binder composition according to any one of the preceding claims, characterized in that it further comprises one or more of the secondary components as defined in standards NF P 15-108, NF EN 13282-1 and NF EN 13282-2, NF EN 197-1, NF EN 197-5 and NF EN 197-6.

8. Use of a shell powder of at least one bivalve mollusc, having a d50 between 15 pm and 50 pm and a D90 less than or equal to 100 pm for the manufacture of cement or road hydraulic binder.

9. Material, in particular construction materials, concretes, treated materials for road base, for soft mobility, treated soils for earthworks, comprising hydraulic binder composition according to any one of claims 1 to 7 and a mixture of aggregates and sand, natural and / or recycled, as well as natural or excavated soils.

10. Material according to claim 9, characterized in that it is a treated material for road base, characterized in that the aggregates and sand are made up of at least 80% by weight of recycled asphalt, advantageously of 100% by weight.

11. A method for manufacturing said material according to claim 9 comprising a cold mixing step (in a plant or in-situ), advantageously between 10°C and 40°C of said road hydraulic binder composition according to any one of claims 1 to 7 and natural and / or recycled aggregates and sand.

Images