COMPOSITE MATERIALS COMPRISING CONCRETE AGGREGATES, AND POROUS CARBON AND USE THEREOF FOR ELIMINATING POLLUTANT GASES

Abstract

The invention belongs to the field of eliminating pollutant gases. In particular, the invention belongs to the field of pollutant gas-absorbing material such as CO2, SO2, NOx and VOCs.

The present invention relates to a fresh composite or composite paste and a composite material comprising aggregates of recycled concrete, porous carbon, a binder and optionally water, as well as to the method for manufacturing the composite and the use thereof for sanitizing air (indoor or outdoor). The invention also relates to an article (for example, an anti-noise wall, a tunnel lining, an indoor decoration, an item of street furniture, etc.) comprising the composite according to the invention.

Claims

1. A fresh composite comprising at least one concrete aggregate having a porosity greater than or equal to 12%, porous carbon having a micropore volume greater than or equal to 0.2 cm.sup.3/g and a macropore volume greater than or equal to 0.2 cm.sup.3/g, a binder and optionally water.

2. The fresh composite of claim 1, wherein the volume ratio of concrete aggregate/porous carbon is in the range of 30:70 to 80:20.

3. The fresh composite of claim 1, wherein the ratio of concrete aggregate outer surface/porous carbon outer surface is in the range of 0.5 to 1.5.

4. The fresh composite of claim 1, wherein the mass ratio of concrete aggregate/binder is in the range of 0.6 to 1.

5. The fresh composite of claim 1, wherein the porous carbon/binder weight ratio is in the range of 0.03 to 0.1.

6. The fresh composite of claim 1, wherein the porous carbon consists essentially of carbon and has a specific surface area ranging from 500 to 3000 m.sup.2/g.

7. The fresh composite of claim 1, wherein the porous carbon aggregate is functionalized.

8. The fresh composite of claim 1, wherein the porous carbon aggregate has an average diameter ranging from 1 to 20 mm.

9. The fresh composite of claim 1, wherein the concrete aggregate consists essentially of recycled concrete.

10. The fresh composite of claim 1, wherein the concrete aggregate has an average diameter ranging from 1 to 50 mm.

11. The fresh composite of claim 1, wherein the water/cement ratio has a value ranging from 0.3 to 0.6.

12. The fresh composite of claim 1, wherein the binder comprises at least one binder selected from CEM I, CEM II, CEM III, CEM IV or CEM V cements, polymeric type binders, resins or carbon-based binders, or mixtures thereof.

13. The fresh composite of claim 1, further comprising at least one adjuvant and/or additive.

14. A composite comprising at least one concrete aggregate having a porosity greater than or equal to 12%, porous carbon having a micropore volume greater than or equal to 0.2 cm.sup.3/g and a macropore volume greater than or equal to 0.2 cm.sup.3/g, a binder and optionally water.

15. A method for sanitizing air comprising placing the fresh composite of claim 1 into an indoor or outdoor environment.

16. A method for manufacturing the composite of claim 14, comprising the steps of: a) mixing at least one concrete aggregate having a porosity greater than or equal to 12%, porous carbon having a micropore volume greater than or equal to 0.2 cm.sup.3/g and a macropore volume greater than or equal to 0.2 cm.sup.3/g, a binder, optionally water and optionally additives, adjuvants and/or aggregates, and obtaining a fresh composite; b) molding and curing the fresh composite obtained in step a); and c) demolding.

17. The fresh composite of claim 7, wherein the porous carbon aggregate is functionalized on the surface with at least one heteroatom selected from O, N, S or P.

18. The fresh composite of claim 8, wherein the porous carbon aggregate has an average diameter ranging from 5 to 10 mm.

19. The fresh composite of claim 10, wherein the concrete aggregate has an average diameter ranging from 5 to 10 mm.

20. The method of claim 15, wherein the fresh composite absorbs CO.sub.2, SO.sub.2, NOx and/or VOCs.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0123] FIG. 1 represents a schematic of the composite manufacturing method according to the invention.

[0124] FIG. 2 shows the CO.sub.2 capture capacity for composites 1 and 2. (a) CO.sub.2 capture capacity as a function of composite material mass; (b) CO.sub.2 capture capacity as a function of material volume; (c) CO.sub.2 capture capacity as a function of gas accessible surface area.

[0125] FIG. 3 shows the diffusion of CO.sub.2 into the cementitious material matrix in composite 2 (a) and composite 1 (b) after 20 days in a 10,000 ppm CO.sub.2 atmosphere. The darker gray areas correspond to the non-carbonated cementitious material.

[0126] The invention is further illustrated by the following non-limiting examples.

[0127] Example 1: Synthesis of a composite according to the invention.

[0128] The composite material consists of aggregates of recycled concrete and porous carbon embedded in a cement matrix. The preparation method of the composites is like the classical method of concrete preparation (see FIG. 1). The different steps of the synthesis are: [0129] 1) Prepare the porous carbon by pyrolysis of brown algae (Lessonia nigrescens) in an oven at 750° C. and an atmosphere of 100 ml/min of inert gas (N.sub.2), [0130] 2) Mix the aggregates of recycled concrete and the porous carbon with a volume ratio of recycled concrete : porous carbon of 60:40. For this purpose 319 g of aggregate of recycled concrete (13% porosity) with an average diameter of about 6 mm are mixed with 11.9 g of porous carbon particles with an average diameter of about 6 mm and a micropore volume of 0,4cm.sup.3/g and a macropore volume of 4,8cm.sup.3/g (specific surface area 746 m.sup.2/g). [0131] 3) Prepare the binder by making a cement paste with cement and water. The quantity of cement corresponds to a mass ratio aggregate/cement of about 0.8. The quantity of water corresponds to a W/C ratio of 0.45. For this purpose, 400 g of CEM I cement are mixed manually with 180 g of water. [0132] 4) Mix the aggregates with the binder by hand until the aggregates are homogeneously distributed in the “cement” paste.
The result is fresh composite 1, [0133] To prepare the composite, we continue with the steps: [0134] 4) Pour the fresh composite into a mold with dimensions 9*3*2 cm and let it harden for 24 hours in a chamber with a relative humidity of about 100%. [0135] 5) Demold and proceed to a hydration stage of 27 days in a climatic chamber with a relative humidity of about 100%.
FIG. 1 in the appendix of a cross section of the composite materials shows that the distribution of aggregates in the cement matrix is homogeneous, although they are small pieces (3×3×2 cm) made at laboratory scale with manual mixing.

[0136] Example 2: Synthesis of a composite outside the invention.

[0137] The composite material consists of aggregates of recycled concrete embedded in a cement matrix. The preparation method of the composites is like the classical method of concrete preparation (see FIG. 1). The different steps of the synthesis are: [0138] 1) Prepare 474 g of aggregates of recycled concrete (13% porosity) with an average diameter of about 6 mm. [0139] 2) Prepare the binder by making a cement paste with cement and water. The quantity of cement corresponds to a mass ratio of aggregates/cement of about 1.2. The quantity of water corresponds to a W/C ratio of 0.45. For this purpose, 400 g of CEM I cement are mixed manually with 180 g of water. [0140] 3) Mix the aggregates with the binder manually until the aggregates are homogeneously distributed in the “cement” paste.
The fresh composite 2 is obtained (out of the invention). [0141] To prepare the composite the following steps are added: [0142] 4) Pour the fresh composite into a mold with dimensions 9*3*2 cm and let it harden for 24 hours in a chamber with a relative humidity of about 100%, [0143] 5) Demold and proceed to a hydration stage of 27 days in a climatic chamber with a relative humidity of about 100%.

TABLE-US-00001 TABLE 1 Summary of characteristics of composites 1 and 2. Example 1 (composite 1 according Example 2 (composite 2 out of to the invention) invention) 319 g of recycled concrete (247 474 g of recycled concrete (370 mL) mL) 11.8 g of porous carbon LN750 n/a (124 mL) 400 g of CEM I cement (385 mL) 400 g of CEM I cement (385 mL) 180 g water (W/C ratio = 0.45) 180 g water (W/C ratio = 0.45)

[0144] Example 3: Measurement of the depolluting capacities of composites 1 and 2.

[0145] The depolluting capacities of the materials were determined on a laboratory scale with CO.sub.2 capture experiments under so-called “accelerated” conditions.

[0146] For this purpose, the composite materials were placed in a CO.sub.2 incubator conditioned in a relative humidity of about 63%, an ambient temperature of about 25° C. and a CO.sub.2 concentration with an order of magnitude higher than what can be found in highly polluted urban areas. The concentration of CO.sub.2 in the air of a large city like Paris is about 400-450 ppm while it can reach more than 1000 ppm at the exit of a tunnel on a road. The concentration chosen for the “accelerated” CO.sub.2 capture experiments was 10,000 ppm, which is 10 times more concentrated than at the exit of a tunnel for example.

[0147] FIG. 2 shows the amount of CO.sub.2 captured for both composites 1 and 2 (prepared in Examples 1 and 2), as a function of the number of days in the chamber (carbonation days). In this example, the composite material according to the invention contains 60% by volume of aggregates of recycled concrete (with an average diameter of about 6 mm) and 40% by volume of porous carbon particles (with an average diameter of about 6 mm, obtained from biomass and with a specific surface area of 1300 m.sup.2/g) in a cement matrix (cement type CEM1).

[0148] To show the synergistic effect of composite 1, it is compared with composite 2 (not comprising porous carbon). The results presented in FIG. 2 show that composite 1 has a significantly higher CO.sub.2 adsorption capacity than composite 2.

[0149] In particular, after 30 days of exposure to CO.sub.2, the composite 1 presents: [0150] an adsorption capacity (for an equivalent mass of material) greater than 20% (FIG. 2a), [0151] an adsorption capacity (for an equivalent volume of material) greater than 30% (FIG. 2b), and [0152] an adsorption capacity (for an equivalent surface of material exposed to the pollutant gas) greater than 30% (FIG. 2c).

[0153] Thus, a synergistic effect on the absorption of pollutant gases is observed between the composite 1 according to the invention and the composite 2 out of the invention. Surprisingly, the CO.sub.2 adsorption capacity of composite 1 is not only significantly higher (by mass, by volume and by exposed surface) but also faster than that of composite 2.

[0154] In FIG. 3 (composite 2, FIG. 3a and composite 1, FIG. 3b) after 20 days under an atmosphere of 10,000 ppm CO.sub.2, carbonation of the cementitious material (uncolored areas) around the carbon particles is observed for composite 1. This indicates that in the case of composite 1, the CO.sub.2 gas which is not adsorbed in the carbon porosity diffuses around the particle and reaches the whole matrix more quickly than in the case of composite 2.