METHOD FOR MANUFACTURING A CONCRETE FORMULATED ON THE BASIS OF ACTIVATED SLAG

Abstract

Method for manufacturing a concrete from activated slag, comprising at least the steps consisting of: a) arranging a premixture P of water and granulates, the temperature of the premixture P being at least equal to 10° C., b) arranging an activation system A comprising at least a co-binder, a chelating agent, an alkali metal carbonate and a carbonated material different from the alkali metal carbonate, c) incorporating the activation system A and a slag S by mixing them into the premixture P, the activation system A and slag S being introduced successively and/or simultaneously, d) continuing the mixing until a fresh concrete is obtained, and e) allowing the fresh concrete to cure.

Claims

1. A process for the manufacture of an activated slag concrete, comprising at least the stages consisting in: a) having available a premix P of water and of aggregates, the temperature of said premix P being at least equal to 10° C., b) having available an activation system A comprising at least one cobinder, a chelating agent, an alkali metal carbonate and a carbonate material distinct from the alkali metal carbonate, c) incorporating, under mixing, in said premix P, said activation system A and a slag S, said activation system A and said slag S being introduced successively and/or simultaneously, d) prolonging said mixing until a fresh concrete is obtained, and e) leaving said fresh concrete to harden.

2. The process as claimed in claim 1, in which said premix P is at a temperature at least equal to 15° C. in stage a).

3. The process as claimed in claim 1 or 2, in which said activation system A of stage b) is in the form of a premix P′ with said slag S, and said activation system A and said slag S are incorporated simultaneously in the premix P.

4. The process as claimed in any one of the preceding claims, additionally comprising the incorporation of at least one adjuvant chosen in particular from plasticizers, superplasticizers and their mixtures.

5. The process as claimed in any one of the preceding claims, employing said cobinder at a content of less than 5% by weight, with respect to the total weight of said activation system A and said slag S, also called weight of binder.

6. The process as claimed in any one of the preceding claims, in which said slag S comprises at least one ground granulated blast-furnace slag.

7. The process as claimed in any one of the preceding claims, in which said cobinder is a precursor of calcium ions.

8. The process as claimed in any one of the preceding claims, in which said activation system A comprises at least one alkali metal carbonate chosen from sodium carbonates, potassium carbonates and their mixtures, and more preferentially comprises at least sodium carbonate.

9. The process as claimed in any one of the preceding claims, in which said carbonate material distinct from the alkali metal carbonate is provided in the form of at least one material chosen from limestone, dolomite, precipitated calcium carbonate, chalk, marble, aragonite, travertine, tufa and their mixtures, and preferably comprises at least limestone.

10. The process as claimed in any one of the preceding claims, in which said chelating agent(s) is a chelating agent for the calcium ion or for the aluminum ion, and preferably for the calcium ion.

11. The process as claimed in any one of the preceding claims, in which said chelating agent is chosen from phosphonates, preferably monophosphonates and/or diphosphonates, and more preferentially from HEDP (1-hydroxyethylidene-1,1-diphosphonic acid) and EDTMP (ethylenediaminetetra(methylenephosphonic acid)).

12. The process as claimed in any one of the preceding claims, employing the alkali metal carbonate and the slag S in an alkali metal carbonate/slag S ratio by weight varying from 2% to 12%, preferably from 6% to 10%.

13. The process as claimed in any one of the preceding claims, employing the cobinder and the slag S in a cobinder/slag S ratio by weight varying from 1% to 5%.

14. The process as claimed in any one of the preceding claims, employing the chelating agent and the slag S in a ratio by weight of the chelating agent with respect to the slag S varying from 0.001% to 2%, preferably from 0.01% to 1% and more preferentially from 0.1% to 0.7%.

15. The process as claimed in any one of the preceding claims, employing water, the activation system A and the slag S in a water/(activation system A+slag S) ratio varying from 0.1 to 1, preferably from 0.2 to 0.55 and more preferentially from 0.3 to 0.5.

16. The process as claimed in any one of claims 4 to 15, employing, as adjuvant, at least one superplasticizer or plasticizer chosen from NBSP (naphthalene-based superplasticizers), PNS (polynaphthalene sulfonates), LS (lignosulfonates) and their mixtures, preferably chosen from PNS, LS and their mixtures.

17. The process as claimed in any one of the preceding claims, in which stages c) to d), indeed even a) to d), are carried out in a concrete mixing plant, preferably a concrete mixing plant with a forced-action mixer.

18. An activated slag concrete obtained by the process as claimed in any one of the preceding claims.

19. The concrete as claimed in the preceding claim, falling at least within the strength class C30/37, preferably falling within the strength class C30/37, according to the standard NF EN 206/CN.

20. The concrete as claimed in claim 18 or 19, falling within the consistency class S4 or S5, preferably within the consistency class S4, according to the standard NF EN 206/CN, for a period of time of at least 60 min, in particular of at least 90 min and more particularly of at least 120 min.

21. A fresh activated slag concrete, obtained on conclusion of stage d) of the process as claimed in any one of claims 1 to 17.

22. A reinforced activated slag concrete, comprising steel reinforcements and an activated slag concrete as claimed in any one of claims 18 to 20.

23. A structuring element comprising an activated slag concrete as claimed in any one of claims 18 to 20, the structuring element preferably being a pile, a diaphragm wall, a footing, a stringer, a slab, a floor, a post, a beam or a shell.

24. A precast element, comprising an activated slag concrete as claimed in any one of claims 18 to 20.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0167] FIG. 1 represents the Abrams cone slump results of an activated slag concrete obtained by the process of the invention according to example 1 (□ symbols) or 2 (Δ symbols) or obtained by a method outside the invention according to example 3 (⊚ symbols).

[0168] FIG. 2 represents the results of spreading with the Abrams minicone (expressed as percentage) of an activated slag mortar obtained by the process of the invention according to the form of introduction of example 2 with water and aggregates at 20° C. (⋄ symbols), water at 60° C. and aggregates at 5° C. (□ symbols) and water and aggregates at 5° C. (Δ symbols).

[0169] FIG. 3 represents the mean shrinkage measured on 3 test specimens of one and the same activated slag concrete obtained by the process according to the invention.

[0170] FIG. 4 represents the compressive strength of an activated slag concrete obtained by a process according to the invention with a water/binder ratio of 0.34 (Δ symbols), 0.36 (⋄ symbols) and 0.38 (□ symbols).

EXAMPLES

[0171] Materials and Methods

[0172] The following starting materials were used: [0173] Semi-crushed silico-calcareous aggregates with a density of 2530 kg/m.sup.3 and a water absorption of 1.3%; [0174] Slag originating from the Ecocem factory at Fos-sur-Mer, produced according to the European standard (NF EN 15167-1). The particle size distribution is characterized by D10=1.38 μm; D50=12.16 μm and D90=34.87 μm. The particle size distribution values are determined with a laser diffraction particle sizer from Malvern named “Mastersizer 3000”, according to the liquid dispersion method. The Blaine fineness is 4500 cm.sup.2/g; [0175] Cobinder: it is a clinker, the Blaine fineness of which is 3100 cm.sup.2/g and the main chemical components of which are as follows: CaO (67% by weight), SiO.sub.2 (21% by weight), Fe.sub.2O.sub.3 (5% by weight), SO.sub.3 (3% by weight); [0176] Anhydrous sodium carbonate (Na.sub.2CO.sub.3), 99% purity, sold by Solvay; [0177] Calcium carbonate, with a median diameter D50=1 μm and with a BET specific surface of 80 000 cm.sup.2/g; [0178] Chelating agent HEDP.Math.4Na; [0179] Superplasticizer of PNS type (solids content 32%).

[0180] The Abrams cone slump measurements are carried out on concrete (FIG. 1) according to the standard NF EN 12350-2 at a temperature of 20° C. and the Abrams minicone spreading measurements are carried out on mortar (FIG. 2) according to the provisions of the standard NF EN 12350-8 using the CEM minicone (Abrams cone at ½ scale) instead of the Abrams cone.

[0181] The shrinkage is measured on test specimens with dimensions of 7×7×28 cm.sup.3 stored at 20° C. and 50% relative humidity according to the standard NF P 15-433.

[0182] The compressive strength is measured for the concretes on test specimens with a diameter of 110 mm and a height of 200 mm according to the standard NF EN 12390-3. For the mortars, the compressive strength is measured on 4 cm×4 cm×16 cm prisms according to the standard NF EN 196-1.

Example 1

[0183] Preparation of a Concrete According to the Invention (Method 1)

[0184] An activation system is prepared by dry mixing sodium carbonate, calcium carbonate, chelating agent and cobinder in the proportions indicated in table 2 as percentage by weight.

[0185] The concrete is prepared by incorporation, under mixing, of the following constituents in the mixer, in the proportions described in detail in table 2, according to the following sequence: [0186] Aggregates; [0187] Water at a temperature making it possible to obtain an equilibrium temperature with the aggregates of between 15° C. and 25° C.; [0188] Mixing for 30 seconds; [0189] Activation system; [0190] Mixing for 30 seconds; [0191] Slag; [0192] Mixing for 30 seconds; [0193] Superplasticizer; [0194] Final mixing for 3 minutes.

TABLE-US-00002 TABLE 2 Composition A Competition B Composition C (according to the (outside the (according to the invention) invention invention Slag (kg/m.sup.3) 400 400 400 Activation (sodium carbonate (sodium carbonate (sodium carbonate system 51% + calcium 61.8% + calcium 51.5% + calcium (kg/m.sup.3) carbonate 25.5% + carbonate 37.5% + carbonate 25.8% + chelating agent chelating agent cobinder 20.6% + 3.1% + cobinder 0.7%): chelating agent 20.4%) 53.4 kg/m.sup.3 2.1%): 78.4 kg/m.sup.3 77.6 kg/m.sup.3 Aggregates 1642 1642 1642 (kg/m.sup.3) Effective water 177 172 172 (kg/m.sup.3) Superplasticizer 5 5.7 5 with a solids content of 32% (kg/m.sup.3)

Example 2

[0195] Preparation of a Concrete According to the Invention (Method 2)

[0196] The activation system is prepared as in example 1.

[0197] A premix of the activation system and of the slag is prepared by dry mixing.

[0198] The concrete is prepared by incorporation, under mixing, of the following constituents in the mixer, in the proportions described in detail in table 2, according to the following sequence: [0199] Aggregates; [0200] Water at a temperature making it possible to obtain an equilibrium temperature with the aggregates of between 15° C. and 25° C.; [0201] Mixing for 30 seconds; [0202] Premixing of the activation system and of the slag; [0203] Mixing for 30 seconds; [0204] Superplasticizer; [0205] Final mixing for 3 minutes.

Example 3

[0206] Preparation of a Concrete Outside the Invention (Method 3)

[0207] The activation system is prepared as in example 1.

[0208] A premix of the activation system and of the slag is prepared as in example 2.

[0209] The concrete is prepared by incorporation, under mixing, of the following constituents (which are at ambient temperature of the laboratory, i.e. 20° C.) in the mixer, in the proportions described in detail in table 2, according to the following sequence: [0210] Aggregates; [0211] Premixing of the activation system and of the slag; [0212] Dry mixing for 30 seconds; [0213] Water; [0214] Mixing for 30 seconds; [0215] Superplasticizer; [0216] Final mixing for 3 minutes.

Example 4

[0217] Abrams Cone Slump Test

[0218] Abrams cone slump tests are carried out for methods 1, 2 and 3, described in detail respectively in examples 1, 2 and 3, with composition A of table 2.

[0219] The results, represented in FIG. 1, show that methods 1 and 2 according to the invention make it possible to maintain a fluid concrete consistency, characterized by a slump of greater than 160 mm, for more than 2 hours. On the contrary, in the case of method 3 outside the invention, the concrete lost its fluid concrete consistency after 45 minutes.

[0220] Abrams minicone spreading tests are also carried out according to method 2, described in detail in example 2, with the concrete equivalent mortar proportions corresponding to composition A (see table 3 below) for a premix of aggregates and of water at different temperatures.

TABLE-US-00003 TABLE 3 Activation system (sodium carbonate 51% + calcium carbonate 25.5% + chelating agent 3.1% + cobinder Effective Constituent Slag 20.4%) Aggregates water Superplasticizer Proportion 1184 232 2597 338 15 (g)

[0221] The following three tests are carried out:

i) The water and the aggregates are conditioned at 20° C. before they are mixed, and the premix P obtained has a temperature of 20° C.;
ii) The aggregates are conditioned at 5° C. and are mixed with water at 60° C., forming a premix P having a temperature of 27° C.;
iii) The water and the aggregates are conditioned at 5° C. before they are mixed, and the premix P obtained has a temperature of 5° C.

[0222] FIG. 2 represents the results of the minicone spreading obtained. In the two cases where the premix of water and of aggregates obtained has a temperature of greater than 15° C. (case i) and ii) above), the consistency of the mortar is kept fluid for at least 1 hour. On the contrary, the use of materials which do not respect the recommendations of temperatures, as in the case of the premix of water and of aggregates at 5° C. (case iii) above), causes a rapid stiffening of the mortar and does not make it possible to obtain the maintenance of a fluid consistency.

Example 5

[0223] Results of the Shrinkage

[0224] The measurements of the shrinkage are carried out for three test specimens obtained with composition A.

[0225] The curve of FIG. 3 corresponds to the mean of the deformations measured on each of the three prisms of one and the same concrete. It shows that the shrinkage of a concrete according to the invention is comparable to the shrinkage of a conventional cement concrete.

Example 6

[0226] Robustness of Concrete Composition in Accordance and not in Accordance with the Invention

[0227] Strength measurements are carried out for concretes prepared with composition B (outside the invention) and composition C (according to the invention).

[0228] In addition, concretes, the composition of which comprises: [0229] an excess of water of 10 liters (composition B or C with 182 kg/m.sup.3 of water per 400 kg/m.sup.3 of slag), or [0230] a deficiency in water of 10 liters (composition B or C with 162 kg/m.sup.3 of water per 400 kg/m.sup.3 of slag),
are produced in order to evaluate the robustness of the composition.

[0231] The results for composition C according to the invention are given in FIG. 4. The impact of the amount of water in the mixture virtually does not modify the mechanical strength of the test specimens obtained. In addition, a compressive strength of greater than 40 MPa is measured at 28 days.

[0232] On the contrary, the results for composition B outside the invention, given in table 4, show that the concrete experiences an extreme slowdown in its hardening in the case of an excess of water. CS represents the compressive strength measured at different ages of the concrete.

TABLE-US-00004 TABLE 4 CS48h CS72h CS7d CS28d Batch (MPa) (MPa) (MPa) (MPa) Composition B 0.8 1.0 28.8 48.2 (20° C.) Composition B + 0 0 0 n.m. 10 liters (20° C.)