NOVEL HYDRAULIC BINDER AND HYDRAULIC COMPOSITION COMPRISING SAME

Abstract

A hydraulic binder which includes a clinker with a specific shape, the clinker including as main phases, given as weight percentages relative to the total weight of the clinker: (i) 70 to 95% of a belite phase having a particle size such that the Dv50 ranges from 5 to 15 μm; (ii) 5 to 30% of a calcium aluminoferrite phase; and (iii) less than 5% of minor phases; the clinker having an Al.sub.2O.sub.3/Fe.sub.2O.sub.3 weight ratio of less than 1.5; and the clinker including less than 5% of alite phase and less than 5% of calcium sulphoaluminate phase; and at least 0.5% dry weight of an activator made of calcium sulphate, as a weight percentage relative to the total weight of phases (i) to (iii).

Claims

1. A hydraulic binder which comprises a particulate-shaped clinker, the clinker comprising as main phases, in % expressed in mass relative to the total mass of the clinker: (i) from 70 to 95% of a belite phase having a particle size such that Dv50 ranges from 5 to 15 μm; (ii) from 5 to 30% of a calcium alumino-ferrite phase; and (iii) less than 5% of minor phases; the clinker having an Al.sub.2O.sub.3/Fe.sub.2O.sub.3 mass ratio lower than 1.5; and the clinker comprising less than 5% of alite phase and less than 5% of calcium sulpho-aluminate phase and at least 0.5% dry mass of a calcium sulphate-based activator, in mass percent relative to the total mass of the phases (i) to (iii).

2. The hydraulic binder according to claim 1, comprising a setting accelerator.

3. The hydraulic binder according to claim 1, wherein the clinker comprises less than 5% of water-soluble alkaline salts.

4. The hydraulic binder according to claim 1, wherein the clinker is prepared by a process which comprises: decarbonating a raw mix having a particle size such that the maximum diameter is lower than 100 μm; clinkering the decarbonated raw mix for 5 to 30 minutes at a temperature ranging from 1 150 to 1 400° C. of calcium, silicon, alumina, magnesium, iron sources and capable, by clinkering, of providing the belite phase and the calcium alumino-ferrite phase, to obtain the clinker comprising as main phases in, in % expressed in mass relative to the total mass of the clinker: (i) from 70 to 95% of said belite phase; (ii) from 5 to 30% of said calcium alumino-ferrite phase; and (iii) less than 5% of minor phases; the clinker having an Al.sub.2O.sub.3/Fe.sub.2O.sub.3 mass ratio lower than 1.5; and the clinker comprising less than 5% of alite phase and less than 5% of calcium sulpho-aluminate phase; and cooling by quenching the clinker obtained.

5. The hydraulic binder according to claim 1, comprising a Portland clinker.

6. A process for preparing a hydraulic binder according to claim 1, which comprises a step of grinding the clinker and a step of adding calcium sulphate.

7. A hydraulic composition which comprises a hydraulic binder according to claim 1 and water.

8. A process for preparing a hydraulic composition according to claim 7, comprising a step of mixing water and the hydraulic binder.

9. A shaped object for the construction field comprising a hydraulic composition according to claim 7.

Description

EXAMPLES

Raw Materials

[0127] The raw materials used for making the different raw mixes, hydraulic binders and hydraulic compositions are described in Table 1 hereinafter.

TABLE-US-00001 TABLE 1 Finess SiO.sub.2 Al.sub.2O.sub.3 Fe.sub.2O.sub.3 CaO MgO K.sub.2O Na.sub.2O SO.sub.3 LOI* Dv50 Product [%] [%] [%] [%] [%] [%] [%] [%] [%] (μm) Limestone 0.05 0.07 0.00 55.9 0.2 0.00 0.00 0.0 43.2 2.2 Metakaolin 55.2 40.9 0.9 0.3 0.3 0.96 0.0 0.0 0.8 7.7 Alumina 7.5 79.1 1.9 3.5 0.0 0.0 0.0 0.0 3.0 (Prolabo) Silica 98.7 0.2 0.0 0.0 0.0 0.0 0.07 0.0 0.2 3.0 Iron Oxide 0.2 0.1 96.4 0.0 0.06 0.0 0.0 0.2 3.0 Ca-Sulphate 0.4 0.0 0.0 41.1 0.2 0.0 0.11 55.7 2.5 (anhydrite MCC 224 - Poland) MgCO.sub.3 0.0 0.0 0.0 0.0 47.8 0.0 0.0 0.0 52.2 (magnesia; Sigma Aldrich) K.sub.2CO.sub.3 0.0 0.0 0.0 0.0 0.0 68.2 0.0 0.0 31.8 Na.sub.2CO.sub.3 0.0 0.0 0.0 0.0 0.0 0.0 58.5 0.0 41.5 Silica 98.5 0.83 0.07 0.04 0.0 0.0 0.0 0.0 0.0 3.0 (Sibelco - C600) Calcium 0.0 0.06 0.02 55.8 0.0 0.0 0.0 0.0 43.5 2.2 carbonate (Omya - Durcal1) Iron ore 2.0 0.0 96.0 0.0 0.0 0.0 0.0 0.0 1.2 (Prolabo) Gypsum 0.7 0.0 0.0 32.7 0.0 0.0 0.0 44.5 21.7 (Meriol) CEM I from 20.1 4.9 2.8 63.9 1.4 0.8 0.1 3.2 2.0 Port La Nouvelle *LOI: Loss on ignition

[0128] In table 1 hereinabove, the total is not always 100% in particular because of minor elements which are non taken into account.

[0129] The grinding agent used was TEA (triethanolamine C.sub.6H.sub.15NO.sub.3) having a 95% purity, the provider of which is VWR.

Preparation of the CSHs

[0130] The accelerator suspension (CSH) was prepared from CEM I cement from Port La Nouvelle suspended in demineralised water. The water/cement ratio was set to 7.5. To this suspension, a PCP type superplasticiser was added at 10% by wet mass (of solution) relative to the cement mass. The superplasticiser used was Glenium ACE 456 (Provider: BASF), which is in the solution form. To this suspension, a viscosifier was been added at 1% by dry mass (of powder) relative to the superplasticiser mass. The viscosifier used was Aquabeton (Provider: Chryso), which is in the powder form. Both adjuvants were added at the start of the synthesis. The suspension was stirred at 450 rpm for 2 days in a glass reactor at a temperature of 20° C. The composition of the formulation used is set out in table 2 hereinafter.

TABLE-US-00002 TABLE 2 Formulation of the accelerator suspension Port la Nouvelle Glenium ACE Aquabeton Composition CEM I 52.5 R 456 (BASF) (Chryso) water mass 200 g 20 g of 0.2 g of 1.5 L solution powder

[0131] After the synthesis, the accelerator suspension was preserved in a polypropylene sealed container. The accelerator suspension required a minimum maturation time (rest time after stirring) to reach the maximum performance. This maturation time was between 7 and 14 days.

[0132] The accelerator suspension thus obtained had a BET specific surface area of about 50 to 80 m.sup.2/g after drying at 60° C. until it had a constant mass.

Production of Two-Phase Belite Clinker

Preparation of the Raw Mix

[0133] A jar rotating machine generally enables a powder mixture to be homogenised in a wet medium, using alumina beads. For an optimum mixing, the powders to be homogenised should generally have a particle size lower than 200 μm.

[0134] The raw materials were mixed in the amounts set out in table 3 hereinafter.

TABLE-US-00003 TABLE 3 Weighings for 5 Kg of material with the raw materials Iron Mass (Kg) Limestone Silica Magnesia Alumina ore Anhydrite BI3 3.541 0.888 0.020 0.065 0.304 0.182

[0135] The addition of water was carried out with demineralised water. The mixing of powders and demineralised water (1:1 mass mixture) was carried out beforehand in the jar.

[0136] In the jar, alumina beads with three different diameters (17, 25 and 35 mm) were added. The total volume of the beads account for 50 to 60% of the internal volume of the jar.

[0137] The beads with different sizes were distributed according to the following proportions (mass %): 25% small ones (17 mm), 50% medium ones (25 mm) and 25% large ones (35 mm). Then, after properly closing the jar by making sure of the presence of a seal, the jar was installed on rolls.

[0138] The jar rotation time was about 2h30 for 2 kg of material and 2 kg of water. The rotation speed of the jar was 50 to 80% of the critical speed, that is the speed at which the beads are satellised because of the centrifugal force. At the end of homogenisation, the beads were recovered using a sieve and the mixture were poured in an appropriate container.

[0139] The mixture was then dried in an oven at 105° C. for at least one night. This step generally does not last more than 24 hours. The end of drying is generally determined by a visual monitoring. This step is generally not made in a factory, because the process is continuous and the decarbonating step is made immediately after. This step is generally useful in a laboratory because some species are water soluble and will be lost without the intermediate drying.

Production of Granulates

[0140] The granulates were produced thanks to a pan granulator.

[0141] After turning ON the granulator and putting the scraper half-way up to avoid that the powder turns around the granulator, the powder was intermittently sprayed to form granulates. The water addition frequency was set according to a practice known to those skilled in the art, depending on the formation quality of the granulates, with a visual monitoring. The amount of added water is generally such that the humidity of the granulates is between 10 and 20%, for example 15%.

[0142] For the purpose of forming small granulates, according to a practice known to those skilled in the art, the scraper was placed on top of the granulator (above half-height up). When the granulates were formed, the granulator continued to rotate for about 10 minutes to obtain solid granulates, in the absence of addition of water. Then, the granulator was stopped and the granulates were sieved in order to keep only granulates with a diameter higher than 3 mm and lower than 10 mm.

[0143] The granulates thus obtained were placed in a ventilated oven at 110° C. for drying up to a constant mass.

Baking

[0144] The raw materials prepared as granulates (called a raw mix) were introduced in platinum crucibles in a static furnace.

[0145] The temperature profile (temperatures and residence time) enabled the raw mix to be baked in 2 successive phases: a decarbonating phase and a higher temperature clinkering phase.

[0146] In a known manner, the limestone decarbonation phase was performed with a temperature rise of 1 000° C./h until 975° C., followed by a holding period of one hour at this temperature (975° C.).

[0147] The clinkering phase was performed with a temperature rise of 300° C./h up to 1 330° C., which temperature was preserved for 15 minutes.

[0148] In order to fix the mineralogical phases of the clinker, the sample has undergone a quenching at room temperature on a metal plate at the end of the clinkering.

[0149] After clinkering, X-ray diffraction Rietveld analyses have shown that the mineralogical composition of the clinker obtained is close to the 80% C2S and 20% C4AF target. The results are reported in table 4 hereinafter.

TABLE-US-00004 TABLE 4 Mineralogical composition C2S C4AF Anhydrite BI3 82.0% 16.6% 1.4%
Production of a Binder According to the Present Invention Test with and without Gypsum

[0150] The effect of the sulphate content of the cement on the hydration rate and the acquisition speed of the mechanical strengths was tested on a composition comprising the clinker BI3 and having a ratio W/B of 0.4.

[0151] The clinker BI3 was ground at a 5 256 cm.sup.2/g Blaine specific surface area.

[0152] The hydration start time was calculated from the microcalorimetry curve, as described hereinafter.

[0153] The isothermal microcalorimetry is one of the basic methods used for following the hydration.

[0154] The Tam Air calorimeter is mainly used to measure heat fluxes due to the fact that chemical reactions immediately follow each other during the hydration process.

[0155] The measurements were carried out at 20° C.

[0156] The preparation of the sample was made by external hand mixing, of a quantity of about 30 g of clinker.

[0157] A mass of 5 to 10 g was introduced in the calorimetry cell.

[0158] The measurement of the thermal flux was followed for 14 days.

[0159] Two events were noticed: [0160] a first set of exothermal peaks starting within the first 24 hours; [0161] a second exothermal peak triggering later and spreading over several days, associated with the CSH formation and belite dissolution.

[0162] The appearance time of the second peak is associated, for the belite cements according to the present invention, with the belite hydration start and the CSH and Portlandite formation.

[0163] Several formulae were tested: a control without sulphate, only comprising the clinker and water, and three formulations according to the present invention comprising clinker, water and respectively 3, 5 and 8 mass % of gypsum relative to the mass of clinker. The gypsum was a sulphate source.

[0164] The results of the microcalorimetry measurements show that, relative to the control without sulphate, an addition of sulphate (gypsum) causes a time offset of the C2S hydration peak. Indeed, the addition of sulphate causes a C2S hydration start at about 7 days (instead of about 16 days in the absence of added sulphate).

[0165] Measurements of the mechanical strengths, made according to the standard EN 196-1 15 days after mixing confirmed these observations. Indeed, the compression mechanical strengths obtained 15 days after mixing the control non-gypsed clinker were about 4 MPa, whereas for the hydraulic compositions according to the present invention comprising from 3 to 8 mass % gypsum, the compression mechanical strengths obtained were in the order of 50 MPa at the same end.

Amount of Gypsum with Bounds

[0166] Five different gypsum addition contents were tested: 0.5; 1.5; 3; 5 and 8 mass % of gypsum relative to the clinker mass, on a composition comprising the ground BI3 clinker at a Blaine specific surface area of 5 200 cm.sup.2/g and having a W/B ratio of 0.4.

[0167] Microcalorimetry measurements were performed according to the protocol described hereinabove, in order to compare the C2S hydration start times.

[0168] As soon as 0.5% of gypsum was added, a decrease in the C2S hydration start time was noticed (16 days for the control without added gypsum and 12 days for the composition comprising 0.5% of gypsum). The decreasing C2S hydration start time was observed up to a gypsum addition of 1.5%. From this percentage, a 6.5 days holding period was noticed up to a gypsum content of 8%.

Effect of Temperature

[0169] In order to determine the effect of temperature on C2S hydration, compression strengths were measured on the same composition at 40° C. and at 80° C. The tested composition comprised clinker BI3, 5 mass % gypsum relative to the clinker and had a W/B ratio of 0.4.

[0170] The mechanical strengths were measured according to the protocol described hereinafter.

[0171] A mass of 30 g of clinker was mixed, and then introduced into cylinders of 11.5 mm diameter and 50 mm height using a syringe paying attention not to trap air bubbles.

[0172] These cylinders were dipped in water at 40 or 80° C. Once set, they were demoulded and then preserved by dipping in water at 40 or 80° C. After sawing the sample at its ends to obtain two parallel faces, a press was used to measure the compression strength.

[0173] Table 5 hereinafter gives the results obtained.

TABLE-US-00005 TABLE 5 W/B = 0.4 - W/B = 0.4 - (Mpa) 40° C. 80° C. 1 d 2 37 6 d 46 49 13 d  50 50

[0174] A beneficial effect of an increase in temperature was noticed on the mechanical strengths 1 day after mixing.

Effect of a CSH or CaCl.SUB.2 .Based Accelerator

[0175] From a hydraulic binder comprising clinker BI3, 5 mass % of gypsum relative to the clinker and having a ratio W/B of 0.4, different mineral accelerators were tested: 1% dry mass (of powder) of CaCl.sub.2 and 3% liquid mass of CSH.

[0176] The CSH based accelerator, which was that previously manufactured, was in the form of a solution and was added to the mixing water. The CSH solution had a solid content of 15.5%. About 0.5% of dry content was thus added relative to the gypsed clinker.

[0177] The CaCl.sub.2 based accelerator was in the form of a powder (Provider: VWR).

[0178] Microcalorimetry measurements enabled the C2S hydration start times to be compared. The C2S hydration start was in the order of 6.5 days without CSH and without CaCl.sub.2, 5 days with CaCl.sub.2 and 2.5 days with 0.5% of CSH.

[0179] The positive impact of the presence of mineral accelerators was thus demonstrated.

Effect of TEA and Calcium Carbonate

[0180]

TABLE-US-00006 TABLE 6 Proportions of the raw mix Raw materials Mass % Limestone 71.1 Metakaolin 6.0 Silica 14.2 Iron oxide 3.8 Calcium sulphate 3.7 MgCO.sub.3 0.5 Na.sub.2CO.sub.3 0.2 K.sub.2CO.sub.3 0.5

[0181] The raw mix, the composition of which is summarised in table 6 hereinabove, was prepared by wet homogenising using a jar rotating machine for 2 hours.

[0182] The homogeneous raw mix was then distributed in plates and it was put in the oven overnight at 110° C. to evaporate water.

[0183] Granulates were then formed from this raw mix using a pan granulator and water.

[0184] These granulates were dried for 12 hours in an oven at 110° C.

Baking the Clinker

[0185] Bakings were made in a laboratory muffle furnace. The granulates were placed in platinum crucibles and treated according to the following protocol: [0186] introducing 6 crucibles into the furnace, without lid; [0187] temperature rise No 1: 1 000° C./h up to 975° C.; [0188] isothermal holding period at 975° C. for 1 h; [0189] placing the lids on the crucibles; [0190] temperature rise No 2: 500° C./h up to the temperature of 1 350° C.; [0191] isothermal holding period at 1 350° C. for 10 minutes; [0192] emptying the crucibles and room temperature quenching in steel tanks.

[0193] The mineralogy of the clinker obtained was analysed by X-ray diffraction and the result is reproduced in table 7 hereinafter.

TABLE-US-00007 TABLE 7 Mineralogical composition of the clinker (mass %) Alite Belite Ferrite Alumina Ca C3S C2S C4AF C3A Langbeinite 0 85 14 0 1

Preparation of the Binder

[0194] The clinker was ground with a ball grinder of 5 kg (loaded at 2 kg) up to a Blaine specific surface area of 4 000 cm.sup.2/g, and then separated into two parts to produce two cements. Cement A was sulphated with 5 mass % of gypsum and ground at 5 230 cm.sup.2/g of Blaine specific surface area, and cement B was sulphated with 3 mass % of gypsum, added with 5 mass % of fine calcium carbonate and ground at 5 793 cm.sup.2/g of Blaine specific surface area.

Strength Tests According to Standard EN 196-1

[0195] Mortars under normalised conditions were prepared with cements A and B in order to determine compression strengths. In addition, mortars were made by adding TEA as an adjuvant in the mixing water (and not as a grounding agent), in order to determine its influence on the final strengths. The results of the compression mechanical strength tests according to standard EN 196-1 are shown in table 8 hereinafter:

TABLE-US-00008 TABLE 8 Compression strengths in normalised mortar EN Compression Compression Compression strength strength strength Cement 2 days [MPa] 7 days [MPa] 28 days [MPa] A 6.9 31.7 62.2 A + 0.03% TEA 6.8 32.4 69.0 B 5.9 28.5 67.9 B + 0.03% TEA 7.3 33.9 73.9

[0196] The results of table 8 hereinabove show the improvement in the mechanical strengths achieved by virtue of the addition of TEA in the mortar as an adjuvant, by comparing rows A to each other and rows B to each other respectively.

[0197] Additionally, the beneficial effect of calcium carbonate on the mechanical strengths is also demonstrated in the presence of TEA, or even in the absence of TEA at 28 days.