ADMIXTURE FOR FLUIDIFYING A CEMENTITIOUS COMPOSITION WITH REDUCED CEMENT CONTENT

Abstract

The application describes an admixture comprising a polymer as fluidifier of a cement composition comprising: from 20 to 64 wt. % clinker, from 5 to 60 wt. % activated clay, from 0 to 35 wt. % limestone, from 0 to 10 wt. % calcium sulfate,

the proportions being relative to the dry weight of the cement composition.

Claims

1. An admixed cement composition comprising: a cement composition comprising: from 20 to 64 weight % clinker, from 5 to 60 weight % activated clay, from 0 to 35 weight % limestone, from 0 to 10 weight % calcium sulfate, the proportions of clinker, activated clay, limestone and calcium sulfate being relative to the dry weight of the cement composition and an admixture comprising a polymer comprising units of following formulas (I) and (II): ##STR00007## where: R.sup.1 and R.sup.2 are each independently a hydrogen or a methyl, R.sup.3 is a hydrogen or a group of formula COO(M).sub.1/m R.sup.4 is a group of formula (CH.sub.2).sub.p(OAlk).sub.qR.sup.5 where: p is 1 or 2, q is an integer of 3 to 300, the Alk in each OAlk unit of the group (OAlk).sub.q is independently a linear or branched alkylene having 2 to 4 carbon atoms, R.sup.5 is OH or a linear or branched alkoxyl having 1 to 4 carbon atoms, R.sup.11 and R.sup.12 are each independently a hydrogen or a methyl, R.sup.13 is a hydrogen or a group of formula COO(M).sub.1/m, M is H or a cation of valence m, when M is H, m is 1 and when M is a cation, m is the valence of the cation M, a is a number from 0.05 to 0.25, such that (100a) represents the molar percentage of units of formula (I) within the polymer, and b is a number from 0.75 to 0.95, such that (100b) represents the molar percentage of units of formula (II) within the polymer, the proportion of polymer in the admixture being from 0.001 weight % to 5 weight % relative to the dry weight of the cement composition.

2. The admixed cement composition according to claim 1, wherein the polymer of the admixture comprises units of following formulas (I) and (II): ##STR00008## where: R.sup.2 is independently a hydrogen or a methyl, R.sup.4 is a group of formula CH.sub.2(OCH.sub.2CH.sub.2).sub.qR.sup.5 where: q is an integer of 3 to 500, R.sup.5 is OH or OMe, a is a number from 0.05 to 0.25, such that (100a) represents the molar percentage of units of formula (I) within the polymer, R.sup.12 is a hydrogen or a methyl, M is H or a cation of valence m, when M is H, m is 1 and when M is a cation, m is the valence of the cation M, b is a number from 0.75 to 0.95, such that (100b) represents the molar percentage of units of formula (II) within the polymer.

3. The admixed cement composition according to claim 2 wherein, in formulas (I) and (II) of the polymer of the admixture: q is an integer of 5 to 200, R.sup.5 is OH or OMe, a is a number from 0.05 to 0.20, b is a number from 0.80 to 0.95, and/or M is H or a monovalent or bivalent cation, m then being 1 or 2.

4. The admixed cement composition according to claim 1, wherein the admixture comprises a set retarding agent.

5. The admixed cement composition according to claim 4, wherein the set retarding agent is gluconic acid in neutral form or a salt thereof, a phosphonic acid in neutral form or a salt thereof, or a mixture thereof.

6. The admixed cement composition according to claim 1, comprising less than 0.001 weight % of tertiary alkanolamine having 1 to 6 carbon atoms relative to the dry weight of the admixed cement composition.

7. A hydraulic composition comprising the admixed cement composition according to claim 1, water, an aggregate and optionally a mineral addition.

8. A method for improving the fluidity retention over time of a cement composition, comprising the contacting of a cement composition comprising: from 20 to 64 weight % clinker, from 5 to 60 weight % activated clay, from 0 to 35 weight % limestone, from 0 to 10 weight % calcium sulfate, the proportions being relative to the dry weight of the cement composition, with an admixture comprising a polymer comprising units of following formulas (I) and (II): ##STR00009## where: R.sup.1 and R.sup.2 are each independently a hydrogen or a methyl, R.sup.3 is a hydrogen or a group of formula COO(M).sub.1/m R.sup.4 is a group of formula (CH.sub.2).sub.p(OAlk).sub.qR.sup.5 where: p is 1 or 2, q is an integer of 3 to 300, the Alk in each OAlk unit of the group (OAlk).sub.q is independently a linear or branched alkylene having 2 to 4 carbon atoms, R.sup.5 is OH or a linear or branched alkoxyl having 1 to 4 carbon atoms, R.sup.11 and R.sup.12 are each independently a hydrogen or a methyl, R.sup.13 is a hydrogen or a group of formula COO(M).sub.1/m, M is H or a cation of valence m, when M is H, m is 1 and when M is a cation, m is the valence of the cation M, a is a number from 0.05 to 0.25, such that (100a) represents the molar percentage of units of formula (I) within the polymer, and b is a number from 0.75 to 0.95, such that (100b) represents the molar percentage of units of formula (II) within the polymer.

9. The use method according to claim 8, wherein the admixture proportion is used so that the proportion of polymer is from 0.001 weight % to 5 weight % relative to the dry weight of the cement composition.

10. The method according to claim 8, wherein the cement composition comprises less than 0.001 weight % of tertiary alkanolamine having 1 to 6 carbon atoms relative to the dry weight of the cement composition.

Description

[0163] The invention is illustrated in the following Examples and FIGURE.

[0164] FIG. 1 illustrates the hydrating kinetics of a cement composition (heat flow in mW/g of cement composition as a function of time in hours): [0165] of a cement composition without admixture (reference) (solid line), [0166] of an admixed cement composition, the admixture comprising the polymer 5 at a dosage of 0.15 weight % relative to the dry weight of the cement composition (the admixed cement composition being free of set retarding agent) (dotted line), or [0167] of an admixed cement composition, the admixture comprising the polymer 5 at 0.1 weight % and sodium gluconate at 0.08 weight % relative to the dry weight of the cement composition (chain-dotted line) (Example 3).

EXAMPLE 1

[0168] Impact of the type of polymer and of the presence of a set retarding agent on the fluidification of a cement composition.

[0169] The polymers described below were tested on a mixture of cement composition and water (cement slurry). Rheological testing was carried out with a hydration time of 2 hours.

[0170] The cement composition used was composed of about 50% clinker and about 50% of a mixture of metakaolin, limestone and gypsum (Table 1).

TABLE-US-00001 TABLE 1 Mineralogical analysis by X-ray diffraction of the cement composition used. Phase name Formula Weight content (%) Alite Ca.sub.3SiO.sub.5 25.3-32.7 Belite Ca.sub.2SiO.sub.5 5.7-15.2 Aluminate Ca.sub.3Al.sub.2O.sub.6 0.3-2.5 Ferrite Ca.sub.4Al.sub.2Fe.sub.2O.sub.10 6.8-8.1 Total clinker phases 37.6-59.1 Calcium sulfate 7.6-8.1 Quartz* SiO.sub.2 1.2-1.6 Free lime* CaO 0.1-0.4 Portlandite Ca(OH).sub.2 .sup.0-1.3 Calcite* CaCO.sub.3 13.5-15.sup. Aragonite* CaCO.sub.3 0.0-1.3 Periclase* MgO 0.0-1.7 Dolomite CaMgCO.sub.3 2.2-3.4 Aphthitalite K.sub.3Na(SO.sub.4).sub.2 0.0-0.5 Thenardite* Na.sub.2SO.sub.4 0.2-0.3 Syngenite K.sub.2Ca(SO.sub.4).sub.2 H.sub.20 0.0-0.7 Mullite Al.sub.6Si.sub.2O.sub.13 1.8-2.0 Hematite Fe.sub.2O.sub.3 0.0-0.7 Amorphous phases 16.2-17.4 Kaolinite Al.sub.2Si.sub.2O.sub.5(OH).sub.4 2.7-3.4

Description of the Polymers Used:

[0171] The polymers used in the Examples are comb polymers having pendant groups linked to the main carbon chain either by ether groups (polymers 5 and 6), or by ester groups (polymers 1 to 4 and 7).

[0172] The comb polymers having pendant groups linked to the main carbon chain by ether groups were obtained by free radical polymerization with HPEG 2400 and are composed of the units of following formulas:

##STR00005##

where a, b and q are such as defined in Table 2 below. The mean total number of units in the polymer is the sum of the mean number of units of formula (I) and the mean number of units of formula (II).

[0173] Polymer 5 is a polymer such as defined in the application.

[0174] The percentage in units of formula (I) in polymer 6 is higher than 30%. It is therefore a comparative polymer.

[0175] The comb polymers having pendant groups linked to the main carbon chain by ester groups (comparative) were obtained by polymerization followed by post-esterification to graft the pendant groups, for example with MPEG 750 for polymer 7, or a MPEG mixture for polymers 1 and 4 (two values of q in Table 2 below). They are composed of the units of following formulas (XI) and (XII):

##STR00006##

where R is H or a methyl.

[0176] The mean total number of units in the polymer is the sum of the mean number of units of formula (XI) and the mean number of units of formula (XII).

TABLE-US-00002 TABLE 2 q, a, b and mean total number of units in each tested polymer, and preparation method. Composed of the units Preparation Polymer of formulas q a* b* method 1 (compar- (XI) & (XII) q1 = 0.20 0.80 Polymerization then ative) with R = Me 114 = post-esterification q2 = 45 2 (compar- (XI) & (XII) 17 0.25 0.75 Polymerization then ative) with R = Me post-esterification 3 (compar- (XI) & (XII) 45 0.20 0.80 Polymerization then ative) with R = Me post-esterification 4 (compar- (XI) & (XII) 31 0.40 0.60 Polymerization then ative) with R = Me q1 = 45 post-esterification q2 = 17 5 (inven- (I) & (II) 50 0.18 0.82 Free radical tion) polymerization 6 (compar- (I) & (II) 50 0.33 0.67 Free radical ative) polymerization 7 (compar- (XI) & (XII) 17 0.47 0.53 Polymerization then ative) with R = H post-esterification *determined by gel permeation chromatography (GPC). Whether during free radical polymerization or during post-esterification, a certain amount of residual monomer remains in solution after synthesis. These residual monomers can be quantified by GPC. The difference between this residual amount and the quantity of starting monomer is the quantity of monomer that has been polymerized and therefore a, after which b = 1 a.

Experimental Protocol:

[0177] The cement composition was prepared as follows using a KENWOOD KM011 CHEF TITANIUM mixer with stainless steel bowl (capacity 4.6 litres) and a metal K-shaped mixing paddle (height 13 cm and width 13.6 cm); the fluidity of the composition was measured as follows: [0178] 1. The water and admixture were weighed in the mixer bowl, and the mixer set in operation at a speed of 43 rpm. [0179] 2. The chronometer was started and the cement composition was added to the bowl in 30 seconds. [0180] 3. The speed was increased to 96 rpm and the mixture was mixed for one minute. [0181] 4. The mixer was stopped for 30 seconds, and any admixed cement composition sprayed onto the walls was scraped towards the centre with a spatula. [0182] 5. The admixed cement composition was mixed for one minute at 96 rpm.
After mixing, the admixed cement composition obtained, which was in the form of a slurry, was poured into the cylindrical measuring cell of a Kinexus Pro (Netzsch) rheometer equipped with measuring geometry of vane type.

[0183] Five minutes after the start of mixing, the admixed cement composition was subjected to pre-shearing for one minute at a strain rate of 200 s.sup.1. The admixed cement composition was then subjected to a series of decreasing levels of strain rate on a logarithmic scale with steps of 200 to 0.01 s.sup.1 and the rheometer recorded the stress to be applied at each point. This allows a flow curve to be plotted, linking the stress applied to obtain each value of strain rate. These flow curves show a minimum stress which is interpreted as a threshold stress, namely a minimum stress to be applied to cause flowing. This value varies inversely to fluidity, it is therefore sought to reduce this value as much as possible.

[0184] Thereafter, the flow curve is measured every 30 minutes up to 120 min after the start of mixing, to check changes in fluidity over time.

[0185] In a first series of tests, the ratio of the weight of water to the weight of the cement composition (dry weight) was 0.45. The admixture was composed of one of the polymers (no set retarding agent). For each test, the proportion of polymer was 0.1 weight % relative to the dry weight of the cement composition to be fluidified. The results are given in Table 3.

TABLE-US-00003 TABLE 3 Threshold stress of the admixed cement composition according to the type of polymer in the admixture. Threshold stresses (Pa) Polymer 5 min 30 min 60 min 90 min 120 min 1 (comparative) 6.7 19.2 37.2 45.9 54.3 2 (comparative) 20.9 23.5 34.7 41.3 48.8 3 (comparative) 11.4 22.6 35.0 42.6 49.7 4 (comparative) 32.8 23.2 36.4 45.9 59.4 5 (invention) 0.8 2.6 5.8 12.1 17.8

[0186] These results show that polymer 5 of the invention is by far the best fluidifier. It allows significant lowering of the initial threshold stress and improved fluidity retention of the admixed cement composition over a time of 120 minutes or longer.

[0187] In a second series of tests, the ratio of the weight of water to the weight of the cement composition (dry weight) was 0.35. The admixture was composed of polymer 5 (no set retarding agent). Having regard to the smaller quantity of water compared with the first series of tests, the dosage of polymer 5 was increased to 0.15 weight % relative to the dry weight of the cement composition to be fluidified, to obtain the desired threshold stresses. The results are given in Table 4 (line: polymer 5).

[0188] In a third series of tests, the ratio of the weight of water to the weight of the cement composition (dry weight) was maintained at 0.35. The admixture was composed of polymer 5 and a solution of sodium gluconate as set retarding agent. The dosage of polymer 5 was reduced to 0.10 weight % relative to the dry weight of the cement composition to be fluidified. The dosage of sodium gluconate was 0.08 weight % relative to the dry weight of the cement composition to be fluidified. The results are given in Table 4 (line: polymer 5+sodium gluconate).

TABLE-US-00004 TABLE 4 Threshold stress of the admixed cement composition according to type of admixture. Threshold stresses (Pa) Admixture 5 min 30 min 60 min 90 min 120 min Polymer 5 (invention) 3.5 9.8 17.4 22.8 28.6 Polymer 5 + sodium 1.0 2.9 5.1 8.0 9.5 gluconate (invention)

[0189] The results show that the addition of a set retarding agent allows an improvement in the fluidity of the admixed cement composition, even when reducing the dosage of polymer 5.

[0190] In a fourth series of tests, the ratio of the weight of water to the weight of the cement composition (dry weight) was maintained at 0.35. The admixture was composed of one of the polymers and a solution of sodium gluconate as set retarding agent. The dosage of the polymer was 0.125 weight % relative to the dry weight of the cement composition to be fluidified. The dosage of sodium gluconate was 0.1 weight % relative to the dry weight of the cement composition to be fluidified. The results are given in Table 5.

TABLE-US-00005 TABLE 5 Threshold stress of the admixed cement composition according to type of admixture. Threshold stresses (Pa) Admixture 5 min 30 min 60 min 90 min 120 min Polymer 5 + sodium 5.2 4.8 4.9 4.8 5.4 gluconate (invention) Polymer 6 + sodium 76.8 57.1 95.8 115.1 120.7 gluconate (comparative) Polymer 7 + sodium 68.1 49.7 61.8 72.9 87.3 gluconate (comparative)

[0191] These results show that an admixture comprising polymer 5 of the invention and sodium gluconate as set retarding agent is by far the best fluidifier compared with admixtures comprising other polymers and the same set retarding agent.

EXAMPLE 2

[0192] Impact of the type of set retarding agent in the admixture on the fluidification of a cement composition.

[0193] Polymer 5 described above was tested with different set retarding agents on a cement composition to be fluidified. A rheological study with a hydration time of 2 hours was carried out.

[0194] The cement composition and the experimental protocol were the same as those described in Example 1.

[0195] The selected set retarding agents were conventional retarders used to reduce the hydrating kinetics of a cement. Among these, carboxylic acids (citric acid, tartaric acid, salicylic acid), a phosphonic acid in neutral form or a salt thereof, and a sugar of sucrose type were evaluated.

[0196] The ratio of the weight of water to the weight of the cement composition (dry weight) was 0.35. The admixture was composed of polymer 5 and the set retarding agent. The dosage of polymer 5 was 0.125 weight % relative to the dry weight of the cement composition to be fluidified. The dosage of set retarding agent was 0.1 weight % relative to the dry weight of the cement composition to be fluidified. The results are given in Table 6.

TABLE-US-00006 TABLE 6 Threshold stress of the admixed cement composition according to the type of admixture comprising polymer 5 and a different set retarding agent. Threshold stresses (Pa) Admixture 5 min 30 min 60 min 90 min 120 min Polymer 5 + 5.2 4.8 4.9 4.8 5.4 sodium gluconate Polymer 5 + 5.9 49.0 76.7 71.4 68.8 citric acid Polymer 5 + 9.6 164.8 256.3 280.7 258.3 tartaric acid Polymer 5 + 70.7 111.2 92.1 81.0 78.1 salicylic acid Polymer 5 + 18.0 49.2 43.2 37.4 34.0 sugar (sucrose) Polymer 5 + 2.1 3.1 4.4 5.7 6.8 phosphonic acid (ATMP)

[0197] These results show that the admixtures which, in addition to polymer 5, comprise sodium gluconate or the phosphonate allow better fluidification than those comprising other set retarding agents.

EXAMPLE 3

[0198] Impact of admixtures on the hydrating kinetics of the cement composition.

[0199] Isothermal microcalorimetry tests (TAM Air calorimeter, TA Instruments) allowed evaluation of the impact of the admixtures on the hydrating kinetics of the cement composition. Since hydration of the cement composition is an exothermal reaction, isothermal calorimetry allows the obtaining of changes in the flow of heat released per gram of the cement composition as a function of time.

[0200] The cement slurry was prepared from a mixture of cement material, admixtures and water. A water-to-binder ratio (W/B) of 0.35 was determined for all the slurries. The agitation system was composed of a turbine agitation paddle (diameter 2.5 cm) attached to an IKA mixer, and a 50 mL stainless steel beaker. The admixtures and water were first weighed and mixed in the stainless steel beaker. The water contributed by the admixture was subtracted from the mixing water. The cement composition powder was added to the water, this addition marking the start of hydration. The suspension was mixed for one minute at a speed of 500 rpm. Mixing was then stopped and the edges of the beaker and the paddle were scraped for one minute. Finally, agitation was restarted at a speed of 1000 rpm for one minute. The cement slurry was then ready for the analyses.

[0201] To reproduce the same experimental conditions as those for the rheological tests, the cement slurries were prepared: [0202] without admixture (reference), [0203] with polymer 5 at a dosage of 0.15 weight % relative to the dry weight of the cement composition (without set retarding agent), or [0204] with a mixture of polymer 5 at 0.1 weight % and sodium gluconate at 0.08 weight % relative to the dry weight of the cement composition.
The results are given in FIG. 1 and show that polymer 5 at a dosage of 0.15 weight % relative to the dry weight of the cement composition provides a delay of about 30 minutes compared with the reference containing the cement composition without admixture. Polymer 5 at a dosage of 0.1 weight % relative to the dry weight of the cement composition in combination with sodium gluconate at a dosage of 0.08 weight % relative to the dry weight of the cement composition delay the hydration kinetics of the cement compositions by about 6 hours compared with the reference containing the cement composition without admixture. However, the set retarding agent has no impact on the intensity of the main hydration peak of the cement composition.

EXAMPLE 4

[0205] Example with another cement composition. Impact of the type of polymer and presence of a set retarding agent on the fluidification of cement composition 2.

[0206] Tests were conducted with a cement composition 2 comprising a different type of clinker from the one previously used (out of stock), but having the mixture of metakaolin, limestone and gypsum such as described in Table 1. Having regard to the different type of clinker, the following results cannot strictly be compared with those of Tables 4 and 5 above.

[0207] The cement composition 2 used was composed of about 50% clinker and about 50% of the mixture of metakaolin, limestone and gypsum (Table 7).

TABLE-US-00007 TABLE 7 Minralogical analysis by X-ray diffraction of cement composition 2 used. Phase name Formula Weight content (%) Alite Ca.sub.3SiO.sub.5 24.7-25.7 Belite Ca.sub.2SiO.sub.5 11.6-12.6 Aluminate Ca.sub.3Al.sub.2O.sub.6 0.9-1.9 Ferrite Ca.sub.4Al.sub.2Fe.sub.2O.sub.10 5.9-9.9 Total clinker phases 44.1-51.1 Calcium sulfate 7.6-8.1 Quartz* SiO.sub.2 1.2-1.6 Free lime* CaO 0.1-0.3 Portlandite Ca(OH).sub.2 0.0-0.5 Calcite* CaCO.sub.3 13.5-15.0 Aragonite* CaCO.sub.3 0.0-0.2 Periclase* MgO 0.0-0.2 Dolomite CaMgCO.sub.3 2.2-3.4 Aphthitalite K.sub.3Na(SO.sub.4).sub.2 0.0 Thenardite* Na.sub.2SO.sub.4 0.2-0.3 Syngenite K.sub.2Ca(SO.sub.4).sub.2 H.sub.20 0.0-0.7 Mullite Al.sub.6Si.sub.2O.sub.13 1.8-2.0 Hematite Fe.sub.2O.sub.3 0.0 Amorphous phases 16.2-17.4 Kaolinite Al.sub.2Si.sub.2O.sub.5(OH).sub.4 2.7-3.4

[0208] The experimental protocol was the same as those described in Examples 1 and 2.

[0209] The ratio of the weight of water to the weight of cement composition 2 (dry weight) was 0.35.

[0210] The admixture was: [0211] either polymer 5 (free of set retarding agent) at a dosage of 0.1 weight % relative to the dry weight of cement composition 2 to be fluidified, [0212] or polymer 5 and sodium gluconate as set retarding agent at a dosage of 0.1 weight % of polymer 5 and 0.08 weight % sodium gluconate, each relative to the dry weight of the cement composition 2 to be fluidified, [0213] or polymer 6 (comparative) (free of set retarding agent) at a dosage of 0.1 weight % relative to the dry weight of the cement composition 2 to be fluidified.

[0214] The results are given in Table 8.

TABLE-US-00008 TABLE 8 Threshold stress of admixed cement composition 2 according to type of admixture. Set Threshold stresses (Pa) retarding 5 30 60 90 120 Admixture agent min min min min min invention 0.1% none 20.0 35.2 53.9 68.6 86.6 polymer 5 invention 0.1% 0.08% 1.6 0.7 0.8 1.0 1.0 polymer 5 sodium gluconate comparative 0.1% none 24.6 56.2 93.2 125.0 160.2 polymer 6

[0215] The use of 0.1 weight % of polymer 5, relative to the dry weight of the cement composition 2 to be fluidified, leads to an increase in the threshold stress of the admixed cement composition 2, whereas the use of 0.1 weight % of polymer 5 and 0.08 weight % of sodium gluconate, each relative to the dry weight of the cement composition 2 to be fluidified, allows the threshold stress to be maintained at a constant low level.

[0216] The use of 0.1 weight % of polymer 6 (comparative), relative to the dry weight of the cement composition 2 to be fluidified, leads to a stronger increase in the threshold stress of the admixed cement composition 2 than that obtained with the use of 0.1 weight % of polymer 5 (invention) relative to the dry weight of the cement composition 2 to be fluidified. Polymer 6 exhibits lower performance than polymer 5.