EP2018355A1

EP2018355A1 - Use of a pulverulent composition comprising titania and an inorganic binder to increase early strength

Info

Publication number: EP2018355A1
Application number: EP07727753A
Authority: EP
Inventors: Christoph Tontrup; Reinhard Trettin; Michael Geyer
Original assignee: Evonik Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2006-05-05
Filing date: 2007-04-04
Publication date: 2009-01-28
Also published as: WO2007128630A1; DE102006020878A1; TW200815303A

Abstract

Use of a pulverulent composition comprising an inorganic binder and, based on the binder, 0.25 to 5% by weight of finely divided titania for the preparation of products having high early strength.

Description

Use of a pulverulent composition comprising titania and an inorganic binder to increase early strength

The invention relates to the use of a pulverulent composition which comprises titania and an inorganic binder to increase the early strength of products prepared therewith .

It is known to utilize the photocatalytic properties of titania in cement mixtures.

In WO98/05601, the titania is used to obtain colour and brilliance of special concretes. It is especially explained that the compressive strength of concretes is not influenced by the titania.

In WO01/00541, similar cases are disclosed, it being explained that the properties of the concretes obtained is not influenced.

In JP2000117117 , a mixture is disclosed which comprises 100 parts by weight of cement and 10 to 150 parts by weight of titania .

In GB-A-849175, a coating composition for concrete is, which of white cement and comprises up to 3% by weight of titania .

In summary, it can be said that in the prior art titania is only disclosed as a photocatalytically active substance in cement mixtures.

It has now surprisingly been found that the early strength of products comprising hydraulic binders can be increased by a pulverulent composition which comprises titania and an inorganic binder.

The invention relates to the use of a pulverulent composition which comprises an inorganic binder and, based on the binder, 0.25 to 5% by weight of finely divided titania, for the preparation of products having high early strength.

Contents of titania of more than 5% by weight as a rule lead to a relatively poor processability of the water- treated composition (e.g. low degree of slump of a fresh concrete); with contents of less than 0.25% by weight the early strength is only increased insignificantly.

Preferably, the content of titania is 0.25 to 2% by weight, a content of 0.25 to 1% by weight being particularly preferred.

A product having high early strength comprising inorganic binder is here to be understood as meaning a product which at any desired point in time in the first 48 hours of hardening of the product achieves strengths which are at least 30% higher than the reference value of a product without titania.

By an inorganic binder, inorganic substances processable in the plastic state are meant, which in the course of a certain time harden and at the same time firmly cement other substances to one another, for example relatively coarse or relatively fine aggregates. The inorganic binders according to the invention include hydraulic binders which spontaneously harden in the presence of water (e.g. cement, hydraulic limes), latent hydraulic binders which exhibit solidification reactions only after a pretreatment, pozzolanic materials which react to give stable products in the presence of water and calcium hydroxide (e.g. silica dust), non-hydraulic binders which only harden in air (e.g. gypsum plaster, anhydrous binders, magnesia binders, non- hydraulic mortars, phosphate binders and water glass) .

Preferably, hydraulic binders, such as cement and hydraulic limes, can be used. Finely divided titania is to be understood as meaning one which has a BET surface area of 20 to 400 m²/g. Preferably, a titania can be employed which has a BET surface area of 40 to 120 m²/g.

It has further proven advantageous to employ a titania which is present in the form of aggregated particles.

Particles of this type can be produced, for example, by flame oxidation or flame hydrolysis. Here, oxidizable and/or hydrolysable starting substances are as a rule oxidized or hydrolysed in a hydrogen-oxygen flame. Suitable starting substances are organic and inorganic substances. On account of its good availability, for example, titanium tetrachloride is particularly suitable. The particles of the titania powder thus obtained are as far as possible pore-free and have free hydroxyl groups on the surface.

A highly suitable, commercially obtainable titania powder is, for example, AEROXIDE® TiO₂ P25, Degussa, having a BET surface area of 50 ± 15 m²/g. Furthermore, the titanias disclosed in WO2005/054136 having a very narrow distribution of the primary particle diameters can advantageously be used.

It is also possible to use mixed oxide powders which, in addition to titania as the main constituent, contain a further metal oxide. These can be, for example, titanium- silicon (for example from DE-A-4235996) , titanium-aluminium (for example from the German patent application having the application number 102004062104.7 of 23 December 2004) or titanium-zirconium mixed oxide powders, for example from the German patent application having the application number 102004061702.3 of 22 December 2004 or doped titania powders as disclosed in EP-A-1138632.

The titania or the titanium mixed oxide powder can also be employed in surface-modified form. Preferably, the following silanes, individually or as a mixture, can be employed for this:

Organosilanes (RO)₃Si(C_nH_2n+I) and (RO) ₃Si (C_nH_2n-I) with R = alkyl, such as methyl, ethyl, n-propyl, i-propyl, butyl and n=l-20.

Organosilanes R' _x (RO) _ySi (C_nH_2n+i) and R' _x (RO) _ySi (C_nH_2n-i) with R=alkyl, such as methyl, ethyl, n-propyl, i-propyl, butyl; R'=alkyl, such as methyl, ethyl, n-propyl, i-propyl, butyl; R' =cycloalkyl; n=l-20; x+y=3, x=l, 2; y=l, 2.

Haloorganosilanes X₃Si (C_nH_2n+i) and X₃Si (C_nH_2n-I) with X=Cl, Br; n=l-20.

Haloorganosilanes X₂ (R' ) Si (C_nH_2n+i) and X₂ (R' ) Si (C_nH_2n_i) with X=Cl, Br, R' = alkyl, such as methyl, ethyl, n-propyl, i-propyl, butyl-; R' =cycloalkyl; n=l-20

Haloorganosilanes X (R' ) ₂Si (C_nH_2n+i) and X (R' ) ₂Si (C_nH_2n-I) with X=Cl, Br; R' = alkyl, such as methyl-, ethyl-, n- propyl-, i-propyl-, butyl-; R' =cycloalkyl; n=l-20

Organosilanes (RO) ₃Si (CH₂) _m-R' with R=alkyl, such as methyl-, ethyl-, propyl-; m=0,l-20; R'= methyl, aryl such as -C₆H₅, substituted phenyl radicals, C₄F₉, OCF₂-CHF-CF₃, C₆F₁₃, OCF₂CHF₂, NH₂, N₃, SCN, CH=CH₂, NH-CH₂-CH₂-NH₂, N- (CH₂-CH₂-NH₂) ₂, 0OC(CH₃)C=CH₂, OCH₂- CH(O)CH₂, NH-CO-N-CO- (CH₂)₅, NH-COO-CH₃, NH-COO-CH₂-CH₃, NH- (CH2)₃Si (OR)₃, S_x- (CH₂) ₃Si (OR)₃, SH, NR¹R^{1 1}R' ' ' with R'=alkyl, aryl; R' '=H, alkyl, aryl; R' ' '=H, alkyl, aryl, benzyl, C₂H₄NR' ' ' ' R' ' ' ' ' with R' ' ' ' = H, alkyl and R' ' ' ' ' = H, alkyl. Organosilanes (R") _x (RO) _ySi (CH₂)_m-R' with R"=alkyl, x+y=3; cycloalkyl, x=l,2, y=l,2; m=0,l to 20; R'=methyl, aryl, such as C₆H₅, substituted phenyl radicals, C₄F₉, OCF₂-CHF-CF₃, C₆Fi₃, OCF₂CHF₂, NH₂, N₃, SCN, CH=CH₂, NH-CH₂-CH₂-NH₂, N- (CH₂-CH₂-NH₂) ₂, 0OC(CH₃)C=CH₂, OCH₂- CH(O)CH₂, NH-CO-N-CO-(CH₂)₅, NH-COO-CH₃, NH-COO-CH₂-CH₃, NH- (CH₂)₃Si(OR)₃, S_x-(CH₂)₃Si(OR)₃, SH, NR¹R^{1 1}R''' with R'=alkyl, aryl; R' '=H, alkyl, aryl; R' ' '=H, alkyl, aryl, benzyl, C₂H₄NR' ' ' ' R' ' ' ' ' with R' ' ' '=H, alkyl and R' ' ' ' ' = H, alkyl.

Haloorganosilanes X₃Si (CH₂) _m-R'

X=Cl, Br; m=0,l-20; R' = methyl, aryl such as C₆H₅, substituted phenyl radicals, C₄F₉, OCF₂-CHF-CF₃, C₆F_i3, 0- CF₂-CHF₂, NH₂, N₃, SCN, CH=CH₂, NH-CH₂-CH₂-NH₂, N-(CH₂-CH₂- NH₂) ₂, -0OC(CH₃)C=CH₂, OCH₂-CH(O)CH₂, NH-CO-N-CO- (CH₂) ₅, NH- COO-CH₃, -NH-COO-CH₂-CH₃, -NH- (CH₂) ₃Si (OR) ₃, -Sx- (CH₂) ₃Si (OR) 3, where R = methyl, ethyl, propyl, butyl and x=l or 2, SH.

Haloorganosilanes RX₂Si (CH₂) _mR' X=Cl, Br; m=0,l-20; R' = methyl, aryl such as C₆H₅, substituted phenyl radicals, C₄F₉, OCF₂-CHF-CF₃, C₆F_i3, 0- CF₂-CHF₂, NH₂, N₃, SCN, CH=CH₂, NH-CH₂-CH₂-NH₂, N-(CH₂-CH₂- NH₂) ₂, -0OC(CH₃)C=CH₂, OCH₂-CH(O)CH₂, NH-CO-N-CO- (CH₂) ₅, NH- COO-CH₃, -NH-COO-CH₂-CH₃, -NH- (CH₂) ₃Si (OR) ₃, -Sx- (CH₂) ₃Si (OR) 3, where R = methyl, ethyl, propyl, butyl and x=l or 2, SH.

Haloorganosilanes R₂XSiCH₂)_mR'

X=Cl, Br; m=0,l-20; R' = methyl, aryl such as C₆H₅, substituted phenyl radicals, C₄F₉, OCF₂-CHF-CF₃, C₆F_i3, 0- CF₂-CHF₂, NH₂, N₃, SCN, CH=CH₂, NH-CH₂-CH₂-NH₂, N-(CH₂-CH₂-

NH₂) ₂, -0OC(CH₃)C=CH₂, OCH₂-CH(O)CH₂, NH-CO-N-CO- (CH₂) ₅, NH- COO-CH₃, -NH-COO-CH₂-CH₃, -NH- (CH₂) ₃Si (OR) ₃, -Sx- (CH₂) ₃Si (OR) 3, where R = methyl, ethyl, propyl, butyl and x=l or 2, SH. Silazanes R¹R₂SiNHSiR₂R' with R, R' = alkyl, vinyl, aryl

Cyclic polysiloxanes D3, D4, D5 where D3, D4 and D5 is understood as meaning cyclic polysiloxanes having 3, 4 or 5 units of the type -0- Si (CH₃) ₂, e.g. octamethylcyclotetrasiloxane = D4

Me₀

Me₂Si

O SiMe,

Si-O Me₀

D4

Polysiloxanes and silicone oils of the type

with

R = alkyl, aryl, (CH₂)_n-NH₂,H R' = alkyl, aryl, (CH₂)_n-NH₂,H

R" = alkyl, aryl, (CH₂)_n-NH₂,H

R'" = alkyl, aryl, (CH₂) _n-NH₂, H

Y = CH₃, H, C_zH_2z+i with z=l-20,

Si(CH₃)₃, Si(CH₃)₂H, Si (CH₃) ₂0H, Si (CH₃) ₂ (OCH₃) , Si(CH₃)₂(C_zH_2z+1) where

R' or R" or R'" is (CH₂) _Z-NH₂ and z = 1 - 20, m = 0,1,2,3, ...oo, n = 0,1,2,3, ...°°, u = 0,1,2,3, ...°°. Preferably, the following substances can be employed as surface modification agents: octyltrimethoxysilane, octyltriethoxysilane, hexamethyldisilazane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, dimethylpolysiloxane, glycidyloxypropyltrimethoxysilane, glycidyloxypropyltriethoxysilane, nonafluorohexyl- trimethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, aminopropyltriethoxysilane .

Particularly preferably, octyltrimethoxysilane, octyltriethoxysilane and dimethylpolysiloxanes can be employed.

A suitable surface-modified titania powder is, for example, AEROXIDE^® TiO₂ T805, Degussa, having a BET surface area of 45 ± 10 m²/g and a carbon content of 2.7 - 3.7% by weight.

A pulverulent composition can also be used in which titania is present sprayed onto the inorganic binder.

In this case, it is advantageous if the moistness of the composition in comparison to the moistness of the composition before spraying on the dispersion increases by at most 5% and particularly preferably at most 1.5%. For example, before spraying the inorganic binder can have a moistness of 2%, after spraying of at most 7% and particularly preferably at most 3.5% moistness. As a result of the small increase in moistness, it is guaranteed that the composition is present in pulverulent form even after spraying. The spraying can be carried out by means of atomization of aqueous dispersions according to processes known to the person skilled in the art.

Advantageously, the dispersions are highly filled, aqueous dispersions of small particle size. Titania dispersions are particularly preferred, having a titania content of at least 30% by weight, based on the dispersion. Furthermore, those dispersions are preferred in which the titania particles have an average aggregate diameter in the dispersion of not more than 2 μm. Particularly preferably, dispersions having an average aggregate diameter of less than 300 nm can be employed. The pH of the dispersion is preferentially 2 to 4 or 9 to 13. However, dispersions in the range from 4 to 9 can also be employed. The pHs are adjusted by addition of acids or bases. The dispersions can furthermore contain additives which counteract sedimentation and reagglomeration . Acids, bases and/or additives should be chosen such that no adverse interactions occurs with the constituents of the hydraulic binder. As a rule, the liquid phase of the dispersion is aqueous .

Table 1 shows suitable dispersions by way of example.

Table 1 : Titania dispersions

The median values of the particle size distribution (d₅o) were determined by means of dynamic light scattering using a measuring instrument from Horiba (LB 500) .

Commercially obtainable titania dispersion are, for example, VP Disp W 740 X (40% by weight of TiO₂, d₅₀ < 0.2 μm, pH 6-9) and VP Disp W 2730 X (30% by weight of TiO₂, d₅₀ < 0.1 μm) .

Examples

Types of titania employed

a) AEROXIDE^® TiO₂ P25 (Degussa AG) , BET surface area

50±15 m²/g, loss on drying < 1.5% by weight, pH 3.5-4.5.

b) TiO₂-2: titania powder according to WO2005/054136, Example A7, BET surface area 91 m²/g.

c) pigmentary titania : BET surface area < 10 m²/g.

d) silicon-titanium mixed oxide: according to DE-A- 102004001520, Example 12, BET surface area 43 m²/g, content of titania 49% by weight, content of silica 51% by weight.

e) TiO₂ dispersion 1 (aqueous) : TiO₂ BET surface area:

90 m²/g, TiO₂ content 30% by weight, d₅₀ = < 0.2 μm, pH = 2 - 4, stabilization HNO_3.

f) TiO₂ dispersion 2 (aqueous) : TiO₂ BET surface area: 50 m²/g, TiO₂ content 30% by weight, d₅₀ = <0.3 μm, pH = 10-13, stabilization NaOH_.

Example 1

An inorganic binder (CEM I 52.5R HS/NA from Holcim) containing 1.5% by weight of the cement of AEROXIDE® TiO₂ P25 is first mixed intensively in a powder mixer. Using this pulverulent composition, a standard mortar (water-cement value 0.45) is prepared according to DIN EN 196. After 24 h and 48 h, the compressive strength of the mortar is measured on prisms of size 1 x 1 x 4 cm following DIN 1164. The experiment is repeated without use of titania. The results of the comparison are shown in Table 1.

Table 1: Early strength after 24 and 48 h

*) based on cement;

From Table 1, it is clear that as a result of addition of titania an increase in the early strength of the mortar after 24h by almost 50% compared to the reference without titania is achieved. The value after 48h shows that titania acts more strongly on the strength at early periods of the cement hydration than at later periods. Measurements of the strength after 7 and 28 days show no significant increases in the strength in comparison to the sample without titania. The titania thus acts only on the early strength and not on the final strength.

Example 2

Pulverulent compositions of inorganic binder (CEM I 42.5 R, Buderus) and various titanias (see Table 2) are first prepared by intensive blending in a powder mixer. All preparations contain an amount of titania of 0.5% by weight of the cement. Using this pulverulent composition, a standard mortar (water-cement value 0.45) is prepared according to DIN EN 196. After 24 h, the compressive strength of the mortar is measured on prisms of size 1 x 1 x 4 cm following DIN 1164. The experiment is repeated without use of titania.

Table 2 : Influence of various types of titania on the early strength

*) based on cement;

Table 2 shows that as a result of the use of finely divided titania a very considerable increase in the early strength can be achieved. This turns out to be higher, the higher the specific surface area. As a result of the use of low- surface area, pigmentary titania, however, only a slight increase in the early strength is achieved. The early strength can also be markedly increased by the use of finely divided titania-containing mixed oxides.

Example 3

Pulverulent, titania-containing compositions are first prepared by spraying various titania dispersions (see Table 3) onto CEM I 42.5 R (Buderus) in an intensive mixer (15 1 volume, Maschinenfabrik Gustav Eirich GmbH & Co KG) . Using this pulverulent composition, a standard mortar (water- cement value 0.45) is prepared according to DIN EN 196. After 24 h, the compressive strength of the mortar is measured on prisms of size 1 x 4 x 4 cm following DIN 1164 The experiment is repeated without use of titania.

Table 3 : Use of titania dispersions

$) titania dispersion 1; &) titania dispersion 2 ; based on cement;

Table 3 shows that a marked increase in the early strength can also be achieved using compositions which comprise a sprayed-on titania dispersion.

Example 4 : Investigation of the strength-increasing action of a titania addition in standard mortar samples

Starting substances: standard sand, CEM I 42.5 R (Buderus) , TiO₂ P 25 (Degussa) , water.

The cement and Aeroxide TiO₂ P25 are first mixed with intensive mixing. The test articles are then prepared according to DIN EN 196 (water-cement value: 0.45) . The strengths of the mortar prisms (1.5 x 1.5 x 6.0 cm) are determined according to DIN 1164. Table 4: Flexural/compressive strengths (in N/mm²) as a function of the amount of titania added (in % by weight)

Titania addition

0 .0 0 .1 0.5 1.0 1 .5 5.0

3. 67/ 3. 76/ 4.56/ 4.77/ 6. 64/ 4 .52/

Id

12.16 12.48 17.72 18.23 18.25 16.41

7. 21/ 7. 49/ 8.29/ 8.03/ 7. 34/ 5 .94/

2d 29.05 30.03 33.99 38.62 33.08 29.97

Table 4 shows that very low concentrations of 0.1% by weight of cement only cause a slight increase in the early strength. On addition of 0.5% by weight of titania based on the binder content, however, a considerable increase in strength of the samples is to be observed. The strengths measured in Table 4 after day 1 also show clearly that the early strength cannot always be increased further as a result of increase in the titania concentration. The strength after 2 days (2d) decreases noticeably even at concentrations of 5%. In summary, it can be said that there is an optimum between amounts of titania which are not yet active and amounts of titania which no longer increase early strength.

Example 5: Reactivity of titania in the hydration process of cement

3.00 g of CEM I 42.5 R in one portion and a pulverulent composition of 3.00 g of CEM I 42.5 R with a 2% by weight titania addition in one portion are mixed in a test tube and uniformly compacted and the distilled water needed for the hydration (1.20 g) is drawn into a syringe having a needle. Subsequently, the test tube and the syringe are inserted into the sample space of the heat flow calorimeter for thermostatting at 25°C. After reaching temperature equilibrium, the water is sprayed into the powder bed and the measurement is started. Figure 1 shows the hydration course of CEM 42.5 R I (Curve a) and the pulverulent composition of CEM 42.5 R I with a 2% by weight titania addition (Curve b) . It is seen that the heat development per time is markedly higher in the initial peak of the sample with a titania addition. Furthermore, an earlier increase and decrease in the evolution of heat in the acceleration phase as a result of a shorter induction period is to be seen, whereby the acceleration of the hydration of the cement and thus the early strength-increasing action as a result of titania addition is demonstrated.

Figure 2 shows the hydration course of CEM 42.5 R I (Curve a) and CEM 42.5 R I with a 2% by weight titania addition (Curve b) . The amount of heat given off after 24 hours is nearly identical in both samples. However, the earlier heat development in the acceleration phase in the case of the sample with a titania addition is also clearly to be seen here .

Claims

Patent claims :

1. Use of a pulverulent composition comprising an inorganic binder and, based on the binder, 0.25 to 5% by weight of finely divided titania for the preparation of products having high early strength.

2. Use according to Claim 1, characterized in that the BET surface area of the titania particles is 40 to 120 m²/g.

3. Use according to Claims 1 or 2, characterized in that the pulverulent composition contains titania sprayed onto the inorganic binder.