IL153588A

IL153588A - Waterproofed cementitious compositions and method of making the same

Info

Publication number: IL153588A
Application number: IL153588A
Authority: IL
Original assignee: Constr Res & Tech Gmbh; Mbt Holding Ag
Priority date: 2001-05-08
Filing date: 2002-12-22
Publication date: 2009-09-22
Also published as: ZA200300162B; NO20030070D0; GB0111145D0; EP1390318A1; NO20030070L; IL153588A0; WO2002090287A1; YU703A

Description

153588/2 Waterproofed cementitious compositions and method of making the same Construction Research & Technology GmbH C. 142593 WATERPROOFING ADMIXTURE This invention relates to the waterproofing of porous cementitious materials and to admixtures for waterproofing.

Cementitious materials such as cement and concrete and various artificial building stones based on these are frequently made into walls, floors, roofs and the like, where they will be exposed to water. As such materials are always inherently porous, water can penetrate them. Although appropriate formulation can do much to reduce this inherent porosity, it can never completely get rid of it. There is therefore a substantial industry that seeks to provide waterproofing to such cementitious surfaces. Up to now, there have been two alternative methods, internal and external. The internal methods involved adding a waterproofing substance to a fluid cementitious mix before hardening. The materials that have been most commercially successful in this regard have been known water-repellent, fatty acid-based materials, typically stearates and oleates. However, relatively large quantities of such materials are needed.

The external treatments have involved coating the surface of the hardened cementitious material with a waterproofing substance. Such substances contain materials that are highly water repellent and are of low viscosity, to allow them to penetrate into the cementitious material. Particularly successful types of waterproofing materials are those based on organosilicon materials. Aqueous emulsions are most frequently encountered, but solvent-based preparations and even organosilicon materials that are inherently sufficiently fluid have also been used. Multiple applications are needed for best effect, and the cost of applying such treatment to large structures can be very high.

More recently, it has been proposed to add organosilicon materials as admixtures to cementitious mixes, in an attempt to utilise the good waterproofing properties of the surface-applied materials to the convenience of use of the stearates and oleates. The materials used have been aqueous hydrolysable silane emulsions.

It has now been found that it is possible to give hardened cementitious materials enhanced water impermeability by use of particular organosilicon materials. The invention therefore provides a method of conferring water impermeability on a hardened cementitious composition which is formed from a fluid cementitious mix, by the addition to the mix of an aqueous emulsion of organosilicon material, which material comprises from 0.25-4.5% by weight of the emulsion of an alkoxysilane and from 0.1-2.0% of an alkoxysiloxane.

The invention also provides a waterproof hardened cementitious composition comprising internally an alkoxysilane and an alkoxysiloxane, which had been added as an admixture to a cementitious mix from which the hardened composition was formed.

Although such emulsions are well known for external application to porous cementitious surfaces for waterproofing, it is surprising to find that, not only do they work when added to fluid mixes as admixtures, but they also work exceptionally well, better than the same material externally applied.

In a preferred embodiment of the invention (hereinafter "preferment 1 "), the emulsion is one that contains 1. 0.25 to 2.5% by weight of an alkoxysilane of the general formula R' -Si(OR2)3 I wherein Ri is an alkyl group with 3 to 12 carbon atoms; and R2 is a methyl or ethyl group; 2. 0.2 to 2% by weight of an alkoxysiloxane of the general formula 04-fa+b) wherein R3 is an alkyl group with 1 to 6 carbon atoms, a is 0.8 to 1.2 and b is 0.2 to 1.2; and 3. water to 100%.

More preferably, some of the water may be replaced by from 0.001-0.5% by weight of an emulsifier, 0.001% by weight of filler with an effective surface area of at least 40M /g.

In another preferred embodiment (hereinafter "preferment 2"), the emulsion contains a) 0.5 to 4.5% by weight of an alkoxysilane of the general formula R'-Si-(OR2)3 wherein R1 is an alkyl group with 1 to 16 carbon atoms, and R2 is an alkyl group with 1 to 4 carbon atoms, b) 4.5 to 0.5% by weight of a mixture consisting of a bl) silane of the general formula R3-Si-(OR2)3 wherein R2 has the meaning already given, and R3 is an aminoalkyl group with 1 to 6 carbon atoms or a group of the general formula H2N-(CH2)x R4 -(CH2)y-, in which R4 represents an oxygen, sulphur, -NH- or -NH-CH2-CH2-NH group and x>2 and y>2, or a group of the general formula (R20)3 Si-(CH2)X-NH-(CH2)X-, wherein R2 and x are defined as above, -CnH2„-0-CH2-CH CH2 or O n is a whole number from 1 to 5, and b2) is a polysiloxane of the general formula wherein R5 is a methyl or phenyl group, with the proviso that at least 90% of the R5 groups are methyl groups, and m=20 to 250, the ratio of bl to b2 being such that more than 1 and up to 3 OR2 groups of compound bl correspond to one SiOH group of compound b2, c) 0.05 to 1% by weight of an O/W emulsifier or emulsifier mixture; and d) water to 100%.

Commercially-available materials suitable for preparing aqueous emulsions for use in this invention include products such as RHEOMIX® 790 ex Feb MBT. Such materials typically have solids contents of 30% or more and have to be diluted to make a composition for use in this invention.

The emulsions are added to a cementitious mix at a rate of from 0.1 - 2.0%, preferably from 0.5 - 1.5% by weight emulsion by weight of cement.

The hardened cementitious product containing the emulsion as admixture has a waterproofing performance that is noticeably superior to anything currently available.

The invention is further described by reference to the following non-limiting example.

The materials used are as follows: A. commercially-available aluminium stearate.

B. RHEOMIX® 790 emulsion, applied by spraying, according to manufacturer's instructions.

C. RHEOMIX® 790, diluted by adding 9 parts of water to 1 part of emulsion (to give a material according to preferment 1 above), and added as an admixture to the mix.

The test material is Lancaster stone, an architectural cast stone. All of A,B and C are tried on the stone, A and C being added to samples of the mix used to make the stone and B being applied to a sample of the hardened stone by spraying. The actual quantity of B is not precisely known, but it is sprayed according to the manufacturer's instructions, at a rate of about 5m2/L. The stone samples are then tested according to a number of recognised British Standards. The results are as follows: (a) Capillary absorption test (BS 1217). The maximum allowable is 1.0mg/mm2.

A B C dosage (% by weight 1.8 NA 1.1 on cement) capillary 0.13 4.0 0.18 absorption (mg/mm2) It can be seen that the performance according to the invention (C) is equivalent to that of the stearate (A), considering the lower quantity used, and much superior to that of the surface-applied siloxane B. (b) ISAT (Initial surface absorption) test. A maximum of 0.25ml/M2/10 min. according to BS 1881, and 0.10ml/M2/60 min according to BS 1217 are allowed. (c) The same stone and the same admixtures in the same dosages were used. The results are as follows: A B C ISAT (10 min) 0.1 1 0.10 0 ISAT (60 min) 0.40 0.03 0 In this case, the stone according to the invention was superior to the stones which used stearate and sprayed siloxane.

Claims

MBG-0463 7 Claims: 1. A method of conferring water impermeability on a hardened cementitious composition which is formed from a fluid cementitious mix, by the addition to the mix of an aqueous emulsion of organosilicon material, which material comprises from 0.25-4.5% by weight of the emulsion of an alkoxysilane and from 0.1-2.0% of an alkoxysiloxane. 2. A method according to claim 1 in which the emulsion is one which contains

1. 0.25 to 2.5% by weight of an alkoxysilane of the general formula R1 -Si(OR2)3 wherein Ri is an alkyl group with 3 to 12 carbon atoms; and R2 is a methyl or ethyl group;

2. 0.2 to 2% by weight of an alkoxysiloxane of the general formula Ra3-Si(OR2)b Q4-(a+b 2 wherein R3 is an alkyl group with 1 to 6 carbon atoms, a is 0.8 to 1.2 and b is 0.2 to 1.2; and 3. water to 100%.

3. A method according to claim 1 , in which the emulsion contains a) 0.5 to 4.5% by weight of an alkoxysilane of the general formula R'-Si-(OR2)3 wherein R1 is an alkyl group with 1 to 16 carbon atoms, and R2 is an alkyl group with 1 to 4 carbon atoms, b) 4.5 to 0.5% by weight of a mixture consisting of a bl) silane of the general formula R3-Si-(OR2)3 wherein R2 has the meaning already given, and R3 is an aminoalkyl group with 1 to 6 carbon atoms or a group of the general formula H2 N-(CH2)x R4 -(CH2)y-, in which R4 represents an oxygen, sulphur, -NH- or -NH-CH2-CH2- NH group and x>2 and y>2; or a group of the general formula (R20)3 Si-(CH2)X-NH-(CH2)X-, MBG-0463 wherein R and x are defined as above, n is a whole number from 1 to 5, and b2) is a polysiloxane of the general formula wherein R5 is a methyl or phenyl group, with the proviso that at least 90% of the R5 groups are methyl groups, and m=20 to 250, the ratio of bl to b2 being such that more than 1 and up to 3 OR2 groups of compound bl correspond to one SiOH group of compound b2, c) 0.05 to 1% by weight of an O/W emulsifier or emulsifier mixture; and MBG-0463 10 d) water to 100%. A method according to any one of claims 1-3, in which some of the water is replaced by from 0.001-0.5% by weight of an emulsifier, 0.001% by weight of filler with an effective surface area of at least 40M /g. A waterproof hardened cementitious composition comprising internally an alkoxysilane and an alkoxysiloxane which had been added to a cementitious mix from which the hardened composition was formed as an admixture by a method according to any one of claims 1-

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