WO2010047408A2

WO2010047408A2 - Method for preventing wash-out of cementitious compositions

Info

Publication number: WO2010047408A2
Application number: PCT/JP2009/068306
Authority: WO
Inventors: Hideo Koyata; Miho Miyakawa; Tetsuya Ando
Original assignee: W.R. Grace & Co.-Conn; Denki Kagaku Kogyo Kabushiki Kaisha
Priority date: 2008-10-21
Filing date: 2009-10-20
Publication date: 2010-04-29
Also published as: JP5378752B2; WO2010047408A3; JP2011207625A

Abstract

A method for providing anti-washout property in a hydratable cementitious composition, wherein at least one polycationic polymer, at least one organic viscosity- modifying agent, and preferably an inorganic viscosity-modifying agent, are combined with a hydratable cementitious binder.

Description

DESCRIPTION

METHOD FOR PREVENTING WASH-OUT OF CEMENTITIOUS COMPOSITIONS

Technical Field

The present invention relates to a method for providing anti-washout properties to cementitious compositions such as concrete and cement masonry that are exposed to water, and, more particularly, the invention relates to the use of at least one polycationic polymer, at least one organic viscosity-modifying agent, and optionally at least one inorganic viscosity-modifying agent for preventing washout in severe situations such as underwater or underground installations.

Background Art

The concept of "washout" is used herein to refer to the loss of a hydratable cement or concrete when placed in an environment that is exposed to water, and this includes chemical leaching of minerals from the cement as well as physical removal of particles from the mixture.

The material that can be washed out from the fresh cement or concrete composition includes the hydratable cementitious binder system, namely, the Portland cement and any pozzolanic powders, such as fly ash, granulated blast furnace slag, silica, or other pozzolans commonly used to supplement the Portland cement. The material washed out may also include fine aggregate material (e.g., sand) in the case of mortars and concretes that are exposed to water.

Washout can occur where the cementitious composition is subjected to severe water flow, such as in underwater or underground placements. In such placement situations, a concrete is typically placed by pumping it in slurry form to the point of placement. For severe applications, a viscosity-modifying agent such as cellulose ether, a natural gum, or a synthetic thickener can be used. For less severe conditions, an organic viscosity-modifying agent can be used for preventing washout. However, for severe placements, such as underwater installations, viscosity-modifying polymers can not be used because such materials increase the viscosity of the concrete to the point at which it is not capable of being pumped easily or at all. Thus, a novel method for providing anti-washout of hydratable cementitious composition is needed.

Summary of the Invention In surmounting the difficulties of the prior art, the present inventors have discovered that the use of at least one poly-cationic polymer and at least one organic viscosity-modifying agent, such as a heteropolysaccharide gum, provides an excellent anti-washout property in hydratable cementitious compositions without creating pumping difficulties Such properties are desirable when the cementitious composition is to be placed in environments where water exposure is severe Such severe placements otherwise tend to wash out the cement/concrete components and cause leaching of cement components and particle fines into the water

In preferred embodiments of the invention, an inorganic viscosity-modifying agent such as bentonite clay may be used to further enhance the anti-washout properties of the components mentioned above

An exemplary method of the invention for providing anti-washout property to a hydratable cementitious composition whereby material in the cementitious composition is not substantially lost when exposed to water, thus comprises combining with a hydratable cementitious binder (a) at least one polycationic polymer containing a plurality of nitrogen-containing moieties selected from the group consisting of quaternary amines and tertiary amines, said at least one polycationic polymer present in the amount of 0 01 to 1 00 percent based on dry weight of said cementitious binder, (b) at least one organic viscosity-modifying agent selected from the group consisting of (i) polysaccharides (e g , cellulose ethers, starch ethers), (ii) heteropolysaccharide gums (e g , diutan, welan), (iii) synthetic water soluble polymers (e g , poly-acrylamide and its derivatives, polyethylene oxide and its copolymers, water soluble polyurethanes, and hydrophobically modified associative thickeners), the amount of said at least one organic viscosity-modifying agent being 0 005 to 0 5 percent based on dry weight of said cementitious binder, and (c) an inorganic viscosity-modifying agent operative to swell upon exposure to water, the amount of said inorganic viscosity-modifying agent being 0 to 5 0% based on dry weight of said cementitious binder

In further preferred embodiments, a "polycarboxylate" polymer, one preferably having polyoxyalkylene sidechains operative to disperse cement particles, can further enhance the rheological properties of the cement or concrete

While poly-heterosaccharide gums have been used before in concrete, these alone have not been found to provide sufficient anti-washout properties in severe applications (e g , underwater), nor is the anti-washout property sufficiently enhanced when poly-heterosaccharide gums are mixed with polycarboxylate cement dispersants which can be used for reducing the amount of water needed to mix the cement or concrete composition However, the present inventors surprisingly discovered that the addition of a poly-cationic polymer, one containing nitrogen, provided a significant improvement in anti-washout property compared to the hetero-polysaccharide gum used alone

Furthermore, the inventors discovered that the addition of bentonite clay (an inorganic viscosity-modifying agent) further enhanced the anti-washout property The afore-mentioned components may be combined separately or together into the hydratable cementitious composition to be treated Preferably, the hetero- polysaccharide and bentonite-type clay can be added as a dry powder additive, while the poly-cationic polymer and polycarboxylate polymer can be added in liquid form Separate addition is preferred because the bentonite-type clay might otherwise absorb one or more of the liquid components (e g , polycarboxylate polymer)

The present invention provides for cementitious structures formed using the aforementioned method, wherein components (a) and (b), preferably also component

(c), are combined with the hydratable cementitious composition Preferably, the structure is formed under water and is surrounded by water and hardens without substantial loss of material due to chemical leaching or particle washout

The present invention also provides for a novel admixture for addition to the hydratable cementitious composition, comprising the (a) at least one polycationic polymer containing a plurality of nitrogen-containing moieties selected from the group consisting of quaternary amines and tertiary amines, said at least one polycationic polymer present in the amount of 0 01 to 1 00 percent based on dry weight of said cementitious binder, (b) at least one organic viscosity-modifying agent selected from the group consisting of (i) polysaccharides (e g , cellulose ethers, starch ethers), (ii) heteropolysaccharide gums (e g , diutan, welan), (iii) synthetic water soluble polymers (e g , poly-acrylamide and its derivatives, polyethylene oxide and its copolymers, water soluble polyurethanes, and hydrophobically modified associative thickeners), the amount of said at least one organic viscosity-modifying agent being 0 005 to 0 5 percent based on dry weight of said cementitious binder, and (c) an inorganic viscosity-modifying agent operative to swell upon exposure to water, the amount of said inorganic viscosity-modifying agent being 0 to 5 0% based on dry weight of said cementitious binder

Further advantages and features of the invention may be described in further detail hereinafter Detailed Description of Exemplary Embodiments

The term "hydratable cementitious compositions" as used herein refers to compositions which harden or cure upon addition of water Such compositions are mixtures composed of a hydratable cementitious binder (usually, but not exclusively) comprising Portland cement, which may be supplemented by limestone, hydrated lime, fly ash, blast furnace slag, silica fume or other materials (some of the foregoing being commonly referred to as "pozzolans") and water Cement mortars are pastes additionally including fine aggregate (e g , sand), and concretes are mortars additionally including coarse aggregate (e g , crushed gravel, stones) "Cementitious" compositions of the invention thus refer to and include all of the foregoing For example, a cementitious composition may be formed by mixing required amounts of certain materials, e g , hydratable cementitious binder (cement with or without pozzolans), water, and fine and/or coarse aggregate, as may be desired, optionally with fibers (e g , steel, synthetic polymer, or combination of such fiber materials) which are sometimes used to prevent shrinkage cracking and/or to reinforce concrete The present invention provides superior anti-washout property to hydratable cementitious materials, especially in severe applications (e g , underwater, underground) wherein the cementitious binder, pozzolans, and fines are susceptible to be washed out and/or leached out by water in the environment

As set forth in the summary of the invention, the present invention involves the use of (a) at least one poly-cationic polymer, and this is preferably a nitrogen- containing polymer having multiple cationic functionality, and (b) at least one organic viscosity-modifying agent, and this is preferably a polysaccharide

The poly-cationic polymer of component (a) is selected from poly-amines, more preferably, poly-quaternary amine or poly-tertiary amine having a high cationic density For example, condensation polymer of epichlorohydrine and dimethylamine

(EPI-DMA), poly-diallyldimethylammonium chloride (DADMAC), condensation product of guanidine, cyano ammonium chloride, formaldehyde (DICY), and variations of the above mentioned polymers may be favorably used for the purpose. Description of the types of cationic polymers can be found in the US Patent application publication US 2007/0287794. The chemical structure of a preferred poly- cationic polymer, EPI-DMA, is shown below:

The organic viscosity-modifying agent of component (b) may be selected from natural or synthetic high molecular weight or associative polymers. This can be selected from cellulose ethers, poly-acrylamide or modified poly-acrylamides, HEUR thickener, polyvinyl alcohol, polyethylene glycol, polysaccharide gum and any other organic polymer that increases viscosity of water. Preferably, the organic viscosity- modifying agent is selected from polysaccharide gums such as welan gum, diutan gum, guar gum, arabic gum, gellan gum, diutan gum, rhamsan gum and xanthan gum. These heteropolysaccharides are described in the US patent application publication US 2006/0166837. The structure of a heteropolysaccharides is shown below:

As a preferable example, the structure of diutan gum is shown below:

In addition to the above (a) poly-cationic polymer and (b) organic viscosity- modifying agent, further exemplary methods and compositions of the invention may further include, as component (c), an inorganic viscosity-modifying agent. Inclusion of this additional component is preferred because it can enhance the anti-washout property. Exemplary inorganic viscosity-modifying agents (component (c)) of the invention therefore further include, along with components (a) and (b), any clay having the ability to swell upon exposure to water. A montmorillonite-type clay such as bentonite can be preferably used as the additional component (c) in the present invention.

Preferred bentonite clays contain sodium ions and calcium ions in the structure.

Japanese patent application Kokai HEI 6 -183799 discloses such bentonite clay for reducing sludge from manufacturing concrete products. The clay minerals described in the Japanese patent application Kokai HEI 6 - 183799 can also be applied to the present invention for the anti-washout enhancing purposes disclosed herein.

In still further exemplary embodiments of the invention, a polycarboxylate polymer operative to disperse cement can be employed. The uses of polycarboxylate polymers for dispersing cement are well known. A preferred polycarboxylate polymer has a comb structure with pendant polyoxyalkylene groups and an anionic backbone. The anionic group is typically carboxylic acid, but other ionic groups or latent acidic groups may also be found on the polymer backbone The polyoxyalkylene pendant group is typically polyethylene glycol with molecular weight range from 400 to 5,000 Polypropylene glycol groups may also be used to some extent, and the polycarboxylate polymer may have longer or shorter pendant groups as desired The chemical bond between the backbone and the pendant groups are typically achieved using an alkyl ether or ester linkage, although it is also known to employ amide, imide, and/or other linkage groups for this purpose

Other than polyoxyalkylene pendant groups, such as short alkyl (i e , having less than eight carbons - C₈), alkanol and/or alkylaryl groups may occasionally be incorporated into the polymer structure to provide certain attributes to the polymer such as adsorption capability, surface activity, and hydrodynamic radius

The use of an optional polycarboxylate polymer for cement dispersing purposes can provide enhanced fluidity to the concrete as well as enhanced anti- washout property The preferable amounts of the anti-washout admixture of the present invention are 0 01 - 1 wt% for (a) the poly-cationic polymer, 0 005 - 0 5 wt% for (b) organic viscosity-modifying agent, and 0 - 5 wt% for (c) the inorganic viscosity-modifying agent If the inorganic viscosity-modifying agent is used, the lowest amount would be 0 05 -5 wt% based on weight of cementitious binder The above-mentioned components can be combined together to provide a single concrete admixture, or, more preferably, added separately to the cementitious composition being treated For example, the poly-cationic polymer and optional (but preferred) polycarboxylate polymer (cement dispersant) can be added in liquid form, preferably together, and possibly combined with the other known concrete admixture components Such admixture components might include an accelerator, retarder, strength enhancer, air entrainer, air defoamer or air control agent, or combination thereof, while the organic viscosity-modifying agent and inorganic viscosity- modifying agent can be added in combination in the form of a dry powder additive, along with other additives that are typically incorporated into a cement or concrete mix in dry form, such as silica fume, fly ash, limestone powders, fibers, and others

While the invention is described herein using a limited number of embodiments, these specific embodiments are not intended to limit the scope of the invention as otherwise described and claimed herein Modification and variations from the described embodiments exist More specifically, the following examples are given as a specific illustration of embodiments of the claimed invention It should be understood that the invention is not limited to the specific details set forth in the examples All parts and percentages in the examples, as well as in the remainder of the specification, are by percentage weight unless otherwise specified

Further, any range of numbers recited in the specification or claims, such as that representing a particular set of properties, units of measure, conditions, physical states or percentages, is intended to literally incorporate expressly herein by reference or otherwise, any number falling within such range, including any subset of numbers within any range so recited For example, whenever a numerical range with a lower limit, RL, and an upper limit RU, is disclosed, any number R falling within the range is specifically disclosed In particular, the following numbers R within the range are specifically disclosed R = RL + k*(RU -RL), where k is a variable ranging from 1% to 100% with a 1% increment, e g , k is 1%, 2%, 3%, 4%, 5% 50%, 51%, 52%, 95%, 96%, 97%, 98%, 99%, or 100% Moreover, any numerical range represented by any two values of R, as calculated above, is also specifically disclosed Example 1

A concrete mix was made using a concrete mix design and procedure for testing the anti-washout property of water-submerged sample in accordance with the Japan Society of Civil Engineers standard (JSCE-D 104-2007)

As indicated below, the admixture components were dosed according to a weight percentage (%) based on weight of cementitious binder Measurements in accordance with JSCE-D 104-2007 were made regarding the slump flow, air content, amount of suspended solids, pH, setting time and 24-hour compressive strength Table 1 below indicates the concrete mix design employed

Table 1: Concrete Mix Design:

Table 2 shows the admixture compositions employed in the concrete examples Table 2: Anti-washout admixture composition

*) C-I Dimethylamine Epichlorohydrine condensate polymer, available from

Yokkaichi Gosei, Japan under "CatioMaster PD-7" tradename C-2 Diallyl dimethyl ammonium chloride polymer, available from Nittobo, Japan, under "PAS

H-IL" brandname

**) Organic viscosity- modifying agent heteropolysacchride gum (Diutan gum from CPKelco)

***) Inorganic viscosity-modifying agent Bentonite (available from Hojun under brandname "Super Clay")

The concrete samples containing the admixtures were then tested for anti- washout properties, and the results are included in Table 3 below

Table 3: Testing Result

As shown in Table 3, the test results provided by the admixtures and method of the present invention indicated that a marked reduction of suspended solids in the cementitious composition was obtained. It is also notable that the admixture of the present invention reduces the pH value of the water, indicating the underwater concrete material release less material component into the water. The example also confirms that the present invention does not show any negative impact on concrete performance such as set time, strength and durability.

The principles, preferred embodiments, and modes of operation of the present invention have been described in the foregoing specification. The invention which is intended to be protected herein, however, is not to be construed as limited to the particular forms disclosed, since these are to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art, without departing from the spirit of the invention.

Claims

1. A method for providing anti-washout property in a hydratable cementitious composition whereby material in the cementitious composition is not substantially lost when exposed to water, comprising combining with a hydratable cementitious binder

(a) at least one polycationic polymer containing a plurality of nitrogen- containing moieties selected from the group consisting of quaternary amines and tertiary amines, said at least one polycationic polymer present in the amount of 0 01 to 1 00 percent based on dry weight of said cementitious binder, (b) at least one organic viscosity-modifying agent selected from the group consisting of (i) polysaccharides, (ii) heteropolysaccharide gums, (iii) synthetic water soluble polymers, the amount of said at least one organic viscosity-modifying agent being 0 005 to 0 5 percent based on dry weight of said cementitious binder, and

(c) an inorganic viscosity-modifying agent operative to swell upon exposure to water, the amount of said inorganic viscosity-modifying agent being 0 to 5 0% based on dry weight of said cementitious binder

2 The method of claim 1 wherein, in said introducing step, said polycationic polymer is a poly-quaternary ammonium polymer

3 The method of claim 1 wherein, in said introducing step, said organic viscosity-modifying agent is a heteropolysaccharide selected from the group consisting of welan gum, diutan gum, guar gum, arabic gum, gellan gum, rhamsan gum, and xanthan gum

4 The method of claim 1 wherein, in said introducing step, said inorganic viscosity-modifying agent is bentonite clay, the amount of said bentonite being at least 0 05 to 5 0% based on dry weight of cementitious binder

5 The method of claim 1 further comprising introducing to said hydratable cementitious binder a polycarboxylate polymer characterized by having polyoxyalkylene pendant groups operative to dispersant said cement particles

6 The method of claim 5 wherein, in said introducing step, said polycationic polymer of component (a) and said polycarboxylate polymer are introduced to said hydratable cement binder in liquid forms, and said at least one organic viscosity-modifying agent of component (b) and said inorganic viscosity- modifying agent of component (c) are introduced to said hydratable cement binder as powders.

7. A cementitious structure obtained by the method of claim 1.