DE102006009840A1 - Additive building material mixtures with micro full particles - Google Patents

Abstract

The present invention relates to the use of compact polymeric microparticles in hydraulically setting building material mixtures to improve their resistance to frost and freeze-thaw cycles.

Description

The The present invention relates to the use of polymeric microparticles in hydraulically setting building material mixtures to improve their Frost or freeze-thaw resistance.

concrete as an important building material is defined according to DIN 1045 (07/1988) as artificial Stone made from a mixture of cement, concrete aggregate and water, possibly also with concrete admixtures and concrete admixtures, by hardening arises. Concrete is u.a. divided into strength groups (BI-BII) and Strength classes (B5-B55). When admixing gas or foam forming Substances are aerated concrete or foam concrete (Römpp Lexikon, 10.Aufl., 1996, Georg Thieme Verlag).

Of the Concrete has two time-dependent Properties. First, learns he dehydration by a decrease in volume, as shrinking referred to as. The biggest part however, the water is bound as water of crystallization. Concrete dries not, it binds off, that is, the first low-viscosity cement paste (cement and Water) stiffens, solidifies and eventually solidifies, depending on the time and the course of the chemical-mineralogical reaction of the cement with the Water, hydration. Due to the water binding capacity of the Cements, the concrete, in contrast to quicklime, also under Harden water and stay firm. Second, concrete deforms under load, the like called creep.

Of the Freeze-thaw change refers to the climatic change of temperatures around the freezing point of water. Especially with mineral bound Building materials like concrete, the frost-thaw change is a damaging mechanism. These Materials have a porous, capillary structure and are not waterproof. Will one, with Water soaked structure Temperatures below 0 ° C exposed, the water freezes in the pores. By the density anomaly of water, the ice now expands. This leads to a damage of the building material. The very fine pores are due to surface effects to a lowering of the freezing point. In micropores water freezes only below -17 ° C. That I by frost-thaw change, the material itself expands and contracts, it comes in addition to a capillary pumping effect, the water absorption, and thus indirectly the injury further increases. For the damage Thus, the number of freeze-thaw changes is crucial.

For the resistance the concrete against frost and freeze-thaw cycles with simultaneous action of Taumitteln are the tightness of his structure, a certain strength the matrix and the presence of a specific pore structure prevail. The structure of a cement-bound concrete is characterized by capillary pores (radius: 2 μm-2 mm) or gel pores (Radius: 2-50 nm) crossed. Pore water contained in it differs in its state form depending on the pore diameter. While Water in the capillary pores maintains its ordinary properties, classified one in the gel pores after condensed water (mesopores: 50 nm) and adsorptively bound surface water (Micropores: 2 nm), the freezing points, for example, can be far below -50 ° C. [M.J. Setzer, Interaction of water with hardened cement paste, "Ceramic Transactions" 16 (1991) 415-39]. This has the consequence that even at deep cooling of the concrete part pore water remains unfrozen (metastable water). At the same temperature but the vapor pressure is over Ice less than the over Water. As ice and metastable water simultaneously side by side be present, a vapor pressure gradient, which leads to a diffusion of the still liquid Water leads to ice and its ice formation, causing a drainage the smaller or an ice accumulation takes place in the larger pores. These Water redistribution due to cooling takes place in every porous system and is decisive for the type of pore distribution dependent.

The artificial introduction of microfine air pores in the concrete thus produces in the first place so-called relaxation rooms for expanding Ice and ice water. In these pores can be freezing pore water expand or internal pressure and tension of ice and ice water catch, without causing microcracks and thus frost damage to the concrete comes. The principal mode of action of such air pore systems is in connection with the mechanism of frost damage of concrete in a variety of overviews [Schulson, Erland M. (1998) Ice damage to concrete. CRREL Special Report 98-6; S.Chatterji, Freezing of air-entrained cement-based materials and specific actions of air-entraining agents, "Cement & Concrete Composites" 25 (2003) 759-65; G.W.Scherer, J.Chen & J.Valenza, Methods for protecting concrete from freeze damage, US Patent 6,485,560 B1 (2002); M. Pigeon, B.Zuber & J.Marchand, Freeze / thaw resistance, "Advanced Concrete Technology "2 (2003) 11 / 1-11 / 17; B. Erlin & B. Mather, A new process by which cyclic freezing can damage concrete - the Erlin / Mather effect, "Cement & Concrete Research" 35 (2005) 1407-11].

A prerequisite for an improved resistance of the concrete during frost and thaw changes is that the distance of each point in the cement stone from the next artificial air pore does not exceed a certain value. This distance is also known as the distance factor or "Powers spacing factor" [TCPowers, The air requirement of frost-resistant concrete, "Proceedings of the Highway Research Board" 29 (1949) 184-202]. Laboratory tests have shown that exceeding the critical "Power spacing factor" of 500 μm leads to damage to the concrete during frost and thaw cycles. Therefore, in order to achieve this with limited air pore content, the diameter of the artificially introduced air pores must be less than 200-300 μm [K.Snyder, K. Natesaiyer & K.Hover, The Static and Statistical Properties of Entrained Air voids in Concrete: A mathematical basis for air void systems characterization) "Materials Science of Concrete" VI (2001) 129-214].

The Formation of an artificial Air pore system hangs decisively from the composition and the grain form of the aggregates, the Type and quantity of cement, concrete consistency, used Mixers, mixing time, temperature, but also of the type and Amount of air entraining agent. In consideration of corresponding Manufacturing rules can control their influences, however There may be a variety of unwanted impairments come, which ultimately leads to that the desired Air content in concrete exceeds or below and thus the strength or the Frost resistance of the concrete negatively affected.

Such artificial Air pores can not be dosed directly, but by the addition of so-called air entraining agents is registered by the mixing Air stabilized [L.Du & K.J.Folliard, Mechanism of air entrainment in concrete "Cement & Concrete Research" 35 (2005) 1463-71]. conventional Air-entraining agents are mostly surfactant-like in structure and break those introduced by mixing Air to small air bubbles with a diameter as possible less than 300 μm and stabilize them in the wet concrete structure. One differentiates thereby between two types.

Of the a type_ e.g. Sodium oleate, the sodium salt of abietic acid or Vinsol resin, an extract of pine roots - reacts with the calcium hydroxide the pore solution in cement paste and drops as insoluble Calcium salt. These hydrophobic salts reduce the surface tension of water and collect at the interface between cement grain, air and water. They stablilize the microbubbles and are therefore found in the hardening Concrete on the surfaces this air pore again.

Of the other type_- e.g. Sodium lauryl sulfate (SDS) or sodium dodecylphenylsulfonate - forms against it soluble with calcium hydroxide Calcium salts, but show an abnormal solution behavior. Under a certain critical temperature, these surfactants show a very low solubility, above this temperature, they are very soluble. By a preferred Accumulation at the air-water interface also reduces it the surface tension, thus stabilize the microbubbles and are preferred on the surfaces this air pores in the cured Find concrete again.

at the use of these air entraining agents according to the prior art a multitude of problems arise [L.Du & K.J. Folliard, Mechanism of air entrainment in concrete "Cement & Concrete Research" 35 (2005) 1463-71]. For example, longer mixing times, different mixer speeds, changed dosing processes cause transport concrete that the stabilized air (in the air pores) expelled again becomes.

The promotion of concretes with extended Transport times, poor temperature control and different pumping and conveyors, as well the introduction of these concretes along with changed Post-processing, jerky behavior and temperature conditions can significantly change a previously set air pore content. That can in the worst case, a concrete mean the required Limit values of a certain exposure class are no longer met and has become unusable [EN 206-1 (2000), Concrete - Part 1: Secification, performance, production and conformity].

Of the Content of fine materials in concrete (e.g., cement with different Alkaline content, additives such as fly ash, silica fume, or color additives) affects the Air entrainment also. Also can interact with defoaming flow agents occur, which thus expel air pores, but also in addition uncontrolled introduce can.

A relatively new way to improve the frost and freeze-thaw resistance is to achieve the air content by blending or metering polymeric microparticles (hollow microspheres) [H.Summer, A new method of making concrete resistant to frost and de-icing salts, "Concrete Plant & Precast Technology" 9 (1978) 476-84]. Since the microparticles usually have particle sizes smaller than 100 μm, they can also be distributed finer and more uniformly than artificially introduced air pores in the concrete structure. As a result, even small amounts are sufficient for a sufficient resistance of the concrete against freezing and thawing. The use of such polymeric microparticles to improve the frost and freeze-thaw resistance of concrete is already known according to the prior art [cf. DE 2229094 A1 . US 4,057,526 B1 . US 4,082,562 B1 . DE 3026719 A1 ]. The microparticles described therein are characterized in particular by the fact that they have a cavity which is smaller than 200 microns (diameter) and this hollow core consists of air (or a gaseous substance). This also includes porous microparticles of the 100 μm scale, which can have a multiple of smaller cavities and / or pores.

compact Polymeric microparticles have not been practically improved the frost and frost-thaw resistance are taken into account.

For the hollow microspheres However, relatively high dosages are needed to achieve values below the critical "Power spacing factor", which at least partly in the big one Particle diameter of> 100 microns is justified. This fact in combination with the high production costs, caused by the multi-stage manufacturing processes, had a negative impact on enforcement of these technologies in the market.

Of the The present invention was therefore based on the object, a means to improve the frost or thaw / thaw resistance for hydraulic provide bonding building material mixtures, which is also at relatively low dosages unfolds its full effectiveness and also easy and cheap to manufacture. Another task existed in it, the mechanical strength of the building material mixture by this Means not or not significantly affect.

It was now surprising found that too single or multi-stage compact polymeric microparticles to improve the frost or Freeze-thaw resistance for hydraulically setting Building material mixtures are suitable. Under single-stage microparticles is understood to mean a particle of homogeneous composition (without shell). That's even more surprising as by these polymeric microparticles no air in the construction mixture will be carried.

The The mode of action can be as follows be explained: the polymers of the invention Microparticles are distributed homogeneously in the mixture. A cavity between Microparticles and cured Building mixture, which may still be due to the shrinkage of the mixture during curing is enlarged, serves as an expansion location for freezing water. The even distribution these capillary active pores with an average distance from each other, the smaller than the "Power spacing factor ", then take care of the increase the frost or thaw / thaw resistance.

By the use of the polymer structures according to the invention the air intake into the building material mixture can be kept extremely low become. As a result, significantly improved compressive strengths of To achieve concrete.

Thus, strength classes can be achieved, which are otherwise adjustable only by a much lower water / cement value (W / Z value). However, low W / Z values may in turn severely limit the processability of the concrete. Higher compressive strengths are also and especially in so far of interest, as the required strength for the development of cement content in the concrete can be reduced, whereby the price per m ^{3 of} concrete can be significantly reduced.

The polymeric microparticles contain at least one monoethylenically unsaturated monomer. The microparticles may be mono- or multistage, whereby the comonomer composition of the individual stages may be different. Preference is given inter alia to nitriles of (meth) acrylic acid and other nitrogen-containing methacrylates, such as methacryloylamidoacetonitrile, 2-methacryloyloxyethylmethylcyanamide, cyanomethylmethacrylate; carbonyl-containing methacrylates, such as oxazolidinylethyl methacrylate, N- (methacryloyloxy) formamide, acetonyl methacrylate, N-methacryloylmorpholine, N-methacryloyl-2-pyrrolidinone; Glycol dimethacrylates such as 1,4-butanediol methacrylate, 2-butoxyethyl methacrylate, 2-ethoxyethoxymethyl methacrylate, 2-ethoxyethyl methacrylate, methacrylates of ether alcohols such as tetrahydrofurfuryl methacrylate, vinyloxyethoxyethyl methacrylate, methoxyethoxyethyl methacrylate, 1-butoxypropyl methacrylate, 1-methyl- (2-vinyloxy) ethyl methacrylate, cyclohexyloxymethyl methacrylate, methoxymethoxyethyl methacrylate Benzyloxymethylmethacrylate, furfurylmethacrylate, 2-butoxyethylmethacrylate, 2-ethoxyethoxymethylmethacrylate, 2-ethoxyethylmethacrylate, allyloxymethylmethacrylate, 1-ethoxybutylmethacrylate, methoxymethylmethacrylate, 1-ethoxyethylmethacrylate, ethoxymethylmethacrylate; Oxiranyl methacrylates such as 2,3-epoxybutyl methacrylate, 3,4-epoxybutyl methacrylate, glycidyl methacrylate; Phosphorus, boron and / or silicon-containing methacrylates, such as 2- (dimethylphosphato) propyl methacrylate, 2- (ethylene phosphite) propyl methacrylate, dimethyl phosphinomethyl methacrylate, dimethyl phosphonoethyl methacrylate, diethyl methacryloyl phosphonate, dipropyl methacryloyl phosphate; sulfur-containing methacrylates such as ethylsulfinylethyl methacrylate, 4-thiocyanatobutyl methacrylate, ethylsulfonylethyl methacrylate, thiocyanatomethyl methacrylate, methylsulfinylmethyl methacrylate, bis (methacryloyloxyethyl) sulfide;
Vinyl esters, such as vinyl acetate;
Styrene, substituted styrenes having an alkyl substituent in the side chain, such as * methylstyrene and * ethylstyrene, substituted styrenes having an alkyl substituent on the ring, such as vinyltoluene and p-methylstyrene;
Heterocyclic vinyl compounds, such as 2-vinylpyri din, 3-vinylpyridine, 2-methyl-5-vinylpyridine, 3 ethyl-4-vinylpyridine, 2,3-dimethyl-5-vinylpyridine, vinylpyrimidine, vinylpiperidine, 9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole, 1-vinylimidazole, 2-methyl-1-vinylimidazole, N vinylpyrrolidone, 2-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine, N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxolane, vinylfuran, vinylthiophene, vinylthiolane, vinylthiazoles and hydrogenated vinylthiazoles, vinyloxazoles and hydrogenated vinyloxazoles;
Vinyl and isoprenyl ethers;
Maleic acid derivatives, such as diesters of maleic acid, wherein the alcohol radicals have 1 to 9 carbon atoms, maleic anhydride, methylmaleic anhydride, maleimide, methylmaleimide;
Fumaric acid derivatives, such as diesters of fumaric acid, wherein the alcohol radicals have 1 to 9 carbon atoms;
α-olefins such as ethene, propene, n-butene, i-butene, n-pentene, i-pentene, n-hexene, i-hexene; Cyclohexene.

Furthermore was found to be enriched by appropriate monomers in addition to ionic repulsion also the steric repulsion the polymer structure can be realized. This leads to an additional Stabilization of the polymer structures in the dispersion and the construction mixture.

Radically polymerizable monomers having a molecular weight greater than 200 g / mol and carrying a hydrophilic radical can therefore also be used according to the invention. Particularly preferred are monomers which carry a polyethylene oxide block having two or more units of ethylene oxide. Preference is given to monomers from the group of the (meth) acrylic acid esters of methoxypolyethyleneglycol CH ₃ O (CH ₂ CH ₂ O) _n H, (where n ≥ 2), (meth) acrylates of an ethoxylated C 16 -C 18 fatty alcohol mixture (having 2 or more ethylene oxide units ), Methacrylic acid esters of 5-tert-octylphenoxypolyethoxyethanol (having 2 or more ethylene oxide units), nonylphenoxypolyethoxyethanol (having 2 or more ethylene oxide units) or mixtures thereof.

In addition, a or more monoethylenically unsaturated monomers having an acid group be included. Preference is given to acrylic acid, methacrylic acid, ethacrylic acid, α-chloroacrylic acid, α-cyanoacrylic acid, p-methylacrylic acid (crotonic acid), α-phenylacrylic acid, p-acryloyloxypropionic acid, sorbic acid, α-chlorosorbic acid, 2'-methylisocrotonic acid, cinnamic acid, p-chlorocinnamic acid, p- Stearic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid, maleic acid, fumaric acid, tricarboxyethylene and maleic anhydride, hydroxyl or amino group-containing esters of the above acids, preferably acrylic or methacrylic acid, such as. 2-hydroxyethyl acrylate, N, N-dimethylaminoethyl acrylate and the analogous derivatives of methacrylic acid, wherein acrylic acid as well methacrylic acid especially and acrylic acid about that are also preferred.

In addition to the monoethylenically unsaturated Monomer with an acid group For example, this polymer may also be further derived from the monoethylenically unsaturated Monomer with an acid group based on different comonomers. As comonomers are preferred ethylenically unsaturated sulfonic acid, ethylenically unsaturated phosphonic and acrylamides are preferred.

ethylenically unsaturated sulfonic are preferably aliphatic or aromatic vinylsulfonic acids or acrylic or methacrylic sulfonic acids. As aliphatic or aromatic vinylsulfonic acids are vinylsulfonic acid, allylsulfonic acid, 4-vinylbenzylsulfonic acid, vinyltoluene sulfonic acid and styrenesulfonic prefers. As acrylic or methacrylic sulfonic acids are sulfoethyl acrylate, Sulfoethyl methacrylate, sulfopropyl acrylate, sulfopropyl methacrylate, 2-hydroxy-3-methacryloxypropyl sulfonic acid and 2-acrylamide-2-methylpropanesulfonic acid is preferred.

ethylenically unsaturated phosphonic like vinylphosphonic acid, allylphosphonic, vinylbenzylphosphonic, Acrylamidoalkylphosphonsäuren, Acrylamidoalkyldiphosphonsäuren. Phonomonomethylated vinylamines, (meth) acrylicphosphonic acid derivatives.

Possible acrylamides are alkyl-substituted acrylamides or aminoalkyl-substituted Derivatives of acrylamide or methacrylamide, such as N-vinylamides, N-vinylformamides, N-vinylacetamides, N-vinyl-N-methylacetamides, N-vinyl-N-methylformamides, N-methylol (meth) acrylamide, Vinylpyrrolidone, N, N-dimethylpropylacrylamide, dimethylacrylamide or diethylacrylamide and the corresponding methacrylamide derivatives and acrylamide and methacrylamide, with acrylamide being preferred.

The chemical crosslinking is achieved by crosslinking agents well known to those skilled in the art. The crosslinkers may be present in each stage. Crosslinkers preferred according to the invention are polyacrylic or polymethacrylic acid esters which are obtained, for example, by the reaction of a polyol or ethoxylated polyol such as ethylene glycol, propylene glycol, trimethylolpropane, 1,6-hexanediolglycerol, pentaerythritol, polyethylene glycol or polypropylene glycol with acrylic acid or methacrylic acid. It is also possible to use polyols, amino alcohols and also their mono (meth) acrylic esters and monoallyl ethers. Furthermore, acrylic esters of Monoallylverbindungen the polyols and amino alcohols. Another group of crosslinkers is derived from the reaction of polyalkylene polyamines such as diethylene triamine and triethylene tetraamine methacrylic acid or methacrylic acid. Suitable crosslinkers are 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,3-butylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, ethylene glycol dimethacrylate, 1 isocyanorattriacrylat, 6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tripropylene glycol diacrylate, tetraethylene glycol diacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, dipentaerythritol pentaacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, Trimethyloltrimethacrylat, tris (2-hydroxyethyl), tris (2 -hydroxy) isocyanurate trimethacrylate, divinyl esters of polycarboxylic acids, diallyl esters of polycarboxylic acids, triallyl terephthalate, diallyl maleate, diallyl fumarate, hexamethylene bismaleimide, Trivinyl trimellitate, divinyl adipate, diallyl succinate, an ethylene glycol divinyl ether, cyclopentadiene diacrylate, triallylamine, tetraallylammonium halides, divinylbenzene, divinyl ether, N, N'-methylenebisacrylamide, N, N'-methylenebismethacrylamide, ethylene glycol dimethacrylate and trimethylolpropane triacrylate. Among these, preferred crosslinkers are N, N'-methylenebisacrylamide, N, N'-methylenebismethacrylamide, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate and triallylamine.

The Polymer structures of the invention may preferably are prepared by emulsion polymerization and preferably have an average particle size of 10 up to 5,000 nm; particularly preferred is an average particle size of 150 to 2,000 nm. Most preferred are average particle sizes of 200 to 1,000 nm.

The Determination of the average particle size is carried out, for example count a statistically significant amount of particles by transmission electron microscopy Recordings.

For the preparation of the polymer structures according to the invention, it is possible to use all regulators and initiators customary in the case of the emulsion polymerization. Examples of the latter are inorganic peroxides, organic peroxides or H ₂ O ₂ and mixtures thereof with optionally one or more reducing agents.

Everyone can according to the invention ionic or nonionic emulsifier during or after dispersion production be used.

While the water-filled, polymeric microparticles according to the invention preferably in the form of an aqueous Dispersion are used, it is within the scope of the present Invention readily possible, the water-filled Add microparticles directly as a solid of the building material mixture. For this purpose, the microparticles, for example - known to the expert Methods - coagulated and by usual Methods (e.g., filtration, centrifugation, sedimentation, and decanting) from the watery Dispersion isolated. The material obtained can be washed and afterwards dried.

The Polymer structures are the building material mixture in a preferred Amount of 0.01 to 5% by volume, in particular 0.1 to 0.5% by volume, added. The Building material mix - for Example in the form of concrete or mortar - this can be the usual hydraulically setting binder, e.g. Cement, lime, gypsum or anhydrite.

Claims (11)

Use of polymeric microparticles in hydraulically setting building material mixtures, characterized in that they are composed of ethylenically unsaturated monomers one or more stages. Use of polymeric microparticles according to claim 1, characterized in that the ethylenic unsaturated Monomers preferably from styrene, butadiene, vinyltoluene, ethylene, propylene, Vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, acrylamide, Methacrylamide, C1-C18 alkyl ester of acrylic or methacrylic acid or mixtures thereof. Use of polymeric microparticles according to claim 1, characterized in that this also contain crosslinkers. Use of polymeric microparticles according to claim 3, characterized in that the Venetzer preferably of ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, Allyl (meth) acrylate, divinylbenzene, diallylmaleinate, trimethylolpropane trimethacrylate, Glycerol dimethacrylate, glycerol trimethacrylate, pentaerythritol tetramethacrylate or their mixtures exist. Use of polymeric microparticles according to claim 1 or 3, characterized in that the microparticles as a dispersion be used. Use of polymeric microparticles according to claim 1 or 3, characterized in that the microparticles are spray-dried, coagulated or freeze-dried powder can be used. Use of polymeric microparticles according to claim 1, characterized in that the microparticles have a mean Particle size of 10 have up to 5000 nm. Use of polymeric microparticles according to claim 1, characterized in that the microparticles in an amount from 0.01 to 5 vol .-%, based on the building material mixture used become. Use of polymeric microparticles according to claim 1, characterized in that the microparticles in an amount from 0.1 to 0.5 vol .-%, based on the building material mixture used become. Use of polymers according to claim 1, characterized characterized in that the building material mixtures consist of a binder, selected from the group of cement, lime, gypsum and anhydrite. Use of polymeric microparticles according to claim 1, characterized in that it is in the building material mixtures for concrete or mortar is.