Cement dispersing polymers for high flow, high strength and selfcompacting concrete

[0005] This application claims the priority of European Patent Application No. 00 105 911.2, filed Mar. 22, 2000, the disclosure of which is incorporated herein by reference in its entirety.

[0006] The invention relates to water-soluble acrylic copolymers suitable as cement dispersing admixtures.

[0007] The quality of fresh concrete is determined by the ease and homogeneity with which it can be mixed, transported, compacted and finished. It can also be defined as the amount of internal work, necessary to achieve full compaction.

[0008] The Theological behavior of concrete is related to rheological terms such as plasticity and visco-elasticity of its cement paste.

[0009] Cement compositions, such as mortar or concrete, lose their flowability with the progression of time due to a fast stiffening effect caused by an early hydration reaction of cement and water. This loss of flow reduces its workability.

[0010] As the workability depends on the conditions of placement, the intended use will determine whether the concrete has the required workability.

[0011] Concrete from ready mix plants or mixed on job sites, used in civil engineering constructions, e.g. anchorage of big bridges, base plates or side walls and box culverts, in building structures such as heavy reinforced structures, concrete filling pipe structures or other complicated structures, demands to be fully compacted to achieve its required strength and durability. The existing and conventional method for compaction is by vibration of the freshly placed concrete.

[0012] A new production system for in situ-casted concrete is needed to improve significantly the cost situation as well as the health and safety aspects on the construction site.

[0013] Additionally, self compacting concrete leads to a higher productivity, shorter building times and to an improved labor environment.

[0014] Increased fluidity, defined e.g. as “flow-table spread”, “slump” and “slump-flow”, can be effected by using large dosages of water in the concrete, but it is well known that the resulting cement-based structure exhibits insufficient compactness due to excessive bleeding and segregation and consequently will have poor final compressive strength.

[0015] In order to avoid excess amount of water, flowing concrete can be produced by the addition of so called superplasticizers or high range water-reducing admixtures (HRWRs) like sulfonated melamine-formaldehyde polycondensates or naphthalene-formaldehyde polycondensates or ligninsulfonate based admixtures. All of these well known polymers are not capable of causing the treated cement compositions to retain high flowability over a sustained period of time (known as “slump life”) without imparting a significant delay in the initial set time and considerable retardation of early strengths. An additional disadvantage is the inconstant and very low flow rate of freshly prepared concrete containing high quantities (e.g. 500 to 700 kg/m³) of cement and up to 20% of silica fume and fly ash, which flow rate cannot be improved by the use of conventional HRWRs.

[0016] For heavy reinforced fresh precast concrete it is desired that the cementitious mixture has sufficient fluidity to flow through and around the reinforcement steel-structure to fill out the mold and level off at the top of the mold.

[0017] In the past ten years various polymer-admixtures based on so called polycarboxylic acid salts, e.g. copolymers of acrylic acid with acrylic esters of polyalkylene glycols have been proposed for imparting high water reduction, high flow and prolonged slump life to concrete, but most of them do not lead to self compacting concrete without causing a too long retardation of the setting time and the early-strength development.

[0018] Enhancing early, i.e. 1 day, compressive strengths, is of high importance in the precast and prestressed concrete industry, and chemical accelerators such as tertiary alkanolamines, alkali metal and alkaline earth metal thiocyanates, nitrites and halides are known in the art for this purpose and can be added separately to the fresh concrete.

[0019] Since calcium chloride and other inorganic salts can initiate corrosion of reinforcing steel embedded in hardened concrete, tertiary alkanolamines which show both, accelerating and corrosion inhibiting properties are the most recommendable chemical accelerators.

[0020] Unfortunately, tertiary amines are well known to act as powerful catalysts for the cleavage of esters and from this reason cannot be premixed with the acrylic ester polymers of the art and stored over longer periods thus causing strongly reduced shelf life of the blend.

[0021] In order to improve the stability of such admixtures, a deactivated form of alkanolamines was demanded which is reactivated in an alkaline environment.

[0022] The problem to be solved by the present invention is, that conventional cement dispersing polymers cannot be used as admixtures to produce simultaneously high flow- and high strength selfcompacting concrete.

[0023] Said problem could be solved with the introduction of a super high flow- or self compacting concrete, which is or contains a multipurpose polymer simultaneously acting 1) as a HRWR, 2) as set- and strength accelerator and 3) as corrosion inhibitor, these problems could be solved, particularly the need for vibration can be significantly reduced.

[0024] Hence, it is a general object of the invention to provide—as a result of extensive studies—acrylic copolymers, which can solve this problem.

[0025] The invention is based on modified acrylic polymers having a) a poly (oxyalkylene) chain and b) a tertiary alkanolamine group which both are connected to the backbone of the polymer by ester bonds. Said polymers are obtainable by aqueous radicalic copolymerization of acrylic polyalkyleneglycol esters- and -amides with an acrylic acid and an acrylic ester of a tertiary alkanolamine.

[0026] In particular it was found that the relationship between the molar ratio of the free carboxylate groups to the polyoxyethylene ester groups and the polyoxyethylene amide groups in the polymer as well as the length of the polyoxyethylene chain strictly determines the performance of the copolymer as a dispersing, water reducing and slump-keeping agent.

[0027] The accelerating and anticorrosive effect of tertiary alkanolamines in aqueous solutions is known for long time. The inventive polymers react in alkaline cementitious compositions and the alkanolamine group is released from the polymer which is partly adsorbed to the cement surface. Due in particular to their close proximity to the cement surface, the released alkanolamines prove a high set accelerating and shrinkage reducing effect.

[0028] Moreover, results suppose, that the polymers also are adsorbed on the reinforcing steel bars in the fresh concrete where they can act as corrosion inhibitors directly on the surface of the steel.

[0029] A water-soluble acrylic copolymer with cement dispersing, set-accelerating and anticorrosive properties to steel, as well as an admixture comprising an amount of from 5 to 95% of said water soluble acrylic copolymer, are described.

[0030] Said polymer is obtainable by copolymerization of an α,β-olefinic monocarboxylic acid or its salt shown by formula 1 given below, a second acrylic monomer shown by formula 2 given below, optionally a third acrylic monomer shown by formula 3 given below, a fourth acrylic monomer shown by formula 4 given below and optionally a fifth acrylic monomer given by formula 5,

[0031] such that the molar ratio of constituent monomer units 1, 2, 3, 4, 5 is

[0032] a:b:c:d:e=(0.1-0.9):(0.01-0.80):(0-0.80):(0.001-0.3):(0-0.5)

[0033] and

[0034] a:(b+c+d+e)=0.1:0.9 to 0.9:0.1,

[0035] whereby

[0036] a designates the molar concentration range of constituent monomers 1,

[0037] b designates the molar concentration range of constituent monomers 2,

[0038] c designates the molar concentration range of constituent monomers 3,

[0039] d designates the molar concentration range of constituent monomers 4,

[0040] e designates the molar concentration range of constituent monomers 5

[0041] said monomers having the structural formulas shown below:

[0042] wherein each R independently from each other represents a hydrogen atom or a methyl group,

[0043] R¹and R²independently from each other represent a C₁-C₄-alkyl, a hydroxyethyl (CH₂CH₂OH) group, an acetoxyethyl group (CH₂CH₂OCOCH₃₎group, hydroxy-isopropyl (CH₂—CHOH—CH₃) group, an acetoxy-isopropyl (CH2—CHOCOCH3) group, or R¹and R ²may together with the nitrogen atom to which they are bound, form a morpholine ring;

[0044] R³is a C₁-C₄-alkyl,

[0045] R⁴and R⁵independently represent an aliphatic, cycloaliphatic, araliphatic or aromatic or R⁴and R⁵may together with the nitrogen atom to which they are bond form a morpholine- or imidazole ring system,

[0046] M represents hydrogen, an alkali metal, an alkaline earth metal, an aluminum ion, an ammonium- or organic ammonium group, such as an ammonium group derived from alkylamines or alkanolamines, in particular amines comprising C₁to C₄alkyl and/or C₁to C₄alkanol groups,

[0047] x and y independently represent integers from 2-300.

[0048] In the solvent polymerization using an aqueous solvent, a water soluble polymerization initiator such as ammonium salts, alkali metal salts of a peroxy acid or hydrogen peroxide is used as the polymerization initiator.

[0049] Further, to control the molecular weight, a chain transfer agent such as alkali sulfite, hydrogensulfite, mercaptoethanol, thioglycolic acid or thioglycerol (3-mercapto-1,2-propanediol) may be used.

[0050] It is preferable that the inventive polymer has a number-average molecular weight of 1000 to 100000, still more preferably 1000 to 30000.

[0051] When the molecular weight is too large, the resulting copolymer will exhibit a poor dispersing effect, while, when it is too small, the resulting copolymer will exhibit not only poor dispersity but also a poor slump retaining effect. Moreover, a defined molar proportion of 1-5 to 1 of carboxylic-groups to methoxypolyalkyleneglykol ester side chains and methoxypolyalkyleneglycol amide side chains at the backbone of the copolymer is preferred.

[0052] The average molecular weight is determined by gel permeation chromatography using a set of defined polyalkyleneglycols as standard reference.

[0053] Following a further aspect of the present invention the inventive copolymers are employed for preparing a cement-dispersing, set accelerating admixture having shrinkage-reducing and anticorrosive properties to steel. Hence, further to the invention, said admixture preferably contains at least one defoaming and/or at least one air-controlling agent.

[0054] Still a further aspect of the present invention is a mortar, concrete, cement or cementitious binder containing the modified acrylic polymer according to the present invention in an amount of 0.01 to 10% by weight of the binder, said mortar or concrete having a unit content of binder composed of cement or a mixture of cement and latent hydraulic or inert microscopic powder of 150 to 800 kg/m³, preferably of 250 to 650 kg/m³.

[0055] In a preferred embodiment, the cement is Portland cement, white cement, high alumina cement, and cement blends wherein the latent hydraulic or inert microscopic powder is fly ash, slag, natural pozzolane, silica fume, burnt oil shale, metakaolin or calcium carbonate.

[0056] The inventive admixture can be used in liquid form, e.g. by addition of water, in powder form and can be added before, during or after the grinding operation of the cement or the cementitious binder.

[0057] In the following, some copolymers of the present invention and cement dispersing admixtures comprising such polymers, the method for producing the same and the cement containing composition of the present invention are explained in more detail with the following examples E1-E6 and comparative examples C1, C2,and C3. Moreover, for comparison, commercially available polymers C7, C8 and C9 are also used for the preparation and testing of flowing concrete (test example 1) and high-strength, self compacting concrete of low water-to-cement ratio (test examples 2 and 3).

[0058] In test examples 4-6 the corrosion inhibiting effect of the inventive polymers on mild steel and on reinforcing steel is demonstrated and compared to comparative examples.

[0059] However, it must be noted that all these examples are given for illustrative purposes only and are not supposed to limit the invention, as defined by the claims, appended hereto.

[0060] The following polyalkyleneglycol-based acrylic esters and -amides have been used in the examples described below (table 1):

[0061] Into a 2 liter-glass reactor, equipped with a stirrer, reflux condenser, N₂-inlet tube and automatic dosing mechanism, were placed 0.30 g of ferrous sulfate and 5 g of thioglycerol dissolved in 380 g water. The inside atmosphere of the flask was replaced with stirring by nitrogen gas and the solution heated to 60° C. Then simultaneously were added in 60 minutes a) an aqueous solution of 72 g (1 mol) of freshly distilled acrylic acid (monomer 1) 493 g (0.24 mol) of monomer 3-3, 82 g (0.04 mol) of monomer 3-4 and 6 g of 50%-sodium hydroxide in 180 g water, b) a solution of 15 g of 35%-hydrogen peroxide and c) 4 g ascorbic acid in 25 g water. After the completion of the addition, in course of which the temperature raised to 75° C., the reaction system was maintained at that temperature for 15 minutes. Finally, the mixture was cooled to 25° C. and 2 g of methoxy-polyoxyalkyleneamine of MW=2000 with a PO/EO mol. ratio of 29:6 were added. 35 g of 50%-sodium hydroxide were then added dropwise to adjust the pH-value to 5.0. Water was added to give a 40%-solution. A polymer of a number average molecular weight of M_n=9300 g/mol was obtained.

[0062] Into a 2 liter-glass reactor, equipped with a stirrer, reflux condenser, N₂-inlet tube and automatic dosing mechanism, were placed 0.30 g of ferrous sulfate and 5 g of thioglycerol dissolved in 380 g water. The inside atmosphere of the flask was replaced with stirring by nitrogen gas and the solution heated to 60° C. Then simultaneously were added in 60 minutes a) an aqueous solution of 72 g (1 mol) of freshly distilled acrylic acid (monomer 1), 493 g (0.24 mol) of monomer 3-3, 82 g (0.04 mol) of monomer 3-4, 15 g (0.05 mol) dimethylaminoethyl acrylate and 6 g of 50%-sodium hydroxide in 180 g water, b) a solution of 15 g of 35%-hydrogen peroxide and c) 4 g ascorbic acid in 25 g water. After the completion of the addition, in course of which the temperature raised to 75° C., the reaction system was maintained at that temperature for 15 minutes. Finally, the mixture was cooled to 25° C. and 2 g of methoxy-polyoxyalkyleneamine of MW=2000 with a PO/EO mol. ratio of 29:6 were added. 35 g of 50%-sodium hydroxide were then added dropwise to adjust the pH-value to 5.0. Water was added to give a 40%-solution. A polymer of a number average molecular weight of M_n=9900 g/mol was obtained.

[0063] Into a 2 liter-glass reactor, equipped with a stirrer, reflux condenser, N₂-inlet tube and automatic dosing mechanism, were placed 0.30 g of ferrous sulfate and 5 g of thioglycerol dissolved in 380 g water. The inside atmosphere of the flask was replaced with stirring by nitrogen gas and the solution heated to 60° C. Then simultaneously were added in 60 minutes a) an aqueous solution of 72 g (1 mol) of freshly distilled acrylic acid (monomer 1), 513.5 g (0.25 mol) of monomer 2-2, 50 g of polypropyleneglycol of MW 4000 and 6 g of 50%-sodium hydroxide in 180 g Water, b) a solution of 15 g of 35%-hydrogen peroxide and c) 4 g ascorbic acid in 25 g water.

[0064] After the completion of the addition, in course of which the temperature raised to 75° C., the reaction system was maintained at that temperature for 15 minutes. Finally, the mixture was cooled to 25° C. and 2 g of methoxy-polyoxyalkyleneamine of MW=2000 with a PO/EO mol. ratio of 29:6 were added. 35 g of 50%-sodium hydroxide were then added dropwise to adjust the pH-value to 5.0. Water was added to give a 40%-solution. A polymer of a number average molecular weight of M_n=10100 g/mol was obtained.

[0065] Into a 2 liter-glass reactor, equipped with a stirrer, reflux condenser, N₂-inlet tube and automatic dosing mechanism, were placed 0.30 g of ferrous sulfate and 5 g of thioglycerol dissolved in 380 g water. The inside atmosphere of the flask was replaced with stirring by nitrogen gas and the solution heated to 60° C. Then simultaneously were added in 60 minutes a) an aqueous solution of 72 g (1 mol) of freshly distilled acrylic acid (monomer 1), 513.5 g of monomer 2-2, 59 g of polypropyleneglycol of MW 4000, 2.15 g (0.015 mol) of dimethylaminoethyl acrylate and 6 g of 50%-sodium hydroxide in 200 g water, b) a solution of 15 g of 35%-hydrogen peroxide and c) 4 g ascorbic acid in 25 g water. After the completion of the addition, in course of which the temperature raised to 75° C., the reaction system was maintained at that temperature for 15 minutes. Finally, the mixture was cooled to 25° C. and 2 g of methoxy-polyoxyalkyleneamine of MW=2000 with a PO/EO mol. ratio of 29:6 were added. 35 g of 50%-sodium hydroxide were then added dropwise to adjust the pH-value to 5.0. Water was added to give a 40%-solution. A polymer of a number average molecular weight M_n=9900 g/mol was obtained.

[0066] Into a 2 liter-glass reactor, equipped with a stirrer, reflux condenser, N₂-inlet tube and automatic dosing mechanism, were placed 0.30 g of ferrous sulfate and 5 g of thioglycerol dissolved in 380 g water. The inside atmosphere of the flask was replaced with stirring by nitrogen gas and the solution heated to 60° C. Then simultaneously were added in 60 minutes a) an aqueous solution of 72 g (1 mol) of freshly distilled acrylic acid (monomer 1), 685 g (0.65 mol) of monomer 2-1, 47 g (0.085 mol) of monomer 3-1, and 6g of 50%-sodium hydroxide in 250 g water, b) a solution of 15 g of 35%-hydrogen peroxide and c) 4 g ascorbic acid in 25 g water. After the completion of the addition, in course of which the temperature raised to 75° C., the reaction system was maintained at that temperature for 15 minutes. Finally, the mixture was cooled to 25° C. and 2g of methoxy-polyoxyalkyleneamine of MW=2000 with a PO/EO mol. ratio of 29:6 were added. 35 g of 50%-sodium hydroxide were then added dropwise to adjust the pH-value to 5.0. Water was added to give a 40%-solution. A polymer of a number average molecular weight of M_n=11100 g/mol was obtained.

[0067] Into a 2 liter-glass reactor, equipped with a stirrer, reflux condenser, N₂-inlet tube and automatic dosing mechanism, were placed 0.30 g of ferrous sulfate and 5 g of thioglycerol dissolved in 380 g water. The inside atmosphere of the flask was replaced with stirring by nitrogen gas and the solution heated to 60° C. Then simultaneously were added in 60 minutes a) an aqueous solution of 72 g (1 mol) of freshly distilled acrylic acid (monomer 1), 685 g (0.65 mol) of monomer 2-1, 47 g (0.085 mol) of dimethylaminoethyl acrylate and 6 g of 50%-sodium hydroxide in 250 g water, b) a solution of 15 g of 35%-hydrogen peroxide and c) 4 g ascorbic acid in 25 g water. After the completion of the addition, in course of which the temperature raised to 75° C., the reaction system was maintained at that temperature for 15 minutes. Finally, the mixture was cooled to 25° C. and 2 g of methoxy-polyoxyalkyleneamine of MW=2000 with a PO/EO mol. ratio of 29:6 were added. 35 g of 50%-sodium hydroxide were then added dropwise to adjust the pH-value to 5.0. Water was added to give a 40%-solution. A polymer of a number average molecular weight of M_n=10700 g/mol was obtained.

[0068] Into a 2 liter-glass reactor, equipped with a stirrer, reflux condenser, N_2-inlet tube and automatic dosing mechanism, were placed 0.30 g of ferrous sulfate and 5 g of thioglycerol dissolved in 380 g water. The inside atmosphere of the flask was replaced with stirring by nitrogen gas and the solution heated to 60° C. Then simultaneously were added in 60 minutes a) an aqueous solution of 72 g (1 mol) of freshly distilled acrylic acid (monomer 1) 516 g (0.49 mol) of monomer 2-1, 95 g (0.09 mol) of monomer 3-2 and 6g of 50%-sodium hydroxide in 200 g Water, b) a solution of 15 g of 35%-hydrogen peroxide and c) 4 g ascorbic acid in 25 g water. After the completion of the addition, in course of which the temperature raised to 75° C., the reaction system was maintained at that temperature for 15 minutes. Finally, the mixture was cooled to 25° C. and 2 g of methoxy-polyoxyalkyleneamine of MW=2000 with a PO/EO mol. ratio of 29:6 were added. 35 g of 50%-sodium hydroxide were then added dropwise to adjust the pH-value to 5.0. Water was added to give a 40%-solution. A polymer of a number average molecular weight of M_n=10200 g/mol was obtained.

[0069] Into a 2 liter-glass reactor, equipped with a stirrer, reflux condenser, N₂-inlet tube and automatic dosing mechanism, were placed 0.30 g of ferrous sulfate and 5 g of thioglycerol dissolved in 380 g water. The inside atmosphere of the flask was replaced with stirring by nitrogen gas and the solution heated to 60° C. Then simultaneously were added in 60 minutes a) an aqueous solution of 72 g (1 mol) of freshly distilled acrylic acid (monomer 1), 516 g (0.49 mol) of monomer 2-1, 95 g (0.09 mol) of monomer 3-2 and 2.86 g (0.02mol) of dimethylaminoethyl acrylate in 200 g water, b) a solution of 15 g of 35%-hydrogen peroxide and c) 4 g ascorbic acid in 25 g water. After the completion of the addition, in course of which the temperature raised to 75° C., the reaction system was maintained at that temperature for 15 minutes. Finally, the mixture was cooled to 25° C. and 2 g of methoxy-polyoxyalkyleneamine of MW=2000 with a PO/EO mol. ratio of 29:6 were added. 35 g of 50%-sodium hydroxide were then added dropwise to adjust the pH-value to 5.0. Water was added to give a 40%-solution. A polymer of a number average molecular weight M_n=9700 g/mol was obtained.

[0070] Into a 2 liter-glass reactor, equipped with a stirrer, reflux condenser, N₂-inlet tube and automatic dosing mechanism, were placed 0.30 g of ferrous sulfate and 5 g of thioglycerol dissolved in 380 g water. The inside atmosphere of the flask was replaced with stirring by nitrogen gas and the solution heated to 60° C. Then simultaneously were added in 60 minutes a) an aqueous solution of 72 g (1 mol) of freshly distilled acrylic acid (monomer 1) 580 g (0.55 mol) of monomer 2-1, 28 g (0.12 mol) of N,N-dicyclohexyl acrylamide and 6 g of 50%-sodium hydroxide in 220 g water, b) a solution of 15 g of 35%-hydrogen peroxide and c) 4 g ascorbic acid in 25 g water. After the completion of the addition, in course of which the temperature raised to 75° C., the reaction system was maintained at that temperature for 15 minutes. Finally, the mixture was cooled to 25° C. and 2 g of methoxy-polyoxyalkyleneamine of MW=2000 with a PO/EO mol. ratio of 29:6 were added. 35 g of 50%-sodium hydroxide were then added dropwise to adjust the pH-value to 5.0. Water was added to give a 40%-solution. A polymer of a number average molecular weight of M_n=10300 g/mol was obtained.

[0071] Into a 2 liter-glass reactor, equipped with a stirrer, reflux condenser, N₂-inlet tube and automatic dosing mechanism, were placed 0.30 g of ferrous sulfate and 5 g of thioglycerol dissolved in 380 g water. The inside atmosphere of the flask was replaced with stirring by nitrogen gas and the solution heated to 60° C. Then simultaneously were added in 60 minutes, a) an aqueous solution of 72 g (1 mol) of freshly distilled acrylic acid (monomer 1), 580 g (0.55 mol) of monomer 2-1, 2.86 g (0.02 mol) of dimethylaminoethyl acrylate and 6g of 50%-sodium hydroxide in 220 g water, b) a solution of 15 g of 35%-hydrogen peroxide and c) 4 g ascorbic acid in 25 g water. After the completion of the addition, in course of which the temperature raised to 75° C., the reaction system was maintained at that temperature for 15 minutes. Finally, the mixture was cooled to 25° C. and 2 g of methoxy-polyoxyalkyleneamine of MW=2000 with a PO/EO mol. ratio of 29:6 were added. 35 g of 50%-sodium hydroxide were then added dropwise to adjust the pH-value to 5.0. Water was added to give a 40%-solution. A polymer of a number average molecular weight of M_n=9500 g/mol was obtained.

[0072] Into a 2 liter-glass reactor, equipped with a stirrer, reflux condenser, N₂-inlet tube and automatic dosing mechanism, were placed 0.30 g of ferrous sulfate and 5 g of thioglycerol dissolved in 380 g water. The inside atmosphere of the flask was replaced with stirring by nitrogen gas and the solution heated to 60° C.

[0073] Then simultaneously were added in 60 minutes a) an aqueous solution of 72 g (1 mol) of freshly distilled acrylic acid (monomer 1), 317 g (0.19 mol) of monomer 2-4,

[0074] 317 g (0.19 mol) of monomer 3-5 and 2.15 g of of dimethylaminoethyl acrylate in 200 g water,

[0075] b) a solution of 15 g of 35%-hydrogen peroxide and c) 4 g ascorbic acid in 25 g water. After the completion of the addition, in course of which the temperature raised to 75° C., the reaction system was maintained at that temperature for 15 minutes. Finally, the mixture was cooled to 25° C. and 2 g of methoxy-polyoxyalkyleneamine of MW=2000 with a PO/EO mol. ratio of 29:6 were added. 35 g of 50%-sodium hydroxide were then added dropwise to adjust the pH-value to 5.0. Water was added to give a 40%-solution. A polymer of a number average molecular weight M_n32 9900 g/mol was obtained.

[0076] SOKALAN PA 25 CL PN (BASF, Badische Anilin& Sodafabrik) a 50% aq. solution of a partially neutralized polyacrylic acid of weight-average molecular weight 4000 was used as a comparative dispersant for concrete.

[0077] Melment F-10 (Süddeutsche Kalkstickstoffwerke,Trostberg, BRD), a commercial dispersing agent for hydraulic cement compositions, is the sodium salt of a sulfonated melamine formaldehyde polycondensate of molecular weight of about 15,000.

[0078] MIGHTY-150(KAO Corp., Tokyo), a commercial dispersing agent for hydraulic cement masses, is the sodium salt of a sulfonated naphthalene-formaldehyde polycondensate of average molecular weight of about 5,000-6,000.

[0079] These examples were performed to demonstrate the improved fluidizing effects of the inventive polymers on fresh concrete and their accelerating action on the development of the early (1d) compressive strengths. The inventive polymers E1 to E5, were tested as fluidizers in flowing concrete (test-example 1) and as admixtures to improve the flowability and slump life of high -strength concrete of low water-to-cement ratio and high binder (cement+silica-fume) content (test example 2).

[0080] Those comparative polymers (C1 to C8) described above were also tested and compared in this context.

[0081] Flowing Concrete

[0082] Use of inventive polymers and comparative polymers for flowing concrete.

[0083] The consistency of freshly prepared concrete i.e. the mobility or viscosity , is the most important characteristic of workability. For measuring the consistency of concrete a “flow table spread” according to DIN 1048, part1 is used in industry.

[0084] Sometimes the “slump test” according to ASTM C143 is additionally used.

[0085] For purposes of this experiment the flow table spread was determined by placing concrete in an iron form on a two-part table (70×70 cm). By removing the form, a concrete body having a truncated cone shape is prepared. Then, the are of the table is lifted on one side for 4 cm, and allowed to fall. This procedure is carried out 15 times, and the concrete spreads. The average diameter of the formed cake corresponds to the flow table spread.

[0086] For the slump test, three layers of concrete are put into a mold having a shape of a truncated cone and having certain dimensions, and compressed with 25 pushes of an iron bar. At the top, the concrete is stripped off evenly, then, the form is vertically removed. The concrete body will sink in by itself. The slump is measured by determining the vertical difference between the top of the mold and the displaced original center of the top surface of the test sample.

[0087] In order to compare the obtained test results and to bring them into a relation with the consistency, the freshly prepared concrete (see DIN 18555, Part2) may be divided into consistency ranges:

[0088] Fluidizers are used when specific construction applications are necessary. Flowing concrete is used when high inserting rates (e.g., from 50 to 150 m³/hour) are required, or when the form and reinforcement of a construction part do not allow a compacting of the concrete by vibration.

[0089] Concretes having K2 or K3 consistencies may be prepared from a concrete of K1 consistency by adding fluidizers (also designated as superplasticizers) when increased mechanical strength at an equal remaining workability shall be obtained.

[0090] For a freshly prepared concrete, the fluidizing effect is dependent on the dosage of the superplasticizer. Usually, from 0.2 to 1.5% solid matter quantities (in dissolved form), referred to the weight of cement, are added.

[0091] To a high degree, the effect is also dependent on the chemical structure and the molecular weight of the polymer, which forms the basis of the fluidizer.

[0092] In order to demonstrate the increased effectiveness of the inventive copolymers, the flow behavior of concrete mixtures containing the copolymers E1 to E5 was measured according to DIN 1048, part1, and ASTM C143. As a comparison, the polymers C-1 to C-8 were also tested with the same methods.

[0093] Preparation and Handling of the Concrete Specimen

[0094] The cement and the aggregates were premixed for 15 seconds in a 50 liter forced circulation mixer for concrete. The mixing water, containing the fluidizer, was added slowly under stirring over 20 seconds. The batch was then mixed in a wet state for an additional 60 seconds. A part of the fresh concrete was then immediately filled into the mold for the determination of the flow table spread and the slump.

[0095] Immediately after measuring the flow table spread, test bodies having edges of 12×12 cm were prepared, and the compressive strength was measured after 1, 7, and 28 days in accordance with DIN 1048, Part 1. The determination of initial setting was carried out according to ASTM-C 403.

[0096] Additionally, the copolymers of the present invention were compared to the comparative polymers C-1 to C-3.

[0097] As mentioned above, the flow table spread and slump was measured immediately after mixing, and re-measured at 60 and 120 minutes after mixing. A mixing up of the concrete for five seconds was carried out before each new measurement.

[0098] Concrete test mixtures No 1 to 11 which were prepared under the same conditions, were then subjected to the above-described examination of flow table spread and slump depending on the time.

[0099] The results are summarized in Table 4. They show a high water reduction and a surprisingly long lasting constancy of the flow table spread and the slump of up to 120 minutes in test mixtures nos. 2, 4, 6, 8, 10, 11 containing the copolymers according to the invention. From a comparison of these mixtures with comparative mixtures nos.1, 3, 5, 7 and 9 containing the alkanolamine-free polymers, it can be seen, that the comparative test mixtures show a strong retardation of the early strength development. Also, comparative mixtures no 12, 13 and 14 containing polyacrylic acid and melamine- and naphthalene polycondensate show a considerable stiffening tendency already 60 minutes after mixing.

[0100] The measurement of flowing properties of fresh mixtures of high flowing -high strength concrete of very low water-to-cement ratio (W/C) is described in the next test-example.

[0101] High Flowing-High Strength Concrete.

[0102] High flowing-high strength concrete of very low water-to-cement ratio and very high content of binder (cement+silicafume) is increasingly demanded by the building- and construction industry. Preparation and testing are prescribed in Japanese Industrial Standards (JIS-A).

[0103] Preparation of the Concrete Mixtures

[0104] In a mixing ratio as shown in table 5, ordinary Portland cement, silica fume, fine aggregates and coarse aggregates (gravel) were sequentially placed inside a forced mixing-type mixer of 50 liters volume. The cement and the aggregates were premixed for 15 seconds, and then the mixing water, containing the fluidizer and 0.02% (related to the weight of fluidizer) of a synthetic air detrainer, was added slowly under stirring over 20 seconds. The batch was then mixed in a wet state for 3 minutes. After mixing, the mixture was transferred to a mixing boat and retempering was conducted at a predetermined number of times every 60 minutes and the slump flow and slump with the progression of time was measured for up to 120 minutes according to JIS-A 1101. The procedures specified in JIS-A 1123 and JIS-A 6204 were employed to measure air content and time-dependent compressive strengths.

[0105] Results of the evaluation of the mixtures, containing inventive and comparative polymers, are shown in table 6.

[0106] It is evident from table 6, that the test mixtures 2, 4, 6, 8 10 and 11, containing the inventive, dimethylaminoethyl acrylate-modified polymers, show an improved setting behavior and early-strength development as compared to comparative mixtures 1, 3, 5, 7 and 9 which exhibit strong retardation of initial setting and early strengths whereas test mixtures 12, 13 and 14, which contain conventional polymers, show only poor flowability.

[0107] Corrosion Inhibition of Mild Steel

[0108] The anticorrosive activity of the polymers was tested by the stacked steel test, as is known.

[0109] An aqueous solution containing 1.6% by weight of the polymers and having a water hardness of 177 ppm of calcium was prepared for use in the test.

[0110] Mild steel cylinders of 3.3-4.5 cm length and 2.5 cm in diameter were used as the test material. All surfaces except one end were coated with an epoxy coating.

[0111] The exposed test end of each slug was polished with a power grinding wheel, then was covered with about 1 g of the 1.6%-polymer solution. The exposed end of the second steel slug was placed over the test end to spread the film and prevent evaporation. The stacked steel slugs were then placed in an equilibrated desiccator over water. Tests were carried out at 20° C.

[0112] Tap water of 177 ppm hardness was used as a control in each test.

[0113] The test results (table 7) showed, that solutions containing the inventive polymers even at low concentrations were non corrosive whereas none of the comparative polymers did develop an anticorrosive activity.

[0114] Measurement of the Anticorrosive Effect of Inventive Polymers on Mild Steel in CaCl-Solutions by Cyclic Voltammetry (CV)

[0115] In this example, the influence of the inventive, anolamine-modified corrosion inhibiting polymers in comparison to non modified polymers C1, C2 and C3 on mild steel specimens was investigated.

[0116] The examination was carried out by means of potentiodynamic polarization measurements, performed in aqueous, chloride containing solutions using a potentiostat/galvanostat with scan option and a Camec II station.

[0117] Test Conditions:

[0118] U_max±5V, v_u=1-8350 mV/min

[0119] working electrodes: polished steel plates (mild steel ST37)

[0120] v=10 mV/s

[0121] concentration of inventive and comparative polymers:1.60% based on solids.

[0122] The test solution was neither stirred, nor degassed. The electrode was conditioned for one hour at; i=0.0 mA/cm², then polarization was started.

[0123] Test period: 1 hour; i_max=0.5 mA/m′j₀and j_udepending on

[0124] currents (i_max=30-50 mA)

[0125] After a further conditioning at i=0.50 mA/cm²for 30 minutes, the CV was performed in cathodic direction during 30 minutes.

[0126] As can be seen from the data in table 8, all inventive polymers perform substantially better than the comparative polymers as well as the control, showing higher positive values of both, the pitting- and the repassivation potentials.

[0127] In the following, the influence of inventive tert.-alkanolamines containing polymers on the shrinkage behavior of a mortar of high cement content is demonstrated by the measurement of the strain of 4×4×16 cm³prisms fitted with an inserted neck.

[0128] The test specimen were initially stored for 24 at 20° C. and 95% RH, subsequently, at 23° C. and 50% RH.

[0129] This example clearly demonstrates the shrinkage compensating effect of up to 50% of the inventive polymers on mortar pieces whereas comparative polymers show only poor reduction as compared to the control specimen.

[0130] While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.