CN106045376B - A kind of low entraining shape steel tube concrete admixture and preparation method thereof - Google Patents

Abstract

The invention discloses a low-air-entraining steel pipe concrete admixture, which is compounded by polycarboxylate water-reducing components, plastic-retaining components, air-entraining agents, defoamers, viscosifiers and water. Aiming at the problems of too fast slump loss and large and unstable air content in the preparation and actual construction of steel pipe concrete, the present invention proposes a low-air-entraining concrete-filled steel pipe admixture. The air-entraining effect of the admixture is Significantly reduce the plastic retention performance, and the air content of the mixed steel pipe concrete is controlled within the range of 1.0-2.5%, which can effectively solve the problems of excessive slump loss and large and unstable air content, and the preparation method involved is simple , suitable for promotional applications.

Description

A kind of low air-entraining concrete-filled steel tube admixture and preparation method thereof

technical field

The invention belongs to the technical field of building materials, and in particular relates to a low-air-entraining concrete-filled steel pipe admixture and a preparation method thereof.

Background technique

In recent years, the development of concrete in our country has made the performance of concrete in all aspects continuously improved, and the dependence on concrete water reducer is increasing. Polycarboxylate high-efficiency water-reducing agent is the third generation of high-performance water-reducing agent. The amount of mineral admixtures such as steel slag powder and mineral powder can save cement. It is widely used in the preparation of high-strength and ultra-high-strength concrete. Prominent concrete works.

However, for concrete filled steel pipes, the large loss of air content and slump over time has always been a problem that plagues normal construction. First of all, when the fresh concrete is transported for a long time and long distance, it should be kept at the initial slump level as much as possible to ensure the smooth transportation and pumping of the concrete. Excessive slump loss will seriously affect the construction quality of CFST, and even cause pipe blockage during pumping of CFST and cause construction accidents. The main reason for the loss of slump is that as the cement hydration progresses, the moisture that provides lubrication decreases continuously, and the water reducer is continuously adsorbed by the cement particles and hydration products, so that the effective content of the water reducer in the liquid phase rapidly increases. decrease, the zeta potential and dispersion of the system decrease. In order to slow down the loss of concrete slump, people have adopted methods such as post-mixing method, multiple-adding method, and compound retarder. However, in engineering practice, due to the complexity of operation and the limitation of mixing equipment, the applicability is not strong. In addition, if the composite retarder is compatible with cement, the slump loss will be too fast and abnormal coagulation will occur. Secondly, the air content of the steel pipe core concrete has a great influence on the bonding performance between the inner wall of the steel pipe and the concrete. The traditional polycarboxylate superplasticizers tend to cause high air content and instability in fresh concrete due to the effect of main chain and side chain hydrophobic groups. If the amount of gas in the core concrete is too large, during the pumping and jacking construction of the steel tube concrete, the gas is easily adsorbed on the inner wall of the steel tube under the action of the pumping pressure and the concrete's own gravity and enriched to form a gas film. Offset the expansion of the core concrete, easy to cause the steel pipe wall and concrete debonding.

Contents of the invention

Aiming at the problems of too fast slump loss and large and unstable air content in the preparation and actual construction of the above-mentioned steel pipe concrete, the present invention proposes a low air-entraining concrete-filled steel pipe admixture, the air-entraining effect of the admixture Significantly reduced, the plastic retention performance is significantly improved, the air content of the mixed steel pipe concrete is controlled within the range of 1.0-2.5%, which can effectively solve the problems of excessive slump loss and large and unstable air content, and the preparation method involved is simple , suitable for promotional applications.

To achieve the above object, the technical solution adopted in the present invention is:

A low-air-entraining concrete-filled steel admixture, which is compounded from polycarboxylate-based water-reducing components, plastic-retaining components, air-entraining agents, defoamers, tackifiers, and water, in which polycarboxylate The mass ratio of water-reducing component, plastic-retaining component, air-entraining agent, defoamer and tackifier is 100:(5-25):(0.002-0.005):(0.03-0.07):(0.01-0.10 ); the rest is water, and the obtained low-air-entraining concrete-filled steel tube admixture is diluted to a solid content of 20-25%.

In the above scheme, the weight average molecular weight of the polycarboxylic acid-based water-reducing component is a polymer of 45,000-75,000, and its general structural formula is shown in Formula I:

In the formula, the value range of a and a' is 22-36; the value range of b and b' is 2-7; the value range of c and c' is 15-45; the value range of d and d' is 2-6 ; R and R' are fatty alcohol groups, and the number of C atoms is 12-16; -[EO-PO]-is EO (ethylene oxide)/PO (propylene oxide) random copolymerization segment.

In the above scheme, the polycarboxylate water-reducing component is composed of dibutylene glycol maleate, higher fatty alcohol methacrylate, crosslinking monomer and EO/PO random copolyether acrylate monomer according to 12 :(1.2-2.4):(6-24):(1-2) The molar ratio is formed by copolymerization.

In the above scheme, the molecular weight of the EO/PO random copolyether acrylate monomer is 1000-1500, wherein the mass ratio EO/PO=0.6-1.5.

In the above scheme, the cross-linking monomer is one of monocondensed 1,2-propylene glycol dimethacrylate and polycondensed 1,2-propylene glycol dimethacrylate. The general structural formula is shown in formula II, and the molecular weight is controlled At 200-400:

In the formula, m=1-3.

In the above scheme, the preparation method of the polycarboxylic acid-based water-reducing component comprises the following steps: a) adding EO/PO random copolyether and hydroquinone into the reactor, stirring and heating to 60°C under nitrogen protection -80°C, add acrylic acid dropwise, react for 3-5 hours to generate EO/PO random copolyether acrylate, where EO/PO random copolyether:acrylic acid=1:1, hydroquinone accounts for EO/PO random copolymerization 0.1-0.5% of ether mass; b) Add EO/PO random copolyether acrylate and dibutylene glycol maleate, initiator and chain transfer agent to the reaction kettle, stir and heat the reaction under nitrogen protection atmosphere kettle, heat up to 70-90°C, dropwise add higher fatty alcohol ester of methacrylate and cross-linking monomer, dropwise add within 3 hours, then keep warm for 3-5 hours; c) Slowly cool down to 40-45°C, Add NaOH solution to adjust the pH to neutral to obtain the polycarboxylic acid water-reducing component, and its effective solid content is 40-45%; wherein, the chain initiator is one of ammonium persulfate, potassium persulfate and sodium persulfate The addition amount is 10-30% of the total mass of the reactants; the chain transfer agent is one of mercaptoethanol, thioglycolic acid, mercaptopropionic acid, sodium bisulfite, sodium formate, and sodium hypophosphite, and the addition amount is 1-10% of the total mass of the reactants; the total mass of the reactants is dibutylene glycol maleate, higher fatty alcohol methacrylate, crosslinking monomer and EO/PO random copolyether acrylate monomer The total mass, the molar ratio of dibutylene glycol maleate, higher fatty alcohol methacrylate, crosslinking monomer and EO/PO random copolyether acrylate monomer is 12:(1.2-2.4):( 6-24): (1-2).

In the above scheme, the general structural formula of the plastic-retaining component is shown in formula III, and its molecular weight is controlled at 20000-40000:

In the formula, x=1-4; y=15-34; z=2-5; s=12-30; q=1-3.

In the above-mentioned scheme, the preparation method of the plastic-retaining component comprises the following steps: a) adding tartaric anhydride and hydroquinone (inhibitor) to the reactor for esterification reaction, the reaction temperature is 75-90°C, and the reaction time is 5-10h, hydroquinone accounts for 0.1-0.5% of the quality of tartaric acid, and in the reaction process, 2-butenoic acid accounting for 5-10% of the quality of tartaric acid is added dropwise to obtain macromonomer tartrate-2-butenoic acid ester; b) Add maleic acid, hydroquinone (polymerization inhibitor) and two kinds of polyethylene oxides (the degree of polymerization is 22 and 13 respectively) into the reactor for esterification reaction, the reaction temperature is 80-95°C, The reaction time is 5-10h, hydroquinone accounts for 0.1-0.5% of the total mass of maleic acid and polyethylene oxide, and the molar ratio of the two polyethylene oxides (the degree of polymerization is 22 and 13 respectively) is 1 : 1, the mass ratio with maleic acid is respectively 1: (3-3.5) and 1: (5-6), makes two polyoxyethylene ether methacrylates; c) the large monomer tartaric acid- Add 2-butenoic acid ester and dipolyoxyethylene ether methacrylate, initiator and chain transfer agent into the reaction kettle, then raise the temperature to 75-85°C, add sodium styrene sulfonate and butyl methacrylate dropwise, The dropping time is within 4 hours, and then keep warm for 3-5 hours; d) Slowly lower the temperature to 40-45°C, add NaOH solution to adjust the pH to neutral to obtain the plastic-preserving component, whose effective solid content is 40-45% ; wherein the chain initiator is one of ammonium persulfate, potassium persulfate and sodium persulfate, and its addition is 10-30% of the total mass of the reactant; wherein the chain transfer agent is mercaptoethanol, thioglycolic acid, mercapto One of propionic acid, sodium bisulfite, sodium formate, sodium hypophosphite, its addition is 1-10% of the total mass of the reactant; the total mass of the reactant is tartrate-2-butenoate, di Total mass of polyoxyethylene ether methacrylate, sodium styrene sulfonate and butyl methacrylate monomers, 2-butenoate tartrate, dipolyoxyethylene ether methacrylate, sodium styrene sulfonate The molar ratio to butyl methacrylate monomer is 1:(0.5-1):(8-12):(5-15).

In the above scheme, the air-entraining agent is one or more of rosin resins, alkyl and alkyl aromatic hydrocarbon sulfonic acids, fatty alcohol sulfonate air-entraining agents; the defoamer is an organic One of silicon and polyether modified silicone defoamers; the thickener is one of hydroxymethyl cellulose ether, hydroxyethyl cellulose ether, and methyl hydroxyethyl cellulose ether .

The preparation method of the above-mentioned low air-entraining type concrete filled steel tube admixture comprises the following steps: 1) Weighing of raw materials: polycarboxylate water-reducing component, plastic-retaining component, air-entraining agent, defoamer and The adhesive is weighed according to the mass ratio of 100:(5-25):(0.002-0.005):(0.03-0.07):(0.01-0.10); Particles, air-entraining agent, defoamer and tackifier are compounded, and then diluted with water until the solid content of the obtained mixed emulsion is 20-25%.

Using the above proposal, the low-air-entraining concrete-filled steel pipe admixture is applied to prepare steel-filled steel pipe concrete, and its added amount accounts for 0.5-2.0% of the cementitious material used in steel pipe concrete.

The principle of the present invention is: 1) Introducing ethylene oxide/propylene oxide random copolymerization and propylene glycol branched chains into the polycarboxylic acid-based water-reducing components increases the physical steric hindrance hierarchy of the branched chains of the water-reducing group, Delay the contact between moisture in concrete and cement particles, and at the same time, ester groups are gradually hydrolyzed in the alkaline environment of cement concrete to form more COO- groups and form complexes with basic metal ions (Ca ²⁺ ), The concentration of Ca ²⁺ in cement is reduced, and the process of hydration reaction is delayed; 2) Propylene glycol dimethacrylate with a cross-linking structure is used to increase the spatial cross-linking performance of the superplasticizer molecule, and at the same time, the ester group connected by propylene glycol The hydrolysis rate of the structure is slower than that of the general ester group structure, which is more conducive to the release of COO ^- groups in the middle and later stages of the superplasticizer molecules, which increases the dispersion performance of cement concrete in the middle and later stages, and effectively controls the loss of concrete slump over time: 3) By introducing sodium benzenesulfonate and branched alkyl ether groups into the plastic-retaining component, the hydrophobicity of the branched chain is increased. At the same time, tartaric anhydride is introduced to release twice the hydroxyl and carboxyl groups in the early stage of cement hydration. A layer of water film is formed on the surface of cement particles to increase the fluidity and plastic retention of cement concrete; 4) By compounding defoamers, air-entraining agents and water-reducing components, the surface tension of water is reduced, making polycarboxylic acid The large bubbles generated by the branched chains of the components themselves gradually escape or burst, thereby increasing the number of tiny bubbles inside the concrete. These tiny bubbles exist stably inside the concrete due to the decrease in surface tension, and play a ball effect to increase the flow of the concrete. degree and slump.

The beneficial effects of the present invention are:

1) The low-air-entraining concrete-filled steel tube admixture of the present invention can significantly improve the slump loss of steel-filled steel tube concrete, basically guaranteeing no loss of concrete slump within 2 hours, and the slump loss of less than 20mm within 3 hours.

2) Control the initial air content of freshly-mixed steel tube concrete at 1.0-2.5% by compounding water-reducing components, plastic-preserving plastic-preserving agents, air-entraining agents, and defoamers, and control the air content of concrete at 0.8-2.5% after 1 hour. 2.2%, to ensure the stable existence of tiny air bubbles inside the concrete.

3) The low-air-entraining concrete-filled steel pipe admixture of the present invention can effectively reduce the amount of cement used, increase the replacement rate of mineral admixtures, and further save the production cost of steel-filled steel pipe concrete under the premise of ensuring mechanical properties and construction performance.

detailed description

In order to better understand the present invention, the content of the present invention will be further clarified below in conjunction with specific examples, but the content of the present invention is not limited to the following examples.

In the following examples, unless otherwise specified, all reagents used are commercially available chemical reagents.

In the following examples, the cement is Huaxin 42.5 ordinary Portland cement; the fly ash is commercially available Class II fly ash; the expansion agent is Tianjin Baoming HCSA high-performance concrete expansion agent; the crushed stone is 5-25mm continuous graded common Crushed stone; sand is ordinary river sand, which belongs to medium sand.

In the following examples, the preparation method of the EO/PO random polyether comprises the following steps: 1) adding 1,2-propanediol and potassium hydroxide into the autoclave, vacuuming and nitrogen replacement 3 times; 2) Add ethylene oxide and propylene oxide into the reaction kettle according to the mass ratio of 40:60, control the temperature at 115°C, the vacuum kettle pressure is 0.4Mpa, the reaction time is 6 hours, and the amount of potassium hydroxide is ethylene oxide and ring 0.25‰ of the total mass of propylene oxide, and 1,2-propanediol is 20% of the total mass of ethylene oxide and propylene oxide; 3) vacuum dehydration and drying to obtain the EO/PO random polyether.

Embodiment 1-3 and comparative example 1

A low-air-entraining special admixture for concrete-filled steel pipes, the parts by weight of each component are shown in Table 1, and its preparation method includes the following steps:

(1) Synthesis of polycarboxylate water-reducing components

a) Add EO/PO random copolyether and hydroquinone into the reaction kettle, stir and heat to 65°C under nitrogen protection, add dropwise acrylic acid, and react for 4 hours to generate EO/PO random copolyether acrylate, wherein The mass ratio of EO/PO random copolyether to acrylic acid is 1:1, hydroquinone accounts for 0.4% of the mass of EO/PO random copolyether; b) mix EO/PO random copolyether acrylate and maleic acid Dibutylene glycol ester, initiator and chain transfer agent are added in the reaction still, under the nitrogen protective atmosphere stirring heating reaction still, be warming up to 85 ℃, dropwise add higher fatty alcohol methacrylate (the number of carbon atoms is 13), Monocondense 1,2-propanediol dimethacrylate, add dropwise within 3 hours, then keep warm for 4 hours; c) Slowly lower the temperature to 40°C, add NaOH solution to adjust the pH to neutral to obtain the polycarboxylic acid system The water-reducing component has an effective solid content of 43%; wherein, the chain initiator is a mixture of ammonium persulfate and potassium persulfate in a mass ratio of 1:1, and its addition is 18% of the total mass of reactants; chain transfer The agent is sodium bisulfite, and its addition is 6% of the total mass of the reactant; the total mass of the reactant is dibutylene glycol maleate, higher fatty alcohol methacrylate (number of carbon atoms is 13), The total mass of monocondensed 1,2-propanediol dimethacrylate and EO/PO random copolyether acrylate monomer, dibutylene maleate, higher fatty alcohol methacrylate, crosslinking monomer and The molar ratio of EO/PO random copolyether acrylate monomer is 12:1.5:18:1.8, and the weight average molecular weight of the obtained polycarboxylate water-reducing component is 45000-51000, and its structural formula is shown in formula IV:

(2) Synthesis of plastic-preserving components

a) Add tartaric anhydride and hydroquinone (inhibitor) into the reaction kettle for esterification reaction, the reaction temperature is 85°C, the reaction time is 5h, hydroquinone accounts for 0.5% of the tartaric acid mass, and during the reaction, dropwise The 2-butenoic acid of tartaric acid quality 7%, makes macromer tartrate-2-butenoic acid ester; b) maleic acid, hydroquinone (polymerization inhibitor) and two kinds of polyethylene oxide ( Polymerization degree is respectively 22 and 13) add in the reactor and carry out esterification reaction, and reaction temperature is 80 ℃, and reaction time is 10h, and hydroquinone accounts for 0.4% of maleic acid and polyethylene oxide gross mass, two kinds The molar ratio of polyethylene oxide (the degree of polymerization is 22 and 13 respectively) is 1:1, and the mass ratios of them to maleic acid are 1:3.4 and 1:5.5, respectively, to obtain dipolyoxyethylene ether methacrylic acid ester; c) Add the prepared macromonomer tartrate-2-butenoate and dipolyoxyethylene ether methacrylate, initiator, and chain transfer agent into the reactor, then heat up to 85°C, and add styrene dropwise Sodium sulfonate and butyl methacrylate are added dropwise within 4 hours, and then incubated for 4 hours; d) Slowly lower the temperature to 40°C, and add NaOH solution to adjust the pH to neutral to obtain the plastic-preserving component, which is effective Solid content is 43%; Wherein, chain initiator is potassium persulfate, and its addition is 28% of reactant gross mass; Wherein, chain transfer agent is thioglycolic acid, and its addition is 5% of reactant gross mass; The total mass of the reactant is the total mass of tartrate-2-butenoic acid ester, dipolyoxyethylene ether methacrylate, sodium styrene sulfonate and butyl methacrylate monomer, and tartrate-2-butenoic acid ester , dipolyoxyethylene ether methacrylate, sodium styrene sulfonate and butyl methacrylate monomers in a molar ratio of 1:8:0.8:6; the molecular weight of the obtained plastic-retaining component is 20000-25000, and the structural formula is shown in Formula V:

(3) Compounding of special admixtures for steel tube concrete

The prepared polycarboxylate water reducer component, plastic retaining component, LP.HW10 sodium lauryl alcohol ether sulfate (air-entraining agent), PAC organosilicon defoamer and methylol with a molecular weight of 100000 The cellulose ether viscosifier was compounded, and its compounding formula is shown in Table 1, and then diluted with water until the solid content of the obtained mixed emulsion was 25%, that is, the special admixture for the low air-entraining concrete filled steel tube was obtained.

The compound formula (parts by weight) of admixture described in table 1 embodiment 1-3 and comparative example 1

serial number Polycarboxylate water reducing component Plastic component air entraining agent Defoamer Tackifier Example 1 100 twenty three 0.002 0.05 0.06 Example 2 100 18 0.003 0.05 0.04 Example 3 100 10 0.003 0.03 0.03 Comparative example 1 100 0 0 0 0

The products obtained in Examples 1-3 and Comparative Example 1 were respectively subjected to a cement paste fluidity test, a setting time test and a mortar strength test. Among them, the slurry fluidity test is tested according to the relevant regulations of GB8077-2012 "Concrete Admixture Homogeneity Test Method"; the setting time is measured according to the method of GB 8076-2008 "Concrete Admixture"; the fluidity of the mortar mixed with the admixture is controlled at Within the range of 180mm±5mm, the measurement results are shown in Table 2.

Table 2 embodiment 1-3 and comparative example 1 obtained product's cement paste fluidity and setting time results

The above results show that the dispersion effect of the admixture obtained in Examples 1 to 3 is excellent, and the fluidity loss of the cement paste after 2 hours is small, and the plastic retention time is longer than that of the single-mixed polycarboxylate water-reducing component. Slightly extended.

Embodiment 4-6, comparative example 2

A special admixture for low-air-entraining concrete-filled steel tubes, the parts by weight of each component are shown in Table 3, and its preparation method includes the following steps:

(1) Synthesis of polycarboxylate water-reducing components

a) Add EO/PO random copolyether and hydroquinone into the reaction kettle, stir and heat to 70°C under nitrogen protection, add dropwise acrylic acid, and react for 4.5 hours to generate EO/PO random copolyether acrylate, wherein The mass ratio of EO/PO random copolyether to acrylic acid is 1:1, hydroquinone accounts for 0.3% of the mass of EO/PO random copolyether; b) mix EO/PO random copolyether acrylate and maleic acid Dibutylene glycol ester, initiator and chain transfer agent are added in the reaction still, under the nitrogen protective atmosphere stirring heating reaction still, be warming up to 80 ℃, dropwise add higher fatty alcohol ester of methacrylate (number of carbon atoms is 15), Tricondensed 1,2-propanediol dimethacrylate, dropwise added within 3 hours, and then kept the temperature for 5 hours; c) Slowly lower the temperature to 45°C, add NaOH solution to adjust the pH to neutral to obtain the polycarboxylic acid system The water-reducing component has an effective solid content of 44%; wherein, the chain initiator is ammonium persulfate, and its addition is 22% of the total mass of the reactant; the chain transfer agent is the mass ratio of sodium bisulfite and sodium hypophosphite 1:1 mixture, its addition is 7% of reactant gross mass; Said reactant gross mass is dibutylene glycol maleate, higher fatty alcohol methacrylate (number of carbon atoms is 15), mono The total mass of condensed 1,2-propanediol dimethacrylate and EO/PO random copolyether acrylate monomer, dibutylene maleate, higher fatty alcohol methacrylate, crosslinking monomer and EO The molar ratio of /PO random copolyether acrylate monomer is 12:2:15:1; the weight average molecular weight of the obtained polycarboxylate water-reducing component is 50000-55000, and its structural formula is shown in formula VI:

(2) Synthesis of plastic-preserving components

a) Add tartaric anhydride and hydroquinone (inhibitor) into the reaction kettle for esterification reaction, the reaction temperature is 80°C, the reaction time is 6h, hydroquinone accounts for 0.4% of the tartaric acid mass, and during the reaction process, dripping accounts for 0.4%. The 2-butenoic acid of tartaric acid quality 8%, makes macromonomer tartrate-2-butenoic acid ester; b) maleic acid, hydroquinone (polymerization inhibitor) and two kinds of polyethylene oxide ( Polymerization degree is respectively 22 and 13) add in the reactor and carry out esterification reaction, and reaction temperature is 90 ℃, and reaction time is 8h, and hydroquinone accounts for 0.4% of the total mass of maleic acid and polyethylene oxide, two kinds The molar ratio of polyethylene oxide (the degree of polymerization is 22 and 13 respectively) is 1:1, and the mass ratio with maleic acid is 1:3.2 and 1:5 respectively, to obtain dipolyoxyethylene ether methacrylate ; c) Add the prepared macromonomer tartrate-2-butenoic acid ester and dipolyoxyethylene ether methacrylate, initiator and chain transfer agent into the reactor, then heat up to 80°C, add styrene sulfonate dropwise Sodium methacrylate, butyl methacrylate, dropwise within 4 hours, and then keep warm for 3 hours; d) Slowly cool down to 40°C, add NaOH solution to adjust the pH to neutral to obtain the plastic-preserving component, which effectively solidifies Content 42%; Wherein, chain initiator is potassium persulfate, and its addition is 25% of reactant gross mass; Wherein, chain transfer agent is the mixture of mercaptoacetic acid and mercaptopropionic acid obtained by the mass ratio of 2:1, its The addition amount is 8% of the total mass of reactants; The total mass of tartrate-2-butenoic acid ester, dipolyoxyethylene ether methacrylate, sodium styrene sulfonate and butyl methacrylate monomer is 1:10:0.7:8 in molar ratio; The molecular weight of the plastic component is 30000-35000, and the structural formula is shown in formula VII:

(3) Compounding of special admixtures for steel tube concrete

The prepared polycarboxylate water reducer component, plastic retaining component, 3N70 sodium lauryl ether sulfate air-entraining agent, M.2005 polyether defoamer and hydroxymethylcellulose with a molecular weight of 100,000 The ether tackifier was compounded, and its compounding formula is shown in Table 3, and then diluted with water until the solid content of the obtained mixed emulsion was 25%, to obtain the low air-entraining special admixture for steel pipe concrete.

The compound formula (parts by weight) of the admixture obtained in table 3 embodiment 4-6

serial number Polycarboxylate water reducing component High-efficiency plasticizer air entraining agent Defoamer Tackifier Example 4 100 20 0.002 0.04 0.03 Example 5 100 15 0.003 0.05 0.04 Example 6 100 10 0.004 0.06 0.05

The admixture in comparative example 2 is commercially available YJ-1 polycarboxylate water reducer produced by Jiangsu Bote, and its effective solid content is 25%.

The products obtained in Examples 4-6 and the YJ-1 type polycarboxylate water reducer described in Comparative Example 2 were subjected to a cement paste fluidity test, a setting time test and a mortar strength test. Among them, the slurry fluidity test is tested according to the relevant regulations of GB8077-2012 "Concrete Admixture Homogeneity Test Method"; the setting time is measured according to GB 8076-2008 "Concrete Admixture" method, and the fluidity of the mortar mixed with the admixture is controlled at Within the range of 180mm±5mm, the measurement results are shown in Table 4.

Table 4 embodiment 4-6 obtained product and comparative example 2 described cement slurry fluidity and coagulation time result

The above results show that the dispersion effect of the admixture obtained in Examples 4 to 6 is excellent, and after 2 hours, the fluidity loss of the cement slurry is small, the plastic retention effect is good, and the coagulation time is prolonged compared with the general polycarboxylate water reducer. It is beneficial to the long-distance and long-term pumping construction of steel pipe concrete.

Application Examples 1-3 and Comparative Example 3

The special admixture for low-air-entraining concrete-filled steel tubes obtained in Example 4 and the YJ-1 polycarboxylate-based water-reducer described in Comparative Example 2 were applied to the preparation of C50 concrete-filled steel tubes. The concrete mix ratios were shown in Table 5, and then The initial slump/expansion, 3h slump/expansion, air content, compressive strength and other properties of the obtained concrete were tested. The results are shown in Table 6.

Table 5C50 Mixing ratio of steel pipe concrete (kg/m ³ )

serial number cement fly ash expansion agent sand gravel water Admixture Application example 1 430 75 45 787 923 160 4.4 Application example 2 430 75 45 787 923 160 5.5 Application example 3 430 75 45 787 923 160 6.6 Comparative example 3 430 75 45 787 923 160 8.8

Table 6 Performance test results of C50 concrete filled steel tubes prepared by application examples 1-3 and comparative example 2

As can be seen from Table 6, along with the increase of the admixture of the present invention, its retarding and plastic-retaining properties are improved, and the slump loss in 3 hours is less than 30mm, and the air content of the freshly mixed steel tube concrete is basically Maintained within a reasonable range, and the admixture can significantly improve the compressive strength of concrete at all ages. Compared with ordinary polycarboxylate water reducers, it can increase the initial flow performance and retardation of concrete while reducing the amount of admixture The plastic-retaining effect ensures the transportation and pumping construction of steel pipe concrete.

To sum up, the present invention effectively solves the shortcoming of the admixture slowing the settling and retaining plastic through the molecular design of the polycarboxylic acid-based component and the plastic-retaining component. The method of compounding defoamer, air-entraining agent and tackifier can effectively control the air content of fresh concrete in the range of 1.0-2.5%, improve the initial flow performance of concrete, and is beneficial to the bonding of concrete and steel pipes and the concrete It can strengthen the strength in the later stage, and can reduce the amount of admixture or the amount of cementitious materials to a certain extent, which is suitable for popularization and application.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the creative concept of the present invention, some improvements and changes are made, and these all belong to the protection of the present invention. scope.

Claims (9)

1. A low air-entraining type concrete filled steel admixture is characterized in that it is formed by compounding polycarboxylate water-reducing components, plastic-retaining components, air-entraining agents, defoamers, tackifiers and water into, wherein the mass ratio of polycarboxylate water reducing component, plastic retaining component, air-entraining agent, defoamer and tackifier is 100:(5-25):(0.002-0.005):(0.03-0.07 ): (0.01-0.10); the rest is water, and the gained low air-entraining concrete-filled steel tube admixture is diluted to a solid content of 20-25%; The general structural formula of the plastic-retaining component is shown in formula III, and its molecular weight is controlled at 20000-40000: In the formula, x=1-4; y=15-34; z=2-5; s=12-30; q=1-3. 2. The low air-entraining concrete-filled steel pipe admixture according to claim 1, characterized in that, the weight average molecular weight of the polycarboxylate water-reducing component is 45000-75000, and its general structural formula is shown in formula I: In the formula, the value range of a and a' is 22-36; the value range of b and b' is 2-7; the value range of c and c' is 15-45; the value range of d and d' is 2-6 ; R and R' are fatty alcohol groups, and the number of C atoms is 12-16; -[EO-PO]- is EO/PO random copolymerization segment. 3. The low air-entraining type concrete-filled steel admixture according to claim 2, wherein the polycarboxylate water-reducing component is composed of dibutylene glycol maleate, higher fatty alcohol methacrylate, The crosslinking monomer and EO/PO random copolyether acrylate monomer are copolymerized according to the molar ratio of 12:(1.2-2.4):(6-24):(1-2). 4. The low air-entraining concrete-filled steel tube admixture according to claim 2, characterized in that, the molecular weight of the EO/PO random copolyether acrylate monomer is 1000-1500, wherein the mass ratio EO/PO=0.6- 1.5. 5. The low-air-entraining concrete-filled steel pipe admixture according to claim 3, wherein the crosslinking monomer is monocondensed 1,2-propanediol dimethacrylate, polycondensed 1,2-propanediol bismethacrylate One of the methacrylates, the general structural formula is shown in formula II, and the molecular weight is controlled at 200-400: In the formula, m=1-3. 6. The low air-entraining type concrete filled steel admixture according to claim 1, characterized in that the air-entraining agent is rosin resins, alkyl and alkyl aromatic hydrocarbon sulfonic acids, fatty alcohol sulfonate air-entraining one or more of the agents. 7. The low-air-entraining concrete retarding admixture for steel pipes according to claim 1, wherein the defoamer is one of organosilicon and polyether modified organosilicon defoamers. 8. The low-air-entraining steel pipe retarding soil admixture according to claim 1, wherein the tackifier is hydroxymethyl cellulose ether, hydroxyethyl cellulose ether, methyl hydroxyethyl fiber One of the ethers. 9. The preparation method of the low-air-entraining type concrete-filled steel pipe admixture described in any one of claims 1-8, is characterized in that, comprises the following steps: 1) taking by weighing of raw materials: polycarboxylate water-reducing component, water-retaining The plastic component, air-entraining agent, defoamer and tackifier are weighed according to the mass ratio of 100:(5-25):(0.002-0.005):(0.03-0.07):(0.01-0.10); 2) The polycarboxylate water-reducing component, plastic-retaining component, air-entraining agent, defoamer, and tackifier are compounded, and then diluted with water until the solid content of the obtained mixed emulsion is 20-25%.