A concrete admixture suitable for high-altitude pumping and its preparation method and application

Abstract

The present invention provides a concrete admixture suitable for high-altitude pumping, and its preparation method and application. The concrete admixture of the present invention first obtains an air-entraining water-reducing agent (DAFS) and an anti-mud viscosity-reducing water-reducing agent (DPCE) by modifying a polycarboxylic acid water-reducing agent using dihydroeugenol, etc., and then physically compounding the above two water-reducing agents with functional components such as an appropriate amount of defoaming agent to prepare an ultra-dispersed, high-air-entraining, viscosity-controlled type machine-made sand concrete admixture suitable for ultra-elevation pumping. The admixture of the present invention is added to concrete, and has good dispersibility and stable air-entraining effect (small bubbles and uniform and stable distribution), high water reduction rate, high flow state, self-compacting, anti-mud viscosity reduction and other characteristics, which can effectively improve the working performance (pumpability, workability) and compactness of high-performance concrete used for large-span suspended arch bridges, and has important practical application value for arch bridge construction in high-altitude areas.

Description

Technical Field

[0001] The invention belongs to the field of building material admixtures, and in particular relates to a concrete admixture suitable for high-altitude pumping, and a preparation method and application thereof. Background Art

[0002] my country has now become a major bridge country in the world, and many bridges have leapt into the forefront of the world's bridge spans. In recent years, bridge engineering has developed rapidly, the scale of bridges has continued to expand, and a large number of new large-span bridges have emerged. In particular, large arch bridges are mainly built in remote mountainous areas with high mountains and deep canyons. The raw materials and construction environment are relatively complex, but the existing concrete admixtures are difficult to meet the requirements of bridge construction in high-altitude mountainous areas, mainly in the following three aspects: (1) The air pressure in high-altitude areas is relatively low, and the bubble migration speed is faster than that in normal pressure environments. The commonly used alkyl sulfonates, saponins and polyethers and other air-entraining agents have reduced bubble stability in the low-air environment of the plateau, and the bubble spacing coefficient and bubble size increase. In addition, ordinary air-entraining agents are easy to migrate to the steel pipe wall during the pumping process of large-span arch bridge concrete, causing the concrete to be wet at the edge and dry in the middle in the pumping pipe, affecting the working performance. Therefore, the bubbles in the arch bridge concrete prepared with ordinary air-entraining agents are easy to float and the size is easy to increase, the pore structure is easy to change, and the workability is poor, which leads to the reduction of concrete mechanical and durability properties. (2) There are many canyon rivers in high-altitude areas, and the ecological environment is fragile. In the process of bridge construction, local materials are used, and machine-made sand is used instead of natural river sand. However, machine-made sand has many edges and corners, a rough surface, and large voids. The prepared concrete is easy to separate and bleed. At the same time, machine-made sand contains a large amount of stone powder and mud, which leads to high viscosity, rapid collapse, and poor workability of the concrete. (3) For large-span suspended arch bridges, the main arch ring is relatively high (300-400m), and the steel bars are arranged densely. In addition, the pumped concrete contains steel fibers, which will further reduce the working performance of the concrete. Therefore, high-performance concrete with high fluidity, self-compacting and good pumping performance is required. Existing concrete admixtures are difficult to achieve the above goals.

[0003] Therefore, in response to the problems existing in the concrete construction of bridges in the above-mentioned high-altitude areas, there is an urgent need for an ultra-elevation pumpable high-toughness machine-made sand concrete admixture suitable for large-span suspended arch bridges to improve the performance of machine-made sand concrete in the construction of arch bridges in high-altitude areas, so that it can be more widely used in harsh environments such as remote and rugged mountainous areas and turbulent rivers. Summary of the invention

[0004] In view of this, the present invention provides a concrete admixture suitable for high-altitude pumping and a preparation method and application thereof, so as to solve the defects existing in the prior art.

[0005] In a first aspect, the present invention provides an air-entraining water-reducing agent, the structural formula of the air-entraining water-reducing agent is as follows:

[0006]

[0007] Wherein, x is a positive integer between 30 and 80, and y is a positive integer between 20 and 70.

[0008] In a second aspect, the present invention further provides a method for preparing the air-entraining water-reducing agent, comprising the following steps:

[0009] Sodium pyrosulfite and liquid caustic soda are added to water to obtain a sodium bisulfite solution;

[0010] Acetone, dihydroeugenol and an auxiliary agent are added to a sodium bisulfite solution, and a sulfonation reaction occurs between the sodium bisulfite and the acetone to generate sodium α-olefin sulfonate;

[0011] After the sulfonation reaction is completed, formaldehyde is added to carry out a condensation reaction. After the condensation reaction is completed, a foam stabilizer is added to obtain an air-entraining water-reducing agent.

[0012] Preferably, the method for preparing the air-entraining water-reducing agent comprises adding acetone, dihydroeugenol and an auxiliary agent to a sodium bisulfite solution, and performing a sulfonation reaction at a temperature not higher than 55° C. to generate sodium α-olefin sulfonate;

[0013] After the sulfonation reaction is completed, formaldehyde is added dropwise while maintaining the temperature unchanged. After the formaldehyde is added, the temperature is raised to 95-99°C for condensation reaction. After the condensation reaction is completed, a foam stabilizer is added to obtain an air-entraining water-reducing agent.

[0014] Preferably, in the preparation method of the air-entraining water-reducing agent, the mass ratio of the dihydroeugenol, sodium pyrosulfite, acetone, formaldehyde and auxiliary agent is (10-15):(35-40):(45-55):(130-140):(1-5);

[0015] The liquid alkali includes at least one of a sodium hydroxide solution and a potassium hydroxide solution.

[0016] In a third aspect, the present invention further provides a concrete admixture suitable for high-altitude pumping, comprising the air-entraining water-reducing agent or the air-entraining water-reducing agent prepared by the preparation method.

[0017] Preferably, the concrete admixture further comprises an anti-mud viscosity-reducing water-reducing agent, and the structural formula of the anti-mud viscosity-reducing water-reducing agent is as follows:

[0018]

[0019] Wherein, a is a positive integer between 5 and 20, b is a positive integer between 20 and 100, c is a positive integer between 1 and 5, and n is a positive integer between 25 and 55.

[0020] Preferably, the concrete admixture suitable for high-altitude pumping, the preparation method of the anti-mud viscosity-reducing water-reducing agent, comprises the following steps:

[0021] Using epichlorohydrin and methyl allyl polyoxyethylene ether as raw materials, methyl allyl polyoxyethylene chlorohydrin ether intermediate is prepared by ring-opening polymerization reaction;

[0022] Using dihydroeugenol and methylallyl polyoxyethylene chlorohydrin ether intermediate as raw materials, dihydroeugenol grafted polyether macromonomer was prepared;

[0023] The anti-mud and viscosity-reducing water-reducing agent was prepared with methyl allyl polyoxyethylene ether, acrylic acid and dihydroeugenol grafted polyether macromonomer as raw materials.

[0024] Preferably, the concrete admixture suitable for high-altitude pumping is prepared by heating and melting methyl allyl polyoxyethylene ether, adding boron trifluoride ethyl ether, and dripping epichlorohydrin at 55-65° C. to prepare methyl allyl polyoxyethylene chlorohydrin ether intermediate through ring-opening polymerization; wherein the molar ratio of boron trifluoride ethyl ether, epichlorohydrin, and methyl allyl polyoxyethylene ether is (0.03-0.05):(1.2-1.3):(0.9-1.1);

[0025] After mixing dihydroeugenol and methyl allyl polyoxyethylene chlorohydrin ether intermediate, adjusting the pH to 12-13, reacting at 75-85° C., to obtain dihydroeugenol grafted polyether macromonomer;

[0026] The molar ratio of the dihydroeugenol to the methyl allyl polyoxyethylene chlorohydrin ether intermediate is (0.8-1.2):(0.8-1.2);

[0027] The concrete admixture also includes a defoamer, a viscosity modifier and a retarder.

[0028] Preferably, in the concrete admixture suitable for high-altitude pumping, the mass ratio of the air-entraining water-reducing agent, the anti-mud and viscosity-reducing water-reducing agent, the defoaming agent, the viscosity modifier and the retarder is 1:(0.6-1.2):(0.1-0.5):(0.03-0.07):(0.02-0.06).

[0029] In a fourth aspect, the present invention also provides a use of the concrete admixture in preparing high-altitude pumped machine-made sand concrete.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. When the air-entraining water-reducing agent (DAFS) of the present invention introduces more bubbles, the volume of the bubbles increases, resulting in a decrease in free water, and the buoyancy generated by the bubbles will affect the shear stress of cement particles. Within the adsorption saturation dosage range of DAFS, the concentration of sulfonate anions in the cement slurry increases with the dosage, the electrostatic repulsion effect on cement particles is enhanced, and the fluidity of the cement slurry increases with the dosage. After reaching the adsorption saturation dosage, the amount of DAFS adsorbed on the surface of cement particles no longer increases, the electrostatic repulsion effect no longer increases, while the amount of free water continues to decrease, and the buoyancy generated by the introduced bubbles continues to increase, resulting in a decrease in dispersion performance. DAFS can prolong the hydration heat induction period, delay the main exothermic peak, and increase the peak exothermic rate. DAFS depolymerizes the flocculation structure between cement particles, increases the free water in the cement pore solution, and can increase the total hydration degree of cement slurry by 10%.

[0032] 2. The concrete admixture suitable for high-altitude pumping of the present invention includes an air-entraining water-reducing agent (DAFS) and an anti-mud and viscosity-reducing water-reducing agent (DPCE). The polyether macromonomer is grafted with dihydroeugenol, which can effectively transform the terminal hydroxyl group of the polyether macromonomer into a new macromonomer containing a rigid benzene ring and a small molecule fragment of hydrophobic propane. The steric hindrance effect of the benzene ring can be used to reduce the chemical intercalation adsorption of the PEO side chain between clay layers, which can greatly reduce the intercalation adsorption of PCE between clay layers, thereby improving the dispersion performance of PCE in concrete prepared with mud-containing machine-made sand; the ultra-high-altitude pumping high-toughness machine-made sand concrete admixture obtained by the present invention has an air entrainment rate of more than 50% higher than that of ordinary admixtures under low pressure conditions in the west, effectively improving the frost resistance and durability of concrete in high-altitude areas. Introducing a large number of stable tiny bubbles (which act as lubricants) can improve the viscosity, pumpability and workability of concrete. At the same time, it can resist mud and reduce viscosity, be self-compacting, change the cement hydration process, regulate the concrete microstructure, and effectively improve the workability and volume stability of concrete. It is of great significance for the preparation of high-performance machine-made sand concrete used in bridges, and has important practical application value for the western development project. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 is the structural formula of the air-entraining water-reducing agent (DAFS) of the present invention;

[0035] Figure 2The infrared spectrum (IR) of the air-entraining water-reducing agent (DAFS) prepared by the present invention;

[0036] Figure 3 The hydrogen nuclear magnetic spectrum of the air-entraining water-reducing agent (DAFS) prepared by the present invention is ( 1 H NMR) spectra;

[0037] Figure 4 This is an infrared spectrum (IR) of the anti-mud viscosity-reducing water-reducing agent (DPCE) prepared by the present invention;

[0038] Figure 5 The nuclear magnetic hydrogen spectrum ( 1 H NMR) spectra;

[0039] Figure 6 This is the expansion state diagram of the machine-made sand concrete of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". Various embodiments of the present invention may be in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the numbered ranges, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated in this article, it is meant to include any cited numbers (fractions or integers) within the indicated range.

[0042] The present application provides an air-entraining water-reducing agent, the structural formula of which is as follows:

[0043]

[0044] ; Wherein, x is a positive integer between 30 and 80, and y is a positive integer between 20 and 70.

[0045] Based on the same inventive concept, the present invention also provides a method for preparing the above-mentioned air-entraining water-reducing agent, comprising the following steps:

[0046] S1, adding sodium pyrosulfite and liquid caustic soda into water to obtain a sodium bisulfite solution;

[0047] S2, adding acetone, dihydroeugenol and an auxiliary agent to the sodium bisulfite solution, and the sodium bisulfite and acetone undergo a sulfonation reaction to generate sodium α-olefin sulfonate;

[0048] S3. After the sulfonation reaction is completed, formaldehyde is added to carry out condensation reaction. After the condensation reaction is completed, a foam stabilizer is added to obtain an air-entraining water-reducing agent.

[0049] Specifically, in step S2, after the sulfonation reaction is completed, formaldehyde is added to carry out a condensation reaction. Since acetone is excessive in the initial stage of the reaction, formaldehyde and acetone first generate a large amount of dimethylolacetone through a cross-aldol condensation reaction, and then alternately condense with the previous sodium α-hydroxysulfonate to form a main chain with a dispersing effect, while dihydroeugenol has only one active hydrogen atom, which dehydrates and condenses with dimethylolacetone to both ends of the main chain to obtain a high molecular polymer that is hydrophobic at both ends.

[0050] The structural formula of the air-entraining water-reducing agent prepared by the present invention is as follows: Figure 1 As shown, specifically, liquid alkali (such as sodium hydroxide solution) is added to water to make the pH value of the base material strongly alkaline, and then sodium pyrosulfite is added to dissolve it to obtain a saturated solution of sodium bisulfite; then acetone is added dropwise to react with the saturated solution of sodium bisulfite, and α-olefin sodium sulfonate is generated through a sulfonation reaction; dihydroeugenol and an auxiliary agent are added before the sulfonation reaction begins, and the temperature is immediately raised after the sulfonation reaction is completed, and formaldehyde is added dropwise to carry out a condensation reaction. The dihydroxymethylacetone generated in the early stage of the condensation reaction is dehydrated and condensed with the polycondensate of sodium α-olefin sodium sulfonate and dihydroeugenol, and an appropriate amount of a foam stabilizer is added to the final reaction product to obtain an air-entraining water-reducing agent (DAFS). The present invention uses dihydroeugenol as a key raw material, and grafts it to both ends of the sulfonated acetone formaldehyde polycondensate through chemical modification to prepare a high air-entraining water-reducing agent (DAFS).

[0051] In some embodiments, acetone is added to a sodium bisulfite solution, and dihydroeugenol and an auxiliary are added at the same time, and a sulfonation reaction is performed at a temperature not higher than 55° C. to generate sodium α-olefin sulfonate.

[0052] In some embodiments, after the sulfonation reaction is completed, formaldehyde is added dropwise while maintaining the temperature unchanged. After the formaldehyde is added, the temperature is raised to 95-99° C. for condensation reaction. During this process, dihydroeugenol is added for dehydration and condensation. At the same time, an auxiliary agent is added. After the condensation reaction is completed, a foam stabilizer is added to obtain an air-entraining water-reducing agent.

[0053] Specifically, the additive in the above embodiment is provided by Wuhan Subo New Building Materials Co., Ltd., model AM01. Adding the additive can make the bubbles inside the concrete mixed with DAFS smaller and more stable.

[0054] Specifically, the foam stabilizer in the above embodiments can be cellulose ether, glutinous rice paste, etc.

[0055] In some embodiments, the mass ratio of dihydroeugenol, sodium metabisulfite, acetone, formaldehyde and auxiliary agent is (10-15):(35-40):(45-55):(130-140):(1-5); preferably (10-15):38:50:136:2. In practice, the fixed amounts of acetone and formaldehyde are 50g and 136g, respectively.

[0056] In some embodiments, the base includes at least one of sodium hydroxide and potassium hydroxide.

[0057] In some embodiments, when preparing air-entraining water-reducing agent (DAFS), during the condensation reaction thereof, in order to prevent the reaction from being difficult to control and to allow acetone and formaldehyde to fully react to generate more dimethylolacetone, the formaldehyde is added dropwise, so that in the initial stage of the reaction, acetone in excess can react with formaldehyde through a cross aldol condensation reaction to generate a large amount of dimethylolacetone.

[0058] In some embodiments, the specific preparation method of the air-entraining water-reducing agent (DAFS) comprises the following steps: adding measured deionized water, sodium hydroxide aqueous solution (liquid caustic soda) and sodium metabisulfite in a four-necked flask equipped with an agitator, a condenser and a thermometer in sequence, adding acetone after stirring and dissolving and continuing to stir for 10 minutes, adding dihydroeugenol and an auxiliary agent, sulfonating for 1 hour at a temperature not exceeding 55° C., and after the sulfonation is completed, adding formaldehyde dropwise for 3 hours while maintaining the temperature unchanged, heating to 97±2° C. for condensation for 2.5 hours, and finally cooling the reactants to room temperature to obtain a high air-entraining water-reducing agent solution (DAFS).

[0059] Based on the same inventive concept, the present invention also provides a concrete admixture suitable for high-altitude pumping, including the above-mentioned air-entraining water-reducing agent or the air-entraining water-reducing agent prepared by the above-mentioned preparation method.

[0060] In some embodiments, the concrete admixture suitable for high-altitude pumping further includes an anti-mud viscosity-reducing water-reducing agent, and the structural formula of the anti-mud viscosity-reducing water-reducing agent is as follows:

[0061]

[0062] Wherein, a is a positive integer between 5 and 20, b is a positive integer between 20 and 100, c is a positive integer between 1 and 5, and n is a positive integer between 25 and 55.

[0063] In some embodiments, the preparation method of the anti-mud viscosity reducing water reducing agent comprises the following steps:

[0064] S1, using epichlorohydrin and methyl allyl polyoxyethylene ether as raw materials, preparing methyl allyl polyoxyethylene chlorohydrin ether intermediate by ring-opening polymerization;

[0065] S2, using dihydroeugenol and methyl allyl polyoxyethylene chlorohydrin ether intermediate as raw materials to prepare dihydroeugenol grafted polyether macromonomer;

[0066] S3. An anti-mud, viscosity-reducing and water-reducing agent is prepared using methyl allyl polyoxyethylene ether, acrylic acid and dihydroeugenol grafted polyether macromonomer as raw materials.

[0067] According to the designability of the molecular structure of a polycarboxylate water-reducing agent, the invention grafts dihydroeugenol onto the terminal hydroxyl group of a methallyl polyether macromonomer, replaces the terminal hydroxyl group of the polyether macromonomer with an alkyl group, and simultaneously introduces a benzene ring functional group to prepare an anti-mud and viscosity-reducing water-reducing agent (DPCE).

[0068] In some embodiments, after methyl allyl polyoxyethylene ether is heated and melted, boron trifluoride etherate is added, and epichlorohydrin is added dropwise at 55-65°C to prepare methyl allyl polyoxyethylene chlorohydrin ether intermediate through ring-opening polymerization; wherein the molar ratio of boron trifluoride etherate, epichlorohydrin, and methyl allyl polyoxyethylene ether is (0.03-0.05):(1.2-1.3):(0.9-1.1).

[0069] In some embodiments, dihydroeugenol and methyl allyl polyoxyethylene chlorohydrin ether intermediate are mixed, the pH is adjusted to 12-13, and the mixture is reacted at 75-85° C. to obtain a dihydroeugenol grafted polyether macromonomer.

[0070] In some embodiments, the molar ratio of dihydroeugenol to methyl allyl polyoxyethylene chlorohydrin ether intermediate is (0.8-1.2):(0.8-1.2).

[0071] In some embodiments, the concrete admixture further includes a defoamer, a viscosity modifier, and a retarder.

[0072] In some embodiments, the mass ratio of air-entraining water-reducing agent, anti-mud and viscosity-reducing water-reducing agent, defoaming agent, viscosity modifier and retarder is 1:(0.6-1.2):(0.1-0.5):(0.03-0.07):(0.02-0.06).

[0073] Among them, the defoaming agent is an ionic adsorption and dispersion defoaming agent, which can ionize into positive ions and negative ions after being dissolved in water. These ions are adsorbed on the surface of colloidal particles with opposite charges, and then a double electric layer is formed on the surface of the ions, resulting in an increase in zeta potential). Silicones, polyethers, etc. can be selected; viscosity modifiers can be selected from polyacrylamide, cellulose ether, polyvinyl alcohol, xanthan gum, etc.; retarders can be selected from sodium gluconate, polyphosphoric acid, sodium citrate, etc.

[0074] In some embodiments, when preparing an anti-mud viscosity-reducing water-reducing agent (DPCE), a method for preparing a dihydroeugenol grafted polyether macromonomer comprises the following steps:

[0075] S1. First, an acid catalysis method is used, with epichlorohydrin (ECH) and methyl allyl polyoxyethylene ether (HPEG, Mx = 2400) as the main raw materials. After HPEG is heated and melted, the commonly used boron trifluoride ether (Et2O·BF3) is used as a catalyst, and ECH is added dropwise at a constant speed at 60°C to prepare a methyl allyl polyoxyethylene chlorohydrin ether intermediate through a ring-opening polymerization reaction; the amount of the three raw materials is n (Et2O·BF3): n (ECH): n (HPEG) = 0.04: 1.25: 1 (molar ratio). The ECH addition time is 0.5h, and after the addition is completed, the reaction is kept warm for 2h and then cooled. The excess ECH is removed by reduced pressure distillation to obtain the finished methyl allyl polyoxyethylene chlorohydrin ether intermediate;

[0076] S2. Continue to use the base catalysis method, with dihydroeugenol and methyl allyl polyoxyethylene chlorohydrin ether intermediate as the main raw materials, add them into the reaction container in a molar ratio of 1:1, use NaOH solution to adjust the pH value to 13, and react at 80°C for 3h to obtain dihydroeugenol grafted polyether macromonomer (D-HPEG).

[0077] In some embodiments, the preparation of the anti-mud viscosity reducing water reducing agent (DPCE) comprises the following steps:

[0078] A new type of anti-mud and viscosity-reducing polycarboxylic acid water reducer (DPCE) was synthesized using methyl allyl polyoxyethylene ether macromonomer (HPEG), dihydroeugenol grafted polyether macromonomer (D-HPEG) and acrylic acid (AA) as main raw materials, with the amount of D-HPEG being 20% ​​to 25% of HPEG and the acid-ether ratio being 4:1 (molar ratio).

[0079] In some embodiments, when preparing the anti-mud viscosity reducing water reducing agent (DPCE), the dripping material containing acrylic acid is added to the base material in a one-time amount of 1 / 3 of the total amount, and the remaining 2 / 3 is added dropwise at a uniform speed.

[0080] In some embodiments, the defoaming agent used is acrylic acid-modified silicone, whose acrylic acid functional group can adsorb cement mineral admixture particles, and silicone can reduce surface tension and induce uniform dispersion of different cementitious material particles.

[0081] In some embodiments, the dosage of the defoaming agent (ie, acrylic modified silicone) is 0.02% to 0.5%.

[0082] The ultra-high-altitude pumpable high-toughness machine-made sand concrete admixture obtained by the present invention has an air entrainment rate increased by more than 50% compared with ordinary admixtures, effectively improving the frost resistance and durability of concrete in high-altitude areas, and introducing a large number of stable tiny bubbles (playing a lubricating role), thereby improving the viscosity, pumpability, workability and volume stability of the concrete. At the same time, the various components can be dispersed well, resist mud and reduce viscosity, and be self-compacting, change the cement hydration process, regulate the concrete microstructure, and effectively ensure the pumping performance and mechanical properties of the concrete. It is of great significance for the preparation of machine-made sand concrete, and has important practical application value for the western development project.

[0083] The principle adopted by the present invention is:

[0084] (1) When more bubbles are introduced by adding high-entraining air-reducing agent (DAFS), the increase in bubble volume leads to a decrease in free water, and the buoyancy generated by the bubbles will affect the shear stress of cement particles. Within the adsorption saturation range of DAFS, the concentration of sulfonate anions in cement paste increases with the increase in the dosage, the electrostatic repulsion effect on cement particles increases, and the fluidity of cement paste increases with the increase in the dosage. After reaching the adsorption saturation dosage, the amount of DAFS adsorbed on the surface of cement particles no longer increases, the electrostatic repulsion effect no longer increases, while the amount of free water continues to decrease, and the buoyancy generated by the introduced bubbles continues to increase, and the dispersibility decreases with the continued increase in the dosage. DAFS can prolong the hydration heat induction period, delay the main exothermic peak, and increase the peak exothermic rate. DAFS depolymerizes the flocculation structure between cement particles, increases the free water in the cement pore solution, and can increase the total hydration degree of cement paste by 10%.

[0085] (2) The anti-mud and viscosity-reducing water-reducing agent (DPCE) used in the present invention first adds epichlorohydrin (ECH) to the terminal hydroxyl group of the polyether macromonomer, and then grafts dihydroeugenol. Through the above two-step reaction, the terminal hydroxyl group of the polyether macromonomer is converted into a new macromonomer containing a rigid benzene ring and a small molecular fragment of hydrophobic propane. The steric hindrance effect of the benzene ring can reduce the chemical intercalation adsorption of the polyoxyethylene (PEO) side chain between clay layers; the terminal hydroxyl group is converted into a hydrophobic alkylbenzene ring to reduce the hydrogen bonding force between the PEO side chain and water, thereby achieving the viscosity reduction function. Its viscosity reduction function is mainly achieved by introducing a rigid steric hindrance group in the side chain and changing the configuration of the polycarboxylate water-reducing agent (PCE), which can greatly reduce the intercalation adsorption of PCE between clay layers, thereby improving the dispersion performance of PCE in concrete prepared with mud-containing machine-made sand, and finally making the concrete show low viscosity and high fluidity.

[0086] Compared with the prior art, the present invention has the following beneficial effects:

[0087] The use of dihydroeugenol grafted polyether macromonomer can effectively transform the terminal hydroxyl group of the polyether macromonomer into a new macromonomer containing a rigid benzene ring and a small molecular fragment of hydrophobic propane. The steric hindrance effect of the benzene ring can be used to reduce the chemical intercalation adsorption of the PEO side chain between clay layers, which can greatly reduce the intercalation adsorption of PCE between clay layers, thereby improving the dispersion performance of PCE in concrete prepared with mud-containing machine-made sand.

[0088] The ultra-high-altitude pumpable high-toughness machine-made sand concrete admixture obtained by the present invention has an air entrainment rate of more than 50% higher than that of ordinary admixtures under low pressure conditions in the west, effectively improving the frost resistance and durability of concrete in high-altitude areas. A large number of stable tiny bubbles (playing a lubricating role) are introduced to improve the viscosity, pumpability and working performance of concrete, while being able to resist mud and reduce viscosity, self-compact, change the cement hydration process, regulate the concrete microstructure, and effectively improve the working performance and volume stability of concrete. It is of great significance for the preparation of high-performance machine-made sand concrete used in bridges, and has important practical application value for western development projects.

[0089] Based on the same inventive concept, the present invention also provides an application of the above-mentioned concrete admixture in the preparation of machine-made sand concrete.

[0090] Specifically, in the above application, the machine-made sand concrete includes PO 42.5 ordinary Portland cement, grade I fly ash, grade S95 mineral powder, machine-made sand, stone, steel fiber, water and the above concrete admixtures;

[0091] Specifically, machine-made sand concrete includes the following raw materials: PO 42.5 cement 550-600 kg / m 3 , Grade I fly ash 140~160kg / m3 、S95 mineral powder 140~150kg / m 3 , Machine-made sand 630~650kg / m 3 、Stone 910~930kg / m 3 , Steel fiber 80~90kg / m 3 , Water 170~180kg / m 3 And 10-15kg of concrete admixture (mother liquor solid content 10%).

[0092] The concrete admixture suitable for high-altitude pumping of the present application and its preparation method and application are further described below with specific examples. This section further illustrates the content of the present invention in conjunction with specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0093] In the following examples, cement used was Huaxin P·O52.5 ordinary Portland cement; silica fume was provided by Shanghai Tiankai Silica Powder Material Co., Ltd., with a SiO2 mass content of 95% and a specific surface area of ​​17500m 2 / kg, 28d activity index 105%; fly ash microbeads were provided by Jingcheng Jiade (Beijing) Trading Co., Ltd., with a loss on ignition of 3.5% and a spherical particle volume rate of 97%.

[0094] In the following examples, the preparation method of air-entraining water-reducing agent (DAFS) comprises the following steps:

[0095] In a four-necked flask equipped with an agitator, a condenser and a thermometer, liquid sodium hydroxide is added into water to make the pH value of the base material strongly alkaline (pH 12), and then sodium metabisulfite is added to dissolve it to obtain a saturated sodium bisulfite solution; acetone is added dropwise at a temperature of 50°C for sulfonation for 1 hour to generate sodium α-olefin sulfonate through sulfonation reaction; after the sulfonation reaction is completed, formaldehyde is added dropwise for 3 hours while maintaining the temperature unchanged, and then dihydroeugenol and an auxiliary agent are added. After the formaldehyde is added, the temperature is raised to 97±2°C for condensation for 2.5 hours, and finally the reactant is cooled to room temperature, and an appropriate amount of a foam stabilizer (specifically cellulose ether) (adding a foam stabilizer of 0.3% by mass of dihydroeugenol) is added to obtain an air-entraining water-reducing agent (DAFS); wherein the mass ratio of dihydroeugenol, sodium metabisulfite, acetone, formaldehyde and an auxiliary agent (provided by Wuhan Subo New Building Materials Co., Ltd., model AM01) is 12:38:50:136:2.

[0096] In the following examples, the preparation method of the anti-mud viscosity reducing water reducing agent (DPCE) comprises the following steps:

[0097] S1. First, an acid catalysis method is used, with epichlorohydrin (ECH) and methyl allyl polyoxyethylene ether (HPEG, Mx=2400) as main raw materials, HPEG is heated and melted, and then common boron trifluoride ether (Et2O·BF3) is used as a catalyst, and ECH is added dropwise at a uniform speed while maintaining 60°C to prepare a methyl allyl polyoxyethylene chlorohydrin ether intermediate through a ring-opening polymerization reaction; the amounts of the three raw materials are n(Et2O·BF3):n(ECH):n(HPEG)=0.04:1.25:1 (molar ratio), the ECH addition time is 0.5h, and after the addition is completed, the reaction is kept warm for 2h and then cooled, and the excess ECH is removed by reduced pressure distillation to obtain a finished methyl allyl polyoxyethylene chlorohydrin ether intermediate;

[0098] S2. Continue to use the base catalysis method, use dihydroeugenol and methyl allyl polyoxyethylene chlorohydrin ether intermediate as the main raw materials, add them into the reaction container in a molar ratio of 1:1, use NaOH solution to adjust the pH value to 13, react at 80°C for 3h, and obtain dihydroeugenol grafted polyether macromonomer (D-HPEG);

[0099] S3. Using dihydroeugenol grafted polyether macromonomer (D-HPEG) and acrylic acid (AA) as raw materials, an anti-mud reduction and viscosity reducing agent (DPCE) was synthesized by free radical copolymerization; the molar ratio of acrylic acid (AA) and dihydroeugenol grafted polyether macromonomer (D-HPEG) was 4:1.

[0100] Figure 2 The infrared spectrum (IR) of the air-entraining water-reducing agent (DAFS) prepared in the present invention.

[0101] Figure 2 In the infrared spectrum (IR) shown, 3448 cm -1 The characteristic absorption peak of hydroxyl (-OH) is 2931cm -1 The characteristic absorption peak of methylene (-CH2-) is 1643cm -1 The strong absorption peak at 1188 cm is the characteristic adsorption peak of carbonyl (C=O). -1 and 1041cm -1 There are stretching peaks of SO and S=O of sulfonic acid groups, which are several typical characteristic peaks of sulfonated acetone formaldehyde condensation polymer (AFS) molecules. Compared with AFS, the characteristic absorption peak of hydroxyl (-OH) of the polymer obtained by air entraining water reducer (DAFS) grafting is significantly weakened, which is related to the disappearance of hydroxyl groups during the dehydration condensation of phenolic compounds and dihydroxyacetone. In addition, DAFS has a peak at 1585cm -1 There is a strong characteristic absorption peak of benzene ring at the bottom, indicating that dihydroeugenol containing benzene ring functional groups is grafted onto the AFS molecular chain through chemical reaction.

[0102] Figure 3 The hydrogen nuclear magnetic spectrum of the air-entraining water-reducing agent (DAFS) prepared by the present invention is ( 1 H NMR) spectrum.

[0103] exist Figure 3 The H NMR spectrum shown ( 1 H NMR) showed that the chemical shifts of DAFS at δ = 6.55 to 6.73 were significantly increased with the characteristic nuclear magnetic absorption peaks of the H atoms of the benzene ring. In addition, due to the condensation of the alkyl chain onto the AFS molecular chain through formaldehyde, the CH 3 and CH 2 The characteristic peak intensity was significantly enhanced, further indicating that dihydroeugenol containing benzene ring functional groups was grafted onto the main chain of AFS molecules through chemical reaction.

[0104] Figure 4 The infrared spectrum (IR) of the anti-mud viscosity-reducing water-reducing agent (DPCE) prepared by the present invention.

[0105] Figure 4 The infrared spectroscopy (IR) characterization results shown in the figure show that compared with the polycarboxylate water reducer (PCE-S) synthesized without adding dihydroeugenol, the prepared anti-mud and viscosity-reducing polycarboxylate water reducer DPCE has a higher viscosity at 1600 cm -1 and 1510cm -1 The characteristic absorption peaks of benzene rings were newly added at two locations, indicating that the modified polyether D-HPEG synthesized from dihydroeugenol has been successfully grafted onto the DPCE molecular chain.

[0106] Figure 5 The nuclear magnetic hydrogen spectrum ( 1 H NMR) spectrum.

[0107] Figure 5 The H NMR spectrum shown ( 1 In the H NMR characterization results, DPCE has a new characteristic nuclear magnetic absorption peak of the benzene ring H atom at the chemical shift δ = 6.81 ~ 6.93 compared with PCE-S, which is consistent with the infrared spectrum characterization results, further indicating that the modified polyether D-HPEG synthesized from dihydroeugenol has been successfully grafted onto the DPCE molecular chain.

[0108] Example 1

[0109] The embodiment of the present application provides a concrete admixture suitable for high-altitude pumping, including air-entraining water-reducing agent (DAFS), anti-mud viscosity-reducing water-reducing agent (DPCE), defoamer, viscosity modifier (VMA), and retarder; wherein the defoamer is acrylic acid-modified silicone, the viscosity modifier is cellulose ether, and the retarder is sodium gluconate;

[0110] The mass ratio of air-entraining water-reducing agent (DAFS), anti-mud and viscosity-reducing water-reducing agent (DPCE), defoaming agent, viscosity modifier (VMA) and retarder is 1:0.7:0.005:0.005:0.01.

[0111] The embodiment of the present application also provides a machine-made sand concrete, which includes raw materials in the proportions shown in the following Table 1.

[0112] Table 1- High performance machine-made sand concrete mix ratio (kg / m 3 )

[0113]

[0114] The water reducing agent used in Table 1 is the concrete admixture suitable for high-altitude pumping in the above-mentioned Example 1.

[0115] Example 2

[0116] The embodiment of the present application provides a concrete admixture suitable for high-altitude pumping, including air-entraining water-reducing agent (DAFS), anti-mud viscosity-reducing water-reducing agent (DPCE), polyether defoaming agent, viscosity modifier (VMA), and retarder; the viscosity modifier is cellulose ether, and the retarder is sodium gluconate;

[0117] The mass ratio of air-entraining water-reducing agent (DAFS), anti-mud viscosity-reducing water-reducing agent (DPCE), polyether defoaming agent, viscosity modifier (VMA) and retarder is 1:0.9:0.006:0.005:0.02.

[0118] The embodiment of the present application also provides a machine-made sand concrete, which includes raw materials in the proportions shown in Table 2 below.

[0119] Table 2- High performance machine-made sand concrete mix ratio (kg / m 3 )

[0120]

[0121] The water reducing agent used in Table 2 is the concrete admixture suitable for high-altitude pumping in the above-mentioned Example 2.

[0122] Example 3

[0123] The embodiment of the present application provides a concrete admixture suitable for high-altitude pumping, including air-entraining water-reducing agent (DAFS), anti-mud viscosity-reducing water-reducing agent (DPCE), defoamer, viscosity modifier (VMA), and retarder; wherein the defoamer is acrylic acid-modified silicone, the viscosity modifier is cellulose ether, and the retarder is sodium gluconate;

[0124] The mass ratio of air-entraining water-reducing agent (DAFS), anti-mud viscosity-reducing water-reducing agent (DPCE), defoaming agent, viscosity modifier (VMA) and retarder is 1:1.1:0.004:0.007:0.015.

[0125] The embodiment of the present application also provides a machine-made sand concrete, which includes raw materials in the proportions shown in Table 3 below.

[0126] Table 3- High performance machine-made sand concrete mix ratio (kg / m 3 )

[0127]

[0128] The water reducing agent used in Table 3 is the concrete admixture suitable for high-altitude pumping in the above-mentioned Example 3.

[0129] Comparative Example 1

[0130] This comparative example provides a commercially available viscosity-reducing polycarboxylate water-reducing agent specially used for high-performance concrete.

[0131] The embodiment of the present application also provides a machine-made sand concrete, which includes raw materials in the proportions shown in Table 4 below.

[0132] Table 4 - Mix ratio of machine-made sand concrete (kg / m 3 )

[0133]

[0134] The water reducer used in Table 4 is the commercially available high-performance concrete-specific viscosity-reducing polycarboxylic acid water reducer in Comparative Example 1.

[0135] Comparative Example 2

[0136] This comparative example provides a water reducer, including PE200 general-purpose PCE water reducer produced by Wuhan Subo New Building Materials Co., Ltd., and an α-olefin sulfonate sodium air entraining agent (AOS) is added, and the amount used is 0.003% of the total mass of the cementitious material (the cementitious material is the mixture of cement, silica fume and fly ash microspheres mentioned in Table 5).

[0137] The embodiment of the present application also provides a machine-made sand concrete, which includes raw materials in the proportions shown in Table 5 below.

[0138] Table 5 - Mix ratio of machine-made sand concrete (kg / m 3 )

[0139]

[0140] Among them, the water reducing agent used in Table 5 is the water reducing agent in the above-mentioned Comparative Example 2.

[0141] The slump (mm), expansion (mm), air content (%), compressive strength (MPa), viscosity index, and autogenous shrinkage (με) of the machine-made sand concrete in test examples 1 to 3 and comparative examples 1 to 2 are shown in Table 6 below.

[0142] Table 6 - Performance of machine-made sand concrete in Examples 1 to 3 and Comparative Examples 1 to 2 Note: S0 in Table 6 represents the initial slump, S 60 represents the 1h slump, L0 represents the initial expansion, L 60 represents the expansion degree in 1h, A0 represents the initial gas content, A 60 Represents the gas content in 1 hour.

[0143] Figure 6 (a) adding the composite admixture of the present invention, corresponding to Example 1; (b) adding ordinary polycarboxylic acid water reducer, corresponding to Example 1.

[0144] The above results show that the admixture obtained by the present invention has the advantages of ultra-dispersion, small and stable bubbles, anti-mud and viscosity reduction, etc. At the same time, the admixture of the present invention can change the cement hydration process, regulate the concrete microstructure, and effectively ensure the mechanical properties and durability of concrete. Under the low pressure conditions in the west, the air entrainment rate of the machine-made sand concrete prepared by the admixture of the present invention is increased by more than 50% compared with the concrete prepared by ordinary admixtures. The high air content makes the concrete have excellent anti-freeze durability in the high-altitude areas in the west, and it also has greatly improved working performance, pumpability, anti-mud and viscosity reduction effect, compactness and volume stability. In addition, the invention of the admixture is of great significance for the preparation of high-toughness machine-made sand concrete used for large-span suspended arch bridges, and has important practical application value for the western development project.

[0145] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A concrete admixture suitable for high-altitude pumping, characterized in that: It includes air-entraining water-reducing agent; it also includes anti-mud and viscosity-reducing water-reducing agent, and the structural formula of the anti-mud and viscosity-reducing water-reducing agent is as follows: ； Wherein, a is a positive integer between 5 and 20, b is a positive integer between 20 and 100, c is a positive integer between 1 and 5, and n is a positive integer between 25 and 55; The structural formula of the air-entraining water reducer is as follows: ； Wherein, x is a positive integer between 30 and 80, and y is a positive integer between 20 and 70; The concrete admixture also includes a defoamer, a viscosity modifier, and a retarder; The mass ratio of the air-entraining water-reducing agent, the anti-mud and viscosity-reducing water-reducing agent, the defoaming agent, the viscosity modifier, and the retarder is 1:(0.6~1.2):(0.1~0.5):(0.03~0.07):(0.02~0.06).

2. The concrete admixture suitable for high-altitude pumping according to claim 1, characterized in that: The preparation method of the anti-mud viscosity-reducing water-reducing agent comprises the following steps: Using epichlorohydrin and methyl allyl polyoxyethylene ether as raw materials, methyl allyl polyoxyethylene chlorohydrin ether intermediate is prepared by ring-opening polymerization reaction; Using dihydroeugenol and methylallyl polyoxyethylene chlorohydrin ether intermediate as raw materials, dihydroeugenol grafted polyether macromonomer was prepared; The anti-mud and viscosity-reducing water-reducing agent was prepared with dihydroeugenol grafted polyether macromonomer, methyl allyl polyoxyethylene ether and acrylic acid as raw materials.

3. The concrete admixture suitable for high-altitude pumping as claimed in claim 2, characterized in that: After methyl allyl polyoxyethylene ether is heated and melted, boron trifluoride etherate is added, and epichlorohydrin is added dropwise at 55-65° C. to prepare methyl allyl polyoxyethylene chlorohydrin ether intermediate through ring-opening polymerization reaction; wherein the molar ratio of boron trifluoride etherate, epichlorohydrin, and methyl allyl polyoxyethylene ether is (0.03-0.05):(1.2-1.3):(0.9-1.1); After mixing dihydroeugenol and methyl allyl polyoxyethylene chlorohydrin ether intermediate, adjusting the pH to 12-13, reacting at 75-85°C to obtain dihydroeugenol grafted polyether macromonomer; The molar ratio of the dihydroeugenol to the methylallyl polyoxyethylene chlorohydrin ether intermediate is (0.8-1.2):(0.8-1.2).

4. The concrete admixture suitable for high-altitude pumping according to claim 1, characterized in that: The preparation method of the air-entraining water-reducing agent comprises the following steps: Sodium pyrosulfite and liquid alkali are added into water to react and obtain a sodium bisulfite solution; Acetone, dihydroeugenol and an auxiliary agent are added to a sodium bisulfite solution, and a sulfonation reaction occurs between the sodium bisulfite and the acetone to generate sodium α-olefin sulfonate; After the sulfonation reaction is completed, formaldehyde is added to carry out a condensation reaction. After the condensation reaction is completed, a foam stabilizer is added to obtain an air-entraining water-reducing agent.

5. The concrete admixture suitable for high-altitude pumping as claimed in claim 4, characterized in that: Sodium pyrosulfite and liquid alkali are added into water to obtain a saturated sodium bisulfite solution, acetone, dihydroeugenol and an auxiliary agent are added into the sodium bisulfite solution, and a sulfonation reaction is carried out at a temperature not higher than 55° C. to generate sodium α-olefin sulfonate; After the sulfonation reaction is completed, formaldehyde is added dropwise while maintaining the temperature unchanged. After the formaldehyde is added, the temperature is raised to 95-99°C for condensation reaction. After the condensation reaction is completed, a foam stabilizer is added to obtain an air-entraining water-reducing agent.

6. The concrete admixture suitable for high-altitude pumping as claimed in claim 4, characterized in that: The mass ratio of the dihydroeugenol, sodium pyrosulfite, acetone, formaldehyde and auxiliary agent is (10-15):(35-40):(45-55):(130-140):(1-5); The liquid alkali includes at least one of a sodium hydroxide solution and a potassium hydroxide solution.

7. Use of the concrete admixture as claimed in any one of claims 1 to 6 in preparing high-altitude pumped machine-made sand concrete.

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