Low temperature shrinkage reducing admixture and method of manufacture

Abstract

The application belongs to the technical field of concrete admixtures, and discloses a low-temperature shrinkage reducing agent and a preparation method. The technical problems of poor stability of an ordinary compound polycarboxylic acid shrinkage reducing agent, poor concrete compressive strength, low shrinkage performance and poor concrete crack resistance caused by use of the polycarboxylic acid shrinkage reducing agent in a low-temperature environment are effectively solved. Therefore, the modified alcohol ether is copolymerized with a polyether macromonomer and acrylic acid, and is supplemented with an amide functional small monomer and a reaction aid by using an oxidation-reduction initiation system to synthesize a shrinkage reducing agent with a polycarboxylic acid structure in an aqueous solution. When the shrinkage reducing agent is mixed into concrete in a low-temperature environment, the water retention of the concrete is enhanced, the concrete shrinkage rate is improved, and the crack resistance of the concrete is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete admixtures, in particular to a low-temperature shrinkage reducing agent and a preparation method thereof. BACKGROUND

[0002] Concrete shrinkage cracks not only affect the aesthetics of construction engineering, but also reduce the strength of concrete engineering structure, and have an adverse effect on the integrity, water tightness and durability of the construction engineering, greatly shortening the service life of the construction engineering.

[0003] Among the various emerging admixtures at present, the polycarboxylic high-performance shrinkage reducing agent has the characteristics of high water-reducing rate, good slump retention performance, green environmental protection, etc., and is widely used in high-speed railways, bridges, water conservancy, commercial concrete, fabricated buildings and concrete prefabricated components, etc. With the development of concrete technology, the polycarboxylic shrinkage reducing agent has become an indispensable component in concrete.

[0004] The local areas of severe cold regions, cold regions and hot summer and cold winter regions in China will successively enter the winter construction and the cold time is long. Compared with the ordinary normal maintenance concrete, the strength of the frozen concrete will be reduced by 20% to 40%. In order to prevent the concrete from being frozen, the ordinary polycarboxylic shrinkage reducing agent will freeze and solidify into a polycarboxylic water-reducing agent ice-water mixture, losing fluidity in a low-temperature environment, especially below-10 DEG C. Therefore, some inorganic salts are compounded in the polycarboxylic shrinkage reducing agent so as to be able to be constructed in the cold winter in the severe cold region. However, when the inorganic salt is physically compounded with the polycarboxylic shrinkage reducing agent, delamination, gas expansion and poor storage stability are prone to occur, which greatly reduces the concrete shrinkage, causes the concrete anti-cracking performance and the compressive strength to be poor, and further reduces the durability of the concrete. SUMMARY

[0005] Therefore, the present application provides a low-temperature shrinkage reducing agent and a preparation method thereof, which are suitable for the cold winter in the severe cold region, and can effectively solve the technical problems of poor stability of the ordinary compounded polycarboxylic shrinkage reducing agent, poor concrete compressive strength and low shrinkage performance when used in a low-temperature environment, and poor concrete anti-cracking performance.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A low-temperature shrinkage reducing agent is prepared from the following raw materials by weight: modified alcohol ether 5-10 parts, polyether macromonomer 50-60 parts, acrylic acid 4-6 parts, amide compound 0.2-0.4 parts, initiator 0.3-0.6 parts, chain transfer agent 0.1-0.3 parts, reducing agent 0.03-0.05 parts, 1% ferrous sulfate aqueous solution 0.4-0.7 parts, appropriate amount of pH adjuster and deionized water.

[0008] In a further technical solution of the present application, the polyether macro-monomer is a methyl allyl polyoxyethylene ether.

[0009] In a further technical solution of the present application, the initiator is hydrogen peroxide or ammonium persulfate.

[0010] In a further technical solution of the present application, the chain transfer agent is one of sodium hypophosphite, mercaptoethanol and mercaptopropionic acid.

[0011] In a further technical solution of the present application, the reducing agent is succinic acid dioctyl ester sulfonate sodium or vitamin C.

[0012] In a further technical solution of the present application, the amide compound is one of N-hydroxymethyl acrylamide, acrylamide and 2-acrylamide-2-methylpropane sulfonic acid.

[0013] In a further technical solution of the present application, the pH regulator is a 30% sodium hydroxide solution.

[0014] In a further technical solution of the present application, the modified alcohol ether has the following structural formula:

[0015]

[0016] In a further technical solution of the present application, the modified alcohol ether is modified from an unsaturated alcohol ether compound.

[0017] Further, in a further technical solution of the present application, the unsaturated alcohol ether compound is one of vinyl glycol ether and vinyl diethylene glycol ether.

[0018] In a further technical solution of the present application, the preparation method of the low-temperature shrinkage reducing agent is as follows:

[0019] S1, the modified alcohol ether, the polyether macro-monomer, the acrylic acid, the amide compound, the initiator, the chain transfer agent, the reducing agent and the 1% ferrous sulfate aqueous solution are weighed according to different weight fractions;

[0020] S2, the polyether macro-monomer and deionized water are added to the reaction kettle at room temperature and normal pressure, stirred uniformly, prepared into a solution with a concentration of 55-65%, the temperature in the kettle is raised to 40-45 DEG C and kept constant, then the initiator, half weight of the acrylic acid and the 1% ferrous sulfate aqueous solution are added, stirred for 5-7 min, and standby;

[0021] S3, the chain transfer agent and the reducing agent are mixed and added to deionized water to prepare A liquid with a concentration of 55-65% at room temperature and normal pressure;

[0022] S4, under room temperature and normal pressure, the modified alcohol ether, the remaining half of the weight of the acrylic acid, and the amide compound are added into the deionized water to form the B liquid with a concentration of 0.1-1%;

[0023] S5, the A liquid and the B liquid are sequentially and slowly added into the reaction kettle, the A liquid is added for 170-180 min, the B liquid is added for 160-170 min, after the addition is completed, the reaction is kept for 1.5-2.5 h to complete the polymerization, and after the reaction is completed, the temperature is kept for 1 h;

[0024] S6, after the keeping is completed, the pH regulator is slowly and dropwisely added, the pH of the mixed solution is adjusted to 5-7, the temperature is reduced to room temperature, and the deionized water is added to dilute to the designed concentration, so that the low-temperature shrinkage reducing agent is obtained.

[0025] According to the technical solution, compared with the prior art, the low-temperature shrinkage reducing agent and the preparation method have the following beneficial effects:

[0026] 1, the modified alcohol ether is used, the polyether macromonomer is copolymerized with the acrylic acid, and then the amide functional small monomer and the reaction aid are used to synthesize the shrinkage reducing agent with the polycarboxylic acid structure in the aqueous solution by using the oxidation-reduction initiation system, through the anti-freezing test, the shrinkage reducing agent prepared by the application still has the flowability at-10℃ to-40℃, is suitable for the cold winter in the severe cold area, and can overcome the problem that the ordinary polycarboxylic acid shrinkage reducing agent is not convenient to apply in the winter in the area.

[0027] 2, the low-temperature synthesis process is adopted, the energy consumption is low, the storage stability is good, the harm to the production and construction personnel and the environment is small, the production process of the application is simple, large-scale production is suitable, and the economic benefit and the environmental benefit are considerable.

[0028] 3, compared with the prior art, the structure of the alcohol ether small monomer is modified, the unsaturated small molecule alcohol ether is modified by 2-naphthol-3, 6-disulfonic acid, the dehydration reaction occurs between the hydroxyl group at the tail end of the unsaturated alcohol ether and the modified alcohol ether compound under the heating condition,

[0029]

[0030] In the low-temperature environment, the modified alcohol ether compound prepared by the application can be well dissolved in water due to the polyether bond, and has low surface tension; and can further prevent the shrinkage cracks caused by the water loss of the concrete.

[0031] 4. The addition of a naphthalene-based aromatic ring to the modified alcohol ether compound prepared in this invention increases the steric hindrance of the side chains, thereby improving the dispersibility of the prepared shrinkage-reducing agent. Furthermore, the rigid structure of the naphthalene ring enhances the compressive strength of concrete. Additionally, the introduced sulfonic acid group is a strongly hydrophilic group; in low-temperature environments, the sulfonic acid group effectively adsorbs free water molecules around the side chains of the polyether, improving dispersion and lubrication performance, locking in most of the free water inside the concrete, reducing internal water freezing, and providing excellent water retention. This enhances the shrinkage-reducing properties of concrete and reduces cracking at low temperatures. Experimental results show that adding the modified alcohol ether shrinkage-reducing agent prepared in this invention resulted in shrinkage rates of 31.97% and 29.96% for concrete at 7 days and 28 days, respectively, in a low-temperature environment (-10℃), significantly higher than the shrinkage-reducing performance of commercially available shrinkage-reducing agents. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available products or conventional processing techniques in the art.

[0034] The polyether macromonomers, acrylic acid, amide compounds, initiators, chain transfer agents, and reducing agents used in this invention are all industrial grade.

[0035] This invention provides a low-temperature shrinkage reducing agent and its preparation method. The low-temperature shrinkage reducing agent is prepared from the following raw materials in parts by weight: 5-10 parts modified alcohol ether, 50-60 parts polyether macromonomer, 4-6 parts acrylic acid, 0.2-0.4 parts amide compound, 0.3-0.6 parts initiator, 0.1-0.3 parts chain transfer agent, 0.03-0.05 parts reducing agent, 0.4-0.7 parts 1% ferrous sulfate aqueous solution, appropriate amount of pH adjuster and deionized water.

[0036] In a further technical solution of the present invention, the specific polyether macromonomer is methyl allyl polyoxyethylene ether; the specific initiator is hydrogen peroxide or ammonium persulfate; the specific chain transfer agent is one of sodium hypophosphite, mercaptoethanol, and mercaptopropionic acid; the specific reducing agent is sodium dioctyl succinate sulfonate or vitamin C; the specific amide compound is one of N-hydroxymethylacrylamide, acrylamide, and 2-acrylamide-2-methylpropanesulfonic acid; and the specific pH adjuster is a 30% sodium hydroxide solution.

[0037] The preparation method of the modified alcohol ether is as follows: 2-naphthol-3,6-disulfonic acid and an unsaturated alcohol ether compound are mixed in a mass ratio of 1-2:9-10, and reacted at 120-125°C for 1.5-2h to obtain the modified alcohol ether.

[0038] The reaction process is as follows:

[0039]

[0040] The preparation method of the low-temperature shrinkage reducing agent comprises the following steps:

[0041] S1, 5-10 parts of modified alcohol ether, 50-60 parts of polyether macromonomer, 4-6 parts of acrylic acid, 0.2-0.4 parts of amide compound, 0.3-0.6 parts of initiator, 0.1-0.3 parts of chain transfer agent, 0.03-0.05 parts of reducing agent, and 0.4-0.7 parts of 1% ferrous sulfate aqueous solution are weighed;

[0042] S2, the polyether macromonomer and deionized water are added to the reaction kettle at room temperature and normal pressure, stirred uniformly, prepared into a solution with a concentration of 55-65%, the temperature in the kettle is raised to 40-45°C and kept constant, then the initiator, half of the weight of the acrylic acid and 1% ferrous sulfate aqueous solution are added, stirred for 5-7min, and standby;

[0043] S3, the chain transfer agent and the reducing agent are mixed and added to deionized water to prepare A liquid with a concentration of 55-65% at room temperature and normal pressure;

[0044] S4, the modified alcohol ether, the remaining half of the weight of the acrylic acid, and the amide compound are added to deionized water to prepare B liquid with a concentration of 0.1-1% at room temperature and normal pressure;

[0045] S5, A liquid and B liquid are sequentially and slowly added to the reaction kettle, the dropping time of A liquid is 170-180min, and the dropping time of B liquid is 160-170min; after the dropping is completed, the polymerization is completed by keeping the reaction for 1.5-2.5h, and after the reaction is completed, the temperature is kept for 1h; wherein the dropping of A liquid and B liquid uses peristaltic pump, and every 30min during the dropping process, it is confirmed whether the liquid level meets the requirements, and if not, the frequency conversion of the peristaltic pump is adjusted in time, so that the adjusted dropping time meets the requirements;

[0046] S6, after the keeping is completed, the pH regulator is slowly added drop by drop, the pH of the mixed solution is adjusted to 5-7, the temperature is reduced to room temperature, deionized water is added to dilute to the designed concentration, and the low-temperature shrinkage reducing agent of the application is obtained; the keeping time is calculated after the dropping of B liquid is completed, and the temperature control is required during the keeping process.

[0047] The application will be further described below in combination with specific examples

[0048] Example 1

[0049] A low-temperature shrinkage-reducing agent and a preparation method thereof, which are prepared from the following raw materials in parts by weight: modified alcohol ether 5 parts, methyl allyl polyoxyethylene ether 50 parts, acrylic acid 4 parts, N-methylol acrylamide 0.2 parts, hydrogen peroxide 0.3 parts, sodium hypophosphite 0.1 part, succinic acid dioctyl ester sulfonate sodium 0.03 parts, 1% ferrous sulfate aqueous solution 0.4 parts, 30% sodium hydroxide solution and deionized water.

[0050] The preparation method of the modified alcohol ether is as follows: 3 parts of 2-naphthol-3,6-disulfonic acid and 27 parts of vinyl glycol ether are mixed and reacted at 120°C for 1.5 hours to obtain the modified alcohol ether.

[0051]

[0052] The preparation method of the low-temperature shrinkage-reducing agent comprises the following steps:

[0053] S1, the modified alcohol ether 5 parts, methyl allyl polyoxyethylene ether 50 parts, acrylic acid 4 parts, acrylamide 0.2 parts, hydrogen peroxide 0.3 parts, sodium hypophosphite 0.1 part, succinic acid dioctyl ester sulfonate sodium 0.03 parts, 1% ferrous sulfate aqueous solution 0.4 parts are weighed in parts by weight;

[0054] S2, the methyl allyl polyoxyethylene ether and deionized water are added to the reaction kettle at room temperature and normal pressure, stirred uniformly, prepared into a solution with a concentration of 55%, the temperature in the kettle is raised to 40°C and kept constant, then the hydrogen peroxide, half of the weight of the acrylic acid and the 1% ferrous sulfate aqueous solution are added, stirred for 5 minutes and standby;

[0055] S3, the sodium hypophosphite and the succinic acid dioctyl ester sulfonate sodium are mixed and added to the deionized water to prepare A liquid with a concentration of 55% at room temperature and normal pressure;

[0056] S4, the modified alcohol ether, the remaining half of the weight of the acrylic acid and the acrylamide are added to the deionized water to prepare B liquid with a concentration of 0.1% at room temperature and normal pressure;

[0057] S5, the A liquid and the B liquid are sequentially and slowly added dropwise into the reaction kettle, the A liquid is added dropwise for 170 minutes, the B liquid is added dropwise for 160 minutes, after the addition is completed, the reaction is kept for 1.5 hours to complete the polymerization, and after the reaction is completed, the temperature is kept for 1 hour;

[0058] S6, after the keeping is completed, the 30% sodium hydroxide solution is slowly and dropwise added, the pH of the mixed solution is adjusted to 5, the temperature is reduced to room temperature, and the deionized water is added to dilute to a solid content of 40%, thereby obtaining the low-temperature shrinkage-reducing agent.

[0059] Example 2

[0060] A low temperature shrinkage reducing agent and a preparation method thereof, which are prepared from the following raw materials in parts by weight: modified alcohol ether 10 parts, methyl allyl polyoxyethylene ether 60 parts, acrylic acid 6 parts, N-methylol acrylamide 0.4 parts, ammonium persulfate 0.6 parts, sodium hypophosphite 0.3 parts, succinic acid dioctyl ester sulfonate sodium 0.05 parts, and 1% ferrous sulfate aqueous solution 0.7 parts;

[0061] The preparation method of the modified alcohol ether is as follows: 2 parts of 2-naphthol-3,6-disulfonic acid and 10 parts of vinyl diethylene glycol ether are mixed and reacted at 125 DEG C for 2 hours to obtain the modified alcohol ether.

[0062]

[0063] The preparation method of the low temperature shrinkage reducing agent comprises the following steps:

[0064] S1, the modified alcohol ether 10 parts, methyl allyl polyoxyethylene ether 60 parts, acrylic acid 6 parts, 2-acrylamide-2-methylpropane sulfonic acid 0.4 parts, ammonium persulfate 0.6 parts, mercaptopropionic acid 0.3 parts, and vitamin C 0.05 parts are weighed in parts by weight;

[0065] S2, the methyl allyl polyoxyethylene ether and deionized water are added into a reaction kettle at room temperature and normal pressure, stirred uniformly, prepared into a solution with a concentration of 65%, the temperature in the kettle is raised to 45 DEG C and kept constant, then the ammonium persulfate, half of the weight of the acrylic acid and the 1% ferrous sulfate aqueous solution are added, stirred for 7 minutes, and standby;

[0066] S3, the vitamin C and the mercaptopropionic acid are mixed and added into deionized water to prepare A liquid with a concentration of 65% at room temperature and normal pressure;

[0067] S4, the modified alcohol ether, the remaining half of the weight of the acrylic acid and 2-acrylamide-2-methylpropane sulfonic acid are added into deionized water to prepare B liquid with a concentration of 1% at room temperature and normal pressure;

[0068] S5, the A liquid and the B liquid are sequentially and slowly added dropwise into the reaction kettle, the dropwise adding time of the A liquid is 180 minutes, the dropwise adding time of the B liquid is 170 minutes, after the dropwise adding is completed, the polymerization is completed by keeping the reaction for 2.5 hours, and after the reaction is completed, the temperature is kept for 1 hour;

[0069] S6, after the keeping is completed, the pH regulator is slowly and dropwise added, the pH of the mixed solution is adjusted to 7, the temperature is reduced to room temperature, deionized water is added for dilution until the solid content is 40%, and thus the low temperature shrinkage reducing agent of the application is obtained.

[0070] Example 3

[0071] A low temperature shrinkage reducing agent and a preparation method thereof, which are prepared from the following raw materials in parts by weight: modified alcohol ether 7.5 parts, methyl allyl polyoxyethylene ether 55 parts, acrylic acid 5 parts, N-methylol acrylamide 0.3 parts, hydrogen peroxide 0.45 parts, sodium hypophosphite 0.2 parts, succinic acid dioctyl ester sulfonic sodium 0.04 parts, and 1% ferrous sulfate aqueous solution 0.55 parts;

[0072] The preparation method of the modified alcohol ether is as follows: 3 parts of 2-naphthol-3,6-disulfonic acid and 27 parts of vinyl glycol ether are mixed and reacted at 120 DEG C for 2 hours to obtain the modified alcohol ether.

[0073]

[0074] The preparation method of the low temperature shrinkage reducing agent comprises the following steps:

[0075] S1, the modified alcohol ether 7.5 parts, methyl allyl polyoxyethylene ether 55 parts, acrylic acid 5 parts, N-methylol acrylamide 0.3 parts, hydrogen peroxide 0.45 parts, sodium hypophosphite 0.2 parts, succinic acid dioctyl ester sulfonic sodium 0.04 parts, and 1% ferrous sulfate aqueous solution 0.55 parts are weighed in parts by weight;

[0076] S2, the methyl allyl polyoxyethylene ether and deionized water are added into a reaction kettle at room temperature and normal pressure, stirred uniformly, prepared into a solution with a concentration of 60%, the temperature in the kettle is raised to 42 DEG C and kept constant, then the hydrogen peroxide, half of the weight of the acrylic acid and the 1% ferrous sulfate aqueous solution are added, stirred for 6 minutes, and standby;

[0077] S3, the sodium hypophosphite and the succinic acid dioctyl ester sulfonic sodium are mixed and added into deionized water to prepare A liquid with a concentration of 60% at room temperature and normal pressure;

[0078] S4, the modified alcohol ether, the remaining half of the weight of the acrylic acid and N-methylol acrylamide are added into deionized water to prepare B liquid with a concentration of 0.5% at room temperature and normal pressure;

[0079] S5, the A liquid and the B liquid are sequentially and slowly added dropwise into the reaction kettle, the A liquid is added dropwise for 175 minutes, the B liquid is added dropwise for 165 minutes, after the addition is completed, the reaction is kept for 2 hours to complete polymerization, and after the reaction is completed, the temperature is kept for 1 hour;

[0080] S6, after the keeping is completed, the pH regulator is slowly and dropwise added, the pH of the mixed solution is adjusted to 6, the temperature is reduced to room temperature, deionized water is added for dilution to obtain the low temperature shrinkage reducing agent with a solid content of 40%.

[0081] The low temperature shrinkage reducing agent prepared in Example 3 of the present application and a common polycarboxylic acid shrinkage reducing agent (PCE-3 solid content 40%, water-reducing rate 31%, Harbin China Communications Civil Engineering Materials Co., Ltd.) were respectively filled in mineral water bottles and subjected to anti-freezing performance test in an ultra-low temperature electric refrigerator at -40 to 0℃. It was found through the test that the common polycarboxylic acid shrinkage reducing agent PCE-3 was frozen and solidified at -10℃ to form a polycarboxylic acid shrinkage reducing agent ice-water mixture; while the low temperature shrinkage reducing agent prepared in Example 3 of the present application was still in liquid state in the environment of -10 to -40℃, but the liquid was relatively viscous at -40℃.

[0082] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0083] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

[0084] Table 1 C50 precast concrete mix proportion

[0085] Raw material name Specification kg / m 3 ]] P·O42.5 cement P·O42.5 325 Sand Natural medium sand 770 Small broken stone 5-15mm 225 Large broken stone 15-20mm 900 Fly ash Grade II 65 Slag S95 grade 40 Water Tap water 145

[0086] Table 2 Performance test related standard specifications adopted

[0087]

[0088] Performance test method

[0089] Table 3 is the comparison of 1h and 2h fluidity and loss rate of cement paste of commercially available shrinkage reducing agent and shrinkage reducing agent prepared in Examples 1-3.

[0090] Table 4 is the compressive strength of concrete of commercially available shrinkage reducing agent and shrinkage reducing agent prepared in Examples 1-3, and the mix proportion of C50 concrete is shown in Table 1.

[0091] Table 5 is the shrinkage rate of concrete of commercially available shrinkage reducing agent and shrinkage reducing agent prepared in Examples 1-3, and the mix proportion of C50 concrete is shown in Table 1.

[0092] Table 6 is the surface tension test result of 10% mass concentration solution prepared by using existing commonly used alcohol ether component compounds (triethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, diethylene glycol monomethyl ether, polyethylene glycol monomethyl ether, vinyl glycol ether and modified alcohol ether prepared in Example 3 of the present application).

[0093] The commercially available shrinkage reducing agent is: ordinary polycarboxylic acid shrinkage reducing agent (PCE-3 solid content 40%, water-reducing rate 31% at room temperature, Harbin Municipal Communications Civil Engineering Materials Co., Ltd.)

[0094] Table 3 cement paste test results

[0095]

[0096] Table 4 concrete compressive strength

[0097]

[0098] Table 5 concrete shrinkage rate

[0099]

[0100] Table 6 comparison of surface tension of single alcohol ether component

[0101]

[0102] Through testing, compared with the commercially available shrinkage reducing agent, the cement paste 1h flow loss rate of the shrinkage reducing agent prepared by the application is less than 10%, and the 2h loss rate is as low as 24.9%, which indicates that the later coagulation speed is faster, and it is indicated that the shrinkage reducing agent prepared by the application can well improve the flow performance of the concrete.

[0103] Through testing, compared with the commercially available shrinkage reducing agent, in a low temperature environment (-10℃), the 1d compressive strength of the concrete mixed with the low temperature shrinkage reducing agent prepared by the application of example 3 is 19.5MPa, and the compressive strength after 28d curing is 58.4MPa, and the compressive strength ratio is 33.4%.

[0104] Through testing, compared with the application of other alcohol ether components, the 7d and 28d shrinkage rates of the concrete mixed with the modified alcohol ether compound prepared by the application are significantly improved in a normal temperature environment (20℃), and are 32.56% and 30.96% respectively; in a low temperature environment (-10℃), the 7d and 28d shrinkage rates of the concrete are slightly decreased, but the shrinkage rates are 31.97% and 29.96% respectively, which are obviously higher than the shrinkage performance of the commercially available shrinkage reducing agent.

[0105] Through testing, the surface tension of the alcohol ether component compound is in the range of 29.05-48.27mN / m, and the surface tension of the modified alcohol ether prepared by the application of example 3 is the lowest, which is 29.05mN / m.

[0106] The test results of shrinkage and surface tension show that the addition of the shrinkage reducing agent prepared in Example 3 of the present application improves the water retention and the crack resistance of the concrete in a low temperature environment.

Claims

1. A low-temperature shrinkage reducing agent, characterized in that, It is prepared from the following raw materials in parts by weight: 5-10 parts modified alcohol ether, 50-60 parts polyether macromonomer, 4-6 parts acrylic acid, 0.2-0.4 parts amide compound, 0.3-0.6 parts initiator, 0.1-0.3 parts chain transfer agent, 0.03-0.05 parts reducing agent, 0.4-0.7 parts 1% ferrous sulfate aqueous solution, appropriate amount of pH adjuster and deionized water; The modified alcohol ether has the following structural formula: The modified alcohol ether is an unsaturated alcohol ether compound that has been modified. The modified alcohol ether is prepared by mixing 2-naphthol-3,6-disulfonic acid and unsaturated alcohol ether compound in a mass ratio of 1-2:9-10 and reacting at 120-125℃ for 1.5-2 hours to obtain the modified alcohol ether. The unsaturated alcohol ether compound is one of vinyl glycol ether and vinyl diethylene glycol ether.

2. The low-temperature shrinkage reducing agent according to claim 1, characterized in that, The polyether macromonomer is methyl allyl polyoxyethylene ether.

3. The low-temperature shrinkage reducing agent according to claim 1, characterized in that, The initiator is hydrogen peroxide or ammonium persulfate; the chain transfer agent is one of sodium hypophosphite, mercaptoethanol, or mercaptopropionic acid; the reducing agent is sodium dioctyl succinate sulfonate or vitamin C; and the amide compound is one of N-hydroxymethylacrylamide, acrylamide, or 2-acrylamide-2-methylpropanesulfonic acid.

4. The low-temperature shrinkage reducing agent according to claim 1, characterized in that, The pH adjuster is a 30% sodium hydroxide solution.

5. A method for preparing a low-temperature shrinkage reducing agent according to any one of claims 1 to 4, characterized in that: S1. Weigh the modified alcohol ether, polyether macromonomer, acrylic acid, amide compound, initiator, chain transfer agent, reducing agent, and 1% ferrous sulfate aqueous solution according to different weight parts; S2. At room temperature and normal pressure, add polyether macromonomer and deionized water to the reactor, stir evenly, and prepare a solution with a concentration of 55-65%. Raise the temperature inside the reactor to 40-45℃ and keep it constant. Then add initiator, half the weight of acrylic acid and 1% ferrous sulfate aqueous solution, stir for 5-7 minutes, and set aside. S3. At room temperature and normal pressure, mix the chain transfer agent and reducing agent and add them to deionized water to prepare solution A with a concentration of 55-65%. S4. At room temperature and normal pressure, add the modified alcohol ether, the remaining half of the weight of acrylic acid and amide compounds to deionized water to prepare solution B with a concentration of 0.1-1%. S5. Slowly add liquid A and liquid B dropwise into the reactor in sequence. The dropwise addition time for liquid A is 170-180 min, and the dropwise addition time for liquid B is 160-170 min. After the dropwise addition is completed, keep the reactor at the temperature for 1.5-2.5 h to complete the polymerization. After the reaction is completed, keep the reactor at the temperature for 1 h. S6. After the heat preservation is completed, slowly add pH adjuster dropwise to adjust the pH of the mixed solution to 5-7. After the temperature drops to room temperature, dilute with deionized water to the designed concentration to obtain the low temperature shrinkage reducer.

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