A preparation method of antifreeze type high-dispersion water reducing agent

Abstract

The invention discloses a method for preparing an antifreeze type highly dispersible water reducing agent, which belongs to the field of concrete water reducing agents. The preparation method comprises preparing amino acid grafted triterpenoid saponin, methylation treatment, and mixing to prepare an aerated water reducing agent. The water reducing agent prepared by the invention can enable concrete to obtain excellent antifreeze properties in a medium with a high salt content.

Description

Technical Field

[0001] The invention relates to a preparation method of an antifreeze type high-dispersion water reducing agent, and belongs to the field of concrete water reducing agents. Background Art

[0002] The frost resistance of concrete refers to the performance of saturated concrete in resisting freeze-thaw cycles. The saturated state of concrete and freeze-touch cycles are necessary conditions for the occurrence of freeze-thaw damage to concrete. Therefore, freeze-thaw damage to concrete generally occurs in concrete structures that are frequently in contact with water in cold areas, such as seawater in water level change areas, hydraulic concrete structures, etc.

[0003] Most of the water conservancy dams in Northeast my country, North China and Northwest China, especially the concrete structures in the extremely cold Northeast China, have suffered varying degrees of freeze-thaw damage in some or all areas. Some projects have been found to have suffered serious freeze damage during construction or shortly after completion. Investigations have found that freeze-thaw damage to concrete exists not only in the "Three Norths" region, but also in the central region north of the Yangtze River and south of the Yellow River. Concrete durability is one of the most important components in the field of concrete at home and abroad today, and it is also one of the most serious problems facing concrete projects in northern my country.

[0004] There are two main methods to improve the antifreeze performance of concrete. One is to add antifreeze admixtures to the water reducer. Commonly used antifreeze agents are inorganic salt antifreeze agents, such as calcium chloride, calcium nitrate, and calcium nitrite. Such antifreeze agents will cause the slump loss of concrete, and if the dosage is too high, it will aggravate the peeling phenomenon of the concrete surface in the salt freezing environment. The other is to add air entraining agent admixtures to the water reducer. Air entraining agent, also known as air entraining agent, is a hydrophobic surfactant. It is added to the concrete mixture and introduces a large number of evenly distributed, closed and stable tiny bubbles during the mixing process. It will prevent moisture from penetrating into the concrete through the capillary channels during the freeze-thaw cycle, thereby preventing the destruction of the concrete.

[0005] Triterpenoid saponin is a nonionic surfactant and belongs to the saponin class of air-entraining agents. When dissolved in water, it forms an arrangement of two groups, which greatly reduces the surface tension between gas and liquid, easily generates bubbles, has a good air-entraining effect, and is very popular in industry.

[0006] Air-entraining water-reducing agent improves the antifreeze performance of concrete mainly from two aspects. In addition to forming closed tiny bubbles in the concrete, it also increases the strength of the concrete so that the force generated by the freeze-thaw cycle will not destroy the concrete's own strength. However, there is another problem with air-entraining water-reducing agent. The increase in the air content of concrete will cause the strength of the concrete to decrease to a certain extent, thereby weakening the effect of the water-reducing agent on the strength of the concrete. When the air content of concrete is about 6%, the concrete can obtain a more effective antifreeze effect in a non-seawater environment. However, in a seawater environment, due to the presence of salt substances such as sodium chloride and sodium sulfate, the frost resistance of the concrete is still poor, especially when the dynamic modulus drops to 80%, the destruction of the concrete accelerates sharply. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the defects of the prior art. By specially treating triterpenoid saponins with air entraining effect and then mixing them with polycarboxylic acid water reducer to prepare a composite water reducer, the concrete can have excellent antifreeze performance in a medium with high salt content such as seawater, and at the same time, the weakening effect of concrete strength caused by the air entraining effect can be alleviated.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A method for preparing an antifreeze type highly dispersed water reducing agent comprises preparing amino acid grafted triterpenoid saponin, methylating and mixing to prepare an aerated water reducing agent.

[0010] The following are further improvements to the above technical solution:

[0011] The method for preparing amino acid-grafted triterpenoid saponin comprises: mixing triterpenoid saponin with a sodium hydroxide solution having a concentration of 0.45-0.55wt%, stirring to completely dissolve the triterpenoid saponin solution for standby use; mixing arginine with a sodium hydroxide solution having a concentration of 0.45-0.55wt%, stirring to completely dissolve the triterpenoid saponin solution; adding the obtained arginine solution to the triterpenoid saponin solution, stirring to uniformly mix the solution; heating the solution to 85-92°C; adding formaldehyde solution; controlling the adding time to be 12-17min; maintaining the temperature at 85-92°C after the adding is completed; stirring the solution for 230-260min; and using a rotary evaporator to evaporate water to obtain amino acid-grafted triterpenoid saponin;

[0012] The mass ratio of the triterpenoid saponin to the sodium hydroxide solution is 1:(11-13);

[0013] The mass ratio of arginine to sodium hydroxide solution is 1:(6.5-7.5);

[0014] The mass ratio of the arginine solution, the triterpenoid saponin solution and the formaldehyde solution is (2.5-3.5): (0.9-1.1): (0.9-1.1);

[0015] The concentration of the formaldehyde solution is 22-27 wt %.

[0016] The methylation treatment method comprises mixing the amino acid grafted triterpenoid saponin with deionized water, stirring evenly, adding trimethyl phosphate, controlling the adding time to be 8-12 minutes, adjusting the pH to be 12.2-12.7, controlling the temperature to be 130-140° C., stirring, and stirring for 70-90 minutes, and after stirring, using a 500Da dialysis bag for purification by dialyzing, and the purification time is 24 hours. After the dialysis is completed, the methylated amino acid grafted triterpenoid saponin is obtained;

[0017] The mass ratio of the amino acid grafted triterpenoid saponin, deionized water and trimethyl phosphate is (4.5-5.5): (135-165): (34-42).

[0018] The method for preparing the air-entraining water-reducing agent by mixing is as follows: mixing the methylated amino acid-grafted triterpenoid saponin with an ethanol aqueous solution, stirring to completely dissolve it, then adding a polycarboxylic acid water-reducing agent powder crushed to a fineness of 500 meshes and sodium carboxymethyl cellulose, stirring to mix them evenly, obtaining a mixed solution, then controlling the temperature to 120° C., drying the mixed solution for 12 hours, and after the drying is completed, crushing the dried product to 500 meshes to obtain an antifreeze type highly dispersed water-reducing agent;

[0019] The model of the polycarboxylic acid water reducer is PC-1009, and the water reduction rate is 25%;

[0020] The mass ratio of the amino acid grafted triterpenoid saponin, ethanol aqueous solution, polycarboxylic acid water reducer powder, and sodium carboxymethyl cellulose is (4.5-5.5): (50-70): (32-42): (6-8);

[0021] The concentration of the ethanol aqueous solution is 35-45wt%.

[0022] Compared with the prior art, the present invention achieves the following beneficial effects:

[0023] The water reducing agent prepared by the present invention has a high water reducing rate. The water reducing agent of the present invention is added in an amount of 0.55wt% of the gel material, and the water reducing rate of the water reducing agent at this dosage is tested according to the method in GB8076-2008, and the water reducing rate is 31.4-32.0%;

[0024] The water reducer prepared by the present invention has a good air entraining effect. The water reducer of the present invention is added in an amount of 0.55wt% of the gel material, and the air content of the water reducer at this dosage is tested according to the method in GB8076-2008, and the air content is 5.7-5.8%;

[0025] The water-reducing agent prepared by the present invention can enable concrete to obtain excellent antifreeze performance. The water-reducing agent of the present invention is added in an amount of 0.55wt% of the gel material. According to the method in GB / T 50082-2009, the quick freezing method is adopted to test the relative dynamic modulus loss rate and mass loss rate of the test piece after 300, 400 and 500 freeze-thaw cycles respectively. The relative dynamic modulus loss rate after 300 freeze-thaw cycles is 0.33-0.57%, and the mass loss rate is 0.56-0.71%; the relative dynamic modulus loss rate after 400 freeze-thaw cycles is 0.44-0.64%, and the mass loss rate is 0.61-0.88%; the relative dynamic modulus loss rate after 500 freeze-thaw cycles is 0.79-0.98%, and the mass loss rate is 0.79-1.03%;

[0026] The water reducer prepared by the present invention can enable concrete to obtain excellent antifreeze performance in a medium with a high salt content. The water reducer of the present invention is added in an amount of 0.55wt% of a gel material, and according to the method in GB / T 50082-2009, a quick freezing method is adopted, and the erosion medium is respectively a 3.5wt% sodium chloride solution, a 5wt% sodium sulfate solution, and seawater. The relative dynamic modulus loss rate and the mass of the peeling material of the test piece after 300 and 500 freeze-thaw cycles in different media are tested respectively. In the 3.5wt% sodium chloride solution, the relative dynamic modulus loss rate after 300 freeze-thaw cycles is 1.08-1.33%, and the mass of the peeling material is 0.053-0.057kg / m 2 ; The relative dynamic modulus loss rate after 500 freeze-thaw cycles is 2.29-2.44%, and the mass of the peeling material is 0.071-0.075kg / m 2 In 5wt% sodium sulfate solution, the relative dynamic modulus loss rate after 300 freeze-thaw cycles was 0.96-1.24%, and the mass of the peeling material was 0.042-0.051kg / m 2 ; The relative dynamic modulus loss rate after 500 freeze-thaw cycles is 1.88-2.05%, and the mass of the peeling material is 0.059-0.067kg / m 2 In seawater, the relative dynamic modulus loss rate after 300 freeze-thaw cycles is 0.86-1.05%, and the mass of the peeling material is 0.055-0.071 kg / m 2 ; The relative dynamic modulus loss rate after 500 freeze-thaw cycles is 1.91-2.20%, and the mass of the peeling material is 0.074-0.081kg / m2 ;

[0027] The water reducer prepared by the present invention can enable concrete to obtain excellent resistance to chloride ion penetration. The water reducer of the present invention is added in an amount of 0.55wt% of the gel material, and the resistance to chloride ion penetration of the concrete is detected by the electric flux method according to the method in GB / T 50082-2009, and the electric flux is 87-92C;

[0028] The water reducer prepared by the present invention can effectively improve the strength of concrete. The water reducer of the present invention is added in an amount of 0.55wt% of the gel material, and the compressive strength and flexural strength of the concrete at 28d are tested according to the method in GB / T50081-2019. The compressive strength is 42.5-43.1MPa, and the flexural strength is 6.22-6.38MPa.

[0029] The water reducer prepared by the present invention can effectively improve the dispersibility of concrete. The water reducer of the present invention is added in an amount of 0.55wt% of the gel material, and the initial slump of the water reducer at this dosage and the change of the slump over time are tested according to the method in GB8076-2008. The initial slump is 217-224mm, and the change of the slump over time is 1.7-2.2mm. DETAILED DESCRIPTION

[0030] Example 1

[0031] (1) Preparation of amino acid grafted triterpenoid saponins

[0032] The triterpenoid saponin was mixed with a sodium hydroxide solution having a concentration of 0.5wt%, and stirred to completely dissolve it, to obtain a triterpenoid saponin solution for standby use; arginine was mixed with a sodium hydroxide solution having a concentration of 0.5wt%, and stirred to completely dissolve it; the obtained arginine solution was added to the triterpenoid saponin solution, and stirred to mix them evenly; the temperature was raised to 89°C, and the formaldehyde solution was added, and the addition time was controlled to be 15min; after the addition was completed, the temperature was maintained at 89°C, and the stirring was performed for 240min; after the stirring was completed, the water was evaporated using a rotary evaporator to obtain an amino acid-grafted triterpenoid saponin;

[0033] The mass ratio of the triterpenoid saponin to the sodium hydroxide solution is 1:12;

[0034] The mass ratio of arginine to sodium hydroxide solution is 1:7;

[0035] The mass ratio of the arginine solution, the triterpenoid saponin solution, and the formaldehyde solution is 3:1:1;

[0036] The concentration of the formaldehyde solution is 25wt%.

[0037] (2) Methylation treatment

[0038] The amino acid grafted triterpenoid saponin was mixed with deionized water, and trimethyl phosphate was added after stirring evenly, and the adding time was controlled to be 10 minutes. After the addition was completed, the pH was adjusted to 12.5, the temperature was controlled to be 135°C, and the stirring was performed for 80 minutes. After the stirring was completed, the amino acid grafted triterpenoid saponin was dialyzed and purified using a 500Da dialysis bag for 24 hours. After the dialysis was completed, the methylated amino acid grafted triterpenoid saponin was obtained;

[0039] The mass ratio of the amino acid grafted triterpenoid saponin, deionized water and trimethyl phosphate is 5:150:38.

[0040] (3) Mixing and preparation of air-entraining and water-reducing agent

[0041] The methylated amino acid-grafted triterpenoid saponin is mixed with an ethanol aqueous solution, stirred to completely dissolve, and then a polycarboxylic acid water-reducing agent powder and sodium carboxymethyl cellulose crushed to a fineness of 500 mesh are added, stirred to mix evenly, to obtain a mixed solution, and then the temperature is controlled to be 120° C., the mixed solution is dried for 12 hours, and after the drying is completed, the dried product is crushed to 500 mesh to obtain an antifreeze type highly dispersed water-reducing agent;

[0042] The model of the polycarboxylic acid water reducer is PC-1009, and the water reduction rate is 25%;

[0043] The mass ratio of the amino acid grafted triterpenoid saponin, ethanol aqueous solution, polycarboxylic acid water reducer powder, and sodium carboxymethyl cellulose is 5:60:37:7;

[0044] The concentration of the ethanol aqueous solution is 40wt%.

[0045] Example 2

[0046] (1) Preparation of amino acid grafted triterpenoid saponins

[0047] The triterpenoid saponin was mixed with a sodium hydroxide solution having a concentration of 0.45wt%, and stirred to completely dissolve it, to obtain a triterpenoid saponin solution for standby use; arginine was mixed with a sodium hydroxide solution having a concentration of 0.45wt%, and stirred to completely dissolve it; the obtained arginine solution was added to the triterpenoid saponin solution, and stirred to mix them evenly; the temperature was raised to 85°C, and the formaldehyde solution was added, and the addition time was controlled to be 17min; after the addition was completed, the temperature was maintained at 85°C, and the stirring was performed for 260min; after the stirring was completed, the water was evaporated using a rotary evaporator to obtain an amino acid-grafted triterpenoid saponin;

[0048] The mass ratio of the triterpenoid saponin to the sodium hydroxide solution is 1:13;

[0049] The mass ratio of arginine to sodium hydroxide solution is 1:7.5;

[0050] The mass ratio of the arginine solution, the triterpenoid saponin solution, and the formaldehyde solution is 2.5:0.9:0.9;

[0051] The concentration of the formaldehyde solution is 22 wt %.

[0052] (2) Methylation treatment

[0053] The amino acid grafted triterpenoid saponin was mixed with deionized water, and trimethyl phosphate was added after stirring evenly, and the adding time was controlled to be 8 minutes. After the addition was completed, the pH was adjusted to 12.2, and the temperature was controlled to be 130° C. and stirred for 90 minutes. After the stirring was completed, the amino acid grafted triterpenoid saponin was dialyzed and purified using a 500Da dialysis bag for 24 hours. After the dialysis was completed, the methylated amino acid grafted triterpenoid saponin was obtained;

[0054] The mass ratio of the amino acid grafted triterpenoid saponin, deionized water and trimethyl phosphate is 4.5:135:34.

[0055] (3) Mixing and preparation of air-entraining and water-reducing agent

[0056] The methylated amino acid-grafted triterpenoid saponin is mixed with an ethanol aqueous solution, stirred to completely dissolve, and then a polycarboxylic acid water-reducing agent powder and sodium carboxymethyl cellulose crushed to a fineness of 500 mesh are added, stirred to mix evenly, to obtain a mixed solution, and then the temperature is controlled to be 120° C., the mixed solution is dried for 12 hours, and after the drying is completed, the dried product is crushed to 500 mesh to obtain an antifreeze type highly dispersed water-reducing agent;

[0057] The model of the polycarboxylic acid water reducer is PC-1009, and the water reduction rate is 25%;

[0058] The mass ratio of the amino acid grafted triterpenoid saponin, ethanol aqueous solution, polycarboxylic acid water reducer powder, and sodium carboxymethyl cellulose is 4.5:50:32:6;

[0059] The concentration of the ethanol aqueous solution is 35wt%.

[0060] Example 3

[0061] (1) Preparation of amino acid grafted triterpenoid saponins

[0062] The triterpenoid saponin was mixed with a sodium hydroxide solution having a concentration of 0.55wt%, and stirred to completely dissolve it, to obtain a triterpenoid saponin solution for standby use; arginine was mixed with a sodium hydroxide solution having a concentration of 0.55wt%, and stirred to completely dissolve it; the obtained arginine solution was added to the triterpenoid saponin solution, and stirred to mix them evenly; the temperature was raised to 92°C, and the formaldehyde solution was added, and the addition time was controlled to be 12min; after the addition was completed, the temperature was maintained at 92°C, and the stirring was performed for 230min; after the stirring was completed, the water was evaporated using a rotary evaporator to obtain an amino acid-grafted triterpenoid saponin;

[0063] The mass ratio of the triterpenoid saponin to the sodium hydroxide solution is 1:11;

[0064] The mass ratio of arginine to sodium hydroxide solution is 1:6.5;

[0065] The mass ratio of the arginine solution, the triterpenoid saponin solution, and the formaldehyde solution is 3.5:1.1:1.1;

[0066] The concentration of the formaldehyde solution is 27 wt %.

[0067] (2) Methylation treatment

[0068] The amino acid grafted triterpenoid saponin was mixed with deionized water, and trimethyl phosphate was added after stirring evenly, and the adding time was controlled to be 12 minutes. After the addition was completed, the pH was adjusted to 12.7, the temperature was controlled to be 140°C, and the stirring was performed for 70 minutes. After the stirring was completed, the amino acid grafted triterpenoid saponin was dialyzed and purified using a 500Da dialysis bag for 24 hours. After the dialysis was completed, the methylated amino acid grafted triterpenoid saponin was obtained;

[0069] The mass ratio of the amino acid grafted triterpenoid saponin, deionized water and trimethyl phosphate is 5.5:160:42.

[0070] (3) Mixing and preparation of air-entraining and water-reducing agent

[0071] The methylated amino acid-grafted triterpenoid saponin is mixed with an ethanol aqueous solution, stirred to completely dissolve, and then a polycarboxylic acid water-reducing agent powder and sodium carboxymethyl cellulose crushed to a fineness of 500 mesh are added, stirred to mix evenly, to obtain a mixed solution, and then the temperature is controlled to be 120° C., the mixed solution is dried for 12 hours, and after the drying is completed, the dried product is crushed to 500 mesh to obtain an antifreeze type highly dispersed water-reducing agent;

[0072] The model of the polycarboxylic acid water reducer is PC-1009, and the water reduction rate is 25%;

[0073] The mass ratio of the amino acid grafted triterpenoid saponin, ethanol aqueous solution, polycarboxylic acid water reducer powder, and sodium carboxymethyl cellulose is 5.5:70:42:8;

[0074] The concentration of the ethanol aqueous solution is 45wt%.

[0075] Comparative Example 1

[0076] The difference from Example 1 is that the step of preparing amino acid-grafted triterpenoid saponin is omitted, and the untreated triterpenoid saponin is directly subjected to the methylation step. The remaining steps are the same to prepare the water reducing agent.

[0077] Comparative Example 2

[0078] Different from Example 1, the methylation treatment step is omitted, and after the step of preparing the amino acid grafted triterpenoid saponin, the amino acid grafted triterpenoid saponin is directly mixed to prepare the air-entraining water-reducing agent to prepare the water-reducing agent.

[0079] Example 4 Water reducing agent water reducing performance test

[0080] The water reducing agent of Example 1-3 and Comparative Example 1-2 was added in an amount of 0.55wt% of the gel material, and the water reduction rate of the water reducing agent at this dosage was tested according to the method in GB8076-2008. The results are shown in Table 1.

[0081] The test concrete mix is ​​as follows:

[0082] Cement 325kg / m 3 、Sand 655kg / m 3 、Crushed stone 1350kg / m 3 , water 130kg / m 3 ;

[0083] The cement is P·O42.5 silicate cement;

[0084] The sand is medium sand in zone II, with a fineness modulus of 2.5 and an apparent density of 2610 kg / m 3 ;

[0085] The crushed stone has a continuous gradation of particle size of 5-40 mm.

[0086] Table 1

[0087]

[0088] Example 5: Test on air entraining performance of water reducing agent

[0089] The water reducing agent of Example 1-3 and Comparative Example 1-2 was added in an amount of 0.55wt% of the gel material, and the air content of the water reducing agent at this dosage was tested according to the method in GB8076-2008. The results are shown in Table 2.

[0090] The test concrete mix is ​​as follows:

[0091] Cement 325kg / m 3 、Sand 655kg / m 3 、Crushed stone 1350kg / m 3 , water 130kg / m 3 ;

[0092] The cement is P·O42.5 silicate cement;

[0093] The sand is medium sand in zone II, with a fineness modulus of 2.5 and an apparent density of 2610 kg / m 3 ;

[0094] The crushed stone has a continuous gradation of particle size of 5-40 mm.

[0095] Table 2

[0096]

[0097] In Example 1-3, amino acid-grafted triterpenoid saponins were prepared, methylated, and finally mixed to prepare a composite water reducer. The obtained water reducer had stable air entraining performance and the air content of the concrete was high.

[0098] Comparative Example 1 omitted the step of preparing amino acid-grafted triterpenoid saponins, and directly subjected the untreated triterpenoid saponins to methylation treatment. The air entraining effect of the obtained water reducer decreased to a certain extent, and the air content of the concrete decreased to a certain extent.

[0099] In Comparative Example 2, the methylation treatment step is omitted. After the step of preparing the amino acid grafted triterpenoid saponin, the amino acid grafted triterpenoid saponin is directly mixed to prepare the air-entraining water-reducing agent. The air-entraining effect of the obtained water-reducing agent is greatly reduced, and the air content of the concrete is seriously reduced.

[0100] Example 6 Water reducing agent antifreeze performance test

[0101] The water reducing agent of Example 1-3 and Comparative Example 1-2 was added to the gel material in an amount of 0.55wt%, and the relative dynamic modulus loss rate and mass loss rate of the test pieces after 300, 400, and 500 freeze-thaw cycles were tested by the quick freezing method according to the method in GB / T 50082-2009. The results are shown in Table 3.

[0102] The test concrete mix is ​​as follows:

[0103] Cement 325kg / m 3 , sand 655kg / m 3 、Crushed stone 1350kg / m 3 , water 130kg / m 3 ;

[0104] The cement is P·O42.5 silicate cement;

[0105] The sand is medium sand in zone II, with a fineness modulus of 2.5 and an apparent density of 2610 kg / m 3 ;

[0106] The crushed stone has a continuous gradation of particle size of 5-40 mm.

[0107] Table 3

[0108]

[0109] In Example 1-3, amino acid-grafted triterpenoid saponins were prepared, methylated, and finally mixed to prepare a composite water reducer. It can be seen that special treatment of triterpenoid saponins can significantly improve the antifreeze performance of the water reducer on concrete. After multiple freeze-thaw cycles, the concrete can still maintain a low relative dynamic modulus loss rate and mass loss rate.

[0110] Comparative Example 1 omitted the step of preparing amino acid-grafted triterpenoid saponins, and directly subjected the untreated triterpenoid saponins to methylation treatment, resulting in poor improvement of the antifreeze performance of concrete by the water reducer. After multiple freeze-thaw cycles, the relative dynamic modulus loss rate and mass loss rate increased to a certain extent.

[0111] In Comparative Example 2, the methylation treatment step is omitted. After the step of preparing the amino acid grafted triterpenoid saponin, the amino acid grafted triterpenoid saponin is directly mixed to prepare the aerated water-reducing agent, resulting in poor improvement of the antifreeze performance of the concrete by the water-reducing agent. After multiple freeze-thaw cycles, the relative dynamic modulus loss rate and the mass loss rate increase to a large extent, especially after 500 freeze-thaw cycles, the increase in the relative dynamic modulus loss rate and the mass loss rate is more serious.

[0112] The water reducing agent of Example 1-3 and Comparative Example 1-2 was added in an amount of 0.55wt% of the gel material, and the quick freezing method was adopted according to the method in GB / T 50082-2009. The erosion medium was 3.5wt% sodium chloride solution, 5wt% sodium sulfate solution, and seawater. The relative dynamic modulus loss rate and the mass of the peeling material of the specimens after 300 and 500 freeze-thaw cycles in different media were tested respectively. The results are shown in Table 4.

[0113] The test concrete mix is ​​as follows:

[0114] Cement 325kg / m 3 、Sand 655kg / m 3 、Crushed stone 1350kg / m 3 , water 130kg / m 3 ;

[0115] The cement is P·O42.5 silicate cement;

[0116] The sand is medium sand in zone II, with a fineness modulus of 2.5 and an apparent density of 2610 kg / m 3 ;

[0117] The crushed stone has a continuous gradation of particle size of 5-40 mm.

[0118] Table 4

[0119]

[0120] In Example 1-3, amino acid-grafted triterpenoid saponins were prepared, methylated, and finally mixed to prepare a composite water reducer. It can be seen that the special treatment of triterpenoid saponins can significantly improve the antifreeze performance of concrete in different types of high-salt media. After multiple freeze-thaw cycles, the concrete can still maintain a low relative dynamic modulus loss rate. In the high-salt medium, the anti-stripping performance is also good, and the quality of the spalling of the concrete sample is low.

[0121] Comparative Example 1 omitted the step of preparing amino acid-grafted triterpenoid saponins, and directly subjected the untreated triterpenoid saponins to methylation treatment, resulting in poor frost resistance of concrete in high-salt media, large loss rate of relative dynamic modulus after multiple freeze-thaw cycles, poor anti-stripping performance, and high quality of spalling of concrete samples;

[0122] Comparative Example 2 omits the methylation treatment step. After the step of preparing the amino acid grafted triterpenoid saponin, the amino acid grafted triterpenoid saponin is directly mixed to prepare the air-entraining and water-reducing agent, resulting in poor frost resistance of the concrete in a high-salt medium, especially after 500 freeze-thaw cycles, the relative dynamic modulus loss rate increases seriously, the anti-stripping performance is also poor, and the spalling of the concrete sample increases seriously.

[0123] Example 7 Test on the anti-chloride ion penetration performance of water reducing agent

[0124] The water reducing agent of Example 1-3 and Comparative Example 1-2 was added in an amount of 0.55wt% of the gel material. According to the method in GB / T 50082-2009, the anti-chloride ion penetration performance of the concrete was tested by the electric flux method. The results are shown in Table 5.

[0125] The test concrete mix is ​​as follows:

[0126] Cement 325kg / m 3 、Sand 655kg / m 3 、Crushed stone 1350kg / m 3 , water 130kg / m 3 ;

[0127] The cement is P·O42.5 silicate cement;

[0128] The sand is medium sand in zone II, with a fineness modulus of 2.5 and an apparent density of 2610 kg / m 3 ;

[0129] The crushed stone has a continuous gradation of particle size of 5-40 mm.

[0130] Table 5

[0131]

[0132] In Example 1-3, amino acid-grafted triterpenoid saponins were prepared, methylated, and finally mixed to prepare a composite water reducer. It can be seen that special treatment of triterpenoid saponins can significantly improve the anti-chloride ion penetration performance of the water reducer on concrete, and the concrete can maintain a low electrical flux.

[0133] Comparative Example 1 omitted the step of preparing amino acid grafted triterpenoid saponins, and directly subjected the untreated triterpenoid saponins to methylation treatment. The chloride ion penetration resistance of the concrete was seriously reduced, and the electrical flux of the concrete was relatively high.

[0134] In Comparative Example 2, the methylation treatment step is omitted. After the step of preparing the amino acid grafted triterpenoid saponin, the amino acid grafted triterpenoid saponin is directly mixed to prepare the air-entraining and water-reducing agent. The chloride ion penetration resistance of the concrete is seriously reduced, and the electrical flux of the concrete is relatively high.

[0135] Example 8 Water reducing agent enhancement effect test

[0136] The water reducers of Examples 1-3 and Comparative Examples 1-2 were added in an amount of 0.55 wt% of the gel material, and the compressive strength and flexural strength of the concrete at 28 days were tested at this dosage of the water reducer according to the method in GB / T50081-2019. The results are shown in Table 6.

[0137] The test concrete mix is ​​as follows:

[0138] Cement 325kg / m 3 、Sand 655kg / m 3 、Crushed stone 1350kg / m 3 , water 130kg / m 3 ;

[0139] The cement is P·O42.5 silicate cement;

[0140] The sand is medium sand in zone II, with a fineness modulus of 2.5 and an apparent density of 2610 kg / m 3 ;

[0141] The crushed stone has a continuous gradation of particle size of 5-40 mm.

[0142] Table 6

[0143]

[0144] In Example 1-3, amino acid-grafted triterpenoid saponins were prepared, methylated, and finally mixed to prepare a composite water reducer. It can be seen that special treatment of triterpenoid saponins can significantly improve the anti-chloride ion penetration performance of the water reducer on concrete, and the concrete can maintain a low electrical flux.

[0145] Comparative Example 1 omitted the step of preparing amino acid grafted triterpenoid saponins, and directly subjected the untreated triterpenoid saponins to methylation treatment. The chloride ion penetration resistance of the concrete was seriously reduced, and the electrical flux of the concrete was relatively high.

[0146] In Comparative Example 2, the methylation treatment step is omitted. After the step of preparing the amino acid grafted triterpenoid saponin, the amino acid grafted triterpenoid saponin is directly mixed to prepare the air-entraining and water-reducing agent. The chloride ion penetration resistance of the concrete is seriously reduced, and the electrical flux of the concrete is relatively high.

[0147] Example 9 Water reducing agent dispersion performance test

[0148] The water reducing agent of Example 1-3 and Comparative Example 1-2 was added in an amount of 0.55wt% of the gel material, and the initial slump of the water reducing agent at this dosage and the change of slump over time were tested according to the method in GB8076-2008. The results are shown in Table 7.

[0149] The test concrete mix is ​​as follows:

[0150] Cement 325kg / m 3 、Sand 655kg / m 3 、Crushed stone 1350kg / m 3 , water 130kg / m 3 ;

[0151] The cement is P·O42.5 silicate cement;

[0152] The sand is medium sand in zone II, with a fineness modulus of 2.5 and an apparent density of 2610 kg / m 3 ;

[0153] The crushed stone has a continuous gradation of particle size of 5-40 mm.

[0154] Table 7

[0155]

[0156] In Example 1-3, amino acid-grafted triterpenoid saponins are prepared, methylated, and finally mixed to prepare a composite water reducer. The water reducer can make concrete have better dispersibility, higher initial slump, and less change in slump over time;

[0157] Comparative Example 1 omitted the step of preparing amino acid-grafted triterpenoid saponins, and directly subjected the untreated triterpenoid saponins to methylation treatment. The dispersibility of the concrete deteriorated, the initial slump decreased to a certain extent, and the slump changed greatly over time.

[0158] In Comparative Example 2, the methylation treatment step is omitted. After the step of preparing the amino acid grafted triterpenoid saponin, the amino acid grafted triterpenoid saponin is directly mixed to prepare the air-entraining and water-reducing agent. The dispersibility of the concrete becomes worse, the initial slump decreases to a large extent, and the slump changes greatly over time.

Claims

1. A method for preparing an antifreeze type highly dispersible water reducing agent, characterized in that: The preparation method comprises preparing amino acid grafted triterpenoid saponin, methylation treatment, and mixing to prepare an air-entraining and water-reducing agent; The method for preparing amino acid grafted triterpenoid saponin comprises: mixing triterpenoid saponin with a sodium hydroxide solution having a concentration of 0.45-0.55wt%, stirring to completely dissolve the triterpenoid saponin solution for standby use; mixing arginine with a sodium hydroxide solution having a concentration of 0.45-0.55wt%, stirring to completely dissolve the triterpenoid saponin solution; adding the obtained arginine solution to the triterpenoid saponin solution, stirring to uniformly mix the solution; heating the solution to 85-92°C; adding formaldehyde solution; controlling the adding time to be 12-17min; maintaining the temperature at 85-92°C after the adding is completed; stirring the solution for 230-260min; and, after the stirring is completed, using a rotary evaporation method to evaporate water to obtain amino acid grafted triterpenoid saponin; The mass ratio of the triterpenoid saponin to the sodium hydroxide solution is 1:(11-13); The mass ratio of arginine to sodium hydroxide solution is 1:(6.5-7.5); The mass ratio of the arginine solution, the triterpenoid saponin solution and the formaldehyde solution is (2.5-3.5): (0.9-1.1): (0.9-1.1); The methylation treatment method comprises mixing the amino acid grafted triterpenoid saponin with deionized water, stirring evenly, adding trimethyl phosphate, controlling the adding time to be 8-12 minutes, adjusting the pH to be 12.2-12.7, controlling the temperature to be 130-140° C., stirring, and stirring for 70-90 minutes, and performing dialysis purification after stirring, and obtaining the amino acid grafted triterpenoid saponin treated with methylation; The mass ratio of the amino acid grafted triterpenoid saponin, deionized water, and trimethyl phosphate is (4.5-5.5): (135-165): (34-42); The method for preparing the air-entraining water-reducing agent by mixing is as follows: mixing the methylated amino acid-grafted triterpenoid saponin with an ethanol aqueous solution, stirring to completely dissolve it, then adding a polycarboxylic acid water-reducing agent powder crushed to a fineness of 500 mesh and sodium carboxymethyl cellulose, stirring to mix them evenly, obtaining a mixed solution, then drying the mixed solution, and after drying, crushing the dried product to 500 mesh to obtain an antifreeze type highly dispersed water-reducing agent; The mass ratio of the amino acid grafted triterpenoid saponin, ethanol aqueous solution, polycarboxylic acid water reducer powder and sodium carboxymethyl cellulose is (4.5-5.5): (50-70): (32-42): (6-8).

2. The method for preparing an antifreeze type highly dispersible water reducing agent according to claim 1, characterized in that: In the step of preparing amino acid-grafted triterpenoid saponins, the concentration of the formaldehyde solution is 22-27 wt %.

3. The method for preparing an antifreeze type highly dispersible water reducing agent according to claim 1, characterized in that: In the methylation treatment step, the dialysis purification method is to use a 500Da dialysis bag for dialysis purification, and the purification time is 24 hours.

4. The method for preparing an antifreeze type highly dispersible water reducing agent according to claim 1, characterized in that: In the step of mixing and preparing the air-entraining and water-reducing agent, the drying method is to control the temperature to 120° C. and dry the mixed liquid for 12 hours.

5. The method for preparing an antifreeze type highly dispersible water reducing agent according to claim 1, characterized in that: In the step of mixing and preparing the aerated water-reducing agent, the model of the polycarboxylic acid water-reducing agent is PC-1009, and the water reduction rate is 25%.

6. The method for preparing an antifreeze type highly dispersible water reducing agent according to claim 1, characterized in that: In the step of mixing and preparing the air-entraining and water-reducing agent, the concentration of the ethanol aqueous solution is 35-45wt%.

Images