CN107840592B - Concrete self-repairing functional additive and preparation method thereof - Google Patents

Abstract

The invention belongs to the field of building materials, and particularly relates to a concrete self-repairing functional additive and a preparation method thereof. The functional additive is prepared by mixing a multi-element ion complexing agent, calcium bicarbonate and water-absorbent resin, and the functional additive comprises the following raw materials in parts by weight: 40-60 parts of a multi-ion complexing agent, 40-50 parts of calcium bicarbonate and 1-5 parts of a water-absorbent resin. The functional admixture has the advantages of strong self-repairing capability, good wide crack self-repairing effect, high repairing speed and the like, has no delayed coagulation effect, has stronger practicability, and has stronger application and popularization values in the field of concrete self-repairing.

Description

A kind of concrete self-healing function admixture and preparation method thereof

technical field

The invention belongs to the field of building materials, in particular to a concrete self-repairing function admixture and a preparation method thereof.

Background technique

As an important basic building material, cement concrete has been widely used in housing construction, road construction, subway tunnels, bridges, reservoir dams, hydropower stations, docks and other fields. However, concrete is a porous and brittle material, which is prone to internal damage and cracks due to external environmental factors. Damage and cracks will reduce the strength of concrete, aggravate the chemical erosion of concrete, freeze-thaw damage, steel corrosion and alkali-aggregate reaction, and seriously reduce the durability of concrete structures.

In order to improve the durability of concrete structures, more and more attention has been paid to the self-healing technology of concrete damage and cracks. The existing concrete self-healing technologies mainly include: adding functional admixtures to stimulate the self-repair of concrete components at internal damage and cracks; adding microcapsules containing binders, and the binders self-repair the cracks after the microcapsules are ruptured; Microorganisms and nutrient solution are added to concrete, and calcite is produced by the reaction of microorganisms and nutrient solution to self-repair damage and cracks. Among these self-healing technologies, the microcapsule method has the problems that the capsule is difficult to break when damage and cracks are formed, and the binder cannot flow out.

Compared with the microencapsulation method and the microbial method, the self-healing technology of the functional admixture method has certain practicability. Patent CN 101386508 A discloses the formula and preparation process of a crack self-healing material. The formula of the crack self-healing material disclosed by the invention is: 62-77% Portland cement, 0.2-1% sodium citrate, 3% -8% choline, 1-3% calcium oxide, 22-35% 80-120 mesh. When cracks appear in concrete, under the condition of moisture or dampness, the invention utilizes sodium citrate and choline to form water-soluble unstable complexes with calcium ions and silicate ions in concrete respectively, which can form water-soluble unstable complexes at the pores and cracks of concrete. The crystallization forms a precipitate and realizes self-healing. Patent CN 105884299A discloses a super self-healing scale cracked concrete high-permeability crystalline repair material. The composition of the material is: ordinary Portland cement 30-45%, quartz sand 40-60%, fly ash 3-15% , silica fume 1-8%, aluminate cement 1-10%, gypsum 1-10%, sodium hydroxide 0.1-4%, water glass 0.1-4%, redispersible powder 0.1-2%, polycarboxylate Acid-based water reducing agent 0.05-1.5%, sodium gluconate 0.01-1% and polypropylene fiber 0.1-2.5%. But the existing concrete self-healing function admixtures all exist: (1) The used sodium citrate and sodium gluconate have a strong inhibitory effect on the hydration of cement, which are typical cement concrete retarders. Extend the setting time of concrete; (2) The chelated products formed by the reaction of sodium citrate, sodium gluconate, etc. with calcium ions are annular structures with large molecular size, and the migration speed to the cracks of concrete is slow, even in some tiny pores (3) There are few free calcium ions and silicate ions in concrete, and the number of chelated calcium ions such as sodium citrate and sodium gluconate is small, and the ability to carry calcium ions to cracks is weak, which is relatively Wide cracks cannot self-repair; (4) The chelation reaction of sodium citrate, sodium gluconate, etc. with calcium ions and migration into the cracks, and the reaction of functional additives with silicate ions, all need to be in the presence of moisture or humidity. It takes a long time for the self-healing of cracks to occur, and the moisturizing ability of concrete is very weak, and the internal water volatilizes quickly. Once there is no water or moisture in the concrete, the self-healing reaction will stop, and it is difficult to achieve a good repair. The existence of these problems severely limits the application of functional admixtures in concrete self-healing.

SUMMARY OF THE INVENTION

Aiming at the deficiencies of the prior art, the present invention aims to provide a concrete self-repairing function admixture and a preparation method thereof.

In order to realize the above-mentioned purpose of the invention, the technical scheme adopted in the present invention is:

A concrete self-repairing function admixture is prepared by mixing a multi-component ion complexing agent, calcium bicarbonate and a water-absorbent resin. 40 to 50 parts, and 1 to 5 parts of water-absorbent resin.

其中n为2或3，分子量介于280～430Da。In the above scheme, the molecular structural formula of the multi-component ion complexing agent is:

Wherein n is 2 or 3, and the molecular weight ranges from 280 to 430 Da.

In the above scheme, the multi-component ion complexing agent is prepared by the following method: maleic anhydride and deionized water are added to the reactor with a condensing reflux device, and the temperature is raised while stirring, and the maleic anhydride is completely dissolved. Then, the temperature is raised to 90-95° C., an aqueous hydrogen peroxide solution is added, and after a constant temperature reaction for a period of time, a sodium hydroxide solution is added to continue the reaction. After the reaction, the product is spray-dried to obtain a multi-ion complexing agent.

In the above scheme, the raw materials in the preparation method are calculated in parts by weight: 100 parts of maleic anhydride, 100 parts of deionized water, 30 parts of hydrogen peroxide solution, and 100 parts of sodium hydroxide solution; The volume concentration of the hydrogen aqueous solution is 25% to 35%, and the molar concentration of the sodium hydroxide solution is 0.1 mol/L to 0.15 mol/L.

In the above scheme, the time of constant temperature reaction in the preparation method is 3h-5h, and sodium hydroxide solution is added to continue the reaction for 1h-2h.

In the above solution, the water absorbent resin is an acrylic acid-acrylamide copolymerized water absorbent resin, and the water absorption ratio is 100-300.

The preparation method of the above-mentioned concrete self-repairing function admixture comprises the following steps: 1) weighing 40-60 parts of multi-component ion complexing agent, 30-50 parts of calcium bicarbonate, 1- 5 parts; 2) Add 40-60 parts of multi-component ion complexing agent, 30-50 parts of calcium bicarbonate, and 1-5 parts of water-absorbent resin into the mixer for mechanical mixing for 5 minutes to obtain concrete self-healing function admixture .

The multi-component ion complexing agent synthesized by the present invention is formed by the reaction of 2 or 3 maleic anhydrides, and the molecular structure formula is:

(n＝2或3)，分子量介于280～430，所述多元离子络合剂具有如下优点：①为线型分子结构，其与钙离子形成的络合物在混凝土的孔隙或裂缝中迁移速度快，微小孔隙中也容易通过；②含有多个络合单元，可同时络合4～6个钙离子，络合离子数量多，对裂缝修复能力强；③不含有羟基，对水泥的水化进程无抑制作用，不影响混凝土的凝结时间。

(n=2 or 3), the molecular weight is between 280 and 430, and the multi-ion complexing agent has the following advantages: ① It is a linear molecular structure, and the complex formed with calcium ions migrates in the pores or cracks of concrete The speed is fast, and it is easy to pass through the tiny pores; ②It contains multiple complex units, which can complex 4 to 6 calcium ions at the same time. The number of complex ions is large, and the crack repair ability is strong; The chemical process has no inhibitory effect and does not affect the setting time of concrete.

The beneficial effects of the present invention are as follows:

(1) The concrete self-healing function admixture of the present invention is prepared from a multi-component ion complexing agent, calcium bicarbonate, and a water-absorbent resin, wherein the multi-component ion complexing agent contains a plurality of complexing units, which can complex more A large amount of calcium ions; the calcium bicarbonate can provide calcium ions and carbonate ions through hydrolysis; the multi-ion complexing agent forms soluble complexes with free calcium ions in concrete and calcium ions generated by the hydrolysis of calcium bicarbonate. Water migrates to pores, microcracks and cracks, and the soluble complexes containing calcium ions are hydrolyzed with silicate ions and carbonate ions in concrete (carbonate ions produced by the hydrolysis of calcium bicarbonate and carbon dioxide in the air that penetrates into the concrete. The resulting carbonate ions) react to form calcium silicate and calcium carbonate precipitation to repair damage and cracks; the number of ions that can be complexed by the multi-ion complexing agent is large, and the source of calcium ions in the functional admixture is sufficient, and the water-absorbent resin is used. The super water absorption capacity enables the concrete to be in a wet state for a long time, ensuring the continuous progress of the self-healing process, and greatly improving the self-healing ability of the functional admixture to the internal damage of the concrete and the wide cracks. It has the advantages of strong self-healing ability and good self-repairing effect of wide cracks;

(2) The multi-ion complexing agent described in the present invention has a linear molecular structure, and the complex formed with calcium ions has a fast migration speed in the pores or cracks of the concrete, and is also easy to pass through the tiny pores, which is conducive to complexation. The speed of material migration to concrete micro-cracks and cracks has the advantage of fast repair speed;

(3) The multi-ion complexing agent described in the present invention does not contain hydroxyl groups, has no inhibitory effect on the hydration process of cement, does not affect the setting time of concrete, has no retarding effect, and is more practical, and is used in the field of concrete self-healing. It has strong application promotion value.

Description of drawings

Figure 1 is a photo of self-healing cracks of ordinary concrete (control group) without adding the self-healing function admixture of the present invention, wherein the left picture is the initial crack; the right picture is the crack after standard curing for 28d.

Figure 2 is a photo of the self-healing of concrete cracks added with the self-healing functional admixture of the present invention, wherein the left picture is the initial crack; the right picture is the crack after standard curing for 28d.

Detailed ways

In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

In the following examples, the multi-component ion complexing agent was prepared by the following method: adding 200 parts of deionized water and 200 parts of maleic anhydride into a 1000ml three-necked flask equipped with condensation reflux, and stirring the maleic anhydride All dissolved, heated to 90 ~ 95 ℃, added 30 parts of hydrogen peroxide aqueous solution with a concentration of 30vt%, constant temperature reaction for 4h, then added 100 parts of 0.12mol/L sodium hydroxide solution, reacted for 1.5h, and then prepared by spray drying. A multi-ionic complexing agent was obtained.

Example 1

A concrete self-healing function admixture, prepared by the following method: weighing 53 parts of multi-component ion complexing agent, 45 parts of calcium bicarbonate, and 2 parts of acrylic acid-acrylamide copolymerized water-absorbent resin, adding it into a mixer for mechanical stirring for 5 minutes, to obtain Self-healing admixture for concrete.

Example 2

A concrete self-healing function admixture, prepared by the following method: weighing 53 parts of multi-component ion complexing agent, 43 parts of calcium bicarbonate, and 4 parts of acrylic acid-acrylamide copolymerized water-absorbent resin, adding it into a mixer for mechanical stirring for 5 minutes, to obtain Self-healing admixture for concrete.

Weigh cement, crushed stone, mineral powder, sand, water, water reducing agent and concrete self-healing function admixture prepared in Example 1 or Example 2 according to the mass ratio in Table 1. First add crushed stone, sand, mineral powder, cement and self-healing admixture into the concrete mixer and mix for 30s, then add the water reducer and water into the mixer and mix for 120s, that is, concrete with self-healing function of cracks is obtained; the control group The concrete self-healing function admixture is not added, and other conditions are the same.

Freeze-thaw damage self-healing and crack self-healing tests were performed on the self-healing concrete prepared above and the control group concrete respectively. The specific operations are as follows:

(1) Take parts from the repaired concrete and the control group concrete, put them into 100mm×100mm×100mm molds, demould after 1 day, put them in the curing room for 28 days, and take out the test pieces according to the national standard GB/T50082-2009. After 200 slow freeze-thaw cycles, the specimens were taken out after the freeze-thaw cycles, and watered for 28 days (watering once every 4 days) to test the compressive strength of the specimens before and after the freeze-thaw cycles and after watering and curing. Example 1 The compressive strength of the self-healing concrete before the freeze-thaw cycle was 43.2 MPa, the compressive strength after the freeze-thaw cycle was 35.8 MPa, and the compressive strength after watering and curing was 39.8 MPa; The compressive strength is 42.5MPa, the compressive strength after the freeze-thaw cycle is 35.2MPa, and the compressive strength after watering and curing is 40.6MPa; the compressive strength of the control group concrete before the freeze-thaw cycle is 41.8MPa, and the compressive strength after the freeze-thaw cycle is 31.7MPa, the compressive strength after watering and curing is 32.6MPa. The test results show that the internal damage of ordinary concrete (control group) caused by freeze-thaw cycles cannot be healed after 28 days of curing, while the internal damage of concrete mixed with self-healing admixtures caused by freeze-thaw cycles has been cured well after curing. Repair (the compressive strength recovery rate of Example 1 is 92.1%, and the recovery rate of compressive strength of Example 2 is 95.5%); The damage self-healing ability was further improved.

(2) Take parts from the repaired concrete and the control group concrete, pour them into the anti-cracking mold of the concrete slab respectively, blow it with a fan for 4 hours immediately after vibrating and leveling, and keep the wind speed at the center of the concrete specimen not less than 5m/s, so that the concrete produces Cracks, the initial cracks were measured, followed by watering and curing (watering every 4 days), and the crack widths were measured at 7 days, 14 days, 21 days and 28 days, respectively. The results of the crack width measurements are listed in Table 2. It can be seen from Table 2 that the self-healing ability of ordinary concrete in the control group is very weak, and the crack width basically does not change with the extension of curing time, while the concrete with self-healing admixture is not only self-healing for small cracks (less than 0.2mm) The effect is very good, and it also shows a strong self-healing ability for wider cracks (greater than 0.3mm); Self-healing ability is further enhanced.

Table 1 Proportion of concrete

Table 2 Variation of crack width in the curing process of concrete prepared in Examples 1, 2 and the control group

Example 3

A concrete self-healing function admixture, prepared by the following method: weighing 53 parts of multi-component ion complexing agent, 45 parts of calcium bicarbonate, and 3 parts of acrylic acid-acrylamide copolymerized water-absorbent resin, adding it into a mixer for mechanical stirring for 5 minutes, to obtain Concrete self-healing function admixture.

Example 4

A concrete self-healing function admixture, prepared by the following method: weighing 57 parts of multi-component ion complexing agent, 40 parts of calcium bicarbonate, and 3 parts of acrylic acid-acrylamide copolymerized water-absorbent resin, adding it into a mixer for mechanical stirring for 5 minutes, to obtain Self-healing admixture for concrete.

Weigh cement, crushed stone, mineral powder, sand, water, water reducing agent and concrete self-healing function admixture prepared in Example 3 or Example 4 according to the mass ratio in Table 3. First add crushed stone, sand, mineral powder, cement and self-healing admixture into the concrete mixer and mix for 30s, then add the water reducer and water into the mixer and mix for 120s, that is, concrete with self-healing function of cracks is obtained; the control group The concrete self-healing function admixture is not added, and other conditions are the same.

Freeze-thaw damage self-healing and crack self-healing tests were performed on the self-healing concrete prepared above and the control group concrete respectively:

(1) Take parts from the repaired concrete and the control group concrete, put them into 100mm×100mm×100mm molds, demould after 1 day, put them in the curing room for 28 days, and take out the test pieces according to the national standard GB/T50082-2009. After 300 slow freeze-thaw cycles, the specimens were taken out after the freeze-thaw cycles, watered for 28 days (watering once every 4 days), and the compressive strength of the specimens before and after the freeze-thaw cycles and after watering and curing was tested. Example 3 The compressive strength of the self-healing concrete before the freeze-thaw cycle was 59.3 MPa, the compressive strength after the freeze-thaw cycle was 50.4 MPa, and the compressive strength after watering and curing was 55.0 MPa; the compressive strength of the self-healing concrete before the freeze-thaw cycle in Example 4 The strength is 61.1MPa, the compressive strength after the freeze-thaw cycle is 51.2MPa, and the compressive strength after watering and curing is 57.6MPa; the compressive strength of the contrast group concrete before the freeze-thaw cycle is 57.5MPa, and the compressive strength after the freeze-thaw cycle is 42.7 MPa, the compressive strength after watering and curing is 44.2MPa. The test results also show that the internal damage of ordinary concrete (control group) caused by freeze-thaw cycles is basically not healed after 28 days of curing, while the internal damage of concrete mixed with self-healing admixtures caused by freeze-thaw cycles has been cured after curing. It is well repaired; compared with Example 3, the content of multi-component ion complexing agent in the self-repairing function admixture used in Example 4 is increased, and the self-repairing ability of the internal damage of concrete is further improved.

(2) Take parts from the repaired concrete and the control group concrete, pour them into the anti-cracking mold of the concrete slab respectively, blow it with a fan for 4 hours immediately after vibrating and leveling, and keep the wind speed at the center of the concrete specimen not less than 5m/s, so that the concrete produces Cracks, the initial cracks were measured, followed by watering and curing (watering every 4 days), and the crack widths were measured at 7 days, 14 days, 21 days and 28 days, respectively. The results of the crack width measurements are listed in Table 4. It can be seen from Table 4 that the crack width of ordinary concrete in the control group is basically unchanged, while the repair ability of concrete cracks mixed with functional admixtures prepared in Examples 3 and 4 is significantly improved. Compared with Example 3, the content of multi-component ion complexing agent in the self-healing function admixture used in Example 4 is increased, the self-healing ability of concrete cracks is further improved, and it also has self-healing ability for cracks larger than 0.7mm.

Table 3 Proportion of concrete

Variation of crack width in the curing process of concrete prepared by Examples 3 and 4 of Table 4 and the control group

Example 5

A concrete self-healing function admixture, prepared by the following method: weighing 40 parts of multi-component ion complexing agent, 50 parts of calcium bicarbonate, and 5 parts of acrylic acid-acrylamide copolymer water-absorbent resin; , calcium bicarbonate and water-absorbent resin are added into the mixer for mechanical mixing for 5 minutes, and the concrete self-healing function admixture is obtained.

Example 6

A concrete self-healing function admixture, prepared by the following method: weighing 60 parts of multi-component ion complexing agent, 30 parts of calcium bicarbonate, and 1 part of acrylic acid-acrylamide copolymer water-absorbent resin; , calcium bicarbonate and water-absorbent resin are added into the mixer for mechanical mixing for 5 minutes, and the concrete self-healing function admixture is obtained.

Obviously, the above-mentioned embodiments are only examples for clear illustration, and are not intended to limit the implementation manner. For those of ordinary skill in the art, changes or modifications in other different forms can also be made on the basis of the above description. There is no need and cannot be exhaustive of all implementations here. However, the obvious changes or changes derived therefrom still fall within the protection scope of the present invention.

Claims (6)

1. a concrete self-repairing function admixture, is characterized in that, is mixed and prepared by multi-component ion complexing agent, calcium bicarbonate, water-absorbing resin, and each raw material is counted in parts by weight: multi-component ion complexing agent 40 ~ 60 parts, 40-50 parts of calcium bicarbonate, 1-5 parts of water-absorbent resin; the molecular structure formula of the multi-component ion complexing agent is: wherein n is 2, and the molecular weight is between 280 and 430; the water-absorbent resin is an acrylic acid-acrylamide copolymerized water-absorbent resin. 2. concrete self-healing function admixture according to claim 1, is characterized in that, described multi-component ion complexing agent is prepared by the following method: maleic anhydride and deionized water are added to belt condensation reflux device reaction In the vessel, the temperature is raised while stirring. After the maleic anhydride is completely dissolved, the temperature is raised to 90~95°C, and the aqueous hydrogen peroxide solution is added. After a period of constant temperature reaction, the sodium hydroxide solution is added to continue the reaction. The product is spray-dried to obtain a multi-ion complexing agent. 3. concrete self-healing function admixture according to claim 2, is characterized in that, in described preparation method, each raw material is counted by weight: 100 parts of maleic anhydride, 100 parts of deionized water, peroxide 30 parts of an aqueous hydrogen solution and 100 parts of a sodium hydroxide solution; the volume concentration of the aqueous hydrogen peroxide solution is 25% to 35%, and the molar concentration of the sodium hydroxide solution is 0.1 mol/L to 0.15 mol/L. 4. The concrete self-healing function admixture according to claim 2, characterized in that, in the preparation method, the time for constant temperature reaction is 3h～5h, and sodium hydroxide solution is added to continue the reaction for 1h～2h. 5 . The self-healing function admixture for concrete according to claim 1 , wherein the water absorption ratio of the acrylic-acrylamide copolymer water-absorbent resin is 100-300. 6 . 6. the preparation method of the concrete self-repairing function admixture described in any one of claim 1～5, it is characterized in that, comprises the following steps: 1) according to the weight ratio of each raw material, take by weighing 40～60 parts of multi-component ion complexing agent , 40~50 parts of calcium bicarbonate, 1~5 parts of water absorbent resin; 2) 40~60 parts of multi-component ion complexing agent, 40~50 parts of calcium bicarbonate, 1~5 parts of water absorbent resin are added and mixed Mechanical mixing in the machine for 5 minutes, the concrete self-healing function admixture is obtained.