CN107840592A - A kind of concrete self-repair function additive and preparation method thereof - Google Patents

Abstract

The invention belongs to the field of building materials, and in particular relates to a concrete self-repairing functional admixture and a preparation method thereof. The functional admixture is prepared by mixing multiple ion complexing agent, calcium bicarbonate, and water-absorbent resin. The raw materials are calculated in parts by weight: 40-60 parts of multiple ion complexing agent, 40-50 parts of calcium bicarbonate , 1 to 5 parts of water-absorbent resin. The functional admixture has the advantages of strong self-repair ability, good self-repair effect for wide cracks, fast repair speed, etc., has no retarding effect, has stronger practicability, and has strong application and promotion value in the field of concrete self-repair.

Description

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

technical field

The invention belongs to the field of building materials, and in particular relates to a concrete self-repairing functional 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, corrosion of steel bars 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. Existing concrete self-repairing technologies mainly include: adding functional admixtures to stimulate the concrete’s own components to react and self-repair at internal damage and cracks; adding microcapsules containing a binder, and the binder will self-repair the cracks after the microcapsules are broken; Add microorganisms and nutrient solution to concrete, and produce calcite through the reaction of microorganisms and nutrient solution to self-repair damage and cracks. Among these self-repairing technologies, the microcapsule method has the problem that the capsule is difficult to break when damage and cracks are formed, and the binder cannot flow out. The microbial method has the problem of short microbial survival and will reduce the strength of concrete, and none of them are practical.

Compared with microcapsule method and microbial method, functional admixture method self-repair technology has certain practicability. Patent CN 101386508 A discloses a formula and preparation process of a crack self-healing material. The formula of the crack self-healing material disclosed in 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 there are cracks in the concrete, under the condition of moisture or humidity, the invention uses sodium citrate and choline to form water-soluble unstable complexes with calcium ions and silicate ions in the concrete respectively, and the complexes are formed in the pores and cracks of the concrete. Crystallization forms precipitates to achieve 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 rubber powder 0.1-2%, polycarboxylate 0.05-1.5% acid-based water reducer, 0.01-1% sodium gluconate and 0.1-2.5% polypropylene fiber. But existing concrete self-repairing function admixture all exists: (1) the sodium citrate that uses, sodium gluconate have very strong inhibitory action to the hydration of cement, belong to typical cement concrete retarder, a small amount of adding will greatly Prolong the setting time of concrete; (2) The chelated products formed by the reaction of sodium citrate, sodium gluconate, etc. (3) There are less free calcium ions and silicate ions in concrete, and the amount of chelated calcium ions such as sodium citrate and sodium gluconate is small, and the ability to carry calcium ions to cracks is weak. Wide cracks cannot be self-repaired; (4) Sodium citrate, sodium gluconate, etc. have a chelation reaction with calcium ions and migrate into the cracks, and the reaction between functional admixtures and silicate ions requires moisture or moisture. However, the self-healing of cracks takes a long time, and the moisture retention capacity of concrete is very weak, and the internal moisture evaporates quickly. Once there is no moisture 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-repair.

Contents of the invention

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

For realizing above-mentioned purpose of the invention, the technical scheme that the present invention adopts is:

A concrete self-repairing functional admixture is prepared by mixing multiple ion complexing agents, calcium bicarbonate, and water-absorbent resins. The raw materials are calculated in parts by weight: 40-60 parts of multiple ion complexing agents, calcium bicarbonate 40-50 parts, 1-5 parts of water-absorbent resin.

In the above-mentioned scheme, the molecular structural formula of described multiple ion complexing agent is: Where n is 2 or 3, and the molecular weight is between 280-430Da.

In the above scheme, the multi-component ion complexing agent is prepared by the following method: add maleic anhydride and deionized water into the reactor with a condensing reflux device, heat up while stirring, and wait until the maleic anhydride is completely dissolved Afterwards, raise the temperature to 90-95°C, add aqueous hydrogen peroxide solution, and react at constant temperature for a period of time, then add sodium hydroxide solution to continue the reaction. After the reaction, the product is spray-dried to obtain a complex 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 aqueous solution, and 100 parts of sodium hydroxide solution; The volume concentration of the hydrogen solution is 25%-35%, and the molar concentration of the sodium hydroxide solution is 0.1mol/L-0.15mol/L.

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

In the above scheme, 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 concrete self-repairing functional admixture includes the following steps: 1) Weighing 40-60 parts of multi-ion complexing agent, 30-50 parts of calcium bicarbonate, and 1-50 parts of water-absorbing resin according to the weight ratio of each raw material. 5 parts; 2) Add 40-60 parts of multi-ion complexing agent, 30-50 parts of calcium bicarbonate, and 1-5 parts of water-absorbent resin into the mixer and mix mechanically for 5 minutes to obtain the concrete self-repairing function admixture .

The multiple ion complexing agent synthesized by the present invention is formed by the reaction of 2 or 3 maleic anhydrides, and the molecular structural formula is:

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

The beneficial effects of the present invention are as follows:

(1) The concrete self-repairing function admixture described in the present invention is prepared from multiple ion complexing agents, calcium bicarbonate, and water-absorbent resins, wherein the multiple ion complexing agents contain multiple complexing units, which can complex more A large number of calcium ions; the calcium bicarbonate can provide calcium ions and carbonate ions by hydrolysis; the multi-ion complexing agent forms a soluble complex with free calcium ions in concrete and calcium ions produced by calcium bicarbonate hydrolysis. 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 infiltrated into the concrete) The generated carbonate ions) react to generate calcium silicate and calcium carbonate precipitation to repair damage and cracks; the number of ions that can be complexed by the multi-component ion complexing agent is large, and the source of calcium ions in the functional admixture is sufficient, and at the same time, the water-absorbent resin is used The super water absorption capacity keeps the concrete in a wet state for a long time, ensures the continuous progress of the self-repair process, and greatly improves the self-repair ability of the functional admixture to the internal damage of the concrete and wider cracks. The functional admixture has Strong self-healing ability, good self-healing effect for wide cracks, etc.;

(2) The multi-ion complexing agent described in the present invention has a linear molecular structure, and the complex formed by it and calcium ions migrates quickly in the pores or cracks of concrete, and also easily passes through the tiny pores, which is conducive to complexation The speed of migration of substances to concrete micro-cracks and cracks has the advantage of fast repair speed;

(3) The multiple 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 retardation effect, and has stronger practicability. It is used in the field of concrete self-repair It has strong application and promotion value.

Description of drawings

Fig. 1 is the crack self-healing photo of ordinary concrete (control group) without adding the self-repairing functional admixture of the present invention, wherein the left picture is the initial crack; the right picture is the crack after standard maintenance 28d.

Fig. 2 is a self-healing photo 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 28 days of standard curing.

Detailed ways

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

In the following examples, the multi-ion complexing agent is prepared by the following method: add 200 parts of deionized water and 200 parts of maleic anhydride in a 1000ml three-necked flask equipped with condensation reflux, and make the maleic anhydride Dissolve everything, heat to 90-95°C, add 30 parts of 30vt% aqueous hydrogen peroxide solution, react at constant temperature for 4 hours, then add 100 parts of 0.12mol/L sodium hydroxide solution, react for 1.5 hours, and then spray dry to prepare multi-ion complexing agent.

Example 1

A concrete self-repairing functional admixture is prepared by the following method: weighing 53 parts of multi-ion complexing agent, 45 parts of calcium bicarbonate, and 2 parts of acrylic acid-acrylamide copolymerized water-absorbing resin, adding them into a mixer and mechanically stirring for 5 minutes to obtain Concrete self-repair function admixture.

Example 2

A concrete self-repairing functional admixture is prepared by the following method: weighing 53 parts of multi-ion complexing agent, 43 parts of calcium bicarbonate, and 4 parts of acrylic acid-acrylamide copolymerized water-absorbing resin, adding them into a mixer and mechanically stirring for 5 minutes to obtain Concrete self-repair function admixture.

Weigh cement, gravel, mineral powder, sand, water, water reducing agent and the concrete self-repairing 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-repairing functional admixture to the concrete mixer and mix for 30 seconds, then add water reducer and water into the mixer and mix for 120 seconds to obtain concrete with crack self-repairing function; the control group The concrete self-repairing function admixture is not added in the concrete, other conditions are the same.

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

(1) A part of the repaired concrete and the concrete of the control group were taken, respectively added to the mold of 100mm×100mm×100mm, demoulded after 1 day, put into the curing room for 28 days, and the specimens were taken out according to the national standard GB/T50082-2009 200 slow freeze-thaw cycles, take out the specimen after the freeze-thaw cycle, water and maintain for 28 days (watering once every 4 days), test the compressive strength of the specimen before and after the freeze-thaw cycle and after watering and curing. The compressive strength of the self-repairing concrete before the freeze-thaw cycle of embodiment 1 is 43.2MPa, the compressive strength after the freeze-thaw cycle is 35.8MPa, and the compressive strength after watering and curing is 39.8MPa; The compressive strength is 42.5MPa, the compressive strength after 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 freeze-thaw cycle is 41.8MPa, and the compressive strength after freeze-thaw cycle is 31.7MPa, and the compressive strength after watering and curing is 32.6MPa. The test results show that the internal damage caused by the freeze-thaw cycle of ordinary concrete (control group) cannot heal after 28 days of curing, while the internal damage of the concrete mixed with the self-repairing functional admixture has been well cured after the freeze-thaw cycle Repair (the recovery rate of compressive strength in embodiment 1 is 92.1%, and the recovery rate of compressive strength in embodiment 2 is 95.5%); compared with embodiment 1, the water-absorbent resin in the self-repairing functional admixture used in embodiment 2 increases, and the concrete The damage self-healing ability is further improved.

(2) Parts of the repaired concrete and the concrete of the control group were respectively poured into the anti-cracking mold of the concrete slab, and immediately blown with a fan for 4 hours after vibrating and smoothing, and the wind speed at the center of the concrete specimen was kept not less than 5m/s, so that the concrete produced For cracks, the initial cracks were measured, and then watered and cured (watering once every 4 days), and when the curing reached 7 days, 14 days, 21 days and 28 days, the crack widths were measured respectively. The crack width measurements are listed in Table 2. It can be seen from Table 2 that the crack self-healing ability of ordinary concrete in the control group is very weak, and the crack width basically does not change with the prolongation of curing time, while the concrete mixed with self-repairing functional admixture not only self-repairs small cracks (less than 0.2mm) Effect is very good, also showed very strong crack self-healing ability to wider crack (greater than 0.3mm); Compared with embodiment 1, the water-absorbent resin in the self-repair function admixture used in embodiment 2 increases, and the crack of concrete The self-healing ability is further enhanced.

Table 1 Concrete Proportion

Changes in crack width in the concrete curing process prepared by table 2 embodiment 1, 2 and control group

Example 3

A concrete self-repairing functional admixture is prepared by the following method: weighing 53 parts of multi-ion complexing agent, 45 parts of calcium bicarbonate, and 3 parts of acrylic acid-acrylamide copolymerized water-absorbing resin, adding them into a mixer and mechanically stirring for 5 minutes to obtain Concrete self-repair function admixture.

Example 4

A concrete self-repairing functional admixture is prepared by the following method: Weigh 57 parts of multi-ion complexing agent, 40 parts of calcium bicarbonate, and 3 parts of acrylic acid-acrylamide copolymerized water-absorbing resin, add them into a mixer and stir mechanically for 5 minutes to obtain Concrete self-repair function admixture.

Weigh cement, crushed stone, mineral powder, sand, water, water reducing agent and the concrete self-repairing functional 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-repairing functional admixture to the concrete mixer and mix for 30 seconds, then add water reducer and water into the mixer and mix for 120 seconds to obtain concrete with crack self-repairing function; the control group The concrete self-repairing function admixture is not added in the concrete, other conditions are the same.

Freeze-thaw damage self-repair and crack self-repair tests were carried out on the self-repair concrete prepared above and the control group concrete respectively:

(1) A part of the repaired concrete and the concrete of the control group were taken, respectively added to the mold of 100mm×100mm×100mm, demoulded after 1 day, put into the curing room for 28 days, and the specimens were taken out 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 and cured 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-repairing concrete before the freeze-thaw cycle is 59.3MPa, the compressive strength after the freeze-thaw cycle is 50.4MPa, and the compressive strength after watering and curing is 55.0MPa; the compressive strength of the self-repairing concrete before the freeze-thaw cycle of embodiment 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 concrete in the comparison group is 57.5MPa before the freeze-thaw cycle, 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 has not healed after 28 days of curing, while the internal damage of concrete mixed with self-repairing functional admixtures has been healed after curing. Very good repair; Compared with Example 3, the content of multiple ion complexing agent in the self-repairing functional admixture used in Example 4 is increased, and the internal damage self-repairing ability of concrete is further improved.

(2) Parts of the repaired concrete and the concrete of the control group were respectively poured into the anti-cracking mold of the concrete slab, and immediately blown with a fan for 4 hours after vibrating and smoothing, and the wind speed at the center of the concrete specimen was kept not less than 5m/s, so that the concrete produced For cracks, the initial cracks were measured, and then watered and cured (watering once every 4 days). When the curing reached 7 days, 14 days, 21 days and 28 days, the crack widths were measured respectively. 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 has basically no change, while the crack repair ability of the concrete mixed with functional admixtures prepared in Examples 3 and 4 has been significantly improved. Compared with Example 3, the content of multi-component ion complexing agent in the self-repairing functional admixture used in Example 4 is increased, the crack self-repair ability of concrete is further improved, and the cracks above 0.7mm also have self-repair ability.

Table 3 Concrete Proportion

Changes in crack width in the concrete curing process prepared by table 4 embodiment 3, 4 and control group

Example 5

A concrete self-repairing functional admixture, prepared by the following method: weighing 40 parts of multi-ion complexing agent, 50 parts of calcium bicarbonate, 5 parts of acrylic acid-acrylamide copolymer water-absorbing resin; weighing the multi-ion complexing agent , calcium bicarbonate, and water-absorbent resin were added to the mixer and mechanically mixed for 5 minutes to obtain the concrete self-repairing functional admixture.

Example 6

A concrete self-repairing functional admixture, prepared by the following method: weighing 60 parts of multi-ion complexing agent, 30 parts of calcium bicarbonate, 1 part of acrylic acid-acrylamide copolymer water-absorbing resin; weighing the multi-ion complexing agent , calcium bicarbonate, and water-absorbent resin were added to the mixer and mechanically mixed for 5 minutes to obtain the concrete self-repairing functional admixture.

Apparently, the above-mentioned embodiments are only examples for clear illustration, rather than limiting the implementation. For those of ordinary skill in the art, on the basis of the above description, other changes or changes in different forms can also be made. It is not necessary and impossible to exhaustively list all the implementation manners here. However, the obvious changes or modifications thus extended are still within the scope of protection of the present invention.

Claims (7)

1. A concrete self-repairing functional admixture is characterized in that it is prepared by mixing multiple ion complexing agents, calcium bicarbonate, and water-absorbent resins, and each raw material is calculated in parts by weight: multiple ion complexing agents 40～ 60 parts, calcium bicarbonate 40-50 parts, water-absorbent resin 1-5 parts. 2. the concrete self-repairing function admixture according to claim 1, is characterized in that, the molecular structural formula of described multiple ion complexing agent is: Wherein n is 2 or 3, and the molecular weight is between 280-430Da. 3. The concrete self-repairing function admixture according to claim 1, is characterized in that, said multi-component ion complexing agent is prepared by the following method: maleic anhydride and deionized water are added to a condensing reflux device for reaction In the container, heat up while stirring. After the maleic anhydride is completely dissolved, heat up to 90-95°C, add aqueous hydrogen peroxide solution, and react at constant temperature for a period of time, then add sodium hydroxide solution to continue the reaction. After the reaction is completed, The product is spray-dried to obtain a complex ion complexing agent. 4. The concrete self-repairing function admixture according to claim 3 is characterized in that, in the preparation method, each raw material is counted as: 100 parts of maleic anhydride, 100 parts of deionized water, peroxidized 30 parts of hydrogen solution, 100 parts of sodium hydroxide solution; the volume concentration of the hydrogen peroxide solution is 25% to 35%, and the molar concentration of the sodium hydroxide solution is 0.1mol/L to 0.15mol/L. 5. The concrete self-repairing functional admixture according to claim 3, characterized in that, in the preparation method, the constant temperature reaction time is 3h-5h, adding sodium hydroxide solution to continue the reaction for 1h-2h. 6 . The admixture with self-repairing function for concrete according to claim 1 , wherein the water-absorbing resin is an acrylic acid-acrylamide copolymerized water-absorbing resin with a water absorption ratio of 100-300. 7. The preparation method of the concrete self-repairing functional admixture described in any one of claims 1 to 6, is characterized in that it comprises the following steps: 1) taking 40 to 60 parts of multiple ion complexing agents according to the weight and number ratio of each raw material , 30-50 parts of calcium bicarbonate, and 1-5 parts of water-absorbent resin; Mix mechanically in the machine for 5 minutes to obtain the concrete self-repairing functional admixture.