CN112851219A - Repair mortar for concrete member and preparation method thereof - Google Patents

Abstract

The application discloses repair mortar for a concrete member and a preparation method thereof, and relates to the technical field of cement-based mortar. The repair mortar for the concrete member is mainly prepared from 1060 parts by weight of admixture and 1060 parts by weight of internal admixture, wherein the admixture comprises the following raw materials in parts by weight based on the total weight of the repair mortar: 0.5-1.5 parts of defoaming agent, 20-30 parts of expanding agent, 25-35 parts of rubber powder and 8-12 parts of water reducing agent; the internal admixture comprises the following raw materials in parts by weight based on the total weight of the internal admixture: 85-105 parts of water, 390-420 parts of cement, 20-35 parts of silica fume, 20-35 parts of accelerator and 550 parts of graded sand. It has the advantage of high bonding strength. The preparation method comprises the following steps: preparing admixtures, sand mixing, mortar and the like; the preparation method has the advantage of improving the bonding strength of the product.

Description

Repair mortar for concrete member and preparation method thereof

Technical Field

The application relates to the technical field of cement-based mortar, in particular to repair mortar for a concrete member and a preparation method thereof.

Background

With the development of the concrete industry, the precast concrete is widely used gradually due to the advantages of convenient construction, convenient recovery and the like, and the specific gravity of the precast concrete is gradually increased in the concrete industry. However, due to the process or manpower, the precast concrete has defects of pot holes, corner falling and the like in the processes of precast, transportation and installation of the concrete.

In order to prevent the defects from being enlarged, the defects of the precast concrete need to be repaired by using repair mortar. The commonly used repair mortar at present is made of raw materials such as cement, quartz sand and the like, is used for repairing the defects of the concrete member and is beneficial to preventing the defects of the concrete member from being continuously expanded.

In view of the above-mentioned related technologies, the inventors believe that after the concrete member is repaired by the repair mortar, the repair mortar is not usually subjected to moisture retention and heat preservation maintenance due to limited conditions of a construction site, and the repair mortar is prone to shrinkage cracking; meanwhile, the repair amount of the defect part is small, the repair layer is thin, the dispersion of water in the slurry is too fast, the bonding strength and the mechanical strength of the repair mortar are reduced to a certain extent, and certain adverse effect is brought to the service life of the repair mortar.

Disclosure of Invention

In order to improve the bonding strength of the repair mortar, the application provides the repair mortar for the concrete member and the preparation method thereof.

In a first aspect, the present application provides a repair mortar for a concrete member, which adopts the following technical scheme:

the repair mortar for the concrete member is mainly prepared from 1060 parts by weight of admixture and 1060 parts by weight of internal admixture, wherein the admixture comprises the following raw materials in parts by weight based on the total weight of the repair mortar: 0.5-1.5 parts of defoaming agent, 20-30 parts of expanding agent, 25-35 parts of rubber powder and 8-12 parts of water reducing agent; the internal admixture comprises the following raw materials in parts by weight based on the total weight of the internal admixture: 85-105 parts of water, 390-420 parts of cement, 20-35 parts of silica fume, 20-35 parts of accelerator and 550 parts of graded sand.

By adopting the technical scheme, the quick-setting admixture is added into the internal admixture by an internal admixture method in the raw materials for preparing the repair mortar, the rubber powder and the expanding agent are added into the external admixture by an external admixture method, the rubber powder is flexible redispersible rubber powder, a flexible network structure is formed after film forming, products of cement hydration in the repair mortar are connected into an organic whole, and the bonding strength of the repair mortar is improved; the accelerator is added to act together with the rubber powder and the cement, so that the setting and hardening time can be adjusted, and the requirements on repairing different parts of the concrete member can be met; the expanding agent is added to generate micro expansion, the shrinkage caused by hydration of the cementing material is compensated, the volume stability of the repair mortar is improved, and the expanding agent and the rubber powder have synergistic effect, so that the shrinkage is reduced, and the cracking risk is reduced. The combined action of the expanding agent, the rubber powder and the accelerating agent is beneficial to adjusting the mortar setting time, so that the mortar has a proper working period, the volume stability of the repair mortar is improved, the bonding strength of the repair mortar is improved, the compressive strength and the flexural strength of the repair mortar are improved, and the strength performance of the repair mortar is improved.

Preferably, the graded sand comprises the following graded sand raw materials in parts by weight: 90-110 parts of sand with the particle size of 0.075-0.15mm, 170 parts of 130-containing sand with the particle size of 0.15-0.3mm and 270 parts of 230-containing sand with the particle size of 0.3-0.6 mm.

By adopting the technical scheme, the sand with three levels of different particle sizes is compounded, so that the sand is favorably compacted and stacked to form a stable aggregate framework, the volume stability of the repair mortar is favorably improved, and the strength performance of a product is favorably improved.

Preferably, the admixture further comprises 0.6 to 1.2 parts by weight of hydroxymethyl propyl cellulose ether and 0.6 to 1.2 parts by weight of starch ether.

By adopting the technical scheme, the hydroxymethyl propyl cellulose ether is added, so that the mortar has certain consistency, the bleeding phenomenon is favorably prevented, the starch ether is added, the water retention of the repair mortar product is favorably improved, the repair mortar is convenient to scrape and coat, and the constructability of the repair mortar is favorably improved.

Preferably, the admixture and the accelerator are powder soluble in room temperature water.

By adopting the technical scheme, the admixture and the accelerating agent are both powder materials, cement, silica fume, the accelerating agent and the admixture are mixed to prepare the powder materials during factory production, the graded sand raw materials are mixed to prepare the graded sand, and the graded sand raw materials can be used by directly adding water and mixing on a construction site, so that the product construction is facilitated, and the product constructability is improved.

Preferably, the water reducing agent is a powder shrinkage-reducing polycarboxylic acid water reducing agent; the expanding agent is a plastic expanding agent.

By adopting the technical scheme, the powder shrinkage-reducing polycarboxylic acid water reducing agent has high water reducing rate, is beneficial to fully hydrating cement and improving the mechanical strength of products. The use of the plastic expanding agent helps to prevent the repair mortar from cracking and to improve the flexural strength of the product.

Preferably, the compressive strength ratio of the accelerator 28d is not less than 90%.

By adopting the technical scheme, the accelerating agent with excellent performance is selected, and the compressive strength of the repair mortar is favorably improved.

Preferably, the rubber powder is saponification-resistant redispersible vinyl acetate/ethylene copolymer rubber powder, the particle size of the rubber powder is 0.5-8um, and the rubber powder contains a polyvinyl alcohol stabilizer.

By adopting the technical scheme, the rubber powder forms a flexible network structure after film forming, hydration products can be organically connected into a whole, and the improvement of the bonding strength of the repair mortar is facilitated; the use of the anti-saponification and the rubber powder containing a proper stabilizer contributes to the improvement of the volume stability of the mortar and the improvement of the strength performance of the mortar.

Preferably, the silica fume activity index is more than 105%, and the water demand ratio is less than 115%.

By adopting the technical scheme, the silica fume with proper activity is used, so that the compactness of the repaired matrix and the transition area is improved, and the bonding strength of the repair mortar is improved.

In a second aspect, the present application provides a method for preparing a repair mortar for a concrete member, which adopts the following technical scheme:

a preparation method of repair mortar for concrete members comprises the following steps:

s1 admixture: adding silica fume, an accelerating agent and an additive into cement, and uniformly mixing to obtain a powder material;

s2 sand mixing: taking dry graded sand raw materials, and uniformly mixing to prepare graded sand;

preparing S3 mortar: taking water, adding the powder material, stirring at a rotating speed of not less than 60 revolutions per minute for 90-300s, adding the graded sand, and continuously stirring for 90-300s to prepare the repair mortar for the concrete member.

By adopting the technical scheme, water is added into the stirring pot at first, and then the powder material is added, so that the powder material is prevented from being adhered to the bottom, the loss is reduced, and the product constructability is improved.

In summary, the present application includes at least one of the following beneficial technical effects:

1. according to the method, the quick-setting agent is added into the internal admixture by an internal doping method in raw materials for preparing the repair mortar, the rubber powder and the expanding agent are added into the external admixture by an external doping method, the rubber powder is flexible redispersible rubber powder, a flexible network structure is formed after film formation, hydration products of cement in the mortar are connected into an organic whole, and the bonding strength of the repair mortar is improved; the accelerator is added to act together with the rubber powder and the cement, so that the setting time can be adjusted, and the requirements for repairing different parts of the concrete member can be met; the expanding agent is added to generate micro expansion, and the micro expansion and the rubber powder have synergistic effect, so that the shrinkage is reduced, and the cracking risk is reduced; the expansion agent, the rubber powder and the accelerator act together, so that the mortar is beneficial to adjusting the mortar setting time, has a proper working period, improves the mortar volume stability, improves the mortar bonding strength, improves the compressive strength and the flexural strength of the repair mortar, and improves the strength performance of the repair mortar;

2. this application still has following advantage: by adding the water reducing agent and the silica fume, the workability of the mortar is improved, the repaired interface is compact, the water-cement ratio is reduced, and the strength is improved; the addition of the rubber powder forms a space network structure in the mortar, so that the bonding strength of the repair mortar is improved; the hydroxymethyl propyl cellulose ether and the starch ether are added, so that the scraping effect of the mortar is improved, and the sagging resistance of the repair mortar is improved; the use of the expanding agent and the tertiary sand preparation contributes to improving the volume stability of the mortar and reducing the cracking risk; the accelerator is added, so that the working time of the mortar can be regulated and controlled, and the product construction is facilitated; adding a powder material into water, stirring to prepare slurry, and then adding aggregate to realize a slurry sand-wrapping process, which is beneficial to further strengthening an interface transition region and improving the strength; the repair mortar prepared by the method and the component are cured under the same condition, and the heat preservation and moisture preservation maintenance is not needed, so that the good bonding strength and the self strength of the mortar can be achieved;

3. the admixture and the accelerator are all made of powder materials, cement, silica fume, the accelerator and the admixture are mixed to prepare the powder materials during factory production, the graded sand raw materials are mixed to prepare graded sand, and the graded sand can be used after being directly stirred by adding water in a construction site, so that the product construction is facilitated, and the product constructability is improved; the powder-based shrinkage-reducing polycarboxylate superplasticizer has high water reducing rate, is beneficial to fully hydrating cement and improving the mechanical strength of products.

Detailed Description

The inventor finds that the shrinkage and cracking phenomena are easy to occur after the common mortar is used for repairing the concrete member in the research process, and the probability of the cracking phenomena can be reduced after moisture preservation and heat preservation maintenance are needed. In the actual use process, due to the limited conditions of the construction site, the concrete member can only be synchronously maintained without moisture preservation and heat preservation maintenance, and the repairing mortar is easy to shrink and crack; and because the repair amount of the defect part is small, the repair layer is thin, the water in the slurry is dispersed and lost too fast, the bonding strength of the repair mortar is reduced, the self strength of the repair mortar is reduced, certain adverse effect is brought to the service life of the repair mortar, and the repair mortar cannot keep the synchronous service life with the concrete matrix member easily. Based on the technical background, the application provides a technical scheme capable of improving the strength performance of the repair mortar, and the service life of the concrete member can be reached or exceeded under the condition of synchronous maintenance of the concrete member by improving the self strength of the repair mortar, so that the effect of one-time repair and lifelong use is facilitated to be realized. The following embodiments are specifically described.

In the application, the silica fume and the accelerating agent are added by adopting an internal mixing method, and the silica fume is added to ensure that the repaired matrix and the transition region are more compact, thereby being beneficial to improving the bonding strength; in the actual use process, the dosage of the accelerator can be adjusted according to different repaired parts and working conditions. The rubber powder, the expanding agent, the water reducing agent, the defoaming agent and other additives adopt an external doping method.

Examples

The raw materials referred to in the present application are all commercially available, and the type and source of the raw materials are shown in table 1.

TABLE 1 Specification, type and origin of the raw materials

The following examples illustrate dry, clean silica sand produced in Sichuan and having three sizes of sand, respectively: sand with a particle size of 0.075-0.15mm, sand with a particle size of 0.15-0.3mm and sand with a particle size of 0.3-0.6 mm.

Examples

Example 1: the repair mortar for the concrete member is prepared by the following method, and comprises the following steps:

s1 admixture: 418.5kg of cement is taken, 28kg of silica fume, 23.5kg of expanding agent, 23.5kg of accelerating agent, 28.2kg of rubber powder, 0.94kg of defoaming agent and 9.4kg of shrinkage-reducing polycarboxylate superplasticizer are added, and the materials are uniformly mixed to prepare the powder material.

Preparing S2 mortar: and (2) pouring 90kg of water into a stirring pot, adding the powder material, stirring at the rotating speed of 70 r/min for 120s, adding 500kg of dried sand with the particle size of 0.15-0.3mm, and continuously stirring for 120s to prepare the repair mortar for the concrete member.

Example 2: the repair mortar for the concrete member is prepared by the following method, and comprises the following steps:

s1 admixture: 418.5kg of cement is taken, 28kg of silica fume, 23.5kg of plastic expanding agent, 23.5kg of accelerating agent, 28.2kg of rubber powder, 0.94kg of defoaming agent and 9.4kg of shrinkage-reducing polycarboxylic acid water reducing agent are added, and the mixture is uniformly mixed to prepare the powder material.

S2 sand mixing: 100kg of sand with the particle size of 0.075-0.15mm is taken, 150kg of sand with the particle size of 0.15-0.3mm and 250kg of sand with the particle size of 0.3-0.6mm, the sand is dried sand, and the materials are uniformly mixed to prepare the graded sand.

Preparing S3 mortar: and (3) pouring 90kg of water into a stirring pot, adding the powder material, stirring at the rotating speed of 70 revolutions per minute for 120s, adding the graded sand, and continuously stirring for 120s to prepare the repair mortar for the concrete member.

Examples 3 to 6

Examples 3 to 6 are different from example 2 in the addition amount of each raw material of examples 3 to 6, and the addition amount of each raw material of examples 3 to 6 is the same as that of example 2, and the addition amount of each raw material of examples 3 to 6 is shown in Table 2.

TABLE 2 addition amounts of the respective raw materials of examples 3 to 6

Example 7

Example 7 differs from example 2 in that 0.9kg of hydroxymethylpropyl cellulose ether was added to example 7, all otherwise in accordance with example 2.

Example 8

Example 8 differs from example 2 in that 0.9kg of starch ether was added to example 8, all otherwise in accordance with example 2.

Example 9

Example 9 differs from example 8 in that 0.9kg of hydroxymethylpropyl cellulose ether was added to example 9, all otherwise in accordance with example 8.

Examples 10 to 15

Examples 10 to 15 are different from example 9 in that the amounts of the respective raw materials of examples 10 to 15 were different from each other and the amounts of the respective raw materials of examples 10 to 15 were the same as those of example 9, and the amounts of the respective raw materials of examples 10 to 15 were shown in Table 3.

TABLE 3 addition amounts of respective raw materials of examples 10 to 15

Example 16

Example 16 differs from example 9 in that the feeding sequence in step S3 of example 16 is different, the graded sand is added to the water in step S3 of example 16, the powder material is added after stirring for 120S, and the rest is the same as example 9,

examples 17 to 21

Examples 17-21 differ from example 9 in that the process parameters for each step of examples 17-21 are different and are otherwise identical to those of example 9, and the process parameters for each step of examples 17-21 are shown in Table 4.

TABLE 4 Process parameters for the various steps of examples 17-21

Comparative example

Comparative example 1

Comparative example 1 differs from example 1 in that comparative example 1 does not have the addition of a swelling agent, a rubber powder and an accelerator, all of which are in accordance with example 1.

Comparative example 2

Comparative example 2 differs from example 1 in that comparative example 2 does not have the addition of a swelling agent and an accelerator, and the rest remains the same as example 1.

Comparative example 3

Comparative example 3 differs from example 1 in that comparative example 3 does not have added glue powder and otherwise remains the same as example 1.

Performance detection

1. Fluidity: the initial fluidity and 20min fluidity retention were measured according to GBT2419-2005 "cement mortar fluidity determination method", and the experimental results are shown in Table 5.

2. Setting time: the initial setting time and final setting time were measured with reference to JC/T2381-2016 repair mortar, and the results are shown in Table 5.

3. Strength: referring to GBT17671-1999 method for testing cement mortar strength (ISO method), samples with dimensions of 40mm by 160mm were made and tested for compressive strength and flexural strength at 28d, and the test results are shown in Table 5.

4. Tensile bond strength: the tensile bond strength was tested with reference to JC/T2381-2016 repair mortar, and the results are shown in Table 5.

5. Dry shrinkage rate: the dry shrinkage of 28d is tested according to JC/T2381-2016 repair mortar, and the experimental results are shown in Table 5.

TABLE 5 comparison table of performance test results of different repair mortar products

Compared with the embodiment 1, the comparative example 1 does not add the expanding agent, the rubber powder and the accelerating agent, and the prepared repair mortar product has poor compressive strength, flexural strength and bonding strength, is not beneficial to prolonging the service life of the product and is not beneficial to market popularization of the product. Compared with the comparative example 1 and the comparative example 2, the expansion agent and the accelerating agent are not added, and the rubber powder is added, so that the strength performance of the prepared repair mortar product is not changed greatly. In the comparative example 3, no rubber powder is added, and the expanding agent and the accelerating agent are added, so that the compressive strength of the prepared repair mortar product is slightly improved, but the strength performance is still poor, the service life of the product is not prolonged, and the market popularization of the product is not facilitated.

Comparing the experimental results of the example 1 and the comparative examples 1 to 3, it can be seen that, in the process of preparing the repair mortar, the expanding agent, the rubber powder and the accelerating agent are added, and due to the combined action of the expanding agent, the rubber powder and the accelerating agent, the compressive strength, the flexural strength and the bonding strength of the prepared repair mortar product are all improved, the strength performance is obviously improved, the service life of the product is prolonged, and the market popularization of the product is facilitated.

Comparing the experimental results of the embodiment 1 and the embodiment 2, the embodiment 2 uses the third-level clean quartz sand, the third-level clean quartz sand can realize tight packing, a stable aggregate skeleton is formed, the volume stability of the repair mortar is improved, and the compressive strength of the prepared repair mortar product is obviously improved. Compared with the comparative example 2 and the examples 3 to 6, the prepared repair mortar product has excellent strength property, is beneficial to prolonging the service life of the product and is beneficial to market popularization of the product due to different addition amounts of the raw materials.

Compared with the experimental results of the embodiment 2 and the embodiment 7, the hydroxymethyl propyl cellulose ether is added into the admixture of the embodiment 7, so that the mortar has certain consistency, the bleeding phenomenon of the mortar is prevented, and the prepared repair mortar product has good construction performance and small change of strength performance. Compared with the experimental results of the embodiment 2 and the embodiment 8, the starch ether is added into the admixture of the embodiment 8, which is beneficial to improving the water retention of the repair mortar product, facilitating the blade coating of the repair mortar, and improving the construction property of the repair mortar, and the strength property of the repair mortar is not changed greatly. Compared with the experimental results of the embodiment 2 and the embodiment 9, the embodiment 9 has the advantages that the hydroxymethyl propyl cellulose ether and the starch ether are added simultaneously, a certain synergistic effect exists between the hydroxymethyl propyl cellulose ether and the starch ether, the compressive strength and the flexural strength of the prepared repair mortar product are improved, the service life of the product is prolonged, and the product market popularization is facilitated.

Compared with the embodiment 9, the strength performance of the prepared repair mortar product is changed due to different addition amounts of the raw materials in the embodiments 10 to 13; compared with the examples 10 to 13, the examples 14 to 15 use better raw material feeding proportion, and the prepared repair mortar product has better strength performance, is beneficial to prolonging the service life of the product and is beneficial to market popularization of the product.

Compared with the embodiment 16, the feeding sequence of the embodiment 9 is different, the graded sand is firstly added into the water and then the powder material is added in the step S3 of the embodiment 16, the powder material is firstly added into the water and then the graded sand is added in the step S3 of the embodiment 9, the slurry sand-wrapping process is facilitated, the interface transition region is further strengthened, the strength is improved, and the repair mortar product prepared in the embodiment 9 has better strength performance. The process parameters of examples 17-21 were different compared to example 9, where the lower the stirring speed of example 17, the compressive strength of the resulting repair mortar product was slightly reduced. In the examples 18 to 21, the prepared repair mortar has excellent compression resistance by using appropriate process parameters, is beneficial to prolonging the service life of the product and is beneficial to market popularization of the product.

The embodiments of the present invention are preferred embodiments of the present application, and the scope of protection of the present application is not limited by the embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims (9)

1. The repair mortar for the concrete member is characterized by being mainly prepared from 1060 parts by weight of internal admixture and an additive, wherein the additive comprises the following raw materials in parts by weight based on the total weight of the repair mortar: 0.5-1.5 parts of defoaming agent, 20-30 parts of expanding agent, 25-35 parts of rubber powder and 8-12 parts of water reducing agent; the internal admixture comprises the following raw materials in parts by weight based on the total weight of the internal admixture: 85-105 parts of water, 390-420 parts of cement, 20-35 parts of silica fume, 20-35 parts of accelerator and 550 parts of graded sand.

2. The repair mortar for concrete members according to claim 1, wherein the graded sand comprises the following graded sand raw materials in parts by weight: 90-110 parts of sand with the particle size of 0.075-0.15mm, 170 parts of 130-containing sand with the particle size of 0.15-0.3mm and 270 parts of 230-containing sand with the particle size of 0.3-0.6 mm.

3. A repair mortar for concrete members according to claim 1, characterized in that: the admixture also comprises 0.6 to 1.2 weight portions of hydroxymethyl propyl cellulose ether and 0.6 to 1.2 weight portions of starch ether.

4. A repair mortar for concrete members according to claim 1, characterized in that: the admixture and the accelerator are powder soluble in room temperature water.

5. A repair mortar for concrete members according to claim 4, characterized in that: the water reducing agent is a powder shrinkage-reducing polycarboxylic acid water reducing agent; the expanding agent is a plastic expanding agent.

6. A repair mortar for concrete members according to claim 1, characterized in that: the 28d compressive strength ratio of the accelerator is not less than 90%.

7. A repair mortar for concrete members according to claim 1, characterized in that: the rubber powder is anti-saponification redispersible vinyl acetate/ethylene copolymer rubber powder, the particle size of the rubber powder is 0.5-8um, and the rubber powder contains a polyvinyl alcohol stabilizer.

8. A repair mortar for concrete members according to any one of claims 1 to 7, characterized in that: the silica fume activity index is more than 105 percent, and the water demand ratio is less than 115 percent.

9. A method for preparing a repair mortar for concrete elements according to any one of claims 1 to 8, characterized in that it comprises the following steps:

s1 admixture: adding silica fume, an accelerating agent and an additive into cement, and uniformly mixing to obtain a powder material;

s2 sand mixing: taking dry graded sand raw materials, and uniformly mixing to prepare graded sand;

preparing S3 mortar: taking water, adding the powder material, stirring at a rotating speed of not less than 60 revolutions per minute for 90-300s, adding the graded sand, and continuously stirring for 90-300s to prepare the repair mortar for the concrete member.