A binary composite cement-based underwater repair mortar and a method for preparing the same

Abstract

The application discloses a binary composite cement-based underwater repair mortar, which is prepared from the following raw materials in parts by weight: 360 parts of Portland cement, 90 parts of sulphoaluminate cement, 50 parts of limestone powder, 500 parts of medium sand, 0-15 parts of UWB-2 underwater non-dispersible concrete flocculating agent, 0-10 parts of re-dispersible latex powder, 2.5 parts of polycarboxylic acid high-performance powdery water reducing agent and 200 parts of water. The obtained cement-based underwater repair mortar has early setting, early strength and good flow performance, and can be used for the construction, repair and reinforcement of hydraulic concrete under static water.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a binary composite cement-based underwater repair mortar and a preparation method thereof. BACKGROUND

[0002] Hydraulic concrete buildings and structures (dams, sluices, discharge tunnels, piers, wharfs, etc.) are in natural conditions and complex underwater environments, and concrete is prone to performance deterioration, resulting in defects such as concrete spalling and cracking, which may cause certain safety hazards. However, it is very difficult to repair concrete in a moist environment or underwater, and the repair material and process have high requirements, otherwise the repair effect may be poor.

[0003] Underwater repair materials include organic grouting materials and inorganic grouting materials, the latter belongs to cement-based repair materials and is prepared from cement, sand, stone, anti-dispersing agent and other additives as a base. The raw materials are easy to obtain, the price is relatively low, the preparation process is simple, and the construction is convenient, and there is a corresponding technical specification. The most widely researched and applied at present is ordinary Portland cement-based underwater repair material, but it has the disadvantages of excessive loss of paste fluidity, excessively low early strength, excessively long setting time in water, and paste easy to be dispersed by water flow. When repairing hydraulic concrete buildings, early strength, setting time and fluidity of the repair material are required. Therefore, it is necessary to develop high-performance cement-based underwater repair materials to improve the early strength, early setting and fluidity of cement-based underwater repair materials. SUMMARY

[0004] In view of the deficiencies of the prior art, the application provides a binary composite cement-based underwater repair mortar and a preparation method thereof, which belong to the technical field of building materials. The cement-based underwater repair mortar obtained by the application has early setting, early strength and good fluidity, and can be used for the construction, repair and reinforcement of hydraulic concrete underwater.

[0005] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0006] A binary composite cement-based underwater repair mortar is composed of the following raw materials in parts by weight: 360 parts of Portland cement, 90 parts of sulphoaluminate cement, 50 parts of limestone powder, 500 parts of medium sand, 0-15 parts of UWB-2 underwater non-dispersible concrete flocculating agent, 0-10 parts of re-dispersible latex powder, 2.5 parts of polycarboxylic acid high-performance powdery water reducing agent, and 200 parts of water.

[0007] Further, the Portland cement has a type of P.O 42.5-52.5 and a density of 3100-3250 kg / m³, and the quality index meets the requirements of the General Portland Cement (GB 175-2007).

[0008] Further, the type of the sulphoaluminate cement is CSA 42.5-52.5, and the density is 3100-3250 kg / m³, which meets the requirements of the General Sulphoaluminate Cement (GB 20472-2006).

[0009] Further, the limestone powder contains 86wt%-99wt% of CaCO3, and the fineness (75 μm sieve residue) is less than 5.0%, which meets the requirements of the Technical Specification for Limestone Powder Mixed with Hydraulic Concrete (DL / T 5304-2013).

[0010] Further, the medium sand is a river sand for construction, and the particle size is in the range of 0.5-1.0 mm, and the fineness modulus is about 2.5.

[0011] Further, the UWB-2 underwater non-dispersive concrete flocculant provides anti-dispersivity, fluidity and construction performance for the repair mortar.

[0012] Further, the redispersible latex powder is a copolymer of vinyl acetate and ethylene.

[0013] Further, the polycarboxylic acid high-performance powdery water-reducing agent has a water-reducing rate of 25-45%, which plays a role in water-reducing and slump-keeping.

[0014] The preparation method of the binary composite cement-based underwater repair mortar comprises the following steps:

[0015] (1) Preparation of mechanically-chemically modified cementitious material: the portland cement, the sulphoaluminate cement and the limestone powder are mixed and dried according to the proportion, then poured into a ball mill jar for ball milling to realize the mechanical-chemical effect, and then all the powders are sieved out with a screen and stored in a sealed bag to obtain the modified cementitious material;

[0016] (2) The modified cementitious material obtained in step (1), the medium sand, the UWB-2 underwater non-dispersive concrete flocculant, the redispersible latex powder and the polycarboxylic acid high-performance powdery water-reducing agent are dry-mixed in a mixer at a low speed for 30 s until the dry materials are uniformly mixed, then water is added, and the low-speed stirring is continued for 30 s, followed by high-speed stirring for 30 s, then paused for 90 s, and then high-speed stirring for 60 s, so that the uniform repair mortar is obtained.

[0017] Further, the total mass ratio of the steel balls to the materials used in the ball milling in step (1) is 7.5:1; the ball milling time is 30 min, and the rotating speed is 75 r / min.

[0018] Further, the rotating speed used in the low-speed stirring in step (2) is 140 r / min, and the rotating speed used in the high-speed stirring is 285 r / min.

[0019] The application compounding sulphoaluminate cement and Portland cement as the base of underwater repair mortar, internally mixing mineral admixture limestone powder to replace cement, and adopting mechano-chemical modification of cementitious materials, and through mixing UWB-2 underwater non-dispersible concrete flocculating agent, redispersible latex powder, medium sand, polycarboxylate high-performance powder water reducing agent, etc., an underwater repair material with early strength, early setting, high rheological property and high strength is prepared.

[0020] On the cement component, the sulphoaluminate cement and the ordinary Portland cement are compounded in proportion, which can achieve the effect of complementary advantages, can not only improve the working performance of single cement, but also shorten the setting time of the composite material system, improve the early strength and the resistance to chloride ion penetration and the like.

[0021] After the mineral admixture limestone powder is replaced by cement in a certain proportion, the fluidity of the slurry can be improved, and it belongs to solid waste utilization, which has significant economic and social benefits.

[0022] The underwater anti-dispersant is crucial in hydraulic concrete building structures. The UWB-2 underwater non-dispersible concrete flocculating agent is a water-soluble polymer material containing a long-chain structure, which can generate ionic bonds or covalent bonds on the surface of cement particles, firmly connecting the cement fine particles together, thereby increasing the viscosity of the slurry to prevent the slurry from segregating and dispersing during underwater construction. However, the anti-dispersant, while improving the anti-dispersibility of the mortar, also leads to problems such as loss of fluidity, prolonged setting time, and reduced mechanical properties, so the amount of the anti-dispersant is very important.

[0023] The redispersible latex powder can be used to improve the flexibility, water resistance and adhesion of the mortar, thereby imparting certain anti-dispersibility to the underwater mortar. The polymer component in the redispersible latex powder can form a film after dispersion in water, which surrounds the cement and fine aggregate particles, acting like a lubricant to reduce internal friction, thereby improving the anti-dispersibility of the mortar while reducing the loss of fluidity.

[0024] Mechano-chemistry can improve the activity of cement and mineral admixtures, accelerate the hydration reaction rate, and increase the fluidity and stability of cementitious materials. Mechano-chemistry can change the particle morphology and distribution of powdered mineral materials, reduce the particle size of cementitious materials, increase the specific surface area, thereby reducing the water demand of cementitious materials and improving their rheological properties. Mechano-chemistry can adjust the chemical composition and microstructure of powdered mineral materials, improve the hydration reaction rate, and control the setting time and strength development of cementitious materials.

[0025] The advantages of the application are:

[0026] (1) The sulphoaluminate cement is mixed into the ordinary Portland cement, so that the setting time of the underwater repair material can be shortened, the early strength and the chloride ion penetration resistance can be improved, the micro-expansion effect of the sulphoaluminate cement during hydration is beneficial to fill the small cracks and gaps, the sealing effect is improved, and the underwater repair mortar has better durability and stability.

[0027] (2) The limestone powder as the mineral admixture can improve the workability of the mortar, reduce the bleeding and segregation, improve the self-leveling ability of the mortar, and promote the repair mortar to fully fill the cracks of the repaired test piece, so that the good working performance is achieved.

[0028] (3) The cement for the underwater repair material is prepared by the mechanical force chemical method. The fine grinding of the cement can optimize the particle size distribution of the cement, improve the mixing property of the cement and water, and then improve the fluidity of the slurry, so that the activity is increased, the hydration rate is accelerated, and the strength is increased. The particle size of the limestone powder after the mechanical force chemical treatment is further reduced, the activity is increased, the filling effect is enhanced, and the secondary reaction is promoted, so that the strength and the compactness of the mortar are improved.

[0029] (4) The redispersible latex powder is used as the additive and the UWB-2 anti-dispersing agent, so that the underwater repair material has good anti-dispersing effect and the loss of fluidity is reduced. The polymer film of the redispersible latex powder can effectively seal the pores and micro-cracks in the repair material, reduce the penetration of water and harmful substances, and improve the water resistance and the corrosion resistance of the repair material. DETAILED DESCRIPTION

[0030] A binary composite cement-based underwater repair mortar is prepared from the following raw materials in parts by weight: 360 parts of Portland cement, 90 parts of sulphoaluminate cement, 50 parts of limestone powder, 500 parts of medium sand, 0-15 parts of UWB-2 underwater non-dispersible concrete flocculant, 0-10 parts of redispersible latex powder, 2.5 parts of polycarboxylic acid high-performance powdered water reducing agent, and 200 parts of water.

[0031] The preparation method of the binary composite cement-based underwater repair mortar comprises the following steps:

[0032] (1) The Portland cement, the sulphoaluminate cement and the limestone powder are mixed and dried in proportion, and then poured into a ball mill tank containing steel balls, the mass ratio of the steel balls to the total mass of the materials is 7.5:1, and the ball milling is carried out at a speed of 75 r / min for 30 min to realize the mechanical force chemical effect, then all the powders are sieved out by a screen, and the modified cementitious material is obtained by sealing the bag for storage;

[0033] (2) The modified cementing material obtained in step (1) is mixed with medium sand, UWB-2 underwater non-dispersible concrete flocculating agent, redispersible latex powder, polycarboxylic acid high-performance powdery water reducing agent in a mixer at a low speed of 140 r / min for 30 s until the dry materials are uniformly mixed, then water is added and the stirring is continued at a low speed of 30 s, followed by high-speed stirring at 285 r / min for 30 s, pausing for 90 s (during the pause, the materials on the wall and bottom of the stirring pot that are not fully stirred are scraped out and placed back on the stirring machine after being uniformly stirred), and then high-speed stirring for 60 s to obtain a uniform repair mortar.

[0034] In order to make the content of the application more convenient to understand, the technical solutions of the application are further described below in combination with specific embodiments, but the application is not limited thereto.

[0035] The type of the silicate cement used is P.O 42.5, and the type of the sulphoaluminate cement used is CSA 42.5, both of which have a density of 3150 kg / m³, and the quality indexes of both meet the requirements of “General-purpose Silicate Cement (GB 175-2007)” and “General-purpose Sulphoaluminate Cement (GB 20472-2006)” respectively.

[0036] The limestone powder used has a CaCO3 content of 98wt%, a fineness (75 μm sieve residue) of less than 5.0%, and a quality index that meets the requirements of “Technical Specification for Limestone Powder Mixed with Hydraulic Concrete (DLT5304-2013)”.

[0037] The medium sand used is river sand for construction, which has a particle size in the range of 0.5-1.0 mm, a fineness modulus of about 2.5, and a good grading.

[0038] The UWB-2 underwater non-dispersible concrete flocculating agent used is produced by the China Petroleum Engineering Technology Research Institute.

[0039] The redispersible latex powder used is produced by the German Wacker Company.

[0040] The polycarboxylic acid high-performance powdery water reducing agent used has a water-reducing rate of 25-45%.

[0041] Example 1:

[0042] A binary composite cement-based underwater repair mortar is composed of the following raw materials in parts by weight: P.O 42.5 cement 360 parts, SAC 42.5 cement 90 parts, limestone powder 50 parts, medium sand 500 parts, UWB-2 underwater non-dispersible concrete flocculating agent 10 parts, redispersible latex powder 0 parts, polycarboxylic acid high-performance water reducing agent powder 2.5 parts, and water 200 parts.

[0043] The preparation process is as follows:

[0044] (1) The silicate cement, sulphoaluminate cement and limestone powder are mixed and dried according to the proportion, then poured into a ball mill tank with steel balls, the total mass of the steel balls to the total mass of the material is 7.5:1, ball milling at 75r / min for 30min to realize the mechanical chemical effect, after ball milling, all the powder is sieved out with a screen and stored in a sealed bag, thus the modified cementitious material is obtained;

[0045] (2) Before formal mixing, a small amount of the modified cementitious material prepared in step (1), medium sand and water are added in the mixer according to the designed mixing ratio to rinse the mixer, then the excess mortar is poured out, so that the cement mortar adheres to the wall of the mixer, avoiding affecting the mixing ratio of the mixture during formal mixing.

[0046] (3) The modified cementitious material, medium sand, UWB-2 underwater non-dispersible concrete flocculating agent, redispersible latex powder and polycarboxylic acid high-performance powder water reducing agent are added according to the designed mixing ratio, the mixer is started to dry mix at 140r / min for 30s, then water is added into the uniformly mixed material, the mixer is continuously stirred at 140r / min for 30s, then high-speed stirring is carried out at 285r / min for 30s, the mortar on the wall and bottom of the mixing pot which is not fully stirred is scraped out, the mortar is placed in the mixer again after being uniformly stirred, the mixer is started again, high-speed stirring is carried out at 285r / min for 60s, thus the uniform repair mortar is obtained.

[0047] Example 2:

[0048] A binary composite cement-based underwater repair mortar is composed of the following raw materials in parts by weight: P.O 42.5 cement 360 parts, SAC 42.5 cement 90 parts, limestone powder 50 parts, medium sand 500 parts, UWB-2 underwater non-dispersible concrete flocculating agent 10 parts, redispersible latex powder 5 parts, polycarboxylic acid high-performance water reducing agent powder 2.5 parts, and water 200 parts.

[0049] The preparation process is as follows:

[0050] (1) The silicate cement, sulphoaluminate cement and limestone powder are mixed and dried according to the proportion, then poured into a ball mill tank with steel balls, the total mass of the steel balls to the total mass of the material is 7.5:1, ball milling at 75r / min for 30min to realize the mechanical chemical effect, after ball milling, all the powder is sieved out with a screen and stored in a sealed bag, thus the modified cementitious material is obtained;

[0051] (2) Before formal mixing, a small amount of the modified cementitious material prepared in step (1), medium sand and water are added in the mixer according to the designed mixing ratio to rinse the mixer, then the excess mortar is poured out, so that the cement mortar adheres to the wall of the mixer, avoiding affecting the mixing ratio of the mixture during formal mixing.

[0052] (3) According to the design mixing ratio, add the modified cementitious material, medium sand, UWB-2 underwater non-dispersible concrete flocculating agent, redispersible latex powder and polycarboxylate high-performance powder water reducing agent with the complete weight, start the mixer, dry mix at 140 r / min for 30 s, then add water into the well-mixed material, continue to mix at 140 r / min for 30 s, then mix at 285 r / min for 30 s, pause for 90 s, scrape out the mortar on the wall and bottom of the mixing pot which is not fully mixed, put it back into the mixer after well mixed, start the mixer again, mix at 285 r / min for 60 s, and obtain the uniform repair mortar.

[0053] Example 3:

[0054] A binary composite cement-based underwater repair mortar is composed of the following raw materials in weight parts: P.O 42.5 cement 360 parts, SAC 42.5 cement 90 parts, limestone powder 50 parts, medium sand 500 parts, UWB-2 underwater non-dispersible concrete flocculating agent 10 parts, redispersible latex powder 10 parts, polycarboxylate high-performance water reducing agent powder 2.5 parts, and water 200 parts.

[0055] The preparation process is as follows:

[0056] (1) Mix the portland cement, sulphoaluminate cement and limestone powder according to the proportion, dry them, then pour them into a ball mill tank containing steel balls, the ratio of the total mass of steel balls to the total mass of materials is 7.5:1, ball mill at 75 r / min for 30 min to realize the mechanical chemical effect, then sieve all the powders with a screen and store them in a sealed bag, and the modified cementitious material is obtained;

[0057] (2) Before formal mixing, add a small amount of the modified cementitious material prepared in step (1), medium sand and water into the mixer according to the design mixing ratio to rinse the pot, then pour out the excess mortar, so that the cement mortar adheres to the wall of the mixer, avoiding affecting the mixing ratio during formal mixing.

[0058] (3) According to the design mixing ratio, add the modified cementitious material, medium sand, UWB-2 underwater non-dispersible concrete flocculating agent, redispersible latex powder and polycarboxylate high-performance powder water reducing agent with the complete weight, start the mixer, dry mix at 140 r / min for 30 s, then add water into the well-mixed material, continue to mix at 140 r / min for 30 s, then mix at 285 r / min for 30 s, pause for 90 s, scrape out the mortar on the wall and bottom of the mixing pot which is not fully mixed, put it back into the mixer after well mixed, start the mixer again, mix at 285 r / min for 60 s, and obtain the uniform repair mortar.

[0059] Example 4

[0060] A binary composite cement-based underwater repair mortar is composed of the following raw materials in parts by weight: P.O 42.5 cement 360 parts, SAC 42.5 cement 90 parts, limestone powder 50 parts, medium sand 500 parts, UWB-2 underwater non-dispersible concrete flocculating agent 0 parts, redispersible latex powder 10 parts, polycarboxylate high-performance water-reducing agent powder 2.5 parts, and water 200 parts.

[0061] The preparation process is as follows:

[0062] (1) Mix silicate cement, sulfoaluminate cement, and limestone powder in proportion, dry them, and then pour them into a ball mill tank containing steel balls. The ratio of the total mass of steel balls to the total mass of materials is 7.5:1. Ball mill at a speed of 75 r / min for 30 min to achieve mechanical chemical effect. After ball milling, screen all the powders with a screen and store them in a sealed bag. The modified cementitious material is obtained.

[0063] (2) Before formal mixing, add a small amount of modified cementitious material prepared in step (1), medium sand, and water to the mixer according to the designed mixing ratio to rinse the pot, then pour out the excess mortar, and make the cement mortar adhere to the pot wall of the mixer to avoid affecting the mixing ratio during formal mixing.

[0064] (3) Add the complete weight of modified cementitious material, medium sand, UWB-2 underwater non-dispersible concrete flocculating agent, redispersible latex powder, and polycarboxylate high-performance powdered water-reducing agent according to the designed mixing ratio. Start the mixer and dry mix at a low speed of 140 r / min for 30 s. Then add water to the uniformly mixed material and continue to mix at a low speed of 140 r / min for another 30 s. After that, mix at a high speed of 285 r / min for 30 s, pause for 90 s, scrape out the mortar on the pot wall and bottom that has not been fully mixed, place it back into the mixer, start the mixer again, and mix at a high speed of 285 r / min for 60 s to obtain uniform repair mortar.

[0065] Example 5

[0066] A binary composite cement-based underwater repair mortar is composed of the following raw materials in parts by weight: P.O 42.5 cement 360 parts, SAC 42.5 cement 90 parts, limestone powder 50 parts, medium sand 500 parts, UWB-2 underwater non-dispersible concrete flocculating agent 5 parts, redispersible latex powder 10 parts, polycarboxylate high-performance water-reducing agent powder 2.5 parts, and water 200 parts.

[0067] The preparation process is as follows:

[0068] (1) The silicate cement, sulphoaluminate cement and limestone powder are mixed and dried according to the proportion, then poured into a ball mill tank with steel balls, the total mass of the steel balls to the total mass of the material is 7.5:1, ball milling at 75r / min for 30min to realize the mechanical chemical effect, after ball milling, all the powder is sieved out with a screen and stored in a sealed bag, thus the modified cementitious material is obtained;

[0069] (2) Before formal mixing, a small amount of the modified cementitious material prepared in step (1), medium sand and water are added in the mixer according to the designed mixing ratio to rinse the mixer, then the excess mortar is poured out, so that the cement mortar adheres to the wall of the mixer, avoiding affecting the mixing ratio of the mixture during formal mixing.

[0070] (3) The modified cementitious material, medium sand, UWB-2 underwater non-dispersible concrete flocculant, redispersible latex powder and polycarboxylic acid high-performance powder water reducer are added according to the designed mixing ratio, the mixer is started to dry mix at 140r / min for 30s, then water is added into the uniformly mixed material, the mixer is continued to mix at 140r / min for 30s, then high-speed mixing is carried out at 285r / min for 30s, the mortar on the wall and bottom of the mixing pot which is not fully mixed is scraped out, the mortar is placed in the mixer again after uniform mixing, the mixer is started again, high-speed mixing is carried out at 285r / min for 60s, thus the uniform repair mortar is obtained.

[0071] Example 6:

[0072] A binary composite cement-based underwater repair mortar is composed of the following raw materials in parts by weight: P.O 42.5 cement 360 parts, SAC 42.5 cement 90 parts, limestone powder 50 parts, medium sand 500 parts, UWB-2 underwater non-dispersible concrete flocculant 15 parts, redispersible latex powder 10 parts, polycarboxylic acid high-performance water reducer powder 2.5 parts, and water 200 parts.

[0073] The preparation process is as follows:

[0074] (1) The silicate cement, sulphoaluminate cement and limestone powder are mixed and dried according to the proportion, then poured into a ball mill tank with steel balls, the total mass of the steel balls to the total mass of the material is 7.5:1, ball milling at 75r / min for 30min to realize the mechanical chemical effect, after ball milling, all the powder is sieved out with a screen and stored in a sealed bag, thus the modified cementitious material is obtained;

[0075] (2) Before formal mixing, a small amount of the modified cementitious material prepared in step (1), medium sand and water are added in the mixer according to the designed mixing ratio to rinse the mixer, then the excess mortar is poured out, so that the cement mortar adheres to the wall of the mixer, avoiding affecting the mixing ratio of the mixture during formal mixing.

[0076] (3) According to the design mixing ratio, add the complete weight of the modified cementitious material, medium sand, UWB-2 underwater non-dispersible concrete flocculating agent, redispersible latex powder, and polycarboxylate high-performance powdery water reducing agent, start the mixer, dry mix at 140 r / min for 30 s, then add water to the uniformly mixed material, continue to mix at 140 r / min for 30 s, then mix at 285 r / min for 30 s, pause for 90 s, scrape out the mortar on the wall and bottom of the mixing pot that is not fully mixed, place it back on the mixer after uniform mixing, start the mixer again, mix at 285 r / min for 60 s at high speed, and obtain uniform repair mortar.

[0077] Comparative Example 1

[0078] A binary composite cement-based underwater repair mortar is composed of the following raw materials in parts by weight: P.O 42.5 cement 360 parts, SAC 42.5 cement 90 parts, limestone powder 50 parts, medium sand 500 parts, UWB-2 underwater non-dispersible concrete flocculating agent 5 parts, redispersible latex powder 10 parts, and polycarboxylate high-performance water reducing agent powder 2.5 parts, water 200 parts.

[0079] The preparation process is as follows:

[0080] (1) Before formal mixing, add a small amount of cement, limestone powder, medium sand, and water to the mixer according to the design mixing ratio, first rinse the pot, then pour out the excess mortar, so that the cement mortar adheres to the wall of the mixer, avoiding affecting the mixing ratio during formal mixing.

[0081] (2) According to the design mixing ratio, add the complete weight of the modified cementitious material, medium sand, UWB-2 underwater non-dispersible concrete flocculating agent, redispersible latex powder, and polycarboxylate high-performance powdery water reducing agent, start the mixer, dry mix at 140 r / min for 30 s, then add water to the uniformly mixed material, continue to mix at 140 r / min for 30 s, then mix at 285 r / min for 30 s, pause for 90 s, scrape out the mortar on the wall and bottom of the mixing pot that is not fully mixed, place it back on the mixer after uniform mixing, start the mixer again, mix at 285 r / min for 60 s at high speed, and obtain uniform repair mortar.

[0082] Comparative Example 2

[0083] A binary composite cement-based underwater repair mortar is composed of the following raw materials in parts by weight: P.O 42.5 cement 360 parts, SAC 42.5 cement 90 parts, limestone powder 50 parts, medium sand 500 parts, UWB-2 underwater non-dispersible concrete flocculating agent 5 parts, redispersible latex powder 10 parts, and polycarboxylate high-performance water reducing agent powder 2.5 parts, water 200 parts.

[0084] The preparation process is as follows:

[0085] (1) Before formal stirring, a small amount of cement, limestone powder, medium sand and water is added in the mixer according to the designed mixing ratio, and the cavity is first rinsed, then the excess mortar is poured out, so that the cement mortar adheres to the pot wall of the mixer, avoiding affecting the mixing ratio of the mixture during formal stirring.

[0086] (2) According to the designed mixing ratio, add the complete weight of cement, limestone powder, medium sand, polyacrylamide anti-dispersant, redispersible latex powder, and polycarboxylic acid high-performance powdered water reducing agent, start the mixer, dry mix at 140 r / min for 30 s, then add water to the uniformly mixed materials, continue to stir at 140 r / min for 30 s, then stir at 285 r / min for 30 s, pause for 90 s, scrape out the mortar on the pot wall and bottom that is not fully stirred, place it back in the mixer after uniform stirring, start the mixer again, and stir at 285 r / min for 60 s, to obtain uniform repair mortar.

[0087] Comparative Example 3:

[0088] A binary composite cement-based underwater repair mortar is composed of the following raw materials in parts by weight: P.O 42.5 cement 360 parts, SAC 42.5 cement 90 parts, limestone powder 50 parts, medium sand 500 parts, polyvinyl alcohol anti-dispersant 1 part, redispersible latex powder 10 parts, polycarboxylic acid high-performance water reducing agent powder 2.5 parts, and water 200 parts.

[0089] The preparation process is as follows:

[0090] (1) Before formal stirring, a small amount of cement, limestone powder, medium sand and water is added in the mixer according to the designed mixing ratio, and the cavity is first rinsed, then the excess mortar is poured out, so that the cement mortar adheres to the pot wall of the mixer, avoiding affecting the mixing ratio of the mixture during formal stirring.

[0091] (2) According to the designed mixing ratio, add the complete weight of cement, limestone powder, medium sand, polyacrylamide anti-dispersant, redispersible latex powder, and polycarboxylic acid high-performance powdered water reducing agent, start the mixer, dry mix at 140 r / min for 30 s, then add water to the uniformly mixed materials, continue to stir at 140 r / min for 30 s, then stir at 285 r / min for 30 s, pause for 90 s, scrape out the mortar on the pot wall and bottom that is not fully stirred, place it back in the mixer after uniform stirring, start the mixer again, and stir at 285 r / min for 60 s, to obtain uniform repair mortar.

[0092] A small amount of freshly mixed repair mortar prepared in each example and comparative example is cast into underwater and overwater test blocks for performance testing, including setting time, anti-dispersion and flow performance. The preparation process of the underwater test block is as follows: first, a water tank with a size of 600mmx400mmx450mm is selected, and the freshly mixed mortar is directly cast into the test mold with a water depth of 300mm (water temperature is maintained at 20±1℃). After 1h of casting, the test mold is taken out, the surface of the underwater test block is smoothed, and then it is put back into the water, and after 24h, the mold is removed. After the mold is removed, the underwater test block is placed in a standard curing box for curing. The overwater test block is directly cast into the test mold, and after 24h, the mold is removed, and the test piece is placed in a standard curing room for curing. Then, the overwater and underwater mortar test blocks of the corresponding curing age are taken for mechanical property comparison test, so as to evaluate whether they meet the requirements of the repair material of hydraulic structure, and the results are shown in Table 1.

[0093] Table 1: Component allocation ratio and performance index in each example and comparative example

[0094]

[0095] As shown in Table 1, in Examples 1-6, when the dosage of UWB-2 underwater non-dispersive concrete flocculant remains unchanged, the fluidity of the repair mortar gradually decreases with the increase of the dosage of redispersible latex powder, but the compressive strength gradually increases; when the dosage of redispersible latex powder remains unchanged, the fluidity of the repair mortar gradually decreases with the increase of the dosage of UWB-2 underwater non-dispersive concrete flocculant, and the compressive strength first increases and then decreases. Among them, the underwater compressive strength of the sample prepared in Example 5 reaches the best at 3d, 7d and 14d hydration age, the fluidity is 265mm, which meets the self-leveling requirement (230mm) in actual construction.

[0096] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be included in the scope of the present application.

Claims

1. A binary composite cementitious underwater repair mortar, characterized in that, It is composed of the following raw materials by weight: Portland cement 360 parts, sulphoaluminate cement 90 parts, limestone powder 50 parts, medium sand 500 parts, UWB-2 underwater non-dispersible concrete flocculating agent 5-15 parts, redispersible latex powder 5-10 parts, polycarboxylic acid high-performance powdery water reducing agent 2.5 parts, and water 200 parts; It comprises the following steps: (1) Preparation of mechanically-chemically modified cementitious material: mix and dry Portland cement, sulphoaluminate cement and limestone powder in proportion, then ball mill to obtain modified cementitious material; (2) Mix the modified cementitious material obtained in step (1) with medium sand, UWB-2 underwater non-dispersible concrete flocculating agent, redispersible latex powder, polycarboxylic acid high-performance powdery water reducing agent in a mixer at low speed for 30 s until the dry materials are uniformly mixed, then add water, continue to stir at low speed for 30 s, then stir at high speed for 30 s, pause for 90 s, then stir at high speed for 60 s to obtain uniform repair mortar.

2. The two-component cementitious underwater repair mortar according to claim 1, characterized in that The Portland cement has a type of P.O 42.5-52.5 and a density of 3100-3250 kg / m³.

3. The two-component, cementitious, underwater repair mortar according to claim 1, characterized in that The sulphoaluminate cement has a type of CSA 42.5-52.5 and a density of 3100-3250 kg / m³.

4. The two-component, cementitious, underwater repair mortar according to claim 1, characterized in that, The limestone powder contains 86wt%-99wt% CaCO3 and has a 75 μm sieve residue fineness of less than 5.0%.

5. The two-part composite cementitious underwater repair mortar of claim 1, wherein, The medium sand is river sand for construction, with a particle size in the range of 0.5-1.0 mm and a fineness modulus of 2.

5.

6. The two-part composite cementitious underwater repair mortar of claim 1, wherein, The polycarboxylic acid high-performance powdery water reducing agent has a water-reducing rate of 25-45%.

7. The two-part composite cementitious underwater repair mortar of claim 1, wherein, In step (1), the total mass ratio of steel balls to materials used in ball milling is 7.5:1; the ball milling time is 30 min and the rotation speed is 75 r / min.

8. The two-part composite cementitious underwater repair mortar of claim 1, wherein, In step (2), the rotation speed used at low speed is 140 r / min and the rotation speed used at high speed is 285 r / min.

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