Dry powder heat-resistant interface treating agent for new and old concrete and application of dry powder heat-resistant interface treating agent

Abstract

The invention belongs to the technical field of concrete admixtures, and particularly relates to a new and old concrete dry powder heat-resistant interface treating agent and application. The interface treating agent is prepared from the following raw materials in parts by weight: 100 parts of cement, 100 to 125 parts of quartz sand, 20 to 30 parts of mineral admixture, 5 to 8 parts of organic-inorganic hybrid phase change microcapsules, 1.5 to 3 parts of carboxymethyl chitosan powder, 0.1 to 0.2 part of early strength agent and 0.05 to 0.1 part of water reducing agent, the preparation method of the organic-inorganic hybrid phase change microcapsule comprises the following steps: preparing a precursor solution from alkyl orthosilicate, an ether-containing silane coupling agent, alcohol, water and ammonia water; preparing an emulsion from paraffin, a surfactant and water; under the conditions of temperature control and stirring, the precursor solution is dropped into the emulsion for reaction, and the organic-inorganic hybrid phase change microcapsule is obtained. The organic-inorganic hybrid phase change microcapsule can adjust the temperature, delay the sudden rise of the temperature at the interface, reduce the peak temperature, reduce the temperature difference, buffer the thermal expansion and cold contraction, and reduce the cracking caused by thermal stress.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete admixtures, and particularly relates to a dry powder type heat-resistant interface treatment agent for new and old concrete and an application thereof. Background Art

[0002] The interfacial bonding between new and old concrete is often involved in structural maintenance, renovation, reinforcement, and some new concrete projects. Examples include bridge reinforcement and renovation, floor additions, water conservancy project repairs, and the connection of precast concrete components. The quality of the interfacial bonding directly impacts project quality. Often, cracks develop at the interface between new and old concrete after a period of service, and newly patched concrete can warp and peel, compromising the overall structural functionality and safety.

[0003] In order to make the new and old concrete truly work together as a whole, choosing the right concrete interface treatment agent is the key. Concrete interface treatment agent (interface treatment agent for short) is a material applied to the concrete interface in order to promote the bonding of the concrete interface. Interface treatment agents are divided into two categories according to their composition: dry powder interface agents and liquid interface agents. Dry powder interface agents are suitable for the interface treatment of cement concrete. Dry powder interface agents are dry powder products composed of inorganic gelling materials such as cement, fillers and related admixtures. When used, they should be mixed with water or other liquids in proportion. Compared with liquid or paste products, dry powders are small in size and light in weight, making them easier to package and transport. In addition, they are not prone to deterioration, precipitation and other problems during storage, and have a longer shelf life. For example, patent CN1168795C discloses an inorganic concrete interface binder, primarily composed of a mixture of active powdered materials, cement, and surfactants. The active powdered materials are a combination of one or more active materials: slag, zeolite powder, fly ash, silica fume, and other active materials. The surfactants are a combination of one or more lignin, naphthalene, resin, molasses, chlorides, sulfates, and organic amines. The cement is high-strength grade. Patent CN1609039B discloses a nanopowder-modified concrete repair interface agent, which is a mixture of 78-94% fly ash, 0-20% silica fume, 1-8% nanopowder, and 0-3% water reducer, with the total weight percentage of each component being 100% in the form of a powder or a paste prepared by adding water. Nano-powder is composed of one or more of nano-SiO2, nano-CaCO3, and nano-Al2O3. When used, the interface agent and cement are mixed in a mass ratio of 1:1 to 3, and water is added to make a pure paste or water and sand are added to make a mortar. This pure paste or mortar is applied to the old concrete surface that needs to be repaired, and then new concrete can be poured or sprayed.

[0004] The above are common dry-powder concrete interface treatment agents. While they can effectively address the problem of insufficient adhesion between new and old concrete interfaces and reduce the risk of warping and spalling, due to the different expansion coefficients of different materials, thermal stress can easily be generated at the interface between new and old concrete and the treatment agent at high temperatures due to the difference in thermal expansion properties. This stress concentration can weaken the interfacial bonding and seriously affect the stability and durability of the concrete structure.

[0005] Therefore, in response to engineering needs in high-temperature environments, it is necessary to develop a dry powder concrete interface treatment agent with good heat resistance. This will greatly expand the application scenarios of such treatment agents and improve their applicability and reliability under high-temperature working conditions. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a dry powder type heat-resistant interface treatment agent for new and old concrete and a preparation method thereof. The dry powder type heat-resistant interface treatment agent includes organic-inorganic hybrid phase change microcapsules that can absorb or release heat, which can adjust the temperature, delay the sudden temperature rise at the interface, reduce the peak temperature, narrow the temperature difference, buffer thermal expansion and contraction, and reduce cracking caused by thermal stress; by adjusting the relative proportions of the shell material raw materials of the organic-inorganic hybrid phase change microcapsules, namely, ethyl orthosilicate and ether-containing silane coupling agent, the organic-inorganic hybrid phase change microcapsules have good redispersibility in water and can form a uniform system with other raw materials in concrete, which is beneficial to delaying the heating rate of the system, making the temperature changes in different parts tend to be synchronized, reducing the temperature difference between the interface treatment agent and different parts of the new and old concrete, avoiding thermal stress caused by uneven thermal expansion, and thus improving heat resistance.

[0007] In order to achieve the above objectives, the following technical solutions are adopted:

[0008] A dry powder heat-resistant interface treatment agent for new and old concrete comprises the following raw materials in parts by weight: 100 parts of cement, 100-125 parts of quartz sand, 20-30 parts of mineral admixture, 5-8 parts of organic-inorganic hybrid phase change microcapsules, 1.5-3 parts of carboxymethyl chitosan powder, 0.1-0.2 parts of an early strength agent, and 0.05-0.1 parts of a water reducer. The organic-inorganic hybrid phase change microcapsules are prepared by a method comprising the following steps: 1) preparing a precursor solution using an alkyl orthosilicate, an ether-containing silane coupling agent, alcohol, water, and aqueous ammonia; 2) preparing an emulsion using paraffin, a surfactant, and water; and 3) dripping the precursor solution into the emulsion under temperature control and stirring conditions to react and obtain the organic-inorganic hybrid phase change microcapsules. The amounts of the precursor solution in step 1) and the emulsion in step 2) satisfy a mass ratio of alkyl orthosilicate to paraffin of 0.6-0.8:0.5-0.8.

[0009] In step 1), the mass ratio of the alkyl orthosilicate, the ether-containing silane coupling agent, the alcohol, the water and the ammonia solution is 0.6-0.8:0.2-0.4:20-40:10-20:1. The alkyl orthosilicate is selected from one or a combination of two or more of methyl orthosilicate, ethyl orthosilicate and propyl orthosilicate. The ether-containing silane coupling agent is selected from one or a combination of two or more of (methoxytriethylene glycol ether propyl) trimethoxysilane, trimethyl [3- (2-methoxy) propyl] silane and polyethylene glycol trimethoxysilyl propyl ether, preferably (methoxytriethylene glycol ether propyl) trimethoxysilane. The alcohol is selected from one or a combination of two or more of methanol, ethanol, propanol and isopropanol. The concentration of the ammonia solution is 25-28wt%.

[0010] In step 2), the mass ratio of the paraffin wax, the surfactant, and the water is 0.5-0.8:0.2-0.3:50. The surfactant is selected from one or a combination of two or more of lauryl betaine, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, Tween 20, and OP-10, preferably hexadecyltrimethylammonium bromide. The paraffin wax is selected from one or a combination of two or more of 18# paraffin wax, 20# paraffin wax, 25# paraffin wax, 30# paraffin wax, 45# paraffin wax, and 58# paraffin wax. The emulsion is emulsified at 60-80°C and a stirring speed of 1000-1500rpm.

[0011] In step 3), the temperature is controlled at 60-80°C. The stirring speed is 500-1000 rpm. The reaction time is 3-5 hours. After the reaction, centrifugation, washing, and drying steps are also included. The washing is performed by alternating washing with water and alcohol 1-3 times. The drying temperature is 60-100°C and the drying time is 12-36 hours. The precursor solution is dripped over 30-60 minutes.

[0012] The carboxylation degree of the carboxymethyl chitosan powder is 80-90%, the pH value is 6-8, and the viscosity is 10-80 mPa.s, preferably 40-60 mPa.s.

[0013] The organic-inorganic hybrid phase-change microcapsules are made from a silica shell with organic ether chains retained on the surface, produced by hydrolyzing and condensing alkyl orthosilicates and ether-containing silane coupling agents and drying at 60-100°C at ambient pressure. The core material is a phase-change material, paraffin wax. Due to the presence of the organic ether chains, these microcapsules are highly redispersible in water and form a uniform system with other concrete ingredients. At high temperatures, the organic-inorganic hybrid phase-change microcapsules undergo a solid-liquid phase transition, absorbing latent heat and slowing the heating rate of the system, synchronizing temperature changes across different areas. This minimizes temperature differences between the interface treatment agent and new and old concrete, avoiding thermal stresses caused by uneven thermal expansion and improving heat resistance. Furthermore, the organic-inorganic hybrid phase-change microcapsules and carboxymethyl chitosan powder reduce porosity and refine pore size distribution, reducing the driving force for capillary water penetration and strengthening the cement paste structure. This also improves the bond strength of the interface treatment agent after immersion in water.

[0014] The cement is ordinary Portland cement with a strength grade of 42.5 or 52.5.

[0015] The mineral admixture is selected from fly ash, mineral powder or a combination of the two.

[0016] The fly ash is selected from one of primary fly ash and secondary fly ash, or a combination of the two.

[0017] The mineral powder is selected from one of S105 mineral powder, S95 mineral powder, and S75 mineral powder, or a combination of two or more thereof.

[0018] The early strength agent is selected from one or a combination of two or more of sodium sulfate, calcium formate, calcium chloride and calcium nitrate.

[0019] The water reducing agent is a polycarboxylic acid powder water reducing agent with a water reducing rate of 20-25%.

[0020] The quartz sand fineness modulus is 2.3-3.0.

[0021] The present invention also provides an application of the above-mentioned dry powder type heat-resistant interface treatment agent for new and old concrete, comprising the following steps:

[0022] S1) roughening the old concrete base to remove surface residues and drying it until there is no obvious water on the surface;

[0023] S2) mixing cement, quartz sand, mineral admixtures, organic-inorganic hybrid phase change microcapsules, carboxymethyl chitosan powder, early strength agent, and water reducing agent, and adding water to mix to obtain a slurry;

[0024] S3) Apply the slurry on the surface of the old concrete base, pour new concrete and maintain.

[0025] The mass of the water is 7.5-10 wt % of the dry powder concrete interface treating agent.

[0026] In step S3), the dry powder concrete interface treatment agent is applied to a thickness of 1-5 mm.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The interface treatment agent of the present invention includes organic-inorganic hybrid phase change microcapsules that can absorb or release heat, which can regulate temperature, delay sudden temperature rise at the interface, reduce peak temperature, narrow temperature difference, buffer thermal expansion and contraction, and reduce cracking caused by thermal stress.

[0029] 2. The present invention adjusts the relative proportions of the shell material raw materials of organic-inorganic hybrid phase change microcapsules, namely, ethyl orthosilicate and ether-containing silane coupling agent, so that the organic-inorganic hybrid phase change microcapsules have good redispersibility in water and can form a uniform system with other raw materials in concrete, which is beneficial to delaying the heating rate of the system, making the temperature changes in different parts tend to be synchronized, reducing the temperature difference between the interface treatment agent and different parts of the new and old concrete, avoiding thermal stress caused by uneven thermal expansion, and thus improving heat resistance.

[0030] 3. The organic-inorganic hybrid phase change microcapsules and carboxymethyl chitosan powder of the present invention also have the functions of reducing porosity and refining pore size distribution, reducing the driving force of capillary water penetration, strengthening the cement stone structure, and improving the bonding strength of the interface treatment agent after immersion in water. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with specific embodiment, but is not limited to the content on the specification sheets. Unless otherwise specified, "parts" described in the embodiments of the present invention are all parts by weight. All reagents used are commercially available reagents in this area.

[0032] Hydroxyethyl cellulose (product number ZZS-HEC-Mw-121K, weight-average molecular weight 121,700) was purchased from Shanghai Zhenzhun Biotechnology Co., Ltd.

[0033] Carboxymethyl chitosan powder, product number C832672, with a carboxylation degree of 80%, a pH value of 6.8, and a viscosity of 43 mPa·s, was purchased from Macklin.

[0034] Carboxymethyl chitosan powder, product number C914893, with a carboxylation degree of 90%, a pH value of 6.2, and a viscosity of 50 mPa·s, was purchased from Macklin.

[0035] Polycarboxylic acid powder water reducer TD-JSS2 with a water reduction rate of 25%, Century Tuoda (Chongqing) New Materials Technology Co., Ltd.

[0036] Quartz sand with a fineness modulus of 2.3 was purchased from Guizhou Zhongsha Building Materials Co., Ltd.

[0037] Example 1

[0038] 1) 0.6 kg of ethyl orthosilicate, 0.4 kg of (methoxytriethylene glycol ether propyl) trimethoxysilane, 40 kg of ethanol, 20 kg of water, and 1 kg of 28 wt% ammonia water were mixed and stirred at 500 rpm for 30 minutes to prepare a precursor solution;

[0039] 2) Add 0.5 kg 58# paraffin wax, 0.2 kg hexadecyltrimethylammonium bromide, and 50 kg water to a heating kettle, raise the temperature to 80°C, and stir at 1500 rpm for 1 hour to emulsify into a uniform emulsion;

[0040] 3) Under the conditions of temperature control at 80° C. and stirring at 1000 rpm, the precursor solution of step 1) was added dropwise to the emulsion of step 2) for 60 min, and the mixture was reacted for 5 h. The mixture was centrifuged, washed alternately with water and ethanol for 3 times, and dried at 100° C. for 24 h to obtain organic-inorganic hybrid phase change microcapsules.

[0041] 4) First, roughen the old concrete base, rinse with water to remove surface residue, and dry until there is no obvious water on the surface;

[0042] 5) 100 parts by mass of 42.5 ordinary Portland cement, 125 parts by mass of quartz sand, 30 parts by mass of primary fly ash, 8 parts by mass of organic-inorganic hybrid phase change microcapsules, 3 parts by mass of carboxymethyl chitosan powder C914893, 0.2 parts by mass of calcium formate, and 0.1 parts by mass of polycarboxylic acid powder water reducer TD-JSS2 were mixed to obtain a mixture, and 7.5 wt% of water was added to the mixture and mixed again to obtain a slurry;

[0043] 6) Apply the slurry on the surface of the old concrete base with a coating thickness of 3mm, pour new concrete and maintain.

[0044] New concrete: Mix 420 parts by mass of 42.5 grade ordinary Portland cement, 600 parts by mass of sand with fineness modulus 3.2, 1000 parts by mass of 5-20mm continuously graded gravel, 10 parts by mass of polycarboxylate water reducer TD-JSS2, 80 parts by mass of first-grade fly ash and 140 parts by mass of water, and cure at a temperature of 20°C and a relative humidity of 95% for 28 days.

[0045] Old concrete: Mix 420 parts by mass of 42.5 grade ordinary Portland cement, 600 parts by mass of sand with fineness modulus 3.2, 1000 parts by mass of 5-20mm continuously graded crushed stone, 10 parts by mass of polycarboxylate water reducer TD-JSS2, 80 parts by mass of first-class fly ash, and 140 parts by mass of water, and cure at a temperature of 20°C and a relative humidity of 95% for 28 days. Then, place it in a constant temperature and humidity aging box at a temperature of 85°C and a relative humidity of 85% for 1000 hours and take it out.

[0046] Example 2

[0047] The rest is the same as Example 1, except that in step 1), the amount of (methoxytriethylene glycol ether propyl)trimethoxysilane used is 0.2 kg.

[0048] Example 3

[0049] The rest is the same as Example 1, except that in step 1), an equal mass of trimethyl[3-(2-methoxy)propyl]silane is used instead of (methoxytriethylene glycol ether propyl)trimethoxysilane.

[0050] Example 4

[0051] The rest is the same as Example 1, except that in step 1), the amount of ethyl orthosilicate used is 0.8 kg.

[0052] Example 5

[0053] The rest is the same as Example 1, except that in step 2), the amount of (methoxytriethylene glycol ether propyl)trimethoxysilane used is 0.2 kg.

[0054] Example 6

[0055] The rest is the same as Example 1, except that in step 5), the amount of organic-inorganic hybrid phase change microcapsules is 5 parts by mass.

[0056] Example 7

[0057] The rest is the same as Example 1, except that in step 5), the carboxymethyl chitosan powder C914893 is replaced by the carboxymethyl chitosan powder C832672 of equal mass.

[0058] Example 8

[0059] The rest is the same as Example 1, except that in step 5), the amount of carboxymethyl chitosan powder C914893 used is 1.5 parts by mass.

[0060] Example 9

[0061] The rest is the same as Example 1, except that in step 1), ethyl orthosilicate is replaced by methyl orthosilicate of equal mass.

[0062] Example 10

[0063] 1) 0.6 kg of ethyl orthosilicate, 0.4 kg of (methoxytriethylene glycol ether propyl) trimethoxysilane, 40 kg of ethanol, 20 kg of water, and 1 kg of 28 wt% ammonia water were mixed and stirred at 500 rpm for 30 minutes to prepare a precursor solution;

[0064] 2) Add 0.8 kg of 58# paraffin wax, 0.2 kg of hexadecyltrimethylammonium bromide, and 50 kg of water to a heating kettle, raise the temperature to 80°C, and stir at 1500 rpm for 1 hour to emulsify into a uniform emulsion;

[0065] 3) Under the conditions of temperature control at 80° C. and stirring at 1000 rpm, the precursor solution of step 1) was added dropwise to the emulsion of step 2) for 60 min, and the mixture was reacted for 5 h. The mixture was centrifuged, washed alternately with water and ethanol for 3 times, and dried at 100° C. for 24 h to obtain organic-inorganic hybrid phase change microcapsules.

[0066] 4) First, roughen the old concrete base, rinse with water to remove surface residue, and dry until there is no obvious water on the surface;

[0067] 5) 100 parts by mass of 42.5 ordinary Portland cement, 100 parts by mass of quartz sand, 50 parts by mass of primary fly ash, 5 parts by mass of organic-inorganic hybrid phase change microcapsules, 1.5 parts by mass of carboxymethyl chitosan powder C914893, 0.2 parts by mass of calcium formate, and 0.1 parts by mass of polycarboxylic acid powder water reducer TD-JSS2 were mixed to obtain a mixture, and 7.5 wt% of water was added to the mixture and mixed again to obtain a slurry;

[0068] 6) Apply the slurry on the surface of the old concrete base with a coating thickness of 5mm, pour new concrete and maintain.

[0069] New concrete: Mix 420 parts by mass of 42.5 grade ordinary Portland cement, 600 parts by mass of sand with fineness modulus 3.2, 1000 parts by mass of 5-20mm continuously graded gravel, 10 parts by mass of polycarboxylate water reducer TD-JSS2, 80 parts by mass of first-grade fly ash and 140 parts by mass of water, and cure at a temperature of 20°C and a relative humidity of 95% for 28 days.

[0070] Old concrete: Mix 420 parts by mass of 42.5 grade ordinary Portland cement, 600 parts by mass of sand with fineness modulus 3.2, 1000 parts by mass of 5-20mm continuously graded crushed stone, 10 parts by mass of polycarboxylate water reducer TD-JSS2, 80 parts by mass of first-class fly ash, and 140 parts by mass of water, and cure at a temperature of 20°C and a relative humidity of 95% for 28 days. Then, place it in a constant temperature and humidity aging box at a temperature of 85°C and a relative humidity of 85% for 1000 hours and take it out.

[0071] Comparative Example 1

[0072] The rest is the same as Example 1, except that, in step 1), an equal mass of propylaminotris(trimethylsiloxy)silane is used instead of (methoxytriethylene glycol ether propyl)trimethoxysilane.

[0073] Comparative Example 2

[0074] The rest is the same as Example 1, except that in step 5), the carboxymethyl chitosan powder C914893 is replaced by hydroxyethyl cellulose of equal mass.

[0075] Comparative Example 3

[0076] The rest is the same as Example 1, except that in step 5), the amount of carboxymethyl chitosan powder C914893 is 4 parts by mass.

[0077] Comparative Example 4

[0078] The rest is the same as Example 1, except that in step 5), the amount of carboxymethyl chitosan powder C914893 used is 1 part by mass.

[0079] The interface treatment agents prepared in the above examples and comparative examples were subjected to the following performance tests:

[0080] Tensile bond strength: The test was carried out in accordance with the standard JC / T907-2018 "Concrete Interface Treatment Agent". The tensile bond strength specimen was cured for 13 days under standard conditions. The pull-out joint was bonded to a 40mm*40mm*10mm mortar specimen using 3M DP420 two-component low-temperature curing and high-temperature resistant epoxy structural adhesive. The interface treatment agent was applied with a thickness of 3mm. The tensile bond strength test was carried out 2 hours later.

[0081] Heat-resistant treatment: The tensile bond strength specimen was cured under standard conditions for 7 days, then placed in an oven at (70±2)°C for 7 days, taken out and cooled under standard conditions for 4 hours, and the pull-out joint was bonded to a 40mm*40mm*10mm mortar specimen using 3M DP420 two-component low-temperature curing and high-temperature resistant epoxy structural adhesive. The tensile bond strength was re-measured after 24 hours, and the strength loss rate was calculated.

[0082] Water immersion treatment: The tensile bond strength specimen was cured under standard conditions for 7 days, and then completely immersed in water at (23±2)℃. After 6 days, the specimen was taken out of the water and the surface water stains were wiped off with a cloth. The pull-out joint was bonded to a 40mm*40mm*10mm mortar specimen with 3M DP420 two-component low-temperature curing and high-temperature resistant epoxy structural adhesive. After 7 hours, the specimen was immersed in water at (23±2)℃. After 24 hours, the specimen was taken out, the surface water stains were wiped off, the tensile bond strength was remeasured, and the strength loss rate was calculated.

[0083] Table 1 Performance test results

[0084] project Tensile bond strength MPa Strength loss rate after heat treatment % Strength loss rate after water immersion treatment % Example 1 1.59 1.3 3.5 Example 2 1.44 2.1 3.2 Example 3 1.50 1.9 3.9 Example 4 1.46 1.3 3.3 Example 5 1.46 1.6 3.4 Example 6 1.42 2.9 4.4 Example 7 1.53 2.3 4.0 Example 8 1.50 3.4 4.5 Example 9 1.59 1.2 3.2 Example 10 1.40 3.8 4.8 Comparative Example 1 1.21 5.7 4.7 Comparative Example 2 1.37 6.5 9.6 Comparative Example 3 1.53 5.0 3.4 Comparative Example 4 1.45 4.3 7.5

[0085] From the heat-resistant treatment test results of Example 1, Example 8, and Comparative Examples 2-4 in Table 1, it can be clearly seen that carboxymethyl chitosan has a significant synergistic effect on improving the heat resistance of organic-inorganic hybrid phase change microcapsules. It is speculated that the organic ether chains on the surface of the organic-inorganic hybrid phase change microcapsules have a large difference in polarity with the cement-based materials, and the interaction force is low. The interface with the hydration product of the cementitious material in the concrete is not tightly bonded, and a weak area is easily formed at the interface. Although the effect on the adhesion at room temperature is not obvious, the weak area is prone to develop microcracks after heat-resistant treatment, resulting in a loss of adhesion strength. The presence of carboxyl and hydroxyl groups in the carboxymethyl chitosan molecules can not only form hydrogen bonds with the organic-inorganic hybrid phase change microcapsules, but also form hydrogen bonds with Ca 2+ The formation of stable coordination bonds promotes the dense accumulation of hydration products in the interface transition zone surrounding the organic-inorganic hybrid phase change microcapsules, effectively filling the pores and strengthening the density of the interface transition zone. Carboxymethyl chitosan improves the interface structure around the microcapsules, creating a synergistic effect with the organic-inorganic hybrid phase change microcapsules, further enhancing heat resistance.

[0086] As can be seen from Table 1, the interface treatment agent prepared by the present invention has high bonding strength and good heat resistance, has good adhesion to concrete, can be used for a long time in a high temperature environment, and effectively avoids hollowing, peeling and falling off.

[0087] The above detailed description is a specific description of one feasible embodiment of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A dry powder heat-resistant interface treatment agent for new and old concrete, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of cement, 100-125 parts of quartz sand, 20-30 parts of mineral admixture, 5-8 parts of organic-inorganic hybrid phase change microcapsules, 1.5-3 parts of carboxymethyl chitosan powder, 0.1-0.2 parts of an early strength agent, and 0.05-0.1 parts of a water reducer. The organic-inorganic hybrid phase change microcapsules are prepared by a method comprising the following steps: 1) preparing a precursor solution using an alkyl orthosilicate, an ether-containing silane coupling agent, alcohol, water, and ammonia water; 2) preparing an emulsion using paraffin, a surfactant, and water; and 3) dripping the precursor solution into the emulsion under temperature control and stirring conditions to react and obtain the organic-inorganic hybrid phase change microcapsules. The amounts of the precursor solution in step 1) and the emulsion in step 2) satisfy a mass ratio of the alkyl orthosilicate to the paraffin of 0.6-0.8:0.5-0.

8.

2. The dry powder heat-resistant interface treatment agent for new and old concrete according to claim 1, characterized in that: In step 1), the mass ratio of the alkyl orthosilicate, the ether-containing silane coupling agent, the alcohol, the water, and the ammonia solution is 0.6-0.8:0.2-0.4:20-40:10-20:

1.

3. The dry powder heat-resistant interface treatment agent for new and old concrete according to claim 1, characterized in that: In step 1), the alkyl orthosilicate is selected from one or a combination of two or more of methyl orthosilicate, ethyl orthosilicate, and propyl orthosilicate; the ether-containing silane coupling agent is selected from one or a combination of two or more of (methoxytriethylene glycol ether propyl) trimethoxysilane, trimethyl [3- (2-methoxy) propyl] silane, and polyethylene glycol trimethoxysilyl propyl ether, preferably (methoxytriethylene glycol ether propyl) trimethoxysilane.

4. The dry powder heat-resistant interface treatment agent for new and old concrete according to claim 1, characterized in that: In step 1), the alcohol is selected from one or a combination of two or more of methanol, ethanol, propanol, and isopropanol; and the concentration of the ammonia water is 25-28 wt%.

5. The dry powder heat-resistant interface treatment agent for new and old concrete according to claim 1, characterized in that: In step 2), the mass ratio of the paraffin wax, the surfactant, and the water is 0.5-0.8:0.2-0.3:50; the surfactant is selected from one or a combination of two or more of lauryl betaine, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, Tween 20, and OP-10, preferably hexadecyltrimethylammonium bromide; the paraffin wax is selected from one or a combination of two or more of 18# paraffin wax, 20# paraffin wax, 25# paraffin wax, 30# paraffin wax, 45# paraffin wax, and 58# paraffin wax.

6. The dry powder heat-resistant interface treatment agent for new and old concrete according to claim 1, characterized in that: In step 3), the temperature is controlled at 60-80° C.; the stirring speed is 500-1000 rpm; the reaction time is 3-5 hours; and the precursor solution is added dropwise over 30-60 minutes.

7. The dry powder heat-resistant interface treatment agent for new and old concrete according to claim 1, characterized in that: The carboxylation degree of the carboxymethyl chitosan powder is 80-90%, the pH value is 6-8, and the viscosity is 10-80 mPa.s.

8. Application of the dry powder heat-resistant interface treatment agent for new and old concrete according to any one of claims 1 to 7, characterized in that: The steps include: S1) roughening the old concrete substrate to remove surface residues and drying it until no obvious water is present on the surface; S2) mixing cement, quartz sand, mineral admixtures, organic-inorganic hybrid phase change microcapsules, carboxymethyl chitosan powder, early strength agent, and water reducing agent, and adding water to mix to obtain a slurry; S3) Apply the slurry on the surface of the old concrete base, pour new concrete and maintain.

9. The application of the dry powder heat-resistant interface treatment agent for new and old concrete according to claim 1, characterized in that: In step S2), the mass of the water is 7.5-10 wt % of the dry powder concrete interface treatment agent.

10. The application of the dry powder heat-resistant interface treatment agent for new and old concrete according to claim 1, characterized in that: In step S3), the dry powder concrete interface treatment agent is applied to a thickness of 1-5 mm.