A wet-mixed mortar for plastering robots and its preparation method

Abstract

This invention discloses a wet-mixed mortar for plastering robots, prepared by mixing a dry mixture of wet-mixed mortar with water. The dry mixture consists of the following raw materials: 114-132 parts cement; 211-223 parts dry sand; 464-495 parts manufactured sand; 38-44 parts fly ash; 12-16 parts slag; 1-1.7 parts polyhydroxycarboxylic acid salt; 0.8-1 part branched alkylbenzene sulfonate; 0.7-0.8 parts polycarboxylic acid; 0.3-0.5 parts air-entraining agent; 0.5-0.7 parts dispersant; and 0.1-0.4 parts retarder. The wet-mixed mortar of this invention exhibits good stability and uniformity, significantly extending the open time during transportation and waiting periods. After application to the wall, it promptly triggers hydration and normal setting and hardening, balancing the open time requirements for long-distance transportation with the time constraints of plastering operations. This fully ensures the continuity, reliability, and efficiency of automated construction by the plastering robot.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically a wet-mixed mortar for plastering robots and its preparation method. Background Technology

[0002] With the continuous advancement of modernization and intelligentization in the construction industry, robotic construction has become an inevitable trend for improving project quality, efficiency, and safety, and addressing labor shortages. In the field of plastering, the application of plastering robots can significantly improve the standardization level and operational efficiency of construction, achieving high-quality and highly consistent plastering operations. However, robotic construction places far more stringent requirements on the stability, pumpability, and workability of materials than manual construction.

[0003] Currently, premixed dry mortar commonly used in the market is prone to component separation during long-distance transportation and storage, leading to unstable performance. Precise control of water usage during on-site mixing directly affects the mortar's workability, causing problems such as pumping difficulties and pipe blockages in robotic construction, severely restricting the realization of the efficiency advantages of robots. Furthermore, for high-rise building construction, on-site mixing not only occupies valuable construction space and generates dust pollution, but also increases the frequency of vertical material transportation, which is seriously inconsistent with the continuous, efficient, and standardized characteristics pursued by robotic construction.

[0004] Therefore, developing a ready-to-use, stable, and particularly suitable wet-mixed mortar for robotic pumping and plastering to overcome the inherent defects of dry-mixed mortar and meet the high material requirements of intelligent construction has become a key technical problem urgently needing to be solved in the industry. In view of the above, to overcome the aforementioned technical problems, this invention designs a wet-mixed mortar for plastering robots, thus solving the above-mentioned technical issues. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing premixed dry mortars in robotic plastering applications, such as poor stability, low on-site mixing efficiency, and insufficient compatibility with robotic construction systems. The invention provides a wet-mixed mortar with stable working performance, excellent pumping performance, good anti-sagging performance, and is particularly suitable for plastering robots, as well as its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A wet-mixed mortar for plastering robots is prepared by mixing and stirring a wet-mixed mortar dry mixture with water, characterized in that the wet-mixed mortar dry mixture is composed of the following raw materials in parts by weight:

[0008] Cement 114–132 parts; dry sand 211–223 parts; manufactured sand 464–495 parts; fly ash 38–44 parts; slag 12–16 parts; polyhydroxycarboxylic acid salt 1–1.7 parts; branched alkylbenzene sulfonate 0.8–1 part; polycarboxylic acid 0.7–0.8 parts; air-entraining agent 0.3–0.5 parts; dispersant 0.5–0.7 parts; retarder 0.1–0.4 parts.

[0009] The manufactured sand is quartz particles produced by crushing and processing quartz stone.

[0010] Furthermore, the synergistic effect of cement, fly ash, and slag can significantly reduce the heat of hydration of the cementitious material system. Its composite filling effect is better than that of cement alone, producing a super synergistic effect, which enables the mortar to have both excellent fluidity and cohesiveness, greatly improving its pumpability.

[0011] Furthermore, the polyhydroxycarboxylic acid salt, branched alkylbenzene sulfonate, and polycarboxylic acid high-efficiency water-reducing agent work synergistically to optimize the rheological properties of the mortar, effectively alleviate the bleeding and dehydration of the mortar under long-distance pumping pressure, ensure the smoothness and continuity of the transportation process, and thus meet the high requirements of robotic automated construction for material stability.

[0012] The polyhydroxycarboxylic acid salt is sodium gluconate;

[0013] The branched alkylbenzene sulfonate is one or more of sodium dodecylbenzene sulfonate, polyacrylamide, α-olefin sulfonate, linear alkylbenzene sulfonate, or alkyl glycerol ether sulfonate, and other types of anionic surfactants may also be selected.

[0014] The polycarboxylic acid is a polymer obtained by addition polymerization of unsaturated carboxylic acid monomers, such as polyacrylic acid or polymethacrylic acid.

[0015] The air-entraining agent is one or more of the following: rosin resins, alkyl and alkyl aromatic sulfonic acids, fatty alcohol sulfonates, or saponins.

[0016] The dispersant is sodium hexametaphosphate.

[0017] In this invention, by using a combination of an air-entraining agent and a dispersant, a large number of tiny and stable air bubbles are introduced into the mortar, and the uniform dispersion of the components is ensured. This significantly enhances the water retention and anti-sagging properties of the mortar while ensuring its good workability, making it less prone to sagging and dripping when the robot applies thick layers of plaster to the wall, thus ensuring the quality of construction.

[0018] Furthermore, the retarder is one or more of citrate, phosphate, or lignin sulfonate. The retarder works synergistically with polyhydroxycarboxylic acid salts and polycarboxylic acid superplasticizers to maintain the open time and workability of the mortar even under high ambient temperatures or long transportation times. When the mortar is applied to the wall and mechanically troweled, the adsorption equilibrium of the retarding components undergoes desorption and reconstruction due to water evaporation and physical shearing. The retarding effect gradually weakens, the cement hydration process starts normally, and the mortar sets and hardens in a timely manner, without false setting or prolonged setting without hardening. This balances the open time requirements for long-distance transportation with the early strength formation requirements after application to the wall.

[0019] The preferred dosage of the retarder is 0.2 to 0.3 parts.

[0020] Furthermore, the wet-mixed mortar is prepared by mixing and stirring the dry mixture of wet-mixed mortar with water, specifically by the following method: adding water to the dry mixture of wet-mixed mortar and stirring, adjusting the consistency to 95±5 mm, to obtain the wet-mixed mortar.

[0021] The present invention also provides the above-mentioned wet-mixed mortar dry mixture.

[0022] This invention also provides a method for preparing a dry mixture of wet-mixed mortar, comprising the following steps:

[0023] 1. Raw material selection and preparation: Prepare all raw materials according to the stated weight proportions;

[0024] 2. Aggregate processing: Dry sand and manufactured sand are screened to control their particle size distribution and fineness modulus; generally, the particle size distribution is in Zone II and the fineness modulus is controlled between 2.3 and 2.6.

[0025] 3. Premixing of admixtures: Add polyhydroxycarboxylic acid salts, branched alkylbenzene sulfonates, polycarboxylic acid, air-entraining agents, dispersants and retarders into a mixer and stir until uniform to prepare a composite admixture;

[0026] 4. Mortar mixing: Cement, dry sand, manufactured sand, fly ash and slag are put into a mixer for dry mixing, and then premixed composite admixtures are added. The mixture is then mixed by alternating forward and reverse rotation or high-frequency pulse mixing to obtain a wet-mixed mortar dry mixture.

[0027] Wet-mixed mortar is prepared by adding water to the dry mixture and stirring to adjust the consistency to 95±5 mm.

[0028] The wet-mixed mortar of the present invention has thixotropic and rapid setting characteristics, with a plastic retention time (workable time) ≥7h to ensure the continuity of mechanical conveying and spraying mortar; after being applied to the wall, the setting and hardening process is accelerated due to the shear thinning recovery state, with a final setting time ≤1h.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. Construction adaptability: Through the precise proportioning and synergistic effect of each component, the present invention enables the resulting wet-mixed mortar to have high fluidity, low bleeding rate, high water retention and excellent anti-sagging properties, which can perfectly adapt to the pumping, spraying and leveling processes of plastering robots, effectively avoiding problems such as pipe blockage, hollowing, and cracking, and significantly improving the efficiency and quality of robot construction.

[0031] 2. Stability during pumping and construction: For the long-distance, high-pressure pumping conditions commonly encountered in robotic construction, the mortar of this invention exhibits excellent stability and uniformity, ensuring that its performance does not significantly degrade after long-distance transport. Simultaneously, through the synergistic regulation of the retarding component and water-reducing agent, the mortar has a significantly extended workable open time during transportation and waiting periods. After application and troweling, it promptly triggers hydration and normal setting and hardening, avoiding the risk of pipe blockage during pumping and ensuring that it does not experience prolonged setting or delayed strength after application. This balances the open time requirements of long-distance transport with the time constraints of plastering operations, fully guaranteeing the continuity, reliability, and efficiency of automated robotic plastering construction.

[0032] 3. Green Economy: Making full use of industrial solid waste such as slag and fly ash not only reduces production costs but also aligns with the green, low-carbon, and sustainable development direction of the construction industry. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] Example 1:

[0035] This embodiment provides a wet-mixed mortar for use in plastering robots, the specific components and weight parts of which are shown in Table 1 below:

[0036] Table 1

[0037] Component categories Raw material name weight cementing materials cement 132 aggregate dry sand 223 Manufactured sand 465 Active admixtures fly ash 38 slag 16 admixtures Sodium gluconate 1 Sodium dodecylbenzenesulfonate 1 Polyacrylic acid 0.8 Air-entraining agent AE-1450 0.5 Sodium hexametaphosphate 0.7 Sodium citrate 0.3

[0038] Its preparation method includes the following steps:

[0039] Step 1: Prepare all raw materials according to the weight proportions in the table above. Among them, the cement is PO 42.5 grade Portland cement; the dry sand and manufactured sand both meet the requirements of Class I sand in GB / T 14684, the particle size distribution is Zone II, the fineness modulus is controlled at 2.3~2.6, and the floating powder is pre-screened off.

[0040] Step 2: Premixing of additives: Pour the weighed sodium gluconate, sodium dodecylbenzene sulfonate, polyacrylic acid, soapberry air-entraining agent, sodium hexametaphosphate and sodium citrate into a special additive mixer and stir at normal speed for 3 minutes to make them fully mixed and homogeneous, thus obtaining the composite additive.

[0041] Step 3: Dry Material Mixing: Add the weighed cement, dry sand, manufactured sand, fly ash, and slag to the dry mortar mixer. Mix in the forward direction for 5 minutes, then in the reverse direction for 5 minutes to ensure that all dry materials are mixed evenly.

[0042] Step 4: Preparation of wet mortar: Add the composite admixture prepared in S2 to the dry mix of S3, then start the high-frequency pulse mode of the mixer and stir continuously for 4 minutes to fully and evenly mix the admixture with the dry mix, thus obtaining a stable wet mortar dry mixture for plastering robots (Note: This product is premixed in the factory and can be used after being transported to the construction site and mixed with water according to the predetermined water-cement ratio).

[0043] Example 2:

[0044] This embodiment provides another type of wet-mixed mortar for use with plastering robots, the specific components and weight parts of which are shown in Table 2 below:

[0045] Table 2

[0046] Component categories Raw material name weight cementing materials cement 114 aggregate dry sand 211 Manufactured sand 483 Active admixtures fly ash 44 slag 12 admixtures Sodium gluconate 1.7 Sodium dodecylbenzenesulfonate 0.8 Polyacrylic acid 0.7 Entraining agent 0.3 Sodium hexametaphosphate 0.5 Sodium phosphate 0.25

[0047] The preparation method is the same as in Example 1.

[0048] Performance testing:

[0049] To verify the effectiveness of the present invention, performance tests were conducted on the mortar products obtained in the above embodiments. Before the test, 30 kg of the dry mixture prepared in Example 1 or 2 was taken, poured into a mixer, water was added and stirred for 3 min, and the consistency was adjusted to 95±5 mm before the following tests were conducted.

[0050] Basic performance: The water retention rate, setting time, fluidity, and pressure bleeding rate are tested according to relevant national standards.

[0051] Anti-sagging performance: Apply the pumped mortar to a vertical wall and observe the maximum thickness of the mortar that does not sag.

[0052] The test results are shown in Table 3 below:

[0053] Table 3

[0054] Test Project Example 1 Example 2 Test Standards Water retention rate (%) 98 98 JGJ / T 70 Pressure water exudation rate (%) 22 24 GB / T 25181-2019 Flowability (mm) 188 195 GB / T 2419-2005 Anti-sagging thickness (mm) 3 3 / 28-day compressive strength (MPa) 13.8 14.3 GB / T 17671 Plastic retention time (h) 27.5 22.5 GB / T 25181-2019 Setting time (h) after application 0.7 0.5 /

[0055] Results analysis:

[0056] As shown in the table above, the wet-mixed mortar prepared by this invention has extremely high water retention and excellent fluidity, with a low pressure bleeding rate, indicating that it possesses excellent pumping stability and anti-segregation ability, and can adapt to long-distance, high-pressure pumping in robotic construction. Simultaneously, the mortar exhibits good anti-sagging properties, achieving a 3 mm thick layer of plastering on vertical walls without dripping, fully meeting the stringent requirements of plastering robots for material workability and stability. Furthermore, by introducing an appropriate amount of retarder based on the above mixing ratio, precise and flexible control of the mortar setting time can be achieved. This significantly extends the workable time while ensuring rapid hydration and timely hardening of the mortar after application, preventing prolonged setting or delayed strength. Thus, without sacrificing other properties, the adaptability, continuity, and reliability of robotic plastering construction are systematically improved.

[0057] Comparative Example 1

[0058] According to the formula of Example 1 in CN 113912343A, the plastering mortar was prepared. Its plastic retention time was 4.5h, its fluidity was 185mm, and its setting time was relatively short, which did not meet the requirements for long-term construction by robots.

[0059] In Comparative Example 1, no retarder was added, and silica fume and steel slag admixtures were added, resulting in a short setting time of 5 hours, which could not meet the requirements of long-term construction by robots.

[0060] Comparative Example 2

[0061] In Example 2, no retarder was added to the formulation. The amount of other raw materials and the preparation method were the same as in Example 2. The plastic retention time of the wet-mixed mortar was 4.2 hours.

[0062] Comparative Example 3

[0063] In the formulation of Example 2, 0.5 parts of sodium phosphate were added, and the dosage of other raw materials and preparation method were the same as in Example 2. The resulting wet-mixed mortar had a plastic retention time of 28.5 hours and a wall setting time of 2.5 hours. Increasing the amount of retarder extended the plastic retention time, but also significantly extended the wall setting time. This resulted in slower hardening and a prolonged setting time, which was not conducive to on-site construction.

[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A wet-mixed mortar for plastering robots, prepared by mixing and stirring a dry mixture of wet-mixed mortar with water, characterized in that... The wet-mixed mortar dry mixture is composed of the following raw materials in parts by weight: Cement 114–132 parts; dry sand 211–223 parts; manufactured sand 464–495 parts; fly ash 38–44 parts; slag 12–16 parts; polyhydroxycarboxylic acid salt 1–1.7 parts; branched alkylbenzene sulfonate 0.8–1 part; polycarboxylic acid 0.7–0.8 parts; air-entraining agent 0.3–0.5 parts; dispersant 0.5–0.7 parts; retarder 0.1–0.4 parts.

2. The wet-mixed mortar for plastering robots as described in claim 1, characterized in that, The manufactured sand is quartz particles produced by crushing and processing quartz stone. The polyhydroxycarboxylic acid salt is sodium gluconate; The branched alkylbenzene sulfonate is one or more of sodium dodecylbenzene sulfonate, polyacrylamide, α-olefin sulfonate, linear alkylbenzene sulfonate, or alkyl glycerol ether sulfonate. The air-entraining agent is one or more of the following: rosin resins, alkyl and alkyl aromatic sulfonic acids, fatty alcohol sulfonates, or saponins; The dispersant is sodium hexametaphosphate.

3. The wet-mixed mortar for plastering robots as described in claim 1, characterized in that, The retarder is one or more of citrate, phosphate, or lignin sulfonate.

4. The wet-mixed mortar for plastering robots as described in claim 3, characterized in that... The retarder is sodium citrate or sodium phosphate.

5. The wet-mixed mortar for plastering robots as described in claim 1, characterized in that, The wet-mixed mortar is prepared by adding water to the dry mixture of wet-mixed mortar and stirring, adjusting the consistency to 95±5 mm, to obtain the wet-mixed mortar.

6. The wet-mixed mortar as described in claim 1, characterized in that... The plastic retention time of wet-mixed mortar is ≥7h, and the setting time after application to the wall is ≤1h.

7. A wet-mixed mortar dry mixture for use in plastering robots, comprising the following raw materials in parts by weight: Cement 114–132 parts; dry sand 211–223 parts; manufactured sand 464–495 parts; fly ash 38–44 parts; slag 12–16 parts; polyhydroxycarboxylic acid salt 1–1.7 parts; branched alkylbenzene sulfonate 0.8–1 part; polycarboxylic acid 0.7–0.8 parts; air-entraining agent 0.3–0.5 parts; dispersant 0.5–0.7 parts; retarder 0.1–0.4 parts.

8. The method for preparing wet-mixed mortar dry mixture for plastering robots as described in claim 7, characterized in that... The method includes the following steps: (1) Raw material selection and preparation: Prepare all raw materials according to the stated weight proportions; (2) Aggregate treatment: Dry sand and manufactured sand are screened to control their particle size distribution to Zone II and the fineness modulus to be controlled at 2.3~2.6; (3) Premixing of admixtures: Add polyhydroxycarboxylic acid salts, branched alkylbenzene sulfonates, polycarboxylic acid, air-entraining agents, dispersants and retarders into a mixer and stir and mix evenly to prepare a composite admixture; (4) Mortar mixing: Cement, dry sand, machine sand, fly ash and slag are put into a mixer for dry mixing, and then premixed composite admixtures are added. The mixture is mixed by alternating forward and reverse rotation or high-frequency pulse mixing to obtain wet-mixed mortar dry mixture.