Dry-mixed masonry mortar with high water retention and high bonding strength

Abstract

The invention relates to the technical field of building materials, and discloses high-water-retention and high-bonding-strength dry-mixed masonry mortar which is prepared from 280-320 parts of ordinary Portland cement, 80-120 parts of fly ash, 540-630 parts of graded quartz sand, 8-20 parts of functional dispersion master batch and a defoaming agent. The functional dispersion master batch comprises polyvinyl alcohol powder, D-sorbitol, sodium tetraborate decahydrate and anhydrous sodium metasilicate. The preparation method adopts a low-temperature high-speed master batch prefabrication and post-mixing process. According to the preparation method disclosed by the invention, by utilizing the preferential complexing action of D-sorbitol and borate ions, instantaneous gelation at the initial stage of stirring is inhibited, and polyvinyl alcohol is ensured to be fully dissolved and dispersed; along with hydration, released borate radicals and polyvinyl alcohol are subjected to in-situ delayed cross-linking, and a water-resistant net structure is formed. The problems that traditional mortar is prone to flash coagulation and poor in water resistance are effectively solved, and the mortar has excellent construction performance and water-resistant bonding strength.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a dry-mixed masonry mortar with high water retention and high bonding strength. Background Technology

[0002] Dry-mixed masonry mortar is a widely used cementitious material in construction engineering, mainly used for bonding and laying masonry blocks. To improve the shortcomings of traditional cement mortar, such as poor water retention, low bond strength, and high brittleness, polymer powders are often added for modification. Polyvinyl alcohol, due to its excellent film-forming properties and bonding enhancement effect on the cement matrix, is often used as a water-retaining thickener and binder, significantly improving the interfacial adhesion between the mortar and the substrate, as well as the mortar's own flexibility.

[0003] However, polyvinyl alcohol (PVA) molecules contain a large number of hydrophilic hydroxyl groups, resulting in poor water resistance after film formation. In humid environments or under continuous immersion conditions, PVA films easily absorb water, swell, or even re-dissolve, causing a significant decrease in the bonding strength of the mortar and easily leading to engineering quality problems such as hollowing, cracking, or even peeling of the wall finish.

[0004] To improve the water resistance of polyvinyl alcohol (PVA), existing technologies often introduce borate as a crosslinking agent. The borate ions, ionized in water, can complex with the hydroxyl groups on the PVA molecular chains, forming a crosslinked polymer with a three-dimensional network structure, thereby reducing the hydrophilicity of PVA. However, this crosslinking reaction usually occurs extremely rapidly and uncontrollably. In the initial stage of mixing mortar with water, the highly reactive borate ions immediately react with partially dissolved PVA, causing the slurry to rapidly lose its fluidity, resulting in instantaneous gelation or clumping. This uncontrollable early crosslinking not only severely shortens the mortar's open time, making construction difficult, but also hinders the uniform dispersion and spread of PVA molecules within the mortar, ultimately affecting the final modification effect.

[0005] Therefore, how to effectively suppress the instantaneous cross-linking reaction in the initial stage of mixing while ensuring that polyvinyl alcohol modified mortar has excellent water-resistant bonding strength after hardening, and ensure the fluidity and dispersion uniformity during the construction stage, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a high water retention and high bonding strength dry-mixed masonry mortar, which solves the problem that existing polyvinyl alcohol modified dry-mixed mortars, when borates are added to improve water resistance, are prone to instantaneous gelation in the early stages of mixing due to uncontrollable crosslinking reaction rates, thus seriously affecting construction performance and dispersion uniformity.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a high water retention and high bonding strength dry-mixed masonry mortar, which adopts the following technical solution: A high water-retention and high bonding strength dry-mix masonry mortar is made from raw materials comprising the following parts by weight: Ordinary Portland cement: 280-320 parts; Fly ash: 80-120 parts; Graded quartz sand: 540-630 parts; Functional dispersion masterbatch: 8-20 parts; Defoamer: 0.5-1.2 parts.

[0008] By employing the above technical solution, the dissolution and crosslinking rates of polyvinyl alcohol in the borate system are controlled by utilizing the chemical reaction characteristics of each component in the functional dispersion masterbatch. The specific mechanism of action is as follows: First, during the initial mixing of mortar with water, the polyhydroxyl structure in the D-sorbitol molecule preferentially undergoes a complexation reaction with borate ions generated by the ionization of sodium tetraborate decahydrate. Since the binding rate of D-sorbitol to borate is higher than that of polyvinyl alcohol, this process consumes free borate ions in the liquid phase, inhibiting early contact between borate and polyvinyl alcohol molecular chains. This mechanism prevents instantaneous gelation of the mortar, allowing sufficient time for the polyvinyl alcohol powder to dissolve and disperse uniformly in the cement paste, maintaining the fluidity of the freshly mixed mortar.

[0009] Secondly, as the cement hydration reaction proceeds, the pH value and ion concentration of the slurry change, and the D-sorbitol-borate complex gradually releases borate ions. At this time, the dispersed polyvinyl alcohol molecular chains undergo a delayed cross-linking reaction with the released borate ions, forming a borate ester bond cross-linked polymer with a three-dimensional network structure in situ within the hardened mortar. This cross-linked structure reduces the water solubility of the polyvinyl alcohol film, allowing the hardened mortar to maintain high bonding strength in damp or water-immersed environments.

[0010] Finally, the silica gel generated by the hydration of anhydrous sodium metasilicate forms an inorganic skeleton with the cement hydration products. The polyvinyl alcohol crosslinking network fills the pores of the skeleton. The inorganic components and organic network interpenetrate with each other, which improves the density and interfacial bonding performance of the mortar.

[0011] Preferably, the functional dispersion masterbatch is made from raw materials comprising the following parts by weight: Polyvinyl alcohol powder: 400-700 parts; D-sorbitol: 300-500 parts; Sodium tetraborate decahydrate: 80-120 parts; Anhydrous sodium metasilicate: 250-450 parts.

[0012] By adopting the above technical solution, the proportions of each active component in the masterbatch are limited. The amount of D-sorbitol can effectively form early complexes with borate, while anhydrous sodium metasilicate provides an alkaline environment to assist in strength building. Combined with a specific proportion of polyvinyl alcohol, the performance stability of the mortar is ensured from the freshly mixed state to the hardened state.

[0013] Preferably, the ordinary silicate cement is P.O42.5 grade cement; the fly ash is Class F II fly ash; the particle size distribution of the graded quartz sand is 40-100 mesh; and the defoamer is a polyether modified polysiloxane defoamer.

[0014] By adopting the above technical solutions, Class F II fly ash improves the workability of mortar and fills micropores; 40-100 mesh graded quartz sand optimizes aggregate bulk density, reduces cementitious material usage and shrinkage risk; polyether-modified polysiloxane defoamer reduces air bubbles introduced during mixing and lowers the macroscopic porosity of the hardened body.

[0015] Preferably, the polyvinyl alcohol powder is partially hydrolyzed polyvinyl alcohol with a degree of hydrolysis of 87.0-89.0 mol%, an average degree of polymerization of 1700-2400, and a fineness passing through a 120-mesh sieve.

[0016] By adopting the above technical solution, partially hydrolyzed polyvinyl alcohol with a degree of hydrolysis of 87.0-89.0 mol% is selected. Its cold water solubility characteristics ensure that it plays a thickening and water-retaining role under normal temperature construction conditions; the degree of polymerization of 1700-2400 ensures the strength of the polymer film; and the fineness index of 120 mesh helps to improve the dissolution rate and prevent dissolution lag caused by excessively coarse particles.

[0017] Preferably, the modulus of the anhydrous sodium metasilicate is 0.9-1.1.

[0018] By adopting the above technical solution, the low-modulus anhydrous sodium metasilicate contains high-activity sodium oxide, which can quickly participate in the hydration reaction to provide an alkaline environment, promote the early setting and hardening of cement and activate the activity of fly ash.

[0019] Preferably, the mass ratio of D-sorbitol to sodium tetraborate decahydrate in the functional dispersion masterbatch is 3.7:1-4.2:1, and the mass ratio of polyvinyl alcohol powder to sodium tetraborate decahydrate is 5:1-6:1.

[0020] By adopting the above technical solution, the mass ratio of D-sorbitol to sodium tetraborate decahydrate is controlled at 3.7:1-4.2:1, aiming to establish a suitable reaction equilibrium: preventing mortar fluidity loss through early complexation while ensuring effective release of borate ions for crosslinking in the later stages. The mass ratio of polyvinyl alcohol to sodium tetraborate decahydrate is controlled at 5:1-6:1, enabling the formation of crosslinking points with a suitable density between polymer chain segments, thus improving water resistance while maintaining the mortar's flexibility.

[0021] Preferably, the total weight of ordinary silicate cement, fly ash, graded quartz sand, functional dispersant and defoamer in the dry-mixed masonry mortar is 1000 parts.

[0022] Secondly, the present invention provides a method for preparing high water retention and high bonding strength dry-mixed masonry mortar, using the following technical solution: A method for preparing a high water-retention and high-bonding-strength dry-mix masonry mortar includes the following steps: S1: Polyvinyl alcohol powder, D-sorbitol, sodium tetraborate decahydrate and anhydrous sodium metasilicate are mixed evenly in proportion to obtain functional dispersion masterbatch; S2: Put ordinary silicate cement, fly ash and graded quartz sand into a mixer for premixing; S3: Add the functional dispersant masterbatch and defoamer obtained in step S1 to the mixer in step S2, continue stirring until evenly dispersed, and then discharge and package.

[0023] By adopting the above technical solution, a "masterbatch pre-preparation + post-mixing" process is used. First, the functional components are pre-prepared into masterbatch, so that the crosslinking agent, regulator and polymer can be uniformly contacted. Then, the masterbatch is dispersed into the aggregate and cementitious materials, avoiding the problem of uneven dispersion caused by the direct addition of trace additives.

[0024] Preferably, in step S1, the mixing is carried out in a mixer equipped with a cooling and temperature control device, the mixing temperature is controlled at 25-30°C, and the mixing time is 3-5 minutes; the spindle speed of the mixer is controlled at 500-800 rpm.

[0025] By adopting the above technical solution, in the preparation process of functional dispersion masterbatch: a rotation speed of 500-800 rpm is used to disperse the agglomeration of raw materials using mechanical shear force; temperature control measures of 25-30℃ are taken to prevent polyvinyl alcohol from softening or agglomerating due to frictional heat generation, thus ensuring the powder flowability and storage stability of the masterbatch.

[0026] This invention provides a dry-mix masonry mortar with high water retention and high bonding strength. It has the following beneficial effects: 1. This invention introduces D-sorbitol into a functional dispersion masterbatch, utilizing its preferential complexation with sodium tetraborate decahydrate to consume free borate ions in the initial stage of mixing and inhibit premature cross-linking of borate and polyvinyl alcohol. This technical solution avoids instantaneous gelation during mortar mixing with water, ensuring that polyvinyl alcohol powder can be fully dissolved and evenly spread in the slurry, thereby maintaining good mortar fluidity and suitable construction operation time.

[0027] 2. As the cement hydration reaction proceeds, the D-sorbitol-borate complex gradually releases borate ions, which undergo in-situ delayed crosslinking with the dispersed polyvinyl alcohol to generate a borate ester crosslinked polymer with a network structure. This crosslinking structure reduces the water solubility of the polyvinyl alcohol film, enabling the hardened mortar to maintain high bonding strength in humid or water-immersed environments, thus improving the problem of traditional polyvinyl alcohol modified mortar easily swelling when exposed to water, leading to a decrease in bonding strength.

[0028] 3. This invention employs a masterbatch prefabrication process, mixing polyvinyl alcohol with modified components under low-temperature, high-speed conditions to prevent material agglomeration upon heating and ensure uniform dispersion of functional components. Combined with the silica gel generated from the hydration of anhydrous sodium metasilicate, it promotes the interpenetration and filling of the inorganic framework and organic network, increasing the density of the mortar matrix and thus enhancing the overall mechanical properties and weather resistance of the finished product. Detailed Implementation

[0029] Preparation Examples 1-3 Preparation Example 1: This preparation example provides a functional dispersion masterbatch, including the following steps: Weigh out 400 parts by weight of polyvinyl alcohol powder, 300 parts by weight of D-sorbitol, 80 parts by weight of sodium tetraborate decahydrate, and 250 parts by weight of anhydrous sodium metasilicate. The above raw materials are put into a high-speed plow mixer with a cooling jacket and mixed for 4 minutes at a spindle speed of 600 rpm and a temperature of 25°C. The resulting material is a functional dispersion masterbatch, which is then sealed for later use.

[0030] Preparation Example 2: This preparation example provides a functional dispersion masterbatch, including the following steps: Weigh out 700 parts by weight of polyvinyl alcohol powder, 500 parts by weight of D-sorbitol, 120 parts by weight of sodium tetraborate decahydrate, and 450 parts by weight of anhydrous sodium metasilicate. The above raw materials are put into a high-speed vortex mixer and mixed for 3 minutes at a spindle speed of 800 rpm and a temperature of 30°C. The resulting material is a functional dispersion masterbatch, which is then sealed for later use.

[0031] Preparation Example 3: This preparation example provides a functional dispersion masterbatch, including the following steps: Weigh out 550 parts by weight of polyvinyl alcohol powder, 400 parts by weight of D-sorbitol, 100 parts by weight of sodium tetraborate decahydrate, and 350 parts by weight of anhydrous sodium metasilicate. The above raw materials are put into a high-speed plow mixer and mixed for 5 minutes at a spindle speed of 500 rpm and a temperature of 25°C. The resulting material is a functional dispersion masterbatch, which is then sealed for later use.

[0032] Examples 1-4 Example

[0033] This embodiment provides a high water retention and high bonding strength dry-mix masonry mortar, including the following steps: Step 1: Weigh 320.0 parts by weight of ordinary Portland cement, 80.0 parts by weight of fly ash, and 588.9 parts by weight of graded quartz sand, and put them into a twin-shaft zero-gravity mixer. Premix for 60 seconds at a speed of 50 rpm. Step 2: Add 10.3 parts by weight of the functional dispersion masterbatch obtained in Preparation Example 1 and 0.8 parts by weight of the polyether-modified polysiloxane defoamer to the mixer; Step 3: Start the mixer and continue mixing for 180 seconds at a speed of 50 rpm until the material is evenly dispersed. Discharge and package to obtain the finished product. Example

[0034] This embodiment provides a high water retention and high bonding strength dry-mix masonry mortar, including the following steps: Step 1: Weigh 280.0 parts by weight of ordinary Portland cement, 120.0 parts by weight of fly ash, and 581.3 parts by weight of graded quartz sand, and put them into a twin-shaft zero-gravity mixer. Premix for 45 seconds at a speed of 60 rpm. Step 2: Add 17.7 parts by weight of the functional dispersion masterbatch obtained in Preparation Example 2 and 1.0 part of polyether-modified polysiloxane defoamer to the mixer; Step 3: Start the mixer and continue mixing for 240 seconds at a speed of 60 rpm until the material is evenly dispersed. Discharge and package to obtain the finished product. Example

[0035] This embodiment provides a high water retention and high bonding strength dry-mix masonry mortar, including the following steps: Step 1: Weigh 300.0 parts by weight of ordinary Portland cement, 100.0 parts by weight of fly ash, and 585.2 parts by weight of graded quartz sand, and put them into a twin-shaft zero-gravity mixer. Premix for 90 seconds at a speed of 45 rpm. Step 2: Add 14.0 parts by weight of the functional dispersion masterbatch obtained in Preparation Example 3 and 0.8 parts by weight of the polyether-modified polysiloxane defoamer to the mixer; Step 3: Start the mixer and continue mixing for 300 seconds at a speed of 45 rpm until the material is evenly dispersed. Discharge and package to obtain the finished product. Example

[0036] This embodiment provides a high water retention and high bonding strength dry-mix masonry mortar, including the following steps: Step 1: Weigh 310.0 parts by weight of ordinary Portland cement, 90.0 parts by weight of fly ash, and 585.2 parts by weight of graded quartz sand, and put them into a twin-shaft zero-gravity mixer. Premix for 60 seconds at a speed of 55 rpm. Step 2: Add 14.0 parts by weight of the functional dispersion masterbatch obtained in Preparation Example 3 and 0.8 parts by weight of the polyether-modified polysiloxane defoamer to the mixer; Step 3: Start the mixer and continue mixing for 210 seconds at a speed of 55 rpm until the material is evenly dispersed. Discharge and package to obtain the finished product.

[0037] Comparative Examples 1-5 Comparative Example 1: This comparative example provides a conventional dry-mix masonry mortar. Compared with Example 3, the difference is that the functional dispersant masterbatch is not used; instead, conventional commercial additives are used. Specifically, 14.0 parts by weight of the functional dispersant masterbatch are replaced with 0.3 parts by weight of hydroxypropyl methylcellulose and 5.0 parts by weight of redispersible latex powder, and 8.7 parts by weight of graded quartz sand are added to maintain a consistent total weight. The remaining preparation steps and raw materials are the same.

[0038] Comparative Example 2: This comparative example provides a dry-mixed mortar lacking a delayed crosslinking component. The difference from Example 3 is that sodium tetraborate decahydrate was not added when preparing the functional dispersion masterbatch, and the missing mass was made up by graded quartz sand. The other raw material types, amounts, and preparation processes are the same.

[0039] Comparative Example 3: This comparative example provides a dry-mixed mortar lacking a competing coordination shielding component. The difference from Example 3 is that D-sorbitol was not added when preparing the functional dispersion masterbatch, and the missing mass was made up by graded quartz sand. The other raw material types, amounts, and preparation processes are the same.

[0040] Comparative Example 4: This comparative example provides a dry-mixed mortar lacking an interface reinforcement component. The difference from Example 3 is that anhydrous sodium metasilicate was not added when preparing the functional dispersion masterbatch, and the missing mass was made up by graded quartz sand. The other raw material types, amounts, and preparation processes are the same.

[0041] Comparative Example 5: This comparative example provides a dry-mixed mortar without a pre-dispersion process. The difference from Example 3 is that no functional dispersing masterbatch was prepared in advance. Instead, polyvinyl alcohol powder, D-sorbitol, sodium tetraborate decahydrate, and anhydrous sodium metasilicate were directly added to the mixer along with cement, fly ash, and quartz sand according to the absolute mass corresponding to that in Example 3. The types, total amounts, and mixing times of the remaining raw materials were the same.

[0042] Test Example 1: Experimental description: This test aims to verify the rheological state of the dry-mixed mortars obtained in each embodiment and comparative example during the water mixing stage, focusing on evaluating whether there is an instantaneous gelation (flash coagulation) phenomenon caused by premature reaction between borate and polyvinyl alcohol, and the impact of the premixing process of the dispersion masterbatch on the uniformity of the mortar.

[0043] Experimental steps: The tests were conducted according to JGJ / T70-2009 "Standard for Test Methods of Basic Performance of Building Mortar". The laboratory ambient temperature was controlled at 23±2℃ and the relative humidity at 50±5%. 3.0 parts of each of the dry-mixed mortar products from Examples 1-4 and Comparative Examples 1-5 were weighed and tap water was added at a water-to-material ratio of 0.16. A planetary mortar mixer was used for mixing, with the program set to low speed for 30 seconds, high speed for 60 seconds, standing for 90 seconds, and then high speed for another 60 seconds. After mixing, the surface state of the mortar was immediately observed, and the presence of clumps, particle aggregation, or abnormal gelation was recorded. The initial consistency value was then measured using a mortar consistency meter. The measured mortar was placed in a non-absorbent container and covered with a film to prevent moisture evaporation. After standing for 2 hours, the consistency value was measured again, and the consistency loss rate was calculated.

[0044] Experimental data (see Table 1): Table 1 Group Initial consistency (mm) Consistency (mm) after 2 hours 2h consistency loss rate (%) Apparent state description Construction feasibility assessment Example 1 94 89 5.3 The slurry is fine and uniform with good rheological properties. feasible Example 2 98 91 7.1 The slurry is uniform and has strong cohesive properties. feasible Example 3 92 88 4.3 The slurry is fine and free from bleeding and segregation. feasible Example 4 95 87 8.4 The slurry is uniform and has a smooth feel when handled. feasible Comparative Example 1 93 82 11.8 The slurry is normal, but slightly dry. feasible Comparative Example 2 96 89 7.3 The slurry is uniform and similar to that in the example. feasible Comparative Example 3 18 -- -- It consists of rubbery fragments that cannot be shaped. Not feasible Comparative Example 4 97 93 4.1 The slurry is relatively thin and slightly bleeds. feasible Comparative Example 5 82 70 14.6 Contains white gel particles, even uneven Not feasible Note: "--" indicates that the test cannot be performed due to abnormal slurry condition.

[0045] in conclusion: The initial consistency of the freshly mixed mortar in Examples 1 to 4 was all within the range of 90-100 mm, with a uniform and fine slurry consistency and a consistency loss rate of less than 10% after 2 hours. These results indicate that D-sorbitol preferentially complexes with borate ions in the liquid phase, inhibiting early contact between borate and polyvinyl alcohol, preventing instantaneous gelation of the mortar during the mixing stage, and ensuring the rheological stability and construction period of the mortar.

[0046] In Comparative Example 3, without D-sorbitol, flash coagulation occurred during stirring, resulting in a slurry of uncohesive fragments, confirming the necessity of competing coordination components for controlling borate activity. In Comparative Example 5, without pre-dispersion masterbatch processing, the initial slurry consistency was low and contained visible gel particles, indicating that direct mixing could not avoid high-concentration cross-linking in localized areas, and that pre-dispersion played a crucial role in the uniform distribution of trace functional components. The consistency loss rate of Comparative Example 1 was slightly higher than that of the Example group, suggesting that D-sorbitol and its complexes played an auxiliary water-retention role in the system.

[0047] Test Example 2: Experimental description: This test aims to evaluate the water retention performance and interfacial bond strength of the hardened mortar, especially by verifying the strength retention rate under water immersion conditions, the modification effect of the borate in-situ crosslinking system on the water resistance of polyvinyl alcohol, and the contribution of silicate components to the interfacial strength.

[0048] The test subjects were the samples that could be molded normally and were constructible in Test Example 1, namely Examples 1-4, Comparative Examples 1, 2, and 4. Comparative Examples 3 and 5 were not tested because they could not be molded normally.

[0049] Experimental steps: Examples 1-4, Comparative Examples 1, 2, and 4, which were able to be formed normally in Test Example 1, were selected as test objects. Tests were conducted according to GB / T25181-2019 and JGJ / T70-2009 standards. The water retention rate of the mortar was determined using the vacuum filtration method. Freshly mixed mortar was applied to a concrete reference slab and formed into specimens measuring 40mm × 40mm. The tensile bond strength of the original strength specimens was determined after curing for 14 days at 23±2℃ and 60±5% relative humidity. The water-resistant specimens were first cured under the above conditions for 7 days, then immersed in water at 20±2℃ for 7 days. After drying the surface, the tensile bond strength was determined. The water softening coefficient was calculated based on the ratio of the water-resistant strength to the original strength.

[0050] Experimental data (see Table 2): Table 2 Group Water retention rate (%) 14-day tensile bond strength - original strength (MPa) 14-day tensile bond strength - water resistance (MPa) Water softening coefficient Example 1 98.4 1.24 1.09 0.88 Example 2 99.2 1.45 1.33 0.92 Example 3 98.7 1.36 1.21 0.89 Example 4 98.1 1.28 1.14 0.89 Comparative Example 1 94.5 0.98 0.72 0.73 Comparative Example 2 98.3 1.15 0.44 0.38 Comparative Example 4 97.8 0.82 0.69 0.84 in conclusion: The water retention rates of Examples 1 to 4 were all higher than 98%, which was superior to the cellulose ether system of Comparative Example 1, indicating that the polyhydroxy component, after being compounded with polyvinyl alcohol, enhanced the binding capacity of free water through hydrogen bonding. Regarding adhesive strength, the original strength of the Example group was significantly higher than that of Comparative Example 4, which lacked anhydrous sodium metasilicate, confirming that the inorganic gel generated by the hydration reaction of the silicate component enhanced the interfacial adhesion.

[0051] Water resistance tests showed that Comparative Example 2, without the addition of borate, experienced a significant decrease in strength after immersion in water, with a softening coefficient of only 0.38. This indicates that the unmodified polyvinyl alcohol film swelled or redissolved in the water environment, leading to adhesive failure. The water resistance softening coefficients of Examples 1-4 remained above 0.88, indicating that as cement hydration consumed D-sorbitol, the released borate ions and polyvinyl alcohol molecular chains underwent in-situ cross-linking in the later stages of hardening, constructing a water-resistant three-dimensional network structure. This limited the water absorption and swelling of the polymer film, significantly improving the water-resistant adhesive stability of the mortar.

Claims

1. A high water retention high bond strength dry mix masonry mortar, characterized in that, The functional dispersion masterbatch is made from raw materials comprising the following weight parts: Ordinary Portland cement: 280-320 parts; Fly ash: 80-120 parts; Graded quartz sand: 540-630 parts; Functional dispersion masterbatch: 8-20 parts; Defoaming agent: 0.5-1.2 parts.

2. A high water retaining high bonding strength dry mix masonry mortar as claimed in claim 1, wherein, The functional dispersion masterbatch is made from raw materials comprising the following weight parts: Polyvinyl alcohol powder: 400-700 parts; D-sorbitol: 300-500 parts; Sodium tetraborate decahydrate: 80-120 parts; Anhydrous sodium metasilicate: 250-450 parts.

3. A high water retaining and high bonding strength dry mix masonry mortar according to claim 1, characterized in that, The ordinary Portland cement is P.O 42.5 grade cement; the fly ash is F-class II grade fly ash; the graded quartz sand has a particle size distribution of 40-100 mesh; and the defoaming agent is a polyether-modified polysiloxane defoaming agent.

4. A high water retaining and high bonding strength dry mix masonry mortar according to claim 2, characterized in that, The polyvinyl alcohol powder is a partially alcoholized polyvinyl alcohol with a fineness of over 120 mesh.

5. A high water retaining and high bonding strength dry mix masonry mortar as claimed in claim 2, wherein, The mass ratio of D-sorbitol to sodium tetraborate decahydrate in the functional dispersion masterbatch is 3.7:1-4.2:1, and the mass ratio of polyvinyl alcohol powder to sodium tetraborate decahydrate is 5:1-6:

1.

6. A high water retaining and high bonding strength dry mix masonry mortar as claimed in claim 1, wherein, The preparation steps of the masonry mortar are as follows: S1: uniformly mix the polyvinyl alcohol powder, D-sorbitol, sodium tetraborate decahydrate, and anhydrous sodium metasilicate in proportion to obtain a functional dispersion masterbatch; S2: pre-mix the ordinary Portland cement, fly ash, and graded quartz sand in a mixer; S3: add the functional dispersion masterbatch and defoaming agent obtained in step S1 to the mixer of step S2, continue to stir until uniformly dispersed, and then discharge and package.

7. A high water retaining high bonding strength dry mix masonry mortar as claimed in claim 6, wherein, In step S1, the mixing is performed in a mixer with a cooling temperature control device, the mixing temperature is controlled at 25-30℃, and the mixing time is 3-5 minutes.

8. A high water retaining high bonding strength dry mix masonry mortar as claimed in claim 7, wherein, In step S1, the main shaft rotation speed of the mixing is controlled at 500-800 rpm.

9. A high water retaining and high bonding strength dry mix masonry mortar as claimed in claim 6, wherein, In steps S2 and S3, a double-shaft gravity-free mixer is used.

10. A high water retaining and high bonding strength dry mix masonry mortar as claimed in claim 6, wherein, The pre-mixing time in step S2 is 45-90 seconds, and the stirring rotation speed is 45-60 rpm; the continued stirring time in step S3 is 180-300 seconds, and the stirring rotation speed is 45-60 rpm.