Aeolian sand mortar internally doped with aluminate coupling agent modified fly ash and preparation method of aeolian sand mortar

Abstract

The invention provides aeolian sand mortar internally doped with aluminate coupling agent modified fly ash and a preparation method of the aeolian sand mortar. The aeolian sand mortar comprises the following raw materials by mass: 10-40g of modified fly ash; 60 to 90 g of cement; 300 to 350 g of aeolian sand; 45 to 55g of water; wherein the modified fly ash is prepared through wet modification of an aluminate coupling agent, and the preparation method of the modified fly ash comprises the following steps: mixing the aluminate coupling agent and absolute ethyl alcohol according to a mass ratio of 1: (3-5), heating, and stirring for the first time until a transparent solvent is formed; and adding the transparent solvent and fly ash into water together, stirring for the second time to form slurry, and drying to obtain the super-hydrophobic modified fly ash. Through innovative selection of internal doping materials and optimization of a preparation process, the mortar has excellent, lasting and stable hydrophobic performance, the anti-permeability, compressive strength, bonding strength and other performance of the mortar are remarkably improved, and the strict requirements of modern constructional engineering for high performance and long service life of the mortar are met.

Description

Technical Field

[0001] The invention relates to the technical field of building mortar materials, and in particular to aerodynamic sand mortar containing fly ash modified by an aluminate coupling agent and a preparation method thereof. Background Art

[0002] In the construction industry, mortar, a crucial bonding and filling material, is widely used in various processes, including wall construction, floor leveling, and wall plastering. Its performance is directly related to the stability, durability, and safety of building structures. However, traditional mortars generally suffer from poor waterproofing, which makes it easy for moisture to penetrate the mortar.

[0003] Moisture intrusion can have a range of serious consequences. First, it significantly reduces the bond strength of mortar, weakening the connections between bricks, blocks, and other wall materials, reducing the overall stability of the wall and increasing the risk of cracking, deformation, and even collapse. Second, the repeated freezing and thawing of moisture within the mortar pores can generate frost heave stress, destroying the mortar's internal structure, causing it to flake and pulverize, significantly shortening its service life. Furthermore, moisture can carry various corrosive agents, such as chloride and sulfate ions, which accelerate the corrosion of steel bars and chemical attack on building materials, further threatening the durability of building structures.

[0004] While there are currently several methods for improving mortar waterproofing, such as using waterproofing agents and surface coatings, these approaches have limitations. The addition of waterproofing agents can affect other mortar properties, such as fluidity and setting time. Surface coatings can be easily damaged during construction or fall off after long-term use, resulting in unstable waterproofing and difficulty meeting the high-performance, long-life requirements of construction projects. Therefore, developing a mortar with superior hydrophobic properties to fundamentally address the issue of water intrusion and improve its impermeability, durability, and mechanical properties is of great practical significance and holds broad application prospects. Summary of the Invention

[0005] In order to solve the above-mentioned defects, the present invention provides a wind-blown sand mortar with fly ash modified by an aluminate coupling agent and a preparation method thereof. The present invention, through the innovative selection of internal admixture materials and the optimization of the preparation process, enables the mortar to have excellent and long-lasting and stable hydrophobic properties, while significantly improving its impermeability, compressive strength, bonding strength and other properties, thereby meeting the strict requirements of modern construction projects for high performance and long life of mortar.

[0006] In a first aspect, the present invention provides a mortar containing fly ash modified with an aluminate coupling agent, comprising the following raw materials in the following mass ratios:

[0007] Modified fly ash 10-40g;

[0008] Cement 60-90g;

[0009] 300-350g of aeolian sand;

[0010] 45-55g water;

[0011] The modified fly ash is prepared by wet modification with an aluminate coupling agent, and the preparation method comprises the following steps:

[0012] An aluminate coupling agent and anhydrous ethanol are mixed in a mass ratio of 1: (3-5), heated, and stirred for the first time to form a transparent solvent; the transparent solvent and fly ash are added into water together, stirred for the second time to form a slurry, and dried to obtain modified fly ash.

[0013] Preferably, the heating temperature is 50-70° C., and the first stirring rate is 800-1200 r / min.

[0014] Preferably, the solid-liquid ratio of fly ash to water is g:mL=1:(2-4).

[0015] Preferably, the mass ratio of the aluminate coupling agent to the fly ash is (1-7):100.

[0016] Preferably, the second stirring rate is 1200-1800 r / min, and the second stirring time is 30-60 minutes;

[0017] Preferably, the drying temperature is 110-130° C., and the drying time is 0.5-2 h.

[0018] Preferably, the particle size of the aeolian sand is in the range of 0.15 to 0.5 mm.

[0019] Preferably, the cement is P·O 42.5R type ordinary Portland cement.

[0020] In a second aspect, the present invention provides a method for preparing aeolian sand mortar containing fly ash modified with an aluminate coupling agent as described above, comprising the following steps:

[0021] (1) Weigh the modified fly ash, cement and aeolian sand according to the weight ratio and mix them evenly;

[0022] (2) adding water and wet mixing until a homogeneous slurry is formed;

[0023] (3) The slurry was injected into the mold and vibrated to form the slurry, and then cured for 7 days at a temperature of 20±5°C and a relative humidity of 90±5% to obtain a hydrophobic aeolian sand mortar specimen.

[0024] Preferably, the dry mixing time is 20 to 40 minutes, the wet mixing time is 5 to 15 minutes, and the vibration time is 30 to 90 seconds.

[0025] Preferably, the performance parameters of the hydrophobic aeolian sand mortar test block include: a contact angle of up to 140°; a cumulative water absorption rate of ≤1.5%; and a 28-day compressive strength of ≥40 MPa.

[0026] In summary, the present invention provides a mortar containing fly ash modified with an aluminate coupling agent and a preparation method thereof. The present invention has the following beneficial effects:

[0027] (1) Hydrophobicity is greatly improved:

[0028] Rigorous experimental testing has shown that aeolian sand mortar containing fly ash modified with an aluminate coupling agent, prepared using the process of this invention, exhibits a contact angle of up to 140°. This exceptional hydrophobicity makes it virtually impossible for water to adhere to or penetrate the mortar surface, fundamentally reducing the possibility of water intrusion into the mortar. This effectively blocks the passage of corrosive media into the mortar along with the water, significantly enhancing the mortar's waterproof properties.

[0029] (2) Mechanical properties are significantly enhanced:

[0030] Compared to conventional mortar, the aeolian sand mortar containing fly ash modified with an aluminate coupling agent exhibits improved compressive and bond strengths, rather than a decrease. This is due to the multiple positive effects of the modified fly ash within the mortar: filling pores, optimizing the microstructure, and participating in cement hydration reactions. These effects enhance the density of the mortar's internal structure and strengthen the adhesion between its components, enabling better coordination and coordination under load, significantly improving the overall mechanical properties.

[0031] (3) Significant improvement in impermeability and durability:

[0032] Due to the mortar's excellent hydrophobic properties and optimized internal structure, moisture is less likely to penetrate the mortar's pores during water penetration and freeze-thaw cycles, effectively reducing damage to the mortar structure caused by water expansion upon freezing, significantly improving the mortar's impermeability and frost resistance. Furthermore, this improved impermeability effectively prevents the intrusion of corrosive media such as chloride and sulfate ions, further enhancing the mortar's durability and extending the service life of the building structure.

[0033] (IV) Overcoming existing technical difficulties:

[0034] The aeolian sand mortar containing fly ash modified with an aluminate coupling agent and its preparation method fundamentally address the issues of unstable waterproofing and poor durability caused by the easy detachment of the surface coating in existing technologies. Instead of relying on a surface coating, the mortar inherently possesses hydrophobic properties through the incorporation of modified materials. This performance is more stable and reliable over long-term use, effectively avoiding the risks of increased maintenance costs and waterproofing failure associated with surface coating issues. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Shown are SEM images of the micromorphology of fly ash before and after modification in Example 1; (left) SEM image of the micromorphology of ordinary fly ash (before modification); (right) SEM image of the micromorphology of L7-1h modified fly ash.

[0036] Figure 2 Shown are the water droplet / ice crystal morphologies on the surface of fly ash powder wet-modified with aluminate coupling agent in Example 1; (left) 3% NaCl solution morphology, (right) ice bead morphology.

[0037] Figure 3 Shown are the water droplet morphologies on the surface of fly ash powder wet-modified with aluminate coupling agent in Example 1 before and after standing for 1 hour; (left) before standing, (right) after standing.

[0038] Figure 4 Shown is the surface contact angle of fly ash powder wet-modified with aluminate coupling agent in Example 1.

[0039] Figure 5 Shown is the surface contact angle of the aeolian sand mortar containing fly ash modified with aluminate coupling agent in Example 2.

[0040] Figure 6 Shown are the water droplet / ice crystal morphologies on the surface of the fly ash and aeolian sand mortar modified with an internal aluminate coupling agent in Example 2; (left) water droplet morphology, (right) ice bead morphology.

[0041] Figure 7 The graph shows the cumulative water absorption of aeolian sand mortar containing fly ash modified with aluminate coupling agent in Example 2.

[0042] Figure 8 The graph shows the cumulative water absorption of the hydrophobic aeolian sand mortar containing fly ash modified with an aluminate coupling agent under the condition of a weight ratio of modified fly ash to cement of 4:6 in Example 2.

[0043] Figure 9 Figure 2 is the XRD pattern of fly ash before and after modification with aluminate coupling agent.

[0044] Figure 10 FT-IR spectra of fly ash before and after modification with aluminate coupling agent. DETAILED DESCRIPTION

[0045] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0046] Example 1

[0047] The preparation process of super-hydrophobic modified fly ash comprises the following steps:

[0048] 1. Raw material preparation:

[0049] 1.1 Modified fly ash: Weigh the following components in percentage by mass:

[0050] Aluminate coupling agent: 1g, 3g, 5g, 7g gradient addition;

[0051] Analytical pure anhydrous ethanol: The dosage is 3 to 5 times the mass of the aluminate coupling agent;

[0052] Original fly ash: 100g / batch;

[0053] 2. Modified fly ash preparation process

[0054] 2.1 Add aluminate coupling agent and anhydrous ethanol in a mass ratio of 1:4 into a container with a stirring and heating device, stir at 1000r / min, heat to 60℃, stir at constant temperature for 20 minutes, and cool to form a transparent solution.

[0055] 2.2 Transfer the transparent solution obtained in step 2.1 into the reactor, add 100g fly ash and 300mL water, adjust the stirring rate to 1500r / min, and continue stirring for 0.5 or 1h to form a modified fly ash slurry.

[0056] 2.3 Transfer the modified fly ash slurry to a vacuum drying oven, set the drying temperature to 120±5℃, dry for 1 hour, and cool and store to obtain modified fly ash L7-0.5h, L7-1h, L5-0.5h, L5-1h, L3-0.5h, L3-1h, L1-0.5h, and L1-1h.

[0057] Example 2

[0058] The hydrophobic aeolian sand mortar forming process comprises the following steps:

[0059] 1. Raw material preparation:

[0060] 1.1 Mortar base material

[0061] Modified fly ash: Modified fly ash of various specifications was obtained in Example 1;

[0062] Cement: P·O 42.5R type ordinary Portland cement;

[0063] Aeolian sand: particle size range is 0.06-0.24mm;

[0064] Mixing water: tap water (pH = 6.5 ~ 7.5);

[0065] 2. Hydrophobic aeolian sand mortar forming process

[0066] 2.1 Ingredients mixing: Weigh the following components according to mass ratio:

[0067] Modified fly ash 10-40g;

[0068] Cement 60-90g;

[0069] 330g of aeolian sand;

[0070] 50g water;

[0071] Among them, the weight ratio of modified fly ash to cement is 4:6, 1:9, 2:8, and 3:7.

[0072] 2.2 Dry mixing treatment:

[0073] a. Put cement and aeolian sand into a planetary mixer (speed 300±10r / min) and premix for 5 minutes;

[0074] b. Add modified fly ash and continue dry mixing for 30 minutes.

[0075] 2.3 Wet mixing and molding:

[0076] Slowly add water, increase the speed to 400±10r / min, and wet mix until a homogeneous slurry is formed; inject the slurry into the mold and vibrate for 30-90 seconds until it is formed, use a vibrating table to expel bubbles, and use a scraper to level the surface.

[0077] 2.4 Standard maintenance

[0078] The mold was transferred to a standard curing room and cured for 7 days at a temperature of 20±5°C and a relative humidity of 90±5% to obtain hydrophobic aeolian sand mortar specimens L7-0.5h4:6, L7-1h4:6, L5-0.5h4:6, L5-1h4:6, L3-0.5h4:6, L3-1h4:6, L1-0.5h4:6, L1-1h4:6, L7-1h1:9, L7-1h2:8, and L7-1h3:7.

[0079] control group

[0080] The ordinary aeolian sand mortar forming process includes the following steps:

[0081] 1. Raw material preparation:

[0082] 1.1 Mortar base material

[0083] Ordinary fly ash (i.e., the content of aluminate coupling agent is 0%);

[0084] Cement: P·O 42.5R type ordinary Portland cement;

[0085] Aeolian sand: particle size range is 0.15-0.5 mm;

[0086] Mixing water: tap water (pH = 6.5 ~ 7.5);

[0087] 2. Aeolian sand mortar forming process

[0088] 2.1 Ingredients mixing: Weigh the following components according to mass ratio:

[0089] Ordinary fly ash 10-40g;

[0090] Cement 60-90g;

[0091] 330g of aeolian sand;

[0092] 50g water;

[0093] Among them, the weight ratio of ordinary fly ash to cement is 1:9, 2:8, 3:7, and 4:6.

[0094] 2.2 Dry mixing treatment:

[0095] a. Put cement and aeolian sand into a planetary mixer (speed 300±10r / min) and premix for 5 minutes;

[0096] b. Add ordinary fly ash and continue dry mixing for 30 minutes.

[0097] 2.3 Wet mixing and molding:

[0098] Slowly add water, increase the speed to 400±10r / min, and wet mix until a homogeneous slurry is formed; inject the slurry into the mold and vibrate for 30-90 seconds until it is formed, use a vibrating table to expel bubbles, and use a scraper to level the surface.

[0099] 2.4 Standard maintenance

[0100] The mold was transferred to a standard curing room and cured for 7 days at a temperature of 20±5°C and a relative humidity of 90±5% to obtain aeolian sand mortar test block control groups of 1:9, 2:8, 3:7, and 4:6.

[0101] Performance testing and characterization:

[0102] 1. Performance testing and characterization of modified fly ash

[0103] 1.1 SEM images of modified fly ash microstructure Figure 1 shown.

[0104] Ordinary fly ash: Surface morphology: Original fly ash particles are spherical, with a relatively smooth surface, only a few scattered attachments or tiny protrusions, and a relatively regular overall structure. Particle state: Particles have clear outlines, no obvious fragmentation or complex pore structure, reflecting their original physical state without modification.

[0105] L7-1h modified fly ash: The particles still maintain a spherical shape, but the surface roughness increases, and more uneven microstructures appear, which is caused by the adhesion of substances and the reaction of the surface during the modification process.

[0106] 1.2 Modified fly ash wettability test:

[0107] a. Contact angle: The contact angle of the fly ash powder modified by wet method with aluminate coupling agent in Example 1 was tested. Using a video optical contact angle meter, 5 μL of deionized water was dropped on the surface of the fly ash powder modified by wet method with aluminate coupling agent. The measured contact angle was 150°, as shown in Table 1 and Figure 4 shown.

[0108] Table 1

[0109] Modified fly ash L7-0.5h L7-1h L5-0.5h L5-1h L3-0.5h L3-1h L1-0.5h L1-1h Contact angle (°) 150.13 150.51 150.72 150.19 145.66 147.14 134.24 140.74

[0110] b. Rolling angle: Adjust the angular velocity of the tilting platform to 1° / s and record the angle of the water droplet as it rolls down. The rolling angle should be less than 5°.

[0111] c. The surface water droplet / ice crystal morphology of fly ash powder modified by aluminate coupling agent wet method is as follows Figure 2 shown. Figure 2 It shows that the ice crystals on the surface of the modified mortar are discrete spherical (diameter ≤ 2 mm), and the adhesion is reduced by 87%.

[0112] d. The morphology of water droplets on the surface of fly ash modified by aluminate coupling agent wet method before and after standing for 1 hour is as follows Figure 3 shown. Figure 3 It shows that the hydrophobic performance is long-lasting and stable.

[0113] e. Figure 9-10 Shown are the XRD patterns and FT-IR patterns of fly ash before and after modification with aluminate coupling agent. Figure 9 and Figure 10 It shows that the XRD spectrum ( Figure 9 ) shows that the characteristic peak shift and intensity change of the modified crystal structure is reconstructed; FT-IR spectrum ( Figure 10 ) The stretching vibration peaks of Si-O-Al and Al-O-Al bonds appear. These changes indicate that the alkoxy groups in the aluminate coupling agent react with Si-OH and Al-OH on the fly ash surface to form Si-O-Al and Al-O-Al covalent bonds. The chemical equations are as follows:

[0114] Al(OC 12 H 25 )3+3Si-OH→(Si-O-Al)(OC 12 H 25 )2+2C 12 H 25 OH.

[0115] 2. Performance testing and characterization of hydrophobic aeolian sand mortar

[0116] 2.1 Surface wettability test of hydrophobic aeolian sand mortar

[0117] a. Surface contact angle: Using a video optical contact angle meter, 5 μL of deionized water was dropped on the surface of aerosol sand mortar specimens containing fly ash modified by wet method with aluminate coupling agent. The measured contact angle was 140° ( Figure 5 Show).

[0118] b. The morphology of water droplets / ice crystals on the surface of aeolian sand mortar with fly ash modified by aluminate coupling agent is as follows: Figure 6 shown.

[0119] 2.2 Water absorption test of hydrophobic aeolian sand mortar:

[0120] The test piece obtained in Example 2 was dried to constant weight and immersed in a water tank. The cumulative water absorption rate was recorded for 7 days and was ≤1.5% (the water absorption rate of the control group was ≥5.6%).

[0121] The water absorption rate variation trend curves of the test blocks prepared in Example 2 are presented in Figure 7 and Figure 8 .

[0122] exist Figure 7 In this experiment, the aluminate coupling agent content was kept constant, and only the weight ratio of modified fly ash (using ordinary fly ash as a control) to cement was adjusted. The experimental results showed that as the proportion of modified fly ash in the mixture gradually increased, the water absorption rate of the hydrophobic aeolian sand mortar specimens containing fly ash modified with the aluminate coupling agent showed a significant downward trend.

[0123] Figure 8The results show that while the weight ratio of modified fly ash (the control group still used ordinary fly ash) to cement was fixed at 4:6, the content of aluminate coupling agent was varied and compared with the control group without the addition of aluminate coupling agent. The results show that the water absorption rate of the hydrophobic aeolian sand mortar specimens with fly ash modified with aluminate coupling agent was also significantly reduced.

[0124] comprehensive Figure 7 and Figure 8 Experimental data indicates that when the aluminate coupling agent dosage ranges from 5% to 7%, the cumulative water absorption of fly ash-hydrophobic aeolian sand mortar specimens containing this modifier significantly decreases. This phenomenon strongly demonstrates that the modified fly ash effectively blocks pores in the mortar system and forms a hydrophobic barrier on the pore surface, significantly improving the mortar's hydrophobic properties.

[0125] 2.3 Mechanical properties test of hydrophobic aeolian sand mortar:

[0126] The compressive strength at 28 days was ≥40MPa (the average value of the control group was 22.5MPa), with an increase of ≥75%.

[0127] The above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A mortar containing fly ash modified with an aluminate coupling agent, characterized in that: The method comprises the following raw materials in the following mass ratios: 10 to 40 g of modified fly ash; Cement 60-90g; 300-350g of aeolian sand; 45-55g water; The modified fly ash is prepared by wet modification with an aluminate coupling agent, and the preparation method comprises the following steps: An aluminate coupling agent and anhydrous ethanol are mixed in a mass ratio of 1: (3-5), heated, and stirred for the first time to form a transparent solvent; the transparent solvent and fly ash are added into water together, stirred for the second time to form a slurry, and dried to obtain modified fly ash.

2. The aeolian sand mortar containing fly ash modified with an aluminate coupling agent according to claim 1, characterized in that: The heating temperature is 50-70° C., and the first stirring rate is 800-1200 r / min.

3. The aeolian sand mortar containing fly ash modified with an aluminate coupling agent according to claim 1, characterized in that: The solid-liquid ratio of fly ash to water is g:mL=1:(2-4); the mass ratio of aluminate coupling agent to fly ash is (1-7):

100.

4. The aeolian sand mortar containing fly ash modified with an aluminate coupling agent according to claim 1, characterized in that: The second stirring rate is 1200-1800 r / min, and the second stirring time is 30-60 minutes.

5. The aeolian sand mortar containing fly ash modified with an aluminate coupling agent according to claim 1, characterized in that: The drying temperature is 110-130°C, and the drying time is 0.5-2h.

6. The method for preparing aeolian sand mortar containing fly ash modified with an aluminate coupling agent according to claim 1, characterized in that: The particle size of the aeolian sand ranges from 0.06 to 0.26 mm.

7. The aeolian sand mortar containing fly ash modified with an aluminate coupling agent according to claim 1, characterized in that: The cement is P·O 42.5R type ordinary Portland cement.

8. A method for preparing aeolian sand mortar containing fly ash modified with an aluminate coupling agent as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Weigh the modified fly ash, cement and aeolian sand according to the weight ratio and mix them evenly; (2) adding water and wet mixing until a homogeneous slurry is formed; (3) The slurry was injected into the mold and vibrated to form the slurry, and then cured for 7 days at a temperature of 20±5°C and a relative humidity of 90±5% to obtain a hydrophobic aeolian sand mortar specimen.

9. The method for preparing aeolian sand mortar containing fly ash modified with an aluminate coupling agent according to claim 8, characterized in that: The dry mixing time is 20 to 40 minutes, the wet mixing time is 5 to 15 minutes; the vibration time is 30 to 90 seconds.

10. The method for preparing aeolian sand mortar containing fly ash modified with an aluminate coupling agent according to claim 8, characterized in that: The performance parameters of the hydrophobic aeolian sand mortar specimens include: contact angle can reach 140°; cumulative water absorption rate ≤1.5%, 28-day compressive strength ≥40MPa.

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