Emulsified paraffin-based concrete curing agent as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of functional building materials, and particularly relates to an emulsified paraffin-based concrete curing agent as well as a preparation method and application thereof. The curing agent comprises the following components in percentage by weight: 65.0 to 75.0 percent of emulsified paraffin, 5.0 percent of a polar solubilizer, 0.5 percent of a thickening agent, 0.8 to 1.0 percent of a water-retaining agent, 0.3 percent of modified nano silicon dioxide, 0.2 percent of trimethyl benzyl ammonium chloride and the balance of water. The concrete curing agent optimized through a nano-composite technology and a multi-component synergistic effect can be suitable for concrete structure curing in an extremely high-temperature dry environment.

Description

Technical Field

[0001] The invention belongs to the technical field of functional building materials, and in particular relates to an emulsified paraffin-based concrete curing agent and a preparation method and application thereof. Background Art

[0002] Concrete is a man-made stone made of cement, fine aggregate (sand), coarse aggregate (crushed stone) and water. It is the most important component of a building. The quality of concrete determines the quality of the building. In the actual construction of concrete, concrete maintenance is a very important link.

[0003] When existing concrete is cured in a high temperature and dry environment, it is easy to cause shrinkage cracks and insufficient strength due to rapid evaporation of water. If traditional concrete curing methods such as sprinkling or covering with plastic film are used, it is difficult to effectively inhibit early shrinkage cracking and strength loss of concrete due to problems such as rapid evaporation rate and uneven coverage.

[0004] Existing emulsified paraffin-based curing agents have become the preferred alternative to traditional curing processes due to their hydrophobic film-forming properties, which can reduce water evaporation through physical barriers. However, single emulsified paraffin coatings still have problems such as insufficient water retention and durability, high film brittleness, and easy cracking. Excessive use will hinder the late hydration reaction of concrete and reduce the mechanical properties of concrete.

[0005] Therefore, there is an urgent need for an emulsified paraffin-based concrete curing agent and a preparation method and application thereof to solve the above-mentioned problems. Summary of the invention

[0006] In order to overcome the defects in the above-mentioned prior art, the present invention provides an emulsified paraffin-based concrete curing agent and a preparation method and application thereof. The present invention prepares a concrete curing agent optimized by nanocomposite technology and multi-component synergistic effect, which can be applied to the curing of concrete structures in extremely high temperature and dry environments.

[0007] To achieve one of the above purposes, the present invention adopts the following technical solution: An emulsified paraffin-based concrete curing agent comprises 65.0-75.0 wt% of emulsified paraffin, 5.0 wt% of a polar solubilizer, 0.5 wt% of a thickener, 0.8-1.0 wt% of a water retaining agent, 0.3 wt% of modified nano silicon dioxide and 0.2 wt% of trimethylbenzyl ammonium chloride, and the balance is water.

[0008] Preferably, the modified nano-silica is prepared by modifying nano-silica with a silane coupling agent, and the particle size of the nano-silica is 20-50 nm.

[0009] Preferably, the modified nano-silica is prepared by modifying nano-silica with γ-aminopropyltriethoxysilane, and the grafting rate is ≥15%, ensuring that the silane coupling agent forms a complete coating layer on the surface of the silica nanoparticles to enhance the interface compatibility. If the grafting rate is insufficient, the nanoparticles are prone to agglomeration to form stress concentration points, resulting in a decrease in the elongation at break of the coating film; the mass ratio of nano-silica to γ-aminopropyltriethoxysilane is 5:1.

[0010] Preferably, the solid content of the emulsified paraffin is 40±1%, which can balance the film-forming continuity and construction fluidity and ensure the effective formation of the hydrophobic barrier. When the solid content is too high, the viscosity of the emulsion is too high, resulting in a decrease in coating uniformity; when the solid content is too low, the film thickness is insufficient, which seriously affects the water permeability.

[0011] Preferably, the water retaining agent is sodium polyacrylate, and the molecular weight of sodium polyacrylate is 2000-5000. If the molecular weight is less than 2000, the network crosslinking density is insufficient, resulting in a decrease in water holding rate. If the molecular weight is greater than 5000, the dissolution rate is reduced, which easily leads to insufficient dissolution. The water absorption is ≥500g / g, and the unit mass of the water retaining agent can absorb 500 times its own weight of water to form a continuous water absorption network. If the water absorption is less than 500g / g, it cannot meet the requirements of a high temperature dry environment.

[0012] Preferably, the polar solubilizer is butanediol; and the thickener is carboxymethyl cellulose.

[0013] Preferably, the purity of trimethylbenzyl ammonium chloride is ≥98%, ensuring the proportion of effective ingredients and avoiding impurities (such as inorganic salts, oligomers, etc.) interfering with the interface reaction; the cation exchange capacity of trimethylbenzyl ammonium chloride is ≥3.5mmol / g, which can provide sufficient quaternary ammonium cations to form an electrostatic repulsion stabilization layer with the surface of nano-silica (positively charged after modification); the high exchange capacity maintains the zeta potential at +25 to +35mV, inhibiting particle agglomeration; the solubility of trimethylbenzyl ammonium chloride is ≥50g / L (25°C), ensuring that the surfactant is fully dissolved in the aqueous phase to form a monomolecular adsorption layer; the benzyl para position in the molecular structure of trimethylbenzyl ammonium chloride is not substituted.

[0014] To achieve the second purpose above, the present invention provides a method for preparing an emulsified paraffin-based concrete curing agent, and the specific steps are as follows: S1. Pre-dispersion treatment: Mix the modified nano-silicon dioxide and trimethylbenzyl ammonium chloride in proportion, add deionized water for ultrasonic dispersion to form a mixed solution; S2, emulsion blending: under high-speed stirring, add emulsified paraffin, polar solubilizer and thickener to an empty container in sequence, and then homogenize for 30 minutes; the emulsified paraffin added first is the main film-forming substance of the system, which can first form a continuous emulsion phase to provide a dispersion medium for subsequent components; polar solubilizers such as butanediol need to be fully mixed with the emulsion before the thickener is added, and reduce the interfacial tension through hydrogen bonding to avoid agglomeration when the subsequent thickener is added; finally, the thickener is added to prevent premature thickening from causing dispersion difficulties, and at the same time, the entanglement of its polymer chains is used to stabilize the emulsion structure. If they are added together or in a disordered order, the stability of the emulsified paraffin emulsion will be reduced, resulting in uneven dispersion of the components and affecting the uniformity of the coating; S3, network construction: after homogenization, add water retaining agent and stir to form an ion cross-linking network; S4, nanocomposite: introduce the pre-dispersed mixed solution into the ion cross-linked network and then homogenize under high pressure for 3 times; S5. Finished product preparation: After the homogenization in step S4 is completed, fine grinding is performed to form a stable emulsion with a particle size distribution of ≤10 μm, which is the curing agent.

[0015] Preferably, the modification steps of the modified nano-silica are: mixing the nano-silica with γ-aminopropyltriethoxysilane, and adjusting the pH of the system to 4.5-5.0 with glacial acetic acid; placing the mixed solution in a 70°C constant temperature water bath, and mechanically stirring the reaction at a speed of 500r / min for 3 hours to obtain modified nano-silica.

[0016] Preferably, in step S1, the dispersion time is 15 minutes and the dispersion power is 400 W; in step S3, the stirring speed is 800 r / min and the stirring time is 20 minutes; in step S4, high-pressure homogenization is performed using a 100 MPa high-pressure homogenizer to ensure that the nanoparticles are evenly embedded in the emulsion system.

[0017] To achieve the third purpose above, the present invention provides an application of an emulsified paraffin-based concrete curing agent, wherein the curing agent is coated on the surface of a concrete test block, the coating amount is 0.3-0.5L / m², the ambient temperature is ≥35°C, and the relative humidity is ≤40%.

[0018] The advantages of the present invention are: (1) The concrete curing agent optimized by the nanocomposite technology and the synergistic effect of multiple components of the present invention can be applied to the curing of concrete structures in extremely high temperature and dry environments; wherein, sodium polyacrylate (PAAS) and carboxymethyl cellulose (CMC) form a double network structure, and then a "core-shell" multi-level network structure constructed by introducing modified nano-silica and trimethylbenzyl ammonium chloride is introduced; the double network structure is nested in the "core-shell" multi-level network structure to form a nano-scale water absorption channel; trimethylbenzyl ammonium chloride forms a 0.5-1 nm thick interface layer on the surface of the nanoparticles; the interface layer reduces the dispersion index through electrostatic repulsion and hydrophobic interaction, thereby ensuring uniform distribution of the nanoparticles and avoiding stress concentration; the "core-shell" multi-level network structure has the thermal stability of the nanoparticles (decomposition temperature>500°C) and the anti-thermal oxidation performance of the network structure, thereby ensuring the integrity of the coating film.

[0019] (2) In the present invention, emulsified paraffin is used to form a continuous hydrophobic film to construct a moisture barrier; butanediol is used as a polar solubilizer to promote the interfacial compatibility between the emulsion and the nanoparticles; carboxymethyl cellulose (CMC) is used as a polymer thickener to regulate the rheology of the system and delay water migration; sodium polyacrylate (PAAS) is used as a water retaining agent to form a three-dimensional double network structure with carboxymethyl cellulose through ionic crosslinking; γ-aminopropyl triethoxysilane is used to modify the surface of nano-silica, and the silane coupling agent shrinks with the surface hydroxyl groups of nano-silica. The reaction forms a stable chemical bond grafting structure with a grafting rate of ≥15%, which strengthens the nanophase, fills the pores of the membrane structure, and improves the density and mechanical strength of the coating. In addition, trimethylbenzyl ammonium chloride (BTAC) as a cationic surfactant optimizes the dispersibility of nano-silica through electrostatic repulsion and steric hindrance effects, and improves its uniform distribution in the emulsion. At the same time, the quaternary ammonium group of trimethylbenzyl ammonium chloride can combine with water through hydrogen bonds, assisting the double network structure formed by sodium polyacrylate and carboxymethyl cellulose, delaying water release and improving water holding rate.

[0020] (3) When the curing agent prepared by the present invention is used for concrete curing, the surface-modified nano-silica is embedded in the paraffin film through the "pinning effect" to fill the pores of the paraffin film, thereby reducing the porosity of the coating by 42% and increasing the elastic modulus by 35% (SEM / AFM characterization). The surface modification enhances the interfacial compatibility between the nano-silica particles and the emulsion, reduces the dispersion index (PDI), and improves the water retention performance of the concrete, so that it can adapt to high temperature and dry environments. Molecular-level water retention: Sodium polyacrylate and carboxymethyl cellulose form a double network structure. Sodium polyacrylate provides rapid water absorption sites, and carboxymethyl cellulose delays water release through polymer chain entanglement, further improving water retention, achieving a 72-hour water retention rate of 68.2%.

[0021] Interface optimization: Butanediol and trimethylbenzyl ammonium chloride work synergistically to reduce the dispersion index (PDI) of nano-silica particles and significantly improve the emulsion stability.

[0022] (4) In the present invention, a "nano-enhanced skeleton" is constructed by introducing modified nano-silica, and a cationic surfactant of trimethylbenzyl ammonium chloride is combined to form a four-level synergistic system of "solubilization-thickening-cross-linking-enhancement". This system exhibits excellent water retention stability, film flexibility and mechanical enhancement effects under extreme environments, breaking through the performance limits of traditional emulsified paraffin curing agents. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0024] Example 1 S1. Modification treatment: nano-silica and γ-aminopropyltriethoxysilane are mixed in a mass ratio of 5:1, the particle size of the nano-silica is 20nm, and the pH of the system is adjusted to 5.0 with glacial acetic acid; the mixed solution is then placed in a constant temperature water bath at 70°C, mechanically stirred at a speed of 500r / min for 3 hours, and the grafting rate is controlled to be ≥15% to obtain modified nano-silica; S2 pre-dispersion treatment: Take 0.3wt% of modified nano-silica and 0.2wt% of trimethylbenzyl ammonium chloride, add 25wt% of deionized water and ultrasonically disperse for 15 minutes (power 400W) to form a stable dispersion; S3. Emulsion blending: Under high-speed stirring at 1200r / min, 68.2wt% of emulsified paraffin (solid content 40%), 5.0wt% of butanediol, and 0.5wt% of carboxymethyl cellulose were added successively and homogenized for 30 minutes; S4. Network construction: Slowly add 0.8 wt% sodium polyacrylate (molecular weight 3400) to the homogenized mixture, maintain the speed at 800 r / min for 20 minutes to form an ion cross-linked network; S5. Nanocomposite: The dispersion in step S2 was introduced and treated three times with a high-pressure homogenizer (100 MPa) to ensure that the nanoparticles were evenly embedded in the emulsion system; S6. Preparation of finished product: The final product is finely ground by a colloid mill (2900r / min) to form a stable emulsion with a particle size distribution of ≤10μm, namely, curing agent 1.

[0025] Example 2 S1. Modification treatment: nano-silica and γ-aminopropyltriethoxysilane are mixed in a mass ratio of 5:1, the particle size of the nano-silica is 26nm, and the pH of the system is adjusted to 5.0 with glacial acetic acid; the mixed solution is then placed in a constant temperature water bath at 70°C, mechanically stirred at a speed of 500r / min for 3 hours, and the grafting rate is controlled to be ≥15% to obtain modified nano-silica; S2. Pre-dispersion treatment: 0.3wt% of modified nano-silica was mixed with 0.2wt% of trimethylbenzyl ammonium chloride, and 25wt% of deionized water was added for ultrasonic dispersion for 15 minutes (power 400W) to form a stable dispersion; S3. Emulsion blending: Under high-speed stirring (1200r / min), 68wt% of emulsified paraffin (solid content 40%), 5.0wt% of butanediol, and 0.5wt% of carboxymethyl cellulose were added in sequence and homogenized for 30 minutes; S4. Network construction: 1.0 wt% sodium polyacrylate (molecular weight 3400) was slowly added to the homogenized mixture, and the reaction was maintained at a speed of 800 r / min for 20 minutes to form an ion cross-linked network; S5. Nanocomposite: The dispersion in step S2 was introduced and treated three times with a high-pressure homogenizer (100 MPa) to ensure that the nanoparticles were evenly embedded in the emulsion system; S6. Preparation of finished product: The final product is finely ground by a colloid mill (2900r / min) to form a stable emulsion with a particle size distribution of ≤10μm, namely, curing agent 2.

[0026] Example 3 S1. Modification treatment: nano-silica and γ-aminopropyltriethoxysilane are mixed in a mass ratio of 5:1, the particle size of the nano-silica is 34nm, and the pH of the system is adjusted to 5.0 with glacial acetic acid; the mixed solution is then placed in a constant temperature water bath at 70°C, mechanically stirred at a speed of 500r / min for 3 hours, and the grafting rate is controlled to be ≥15% to obtain modified nano-silica; S2 pre-dispersion treatment: 0.3wt% of modified nano-silica was mixed with 0.2wt% of trimethylbenzyl ammonium chloride, and 28.2wt% of deionized water was added and ultrasonically dispersed for 15 minutes (power 400W) to form a stable dispersion; S3. Emulsion blending: Under high-speed stirring (1200r / min), 65wt% of emulsified paraffin (solid content 40%), 5.0wt% of butanediol, and 0.5wt% of carboxymethyl cellulose were added in sequence and homogenized for 30 minutes; S4. Network construction: Slowly add 1.0wt% sodium polyacrylate (molecular weight 2000) to the homogenized mixture, maintain the speed at 800r / min for 20 minutes to form an ion cross-linked network; S5. Nanocomposite: The dispersion in step S2 was introduced and treated three times with a high-pressure homogenizer (100 MPa) to ensure that the nanoparticles were evenly embedded in the emulsion system; S6. Preparation of finished product: The final product is finely ground by a colloid mill (2900r / min) to form a stable emulsion with a particle size distribution of ≤10μm, namely curing agent 3.

[0027] Example 4 S1. Modification treatment: nano-silica and γ-aminopropyltriethoxysilane are mixed in a mass ratio of 5:1, the particle size of the nano-silica is 50nm, and the pH of the system is adjusted to 5.0 with glacial acetic acid; the mixed solution is then placed in a constant temperature water bath at 70°C, mechanically stirred at a speed of 500r / min for 3 hours, and the grafting rate is controlled to be ≥15% to obtain modified nano-silica; S2 pre-dispersion treatment: 0.3wt% of modified nano-silica was mixed with 0.2wt% of trimethylbenzyl ammonium chloride, and 18.2wt% of deionized water was added for ultrasonic dispersion for 15 minutes (power 400W) to form a stable dispersion; S3. Emulsion blending: Under high-speed stirring (1200r / min), 75wt% of emulsified paraffin (solid content 40%), 5.0wt% of butanediol, and 0.5wt% of carboxymethyl cellulose were added in sequence and homogenized for 30 minutes; S4. Network construction: Slowly add 1.0wt% sodium polyacrylate (molecular weight 5000) to the homogenized mixture, maintain the speed at 800r / min for 20 minutes to form an ion cross-linked network; S5. Nanocomposite: The dispersion in step S2 was introduced and treated three times with a high-pressure homogenizer (100 MPa) to ensure that the nanoparticles were evenly embedded in the emulsion system; S6. Preparation of finished product: The final product is finely ground by a colloid mill (2900 r / min) to form a stable emulsion with a particle size distribution of ≤10 μm, namely, curing agent 4.

[0028] Comparative Example 1 An organic concrete curing agent produced by Zhuonengda Company was selected as curing agent 5.

[0029] The curing agent prepared in Examples 1-2 and Comparative Example 1 was applied to concrete. The specific steps are: Apply the curing agent evenly on the surface of C30 concrete test block, with a coating amount of 0.4L / m 2 The test block was placed in an oven at 80°C for 72 hours, and the internal humidity, number and width of cracks, and 28-day compressive strength of the test block were monitored. The specific results are shown in Table 1 below: Table 1 ; The blank control group in Table 1 is a concrete control group that is not coated with a curing agent. As can be seen from Table 1 above, the experimental results show that the internal humidity of the test block of Comparative Example 1 is 58.9%, the number of cracks is 3, and the 28-day compressive strength reaches 34.5 MPa, while Examples 1-2 are better than Comparative Example 1 and the blank control group, indicating that the curing agent of the present invention has excellent properties such as ultra-long water retention durability and not easy to crack.

[0030] The curing agents of Example 1 and Comparative Example 1 were applied to concrete to perform a coating performance test, and the test steps were as follows: 1. Apply the curing agent evenly on the surface of C30 concrete test block, with a coating amount of 0.4L / m 2 , and then place the concrete test block at 25°C for 24 hours for curing. After curing, the concrete test block is cut into 1 cm × 1 cm test pieces; 2. Use scanning electron microscopy (SEM) to observe the surface morphology and calculate the porosity (pore area / total surface area × 100%); 3. Use atomic force microscopy (AFM) to measure the elastic modulus in contact mode and take the average value of 5 different areas. The specific results are shown in Table 2 below: Table 2 ; It can be seen from Table 2 that after the curing agent prepared in Example 1 is applied to concrete, the porosity of the concrete is reduced by 42.16% compared with Comparative Example 1, and the elastic modulus is increased by 34.78%.

[0031] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An emulsified paraffin-based concrete curing agent, characterized in that: The curing agent comprises 65.0-75.0wt% of emulsified paraffin, 5.0wt% of polar solubilizer, 0.5wt% of thickener, 0.8-1.0wt% of water retaining agent, 0.3wt% of modified nano silicon dioxide and 0.2wt% of trimethylbenzyl ammonium chloride, and the balance is water.

2. The emulsified paraffin-based concrete curing agent according to claim 1, characterized in that: The modified nano silicon dioxide is prepared by modifying nano silicon dioxide with a silane coupling agent, and the particle size of the nano silicon dioxide is 20-50 nm.

3. The emulsified paraffin-based concrete curing agent according to claim 1, characterized in that: The modified nano silicon dioxide is prepared by modifying nano silicon dioxide with γ-aminopropyltriethoxysilane, and the grafting rate is ≥15%; the mass ratio of the nano silicon dioxide to γ-aminopropyltriethoxysilane is 5:

1.

4. The emulsified paraffin-based concrete curing agent according to claim 1, characterized in that: The solid content of the emulsified paraffin is 40±1%.

5. The emulsified paraffin-based concrete curing agent according to claim 1, characterized in that: The water retaining agent is sodium polyacrylate, the molecular weight of sodium polyacrylate is 2000-5000, and the water absorption is ≥500g / g.

6. The emulsified paraffin-based concrete curing agent according to claim 1, characterized in that: The polar solubilizer is butanediol; the thickener is carboxymethyl cellulose; the purity of trimethylbenzyl ammonium chloride is ≥98%, and its cation exchange capacity is ≥3.5mmol / g.

7. A method for preparing the emulsified paraffin-based concrete curing agent according to any one of claims 1 to 6, characterized in that: The specific steps are as follows: S1, pre-dispersion treatment: mixing the modified nano-silicon dioxide with trimethylbenzyl ammonium chloride, adding deionized water for ultrasonic dispersion to form a mixed solution for standby use; S2, emulsion blending: under high-speed stirring, add emulsified paraffin, polar solubilizer and thickener to an empty container in sequence, and then homogenize for 30 minutes; S3, network construction: after homogenization, add water retaining agent and stir to form an ion cross-linking network; S4, nanocomposite: introduce the pre-dispersed mixed solution into the ion cross-linked network and then homogenize under high pressure for 3 times; S5. Finished product preparation: After the homogenization in step S4 is completed, fine grinding is performed to form a curing agent with a particle size distribution of ≤10 μm.

8. The method for preparing an emulsified paraffin-based concrete curing agent according to claim 7, characterized in that: The modification steps of the modified nano-silica are: mixing the nano-silica with γ-aminopropyltriethoxysilane, and adjusting the pH of the system to 4.5-5.0 with glacial acetic acid; placing the mixed solution in a 70° C. constant temperature water bath, and mechanically stirring the reaction for 3 hours to obtain the modified nano-silica.

9. The method for preparing an emulsified paraffin-based concrete curing agent according to claim 7, characterized in that: In step S1, the dispersion time is 15 minutes and the dispersion power is 400W; in step S3, the stirring speed is 800r / min and the stirring time is 20 minutes; in step S4, the high-pressure homogenization is carried out by a 100MPa high-pressure homogenizer.

10. An application of the emulsified paraffin-based concrete curing agent according to any one of claims 1 to 6, characterized in that: Apply the curing agent on the surface of the concrete test block at a coating amount of 0.3-0.5L / m². The ambient temperature is ≥35℃ and the relative humidity is ≤40%.