Method for improving tensile bonding strength of extruded polystyrene board and mortar

Abstract

The invention relates to the technical field of building materials, in particular to a method for improving tensile bonding strength of an extruded polystyrene board and mortar, which comprises the following steps: S1, design of a mortar formula: the mortar formula adopts a two-component mortar formula, the two-component mortar formula comprises a dry powder group and a liquid group, the dry powder group and the liquid group are mixed according to a certain proportion to form uniform slurry. According to the invention, a double-component mortar formula is adopted, all the components have a synergistic effect, so that the mortar and the XPS board are firmly bonded, the construction steps are specified in detail, clear requirements are provided for links such as base surface cleaning, mortar coating thickness control, XPS board bonding and curing maintenance, and the construction quality can be effectively ensured; the XPS plate is prevented from falling off, the heat preservation effect of an outer wall heat preservation system is guaranteed, the energy consumption cost of a building is reduced, the threat of the falling-off plate to pedestrian safety is eliminated, and remarkable economic benefits and social benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and specifically to a method for improving the tensile bond strength between extruded polystyrene board and mortar. Background Technology

[0002] In building exterior wall insulation projects, extruded polystyrene (XPS) boards are widely used due to their excellent thermal insulation performance, low water absorption, and good compressive strength. However, the smooth surface and strong hydrophobicity of XPS boards make bonding with mortar a major challenge.

[0003] In practical applications, traditional single-component mortar, when bonded to XPS boards, suffers from poor flexibility and insufficient durability due to the limitations of cement-based materials. This results in the tensile bond strength between the two materials failing to meet the requirements of actual engineering projects. If the XPS boards and mortar are not firmly bonded, the XPS boards may detach over time due to environmental factors such as temperature changes, rain erosion, and wind. This not only seriously affects the insulation effect of the external wall insulation system, leading to energy waste and increased building energy costs, but also poses a threat to pedestrian safety, potentially causing serious accidents.

[0004] Therefore, how to effectively improve the tensile bond strength between XPS boards and mortar, and enhance the stability and reliability of external wall insulation systems, has become a key issue that urgently needs to be addressed in the field of building materials. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides a method for improving the tensile bond strength between extruded polystyrene (XPS) boards and mortar. This method effectively solves the problems of poor flexibility and insufficient durability in existing single-component mortars when bonding with XPS boards, which are limited by the construction characteristics of cement-based materials.

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

[0007] This invention provides a method for improving the tensile bond strength between extruded polystyrene board and mortar, the method comprising the following steps:

[0008] S1, Mortar formulation design, the mortar formulation adopts a two-component mortar formulation, the two-component mortar formulation includes a dry powder group and a liquid group, the dry powder group and the liquid group are mixed in a certain proportion to form a uniform slurry;

[0009] S2, Mortar formulation components and proportions: The dry powder group includes the following components: ordinary Portland cement 40%–60%, quartz sand 30%–50%, silica fume 2%–4%, cellulose ether 0.01%–0.02%, latex powder 1%–3%, defoamer 0.1%–0.2%, and polymer powder 0.5%–1%. The liquid group includes the following components: emulsion 20%–30%, water 70%–80%, and the mixing ratio of the dry powder group and the liquid group is 3:1.

[0010] S3, Mortar preparation steps: First, premix all components of the dry powder group evenly in a dry environment to ensure that each component is evenly dispersed. After mixing, place it in a dry place for later use. Next, mix the emulsion and water in the liquid group and stir evenly with a stirring device to form a uniform liquid mixture. Finally, mix the dry powder group and the liquid group in the above 3:1 ratio and stir mechanically for 3 to 5 minutes until there are no lumps in the mixture, forming a uniform slurry.

[0011] S4, Specific Construction Steps

[0012] S41. Before construction, the base surface must be cleaned to ensure that it is flat, dry, and free of dust, oil, and other impurities.

[0013] S42. After cleaning, use a notched trowel to evenly apply the prepared mortar to the XPS board surface. It is recommended to apply the mortar to a thickness of 1-1.5mm.

[0014] S43, after the mortar is applied, press the XPS board lightly onto the base surface and pat the XPS board gently with your hand to ensure that the mortar and the XPS board are in full contact and that they are fully bonded together.

[0015] S44. After construction is completed, the construction area should be cured and protected. During the curing period, the construction area should be protected from direct sunlight or rain.

[0016] According to the above-mentioned method for improving the tensile bond strength between extruded polystyrene board and mortar, the curing time for the construction area is at least 24 hours to ensure that the mortar is fully cured.

[0017] According to the above-mentioned method for improving the tensile bond strength between extruded polystyrene board and mortar, the type of emulsion is one of acrylic emulsion or ethylene-vinyl acetate copolymer emulsion and acrylic emulsion.

[0018] According to the above-mentioned method for improving the tensile bond strength between extruded polystyrene board and mortar, the ordinary silicate cement accounts for 50%, quartz sand accounts for 40%, silica fume accounts for 3%, cellulose ether accounts for 0.015%, latex powder accounts for 2%, defoamer accounts for 0.15%, and polymer powder accounts for 0.85%. The liquid component includes the following components: emulsion accounts for 25% and water accounts for 75%.

[0019] According to the above-mentioned method for improving the tensile bond strength between extruded polystyrene board and mortar, the ordinary silicate cement accounts for 45%, the quartz sand accounts for 45%, the silica fume accounts for 2.5%, the cellulose ether accounts for 0.01%, the latex powder accounts for 2.5%, the defoamer accounts for 0.2%, and the polymer powder accounts for 0.8%. The liquid component includes the following components: emulsion accounts for 23% and water accounts for 77%.

[0020] The technical solution provided by this invention has the following advantages compared with the known prior art:

[0021] 1. Enhanced Bond Strength: A two-component mortar formula is used. Ordinary silicate cement in the dry powder component provides basic bonding performance and strength, while quartz sand enhances structural stability, silica fume fills voids to improve density and strength, and latex powder and polymer powder enhance adhesion and wettability. The emulsion in the liquid component further enhances flexibility, bonding ability, and durability. The synergistic effect of these components ensures a strong bond between the mortar and XPS boards. In Example 1, the bond strength after immersion in water reached 0.35 MPa, and in Example 2, the initial bond strength was 0.72 MPa, effectively solving the problem of insufficient bond strength between traditional single-component mortar and XPS boards.

[0022] 2. Enhanced Flexibility and Durability: Cellulose ethers improve the water retention and workability of the mortar, latex powder enhances flexibility, and acrylic emulsions or ethylene-vinyl acetate copolymer emulsions improve the mortar's weather resistance, water resistance, and frost resistance. In the examples, after 50 freeze-thaw cycles and 1000 hours of damp heat aging treatment, the strength reduction rate was low (8% in Example 1 and 9% in Example 2), indicating that the mortar of this invention can effectively resist the influence of environmental factors, reduce the risk of cracking and peeling, and extend the service life of the external wall insulation system.

[0023] 3. Adaptable to different construction conditions: During the preparation of the mortar, the precise batching and mixing process ensures stable quality. The open time test shows that when the XPS board is pasted at an interval of 20 minutes, the bonding strength can still maintain a high proportion (92% of the initial value in Example 1 and 91% in Example 2). This indicates that the mortar has good open time performance within a certain period of time, which can meet the needs of different construction rhythms and improve construction flexibility.

[0024] 4. Ensuring construction quality and safety: The method of this invention provides detailed specifications for the construction steps, with clear requirements for everything from base surface cleaning and mortar application thickness control to XPS board bonding and curing. This effectively ensures construction quality and prevents XPS boards from falling off, thus guaranteeing the insulation effect of the external wall insulation system, reducing building energy consumption costs, and eliminating the threat to pedestrian safety posed by detached boards. It has significant economic and social benefits. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] The present invention will be further described below with reference to embodiments.

[0027] Example 1: A method for improving the tensile bond strength between extruded polystyrene board and mortar, comprising the following steps:

[0028] S1, mortar formulation design. The mortar formulation adopts a two-component mortar formulation, which includes a dry powder component and a liquid component. The dry powder component and the liquid component are mixed in a certain proportion to form a uniform slurry.

[0029] S2, Mortar formulation components and proportions: The dry powder group includes the following components: ordinary Portland cement 40%–60%, quartz sand 30%–50%, silica fume 2%–4%, cellulose ether 0.01%–0.02%, latex powder 1%–3%, defoamer 0.1%–0.2%, and polymer powder 0.5%–1%. The liquid group includes the following components: emulsion 20%–30%, water 70%–80%, and the mixing ratio of the dry powder group and the liquid group is 3:1.

[0030] Ordinary silicate cement, as the main cementing material, provides basic bonding performance and strength. Quartz sand acts as aggregate, enhancing the structural stability of the mortar. Silica fume, with its high activity, can fill the voids between cement particles, improving the density and strength of the mortar. Cellulose ether can improve the water retention and workability of the mortar. Latex powder (redispersible) enhances the flexibility and adhesion of the mortar. Defoamer is used to eliminate air bubbles generated during mixing, ensuring the uniformity of the mortar. Polymer powder (special type) can further improve the wetting and adhesion to XPS boards. Emulsion can enhance the flexibility, adhesion and durability of the mortar. Water acts as a solvent, ensuring that all components are fully mixed and reacted.

[0031] The emulsions are either acrylic emulsions or ethylene-vinyl acetate copolymer emulsions, or a combination of both. Acrylic emulsions possess excellent weather resistance, water resistance, and UV resistance. The polymer film formed after film formation is tough and elastic, exhibiting high chemical stability and maintaining stable performance under various climatic conditions. They resist the influence of environmental factors on mortar bonding performance, significantly improving the bond strength between mortar and XPS boards, enhancing mortar flexibility, and allowing it to better adapt to temperature changes causing expansion and contraction, reducing the possibility of cracking. Vinyl acetate-ethylene copolymer emulsions (VAE emulsions), on the other hand, possess good adhesion, flexibility, and water resistance, exhibiting good adhesion to various substrates. Their molecular structure contains ethylene segments, giving the emulsion good flexibility and low-temperature performance, maintaining good film-forming properties at lower temperatures. Adding VAE emulsion to mortar can improve its bond strength and flexural strength, enhance its workability, and make it easier to apply and handle. Simultaneously, it can also enhance the mortar's freeze-thaw resistance and durability, making it suitable for building insulation projects in cold regions.

[0032] S3, Mortar Preparation Steps: Using a high-precision electronic scale, accurately weigh each component according to the proportions: 50% ordinary silicate cement, 40% quartz sand, 3% silica fume, 0.015% cellulose ether, 2% latex powder (redispersible), 0.15% defoamer, and 0.85% polymer powder (special type). Add these components sequentially to a high-efficiency dry powder mixer. Set the mixer speed to 200-300 rpm and the mixing time to 10-15 minutes to ensure that each component is fully and evenly mixed and that each component is evenly distributed in the dry powder mixture. After mixing, transfer the dry powder mixture to a sealed, moisture-proof container and store it in a dry and ventilated environment for later use.

[0033] In the preparation of the liquid group, precise metering equipment is also used. 25% of the emulsion and 75% of the water are added to a container with a stirring device. The stirring device is turned on, and the stirring speed is controlled at 150-200 rpm for 5-8 minutes until the liquid group forms a homogeneous mixture without emulsion stratification or water-oil separation.

[0034] Finally, following the strict ratio of 3:1 between dry powder and liquid, slowly pour the dry powder from the moisture-proof container into the container containing the liquid. Simultaneously, start the mechanical mixing equipment, setting the mixing speed to 300-400 rpm and the mixing time to 4 minutes. During the mixing process, closely observe the state of the mortar to ensure that there are no lumps in the mixture, resulting in a uniform, fine mortar with good fluidity.

[0035] S4, Specific Construction Steps

[0036] S41. Before construction, the base surface must be cleaned to ensure that it is flat, dry, and free of dust, oil, and other impurities.

[0037] S42. After cleaning, use a notched trowel to evenly apply the prepared mortar to the XPS board surface. It is recommended to apply the mortar to a thickness of 1-1.5mm. During the application process, keep the trowel at a 45°-60° angle to the XPS board surface and apply even pressure to ensure that the application thickness is controlled at about 1.2mm, with an error of no more than ±0.2mm.

[0038] S43, after the mortar is applied, press the XPS board lightly onto the base surface and pat the XPS board gently with your hand to ensure that the mortar and the XPS board are in full contact and that they are fully bonded together.

[0039] S44. After construction is completed, the construction area must be cured and maintained. During the curing period, the construction area should be protected from direct sunlight or rain. The curing time should be at least 24 hours to ensure that the mortar is fully cured. After construction is completed, obvious warning signs should be set up nearby to prevent unauthorized personnel from touching the construction area. The construction area should be cured in a natural environment. During the curing period, a dedicated person should be assigned to observe the weather conditions regularly. In case of strong sunlight, use shade nets to cover the construction area to avoid exposure to the sun. If there is a rain forecast, cover the construction area with plastic film in advance to prevent rain.

[0040] The final test was followed by a water immersion bond strength test. The specimen with the XPS board was immersed in water at a temperature of (23±2)℃ for 48 hours. After immersion, the specimen was removed and the surface moisture was gently wiped with a damp cloth. Following the same test method and test points as above, the bond strength after immersion was measured to be 0.35MPa.

[0041] For weather resistance testing, specimens were placed in a test chamber simulating a climatic environment and subjected to multiple freeze-thaw cycles and damp heat aging treatments according to standard procedures. The freeze-thaw cycle conditions were: freezing at -20℃ for 3 hours, followed by thawing in water at 50℃ for 1 hour, repeated 50 times. The damp heat aging conditions were: temperature (60±2)℃, relative humidity (95±3)%, duration 1000 hours. After treatment, the bond strength was tested again, and the strength reduction rate after freeze-thaw cycles was calculated, which was 8%.

[0042] In the open-time test, after applying mortar to the XPS board surface, the XPS boards were bonded at different time intervals (e.g., 10 minutes, 15 minutes, 20 minutes, 25 minutes, and 30 minutes), and then the bond strength was tested according to the above test method. When the XPS boards were bonded after a 20-minute interval, the bond strength remained at 92% of the initial value.

[0043] Example 2: A method for improving the tensile bond strength between extruded polystyrene board and mortar, comprising the following steps:

[0044] Steps S1 and S2 are the same as in Example 1 above, except that the ratio of the dry powder group to the liquid group in S3 is adjusted as follows:

[0045] For the dry powder batch, adjust the formula ratio and weigh out 45% ordinary silicate cement, 45% quartz sand, 2.5% silica fume, 0.01% cellulose ether, 2.5% latex powder (redispersible), 0.2% defoamer, and 0.8% polymer powder (special type). Add these components to the dry powder mixer and mix at a low speed of 150 rpm for 5 minutes to initially mix the components. Then increase the speed to 350 rpm and continue mixing for 12 minutes to ensure uniform mixing. Store the mixed dry powder batch in a sealed, moisture-proof container in a dry environment.

[0046] For the liquid component, the emulsion accounts for 23% and water accounts for 77%. Both are added to a mixing device and stirred at 180 rpm for 6 minutes to form a homogeneous liquid. Then, the dry powder component and the liquid component are mixed in a 3:1 ratio and mechanically stirred at 350 rpm for 4 minutes to prepare the mortar slurry. During the stirring process, the state of the slurry is carefully observed to ensure its homogeneity and good fluidity.

[0047] Then, using a notched trowel of the same specifications as in Example 1, apply the mortar evenly to the surface of the XPS board, controlling the thickness to be approximately 1.3 mm, with an allowable deviation of ±0.1 mm. After application, quickly attach the XPS board to the substrate. During the attachment process, pay attention to adjusting the position of the XPS board to ensure that the gaps between the boards are uniform and consistent, and the gap width does not exceed 2 mm. Gently tap the XPS board with a rubber mallet to ensure that the mortar is in full contact with the XPS board and the substrate, ensuring a firm bond. After construction, take the same curing and protection measures to avoid interference from external factors.

[0048] Performance Testing: Following standard testing procedures, bond strength tests were conducted after the mortar curing period. For the initial bond strength test, six test points were selected, and the results showed an initial bond strength of 0.72 MPa. After immersion in water, the bond strength was tested under the same immersion conditions as in Example 1, and the measured bond strength was 0.33 MPa.

[0049] For weather resistance testing, the freeze-thaw cycles and damp heat aging conditions simulated in the test chamber were the same as in Example 1. After testing, the strength reduction rate after freeze-thaw cycles was 9%. In the open time test, XPS boards were bonded at 20-minute intervals, and the bond strength was 91% of the initial value.

[0050] By analyzing the bonding strength data of XPS boards bonded at different time intervals, the mortar of the present invention was further verified to have good open time performance within a certain period of time, which can meet the needs of different construction rhythms in actual construction.

[0051] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the tensile bond strength between extruded polystyrene board and mortar, characterized in that, The method includes the following steps: S1, Mortar formulation design, the mortar formulation adopts a two-component mortar formulation, the two-component mortar formulation includes a dry powder group and a liquid group, the dry powder group and the liquid group are mixed in a certain proportion to form a uniform slurry; S2, Mortar formulation components and proportions: The dry powder group includes the following components: ordinary Portland cement 40%–60%, quartz sand 30%–50%, silica fume 2%–4%, cellulose ether 0.01%–0.02%, latex powder 1%–3%, defoamer 0.1%–0.2%, and polymer powder 0.5%–1%. The liquid group includes the following components: emulsion 20%–30%, water 70%–80%, and the mixing ratio of the dry powder group and the liquid group is 3:

1. S3, Mortar preparation steps: First, premix all components of the dry powder group evenly in a dry environment to ensure that each component is evenly dispersed. After mixing, place it in a dry place for later use. Next, mix the emulsion and water in the liquid group and stir evenly with a stirring device to form a uniform liquid mixture. Finally, mix the dry powder group and the liquid group in the above 3:1 ratio and stir mechanically for 3 to 5 minutes until there are no lumps in the mixture, forming a uniform slurry. S4, Specific Construction Steps S41. Before construction, the base surface must be cleaned to ensure that it is flat, dry, and free of dust, oil, and other impurities. S42. After cleaning, use a notched trowel to evenly apply the prepared mortar to the XPS board surface. It is recommended to apply the mortar to a thickness of 1-1.5mm. S43, after the mortar is applied, press the XPS board lightly onto the base surface and pat the XPS board gently with your hand to ensure that the mortar and the XPS board are in full contact and that they are fully bonded together. S44. After construction is completed, the construction area should be cured and protected. During the curing period, the construction area should be protected from direct sunlight or rain.

2. The method for improving the tensile bond strength between extruded polystyrene board and mortar according to claim 2, characterized in that, The curing time for the construction area shall be at least 24 hours to ensure that the mortar is fully cured.

3. The method for improving the tensile bond strength between extruded polystyrene board and mortar according to claim 3, characterized in that, The emulsion is one of the following: an acrylic emulsion, an ethylene-vinyl acetate copolymer emulsion, or an acrylic emulsion.

4. The method for improving the tensile bond strength between extruded polystyrene board and mortar according to claim 3, characterized in that, The composition includes 50% ordinary silicate cement, 40% quartz sand, 3% silica fume, 0.015% cellulose ether, 2% latex powder, 0.15% defoamer, and 0.85% polymer powder. The liquid component comprises 25% emulsion and 75% water.

5. A method for improving the tensile bond strength between extruded polystyrene board and mortar according to claim 3, characterized in that, The composition includes 45% ordinary silicate cement, 45% quartz sand, 2.5% silica fume, 0.01% cellulose ether, 2.5% latex powder, 0.2% defoamer, and 0.8% polymer powder. The liquid component comprises 23% emulsion and 77% water.