Special cement mortar for glass brick wall masonry and preparation method thereof

Abstract

The invention belongs to the field of cement mortar, and particularly relates to special cement mortar for glass brick wall masonry and a preparation method thereof, the cement mortar comprises the following raw materials by weight: 10%-20% of general purpose cement, 5%-15% of quartz powder, 2%-10% of limestone powder, 40%-60% of medium sand, 1%-5% of fly ash, 10%-25% of polyvinyl acetate, 1%-5% of benzoate, 3%-8% of Larsen mixture, 0.3%-0.8% of a retarder, 1.0%-2.5% of a water reducer, and 10%-25% of water; wherein the Larsen mixture is prepared by compounding the following components in percentage by weight: 30% of ethylene-vinyl acetate copolymer, 10% of hydroxypropyl methyl cellulose, 20% of nano calcium carbonate and 40% of silica fume; the cement is ordinary Portland cement with the grade of 42.5; the purity of the quartz powder is greater than or equal to 99.5%, the particle size is 200-300 meshes, and the whiteness is greater than or equal to 90. Therefore, the problems of leakage and cracks caused by thermal expansion and cold contraction are solved, and the requirements of the glass curtain wall for air tightness, water tightness, wind pressure resistance, interlayer deformation performance and fire resistance are met at the same time.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of cement mortar, and particularly relates to a special cement mortar for glass brick wall masonry and a preparation method thereof. BACKGROUND

[0002] Glass bricks, as a new type of building material with light transmission, aesthetic and decorative properties, are increasingly widely used in the field of building decoration. At present, in the process of installing glass bricks, a method of connecting steel bars and using structural adhesive is mainly adopted in China. Structural support is provided by steel bar framework, and the bonding and fixing of glass bricks and the base are realized by structural adhesive to form a glass brick wall. However, the existing installation method has many deficiencies. On the one hand, the bonding strength, permeability resistance, flexibility and weather resistance of the structural adhesive cannot meet the long-term use requirements of the glass brick wall. Glass bricks are prone to loosen and fall off, or leakage problems caused by water penetration. When the environmental temperature changes, cracks are easily generated due to the mismatch of thermal expansion and cold shrinkage properties of the structural adhesive and the glass bricks, which affects the integrity and service life of the wall. The air tightness, water tightness, wind pressure resistance, interlayer deformation performance and fire resistance requirements of the glass curtain wall cannot be met at the same time. More importantly, when individual glass bricks are damaged during use, the overall integrity after the curing of the steel bar framework and the structural adhesive restricts the replacement of individual glass bricks, which increases the maintenance difficulty and often requires the demolition and reconstruction of the local or even the whole wall, thereby increasing the maintenance cost and resource waste. SUMMARY

[0003] The present application aims to solve the problems of the bonding strength, permeability resistance, flexibility and weather resistance of the structural adhesive, which cannot meet the long-term use requirements of the glass brick wall, and the glass bricks are prone to loosen and fall off, or leakage problems caused by water penetration. When the environmental temperature changes, cracks are easily generated due to the mismatch of thermal expansion and cold shrinkage properties of the structural adhesive and the glass bricks, which affects the integrity and service life of the wall. The air tightness, water tightness, wind pressure resistance, interlayer deformation performance and fire resistance requirements of the glass curtain wall cannot be met at the same time. More importantly, when individual glass bricks are damaged during use, the overall integrity after the curing of the steel bar framework and the structural adhesive restricts the replacement of individual glass bricks, which increases the maintenance difficulty and often requires the demolition and reconstruction of the local or even the whole wall, thereby increasing the maintenance cost and resource waste.

[0004] To achieve the above object, the application adopts the following technical scheme: a special cement mortar for glass brick wall masonry and a preparation method thereof, the cement mortar is composed of the following raw materials in percentage by weight: general cement 10-20%, quartz powder 5-15%, limestone powder 2-10%, medium sand 40-60%, fly ash 1-5%, polyvinyl acetate 10-25%, benzoate 1-5%, Larsen mixture 3-8%, retarder 0.3-0.8% (based on the weight of cement), water reducing agent 1.0-2.5% (based on the weight of cement), and water 10-25%; wherein the Larsen mixture is compounded by the following components in weight ratio: ethylene-vinyl acetate copolymer 30%, hydroxypropyl methylcellulose 10%, nano calcium carbonate 20%, and silica ash 40%; the cement is ordinary Portland cement of grade 42.5; the quartz powder has purity ≥ 99.5% and particle size of 200-300 mesh, and whiteness ≥ 90.

[0005] A preparation method of a special cement mortar for glass brick wall masonry, comprising the following steps: S1. Using a compulsory mixer (mixing capacity 50-200 L) to mix cement, quartz powder, limestone powder, sand and fly ash, first stirring at 300 r / min for 3 min, and then stirring at 500 r / min for 2-3 min to form uniform component A; S2. Putting polyvinyl acetate, benzoate, Larsen mixture, retarder and water reducing agent into another container, stirring at 800-1000 r / min for 4-6 min at 20-25℃ to form uniform component B; S3. Mixing component A and component B in weight ratio of (80-90):(10-20), and stirring at 300-350 r / min for 3 min; S4. Adding water in three times during the stirring process, adding 50%, 30% and 20% of the total water amount respectively, and stirring for 1 min, 1.5 min and 2 min respectively after each time of adding water, and continuing to stir until the mortar consistency reaches the spreadability of 200-250 mm to obtain the special cement mortar.

[0006] Further, the medium sand has fineness modulus of 2.3-3.0, clay content ≤ 3%, and mud block content ≤ 1%, and is used after water washing treatment.

[0007] Further, the polyvinyl acetate is an emulsion type product, with solid content of 50-60%, viscosity of 2000-5000 mPa・s (25℃), pH value of 4-6, and residual acetic acid content ≤ 0.5%.

[0008] Further, the retarder is citric acid with purity ≥ 99%, and is added in amount of 0.6-0.8% of the weight of cement in summer high temperature, and 0.3-0.5% in winter low temperature.

[0009] Furthermore, the water reducer is a melamine formaldehyde resin water reducer with a solid content of 25% to 30% and a water reduction rate of ≥15%.

[0010] Furthermore, the mixing ratio of component A to component B is (80-90):(10-20).

[0011] Furthermore, in step S1, the rotation speed of the forced mixer is 300 r / min in the low speed stage and 500 r / min in the high speed stage.

[0012] Compared with the existing technology, the advantages of the special cement mortar for glass brick wall construction and its preparation method are: 1. The present invention achieves a synergistic improvement in bonding strength, impermeability, flexibility, and weather resistance through a composite structure formed by scientifically proportioning inorganic raw materials such as general-purpose cement and quartz powder with organic components such as polyvinyl acetate and Larsen mixture. The inorganic raw materials provide the basic strength of the mortar to firmly fix the glass bricks, while the organic components enhance the interfacial bonding with the glass bricks through intermolecular forces and relieve the stress caused by temperature changes. The addition of water reducer and silica fume reduces porosity to enhance impermeability. This solves the problems of glass bricks loosening and falling easily, leakage, and cracking due to thermal expansion and contraction that exist in existing structural adhesive bonding methods, while simultaneously meeting the air tightness, water tightness, wind pressure resistance, interlayer deformation performance, and fire resistance requirements of glass curtain walls.

[0013] 2. The present invention achieves a dual improvement in construction convenience and maintenance flexibility through the structural design of "unreinforced masonry + special mortar operability" - there is no need to build a steel skeleton during construction, and installation can be completed directly by applying mortar, and the retarder can adjust the setting time to adapt to different environments, simplifying the construction process; at the same time, the mortar still retains a certain degree of separability after hardening. When a single glass brick is damaged, the broken brick and mortar can be directly separated for replacement, thereby solving the problem of cumbersome construction and inability to replace a single block in the existing method of stringing reinforcement and structural adhesive, which leads to maintenance difficulties. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Fig. 1 This is a schematic diagram of the raw material preparation process of the special cement mortar for glass brick wall construction and its preparation method provided by the present invention; Fig. 2 This is a schematic diagram of a cement mortar preparation process for the special cement mortar for glass brick wall construction and a preparation method thereof provided by the present invention; Fig. 3 The invention provides a schematic diagram of the construction process of the special cement mortar for glass brick wall construction and a preparation method thereof. DETAILED DESCRIPTION

[0015] The following examples are for illustrative purposes only and are not intended to limit the scope of the present application.

[0016] As Figs. 1-3 shown in the figure, a glass brick wall masonry special cement mortar and a preparation method thereof, the cement mortar is composed of the following raw materials in percentage by weight: ordinary Portland cement 10%~20%, quartz powder 5%~15%, limestone powder 2%~10%, medium sand 40%~60%, fly ash 1%~5%, polyvinyl acetate 10%~25%, benzoate 1%~5%, larsen mixture 3%~8%, retarder 0.3%~0.8% (by weight of cement), water reducing agent 1.0%~2.5% (by weight of cement), water 10%~25%; wherein the larsen mixture is compounded by the following components in weight ratio: ethylene-vinyl acetate copolymer 30%, hydroxypropyl methyl cellulose 10%, nano calcium carbonate 20%, silica ash 40%; the cement is ordinary Portland cement of grade 42.5; the quartz powder has purity ≥99.5%, particle size of 200~300 mesh, and whiteness ≥90.

[0017] It should be noted that the weight percentage range of each raw material described in the present embodiment is determined based on the differentiated requirements of mortar performance in different application scenarios, for example, in a humid environment with higher bonding strength requirements, the proportion of polyvinyl acetate can be appropriately increased to 20%~25%, and the proportion of medium sand can be correspondingly reduced to 40%~50%; while in a dry and high-flowing construction environment, the proportion of water can be adjusted to 20%~25%, while ensuring that the proportions of other raw materials are adapted within the limited range to ensure that the comprehensive performance of the mortar meets the standards.

[0018] A preparation method of a glass brick wall masonry special cement mortar, comprising the following steps: S1. using a compulsory mixer (mixing capacity 50-200L) to mix cement, quartz powder, limestone powder, sand and fly ash, first stirring at 300r / min for 3min, then stirring at 500r / min for 2-3min, to form uniform component A; S2. putting polyvinyl acetate, benzoate, larsen mixture, retarder and water reducing agent into another container, stirring at 800-1000r / min for 4-6min at 20-25℃, to form uniform component B; S3. mixing component A and component B in weight ratio of (80~90):(10~20), stirring at 300~350r / min for 3min; S4. adding water in 3 times during stirring, adding 50%, 30% and 20% of the total water amount in order, stirring for 1min, 1.5min and 2min respectively after each time of water addition, and continuing to stir until the mortar consistency reaches 200~250mm of spread, to obtain the special cement mortar.

[0019] It should be noted that in the preparation steps described in this embodiment, the stirring time and speed are set to ensure that the raw materials are fully mixed and do not damage the properties of the raw materials themselves, for example, in step S1, low-speed stirring first can prevent fine powders such as cement from flying, and high-speed stirring can promote uniform dispersion of the materials; in step S4, water is added in several times and the stirring time is controlled, which can effectively avoid the stratification of the mortar caused by excessive local water content. If the ambient temperature deviates from 20-25℃, the total stirring time can be adjusted appropriately, such as shortening by 10%-15% at high temperature or lengthening by 10%-20% at low temperature, to ensure that the mortar consistency meets the requirements.

[0020] Further, the fine modulus of the medium sand is 2.3-3.0, the clay content is ≤3%, the mud content is ≤1%, and it is used after water washing treatment.

[0021] It should be noted that in the medium sand parameters described in this embodiment, the medium sand with a fine modulus of 2.3-3.0 can provide good construction fluidity while ensuring the strength of the mortar, and the limitation of clay content and mud content can avoid the influence of impurities on the bonding force of the mortar and glass bricks, and the water washing treatment not only reduces the clay content, but also removes the soluble salt on the surface of the sand particles, preventing the salt from analyzing out in the later period to cause white frost on the surface of the glass bricks, affecting the aesthetic appearance.

[0022] Further, the polyvinyl acetate is an emulsion product with a solid content of 50%-60%, a viscosity of 2000-5000 mPa・s (25℃), a pH value of 4-6, and a residual acetic acid content of ≤0.5%.

[0023] It should be noted that in the polyvinyl acetate parameters described in this embodiment, a solid content of 50%-60% can balance its bonding force and the flexibility of the mortar, a viscosity that is too low can cause the mortar to flow too easily, and a viscosity that is too high can increase the difficulty of stirring, a weak acidic environment with a pH value of 4-6 can inhibit the growth of microorganisms, prolonging the storage time, and a residual acetic acid content of ≤0.5% can avoid adverse effects on the cement hydration reaction, ensuring normal development of the mortar strength.

[0024] Further, the retarder is citric acid with a purity of ≥99%, which is added at a dosage of 0.6%-0.8% of the cement weight in summer and 0.3%-0.5% in winter.

[0025] It should be noted that the dosage adjustment of the retarder described in this embodiment is based on the influence of temperature on the cement hydration speed. In summer, the cement hydration speed increases, and increasing the dosage of citric acid can prolong the initial setting time of the mortar to more than 4 hours, ensuring sufficient time for construction operation. Reducing the dosage in winter can avoid slow hydration leading to slow strength development, and citric acid with a purity of ≥99% can reduce the interference of impurities on the performance of the mortar, ensuring stable retardation effect.

[0026] Further, the water reducing agent is melamine formaldehyde resin water reducing agent, solid content 25%-30%, water reducing rate ≥15%.

[0027] It should be noted that the water reducing agent parameters described in this embodiment, the solid content of 25%-30% can ensure the effective ingredient concentration in the mortar, and the water reducing rate of ≥15% can significantly reduce the mixing water consumption, improve the mortar strength, reduce the porosity, and enhance the impermeability. The melamine formaldehyde resin water reducing agent has good compatibility with other organic components in the formula, and does not produce stratification or precipitation phenomenon, ensuring uniform and stable performance of the mortar.

[0028] Further, the mixing ratio of component A and component B is (80-90):(10-20).

[0029] It should be noted that the mixing ratio range described in this embodiment is determined by considering the balance between the strength and flexibility of the mortar. If the proportion of component A is too high, the mortar will lack flexibility and be prone to cracks due to temperature changes. If the proportion of component B is too high, the mortar strength will be reduced, affecting the bonding force. In actual application, the size of the glass brick can be adjusted. For example, when building large-size glass bricks (edge length ≥ 300 mm), the proportion of component A can be 85%-90% to improve the mortar bearing capacity.

[0030] Further, in step S1, the rotational speed of the forced mixer is 300 r / min in the low-speed stage and 500 r / min in the high-speed stage.

[0031] It should be noted that the stirring speed described in this embodiment is 300 r / min in the low-speed stage, which can make the aggregates such as sand fully dispersed and avoid agglomeration. The high-speed stage can promote the uniform combination of cement, quartz powder and other fine powders with aggregates. If the power of the mixer is different, the rotational speed can be adjusted according to the linear speed equivalence principle to ensure consistent mixing effect. For example, the rotational speed of a small-capacity mixer (50 L) can be appropriately increased to 350 r / min and 550 r / min, and the rotational speed of a large-capacity mixer (200 L) can be appropriately reduced to 280 r / min and 480 r / min to ensure uniform mixing of materials.

[0032] Example 1 A special cement mortar for glass brick wall building is prepared according to the following weight percentage: 42.5-grade ordinary Portland cement 15% (initial setting time 50 min, final setting time 550 min, 3d compressive strength 23 MPa); Quartz powder 10% (purity 99.6%, particle size 250 mesh, whiteness 92); Limestone powder 5%; Medium sand 50% (fineness modulus 2.6, clay content 2%, treated by water washing); Class I fly ash 3% (water demand ratio 93%, loss on ignition 4%); Polyvinyl acetate 12% (emulsion type, solid content 55%, viscosity 3500 mPa・s (25℃), pH value 5); Benzoate 3% (purity 99.6%); Larson mixture 5% (ethylene-vinyl acetate copolymer 30%, hydroxypropyl methylcellulose 10%, 50 nm nano calcium carbonate 20%, silica ash 40%, passed through 80 mesh sieve); Retarder 0.5% (by weight of cement, citric acid purity 99.2%); Water reducing agent 1.8% (by weight of cement, melamine formaldehyde resin water reducing agent, solid content 28%, water reducing rate 16%); Water 15% (tap water, pH value 7); Preparation method: Preparation of component A: cement, quartz powder, limestone powder, medium sand, fly ash are put into a 50L forced mixer, stirred at 300r / min for 3min, then stirred at 500r / min for 2min, and mixed uniformly.

[0033] Preparation of component B: polyvinyl acetate, benzoate, larson mixture, retarder, water reducing agent are put into a container, stirred at 900r / min for 5min at 25℃, until there is no stratification.

[0034] Mix according to the weight ratio of A:B=85:15, stir at 320r / min for 3min, add water in 3 times (50%, 30%, 20%), stir for 1min, 1.5min, 2min respectively after each time of water addition, finally stir to 220mm of spread, and prepare the mortar.

[0035] Construction application: used for masonry of glass bricks with edge length of 200mm, after base treatment, the mortar is applied with thickness of 6mm, cured for 5d, tested to have 28d bonding strength of 1.8MPa, impermeability grade P8, and no cracks after bending 180°.

[0036] Example 2 A special cement mortar for glass brick wall masonry is prepared according to the following weight percentage: Ordinary Portland cement 42.5 20% (initial setting time 48min, final setting time 580min, 3d compressive strength 24MPa); Quartz powder 12% (purity 99.5%, particle size 280 mesh, whiteness 91); Limestone powder 8%; Medium sand 45% (fineness modulus 2.8, clay content 2.5%, treated by water washing); Class II fly ash 4% (water demand ratio 100%, loss on ignition 7%); Polyvinyl acetate 20% (emulsion type, solid content 58%, viscosity 4000 mPa-s (25°C), pH value 5.5); Benzoate 4% (purity 99.5%); Larson mixture 6% (same composition as in Example 1); Retarder 0.7% (by weight of cement, citric acid purity 99.3%, added in high summer temperature); Water reducing agent 2.2% (by weight of cement, melamine formaldehyde resin water reducing agent, solid content 29%, water reducing rate 17%); Water 22% (tap water, pH value 7.5); Preparation method: Preparation of component A: The above solid raw materials are put into a 100L forced stirrer, stirred at 300r / min for 3min, and then stirred at 500r / min for 3min until uniform.

[0037] Preparation of component B: The liquid and additives are put into a container, stirred at 850r / min for 5min at 22°C until completely dispersed.

[0038] Mix according to the weight ratio A:B=82:18, stir at 340r / min for 3min, add water in 3 times (same ratio as in Example 1), and stir until the spread is 240mm.

[0039] Construction application: used for building glass bricks with an edge length of 350mm, the mortar is applied with a thickness of 9mm, cured for 7d, and the 28d bonding strength is 2.0MPa, the impermeability grade is P8, and there is no crack after bending 180°.

[0040] The working principle of the present application is as follows: The inorganic ingredients (general-purpose cement, quartz powder, limestone powder, medium sand, fly ash) and the organic ingredients (polyvinyl acetate, benzoate, larsen mixture) synergize, wherein the inorganic raw materials such as cement and quartz powder provide the base strength for the mortar, the organic ingredients such as ethylene-vinyl acetate copolymer in polyvinyl acetate and larsen mixture endow the mortar with flexibility and adhesion, the setting time is adjusted by the retarder (citric acid) to adapt to the construction environment, the water reducing agent (melamine formaldehyde resin) reduces the water consumption and improves the density, and then through the preparation method of grouping and stirring (component A ensures the uniform dispersion of inorganic raw materials, and component B ensures the full fusion of organic ingredients), controlling the rotation speed and the water adding mode, the raw materials form a whole with stable structure and balanced performance, which has enough strength to fix the glass bricks and good flexibility to adapt to thermal expansion and cold contraction, and the impermeability is enhanced through optimization of grading and additive effect; the technology solves the problems in the background art in the following ways: first, the organic and inorganic ingredients synergize to improve the bonding strength (polyvinyl acetate and larsen mixture enhance the interfacial adhesion), impermeability (water reducing agent reduces porosity + silica ash filling and densification), flexibility (EVA and polyvinyl acetate relieve stress) and weather resistance (stable organic ingredients resist environmental aging), overcoming the performance deficiency of structural adhesive; second, the construction process is simplified (no need to build a steel skeleton, the mortar can be directly applied) and the setting time is adjusted by the retarder to improve the construction efficiency, solving the problem of complicated construction of existing methods; third, the mortar remains a certain operability after hardening and is not bound by the steel skeleton, when individual glass bricks are damaged, the damaged brick can be separated from the mortar by tools, replaced individually and then coated with mortar to fix, realizing single replacement and solving the maintenance difficulty.

[0041] The above is only the preferred embodiment of the present application, and is not intended to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A special cement mortar for glass brick wall construction, characterized in that: The cement mortar is composed of the following raw materials in percentage by weight: 10% to 20% general cement, 5% to 15% quartz powder, 2% to 10% limestone powder, 40% to 60% medium sand, 1% to 5% fly ash, 10% to 25% polyvinyl acetate, 1% to 5% benzoate, 3% to 8% Larsen mixture, 0.3% to 0.8% retarder, 1.0% to 2.5% water reducer, and 10% to 25% water.

2. The special cement mortar for glass brick wall construction according to claim 1, characterized in that: The Larsen mixture is compounded by weight of the following components: 30% ethylene-vinyl acetate copolymer, 10% hydroxypropyl methylcellulose, 20% nano-calcium carbonate, and 40% silica fume; the cement is 42.5 grade ordinary Portland cement; the quartz powder has a purity of ≥99.5%, a particle size of 200-300 meshes, and a whiteness of ≥90.

3. A method for preparing special cement mortar for glass brick wall construction, characterized in that: The steps include: S1. Use a forced mixer (mixing capacity 50-200 L) to mix cement, quartz powder, limestone powder, sand, and fly ash at 300 rpm for 3 minutes, then at 500 rpm for 2-3 minutes to form a uniform component A. S2. The polyvinyl acetate, benzoate, Larsen mixture, retarder and water reducer are placed in another container and stirred at 800-1000r / min for 4-6 minutes at 20-25°C to form a uniform component B; S3. Mix component A and component B in a weight ratio of (80-90): (10-20) and stir at 300-350 r / min for 3 minutes; S4. During the mixing process, add water in three times, in the order of 50%, 30%, and 20% of the total water volume. Stir for 1 minute, 1.5 minutes, and 2 minutes after each addition of water. Continue stirring until the mortar consistency reaches an expansion of 200-250mm to obtain a special cement mortar.

4. The special cement mortar for glass brick wall construction according to claim 1, characterized in that: The medium sand has a fineness modulus of 2.3 to 3.0, a mud content of ≤3%, a mud block content of ≤1%, and is used after being washed with water.

5. The special cement mortar for glass brick wall construction according to claim 1, characterized in that: The polyvinyl acetate is an emulsion product with a solid content of 50% to 60%, a viscosity of 2000 to 5000 mPa·s (25° C.), a pH value of 4 to 6, and a residual acetic acid content of ≤0.5%.

6. The special cement mortar for glass brick wall construction according to claim 1, characterized in that: The retarder is citric acid with a purity of ≥99%, which is added at 0.6%-0.8% of the weight of the cement during high temperatures in summer and at 0.3%-0.5% during low temperatures in winter.

7. The special cement mortar for glass brick wall construction according to claim 1, characterized in that: The water reducing agent is a melamine formaldehyde resin water reducing agent with a solid content of 25% to 30% and a water reduction rate of ≥15%.

8. The method for preparing the special cement mortar for glass brick wall construction according to claim 3, characterized in that: The mixing ratio of component A and component B is (80-90): (10-20).

9. The method for preparing the special cement mortar for glass brick wall construction according to claim 3, characterized in that: In step S1, the rotation speed of the forced mixer is 300 r / min in the low speed stage and 500 r / min in the high speed stage.

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