Aerated concrete masonry insulation mortar suitable for low-temperature environments and its preparation method

Abstract

The present application relates to the technical field of mortar, in particular to an aerated concrete masonry insulation mortar capable of being used in low-temperature environment and a preparation method thereof, the insulation mortar comprises the following raw materials in parts by weight: 25-40 parts of low-carbon cementitious material, 25-40 parts of fine aggregate, 5-10 parts of fly ash, 0.2-1 part of early strength agent, 10-25 parts of vitrified microbead, and 0.2-2 parts of anti-freezing agent. The present application solves the problem that the existing aerated concrete masonry mortar cannot be used in low-temperature environment and is prone to cracking in winter, and can improve the initial temperature during mixing of the mortar, is suitable for construction in special areas or low-temperature environment, and is more similar to the performance of aerated concrete blocks, and meets the mechanical performance requirements of aerated concrete masonry mortar in low-temperature environment.

Description

Technical Field

[0001] This invention relates to the field of mortar technology, specifically to aerated concrete masonry insulation mortar that can be used in low-temperature environments and its preparation method. Background Technology

[0002] Autoclaved aerated concrete (AAC) is a new type of green and energy-saving wall material with advantages such as lightweight, sound insulation, heat insulation, and fire resistance. It also makes extensive use of fly ash and tailings, thus possessing environmental benefits. However, due to its rich porous structure, AAC has poor durability. In cold climates, under the influence of low temperatures, carbonization, and wet-dry cycles, its compressive strength decreases significantly in a short period, leading to wall cracking. When the external temperature and humidity change, the air-dried AAC freezes, increasing its moisture content and causing significant shrinkage and expansion deformation, resulting in wall cracking. Since the wall is mainly composed of mortar and blocks, excessive drying shrinkage of the mortar leads to increased wall deformation, causing cracks and leaks, severely affecting the wall's heat insulation and sound insulation performance, and also posing structural safety hazards. Increasing the amount of mortar used is a primary solution, but this is energy-intensive and does not align with current environmental protection trends.

[0003] Currently, the mortar used for aerated concrete (APC) construction is mainly traditional mortar, which has poor density and structure compatibility with APC. Furthermore, traditional APC mortar is generally suitable for temperatures of 5℃ and above. Taking northern China as an example, temperatures gradually drop below 5℃ starting in October each year. Due to these climatic conditions, APC construction becomes very difficult at low temperatures. When traditional mortar is mixed with water, its hydration and curing process involves volume shrinkage, which can easily lead to cracking. Therefore, there is an urgent need to develop a thermal insulation mortar for APC that can be used at low temperatures. This mortar should provide an initial mixing temperature suitable for construction in special regions or low-temperature environments, and its performance should be closer to that of APC blocks, meeting the mechanical performance requirements of APC mortar at low temperatures. Summary of the Invention

[0004] The technical problem this invention aims to solve is to provide an aerated concrete masonry insulation mortar that can be used in low-temperature environments and its preparation method, thereby addressing the issue that existing aerated concrete masonry mortars cannot be used at low temperatures and are prone to cracking in winter. This invention can also be used at room temperature.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] Aerated concrete masonry insulation mortar suitable for use in low-temperature environments, wherein the insulation mortar comprises the following raw materials in parts by weight:

[0007] Low-carbon cementitious materials: 25-40 parts;

[0008] Fine aggregate: 25-40 parts;

[0009] Fly ash: 5-10 parts;

[0010] Early strength agent: 0.2–1 part;

[0011] Vitrified microspheres: 10-25 parts;

[0012] Antifreeze: 0.2–2 parts;

[0013] The low-carbon cementitious material includes limestone, low-grade bauxite, anhydrite, and sand. The low-carbon cementitious material contains 15–35 wt.% free calcium oxide, 5–10 wt.% anhydrous calcium sulfoaluminate, 40–55 wt.% dicalcium silicate, 3–7 wt.% anhydrous calcium sulfate, and 2–5 wt.% tetracalcium aluminoferrite.

[0014] In some embodiments, aerated concrete masonry insulation mortar can be used in low-temperature environments, and the insulation mortar comprises the following raw materials in parts by weight:

[0015] Low-carbon cementitious materials: 28-35 parts;

[0016] Fine aggregate: 30-35 parts;

[0017] Fly ash: 5-8 parts;

[0018] Early strength agent: 0.2–0.8 parts;

[0019] Vitrified microspheres: 15-22 parts;

[0020] Antifreeze: 0.5–1.5 parts;

[0021] The low-carbon cementitious material includes limestone, low-grade bauxite, anhydrite, and sand. The low-carbon cementitious material contains 18–30 wt.% free calcium oxide, 6–8 wt.% anhydrous calcium sulfoaluminate, 40–45 wt.% dicalcium silicate, 5–7 wt.% anhydrous calcium sulfate, and 2–5 wt.% tetracalcium aluminoferrite.

[0022] Preferably, the low-carbon cementitious material contains 23.7 wt.% free calcium oxide, 6.3 wt.% anhydrous calcium sulfoaluminate, 40.6 wt.% dicalcium silicate, 5.9 wt.% anhydrous calcium sulfate, 2.03 wt.% tetracalcium aluminoferrite, and 11.5 wt.% other components.

[0023] Furthermore, the fine aggregate is one or both of sand and aerated concrete waste.

[0024] Furthermore, the proportions of the fine aggregate components with particle sizes less than 0.63 mm, 0.63 mm to 0.80 mm, and 0.80 mm to 0.15 mm are 20%, 40%, and 40%, respectively.

[0025] Furthermore, the early strength agent is one or both of calcium formate and lithium carbonate.

[0026] Furthermore, the fly ash is Class I fly ash or Class II fly ash, and the proportion of fly ash particles with a particle size of 3 to 15 μm is not less than 33%.

[0027] Furthermore, the antifreeze is a mixture of acrylic emulsion and ethylene glycol in a mass ratio of 1:(0.2-0.5).

[0028] Furthermore, the specific surface area of ​​the low-carbon cementitious material is 380–420 m². 2 / kg.

[0029] This invention also provides a method for preparing aerated concrete masonry insulation mortar that can be used in low-temperature environments, comprising the following steps:

[0030] Step 1: Add water to the low-carbon cementitious material and stir to hydrate it to obtain a slurry; preferably, the water-cement ratio is 0.5-0.6, the stirring time is 3-10 min, and the stirring speed is 130-290 r / min.

[0031] Step 2: Add fine aggregate, fly ash, vitrified microspheres, early strength agent, and antifreeze agent to the slurry and stir evenly to obtain the thermal insulation mortar.

[0032] Furthermore, the preparation of the low-carbon cementitious material includes the following steps:

[0033] Step a: Weigh limestone, low-grade bauxite, anhydrite, and sand, grind and mix them evenly to obtain a mixture;

[0034] Step b: The mixture is calcined at a low temperature to obtain the low-carbon cementitious material; preferably, the calcination temperature is 1200-1350℃ and the calcination time is 30min.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The thermal insulation mortar of this invention uses low-carbon cementitious materials. The heat released during the reaction of free calcium oxide with water to form calcium hydroxide raises the initial temperature of the mortar, ensuring that the initial temperature remains high even under low-temperature conditions, guaranteeing proper cement hydration. Free calcium oxide and other cement components are associated and encapsulated. The partially dissociated free calcium oxide reacts first, raising the temperature, followed by the reaction of other cement components. The temperature rise is slow and uniform, providing continuous heat during the early and later stages of hydration. Simultaneously, the volume expansion during the reaction of free calcium oxide and anhydrous calcium sulfoaluminate with water to form calcium hydroxide compensates for the volume shrinkage of the mortar during drying, reducing cracking. Furthermore, the early-strength agent accelerates the hydration of dicalcium silicate and anhydrous calcium sulfoaluminate, thereby improving the mortar's bond strength. The anhydrous calcium sulfate used also has an early-strength effect, synergistically promoting hydration and early strength with the early-strength agent; additionally, the anhydrous calcium sulfate can regulate the reaction rate of free calcium oxide.

[0037] 2. This invention employs an antifreeze agent composed of acrylic emulsion and ethylene glycol, which promotes the improvement of the frost resistance of concrete blocks and further enhances the frost resistance of the mortar. Simultaneously, the hydrated components of anhydrous calcium sulfoaluminate possess excellent frost resistance. At low temperatures, the anhydrous calcium sulfoaluminate hydrate poses no risk of exceeding its thermal stability temperature and achieves rapid hardening and early strength. When the temperature rises, its strength recovers to its original level and does not decrease due to freezing. Based on the synergistic effect of the antifreeze agent and anhydrous calcium sulfoaluminate, this mortar remains crack-free and does not peel off during long-term operation under severe cold conditions, ensuring durability.

[0038] 3. This invention uses fly ash to improve the fluidity of mortar, inhibit mortar bleeding, and ensure construction performance. The active components of fly ash are silicon dioxide and aluminum oxide. When mixed with cement and water, they can form a relatively stable cementitious substance, thereby giving the mortar higher strength, reducing the occurrence of mortar cracking in low-temperature environments, and improving the frost resistance of the mortar. Fly ash can also compensate for insufficient fine particles, interrupt continuous bleeding channels, and ensure later-stage strength.

[0039] 4. The present invention adopts a reasonable combination of sand gradation, with coarse sand (0.80-0.15mm) providing a "skeleton" for fine sand (less than 0.63mm, 0.63mm-0.80mm). Both coarse and fine sand can fully contact water to carry out hydration reaction, so that the compressive strength and bonding strength can be maximized.

[0040] 5. The low-carbon cementitious material used in this invention is calcined at low temperature, which is simple to operate and has lower carbon emissions than other cements. Furthermore, it utilizes fly ash, aerated concrete waste, etc., to achieve a low-carbon and environmentally friendly effect. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0042] In this embodiment of the invention, the proportions of the fine aggregate with a particle size less than 0.63 mm, a particle size between 0.63 mm and 0.80 mm, and a particle size between 0.80 mm are 20%, 40%, and 40%, respectively.

[0043] In the embodiments of the present invention, the early strength agent is one or both of calcium formate and lithium carbonate.

[0044] In the embodiments of the present invention, the fly ash is Class I fly ash or Class II fly ash, and the proportion of the fly ash particle size of 3 to 15 μm is not less than 33%.

[0045] In this embodiment of the invention, the antifreeze is a mixture of acrylic emulsion and ethylene glycol in a mass ratio of 1:(0.2-0.5).

[0046] In this embodiment of the invention, the specific surface area of ​​the low-carbon cementitious material is 380–420 m². 2 / kg.

[0047] The method for preparing thermal insulation mortar in this embodiment of the invention includes the following steps:

[0048] Step 1: Add water to the low-carbon cementitious material and stir to hydrate it to obtain a slurry; preferably, the water-cement ratio is 0.5-0.6, the stirring time is 3-10 min, and the stirring speed is 130-290 r / min.

[0049] Step 2: Add fine aggregate, fly ash, vitrified microspheres, early strength agent, and antifreeze agent to the slurry and stir evenly to obtain the thermal insulation mortar.

[0050] In the embodiments of the present invention, the low-carbon cementitious material contains 23.7 wt.% free calcium oxide, 6.3 wt.% anhydrous calcium sulfoaluminate, 40.6 wt.% dicalcium silicate, 5.9 wt.% anhydrous calcium sulfate, 2.03 wt.% tetracalcium aluminoferrite, and 11.5 wt.% other components.

[0051] Furthermore, the preparation of the low-carbon cementitious material includes the following steps:

[0052] Step a: Weigh limestone, low-grade bauxite, anhydrite, and sand, grind and mix them evenly to obtain a mixture;

[0053] Step b: The mixture is calcined at a low temperature to obtain the low-carbon cementitious material; preferably, the calcination temperature is 1200-1350℃ and the calcination time is 30min.

[0054] Example 1

[0055] As a preferred embodiment of the present invention, the specific composition of the aerated concrete masonry insulation mortar that can be used in low-temperature environments disclosed in this embodiment is shown in Table 1.

[0056] Table 1

[0057]

[0058]

[0059] In this embodiment, the low-carbon cementitious material is first hydrated with water at 2°C to obtain a slurry. Preferably, the water-cement ratio is 0.55, the stirring time is 5 minutes, and the stirring speed is 140 r / min. Then, fine aggregate, fly ash, vitrified microspheres, early strength agent, and antifreeze agent are added to the slurry and stirred evenly to obtain thermal insulation mortar #1. Thermal insulation mortar #1 is then cured at an ambient temperature of 2°C.

[0060] Example 2

[0061] As a preferred embodiment of the present invention, the specific composition of the aerated concrete masonry insulation mortar that can be used in low-temperature environments disclosed in this embodiment is shown in Table 2.

[0062] Table 2

[0063]

[0064] In this embodiment, the low-carbon cementitious material is first hydrated with water at 2°C to obtain a slurry. Preferably, the water-cement ratio is 0.55, the stirring time is 5 minutes, and the stirring speed is 140 r / min. Then, fine aggregate, fly ash, vitrified microspheres, early strength agent, and antifreeze agent are added to the slurry and stirred evenly to obtain thermal insulation mortar #2. Thermal insulation mortar #2 is then cured at an ambient temperature of 2°C.

[0065] Example 3

[0066] As a preferred embodiment of the present invention, the specific composition of the aerated concrete masonry insulation mortar that can be used in low-temperature environments disclosed in this embodiment is shown in Table 3.

[0067] Table 3

[0068]

[0069] In this embodiment, the low-carbon cementitious material is first hydrated with water at 2°C to obtain a slurry. Preferably, the water-cement ratio is 0.55, the stirring time is 5 minutes, and the stirring speed is 140 r / min. Then, fine aggregate, fly ash, vitrified microspheres, early strength agent, and antifreeze agent are added to the slurry and stirred evenly to obtain the thermal insulation mortar #3. The thermal insulation mortar #3 is then cured at an ambient temperature of 2°C.

[0070] Example 4

[0071] As a preferred embodiment of the present invention, the specific composition of the aerated concrete masonry insulation mortar that can be used in low-temperature environments disclosed in this embodiment is shown in Table 4.

[0072] Table 4

[0073]

[0074] In this embodiment, the low-carbon cementitious material is first hydrated with water at 20°C to obtain a slurry. Preferably, the water-cement ratio is 0.55, the stirring time is 5 minutes, and the stirring speed is 140 r / min. Then, fine aggregate, fly ash, vitrified microspheres, early strength agent, and antifreeze agent are added to the slurry and stirred evenly to obtain thermal insulation mortar #4. Thermal insulation mortar #4 is then cured at an ambient temperature of 20°C.

[0075] Comparative Example 1

[0076] The specific composition of the thermal insulation mortar in this comparative example is shown in Table 5.

[0077] Table 5

[0078]

[0079] In this comparative example, rapid-hardening sulfoaluminate cement was first hydrated with water at 2°C to obtain a slurry. Preferably, the water-cement ratio was 0.55, the mixing time was 3 minutes, and the mixing speed was 140 r / min. Then, fine aggregate, fly ash, early-strength agent, vitrified microspheres, and antifreeze agent were added to the slurry and mixed evenly to obtain comparative thermal insulation mortar 1. Comparative thermal insulation mortar 1 was cured at an ambient temperature of 2°C.

[0080] Comparative Example 2

[0081] The specific composition of the thermal insulation mortar in this comparative example is shown in Table 6.

[0082] Table 6

[0083]

[0084]

[0085] In this comparative example, rapid-hardening sulfoaluminate cement and silicate cement were first mixed to form a mixed cement. Water at 2°C was added to the mixed cement and stirred to hydrate it, resulting in a slurry. Preferably, the water-cement ratio was 0.55, the stirring time was 3 minutes, and the stirring speed was 140 r / min. Then, fine aggregate, fly ash, early-strength agent, vitrified microspheres, and antifreeze agent were added to the slurry and stirred evenly to obtain comparative thermal insulation mortar 2. Comparative thermal insulation mortar 2 was cured at an ambient temperature of 2°C.

[0086] According to the JGJ / T 70~2009 standard for basic performance test methods of building mortar, the performance of the thermal insulation mortars after curing in Examples 1~5 and Comparative Examples 1~2 was tested, and the performance results are shown in Table 7.

[0087] Table 7

[0088]

[0089] As shown in Table 7, the aerated concrete masonry insulation mortar provided by this invention, which can be used at low temperatures, although its setting and hardening are slower in low-temperature environments (Examples 1-3) than at normal temperatures (Example 4), still meets the construction requirements and can be used at low temperatures of 1-5℃ or above. The difference between Example 1 and Comparative Example 1 lies in the use of low-carbon cementitious materials and rapid-hardening sulfoaluminate cement. Sulfoaluminate cement can be used in low-temperature environments, with a short setting time but slow strength development. Comparative Example 2 uses a combination of silicate cement and sulfoaluminate cement. Due to the low-temperature environment, the setting time is longer, and sulfoaluminate cement reacts first at low temperatures, leading to inconsistent hydration processes with silicate cement, potentially resulting in uneven mortar strength development and low strength. Through comparison, it was found that the insulation mortar of this invention has a small difference in density with aerated concrete blocks, good adhesion to aerated concrete blocks, good frost resistance, and various properties meet the JC 890-2001 standard for masonry and plastering mortars for autoclaved aerated concrete. No cracking was observed at low temperatures.

[0090] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. 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 or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. Aerated concrete masonry insulation mortar for low-temperature environmental use, characterized in that, The heat preservation mortar comprises the following raw materials in parts by weight: Low-carbon cementing material: 25-40 parts; Fine aggregate: 25-40 parts; Fly ash: 5-10 parts; Early strength agent: 0.2-1 part; Vitrified microbead: 10-25 parts; Anti-freezing agent: 0.2-2 parts; The low-carbon cementing material comprises limestone, low-grade bauxite, hard gypsum and sand, and the free calcium oxide content in the low-carbon cementing material is 15-35 wt.%, the anhydrous calcium sulphoaluminate content is 5-10 wt.%, the dicalcium silicate content is 40-55 wt.%, the anhydrous calcium sulphate content is 3-7 wt.% and the tetracalcium aluminoferrite content is 2-5 wt.%. The anti-freezing agent is a mixture of acrylic acid emulsion and ethylene glycol in a mass ratio of 1:(0.2-0.5). The low-carbon cementing material has a specific surface area of 380-420 m 2 / kg. The preparation method of the aerated concrete masonry heat preservation mortar for low-temperature environment comprises the following steps: Step 1, water is added to the low-carbon cementing material for hydration to obtain a slurry; the water-cement ratio is 0.5-0.6, the stirring time is 3-10 min and the stirring speed is 130-290 r / min; Step 2, the fine aggregate, fly ash, vitrified microbead, early strength agent and anti-freezing agent are added into the slurry and stirred uniformly to obtain the heat preservation mortar.

2. The low-temperature environment usable aerated concrete masonry thermal insulation mortar according to claim 1, characterized in that, The heat preservation mortar comprises the following raw materials in parts by weight: Low-carbon cementing material: 28-35 parts; Fine aggregate: 30-35 parts; Fly ash: 5-8 parts; Early strength agent: 0.2-0.8 part; Vitrified microbead: 15-22 parts; Anti-freezing agent: 0.5-1.5 parts; The low-carbon cementing material comprises limestone, low-grade bauxite, hard gypsum and sand, and the free calcium oxide content in the low-carbon cementing material is 18-30 wt.%, the anhydrous calcium sulphoaluminate content is 6-8 wt.%, the dicalcium silicate content is 40-45 wt.%, the anhydrous calcium sulphate content is 5-7 wt.% and the tetracalcium aluminoferrite content is 2-5 wt.%.

3. The low-temperature environment usable aerated concrete masonry thermal insulation mortar according to claim 1 or 2, characterized in that, The fine aggregate is one or both of sand and aerated concrete waste.

4. The low-temperature environment usable aerated concrete masonry thermal insulation mortar according to claim 1 or 2, characterized in that, The components with particle sizes less than 0.63 mm, in the range of 0.63-0.80 mm and in the range of 0.80-1.5 mm account for 20%, 40% and 40%, respectively.

5. The low-temperature environment usable aerated concrete masonry thermal insulation mortar according to claim 1 or 2, characterized in that, The early strength agent is one or both of calcium formate and lithium carbonate.

6. The low-temperature environment usable aerated concrete masonry thermal insulation mortar according to claim 1 or 2, characterized in that, The fly ash is Class I fly ash or Class II fly ash, and the components with particle sizes in the range of 3-15 μm account for not less than 33%.

7. The low-temperature environment usable aerated concrete masonry thermal insulation mortar according to claim 1, characterized in that, The preparation of the low-carbon cementing material comprises the following steps: Step a, limestone, low-grade bauxite, hard gypsum and sand are weighed, ground and mixed uniformly to obtain a mixture; Step b, the mixture is subjected to low-temperature calcination to obtain the low-carbon cementing material; the low-temperature calcination temperature is 1200-1350 ℃ and the calcination time is 30 min.

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