CN107500642B - Application of calcium silicate hydrate fibers in preparation of aerated concrete blocks - Google Patents

Application of calcium silicate hydrate fibers in preparation of aerated concrete blocks Download PDF

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CN107500642B
CN107500642B CN201710977020.8A CN201710977020A CN107500642B CN 107500642 B CN107500642 B CN 107500642B CN 201710977020 A CN201710977020 A CN 201710977020A CN 107500642 B CN107500642 B CN 107500642B
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calcium silicate
silicate hydrate
aerated concrete
slurry
fibers
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CN107500642A (en
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李光辉
姜涛
曹鹏旭
彭志伟
罗骏
张元波
饶明军
张鑫
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Central South University
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B14/38—Fibrous materials; Whiskers
    • C04B14/46—Rock wool ; Ceramic or silicate fibres
    • C04B14/4643—Silicates other than zircon
    • C04B14/465—Ca-silicate, e.g. wollastonite
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/20—Mortars, concrete or artificial stone characterised by specific physical values for the density
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Civil Engineering (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)

Abstract

The invention relates to an application of calcium silicate hydrate fibers in preparing aerated concrete blocks; belongs to the technical field of green energy-saving building materials. The invention uses calcium silicate hydrate fiber as additive for producing aerated concrete block; the calcium silicate hydrate fiber has a diameter of 0.01 to 0.5 μm and a length of 0.5 to 5 μm, and contains calcium and silicon in an atomic ratio of 0.5 to 2. Through a great deal of research, the inventor finds that the hydrated calcium silicate fiber with a determined structure is used as an mineralization inducer for the hydration process of aerated concrete, can induce the formation of tobermorite in the production process, and is beneficial to improving the comprehensive performance of products (aerated concrete blocks). The calcium silicate hydrate fiber used in the invention is a reaction product prepared by preparing slurry by utilizing a siliceous raw material and a calcareous raw material and carrying out hydrothermal synthesis on the slurry; the preparation process is simple and the cost is low; the formation of tobermorite in the product can be induced under the condition of low addition amount, so that the mechanical strength of the product is improved.

Description

Application of calcium silicate hydrate fibers in preparation of aerated concrete blocks
Technical Field
The invention relates to a method for preparing an aerated concrete block by using a calcium silicate hydrate fiber additive; belongs to the technical field of green energy-saving building materials.
Background
The aerated concrete block is a novel energy-saving building material which takes hydrated calcium silicate gel, tobermorite, water-flower garnet and the like as main components, is light and porous, has heat preservation and insulation, good fireproof performance, can be nailed, sawed and planed, and has certain anti-seismic performance. Generally, the compressive strength of the aerated concrete block is 2.5-5 MPa, and the volume weight is 500-700 kg/m3The masonry wall is generally used for a filler wall of a building, and the masonry with higher strength can also be used on an outer wall. The production process of aerated concrete building blocks is in EuropeThe united states, japan, and the like have reached maturity, and domestic production technologies are in the stage of overtaking western countries as a whole. At present, aerated concrete block products produced in China have the main problems of generally low strength of the blocks, serious corner drop and cracking phenomena and the like.
In order to overcome the defects of the existing aerated concrete block, the prior art mainly adds reinforcing fibers. For example, chinese patent publication No. CN102206095A discloses that the compressive strength and internal cracks of an aerated concrete block are improved by adding modified polypropylene fibers.
However, the uniform distribution of additives such as polypropylene fibers in the aerated concrete block is the key for improving the mechanical strength of the product, the addition amount and the medicament addition mode of the additives are strictly controlled, and the addition amount of the polypropylene fibers is too low to achieve the fiber reinforcement effect; and if the addition amount is too high, the polypropylene fibers are agglomerated, so that the compressive strength of the aerated concrete block is reduced. In addition, the polypropylene fiber is sensitive to sunlight and oxygen, is easy to deteriorate and decompose, and has weak bonding property with a cement matrix, so that the stability of the later strength of the aerated concrete block is influenced.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides the application of calcium silicate hydrate fibers in the preparation of aerated concrete blocks, and aims to improve the comprehensive performance of the aerated concrete blocks by using the calcium silicate hydrate fibers as an inducer (additive).
An application of calcium silicate hydrate fibers in preparing aerated concrete blocks, which are used as an inducer for generating tobermorite and are used for preparing the aerated concrete blocks.
Researches show that the strength of the aerated concrete block can be unexpectedly improved on the premise of reducing the volume weight of the aerated concrete block by adding the calcium silicate hydrate fiber into the casting slurry for preparing the aerated concrete block.
The process complexity of the production process of the aerated concrete block and the diversity of the structure and the type of the hydrated calcium silicate material enable the quality of the aerated concrete block product to be easily influenced by the production process. Through a great deal of research, the inventor finds that the hydrated calcium silicate fiber with a determined structure is used as an mineralization inducer for the hydration process of aerated concrete, can induce the formation of tobermorite in the production process, and is beneficial to improving the comprehensive performance of products (aerated concrete blocks).
Preferably, the diameter of the calcium silicate hydrate fiber is 0.01-0.5 μm; the length is 0.5 to 5 μm. The length-diameter ratio is preferably 10-100; more preferably 50 to 100. The inventor also researches and discovers that the adoption of the calcium silicate hydrate fiber with the optimal diameter and length range is beneficial to selectively inducing the generation of tobermorite, so that the performance of the prepared aerated concrete block is further improved, for example, the volume weight of the aerated concrete block is reduced, and the strength of the aerated concrete block is improved.
More preferably, the diameter of the calcium silicate hydrate fiber is 0.01-0.1 μm; the length is 1 to 3 μm.
Preferably, the calcium silicate hydrate fiber has a calcium silicon atomic ratio (element molar ratio) of 0.5 to 2. The calcium silicate hydrate within the calcium-silicon atomic ratio range has relatively stable structure and higher activity, and can obviously improve the generation of tobermorite in the product when being used as an additive for aerated concrete production, thereby improving the performances of the product such as mechanical strength, volume weight and the like.
More preferably, the calcium silicate hydrate fiber has a calcium-silicon atomic ratio of 0.6 to 1.0. The calcium silicate hydrate fibers in the optimal proportion are beneficial to further improving the performance of the aerated concrete block obtained subsequently.
The calcium silicate hydrate fiber is obtained by performing hydrothermal reaction on slurry prepared from a siliceous raw material, a calcareous raw material and water at the temperature of 150-220 ℃.
Through a large number of researches, the hydrothermal reaction is carried out in the temperature range, and the finally obtained calcium silicate hydrate fiber is particularly suitable for the additive for preparing aerated concrete blocks. Research shows that the compressive strength of the aerated concrete block can be obviously improved by adding the calcium silicate hydrate fiber prepared in the temperature range.
Preferably, the temperature of the hydrothermal reaction is 180 to 200 ℃. The hydrated calcium silicate fiber obtained by hydrothermal at the temperature is more beneficial to the improvement of the overall performance of the aerated concrete block.
The siliceous raw material can be quartz, fly ash, slag and other materials mainly containing silicon dioxide.
The calcareous raw materials can be lime, carbide slag and other materials mainly containing CaO.
The calcium silicate hydrate fiber used in the invention is prepared by taking siliceous raw materials such as quartz, fly ash and slag and calcareous raw materials such as lime and carbide slag as main raw materials (silicon-containing and calcareous raw materials for producing aerated concrete blocks) through a hydrothermal synthesis method; the principle is simple, the popularization and the application are easy, and the promotion of the quality improvement and the consumption reduction of energy-saving building material products is facilitated.
According to the method, the selected siliceous raw materials and the selected calcareous raw materials are all raw materials for synthesizing the aerated concrete block; the exogenous materials such as polypropylene fiber and the like commonly used in the prior art can not be introduced; the obtained aerated concrete block has more excellent performance.
The inventor further finds that the strength of the aerated concrete block product obtained subsequently is further improved by controlling a proper material ratio and the liquid-solid ratio of the system before the hydrothermal reaction and cooperating with the temperature and time conditions of the hydrothermal reaction.
Preferably, the molar ratio of calcium to silicon in the slurry is 0.2 to 1.0.
Preferably, the pH value of the slurry is 11-14; more preferably 12 to 13. The pH can be adjusted by conventional methods, for example, by adjusting the pH of the slurry with sodium hydroxide.
Preferably, the slurry has a liquid-solid ratio of 5 to 30 mL/g.
Under the hydrothermal condition, the appropriate hydrothermal reaction time is controlled, so that the application prospect of the obtained calcium silicate hydrate fibers in preparing the aerated concrete block can be further improved, and the performance of the prepared aerated concrete block is further improved.
Preferably, the hydrothermal reaction time is 0.1-2 h; more preferably 0.2 to 0.5 hour.
In the present invention, the hydrothermal reaction is carried out in a closed vessel. Under the hydrothermal condition, the pressure of the hydrothermal reaction is preferably 1.3MPa to 2.5 MPa.
The inventor also finds that the temperature, the pH value and the solid-liquid ratio in the hydrothermal reaction process are controlled in the preferable range, and the calcium silicate hydrate fibers which are more beneficial to induction of tobermorite and further improve the performance of the aerated concrete block can be obtained through the cooperation of the parameters.
The preferred preparation method of the calcium silicate hydrate fiber comprises the following steps: preparing a slurry from a siliceous raw material, a calcareous raw material and water according to a calcium-silicon molar ratio of 0.2-1.0 and a liquid-solid ratio of 5-30 mL/g, and adding 0-40 g/L NaOH to adjust the pH value of the slurry. Adding the prepared suspension slurry into a high-pressure closed container, and carrying out hydro-thermal synthesis under the conditions that the temperature is 180-200 ℃, the time is 0.2-0.5 h, and the stirring speed is 100-300 rpm.
After the hydrothermal reaction is finished, cooling the hydrothermal reaction liquid to room temperature, and then carrying out solid-liquid separation, washing and drying to obtain the calcium silicate hydrate fiber meeting the requirements.
The application of the invention comprises the steps of uniformly mixing the calcium silicate hydrate fibers with the casting slurry, and obtaining the aerated concrete block after the steps of moulding, static curing, cutting and autoclaved curing; the addition amount of the calcium silicate hydrate fiber is 0.1-20% of the weight of the casting slurry.
In the invention, calcium silicate hydrate fibers (preferably calcium silicate hydrate fibers obtained by the preparation method of the invention) are added into the conventional casting slurry; and then the conventional preparation method of the existing aerated concrete block is adopted to obtain the aerated concrete block with obviously improved strength.
The casting slurry mainly comprises at least one of fly ash, quartz powder or slag; and a slurry of cement, lime, gypsum and aluminum powder.
Preferably, the casting slurry comprises 50-75 parts by weight of at least one of quartz powder, slag or fly ash; 30-35 parts by weight of water; 2-5 parts by weight of gypsum; 5-10 parts by weight of cement; 10-15 parts by weight of lime; 0.05 to 0.1 part by weight of aluminum powder slurry.
The addition amount of the calcium silicate hydrate fiber is less than 0.1 percent, and the effect of the additive on improving the mechanical strength of the aerated concrete block product is not obvious; the addition amount exceeds 20 percent, and the mechanical strength of the aerated concrete block product is reduced when the relative addition amount is 0.1 to 20 percent.
Preferably, the addition amount of the calcium silicate hydrate fibers is 1-10% of the weight of the casting slurry; further preferably 1-5%; most preferably 3 to 5%.
According to the preferable application of the invention, according to the weight parts of the casting slurry, the fly ash (and/or quartz sand and slag), the gypsum and the water are prepared into the primary pulp in advance, and after the full stirring, the cement and the lime are added; and (3) stirring for 3-5 min, then adding 1-10% of calcium silicate hydrate fiber additive (based on the weight of the casting slurry) and aluminum powder, and finally performing mold framing, precuring, cutting and steam curing to obtain the aerated concrete block product.
The invention relates to a preferable application (preparation method of aerated concrete block), which comprises the following steps:
step (1):
preparing slurry according to the molar ratio of calcium to silicon of 0.2-1.0 and the liquid-solid ratio of 5-30 mL/g, and adding 5-40 g/L NaOH to adjust the pH value of the slurry; putting the obtained suspension slurry into a pressure reaction kettle, stirring and heating to 180-200 ℃, and reacting for 0.1-2 h at a constant temperature under the pressure of 1.3-2.0 MPa; after the reaction is finished, cooling the slurry to room temperature, taking out the slurry, and carrying out solid-liquid separation, washing and drying to obtain the calcium silicate hydrate fiber meeting the requirements;
step (2):
the content of the casting slurry (in parts by weight) is as follows: 50 parts of fly ash (and/or quartz sand and slag); 2.4 parts of gypsum; 32.5 parts of water; 5 parts of cement; 10 parts of quicklime; 0.1 part of aluminum powder;
preparing raw slurry from fly ash (and/or quartz sand and slag), gypsum and water according to the proportion of the casting slurry, fully stirring, and pumping into a casting stirrer by a mortar pump; then adding cement and lime; stirring for 3min, then sequentially adding 1-10% of calcium silicate hydrate fiber additive (prepared in step (1); based on the weight of the casting slurry) and aluminum powder, controlling the diffusivity to be 17cm, stirring for 50s, and discharging the slurry to a mold frame. Pre-curing, cutting and steam curing the blank to obtain the aerated concrete block product. The temperature and the humidity of the static curing chamber are respectively 50 ℃ and 80%, and the blank body behind the die frame is pre-cured for 2 hours; steam curing temperature and pressure are 185 ℃, 1.5MPa, and steam curing is carried out for 5 h. The temperature rise and temperature reduction time in the steam pressure curing process is controlled to be 2 hours.
The strength of the aerated concrete block obtained under the optimal laboratory conditions (small mold test, uneven gas generation) is 7.8MPa, and the volume weight is 805kg/m3。
The beneficial effects that can be obtained by adopting the invention are as follows:
the hydrated calcium silicate fiber is used as an additive for inducing the formation of tobermorite, the production process of the aerated concrete block is not changed, and the mechanical strength of the block product can be obviously improved and the quality of the product can be improved only by adding a small amount of the additive. The calcium silicate hydrate fiber additive has wide source and low cost, and can be obtained by hydrothermal synthesis of siliceous raw materials and calcareous raw materials for producing aerated concrete blocks.
According to the invention, the hydrated calcium silicate fiber is used as an inducer for forming tobermorite in the production process of the aerated concrete block, and the formation of the tobermorite is excited, so that the mechanical strength of the product is improved, the problem of low strength of the aerated concrete block in the prior art is solved, the technical development of the lightweight high-strength aerated concrete block product is promoted, the product quality is improved, and the market competitiveness of the product is increased.
Drawings
FIG. 1 is an XRD pattern of a block product of comparative example 1 of the present invention;
FIG. 2 is an XRD pattern of a block product of example 3 of the present invention;
FIG. 3 is an SEM image of a block product of comparative example 1 of the present invention;
FIG. 4 is an SEM image of a block product of example 3 of the present invention;
FIG. 5 is an SEM image of a calcium silicate hydrate fiber additive prepared in example 3 of the present invention.
As can be seen from fig. 1 and 2: the addition of calcium silicate hydrate fibers can promote the formation of tobermorite in concrete block products thereof. Because the autoclave curing temperature is lower, mullite and quartz in the fly ash are not completely decomposed.
As can be seen from fig. 3 and 4: under the condition without additives, almost no fibrous substances are formed on the fracture surface of the aerated concrete block product; 3 percent of calcium silicate hydrate fiber additive is added, so that the formation of tobermorite whiskers in the product can be induced, and the compressive strength of the building block product is improved.
As can be seen from fig. 5: the diameter of the prepared calcium silicate hydrate fiber is 0.01-0.1 mu m, the length is 1-3 mu m, the specific surface area is high, and the activity is high.
Detailed Description
Comparative example 1:
the content of the casting slurry (in parts by weight) is as follows: 50 parts of fly ash (and/or quartz sand and slag); 2.5 parts of gypsum; 32.5 parts of water; 5 parts of cement; 10 parts of quicklime; 0.1 part of aluminum powder;
preparing raw slurry from fly ash (and/or quartz sand and slag), gypsum and water according to the proportion of the casting slurry, fully stirring, and pumping into a casting stirrer by a mortar pump; then adding cement and lime; after stirring for 3min, aluminum powder was added with controlled diffusivity of 17cm, stirred for 50s, and the slurry was dropped into a mold. Pre-curing, cutting and steam curing the blank to obtain the aerated concrete block product. The temperature and the humidity of the static curing chamber are respectively 50 ℃ and 80%, and the blank body behind the die frame is pre-cured for 2 hours; controlling the temperature rise and temperature reduction time in the steam curing process to be 2h, controlling the steam curing temperature and pressure to be 185 ℃, and performing steam curing for 5h under the pressure of 1.5 MPa; obtaining the aerated concrete block. The main mineral compositions of the product are quartz, mullite and calcium silicate hydrate gel. The compressive strength of the building block product is 3.2MPa, and the volume weight is 620kg/m3。
Example 1:
step (1):
preparing slurry according to the molar ratio of calcium to silicon of 0.4 and the liquid-solid ratio of 15mL/g, and adding 20g/L NaOH to adjust the pH value (the pH value is 13) of the slurry; putting the obtained suspension slurry into a pressure reaction kettle, stirring and heating to 160 ℃, and reacting for 2 hours at a constant temperature under the pressure of 0.6 MPa; after the reaction is finished, cooling the slurry to room temperature, taking out the slurry, and obtaining a product (the hydrated calcium silicate fiber additive) after solid-liquid separation, washing and drying. The obtained product was subjected to XRD and SEM analysis. The main mineral compositions of the product are mullite, quartz and calcium silicate hydrate gel. The diameter of the calcium silicate hydrate fiber is 0.1-0.5 μm, the length is 1-5 μm, and the length-diameter ratio is 20-30; the calcium silicon atomic ratio of the calcium silicate hydrate fibers was 0.75.
Step (2):
the content of the casting slurry (in parts by weight) is as follows: 50 parts of fly ash (and/or quartz sand and slag); 2.5 parts of gypsum; 32.5 parts of water; 5 parts of cement; 10 parts of quicklime; 0.1 part of aluminum powder;
preparing raw slurry from fly ash (and/or quartz sand and slag), gypsum and water according to the proportion of the casting slurry, fully stirring, and pumping into a casting stirrer by a mortar pump; then adding cement and lime; after stirring for 3min, adding 3% calcium silicate hydrate fiber additive (prepared in step (1); based on the weight of the casting slurry) and aluminum powder in sequence, controlling the diffusivity to be 17cm, stirring for 50s, and discharging the slurry to a mold frame. Pre-curing, cutting and steam curing the blank to obtain the aerated concrete block product. The temperature and the humidity of the static curing chamber are respectively 50 ℃ and 80%, and the blank body behind the die frame is pre-cured for 2 hours; steam curing temperature and pressure are 185 ℃, 1.5MPa, and steam curing is carried out for 5 hours, thus obtaining the aerated concrete block. The temperature rise and temperature reduction time in the steam pressure curing process is controlled to be 2 hours. The main mineral compositions of the product are quartz, mullite, calcium silicate hydrate gel and tobermorite. The compressive strength of the building block product is 4.3MPa, and the volume weight is 634kg/m3。
Example 2:
step (1):
preparing slurry according to the molar ratio of calcium to silicon of 0.8 and the liquid-solid ratio of 25mL/g, and adding 10g/L NaOH to adjust the pH value (the pH value is 13) of the slurry; putting the obtained suspension slurry into a pressure reaction kettle, stirring and heating to 180 ℃, and reacting for 1.0h at a constant temperature under the pressure of 1.3 MPa; after the reaction is finished, cooling the slurry to room temperature, taking out the slurry, and obtaining a product (the hydrated calcium silicate fiber additive) after solid-liquid separation, washing and drying. The obtained product was subjected to XRD and SEM analysis. The main phases of the product are mullite, quartz, tobermorite and calcium silicate hydrate gel. The diameter of the calcium silicate hydrate fiber is 0.01-0.1 μm, the length is 3-5 μm, and the length-diameter ratio is 50-100; the calcium silicon atomic ratio of the calcium silicate hydrate fibers was 0.75.
Step (2):
the content of the casting slurry (in parts by weight) is as follows: 50 parts of fly ash (and/or quartz sand and slag); 2.5 parts of gypsum; 32.5 parts of water; 5 parts of cement; 10 parts of quicklime; 0.1 part of aluminum powder;
preparing raw slurry from fly ash (and/or quartz sand and slag), gypsum and water according to the proportion of the casting slurry, fully stirring, and pumping into a casting stirrer by a mortar pump; then adding cement and lime; after stirring for 3min, adding 3% calcium silicate hydrate fiber additive (prepared in step (1); based on the weight of the casting slurry) and aluminum powder in sequence, controlling the diffusivity to be 17cm, stirring for 50s, and discharging the slurry to a mold frame. Pre-curing, cutting and steam curing the blank to obtain the aerated concrete block product. The temperature and the humidity of the static curing chamber are respectively 50 ℃ and 80%, and the blank body behind the die frame is pre-cured for 2 hours; steam curing at 185 deg.C under 1.5MPa for 5 hr; obtaining the aerated concrete block. The temperature rise and temperature reduction time in the steam pressure curing process is controlled to be 2 hours. The main mineral compositions of the product are quartz, mullite, calcium silicate hydrate gel and tobermorite. The compressive strength of the building block product is 6.5MPa, and the volume weight is 716kg/m3。
Example 3:
step (1):
preparing slurry according to the molar ratio of calcium to silicon of 1.0 and the liquid-solid ratio of 20mL/g, and adding 5g/L NaOH to adjust the pH value (the pH value is 12) of the slurry; putting the obtained suspension slurry into a pressure reaction kettle, stirring and heating to 200 ℃, and reacting for 0.5h at a constant temperature under the pressure of 1.3 MPa; after the reaction is finished, cooling the slurry to room temperature, taking out the slurry, and obtaining a product (the hydrated calcium silicate fiber additive) after solid-liquid separation, washing and drying. The obtained product was subjected to XRD and SEM analysis. The main phases of the product are mullite, quartz, calcium silicate hydrate gel and tobermorite. The diameter of the calcium silicate hydrate fiber is 0.01-0.1 μm, the length is 1-3 μm, and the length-diameter ratio is 50-100; the calcium silicon atomic ratio of the calcium silicate hydrate fibers was 0.75.
Step (2):
the content of the casting slurry (in parts by weight) is as follows: 50 parts of fly ash (and/or quartz sand and slag); 2.5 parts of gypsum; 32.5 parts of water; 5 parts of cement; 10 parts of quicklime; 0.1 part of aluminum powder;
preparing raw slurry from fly ash (and/or quartz sand and slag), gypsum and water according to the proportion of the casting slurry, fully stirring, and pumping into a casting stirrer by a mortar pump; then adding cement and lime; after stirring for 3min, adding 3% calcium silicate hydrate fiber additive (prepared in step (1); based on the weight of the casting slurry) and aluminum powder in sequence, controlling the diffusivity to be 17cm, stirring for 50s, and discharging the slurry to a mold frame. Pre-curing, cutting and steam curing the blank to obtain the aerated concrete block product. The temperature and the humidity of the static curing chamber are respectively 50 ℃ and 80%, and the blank body behind the die frame is pre-cured for 2 hours; steam curing at 185 deg.C under 1.5MPa for 5 hr; obtaining the aerated concrete block. The temperature rise and temperature reduction time in the steam pressure curing process is controlled to be 2 hours. The main mineral compositions of the product are quartz, mullite, calcium silicate hydrate gel and tobermorite. The compressive strength of the building block product is 7.8MPa, and the volume weight is 805kg/m3。
Example 4:
the comparative test discusses the influence of the temperature of the calcium silicate hydrate fiber additive in the preparation process on the finally obtained performance, which is specifically as follows:
step (1):
preparing slurry according to the molar ratio of calcium to silicon of 1.2 and the liquid-solid ratio of 20mL/g, and adding 40g/L NaOH to adjust the pH value (the pH value is 14) of the slurry; putting the obtained suspension slurry into a pressure reaction kettle, stirring and heating to 220 ℃, and reacting for 2 hours at a constant temperature under the pressure of 2.5 MPa; after the reaction is finished, cooling the slurry to room temperature, taking out the slurry, and obtaining a product (the hydrated calcium silicate fiber additive) after solid-liquid separation, washing and drying. The obtained product was subjected to XRD and SEM analysis. The main phases of the product are mullite, hydrated garnet and tobermorite. The diameter of the calcium silicate hydrate fiber is 0.1-0.5 μm, the length is 1-2 μm, and the length-diameter ratio is 10-20; the calcium silicon atomic ratio of the hydrated calcium silicate fiber is 1.5.
Step (2):
the content of the casting slurry (in parts by weight) is as follows: 50 parts of fly ash (and/or quartz sand and slag); 2.5 parts of gypsum; 32.5 parts of water; 5 parts of cement; 10 parts of quicklime; 0.1 part of aluminum powder;
preparing raw slurry from fly ash (and/or quartz sand and slag), gypsum and water according to the proportion of the casting slurry, fully stirring, and pumping into a casting stirrer by a mortar pump; then adding cement and lime; after stirring for 3min, adding 3% calcium silicate hydrate fiber additive (prepared in step (1); based on the weight of the casting slurry) and aluminum powder in sequence, controlling the diffusivity to be 17cm, stirring for 50s, and discharging the slurry to a mold frame. Pre-curing, cutting and steam curing the blank to obtain the aerated concrete block product. The temperature and the humidity of the static curing chamber are respectively 50 ℃ and 80%, and the blank body behind the die frame is pre-cured for 2 hours; steam curing at 185 deg.C under 1.5MPa for 5 hr; obtaining the aerated concrete block. The temperature rise and temperature reduction time in the steam pressure curing process is controlled to be 2 hours. The main mineral compositions of the product are quartz, mullite, calcium silicate hydrate gel, tobermorite and garnet hydrate. The compressive strength of the building block product is 3.5MPa, and the volume weight is 652kg/m3。
Example 5:
the comparative test discusses the influence of smaller addition of the calcium silicate hydrate fiber additive on the performance of the prepared building block product, and specifically comprises the following steps:
step (1):
preparing slurry according to the molar ratio of calcium to silicon of 1.0 and the liquid-solid ratio of 20mL/g, and adding 5g/L NaOH to adjust the pH value (the pH value is 12) of the slurry; putting the obtained suspension slurry into a pressure reaction kettle, stirring and heating to 200 ℃, and reacting for 0.5h at a constant temperature under the pressure of 1.3 MPa; after the reaction is finished, cooling the slurry to room temperature, taking out the slurry, and obtaining a product (the hydrated calcium silicate fiber additive) after solid-liquid separation, washing and drying. The obtained product was subjected to XRD and SEM analysis. The main phases of the product are mullite, quartz, calcium silicate hydrate gel and tobermorite. The diameter of the calcium silicate hydrate fiber is 0.01-0.1 μm, the length is 1-2 μm, and the length-diameter ratio is 50-100; the calcium silicon atomic ratio of the calcium silicate hydrate fibers was 0.75.
Step (2):
the content of the casting slurry (in parts by weight) is as follows: 50 parts of fly ash (and/or quartz sand and slag); 2.5 parts of gypsum; 32.5 parts of water; 5 parts of cement; 10 parts of quicklime; 0.1 part of aluminum powder;
preparing raw slurry from fly ash (and/or quartz sand and slag), gypsum and water according to the proportion of the casting slurry, fully stirring, and pumping into a casting stirrer by a mortar pump; then adding cement and lime; after stirring for 3min, 0.01% calcium silicate hydrate fiber additive (prepared in step (1); based on the weight of the casting slurry) and aluminum powder were added in sequence, the degree of diffusion was controlled at 17cm, stirring was carried out for 50s, and the slurry was dropped into a mold. Pre-curing, cutting and steam curing the blank to obtain the aerated concrete block product. The temperature and the humidity of the static curing chamber are respectively 50 ℃ and 80%, and the blank body behind the die frame is pre-cured for 2 hours; steam curing at 185 deg.C under 1.5MPa for 5 hr; obtaining the aerated concrete block. The temperature rise and temperature reduction time in the steam pressure curing process is controlled to be 2 hours. The main mineral compositions of the product are quartz, mullite and calcium silicate hydrate gel. The compressive strength of the building block product is 3.3MPa, and the volume weight is 605kg/m3。
Example 6:
the comparative test discusses the influence of the larger addition amount of the calcium silicate hydrate fiber additive on the performance of the prepared building block product, which is specifically as follows:
step (1):
preparing slurry according to the molar ratio of calcium to silicon of 1.0 and the liquid-solid ratio of 20mL/g, and adding 5g/L NaOH to adjust the pH value (the pH value is 12) of the slurry; putting the obtained suspension slurry into a pressure reaction kettle, stirring and heating to 200 ℃, and reacting for 0.5h at a constant temperature under the pressure of 1.3 MPa; after the reaction is finished, cooling the slurry to room temperature, taking out the slurry, and obtaining a product (the hydrated calcium silicate fiber additive) after solid-liquid separation, washing and drying. The obtained product was subjected to XRD and SEM analysis. The main phases of the product are mullite, quartz, calcium silicate hydrate gel and tobermorite. The diameter of the calcium silicate hydrate fiber is 0.01-0.1 μm, the length is 1-2 μm, and the length-diameter ratio is 50-100; the calcium silicon atomic ratio of the calcium silicate hydrate fibers was 0.75.
Step (2):
the content of the casting slurry (in parts by weight) is as follows: 50 parts of fly ash (and/or quartz sand and slag); 2.5 parts of gypsum; 32.5 parts of water; 5 parts of cement; 10 parts of quicklime; 0.1 part of aluminum powder;
preparing raw slurry from fly ash (and/or quartz sand and slag), gypsum and water according to the proportion of the casting slurry, fully stirring, and pumping into a casting stirrer by a mortar pump; then adding cement and lime; after stirring for 3min, sequentially adding 1% calcium silicate hydrate fiber additive (prepared in step (1); based on the weight of the casting slurry) and aluminum powder, controlling the diffusivity to be 17cm, stirring for 50s, and discharging the slurry to a mold frame. Pre-curing, cutting and steam curing the blank to obtain the aerated concrete block product. The temperature and the humidity of the static curing chamber are respectively 50 ℃ and 80%, and the blank body behind the die frame is pre-cured for 2 hours; steam curing at 185 deg.C under 1.5MPa for 5 hr; obtaining the aerated concrete block. The temperature rise and temperature reduction time in the steam pressure curing process is controlled to be 2 hours. The main mineral compositions of the product are quartz, mullite, tobermorite and calcium silicate hydrate gel. The compressive strength of the building block product is 5.3MPa, and the volume weight is 706kg/m3。
Example 7:
the comparative test discusses the influence of the larger addition amount of the calcium silicate hydrate fiber additive on the performance of the prepared building block product, which is specifically as follows:
step (1):
preparing slurry according to the molar ratio of calcium to silicon of 1.0 and the liquid-solid ratio of 20mL/g, and adding 5g/L NaOH to adjust the pH value (the pH value is 12) of the slurry; putting the obtained suspension slurry into a pressure reaction kettle, stirring and heating to 200 ℃, and reacting for 0.5h at a constant temperature under the pressure of 1.3 MPa; after the reaction is finished, cooling the slurry to room temperature, taking out the slurry, and obtaining a product (the hydrated calcium silicate fiber additive) after solid-liquid separation, washing and drying. The obtained product was subjected to XRD and SEM analysis. The main phases of the product are mullite, quartz, calcium silicate hydrate gel and tobermorite. The diameter of the calcium silicate hydrate fiber is 0.01-0.1 μm, the length is 1-2 μm, and the length-diameter ratio is 50-100; the calcium silicon atomic ratio of the calcium silicate hydrate fibers was 0.75.
Step (2):
the content of the casting slurry (in parts by weight) is as follows: 50 parts of fly ash (and/or quartz sand and slag); 2.5 parts of gypsum; 32.5 parts of water; 5 parts of cement; 10 parts of quicklime; 0.1 part of aluminum powder;
preparing raw slurry from fly ash (and/or quartz sand and slag), gypsum and water according to the proportion of the casting slurry, fully stirring, and pumping into a casting stirrer by a mortar pump; then adding cement and lime; after stirring for 3min, adding 10% calcium silicate hydrate fiber additive (prepared in step (1); based on the weight of the casting slurry) and aluminum powder in sequence, controlling the diffusivity to be 17cm, stirring for 50s, and discharging the slurry to a mold frame. Pre-curing, cutting and steam curing the blank to obtain the aerated concrete block product. The temperature and the humidity of the static curing chamber are respectively 50 ℃ and 80%, and the blank body behind the die frame is pre-cured for 2 hours; steam curing at 185 deg.C under 1.5MPa for 5 hr; obtaining the aerated concrete block. The temperature rise and temperature reduction time in the steam pressure curing process is controlled to be 2 hours. The main mineral compositions of the product are quartz, mullite, tobermorite and calcium silicate hydrate gel. The compressive strength of the building block product is 7.2MPa, and the volume weight is 820kg/m3。
Example 8:
the comparative test discusses the influence of the larger addition amount of the calcium silicate hydrate fiber additive on the performance of the prepared building block product, which is specifically as follows:
step (1):
preparing slurry according to the molar ratio of calcium to silicon of 1.0 and the liquid-solid ratio of 20mL/g, and adding 5g/L NaOH to adjust the pH value (the pH value is 12) of the slurry; putting the obtained suspension slurry into a pressure reaction kettle, stirring and heating to 200 ℃, and reacting for 0.5h at a constant temperature under the pressure of 1.3 MPa; after the reaction is finished, cooling the slurry to room temperature, taking out the slurry, and obtaining a product (the hydrated calcium silicate fiber additive) after solid-liquid separation, washing and drying. The obtained product was subjected to XRD and SEM analysis. The main phases of the product are mullite, quartz, calcium silicate hydrate gel and tobermorite. The diameter of the calcium silicate hydrate fiber is 0.01-0.1 μm, the length is 1-2 μm, and the length-diameter ratio is 50-100; the calcium silicon atomic ratio of the calcium silicate hydrate fibers was 0.75.
Step (2):
the content of the casting slurry (in parts by weight) is as follows: 50 parts of fly ash (and/or quartz sand and slag); 2.5 parts of gypsum; 32.5 parts of water; 5 parts of cement; 10 parts of quicklime; 0.1 part of aluminum powder;
preparing raw slurry from fly ash (and/or quartz sand and slag), gypsum and water according to the proportion of the casting slurry, fully stirring, and pumping into a casting stirrer by a mortar pump; then adding cement and lime; after stirring for 3min, 20% calcium silicate hydrate fiber additive (prepared in step (1); based on the weight of the casting slurry) and aluminum powder were added in sequence, the degree of diffusion was controlled at 17cm, stirring was carried out for 50s, and the slurry was dropped into a mold frame. Pre-curing, cutting and steam curing the blank to obtain the aerated concrete block product. The temperature and the humidity of the static curing chamber are respectively 50 ℃ and 80%, and the blank body behind the die frame is pre-cured for 2 hours; steam curing at 185 deg.C under 1.5MPa for 5 hr; obtaining the aerated concrete block. The temperature rise and temperature reduction time in the steam pressure curing process is controlled to be 2 hours. The main mineral compositions of the product are quartz, mullite, tobermorite and calcium silicate hydrate gel. The compressive strength of the building block product is 4.8MPa, and the volume weight is 755kg/m3。
Analysis of the results
The comprehensive comparison of the preparation processes of the calcium silicate hydrate fiber additives in examples 1 to 4 shows that calcium silicate hydrate fibers of different types and crystal morphologies can be prepared by adjusting the initial conditions of the synthesized calcium silicate hydrate fibers, and when the hydrothermal synthesis temperature, the calcium-silicon molar ratio, the NaOH concentration and the like are in the synergistic optimal range, the calcium-silicon atomic ratio of the synthesized calcium silicate hydrate fibers is 0.75, and the calcium-silicon atomic ratio reaches or approaches to that of tobermorite molecules; then properly controlling the hydrothermal reaction time within a preferable range to obtain calcium silicate hydrate fibers with fine crystal size; the prepared calcium silicate hydrate fiber additive has the characteristics of small diameter and length, large specific surface area, high activity and the like.
Through comparison between examples 1-8 and comparative example 1, the calcium silicate hydrate fiber prepared by the method disclosed by the invention is added into casting slurry produced by aerated concrete blocks, so that formation of tobermorite in the aerated concrete blocks can be induced, and the mechanical strength of the product can be improved. Particularly, when the temperature of the hydrothermal reaction is controlled to be 180-200 ℃, and the pH of the hydrothermal reaction is controlled to be 12-13 (examples 2 and 3), the performance of the obtained building block product is better.
In addition, it was found that the additive obtained by hydrothermal temperature higher than 200 ℃ (example 4) or lower than 180 ℃ (example 1) has limited effect on improving the performance of the block product.
The inventor also discusses the influence of the additive amount on the performance of the building block product; it was found that the effect of improving the performance of the block product was limited when the amount of the additive was small (example 5), and the performance of the block product was improved with the increase of the amount of the additive, but the performance was rather reduced when the amount of the additive was 10% or more (example 8). The proper addition amount of the calcium silicate hydrate fibers has a promoting effect on the improvement effect of the mechanical strength of the aerated concrete block.

Claims (11)

1. The application of the calcium silicate hydrate fiber in the preparation of the aerated concrete block is characterized in that the calcium silicate hydrate fiber is used as an inducer for generating tobermorite and is used for preparing the aerated concrete block;
the diameter of the calcium silicate hydrate fiber is 0.01-0.5 mu m, and the length of the calcium silicate hydrate fiber is 0.5-5 mu m;
the calcium silicon atomic ratio of the calcium silicate hydrate fiber is 0.5-2.
2. The use of calcium silicate hydrate fibers as claimed in claim 1 for the preparation of aerated concrete blocks, wherein the diameter of the calcium silicate hydrate fibers is 0.01 to 0.1 μm; the length is 1 to 3 μm.
3. The use of calcium silicate hydrate fibers as claimed in claim 2 for the preparation of aerated concrete blocks, wherein the calcium to silicon atomic ratio is 0.6 to 1.0.
4. The application of calcium silicate hydrate fibers in preparing aerated concrete blocks according to any one of claims 1 to 3, wherein the calcium silicate hydrate fibers are prepared from slurry prepared from a siliceous raw material, a calcareous raw material and water under the hydrothermal condition of 150-220 ℃.
5. The use of calcium silicate hydrate fibers according to claim 4 in the preparation of aerated concrete blocks, wherein the molar ratio of calcium to silicon in the slurry is 0.2 to 1.0.
6. The use of calcium silicate hydrate fibers as claimed in claim 5 for the preparation of aerated concrete blocks, wherein the slurry has a pH of 11 to 14; the liquid-solid ratio is 5-30 mL/g.
7. The application of calcium silicate hydrate fibers in preparing aerated concrete blocks according to claim 6, wherein the hydrothermal reaction time is 0.1-2 h.
8. The application of the calcium silicate hydrate fibers in preparing the aerated concrete block according to any one of claims 1 to 7, wherein the aerated concrete block is obtained by uniformly mixing the calcium silicate hydrate fibers with the casting slurry, and performing mold frame, static curing, cutting and autoclaved curing; the addition amount of the calcium silicate hydrate fiber is 0.1-20% of the weight of the casting slurry.
9. The use of calcium silicate hydrate fibers as claimed in claim 8 in the preparation of aerated concrete blocks, wherein the amount of calcium silicate hydrate fibers added is 1-10% by weight of the casting paste.
10. Use of calcium silicate hydrate fibers according to claim 8 for the preparation of aerated concrete blocks, wherein the casting slurry is a slurry consisting essentially of at least one of fly ash, quartz powder or slag; and a slurry of cement, lime, gypsum and aluminum powder.
11. The use of calcium silicate hydrate fibers in the preparation of aerated concrete blocks according to claim 10, wherein the casting slurry comprises 50 to 75 parts by weight of at least one of quartz powder, slag or fly ash; 30-35 parts by weight of water; 2-5 parts by weight of gypsum; 5-10 parts by weight of cement; 10-15 parts by weight of lime; 0.05 to 0.1 part by weight of aluminum powder slurry.
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