CN114044635A - Composite cement, cement prefabricated member, preparation method and application thereof - Google Patents

Composite cement, cement prefabricated member, preparation method and application thereof Download PDF

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CN114044635A
CN114044635A CN202111348012.XA CN202111348012A CN114044635A CN 114044635 A CN114044635 A CN 114044635A CN 202111348012 A CN202111348012 A CN 202111348012A CN 114044635 A CN114044635 A CN 114044635A
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cement
particles
composite
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water
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刘阳
王军
蒋震
向佳瑜
曾维
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China West Construction Group Co Ltd
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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
    • C04B7/00—Hydraulic cements
    • C04B7/02—Portland cement
    • 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
    • C04B7/00—Hydraulic cements
    • C04B7/02—Portland cement
    • C04B7/06—Portland cement using alkaline raw materials
    • 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
    • C04B7/00—Hydraulic cements
    • C04B7/24—Cements from oil shales, residues or waste other than slag
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D11/00—Control of flow ratio
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding

Abstract

The invention discloses composite cement, a cement prefabricated member, a preparation method and application thereof, wherein the preparation raw materials of the composite cement are inert powder particles and cement clinker particles; wherein the particle size of the inert powder particles is larger than that of the cement clinker particles, and the mass fraction of the inert powder particles in the composite cement is 35-75%. The composite cement of the invention selects inert powder (limestone powder or quartz powder) as the skeleton of the composite cement, and the resource source is wide. The addition of the inert powder reduces the consumption of cement, is beneficial to saving cost and effectively reduces the emission of carbon dioxide.

Description

Composite cement, cement prefabricated member, preparation method and application thereof
Technical Field
The invention relates to the technical field of building materials, in particular to composite cement, a cement prefabricated member, and a preparation method and application thereof.
Background
Cement is the most used building material in the world, and billions of tons of cement are produced and made into concrete for engineering every year. However, in the modern society advocating sustainable development, a series of environmental problems caused by the continuous increase of the cement amount have to be paid attention. The process of producing cement is accompanied by the emission of large amounts of carbon dioxide, which account for about 7% of the total amount of artificial carbon dioxide emissions. Therefore, research into environmental problems in cement and concrete applications is highly needed and urgent, and the cement industry is being promoted to lower carbonation and green color.
Aiming at the problem of carbon dioxide emission in cement and concrete application, the following method is mainly adopted to improve the utilization efficiency of cement. To reduce the amount of cement clinker used, one effective method is to replace the cement with a supplementary cementitious material. Typical supplementary cementitious materials include active materials such as fly ash, blast furnace slag and calcined clay, but in some cases inert materials such as limestone powder are also used as filler materials. On the other hand, the key for improving the utilization efficiency of the cement is to optimize the mix proportion design so as to increase the hydration degree of the cement. The increase of the utilization efficiency of cement is advantageous to improve the strength grade of concrete, reduce the excessive material consumption, and improve the durability of the composite cement for a prolonged service life. Meanwhile, porosity is an important parameter for determining strength, permeability, durability, etc. of the cement. By reducing the initial water-cement ratio of the slurry formation, the interparticle voids that need to be filled with hydration products can be reduced, resulting in a hardened slurry with low porosity.
To date, various High strength composite cements have been developed based on the theory of particle close packing, such as highly dense with Small cement based homogeneous systems (DSP), Reactive Powder Concrete (RPC), Ultra-High Performance Concrete (UHPC), and the like.
The traditional compact stacking cement-based material (including DSP, RPC, UHPC and the like) is characterized in that the consumption of cement and superfine powder is large, the stacking compactness of the system is high, but the cement hydration is insufficient and the hydration degree is low due to small water cement ratio. Taking UHPC as an example, the water-solid ratio is 0.14-0.20, the hydration degree of the cement is only 30% -40%, most of the cement cannot be fully hydrated and only plays the role of a filler, and the use efficiency of the cement is very low. Meanwhile, the cement consumption and the superfine active powder consumption of the traditional stacking material are large, and the carbon emission in the production process is large.
Therefore, it is required to develop a composite cement with which a cement preform having high compressive strength can be obtained.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides the composite cement, and the cement prefabricated member prepared from the composite cement has high compressive strength.
The invention also provides a preparation method of the composite cement.
The invention also provides the application of the composite cement.
The invention also provides a cement prefabricated member.
The invention also provides a preparation method of the cement prefabricated member.
The invention also provides an application of the cement prefabricated member.
The invention provides composite cement in a first aspect, wherein the preparation raw materials of the composite cement are inert powder particles and cement clinker particles;
wherein the particle size of the inert powder particles is larger than that of the cement clinker particles, and the mass fraction of the inert powder particles in the composite cement is 35-75%;
the inert powder particles comprise at least one of limestone powder and quartz powder.
According to some embodiments of the invention, the inert powder particles further comprise silica fume particles.
According to some embodiments of the invention, the silica fume particles are present in the composite cement in a mass fraction of between 2% and 4%.
According to some embodiments of the invention, the silica fume particles are present in the composite cement in a mass fraction of between 3% and 4%.
According to some embodiments of the invention, the mass fraction of the cement clinker particles in the composite cement is between 20% and 40%.
According to some embodiments of the invention, the mass fraction of the cement clinker particles in the composite cement is between 25% and 40%.
According to some embodiments of the invention, the mass fraction of the cement clinker particles in the composite cement is between 25% and 30%.
According to some embodiments of the invention, the mass fraction of the limestone powder in the composite cement is 60% to 80%.
According to some embodiments of the invention, the mass fraction of the limestone powder in the composite cement is 60% to 75%.
According to some embodiments of the invention, the mass fraction of the limestone powder in the composite cement is 60% to 72%.
According to some embodiments of the invention, the mass fraction of the limestone powder in the composite cement is 67% to 72%.
According to some embodiments of the invention, the silica fume particles have a D50 of 0.1 μm to 0.2 μm.
According to some embodiments of the invention, the silica fume particles have a specific surface area of 25m2More than g.
According to some embodiments of the invention, the silica fume particles have a specific surface area of 29m2More than g.
According to some embodiments of the invention, the silica fume particles have a specific surface area of 29m2/g～30m2/g。
According to some embodiments of the invention, the mass ratio of the silica fume to the cement plastic particles is 2-4: 100.
According to some embodiments of the invention, the mass ratio of the silica fume to the cement plastic particles is 3: 100.
According to some embodiments of the invention, the inert powder particles have a D50 of 10 to 20 μm.
According to some embodiments of the invention, the cement clinker particles have a D50 of between 3 μm and 5 μm.
According to some embodiments of the invention, the inert powder particles have a D50 of 10 to 15 μm.
According to some embodiments of the invention, the cement clinker particles have a D50 of between 3 μm and 4 μm.
According to some embodiments of the invention, the water cement ratio of the composite cement is less than 0.4.
According to some embodiments of the invention, the water cement ratio of the composite cement is 0.2 to 0.35.
According to some embodiments of the invention, the water cement ratio of the composite cement is 0.26 to 0.35.
According to some embodiments of the invention, the cement clinker particles are portland cement clinker particles.
According to some embodiments of the invention, the portland cement is grade 42.5.
According to some embodiments of the invention, the specific surface area of the cement clinker particles is 2.5m2More than g.
According to some embodiments of the invention, the specific surface area of the cement clinker particles is 2.6m2More than g.
According to some embodiments of the invention, the specific surface area of the cement clinker particles is 2.6m2/g～3.0m2/g。
According to some embodiments of the invention, the specific surface area of the cement clinker particles is 2.6m2/g～2.7m2/g。
According to some embodiments of the invention, the specific surface area of the composite cement is 1.0m2More than g.
According to some embodiments of the invention, the specific surface area of the composite cement is 1.0m2/g～1.5m2/g。
According to some embodiments of the invention, the specific surface area of the composite cement is 1.0m2/g～1.1m2/g。
The second aspect of the invention provides a preparation method of the composite cement, which comprises the following steps: and mixing the cement plastic particles with the inert powder particles to obtain the cement plastic powder.
The third aspect of the invention provides the application of the composite cement in preparing concrete materials and/or cement prefabricated members.
The invention provides a cement prefabricated member, and the preparation raw materials comprise the composite cement.
According to some embodiments of the invention, the compressive strength of the cement preform is above 80MPa (90 days hydration).
According to some embodiments of the invention, the compressive strength of the cement preform is above 90MPa (90 days of hydration).
According to some embodiments of the invention, the compressive strength of the cement preform is between 80MPa and 120MPa (90 days of hydration).
According to some embodiments of the invention, the compressive strength of the cement preform is between 90MPa and 120MPa (hydrated for 90 days).
According to some embodiments of the invention, the flexural strength of the cement preform is above 15Mpa (hydrated for 90 days).
According to some embodiments of the invention, the flexural strength of the cement preform is between 15MPa and 30MPa (hydration for 90 days).
The fifth aspect of the present invention provides a method for preparing the above cement preform, comprising the steps of:
and mixing the inert powder particles and the cement clinker particles to prepare slurry, and hardening to obtain the cement clinker.
According to some embodiments of the invention, the water-to-gel ratio of the slurry is 0.12 to 0.15.
According to some embodiments of the invention, the water-to-gel ratio of the slurry is 0.12 to 0.13. According to some embodiments of the invention, the hardening time is between 12h and 30 h.
The invention also provides the application of the cement prefabricated member in preparing building materials.
The reverse filling means that inert particles with larger particle size such as limestone powder form the main part of the system and form an initial skeleton. The superfine portland cement particles with small particle size fill the gaps in the framework, so that the initial stacking compactness is further improved. As the cement hydration reaction proceeds, the resulting hydration products fill the packing voids.
According to at least one embodiment of the present invention, the following advantageous effects are provided:
the composite cement of the invention selects inert powder (limestone powder or quartz powder) as the skeleton of the composite cement, and the resource source is wide. The addition of the inert powder reduces the consumption of cement, is beneficial to saving cost and effectively reduces the emission of carbon dioxide.
The composite cement of the invention further fills the large-particle filling material with the ultrafine cement clinker particles, thereby reducing the gaps among the particles to a greater extent. Compared with the prior art, the stacking compactness is further improved. As the voids are more filled, the porosity is reduced and the durability of the structure is improved.
The higher effective water cement ratio of the composite cement of the invention is beneficial to improving the hydration degree of the cement when the slurry is formed. The greatly improved hydration degree of the cement shows that the utilization efficiency of the cement is greatly improved, and the cement consumption is greatly saved.
The invention adopts a reverse dense stacking system to construct a cementing material system with low cost, low pollution and high durability.
Drawings
FIG. 1 is a graph showing the compressive strength of a cement preform in an embodiment of the present invention.
FIG. 2 is a graph showing the flexural strength of a cement preform in an embodiment of the present invention.
FIG. 3 is a graph comparing the compressive strength of cement preforms in examples 2 and 8 of the present invention.
FIG. 4 is a graph comparing the compressive strength of cement preforms in examples 3 and 9 of the present invention.
FIG. 5 is a back-scattered image of the initial state of the cement preform in example 2 of the present invention.
FIG. 6 is a backscatter image of a cement preform hydrated for 90 days in example 2 of the present invention.
Detailed Description
The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.
In the description of the present invention, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Specific examples of the present invention are described in detail below.
The construction method of the composite cement in the embodiment of the invention comprises the following steps:
s1, selecting materials:
the raw material of the reverse filling gelling system comprises a gelling component, namely limestone powder with large particle size and superfine cement clinker particles with small particle size, and a small amount of superfine silica fume particles (the particle size of the silica fume is 0.15 mu m) are doped.
In the embodiment of the invention, powder (limestone powder or quartz powder) with the fineness equivalent to that of ordinary cement is selected as a framework, ultrafine cement clinker particles with finer particles are selected as filling materials, and cement particles with smaller particle size are used for filling the stacking gaps of the framework powder with larger particle size. The median particle diameters D50 of the skeleton powder and the superfine cement clinker particles are 14.4 μm and 3.9 μm respectively, and the two components are mixed to form a binary gel system.
S2, calculating the packing compactness:
in order to obtain a dense packing structure, the packing compactness of the mixed powder was calculated using a Compressible Packing Model (CPM).
Firstly, the minimum water demand method is required to be used for measuring the stacking compactness of a single powder, and the minimum water demand method is a method which is proposed by the French road and bridge test center (LCPC) and is used for measuring the actual stacking compactness of a powder particle system. The test determines the degree of compaction by determining the voids between the particles, the volume of which is determined by the instantaneous water demand (called the "minimum water demand") at which the powder transforms from the solid state to the slurry state. The experiment assumed that the minimum water demand for the powder from solids to slurry just filled the voids between the granules, and that the slurry contained no air, i.e. the minimum water demand volume was equal to the volume of the voids between the granules (i.e. Vv ═ Vw).
The minimum water requirement method comprises the following steps:
adopting a paste mixer, firstly pouring water into a mixing pot (for example, mixing a water reducing agent, and mixing the water reducing agent and the water), and then mixing a certain mass mB(500g) Is poured into the mixing kettle. Slowly stirring for 1min, then stirring at high speed for 1min, and pausing for 90s, and scraping the slurry at the blade, the edge and the bottom of the pot. Stirring was then continued at high speed for 5min, with continued attempts until the amount of water added was just enough to change the mix from a wet solid (spherical) to a flat homogeneous slurry. The mixing water quantity added at the moment is the minimum water consumption mWI.e. a slight reduction in this water amount only gives a moist agglomerated solid.
The minimum water demand (m) required for forming flat and uniform slurry from certain powder is obtained based on the minimum water demand method testW) And calculating the actual stacking compactness of the powder.For a single powder, the actual packing density of the particles
Figure BDA0003354694780000071
Is the solid volume divided by the total volume, i.e.:
Figure BDA0003354694780000072
in the formula, VBVolume (cm) of solid particles in the powder3)；
VWVolume of the bulk voids in the powder (cm)3)；
mB-mass (g) of powder used in the minimum water requirement method;
mW-minimum water usage (g) of the powder;
rho-density of powder (g/cm)3)。
In the following equation, the assumption that the volume of the minimum water demand is equal to the volume of the voids between the particles is followed. For the superfine cement clinker particle-limestone powder binary mixed system, the actual stacking compactness is as follows:
Figure BDA0003354694780000073
in the formula, ρCDensity (g/cm) of ultrafine cement clinker particles in a binary system3)；
ρLSDensity (g/cm) of limestone powder in binary system3)；
mC-mass (g) of ultrafine cement clinker particles;
mLS-mass (g) of limestone flour;
mW-minimum water requirement (g) required for binary systems.
Substituting the actual stacking compactness of the single powder into a calculation formula of the compressible stacking model to obtain a variation curve of the stacking compactness of the binary system along with different mixing amounts of the powders.
The actual bulk density in the ternary system is calculated by referring to the same logic as the above method, and is not described herein.
S3, determining the mixing ratio:
when only limestone powder particles with large particle size exist in a binary system, a large number of stacking gaps to be filled exist in the system. Along with the increase of the mixing amount of the superfine cement clinker particles, the superfine cement clinker particles with small particle sizes continuously fill the stacking gaps of the limestone powder, and the stacking compactness of a binary reverse filling system is increased.
S4, test piece forming and performance testing:
the superfine cement clinker particles selected in the embodiment of the invention are superfine cement (the strength grade is 42.5, and the specific surface area is 2.62 m) produced by Nippon grass Korea building materials Co2(g), the limestone powder is 200 mesh limestone powder (specific surface area is 0.59 m) produced by Hubei Jingmen Shunshan calcium industry Co Ltd2(g)), the silica fume is micro silica fume produced by Gansu Sanyuan silicon materials Co., Ltd (D50 is: 0.15 μm; the specific surface area is 29.2m2/g)。
Example 1
This example is a method for preparing composite cement and cement prefabricated member.
The raw materials for producing the composite cement of this example included 15g of the ultrafine cement clinker particles and 85g of the limestone powder.
The preparation method of the cement prefabricated member of the embodiment comprises the following steps:
mixing cement and limestone powder at low speed, adding water, and stirring at high speed to obtain uniform and dense slurry (water-gel ratio of 0.127); and then covering and sealing the test piece by using a preservative film, and curing the test piece in water at 20 ℃ after the test piece is hardened (about 24 hours).
Example 2
This example is a method for preparing composite cement and cement prefabricated member.
The raw materials for producing the composite cement of this example included 25g of the ultrafine cement clinker particles and 75g of the limestone powder.
The preparation method of the cement prefabricated member of the embodiment comprises the following steps:
mixing cement and limestone powder at low speed, adding water, and stirring at high speed to obtain uniform and dense slurry (water-gel ratio of 0.120); and then covering and sealing the test piece by using a preservative film, and curing the test piece in water at 20 ℃ after the test piece is hardened (about 24 hours).
Example 3
This example is a method for preparing composite cement and cement prefabricated member.
The raw materials for producing the composite cement of this example included 30g of the ultrafine cement clinker particles and 70g of the limestone powder.
The preparation method of the cement prefabricated member of the embodiment comprises the following steps:
mixing cement and limestone powder at low speed, adding water, and stirring at high speed to obtain uniform and dense slurry (water-gel ratio of 0.120); and then covering and sealing the test piece by using a preservative film, and curing the test piece in water at 20 ℃ after the test piece is hardened (about 24 hours).
Example 4
This example is a method for preparing composite cement and cement prefabricated member.
The raw materials for producing the composite cement of this example included 35g of the ultrafine cement clinker particles and 65g of the limestone powder.
The preparation method of the cement prefabricated member of the embodiment comprises the following steps:
uniformly mixing cement and limestone powder at a low speed, adding water, and continuously stirring and wetting the powder at a high speed to convert the powder into uniform and dense slurry (the water-cement ratio is 0.123); and then covering and sealing the test piece by using a preservative film, and curing the test piece in water at 20 ℃ after the test piece is hardened (about 24 hours).
Example 5
This example is a method for preparing composite cement and cement prefabricated member.
The raw materials for producing the composite cement of this example included 40g of the ultrafine cement clinker particles and 60g of the limestone powder.
The preparation method of the cement prefabricated member of the embodiment comprises the following steps:
mixing cement and limestone powder at low speed, adding water, and stirring at high speed to obtain uniform and dense slurry (water-gel ratio of 0.124); and then covering and sealing the test piece by using a preservative film, and curing the test piece in water at 20 ℃ after the test piece is hardened (about 24 hours).
Example 6
This example is a method for preparing composite cement and cement prefabricated member.
The raw materials for producing the composite cement of this example included 50g of the ultrafine cement clinker particles and 50g of the limestone powder.
The preparation method of the cement prefabricated member of the embodiment comprises the following steps:
mixing cement and limestone powder at low speed, adding water, and stirring at high speed to obtain uniform and dense slurry (water-gel ratio of 0.129); and then covering and sealing the test piece by using a preservative film, and curing the test piece in water at 20 ℃ after the test piece is hardened (about 24 hours).
Example 7
This example is a method for preparing composite cement and cement prefabricated member.
The raw material for producing the composite cement of this example included 100g of ultrafine cement clinker particles.
The preparation method of the cement prefabricated member of the embodiment comprises the following steps:
uniformly mixing cement and limestone powder at a low speed, adding water, and continuously stirring and wetting the powder at a high speed to convert the powder into uniform and dense slurry (the water-cement ratio is 0.177); and then covering and sealing the test piece by using a preservative film, and curing the test piece in water at 20 ℃ after the test piece is hardened (about 24 hours).
Example 8
This example is a method for preparing composite cement and cement prefabricated member.
The raw materials for producing the composite cement of this example included 25g of ultrafine cement clinker particles, 3g of silica fume particles and 72g of limestone powder.
The preparation method of the cement prefabricated member of the embodiment comprises the following steps:
mixing cement and limestone powder at low speed, adding water, and stirring at high speed to obtain uniform and dense slurry (water-gel ratio of 0.120); and then covering and sealing the test piece by using a preservative film, and curing the test piece in water at 20 ℃ after the test piece is hardened (about 24 hours).
Example 9
This example is a method for preparing composite cement and cement prefabricated member.
The raw materials for producing the composite cement of this example included 30g of ultrafine cement clinker particles, 3g of silica fume particles and 67g of limestone powder.
The preparation method of the cement prefabricated member of the embodiment comprises the following steps:
mixing cement and limestone powder at low speed, adding water, and stirring at high speed to obtain uniform and dense slurry (water-gel ratio of 0.120); and then covering and sealing the test piece by using a preservative film, and curing the test piece in water at 20 ℃ after the test piece is hardened (about 24 hours).
When the mixing amount of the superfine cement clinker particles is about 25 percent, the stacking compactness of the binary system reaches the maximum value, and the stacking gaps among the limestone powder are fully filled by the superfine cement clinker particles. When the mixing amount of the superfine cement clinker particles is further increased, the integral stacking compactness is reduced due to the fact that the excessive small particles generate a loosening effect.
The mixing proportion of the composite cement prepared in the embodiments 1-7 of the invention is shown in Table 1.
TABLE 1 compounding ratio of composite cement prepared in inventive examples 1 to 7
Figure BDA0003354694780000101
Figure BDA0003354694780000111
And (3) testing the water consumption for slurry forming according to the minimum water demand method, and obtaining the corresponding actual stacking compactness when different superfine cement clinker particles are mixed according to the actually measured minimum water consumption through inverse calculation, wherein the specific test data are shown in table 1. When the content of the superfine cement clinker particles in the system is 25%, the water-solid ratio is only 0.12, and the actual water-cement ratio is 0.48. When the mixing amount of the superfine cement clinker particles is increased to 30 percent, the actual water cement ratio is only 0.4.
The test results of the compressive strength and the flexural strength of the composite cement prepared in the embodiments 1 to 7 of the invention are shown in fig. 1 and fig. 2. From fig. 1 and 2 it can be seen that: when the mixing amount of the superfine cement clinker particles is less than 30%, the strength of the binary reverse filling system is greatly improved along with the increase of the mixing amount of the cement, and the strength tends to increase linearly. As the cement content continues to increase, the strength increases to a lesser extent. The compression strength and the flexural strength of the hardened slurry mixed with 50 percent of the superfine portland cement and 100 percent of the superfine portland cement are basically the same. At 90 days of age, the compressive strengths of the hardened slurries with 50% (example 6) and 100% (example 7) of cement loading reached 118MPa and 120MPa, respectively. The hardened slurries containing 25% (example 2) and 30% (example 3) of the ultra-fine portland cement had almost the same molding water-to-solid ratio (0.12), and thus the actual water-cement ratio became the determining factor for the development of strength. The actual forming water cement ratio of example 2 was 0.48, and the compressive strengths of the hardened slurry at 3 days and 90 days were 40.1MPa and 74.2MPa, respectively. While example 3 reduces the water to cement ratio to 0.4, the compressive strength of the hardened slurry increased to 47.8MPa and 94.2MPa at 3 days and 90 days, respectively. Examples 2 and 3 demonstrate that reverse gelling filler systems can achieve higher strength with a small amount of cement. When the cement dosage is further reduced to 15%, the strength of the concrete in the 90-day age of the example 1 is only 38.6MPa, and the development of the strength cannot be guaranteed due to the excessively low cement dosage. The ultrafine cement clinker particles used in the reverse-filled cementitious system have a large specific surface area and an increased rate of hydration, so that a reduction in the particle size of the cement particles allows them to hydrate more quickly and to reach a higher degree of hydration in a shorter time. Since the fineness of the cement used was very high, with an average particle size (D50) of about 4 μm, no significant increase in strength was observed after 42 days for all slurries, indicating that a stable structure had been formed.
The compressive strength of the composite cement hardened paste obtained in examples 8 and 9 is shown in FIGS. 3 and 4. Examples 8 and 9, which replace the limestone flour of examples 2 and 3, respectively, by 3% silica fume, are known from fig. 3 and 4: when the silica fume is used for replacing limestone powder with equal mass, the compressive strength of the slurry is improved. The hydration product generated by the reaction of the finer silica fume particles fills the pores of the hardened slurry, further improving the compactness of the structure. At 90 days of age, the compressive strength of the hardened paste of the 25% cement plus 3% silica fume group (example 8) increased from 74.2MPa to 84.7MPa compared to the hardened paste of 25% cement (example 2), and the compressive strength of the 30% cement plus 3% silica fume group (example 9) increased from 94.2MPa to 102.6MPa compared to the 30% cement (example 3). Experimental results show that the limestone powder is replaced by a small amount of silica fume, so that the development of the strength of the limestone powder-superfine cement clinker particle reverse stacking cementing material is facilitated.
The porosity of the material in the embodiment 8 of the invention is 15.3%, and the most probable particle size reaches 13 nm-14 nm, and the material is micro bubbles; the porosity of the porous material in the embodiment 9 of the invention is 12.8%, and the most probable pore diameter reaches 13 nm-14 nm, and the porous material is micro bubbles.
Fig. 5 and 6 are backscattering images of the hardened slurry of example 2 (25% loading of ultra fine cement clinker particles) in the initial state and after 90 days of hydration. In order to observe the initial stacking state of limestone powder-superfine cement clinker particles, the fresh slurry is taken to be soaked and polished in a container after hydration is stopped, and a back scattering test piece is prepared to be observed under an electron microscope. Example 2 had the highest bulk density in the initial state. As shown in fig. 3, a small portion of ultra-fine portland cement particles (UPC, brightest particles) are uniformly distributed among large limestone powder particles (LS, gray particles), and gaps between the particles are filled. In addition, a part of the space (darkest part) is filled with the mixing water in the initial state. As hydration proceeds, cement clinker contacts water to form external hydration products, which gradually occupy the water space. After a 90 day age of continuous hydration, the packed voids of the particles were almost filled with the hydration product, leaving only a small number of Capillary Pores (CP), as shown in fig. 4). In the reverse filling cementitious material, cement particles are uniformly filled in gaps of limestone powder particles in an initial state, and hydration products are generated by continuous hydration to fill the gaps and bond the cement particles and the lime powder particles together, so that a compact microstructure is formed.
The raw material of the composite cement of the present invention selects powder (such as limestone powder and/or silica fume) with fineness equivalent to that of ordinary cement as a skeleton, selects ultrafine cement clinker particles with finer particles as a filler, and fills the stacking gaps of the limestone powder particles with large particle size with cement particles with small particle size. The median particle diameters D50 of the limestone powder and the superfine cement clinker particles are 14.4 μm and 3.9 μm respectively. The limestone powder particles are bonded together by the hydration products produced by the hydration of the ultrafine cement clinker particles, so that a dense structure is obtained.
In the embodiment of the invention, the particle size of the mixed powder is optimized in order to obtain a more compact stacking structure. And (4) as for the stacking compactness of the mixed powder, the stacking compactness is used for characterization. The stacking compactness of the mixed particles with different particle diameters is calculated by a compressible stacking model (CPM), and the optimum proportion of different powders in the most compact stacking state is obtained.
According to the embodiment of the invention, the water-to-glue ratio of the test piece during molding is obtained according to the relationship between the stacking compactness and the water consumption. The volume of the water consumption obtained by calculation is the same as the volume of the gaps among the densely piled powder bodies, and the mixing water is just filled in the gaps among the powder bodies. The hydration products subsequently formed during the hydration reaction occupy the water space, reducing porosity and increasing durability.
In conclusion, the composite cement reduces the emission of carbon dioxide in production by reducing the dosage of cement clinker; the particle accumulation of the system is optimized by changing the proportion of the coarse particles and the fine particles, so that the accumulation compactness of the system is improved, and the initial particle spacing of the system is reduced; the inert powder material is utilized to form the main body part of the stacking system on the cement plastic particles, and the ultrafine particles fill the gaps among the cement particles, so that the stacking compactness of the system is improved.
The price of limestone powder is 180 yuan/ton, the price of cement is 600 yuan/ton, and the price of silica fume is 850 yuan/ton. The dosage of the cementing material in the unilateral concrete is about 400 kg, when 50 percent of limestone powder is used for replacing cement with equal mass, the cost can be reduced by 168 yuan, and the cost reduction ratio of the cementing material is 35 percent.
While the embodiments of the present invention have been described in detail with reference to the specific embodiments, the present invention is not limited to the embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art. Furthermore, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.

Claims (10)

1. The composite cement is characterized in that: the preparation raw materials of the composite cement are inert powder particles and cement clinker particles;
wherein the particle size of the inert powder particles is larger than that of the cement clinker particles, and the mass fraction of the inert powder particles in the composite cement is 35-75%;
the inert powder particles comprise at least one of limestone powder and quartz powder.
2. The composite cement of claim 1, wherein: d50 of the inert powder is 10-20 mu m; preferably, the D50 of the cement clinker particles is between 3 and 5 μm.
3. The composite cement of claim 1, wherein: the water-cement ratio of the composite cement is less than 0.4; preferably, the water-cement ratio of the cement clinker particles is 0.2-0.35.
4. The composite cement of claim 1, wherein: the inert powder particles further comprise silica fume particles; preferably, the mass fraction of the silica fume particles in the composite cement is 2-4%.
5. The composite cement of claim 1, wherein: the cement clinker particles are silicate cement clinker particles.
6. The composite cement of claim 1, wherein: the specific surface area of the cement clinker particles is 2.5m2More than g.
7. Use of a composite cement according to any one of claims 1 to 6 for the preparation of concrete materials and/or cement pre-forms.
8. A cement preform characterized by: the preparation raw materials comprise the composite cement.
9. The cement preform of claim 8, wherein: the compressive strength of the cement prefabricated member is above 80 MPa.
10. A method of making a cement preform according to claim 9, characterized by: the method comprises the following steps:
and mixing the inert powder particles and the cement plastic particles to prepare slurry, and hardening to obtain the cement plastic composite material.
CN202111348012.XA 2021-11-15 2021-11-15 Composite cement, cement prefabricated member, preparation method and application thereof Pending CN114044635A (en)

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB580291A (en) * 1944-06-26 1946-09-03 Steven Gottlieb Improvements in or relating to cement
US5478391A (en) * 1993-03-26 1995-12-26 Cement Technology Corporation Cementitious materials and method of making the same
JPH08239249A (en) * 1995-03-02 1996-09-17 Mitsubishi Materials Corp Cement composition
JPH11147750A (en) * 1997-11-11 1999-06-02 Mitsubishi Materials Corp Cement composition
CN101948255A (en) * 2010-08-27 2011-01-19 华南理工大学 Preparation method of composite cement with low clinker dosage and high flexural compression ratio
JP5623679B2 (en) * 2012-08-21 2014-11-12 大成建設株式会社 Cementitious matrix and fiber-reinforced cementitious mixture
CN109020270A (en) * 2018-08-17 2018-12-18 华南理工大学 A kind of high resistance to corrosion composite Portland cement and preparation method thereof
CN110204274A (en) * 2019-05-29 2019-09-06 华南理工大学 A kind of preparation method of the highly resistance sea water intrusion complex cement based on cementitious material

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB580291A (en) * 1944-06-26 1946-09-03 Steven Gottlieb Improvements in or relating to cement
US5478391A (en) * 1993-03-26 1995-12-26 Cement Technology Corporation Cementitious materials and method of making the same
JPH08239249A (en) * 1995-03-02 1996-09-17 Mitsubishi Materials Corp Cement composition
JPH11147750A (en) * 1997-11-11 1999-06-02 Mitsubishi Materials Corp Cement composition
CN101948255A (en) * 2010-08-27 2011-01-19 华南理工大学 Preparation method of composite cement with low clinker dosage and high flexural compression ratio
JP5623679B2 (en) * 2012-08-21 2014-11-12 大成建設株式会社 Cementitious matrix and fiber-reinforced cementitious mixture
CN109020270A (en) * 2018-08-17 2018-12-18 华南理工大学 A kind of high resistance to corrosion composite Portland cement and preparation method thereof
CN110204274A (en) * 2019-05-29 2019-09-06 华南理工大学 A kind of preparation method of the highly resistance sea water intrusion complex cement based on cementitious material

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