CN115304296B - Recyclable cement and preparation method thereof - Google Patents

Recyclable cement and preparation method thereof Download PDF

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CN115304296B
CN115304296B CN202211036237.6A CN202211036237A CN115304296B CN 115304296 B CN115304296 B CN 115304296B CN 202211036237 A CN202211036237 A CN 202211036237A CN 115304296 B CN115304296 B CN 115304296B
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clinker
cement
recyclable
adjusting materials
waste concrete
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CN115304296A (en
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唐佩
黄杰
李博
陈伟
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Wuhan University of Technology WUT
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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
    • C04B7/24—Cements from oil shales, residues or waste other than slag
    • C04B7/246—Cements from oil shales, residues or waste other than slag from waste building materials, e.g. waste asbestos-cement products, demolition waste
    • 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

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Processing Of Solid Wastes (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)

Abstract

The invention relates to recyclable cement and a preparation method thereof. The recyclable cement comprises waste concrete micro powder and quality adjusting materials, wherein the quality adjusting materials are siliceous quality adjusting materials or calcareous quality adjusting materials, and the quality adjusting materials are not higher than 10% in mass percentage relative to the waste concrete micro powder.The strength of the full-component recyclable cement provided by the invention is kept almost unchanged after repeated recycling, natural resources are saved, and CO is greatly reduced 2 The emission has obvious economic benefit and social value.

Description

Recyclable cement and preparation method thereof
Technical Field
The invention relates to the field of building materials, in particular to recyclable cement and a preparation method thereof.
Background
Cement concrete is the most widely used civil engineering material at present, and since the invention of silicate cement, about 800 million tons of cement is produced by human beings, about 900 million tons of limestone is consumed, and about 400 million tons of CO is discharged 2 . Over 370 million tons of cement have been produced in China for nearly 20 years. Waste concrete is the largest low carbon attribute calcium reserve in nature and human society, where calcium exists primarily in the form of unhydrated cement, hydrated calcium silicate, and aggregate in the concrete. And with the acceleration of urban process in China, the urban transformation process generates more than 6.4 hundred million tons of waste cement concrete each year.
For a long time, due to the lack of an effective full-recycling technology of waste concrete, construction wastes such as waste concrete and the like are piled up or simply buried, resource waste and ecological environment hazard are caused. If the full-cycle cement can be developed, not only can large amount of solid waste be consumed, but also the urgent requirement of sustainable development of building material industry can be met, and the full-cycle cement has great significance on national strategies such as ecological civilization construction, resource safety supply, building material carbon neutralization and the like.
The chemical composition of the waste concrete is similar to that of silicate cement, and the waste concrete can be theoretically used as a raw material for full-component circulation. However, this full component cyclic process faces two challenges:
(1) The waste concrete contains fine aggregate components such as quartz, and silicon oxides such as quartz have lower reactivity than clay silicate minerals after high-temperature firing. When the waste concrete is recycled, quartz is difficult to react with calcareous components to generate clinker phases such as dicalcium silicate, tricalcium silicate and the like, and free calcium oxide and quartz are generated.
(2) The waste concrete contains coarse aggregate components such as calcite and dolomite, while the dolomite chemical composition has a high MgO content (CaMg (CO) 3 ) 2 ). When the waste concrete circulates in full components, the MgO content is extremely easy to exceed 6% specified by national standard, free periclase is produced, and the clinker stability is unqualified.
Therefore, there is a strong need to develop a clinker prepared by using the full components of waste concrete as raw materials, and to perform full component recycling again after the completion of the service. The method provides technical innovation for complete closed circuit of cement concrete material circulation, promotes green sustainable development of building materials, and has great application value.
Disclosure of Invention
The invention provides recyclable cement and a preparation method thereof for solving the technical problems. The invention innovatively provides a carbon-negative clinker system, and the waste concrete micro powder is completely used as a raw material, so that the waste concrete full cycle is realized in the preparation process. Essentially only CO released by combustion of fuel during a full cycle 2 Avoiding CO generated by limestone decomposition 2 The method comprises the steps of carrying out a first treatment on the surface of the At the same time, CO can be absorbed in the stage of carbonization maintenance to form strength 2 Further reducing the CO of the clinker system 2 And (5) discharging. The scheme of the invention realizes the waste building micro powder and CO at the same time 2 The emission is significantly reduced.
The recyclable cement comprises waste concrete micro powder and a conditioning material, wherein the conditioning material is siliceous conditioning material or calcareous conditioning material, and the mass percentage of the conditioning material is not higher than 10%.
Preferably, the siliceous conditioning material is clay and the calcareous conditioning material is limestone.
Preferably, the clinker of the recyclable cement comprises the following components in percentage by mass: caO:40-55%, siO 2 ：25-35％；Al 2 O 3 ：7-12％；MgO：1-10％；Fe 2 O 3 :1-7%, wherein (CaO+MgO)/SiO 2 The molar ratio takes the value of 1.8-2.0.
Preferably, the clinker of the recyclable cement has a phase composition comprising, in mass percent: dicalcium silicate: 50-75% of dicalcium aluminosilicate: 5-15%; magnesium silicate: 0-10%; tricalcium disilicate: 3-10%, 5% -20% of glass phase, and the sum of free calcium oxide, quartz and magnesium oxide content is less than 3%.
Preferably, the preparation method comprises the steps of crushing and grinding waste concrete, adding a mass-regulating material, and performing clinker firing, pressure forming, carbonization and maintenance to obtain the recyclable cement.
Preferably, the carbonization maintenance is carried out at a concentration of CO of 15-99% by volume 2 Curing with relative humidity of 40-60%, and curing time of 1-3 days.
Preferably, the clinker is sintered in a rotary kiln at 1200-1280 deg.c for 0.5-1 hr after premixing.
Preferably, the method further comprises the step of repeatedly carrying out crushing, grinding, clinker firing, pressure forming and carbonization maintenance processes for a plurality of times after the obtained recyclable cement is abandoned in service.
Preferably, after the clinker is sintered, the sintered clinker is crushed and ground to have the grain diameter smaller than 80 microns and the specific surface area larger than 400m 2 /kg。
Preferably, the pressure forming process is to prepare the concrete member by pressure forming the ground clinker at a water cement ratio of 0.1-0.2.
The technical principle and the advantages of the invention are as follows:
(1) The clinker provided by the invention is low-calcium carbon-negative clinker and is characterized in that the molar ratio of Ca to Si is about 1.8-2.0. CaO-C phase diagram of calcium-rich high-temperature area different from ordinary Portland cement firing 2 S-C 12 A 7 The clinker is burned into a corresponding phase diagram C in a high temperature area 2 S-C 3 S 2 -C 2 AS is low calcium and silicon rich. The regional phase diagram is characterized by liquid phase rich silicon at high temperature, liquid phase SiO thereof 2 The content is about 30%; whereas SiO in liquid phase in ordinary silicate cement sintering process 2 The content is about 5%. The liquid phase in the low-calcium negative carbon clinker firing process is easier to melt the quartz phase with lower activity in the waste concrete micro powder, and promotes the quartz phase to participate in the reaction to generate clinker phases such as dicalcium silicate and the like.
(2) The clinker provided by the invention is low-calcium carbon-negative clinker, and MgO component introduced by dolomite aggregate in waste concrete does not form free magnesium oxide, but glass phase or magnesium silicate.
(3) The invention provides (CaO+MgO)/SiO 2 The molar ratio takes the value of 1.8-2.0. The main product of cement hydration in waste concrete is hydrated calcium silicate gel (Ca/Si molar ratio about 2.0). When firing at high temperatureDecomposing at 600-900 deg.C to form dicalcium silicate, which is difficult to be combined with SiO 2 The reaction forms low-calcium monocalcium silicate or tricalcium silicate. The strength of the full-component recyclable cement provided by the invention is kept almost unchanged after repeated recycling, natural resources are saved, and CO is greatly reduced 2 The emission has obvious economic benefit and social value.
Drawings
Figure 1 is an XRD pattern of the full component recycled cement clinker of example 1.
FIG. 2 is a graph showing the compressive strength of the full component recycled cement clinker of example 1.
FIG. 3 is a graph showing the compressive strength of the full component recycled cement clinker of example 2
Fig. 4 is an XRD pattern of the full component recycled cement clinker of comparative example 1.
Figure 5 is an XRD pattern of the full component recycled cement clinker of comparative example 2.
Detailed Description
In order to further illustrate the present invention, the full-component recyclable cement and the method of making the same, provided herein, are described in detail below in conjunction with the examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Waste C40 concrete is used as a main raw material, and calcium carbonate is used as a quality adjusting material. Drying, crushing and grinding the waste concrete to obtain micro powder with granularity smaller than 100 microns. After premixing the waste concrete micro powder and the calcium carbonate, feeding the mixture into a rotary kiln to calcine at 1260 ℃ for 60min, and then rapidly cooling to obtain the recyclable cement with high carbonization activity. After the first cycle, no conditioning material is added for each full component cycle of the waste concrete. The chemical compositions of the waste concrete micro powder and the multi-time full-component circulating clinker are shown in table 1. The ingredients for the full component cycle are shown in table 2.
TABLE 1 composition of the raw materials in example 1 Main chemical composition (wt%)
Figure BDA0003819178720000031
Figure BDA0003819178720000041
Table 2 shows the proportions (unit: g) of the recyclable cement prepared in example 1
Example 1 RCF CaCO 3
First cycle clinker 1000 100
Second cycle clinker 1000 0
Third circulation clinker 1000 0
Fourth cycle clinker 1000 0
Fifth cycle clinker 1000 0
Mixing clinker in the ratio of 0.12 water to ash and formingThe pressure is 9MPa;99% CO 2 The concentration maintenance is carried out for 1 day, and the performance of the full-component circulating clinker is reflected by the compressive strength. The phase composition of the clinker in example 1 is shown in figure 1 and the properties are shown in figure 2. The results show that the performance of the waste concrete remains unchanged after full-component circulation.
Example 2
Waste C40 concrete is used as a main raw material, and clay is used as a quality adjusting material. Drying, crushing and grinding the waste concrete to obtain micro powder with granularity smaller than 100 microns. After premixing the waste concrete micro powder and clay, feeding the mixture into a rotary kiln, calcining the mixture at 1260 ℃ for 60 minutes, and rapidly cooling the mixture to obtain the recyclable cement with high carbonization activity. After the first cycle, no conditioning material is added for each full component cycle of the waste concrete. The chemical compositions of the waste concrete micro powder and the multi-time full-component circulating clinker are shown in table 3. The ingredients for the full component cycle are shown in table 4.
TABLE 3 composition of the raw materials in example 2 Main chemical composition (wt%)
Figure BDA0003819178720000042
Figure BDA0003819178720000051
Table 4 shows the proportions (unit: g) of the recyclable cement prepared in example 2
Example 1 RCF Clay
First cycle clinker 1000 40
Second cycle clinker 1000 0
Third circulation clinker 1000 0
Fourth cycle clinker 1000 0
Fifth cycle clinker 1000 0
Comparative examples 1 and 2 were respectively the construction micro powder burned Portland cement (CaO/SiO) of example 1 for the construction micro powder as a whole-component circulation object 2 Molar ratio greater than 2) and low-calcium carbon-negative clinker (CaO/SiO) 2 Molar ratio 1.0-1.5). The proportions of the recyclable cements in table 5. Fig. 4 and 5 are XRD patterns of the clinker of comparative examples 1 and 2, respectively. The presence of free calcium oxide, magnesium oxide and quartz phases in comparative examples 1 and 2, respectively, indicates that the clinker firing quality is poor and full component recycling is not possible.
Table 5 shows the proportions (unit: g) of the recyclable cement in the comparative examples
RCF CaCO 3 SiO 2 (CaO+MgO)/SiO 2 Molar ratio of
Comparative example 1 1000 300 0 2.25
Comparative example 2 1000 0 100 1.30
The above examples are presented for clarity of illustration only and are not limiting of the embodiments. Other variations and modifications of the above description will be apparent to those of ordinary skill in the art, and it is not necessary or exhaustive of all embodiments, and thus all obvious variations and modifications that come within the scope of the invention are desired to be protected.

Claims (7)

1. The preparation method of the recyclable cement comprises waste concrete micro powder and mass adjusting materials, wherein the mass adjusting materials are siliceous mass adjusting materials or calcareous mass adjusting materials, the mass percentage of the mass adjusting materials relative to the waste concrete micro powder is not higher than 10%, and clinker of the recyclable cement comprises the following components in percentage by mass: caO:40-55%, siO 2 ：25-35%；Al 2 O 3 ：7-12%；MgO：1-10%；Fe 2 O 3 :1-7%, wherein (CaO+MgO)/SiO 2 The molar ratio is 1.8-2.0; the preparation method is characterized in that waste concrete is crushed and ground, then a quality-regulating material is added, clinker firing, pressure forming and carbonization maintenance are carried out, so that first-time recyclable cement is obtained, the crushing, grinding, clinker firing, pressure forming and carbonization maintenance processes are repeated for N times after the obtained first-time recyclable cement is abandoned in service, and the (n+1) -th recyclable cement is obtained, wherein N is a positive integer, and the quality-regulating material is not added after the first circulation.
2. The process according to claim 1, wherein the carbonization treatment is carried out with a CO concentration of 15% to 99% by volume 2 Curing the mixture at the relative humidity of 40-60%, wherein the curing time is 1-3 days.
3. The method for preparing the green brick according to claim 1, wherein the clinker is sintered for 0.5-1 h at 1200-1280 ℃ after premixing the raw materials.
4. The process according to claim 1, wherein the clinker after the completion of the clinker firing is crushed and ground to a particle size of less than 80 μm and a specific surface area of more than 400m 2 /kg。
5. The method of claim 1, wherein the press molding process is a process of preparing the concrete member by press molding the ground clinker at a water cement ratio of 0.1 to 0.2.
6. The method of claim 1, wherein the siliceous conditioning material is clay and the calcareous conditioning material is limestone.
7. The method of claim 1, wherein the clinker phase composition of the recyclable cement comprises, in mass percent: dicalcium silicate: 50-75% of dicalcium aluminosilicate: 5-15%; magnesium silicate: 0-10%; tricalcium disilicate: 3-10%, 5% -20% of glass phase, and the sum of free calcium oxide, quartz and magnesium oxide content is less than 3%.
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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0812404A (en) * 1994-07-05 1996-01-16 Fuminori Tomosawa Recyclable concrete, mortar and recycling thereof

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JP7299120B2 (en) * 2019-03-13 2023-06-27 太平洋セメント株式会社 Method for producing cement powder composition
CN111362600B (en) * 2020-04-09 2022-03-08 长江大学 Preparation method of regenerated set cement
CN112079583A (en) * 2020-08-26 2020-12-15 武汉理工大学 Building material product based on rapid carbonization of regenerated cementing material and preparation method thereof
CN114195414A (en) * 2022-01-05 2022-03-18 西南科技大学 Carbon emission reduction method for production of cementing material
CN114560639A (en) * 2022-03-10 2022-05-31 湖南大学 Solid waste base high-activity carbon-fixing low-calcium gelling material and preparation method thereof
CN114772956B (en) * 2022-03-14 2022-10-21 华南理工大学 High-carbon-absorption early-strength cementing material based on recycled concrete powder and biochar and application thereof

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0812404A (en) * 1994-07-05 1996-01-16 Fuminori Tomosawa Recyclable concrete, mortar and recycling thereof

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