NL2036279A

NL2036279A - Boron-phosphorus composite modified high belite sulphoaluminate cement clinker and preparation method thereof

Info

Publication number: NL2036279A
Application number: NL2036279A
Authority: NL
Inventors: An Nan; Cui Wenjuan; Cao Lixue; Zhang Wensheng; Ye Jiayuan; Zhang Hongtao; Ren Xuehong
Original assignee: China Nat Building Material Group Co Ltd; China Building Mat Academy Co Ltd
Priority date: 2022-12-13
Filing date: 2023-11-15
Publication date: 2024-06-17
Also published as: CN115710095B; ZA202310505B; CN115710095A

Abstract

The disclosure relates to a boron-phosphorus composite modified high belite sulphoaluminate cement clinker and a preparation method thereof. The boron- 5 phosphorus composite modified high belite sulphoaluminate cement clinker includes the following mass fractions of raw materials: 55% to 70% of limestone, 12% to 20% of sandstone, 0% to 5% of Bayer red mud, 5% to 15% of desulfurized gypsum, 5% to 15% of bauxite, 0.01% to 1% of borax, and 0.01% to 2% of calcium phosphate. The cement clinker includes the following mass fractions of mineral components in mass fractions: 10 15% - 30% OF C4A3$, 55% to 75% of C2$, 5% to 10% of C4AF, and 5% to 20% of C$, with the rest including a plurality of miscellaneous mineral components. The following advantages are associated with the disclosure: Borax and calcium phosphate are used to induce the transformation of dicalcium silicate (C28) in the clinker minerals from the ß-CzS crystalline phase to more reactive d-CzS and d’-C28 crystalline phases. The 15 transformation advances the hydration process of C28, thus enhancing strength during later stages of cement curing.

Description

BORON-PHOSPHORUS COMPOSITE MODIFIED HIGH BELITE

SULPHOALUMINATE CEMENT CLINKER AND PREPARATION METHOD THEREOF

TECHNICAL FIELD

[0001] The disclosure relates to a boron-phosphorus composite modified high belite sulphoaluminate cement clinker and a preparation method thereof.

BACKGROUND

[0002] Sulphoaluminate cement is a new type of low carbon cement, with firing temperature of 100-150°C lower than that of Portland cement, and carbon emission far lower than that of Portland cement. However, the hardening time of sulphoaluminate cement is too short for construction, and the strength of sulphoaluminate cement is difficult to increase in the later period and even shrinks. The main reason is that calcium sulphoaluminate, the main mineral of sulphoaluminate cement, reacts quickly in the early hydration process to generate high sulfur type hydrated calcium sulphoaluminate (Ettringite). The product tends to transform to single sulfur type hydrated calcium sulphoaluminate (AFm) over time, resulting in weak strength growth in the later period, and there is a strength reduction, which cannot meet the requirements for later hydration strength growth. Therefore, how to ensure the stable development of strength of sulphoaluminate cement in the middle and later periods has become an urgent problem.

[0003] High belite sulphoaluminate cement is a new type of cement that can effectively solve the above problems. Its main difference from traditional sulphoaluminate cement is that it has lower a C4A:3$ content and a higher proportion of C2S minerals. The clinker of the cement has a lower aluminum content, so it can use lower grade bauxite as its aluminum raw materials to improve the utilization rate of raw materials and reduce production costs. Compared to Portland cement clinker, its CO2 emissions during the production process of cement clinker are lower. In addition, the high belite sulphoaluminate cement can maintain high early strength of ordinary sulphoaluminate cement while ensure stable late strength growth of high belite cement clinker.

[0004] However, at present, most of the high belite sulphoaluminate cement cannot meet the demand for strength increase in the middle and later period, which is mainly because dicalcium silicate (C2S), hydrating in the later period, is mainly B- C2S. And its hydration time is generally after the age of 28 days, before which the strength hardly increases, so a method is needed to solve the problem of insufficient strength development of high belite sulphoaluminate cement.

SUMMARY

[0005] To solve the aforesaid problems, the disclosure provides a boron-phosphorus composite modified high belite sulphoaluminate cement clinker and a preparation method thereof.

[0006] The cement clinker comprises the following mass fractions of raw materials: 55% to 70% of limestone, 12% to 20% of sandstone, 0% to 5% of Bayer red mud, 5% to 15% of desulfurized gypsum, 5% to 15% of bauxite, 0.01% to 1% of borax, and 0.01% to 2% of calcium phosphate.

[0007] The cement clinker comprises the following mass fractions of mineral components in mass fractions: 15% to 30% of C4A3$, 55% to 75% of C2$, 5% to 10% of ~~ C4AF, and 5% to 20% of CaS04 (C$), with the rest comprising a plurality of miscellaneous mineral components.

[0008] The preparation method of the boron-phosphorus composite modified high belite sulphoaluminate cement clinker comprises:

[0009] (1) Pretreatment of raw materials: drying each raw material separately at 105°C for 24 hours; respectively crushing the dried raw materials in a crush until the sieve residue over a 0.08 mm sieve is less than 8%; and

[0010] (2) Pre-mixing of raw materials: creating a mixture by mixing the following mass fractions of the raw materials in a mixing tank: 55% - 70% of limestone, 12% - 20% of sandstone, 0% - 5% of Bayer red mud, 5% - 15% of desulfurized gypsum, 5% - 15% of bauxite, 0.01% - 1% of borax, and 0.01% - 2% of calcium phosphate, in a mixing tank to form a mixture; and transferring the mixture in a mixer and mixing thoroughly for 9 hours to obtain raw material mixture; and

[0011] (3) Pressing: adding 8% by mass of ultra-pure water to the pre-mixed raw material mixture, pressing the resulting mixture into a mold to shape a specimen, and drying the specimen at 105°C for 12 hours to obtain a dry specimen; and

[0012] (4) Calcination of clinker: placing the dry specimen obtained in (3) into a muffle furnace for calcination; gradually raising the temperature to 900°C at a rate of 5 to 10°C/min; holding the temperature for 0.5 to 1 hour; swiftly transferring the calcinated specimen to an environment of 1250 to 1350°C; holding the temperature for 1 hour; after the calcination, taking out the clinker and rapidly cooling the clinker to obtain a high belite sulfoaluminate cement clinker.

[0013] The following advantages are associated with the disclosure: Borax and calcium phosphate are used to induce the transformation of dicalcium silicate (C2S) in the clinker minerals from the B-C2S crystalline phase to relatively more reactive a-C2S and o’-C28S crystalline phases. The transformation advances the hydration process of C25S, thus enhancing strength during later stages of cement curing.

DETAILED DESCRIPTION

[0014] To further illustrate the disclosure, embodiments detailing a boron-phosphorus composite modified high belite sulphoaluminate cement clinker and a preparation method thereof are described below. It should be noted that the following embodiments are intended to describe and not to limit the disclosure.

[0015] A cement clinker comprises the following mass fractions of raw materials: 55% to 70% of limestone, 12% to 20% of sandstone, 0% to 5% of Bayer red mud, 5% to 15% of desulfurized gypsum, 5% to 15% of bauxite, 0.01% to 1% of borax, and 0.01% to 2% of calcium phosphate.

[0016] The cement clinker belongs to the CaO-Si02-Al203-S03-Fe203 pentasystem, and comprises phosphorus, boron, and other elements present in the minerals.

[0017] Borax and calcium phosphate are used to promote the conversion of B-C2S crystalline phases in the clinker minerals into more reactive a-C2S and a’-C2S crystalline phases. The conversion enhances the strength of the cement during later stages of curing while also maintaining a low drying shrinkage rate, thereby ensuring the stability of the cement.

[0018] The cement clinker comprises the following of mineral components in mass fractions: 15% to 30% of C4A3$, 55% to 75% of C2$, 5% to 10% of C4AF, and 5% to 20% of C$, with the rest comprising a plurality of miscellaneous mineral components.

[0019] A method for preparing the boron-phosphorus composite modified high belite sulphoaluminate cement clinker, and the method comprises:

[0020] (1) pretreatment of raw materials: drying each raw material separately at 105°C for 24 hours; respectively crushing the dried raw materials in a crusher until a sieve residue over a 0.08 mm sieve is less than 8%;

[0021] (2) pre-mixing of raw materials: creating a mixture by mixing the following mass fractions of the raw materials in a mixing tank: 55% - 70% of limestone, 12% - 20% of sandstone, 0% - 5% of Bayer red mud, 5% - 15% of desulfurized gypsum, 5% - 15% of bauxite, 0.01% - 1% of borax, and 0.01% - 2% of calcium phosphate; and transferring the mixture to a mixer and mixing thoroughly for 9 hours to obtain a raw material mixture;

[0022] (3) pressing: adding 8% by mass of ultra-pure water to the pre-mixed raw material mixture, pressing the resulting mixture into a mold to shape a specimen, and drying the specimen at 105°C for 12 hours to obtain a dry specimen; and

[0023] (4) calcination of clinker: placing the dry specimen obtained in (3) into a muffle furnace for calcination; gradually raising the temperature to 900°C at a rate of 5 to 10°C/min; holding the temperature for 0.5 to 1 hour; swiftly transferring the calcinated specimen to an environment of 1250 to 1350°C; holding the temperature for 1 hour; after the calcination, taking out the clinker and rapidly cooling the clinker to obtain a high belite sulfoaluminate cement clinker.

[0024] In specific applications, the high belite sulfoaluminate cement clinker obtained in (4) is finely ground to achieve a Blaine specific surface area of 380 — 420 m?/kg and combined with an equal specific surface area of anhydrite that serves as a hydration promoter and set regulator. The specific proportion are as follows: 95%-97% by mass of the high belite sulfoaluminate cement clinker and 3%-5% by mass of anhydrite are mixed together and ground to achieve a Blaine specific surface area of 380 — 420 m2/kg, resulting in the production of belite sulfoaluminate cement.

[0025] For specific applications, refer to Table 1 for detailed information on the respective raw materials and chemical compositions thereof used in Examples 1 to 3:

Table 1 Chemical composition of raw material ip] ee 0 0) 20 10

Loss | SiOz | Al2O3 { Fe203{ CaO SOs | TiO2 | Total types

I CE Eo) A I I EE

Sew | OSE EE EEE [IE

Desulfurized 16.94| 1.35 | 1.55 | 1.1 13425 2.28 (40.35 / 97.82 osn ll el 7e

Example 1

[0026] The five raw materials listed in Table 1 were individually dried at 105°C for 12 hours, and mixed in the following mass fractions: limestone (65.20%), bauxite (8.93%), sandstone (13.92%), desulfurized gypsum (7.65%), and red mud (3.00%). Additionally, 5 0.3% by weight of borax and 1% by weight of calcium phosphate were added and thoroughly blended with the mixture to form a raw material mixture. 1 kg of the raw material mixture was finely ground in a vibrating mill until only 5% of the raw material mixture remained on a sieve with square-shaped holes that have a size of 0.075mm, resulting in a powdered cement raw material mixture. Next, 8% by mass of water was added to the powdered cement raw material mixture and thoroughly stirred. The resulting mixture was then placed in a compression machine, pressed into discs with a diameter of 235 mm. Subsequently, the discs were dried at 105°C for 12 hours, subjected to calcination in a muffle furnace at 900°C for 30 minutes, transferred to an electric furnace and maintained at a temperature of 1290°C for 1 hour. After the calcination process, the mixture was taken out from the electric furnace and rapidly cooled to room temperature using a fan, resulting in the formation of a cement clinker.

[0027] The cement clinker was crushed and finely ground using a ball mill to achieve a fineness with a specific surface area of 400 + 20 m?/kg. For detailed information regarding the chemical composition of the cement clinker and the quantified mineral composition determined through XRD diffraction analysis, refer to Table 2.

Table 2 Chemical composition of the cement clinker

Exam

[0028] Table 3 presents the test results for various physical properties, including the strength of mortar made from the cement clinker, standard consistency water content, and setting time, and other relevant physical properties, all conducted according to the

Chinese nation standard method.

Table 3 Physical properties of the cement clinker and strength of mortar made from the cement clinker.

Specific; Standard | Setting time Flexural Compressive strength

Physical | surface | consistenc (min) (MPa) strength (MPa) properties! area y water _ (m?/kg) content (%) initial Final 28d 28d setting setting

Example

Example 2

[0029] The five raw materials listed in Table 1 were individually dried at 105°C for 12 hours, and mixed in the following mass fractions: limestone (66.67%), bauxite (8.54%), sandstone (15.52%), desulfurized gypsum (6.60%), and red mud (0.37%). The raw material mixture, weighing 5 kg, was supplemented with 0.3% by weight of borax and 2% by weight of calcium phosphate. Afterward, the resulting mixture was finely ground ina vibrating mill until only 5% of the raw material mixture was retained on a sieve with square-shaped holes that have a size of 0.075mm, resulting in a powdered cement raw material mixture. Then, 8% by mass of water was added to the powdered cement raw material mixture and thoroughly stirred. The resulting mixture was placed in a compression machine, pressed into discs with a diameter of 235 mm, and dried at 105°C for 12 hours. Subsequently, the dried mixture was subjected to calcination in a muffle furnace at 900°C for 30 minutes, transferred to an electric furnace and maintained at a temperature of 1290°C for 1 hour. After the calcination process, the mixture was taken out from the electric furnace and rapidly cooled to room temperature using a fan, resulting in the formation of a cement clinker.

[0030] The cement clinker was crushed and finely ground using a ball mill to achieve a fineness with a specific surface area of 400 + 20 m?/kg. For detailed information regarding the chemical composition of the cement clinker and the quantified mineral composition determined through XRD diffraction analysis, refer to Table 4.

Table 4 Chemical composition of the cement clinker

Desulfur

Limes- Red

Bauxite- Sands-| ized C4A3 B- |C4A tone mud/ a-C2S CS e/% | one/% |gypsum $ C2S/ F 1% % %

Example 29.5 25.8 12.2 66.67 | 8.54 | 15.52 0.37 26.78 5.27 2 6 4 4

[0031] Table 5 presents the test results for various physical properties, including the strength of mortar made from the cement clinker, standard consistency water content, and setting time, and other relevant physical properties, all conducted according to the

Chinese nation standard method.

Table 5 Physical properties of the cement clinker and strength of mortar made from the cement clinker. oo Flexural

Specific{ Standard | Setting time Compressive strength

Physical | surface | consistenc (min) (MPa) strength (MPa) a properties| area y water

Initial | Final (m?/kg) content (%) 3d 28d 3d 28d setting setting

Example 5 412 23.7 0:25 | 0:47 3.848 23.8/33.9

Example 3

[0032] The five raw materials listed in Table 1 were individually dried at 105°C for 12 hours, and mixed in the following mass fractions: limestone (61.18%), bauxite (15.82%), sandstone (10.12%), desulfurized gypsum (8.52%), and red mud (1.76%). The raw material mixture, weighing 5 kg, was supplemented with 0.6% by weight of borax and 2% by weight of calcium phosphate. Afterward, the resulting mixture was finely ground in a vibrating mill until only 5% of the raw material mixture was retained on a sieve with square-shaped holes that have a size of 0.075mm, resulting in a powdered cement raw material mixture. Then, 8% by mass of water was added to the powdered cement raw material mixture and thoroughly stirred. The resulting mixture was placed in a compression machine, pressed into discs with a diameter of 235 mm, and dried at

105°C for 12 hours. Subsequently, the dried mixture was subjected to calcination in a muffle furnace at 900°C for 30 minutes, transferred to an electric furnace and maintained at a temperature of 1290°C for 1 hour. After the calcination process, the mixture was taken out from the electric furnace and rapidly cooled to room temperature using a fan, resulting in the formation of a cement clinker.

[0033] The cement clinker was crushed and finely ground using a ball mill to achieve a fineness with a specific surface area of 400 + 20 m?/kg. For detailed information regarding the chemical composition of the cement clinker and the quantified mineral composition determined through XRD diffraction analysis, refer to Table 6.

Table 6 Chemical composition of the cement clinker

Desulfuri

Lime- Sand- Red

Bauxit zed stone/ stone/ mud/| C4A3$ |a-C2S| B-C2S | C4AF | C$ el% ayps- % % % um/%

[0034] Table 7 presents the test results for various physical properties, including the strength of mortar made from the cement clinker, standard consistency water content, and setting time, and other relevant physical properties, all conducted according to the

Chinese nation standard method.

Table 7 Physical properties of the cement clinker and strength of mortar made from the cement clinker. — Flexural

Specific; Standard | Setting time Compressive strength

Initial | Final (m2/kg) content (%) 3d | 7d 28d} 3d | 7d | 28d setting setting

Example 3 405 23.9 0:26 | 0:48 3.8 47 7.2 | 26.6/34.7 60.5

Example 4

[0035] The five raw materials listed in Table 1 were individually dried at 105°C for 12 hours, and mixed in the following mass fractions: limestone (61.18%), bauxite (15.82%), sandstone (10.12%), desulfurized gypsum (11.07%), and red mud (1.76%). The raw material mixture, weighing 5 kg, was finely ground in a vibrating mill until only 5% of the raw material mixture was retained on a sieve with square-shaped holes that have a size of 0.075mm, resulting in a powdered cement raw material mixture. Then, 8% by mass of water was added to the powdered cement raw material mixture and thoroughly stirred.

The resulting mixture was placed in a compression machine, pressed into discs with a diameter of 235 mm, and dried at 105°C for 12 hours. Subsequently, the dried mixture was subjected to calcination in a muffle furnace at 900°C for 30 minutes, transferred to an electric furnace and maintained at a temperature of 1290°C for 1 hour. After the calcination process, the mixture was taken out from the electric furnace and rapidly cooled to room temperature using a fan, resulting in the formation of a cement clinker.

[0036] The cement clinker was crushed and finely ground using a ball mill to achieve a fineness with a specific surface area of 400 + 20 m?/kg. For detailed information regarding the chemical composition of the cement clinker and the quantified mineral composition determined through XRD diffraction analysis, refer to Table 8.

Table 8 Chemical composition of the cement clinker

Lime- _|Sand- Desulfur Red stone/ Baux stone/ zed mud/| C4A3$ |a-C2S|B-C2S| C4AF | C$ % el% % ayps- % um/%

Exampl

[0037] Table 9 presents the test results for various physical properties, including the strength of mortar made from the cement clinker, standard consistency water content, and setting time, and other relevant physical properties, all conducted according to the

Chinese nation standard method.

Table 9 Physical properties of the cement clinker and strength of mortar made from the cement clinker. — Flexural

Specific; Standard | Setting time Compressive strength

Physical | surface | consistenc (min) (MPa) strength (MPa) a properties| area y water _ :

Initial | Final (m?/kg) content (%) ‚3d 7d {28d} 3d | 7d | 28d setting setting

Example 4 410 25.7 0:22 | 0:48 3.8 47 6.6 25.2/33.8 49.4

[0038] Under comparable specific surface area conditions of the cement clinker, the addition of 0.3% to 0.6% by mass of borax and 1% to 2% by mass of calcium phosphate tothe raw material resulted in a significant improvement in the flexural and compressive strengths of the cement clinker mortar when compared to Example 4, where boron and phosphorus were not added. The results indicated that the inclusion of boron and phosphorus during the sintering process of the cement clinker had a positive impact on the strength of the cement clinker during the middle and later stages.

Claims

ConclusiesConclusions

1. Boor-fosfor composiet gemodificeerd hoog beliet sulfoaluminaatcementklinker, omvattende de volgende massafracties van ruwe materialen: 55% tot en met 70% aan kalksteen, 12% tot en met 20% aan zandsteen, 0% tot en met 5% aan Bayer rood slib, 5% tot en met 15% aan ontzwaveld gips, 5% tot en met 15% aan bauxiet, 0,01% tot en met 1% aan borax, en 0,01% tot en met 2% aan calciumfosfaat.1. Boron-phosphorus composite modified high belite sulfoaluminate cement clinker, comprising the following mass fractions of raw materials: 55% to 70% limestone, 12% to 20% sandstone, 0% to 5% Bayer red sludge , 5% to 15% of desulfurized gypsum, 5% to 15% of bauxite, 0.01% to 1% of borax, and 0.01% to 2% of calcium phosphate.

2. Cementklinker volgens conclusie 1, waarbij de cementklinker de volgende massafracties omvat aan minerale componenten in massafracties: 15% tot en met 30% aan C4A3$, 55% tot en met 75% aan C2$, 5% tot en met 10% aan C4AF, en 5% tot en met 20% aan C$, waarbij de rest een veelheid aan verschillende minerale componenten omvat.2. Cement clinker according to claim 1, wherein the cement clinker comprises the following mass fractions of mineral components in mass fractions: 15% to 30% of C4A3$, 55% to 75% of C2$, 5% to 10% of C4AF, and 5% to 20% of C$, with the remainder comprising a variety of different mineral components.

3. Werkwijze voor het bereiden van een boor-fosfor composiet gemodificeerde hoog beliet sulfoaluminaatcementklinker volgens conclusie 1, waarbij de werkwijze omvat: 1) het voorbehandelen van ruwe materialen: het afzonderlijk drogen van elk materiaal bij 105 °C gedurende 24 uren; respectievelijk het verpletteren van de gedroogde ruwe materialen in een molen tot een zeefresidu over een 0,08 mm zeef overblijft dat kleiner is dan 8%; 2) het voormengen van ruwe materialen: het creëren van een mengsel door de volgende massafracties van de ruwe materialen te mengen in een mengreservoir: 55% tot en met 70% aan kalksteen, 12% tot en met 20% aan zandsteen, 0% tot en met 5% aan Bayer rood slib, 5% tot en met 15% aan ontzwaveld gips, 5% tot en met 15% aan bauxiet, 0,01% tot en met 1% aan borax, en 0,01% tot en met 2% aan calciumfosfaat; en het overbrengen van het mengsel naar een menger, en het grondig mengen gedurende 9 uren, teneinde te komen tot een ruw materiaalmengsel; 3) persen: het toevoegen van 8% op massabasis van ultra-zuiver water aan het voorgemengde ruwe materiaalmengsel, het persen van het resulterende mengsel in een vorm, teneinde een specimen te vormen, en het drogen van het specimen bij 105 °C gedurende 12 uren, teneinde een droog specimen te verkrijgen; enA method for preparing a boron-phosphorus composite modified high belite sulfoaluminate cement clinker according to claim 1, wherein the method comprises: 1) pretreating raw materials: drying each material separately at 105°C for 24 hours; respectively crushing the dried raw materials in a mill until a sieve residue over a 0.08 mm sieve is left that is less than 8%; 2) pre-mixing of raw materials: creating a mixture by mixing the following mass fractions of the raw materials in a mixing tank: 55% to 70% of limestone, 12% to 20% of sandstone, 0% to and with 5% of Bayer red sludge, 5% to 15% of desulfurized gypsum, 5% to 15% of bauxite, 0.01% to 1% of borax, and 0.01% to 2% calcium phosphate; and transferring the mixture to a mixer and mixing thoroughly for 9 hours to obtain a raw material mixture; 3) pressing: adding 8% by mass of ultra-pure water to the pre-mixed raw material mixture, pressing the resulting mixture into a mold to form a specimen, and drying the specimen at 105°C for 12 hours, in order to obtain a dry specimen; and

4) calcineren van klinker: het in (3) verkregen droge specimen in een moffeloven plaatsen met het oog op het uitvoeren van een calcinering; het geleidelijk aan opdrijven van de temperatuur tot 900 °C aan een snelheid van4) calcination of clinker: placing the dry specimen obtained in (3) in a muffle furnace with a view to carrying out a calcination; gradually increasing the temperature to 900 °C at a rate of

5 °C/min tot en met 10 °C/min; het snel overbrengen van het gecalcineerde specimen naar een omgeving met een temperatuur van 1250 °C tot en met5 °C/min to 10 °C/min; the rapid transfer of the calcined specimen to an environment with a temperature of 1250 °C to

1350 °C; het in stand houden van de temperatuur gedurende 1 uur; na het calcineren, het verwijderen van de klinker en het snel afkoelen van de klinker, teneinde een hoog beliet sulfoaluminaatcementklinker te verkrijgen.1350°C; maintaining the temperature for 1 hour; after calcining, removing the clinker and rapidly cooling the clinker, in order to obtain a highly belite sulfoaluminate cement clinker.