High-temperature calcined-activated slag cement base material as well as preparation method and application thereof

Abstract

The invention belongs to the field of building materials, discloses a high-temperature calcined-activated slag cement base material as well as a preparation method and application thereof, and aims to solve the technical problems of poor slag activation effect, high cement carbon emission and insufficient performance in the prior art. The high-temperature calcined-activated slag cement is prepared from the following raw materials in parts by mass: 40 to 80 parts of cement clinker, 15 to 45 parts of high-temperature calcined activated slag and 0 to 5 parts of gypsum, wherein the raw material of the high-temperature calcined activated slag is bauxite desiliconized tailings. According to the slag cement prepared by calcining and activating the slag, the use intensity of the slag cement is guaranteed while the use amount of the cement clinker is reduced. According to the method, resource utilization of the slag is achieved, solid waste stockpiling pollution is reduced, and compared with traditional clinker, the method is low in calcination temperature and energy consumption, simple in preparation process step and easy for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of building materials, in particular to a cement preparation method. BACKGROUND

[0002] After the low-grade bauxite is treated by desilication, a large amount of desilication tailings (which belong to a kind of slag) will be produced. If these tailings are stored for a long time, not only land resources will be occupied, but also environmental problems such as soil pollution and water pollution may be caused, and resources will be wasted seriously.

[0003] At present, some technologies (CN106348697A) attempt to incorporate desilication tailings into cement to realize recycling, but due to the low activity of desilication tailings which have not been effectively activated, the compatibility with the cement matrix is poor, which leads to the difficulty of meeting the engineering requirements in terms of strength, durability and other key performances of composite cement. The existing activation methods mostly use chemical activation (such as adding alkali activator), which can improve the activity of slag to some extent, but has problems such as high cost and easy to cause cement shrinkage and cracking in later stage; and the conventional low-temperature calcination (lower than 500℃) has limited activation effect, which cannot fully destroy the inert mineral structure of slag and release effective active ingredients. Patent CN119241196A uses a hydration accelerator (mass ratio 0.08-0.13:1) composed of cupric hydroxide iodate and aluminum dihydrogen phosphate, adjusts the alkalinity of the system through double-displacement complexation reaction, accelerates the dissolution of silicon-aluminum phases in slag powder, promotes the early generation of AFt (ettringite) and C-S-H gel (calcium silicate hydrate), and fills the pores of hydration products to improve the density, but cupric hydroxide iodate is a small chemical raw material, the market supply is relatively limited, and the price is relatively high, which may face the problems of unstable raw material supply and rising cost in large-scale production; at the same time, cupric hydroxide iodate has strong alkalinity, which may cause local alkalinity to be too high and lead to the risk of cement shrinkage and cracking in later stage if the stirring is not uniform.

[0004] In addition, the traditional cement production process has high carbon emission. Therefore, it is an urgent problem to be solved in the field of building materials to develop a kind of cement which can efficiently activate slag (desilication tailings), reduce carbon emission of cement, and ensure the mechanical properties of cement. SUMMARY

[0005] In view of the technical problems of poor activation effect of slag, high carbon emission of cement and insufficient performance of prepared cement-based products, the present application provides a high-temperature calcination-activated slag cement base material, a preparation method and application thereof. Through high-temperature calcination at a specific temperature, the slag is efficiently activated, and by combining with reasonable component proportion, the industrial solid waste is utilized, and low-carbon and high-strength cement materials are prepared.

[0006] To achieve the above-mentioned purposes, the technical scheme of the present application is as follows: A high-temperature calcined-activated slag cement base material, raw materials of which include cement clinker 40-80 parts, high-temperature calcined-activated slag 15-45 parts and gypsum 0-5 parts in mass fraction; wherein, raw materials of the high-temperature calcined-activated slag are bauxite desilicon tailings.

[0007] The high-temperature calcined-activated slag is obtained by crushing, grinding and constant temperature calcining at 500-800℃ for 1-2.5h of the bauxite desilicon tailings.

[0008] Further, the temperature increasing rate of the constant temperature calcining is 5-10℃ / min.

[0009] The gypsum is dihydrate gypsum, purity of which is ≥90%.

[0010] The preparation method of the high-temperature calcined-activated slag cement base material is as follows: (1) slag pretreatment and high-temperature calcined-activation: the bauxite desilicon tailings are sent into a crusher for crushing, then ground by a vibration mill and sieved by a 200 mesh standard sieve to obtain powder with particle size ≤0.075mm; the ground powder is put into a muffle furnace, the temperature is increased to 500-800℃ at a temperature increasing rate of 5-10℃ / min, constant temperature calcining is carried out for 1-2.5h, and then the calcined slag is naturally cooled to room temperature to obtain the high-temperature calcined-activated slag; (2) raw material mixing: silicate cement clinker, high-temperature calcined-activated slag and gypsum are weighed according to mass fraction, and then put into a mixer to mix for 10-20min at a rotating speed of 150-300r / min to obtain mixed powder, i.e. the high-temperature calcined-activated slag cement base material.

[0011] The specific surface area of the high-temperature calcined-activated slag cement base material is 350-400m 2 / kg (the specific surface area data is obtained by experimental test according to GB / T8074-2008 "Cement Specific Surface Area Determination Method Blaine Method").

[0012] The application of the high-temperature calcined-activated slag cement base material in preparing mortar or concrete. For example, the prepared high-temperature calcined-activated slag cement base material is added with formula amount of water, stirred in a stirrer at a rotating speed of 200-500r / min for 5-10min to form a uniform cement slurry, and then molded and cured to obtain.

[0013] The present application has the following advantages: 1. excellent activation effect: the main inert mineral phases (such as kaolinite and diaspore) in the desilicon tailings are fully converted into high-activity metakaolin and corundum phase by high-temperature calcining at 500-800℃, the particle size of the slag is reduced, the specific surface area is increased, and the pozzolanic activity of the slag is enhanced.

[0014] 2. Low carbon and environmentally friendly: This invention uses industrial solid waste (desiliconized tailings) as the main auxiliary material to replace part of the silicate cement clinker, thereby reducing the amount of clinker used in the cement production process, reducing carbon emissions, and realizing the resource utilization of desiliconized tailings, reducing solid waste stockpiling pollution.

[0015] 3. Improved mechanical properties: Tests have verified that the mortar test blocks prepared from the cement-based material of this invention have a 3-day compressive strength ≥18MPa and a 28-day compressive strength ≥42.5MPa.

[0016] 4. Low cost and simple process: This invention uses high-temperature calcination activation, which does not require the addition of expensive chemical activators. Moreover, the calcination temperature is moderate (lower than the traditional clinker calcination temperature), the energy consumption is low, the preparation process is simple, and it is easy to industrialize. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 SEM images of the high-temperature calcined activated slag prepared in Examples 1-3.

[0019] Figure 2 The FTIR spectra of the high-temperature calcined activated slag prepared in Examples 1-3 are shown.

[0020] Figure 3 The XRD patterns are those of the high-temperature calcined activated slag prepared in Examples 1-3.

[0021] Figure 4 The compressive strength diagrams are for the high-temperature calcined-activated slag cement materials prepared in Examples 1-5 and Comparative Example 1 after curing. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The composition of the silicate cement clinker used in this invention is shown in Table 1.

[0024] Table 1 Chemical composition of silicate cement clinker The components of the bauxite desilication tailings used in the present application are shown in Table 2.

[0025] Table 2 Chemical components of bauxite desilication tailings Example 1 The high-temperature calcined-activated slag cement base material of the present example has the following mass fractions of components: Portland cement clinker 70 parts, high-temperature calcined-activated slag 30 parts, and gypsum 0 parts.

[0026] The preparation method of the high-temperature calcined-activated slag cement base material has the following steps: (1) Slag pretreatment and high-temperature calcination and activation: The bauxite desilication tailings are fed into a crusher for crushing, and then ground by a vibrating mill, and the powder with a particle size of ≤0.075 mm is sieved out by a 200-mesh standard sieve; the ground powder is placed in a muffle furnace, and the temperature is raised to 500°C at a rate of 5°C / min, and the temperature is kept constant for 2 h, and then naturally cooled to room temperature after calcination, to obtain high-temperature calcined-activated slag; (2) Mixing of raw materials: The Portland cement clinker, high-temperature calcined-activated slag, and gypsum are weighed according to the above mass fractions, and the above raw materials are put into a mixer, and mixed at a speed of 180 r / min for 15 min, to obtain a mixed powder, i.e., a high-temperature calcined-activated slag cement base material (with a specific surface area of 373 m 2 / kg).

[0027] Preparation of mortar test blocks: Water is added to the high-temperature calcined-activated slag cement base material (with a water-binder ratio of 0.5), and stirred in a stirrer at a speed of 350 r / min for 10 min to form a uniform cement slurry, and then molded by injection and cured at a temperature of 25°C and a humidity of 65% for 3-28 days to obtain mortar test blocks (40 mm x 40 mm x 160 mm).

[0028] Example 2 The high-temperature calcined-activated slag cement base material of the present example has the following mass fractions of components: Portland cement clinker 75 parts, high-temperature calcined-activated slag 25 parts, and gypsum 0 parts.

[0029] The preparation method of the high-temperature calcined-activated slag cement base material has the following steps: (1) Slag pretreatment and high-temperature calcination and activation: The bauxite desilication tailings are fed into a crusher for crushing, and then ground by a vibrating mill, and the powder with a particle size of ≤0.075 mm is sieved out by a 200-mesh standard sieve; the ground powder is placed in a muffle furnace, and the temperature is raised to 600°C at a rate of 10°C / min, and the temperature is kept constant for 1.5 h, and then naturally cooled to room temperature after calcination, to obtain high-temperature calcined-activated slag; (2) Raw material mixing: the portland cement clinker, high-temperature calcined and activated slag, and gypsum were weighed according to the above mass ratio, and were put into a mixer to mix for 10 min at a rotation speed of 150 r / min, to obtain a mixed powder, i.e., a high-temperature calcined-activated slag cement base material (the specific surface area was 381 m 2 / kg).

[0030] Preparation of mortar test block: water was added to the high-temperature calcined-activated slag cement base material (the water-binder ratio was controlled to be 0.5), and was stirred in a stirrer at a rotation speed of 200 r / min for 10 min to form a uniform cement slurry, and then was injected into a mold and cured for 3-28 days under the condition that the temperature was 25°C and the humidity was 65%, to obtain a mortar test block (40 mm x 40 mm x 160 mm).

[0031] Example 3 The high-temperature calcined-activated slag cement base material of the present example had the following mass ratio of components: portland cement clinker 60 parts, high-temperature calcined and activated slag 38 parts, and gypsum 2 parts.

[0032] The preparation method of the high-temperature calcined-activated slag cement base material had the following steps: (1) Slag pretreatment and high-temperature calcination and activation: the bauxite desilication tailings were sent into a crusher for crushing, and then were ground by a vibration mill and sieved by a standard sieve with a mesh size of 200 to obtain a powder with a particle size of ≤0.075 mm; the ground powder was put into a muffle furnace, and was heated to 700°C at a heating rate of 5°C / min, and was calcined at constant temperature for 1 h, and was naturally cooled to room temperature after calcination, to obtain high-temperature calcined and activated slag; (2) Raw material mixing: the portland cement clinker, high-temperature calcined and activated slag, and gypsum were weighed according to the above mass ratio, and were put into a mixer to mix for 20 min at a rotation speed of 250 r / min, to obtain a mixed powder, i.e., a high-temperature calcined-activated slag cement base material (the specific surface area was 394 m 2 / kg).

[0033] Preparation of mortar test block: water was added to the high-temperature calcined-activated slag cement base material (the water-binder ratio was controlled to be 0.5), and was stirred in a stirrer at a rotation speed of 400 r / min for 8 min to form a uniform cement slurry, and then was injected into a mold and cured for 3-28 days under the condition that the temperature was 25°C and the humidity was 65%, to obtain a mortar test block (40 mm x 40 mm x 160 mm).

[0034] Example 4 The high-temperature calcined-activated slag cement base material of the present example had the following mass ratio of components: portland cement clinker 50 parts, high-temperature calcined and activated slag 47 parts, and gypsum 3 parts.

[0035] The preparation method of the high-temperature calcined-activated slag cement base material is as follows: (1) Slag pretreatment and high-temperature calcination and activation: the bauxite desilication tailings are sent into a crusher for crushing, and then are ground by a vibration mill, and the powder with a particle size of ≤0.075 mm is sieved out by a 200-mesh standard sieve; the ground powder is placed into a muffle furnace, and is raised to 800℃ at a temperature raising rate of 10℃ / min, and is calcined at constant temperature for 1h, and is naturally cooled to room temperature after the calcination is completed, and the high-temperature calcined-activated slag is obtained; (2) Raw material mixing: the portland cement clinker, the high-temperature calcined-activated slag and the gypsum are weighed according to the above mass fractions, and the raw materials are put into a mixer, and are mixed at a rotating speed of 300r / min for 15min, and the mixed powder, i.e. the high-temperature calcined-activated slag cement base material (the specific surface area is 397 m 2 / kg) is obtained.

[0036] Preparation of mortar test block: water is added into the high-temperature calcined-activated slag cement base material (the water-binder ratio is controlled to be 0.5), and is stirred in a stirrer at a rotating speed of 400r / min for 10min, and a uniform cement slurry is formed, and then is injected into a mold, and is cured under the conditions that the temperature is 25℃ and the humidity is 65%, and is cured for 3-28 days, and the mortar test block (40mm×40mm×160mm) is obtained.

[0037] Example 5 The mass fractions of the components of the high-temperature calcined-activated slag cement base material of the present example are as follows: the portland cement clinker is 40 parts, the high-temperature calcined-activated slag is 45 parts, and the gypsum is 5 parts.

[0038] The preparation method of the high-temperature calcined-activated slag cement base material is as follows: (1) Slag pretreatment and high-temperature calcination and activation: the bauxite desilication tailings are sent into a crusher for crushing, and then are ground by a vibration mill, and the powder with a particle size of ≤0.075 mm is sieved out by a 200-mesh standard sieve; the ground powder is placed into a muffle furnace, and is raised to 750℃ at a temperature raising rate of 10℃ / min, and is calcined at constant temperature for 1h, and is naturally cooled to room temperature after the calcination is completed, and the high-temperature calcined-activated slag is obtained; (2) Raw material mixing: the portland cement clinker, the high-temperature calcined-activated slag and the gypsum are weighed according to the above mass fractions, and the raw materials are put into a mixer, and are mixed at a rotating speed of 200r / min for 20min, and the mixed powder, i.e. the high-temperature calcined-activated slag cement base material (the specific surface area is 385 m 2 / kg) is obtained.

[0039] Preparation of mortar test block: water was added to the high-temperature calcined-activated slag cement base material (controlling the water-binder ratio to be 0.5), and stirred in a stirrer at a rotating speed of 400 r / min for 10 min to form a uniform cement slurry, and then the cement slurry was injected into a mold and cured under the conditions of a temperature of 25°C and a humidity of 65% for 3-28 days to obtain a mortar test block (40 mm x 40 mm x 160 mm).

[0040] Example 6 The high-temperature calcined-activated slag cement base material of the present example has the following mass fractions of components: 80 parts of Portland cement clinker, 15 parts of high-temperature calcined-activated slag, and 5 parts of gypsum.

[0041] The preparation method of the high-temperature calcined-activated slag cement base material has the following steps: (1) slag pretreatment and high-temperature calcination and activation: the bauxite desilicon tailings were sent into a crusher for crushing, and then ground by a vibration mill and sieved by a standard sieve of 200 mesh to obtain a powder with a particle size of ≤0.075 mm; the ground powder was placed in a muffle furnace, and the temperature was raised to 500°C at a rate of 8°C / min, and then kept at a constant temperature for 2.5 h, and then naturally cooled to room temperature to obtain high-temperature calcined-activated slag; (2) mixing of raw materials: the Portland cement clinker, the high-temperature calcined-activated slag, and the gypsum were weighed according to the above mass fractions, and then put into a mixer to mix for 20 min under the condition of a rotating speed of 200 r / min to obtain a mixed powder, i.e. the high-temperature calcined-activated slag cement base material (with a specific surface area of 376 m 2 / kg).

[0042] Preparation of mortar test block: water was added to the high-temperature calcined-activated slag cement base material (controlling the water-binder ratio to be 0.5), and stirred in a stirrer at a rotating speed of 400 r / min for 10 min to form a uniform cement slurry, and then the cement slurry was injected into a mold and cured under the conditions of a temperature of 25°C and a humidity of 65% for 3-28 days to obtain a mortar test block (40 mm x 40 mm x 160 mm).

[0043] Comparative Example 1 The cement base material of the present comparative example has the following mass fractions of components: 70 parts of Portland cement clinker and 30 parts of bauxite desilicon tailings (not calcined and activated).

[0044] The preparation method of the cement base material of the present comparative example has the following steps: the Portland cement clinker and the bauxite desilicon tailings (not calcined and activated) were weighed according to the above mass fractions, and then put into a mixer to mix for 15 min under the condition of a rotating speed of 180 r / min to obtain a mixed powder, i.e. the cement base material.

[0045] Preparation of mortar test blocks: Water was added to the cementitious material of this comparative example (the water-cement ratio was controlled to be 0.5), and the mixture was stirred in a mixer at a speed of 350 r / min for 10 min to form a uniform cement paste. After being poured into molds and cured at a temperature of 25℃ and a humidity of 65% for 3-28 days, mortar test blocks (40mm×40mm×160mm) were obtained.

[0046] Implementation Results Example 1. Effect of calcination temperature on the properties of desiliconized tailings (1) Microscopic morphology analysis The microstructure of the desiliconized tailings at different calcination temperatures is shown in Figure 1. It can be seen that the desiliconized tailings at 500℃ still exhibit an irregular morphology with relatively more coarse particles. As the calcination temperature increases, the number of blocky particles decreases significantly, the desiliconized tailings particles are significantly refined, the particle size becomes smaller, and the surface edges gradually disappear.

[0047] (2) Infrared spectroscopy analysis Infrared spectra of desilication tailings at different calcination temperatures, such as Figure 2 As shown, 3695cm -1 and 3621cm -1 It is the hydroxyl stretching vibration peak of kaolinite, 2110 cm⁻¹ -1 and 1990cm -1 It is the hydroxyl stretching vibration peak of diaspore monohydrate, 10¹⁰ cm⁻¹ -1 The chemical vibration peak of the aluminum-oxygen bond in gibbsite is 907 cm⁻¹. -1 The peak of the hydroxyl bending vibration of kaolinite is 758 cm⁻¹. -1 This is the peak of the silicon-oxygen bond bending vibration in kaolinite.

[0048] When the calcination temperature is 500℃, 3695cm -1 and 3621cm -1 The intensities of the two kaolinite hydroxyl stretching vibration peaks decreased significantly, with the peak at 3695 cm⁻¹ decreasing at a calcination temperature of 600℃. -1 and 3621cm -1 The two characteristic peaks almost completely disappeared. This indicates that kaolinite begins to lose a large amount of hydroxyl groups at a calcination temperature of 500℃, and by 600℃, the hydroxyl groups are almost completely removed. At a calcination temperature of 500℃, the peak at 2110 cm⁻¹... -1 and 1990cm -1 The intensities of the two hydroxyl stretching vibration peaks in diaspore began to decrease, and the characteristic peaks of both disappeared almost completely at 700℃. This indicates that diaspore begins to lose hydroxyl groups at a calcination temperature of 500℃, and by 700℃, the hydroxyl groups have been almost completely removed.

[0049] (3) X-ray diffraction analysis The XRD patterns of the desilication tailings at different calcination temperatures are shown in Figure 3 As shown in the figure, after calcination at 500 DEG C, the diffraction peak intensity of kaolinite is greatly reduced, and the diffraction peak intensity of diaspore also begins to decrease, indicating that the kaolinite in the desilication tailings has begun to decompose into metakaolin at 500 DEG C, and the decomposition equation is shown in formula 1, and the diaspore also begins to decompose to generate corundum phase, and the decomposition equation is shown in formula 2. After calcination at 600 DEG C, the diffraction peak of kaolinite disappears completely, and the diffraction peak intensity of diaspore is greatly reduced, and the diffraction peak of diaspore disappears completely at 700 DEG C, indicating that the diaspore has completely dehydrated and converted into corundum phase. Since metakaolin belongs to semi-crystalline or amorphous nature, its obvious diffraction peak cannot be seen in the XRD pattern. Therefore, the XRD analysis results of the desilication tailings are basically consistent with the infrared analysis results.

[0050] 2, Compressive strength The cement mortar test blocks of 40mmx40mmx160mm were prepared by using examples 1-5 and comparative example 1 respectively, and the compressive strength test was carried out according to the standard of GB / T17671-2021 "Cement mortar strength test method (ISO method)", and the 3d and 28d compressive strength was measured. The component distribution ratio of the cement base material and the compressive strength test results are shown in table 3.

[0051] Table 3 Component distribution ratio of cement base material and compressive strength test results From table 3 and Figure 4 It can be seen that the 3d compressive strength of the cement mortar test blocks prepared by examples 1-5 reaches 18.3-20.6MPa, compared with comparative example 1, the increase of the amount of slag will slightly reduce the early strength of cement, which indicates that it has a certain delaying effect on the early hydration of cement. At the same time, the 28d compressive strength of the cement mortar test blocks prepared by examples 1-5 reaches 42.8-46.9MPa, compared with comparative example 1, while reducing the amount of portland cement clinker, it also ensures that the service strength of the cement test block is improved by 15-30%.

[0052] The above only describes the preferred embodiments of the present application and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A high temperature calcined-activated slag cement binder, characterized in that, The raw materials include cement clinker 40-80 parts by mass, high-temperature calcined and activated slag 15-45 parts by mass, and gypsum 0-5 parts by mass; the raw material of the high-temperature calcined and activated slag is bauxite desilicon tailings.

2. The high temperature calcination-activated slag cement binder according to claim 1, characterized in that, The high-temperature calcined and activated slag is obtained by crushing, grinding and constant-temperature calcination of bauxite desilicon tailings.

3. The high temperature calcination-activated slag cement binder according to claim 2, characterized in that, The constant-temperature calcination temperature is 500-800℃.

4. The high temperature calcination-activated slag cement binder according to claim 3, characterized in that, The constant-temperature calcination time is 1-2.5h.

5. The high temperature calcination-activated slag cement binder according to claim 4, characterized in that, The constant-temperature calcination temperature is 500-800℃.

6. The high temperature calcination-activated slag cement binder according to claim 3, wherein, The constant-temperature calcination time is 1-2.5h.

7. The high temperature calcination-activated slag cement binder according to claim 6, characterized in that, The cement clinker is Portland cement clinker.

8. Process for the production of a high-temperature clinker-activated slag cement binder according to any one of claims 1-7, characterized in that, The purity of the gypsum is ≥90%. The steps are as follows: (1) crushing and grinding bauxite desilicon tailings, and then constant-temperature calcining at 500-800℃ for 1-2.5h to obtain high-temperature calcined and activated slag; 9. The method of producing a high temperature clinker-activated slag cement binder according to claim 8, characterized in that, (2) taking cement clinker, high-temperature calcined and activated slag and gypsum by mass parts, and mixing to obtain mixed powder, i.e. high-temperature calcined and activated slag cement base material. The stirring speed in step (2) is 150-300r / min, and the time is 10-20min.

10. Application of the high-temperature calcined and activated slag cement base material of claim 1 in preparing mortar or concrete.

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