Preparation method of marine resource-based alkali-activated cementitious material

Abstract

A preparation method of marine resource-based alkali-activated cementitious material, comprising the following steps: (1) uniformly mixing and compacting 38 parts of diatomite and 62 parts of coral powder to obtain a mixture; (2) calcining the mixture obtained in step (1) at 800-900 DEG C for 4 hours to obtain a material with a hardened state; (3) cooling, crushing, ball milling and sieving the material with a hardened state obtained in step (2) to 80 mu m or less to obtain a precursor with volcanic ash activity; (4) mixing the precursor, an alkali activator and water according to a mass ratio of 56.17:21.25:22.58, stirring at 1000 r / min for 2 minutes and pouring into a mold to form, and curing under standard curing conditions of a temperature of 20 DEG C + / - 2 DEG C and RH of 90% + / - 5% to obtain the marine resource-based alkali-activated cementitious material. The marine resource-based alkali-activated cementitious material in the application can be obtained from the sea, and the calcination temperature is lower than the firing temperature of ordinary Portland cement, which provides a new idea for the local material supply and low-carbon development of building materials for island reef construction.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically a method for preparing a marine resource-based alkali-activated cementitious material. Background Technology

[0002] The islands and reefs in the South China Sea are located in tropical current-prone areas and are frequently hit by typhoons. Their main component is loose calcareous sand, making them extremely fragile and easily damaged, potentially causing significant property loss and even threatening lives. Therefore, constructing stable island and reef foundations is essential. Currently, the more mature methods for island and reef reinforcement include dynamic compaction, mechanical rolling, vibro-compaction (grouting), and microbial calcium carbonate-induced sedimentation technology. Grouting is one of the more commonly used methods; however, transporting reinforcement materials such as silicate cement from inland areas is inconvenient and costly. Utilizing marine resources to prepare new green cementitious materials would not only facilitate the use of locally sourced materials but also avoid the problems of high transportation costs.

[0003] Alkali-activated cementitious materials are a novel, low-carbon building material. They can be prepared by mixing industrial solid wastes such as slag, fly ash, steel slag, and red mud, or natural aluminosilicates such as metakaolin, with alkali activators (sodium hydroxide / potassium hydroxide, water glass) as precursors, resulting in a three-dimensional network gel structure. Due to different precursor compositions, the gels of alkali-activated cementitious materials are mainly classified into two types: C-(A)-SH and NASH. Therefore, silicon is one of the essential elements for preparing cementitious materials. Based on the necessary constituent elements of alkali-activated cementitious materials, utilizing marine resources such as calcium and silicon (coral, diatomaceous earth) to prepare cementitious materials for use in island and reef construction would not only achieve the rational utilization of marine resources but also avoid the inconvenience of transporting cementitious materials from outside. However, how to prepare a novel low-carbon cementitious material using diatomaceous earth and coral presents a challenge for those in this technical field. Summary of the Invention

[0004] In view of this, the present invention proposes a method for preparing marine resource-based alkali-activated cementitious materials to solve or at least partially solve the problems of inconvenient and expensive transportation of building materials (such as cement, aggregates, etc.) from the inland during the reinforcement and construction of islands and reefs.

[0005] The technical solution of this invention is: to provide a method for preparing a marine resource-based alkali-activated cementitious material, comprising the following steps:

[0006] (1) Mix 38 parts of diatomaceous earth and 62 parts of coral powder evenly and compact them to obtain a mixture;

[0007] (2) The mixture obtained in step (1) is calcined at 800-900℃ for 4 hours to obtain a material with a caking state;

[0008] (3) Cool, crush, ball mill and sieve the caking material obtained in step (2) to below 80 μm to obtain a precursor with pozzolanic activity;

[0009] (4) The above-mentioned precursor, alkali activator and water are mixed at a mass ratio of 56.17:21.25:22.58 and stirred at 1000r / min for 2 minutes and cast into shape. The marine resource-based alkali activated cementitious material is obtained by curing under the standard curing conditions of temperature 20±2℃ and RH 90%±5%.

[0010] The diatomaceous earth and coral powder in step (1) have a particle size of less than 80 μm.

[0011] The cooling method in step (3) is natural cooling or air cooling.

[0012] The precursor particle size after sieving in step (3) is less than 80 μm.

[0013] The alkaline activator in step (4) is industrial water glass, sodium hydroxide and water.

[0014] The alkaline activator is industrial water glass liquid with a modulus of 1.0 to 2.0. The modulus refers to the molar ratio of silicon dioxide to sodium oxide in the water glass, i.e., M = n(SiO2) / n(Na2O).

[0015] The present invention has the following beneficial effects:

[0016] 1) The raw materials used (diatomaceous earth and coral) can all be obtained from the ocean, realizing the utilization of marine resources and reducing the inconvenience and cost of transporting cementitious materials from inland areas.

[0017] 2) The calcination temperature in this invention is 800-900℃, which is much lower than the firing temperature of ordinary silicate cement (1400℃), greatly reducing production costs and energy consumption. Attached Figure Description

[0018] Figure 1 The XRD patterns of diatomaceous earth and coral powder and the standard card of aragonite (PDF#41-1475) described in this invention are shown.

[0019] Figure 2 The XRD patterns are of the pozzolanic active precursors prepared at different calcination temperatures (a) and air cooling (b) according to the present invention.

[0020] Figure 3 The images show the FTIR spectra of the pozzolanic active precursors prepared at different calcination temperatures (a) and air cooling (b) according to the present invention.

[0021] Figure 4The 28-day compressive strength of marine resource-based alkali-activated cementitious materials prepared under different calcination temperatures and air cooling conditions according to this invention is shown. Detailed Implementation

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

[0023] Example 1

[0024] This embodiment is an example of the preparation method of the marine resource-based alkali-activated cementitious material of the present invention, including the following steps:

[0025] (1) Mix 38 parts of diatomaceous earth and 62 parts of coral powder evenly and compact them to obtain a mixture;

[0026] (2) The mixture obtained in step (1) is calcined at 800°C for 4 hours to obtain a material with a caking state;

[0027] (3) After the material with a caking state obtained in step (2) is naturally cooled, it is crushed, ball-milled and sieved to below 80 μm to obtain a precursor with volcanic ash activity;

[0028] (4) The precursor, liquid water glass with a modulus of 1.0 and water are mixed in a mass ratio of 56.17:21.25:22.58 and stirred at 1000 r / min for 2 minutes and then cast into a mold. After curing for one day under standard conditions of 20±2℃ and RH90%±5%, the mold is removed. The demolded test block is then cured for 28 days and then subjected to a compressive strength test.

[0029] The compressive strength of the marine resource-based alkali-activated cementitious material prepared in Example 1 was 9.00 MPa.

[0030] Example 2

[0031] This embodiment is another example of the preparation method of the marine resource-based alkali-activated cementitious material described in this invention, including the following steps:

[0032] (1) Mix 38 parts of diatomaceous earth and 62 parts of coral powder evenly and compact them to obtain a mixture;

[0033] (2) The mixture obtained in step (1) is calcined at 850°C for 4 hours to obtain a material with a caking state;

[0034] (3) After the material with a caking state obtained in step (2) is naturally cooled, it is crushed, ball-milled and sieved to below 80 μm to obtain a precursor with volcanic ash activity;

[0035] (4) The precursor, liquid water glass with a modulus of 1.0 and water are mixed in a mass ratio of 56.17:21.25:22.58 and stirred at 1000 r / min for 2 minutes and then cast into a mold. After curing for one day under standard conditions of 20±2℃ and RH90%±5%, the mold is removed. The demolded test block is then cured for 28 days and then subjected to a compressive strength test.

[0036] The compressive strength of the marine resource-based alkali-activated cementitious material prepared in Example 2 was tested and found to be 10.75 MPa.

[0037] Example 3

[0038] This embodiment is another example of the preparation method of the marine resource-based alkali-activated cementitious material described in this invention, including the following steps:

[0039] (1) Mix 38 parts of diatomaceous earth and 62 parts of coral powder evenly and compact them to obtain a mixture;

[0040] (2) The mixture obtained in step (1) is calcined at 900°C for 4 hours to obtain a material with a caking state;

[0041] (3) After the material with a caking state obtained in step (2) is naturally cooled, it is crushed, ball-milled and sieved to below 80 μm to obtain a precursor with volcanic ash activity;

[0042] (4) The precursor, liquid water glass with a modulus of 1.0 and water are mixed in a mass ratio of 56.17:21.25:22.58 and stirred at 1000 r / min for 2 minutes and then cast into a mold. After curing for one day under standard conditions of 20±2℃ and RH90%±5%, the mold is removed. The demolded test block is then cured for 28 days and then subjected to a compressive strength test.

[0043] The compressive strength of the marine resource-based alkali-activated cementitious material prepared in Example 3 was tested and found to be 11.80 MPa.

[0044] Comparative Example

[0045] This embodiment is a comparative example of the preparation method of the marine resource-based alkali-activated cementitious material of the present invention, including the following steps:

[0046] (1) Mix 38 parts of diatomaceous earth and 62 parts of coral powder evenly and compact them to obtain a mixture;

[0047] (2) The mixture obtained in step (1) is calcined at 800°C for 4 hours to obtain a material with a caking state;

[0048] (3) After air cooling (800~AC) of the caking material obtained in step (2), crush, ball mill and sieve to below 80μm to obtain a precursor with volcanic ash activity;

[0049] (4) The precursor, liquid water glass with a modulus of 1.0 and water are mixed in a mass ratio of 56.17:21.25:22.58 and stirred at 1000 r / min for 2 minutes and then cast into a mold. After curing for one day under standard conditions of 20±2℃ and RH90%±5%, the mold is removed. The demolded test block is then cured for 28 days and then subjected to a compressive strength test.

[0050] The compressive strength of the marine resource-based alkali-activated cementitious material prepared in Comparative Example 1 was tested and found to be 9.23 MPa.

[0051] Table 1 Chemical composition of diatomaceous earth and coral powder

[0052] raw materials CaO <![CDATA[SiO2]]> SrO <![CDATA[Na2O]]> <![CDATA[Al2O3]]> MgO <![CDATA[SO3]]> Cl <![CDATA[Fe2O3]]> F <![CDATA[K2O]]> LOI Coral powder 49.08 4.77 0.84 0.825 0.81 0.67 0.56 0.46 0.35 0.26 0.15 41.10 diatomite 1.01 73.35 0.005 4.57 13.35 0.16 0.03 0.05 0.98 ～ 4.98 1.25

[0053] The chemical composition of the raw materials (coral, diatomaceous earth) used in the embodiments and comparative examples of this application is shown in Table 1. As can be seen from Table 1, diatomaceous earth is mainly composed of SiO2, Al2O3, Na2O, and K2O, with SiO2 content as high as 73.35%; coral powder is mainly composed of CaO and SiO2, and has a high loss on ignition (41.10%). The XRD patterns of the raw materials (…) Figure 1 Based on the chemical composition, it can be seen that diatomite has a relatively broad diffuse peak between diffraction angles of 15° and 35°, indicating that diatomite mainly exists in the form of microcrystalline or semi-crystalline SiO2 (diatom opal); while coral is mainly composed of aragonite-type calcium carbonate (PDF#41-1475).

[0054] Table 2 shows the results obtained under different experimental conditions in Examples 1 to 3 and the comparative examples.

[0055] Example Example 1 Example 2 Example 3 Comparative Example Calcination temperature (°C) 800 850 900 800 Cooling method Natural cooling Natural cooling Natural cooling Air cooling (AC) 28-day compressive strength (MPa) 9.00 10.75 11.80 9.23

[0056] The experimental results in Table 2 show that when the calcination temperature is 800℃, the 28-day compressive strength of the marine resource-based alkali-activated cementitious material is 9.00 MPa; when the calcination temperature is increased to 900℃, its 28-day compressive strength is 11.80 MPa, an increase of 31.11%. This indicates that as the calcination temperature of the raw materials increases, the compressive strength of the marine resource-based alkali-activated cementitious material prepared from them also increases. Comparison of Example 1 and the comparative example reveals that when air cooling is used, the compressive strength of the alkali-activated cementitious material is higher, but the increase is smaller.

Claims

1. A method for preparing a marine resource-based alkali-activated cementitious material, characterized in that, Includes the following steps: (1) Mix 38 parts of diatomaceous earth and 62 parts of coral powder evenly and compact them to obtain a mixture; (2) The mixture obtained in step (1) is calcined at 800-900 °C for 4 hours to obtain a material with a caking state; (3) Cool, crush, ball mill and sieve the material in the caking state obtained in step (2) to below 80 µm to obtain a precursor with pozzolanic activity; (4) The precursor, alkali activator and water are mixed at a mass ratio of 56.17:21.25:22.58 and stirred at 1000 r / min for 2 minutes and cast into a mold. The marine resource-based alkali-activated cementitious material is obtained by curing under standard curing conditions of 20±2 ℃ and RH90%±5%.

2. The method for preparing marine resource-based alkali-activated cementitious materials according to claim 1, characterized in that, The diatomaceous earth and coral powder in step (1) have a particle size of less than 80 µm.

3. The method for preparing marine resource-based alkali-activated cementitious materials according to claim 1, characterized in that, The cooling method in step (3) is natural cooling or air cooling.

4. The method for preparing marine resource-based alkali-activated cementitious materials according to claim 1, characterized in that, The precursor particle size after sieving in step (3) is less than 80 μm.

5. The method for preparing marine resource-based alkali-activated cementitious materials according to claim 1, characterized in that, The alkaline activator in step (4) is liquid water glass, which is composed of industrial water glass, sodium hydroxide and water.

6. The method for preparing marine resource-based alkali-activated cementitious materials according to claim 5, characterized in that, The modulus of the alkali activator is 1.0 to 2.0.

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