Organic-inorganic composite alkali-activated cementing material and preparation method thereof

Abstract

The invention belongs to the technical field of cementing materials, and particularly relates to an organic-inorganic composite alkali-activated cementing material and a preparation method thereof. The modified wollastonite added into the organic-inorganic composite alkali-activated cementing material has a large amount of silicon hydroxyl (Si-OH), and the groups are high in activity, so that the compatibility and binding force of the wollastonite and the styrene butadiene rubber emulsion can be greatly improved. The modified wollastonite provides CaO and SiO2 at the same time, a hybridization system composed of N-A-S-H gel, C-A-S-H gel and unreacted wollastonite needle-shaped particles is formed, the hybridization system can force cracks to deflect, bypass and branch in the expansion process, more fracture energy is consumed, and therefore the fracture toughness and toughness of the material are improved.

Description

Technical Field

[0001] This invention belongs to the field of cementitious materials technology, specifically relating to an organic-inorganic composite alkali-activated cementitious material and its preparation method. Background Technology

[0002] With the rapid development of the building materials industry and the introduction of the national dual-carbon strategy, governments and scholars have begun to focus on the comprehensive utilization of solid waste to replace the traditional cement-based cementitious materials production process, which consumes a large amount of energy and emits a large amount of carbon dioxide, causing a serious burden on the environment. Alkali-activated cementitious materials, on the other hand, have lower energy consumption and no carbon dioxide emissions. In recent years, the preparation of high-ductility alkali-activated cementitious materials using industrial solid waste (such as mineral powder, fly ash, molybdenum tailings, and carbide slag) has become a research hotspot. However, existing alkali-activated cementitious materials generally suffer from the following problems: 1) High shrinkage: Due to the low activity of solid waste materials, shrinkage cracks are easily generated during the hardening process. 2) Low flexural strength: The limited cementitious properties of solid waste materials make it difficult for the mechanical properties (especially flexural strength) of the materials to meet engineering requirements. 3) The main disadvantage of alkali-activated materials (such as fly ash and slag-based polymers) is their high brittleness; their failure usually manifests as sudden and catastrophic fracture.

[0003] Therefore, developing a highly ductile cementitious material to overcome its shortcomings such as brittleness, easy cracking, and poor durability is of great scientific significance and engineering application value. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an organic-inorganic composite alkali-activated cementitious material and its preparation method.

[0005] The technical solution adopted in this invention is as follows: An organic-inorganic composite alkali-activated cementitious material, comprising the following raw materials by weight: 30-50 parts mineral powder, 10-30 parts steel slag, 10-25 parts molybdenum tailings, 3-8 parts calcium carbide slag, 5-10 parts water glass, 1-3 parts sodium carbonate, 0.1-0.5 parts lignin sulfonate, 0.05-0.3 parts retarder, 0.5-2 parts calcium stearate, 3-9 parts modified wollastonite, and 5-10 parts styrene-butadiene rubber latex.

[0006] The modified wollastonite is prepared by the following steps: calcining wollastonite at 800-1050℃ for 1-4 hours, grinding it until D50 < 10μm, adding a weak acid to the wollastonite at 20-60℃, soaking, washing, and drying to obtain the modified wollastonite.

[0007] The weak acid is citric acid, acetic acid, dilute phosphoric acid, or formic acid.

[0008] The retarder is boric acid or citric acid.

[0009] The water glass has a modulus of 1.2 and a mass fraction of 32.5%.

[0010] The D50 of the molybdenum tailings is 0.1-22.0 μm.

[0011] A method for preparing organic-inorganic composite alkali-activated cementitious materials includes the following steps: Wollastonite was calcined at 800-1050℃ for 1-4 hours, ground until D50 < 10μm, and then soaked in a weak acid at 20-60℃ for 2-8 hours. The filter cake was washed (repeatedly rinsed with hot deionized water at 60-80℃ until the pH of the filtrate reached about 7.0 to ensure that excess acid and dissolved calcium ions and other impurities were fully removed). The filter cake was dried to obtain modified wollastonite. The modified wollastonite was mixed with mineral powder, steel slag, molybdenum tailings, carbide slag, sodium carbonate, lignin sulfonate, retarder, and calcium stearate. Styrene-butadiene rubber latex and water glass (modulus 1.2, mass fraction 32.5%) were mixed evenly, and then added to the mixed powder obtained in step 2) and mixed evenly to obtain an organic-inorganic composite alkali-activated cementitious material.

[0012] In step 1), the drying process involves drying at 105-120℃ in a forced-air drying oven for 3-5 hours.

[0013] Compared with the prior art, the beneficial technical effects of the present invention are: This invention employs a combined calcination-acid etching method to activate and modify wollastonite. First, the raw wollastonite is calcined at a specific temperature. This process primarily removes adsorbed water and some structural hydroxyl groups from the mineral surface, causing lattice shrinkage and generating micro-stress, thereby enhancing its reactivity. Simultaneously, the thermal decomposition of certain associated impurities leaves micropores within the particles. Subsequently, the calcined product is ground to increase its specific surface area and introduce defects. Next, the calcined product powder is treated with a weak acid solution under mild conditions. The acid etching reaction selectively removes calcium from the surface. After the acid etching reaction, the powder is washed until neutral to ensure that excess acid and dissolved calcium ion impurities are fully removed, forming a porous active layer rich in amorphous silica. The newly formed silica layer contains a large number of silanol groups (Si-OH), which are highly reactive and can significantly improve the compatibility and bonding strength between wollastonite and styrene-butadiene rubber latex.

[0014] Furthermore, modified wollastonite simultaneously provides CaO and SiO2, which can participate in the reaction and promote CASH gel formation in an alkaline-activated environment. Low-calcium-to-silicon ratio CASH gels are more easily formed on and around the surface of wollastonite particles. Ultimately, the material matrix is ​​no longer a single NASH gel, but a hybrid system composed of NASH gel, CASH gel, and unreacted wollastonite needle-like particles. This multiphase structure is more effective at preventing rapid crack propagation than a single, homogeneous gel structure, thus exhibiting better toughness. Simultaneously, because the modified wollastonite maintains a high aspect ratio after grinding, these fine needle-like particles, dispersed in the alkaline-activated matrix, can act like "microfibers," ultimately forming a "microfiber" effect and bridging and deflecting cracks. When microcracks are generated in the matrix, these needle-like particles can bridge the cracks on both sides, preventing further propagation. More importantly, the hybrid system forces cracks to deflect, bypass, and branch during propagation, consuming more fracture energy, thereby improving the fracture toughness and overall toughness of the material.

[0015] The reaction between carbide slag and ammonium carbonate can not only generate CaCO3 particles, increasing nucleation sites, but also generate strong alkali NaOH, increasing the alkalinity of the solution. This promotes the participation of low-surface-activation-energy silicon-oxygen tetrahedra, iron-oxygen tetrahedra, and aluminum-oxygen octahedra in the hydration reaction of low-activity ultrafine-ground molybdenum tailings. Furthermore, it can promote the participation of silicates (CaO▪SiO2) in the hydration reaction of wollastonite, thus better forming a hybrid system structure.

[0016] Adding lignin sulfonate can reduce the water-cement ratio, increase the strength of cementitious materials, and improve their performance. However, given that alkali-activated cementitious materials react rapidly and uncontrollably under highly alkaline conditions, retarders are added to control the reaction.

[0017] During the hydration and curing process of alkali-activated materials, styrene-butadiene rubber (SBR) latex dehydrates and forms a film in a strongly alkaline environment. This film bridges cracks through physical action, and its curing does not require the addition of a curing agent. It forms a polymer film that effectively protects the interior, fills capillary pores, and inhibits moisture evaporation, thereby significantly reducing shrinkage and increasing the system's toughness. Simultaneously, some functional groups on the branch chains form alkaline bonds with the cementitious material, effectively bridging microcracks and improving tensile strength.

[0018] The cementitious materials prepared using the raw materials and methods of this invention have good tensile strength, elastic modulus, and durability, and have significant scientific and engineering application value. Detailed Implementation

[0019] The following examples illustrate specific implementations of the present invention. However, these examples are merely for illustrative purposes and do not limit the scope of the invention in any way.

[0020] Example 1: An organic-inorganic composite alkali-activated cementitious material, using the following raw materials: 4 kg of mineral powder, 2 kg of steel slag, 2 kg of molybdenum tailings (D50=9.1μm), 0.5 kg of calcium carbide slag, 0.8 kg of water glass, 0.2 kg of sodium carbonate, 0.03 kg of lignosulfonate, 0.02 kg of boric acid, 0.1 kg of calcium stearate, 0.5 kg of modified wollastonite, and 0.8 kg of styrene-butadiene rubber latex.

[0021] Preparation method: Wollastonite was calcined at 800℃ for 4 hours and ground until D50 < 10 μm. A weak acid was added to the wollastonite at 25℃ and soaked for 7 hours. The filter cake was repeatedly washed with hot deionized water at 60℃ until the pH value of the filtrate reached about 7.0. The filter cake was dried in a forced-air drying oven at 105℃ for 5 hours to obtain modified wollastonite. Take 4 kg of mineral powder, 2 kg of steel slag, 2 kg of molybdenum tailings, 0.5 kg of calcium carbide slag, 0.8 kg of water glass, 0.2 kg of sodium carbonate, 0.03 kg of lignin sulfonate, 0.02 kg of boric acid or citric acid, 0.1 kg of calcium stearate, 0.5 kg of modified wollastonite, and 0.8 kg of styrene-butadiene rubber latex. Mix the modified wollastonite with the mineral powder, steel slag, molybdenum tailings, calcium carbide slag, sodium carbonate, lignin sulfonate, boric acid or citric acid, and calcium stearate. Styrene-butadiene rubber latex and water glass (modulus 1.2, mass fraction 32.5%) were mixed evenly, and then added to the mixed powder obtained in step 2) and mixed evenly to obtain an organic-inorganic composite alkali-activated cementitious material.

[0022] Example 2: An organic-inorganic composite alkali-activated cementitious material, using the following raw materials: 3 kg of mineral powder, 3 kg of steel slag, 1 kg of molybdenum tailings (D50=22μm), 0.8 kg of calcium carbide slag, 0.5 kg of water glass, 0.3 kg of sodium carbonate, 0.01 kg of lignin sulfonate, 0.03 kg of citric acid, 0.05 kg of calcium stearate, 0.9 kg of modified wollastonite, and 0.5 kg of styrene-butadiene rubber latex.

[0023] Preparation method: Wollastonite was calcined at 1050℃ for 1 hour and ground until D50 < 10 μm. A weak acid was added to the wollastonite at 50℃ and soaked for 2 hours. The filter cake was repeatedly washed with hot deionized water at 80℃ until the pH value of the filtrate reached about 7.0. The filter cake was dried in a forced-air drying oven at 120℃ for 3 hours to obtain modified wollastonite. Take 4 kg of mineral powder, 2 kg of steel slag, 2 kg of molybdenum tailings, 0.5 kg of calcium carbide slag, 0.8 kg of water glass, 0.2 kg of sodium carbonate, 0.03 kg of lignin sulfonate, 0.02 kg of boric acid or citric acid, 0.1 kg of calcium stearate, 0.5 kg of modified wollastonite, and 0.8 kg of styrene-butadiene rubber latex. Mix the modified wollastonite with the mineral powder, steel slag, molybdenum tailings, calcium carbide slag, sodium carbonate, lignin sulfonate, citric acid, and calcium stearate. Styrene-butadiene rubber latex and water glass (modulus 1.2, mass fraction 32.5%) were mixed evenly, and then added to the mixed powder obtained in step 2) and mixed evenly to obtain an organic-inorganic composite alkali-activated cementitious material.

[0024] Example 3: An organic-inorganic composite alkali-activated cementitious material, using the following raw materials: 5 kg mineral powder, 1 kg steel slag, 2.5 kg molybdenum tailings (D50=2μm), 0.3 kg calcium carbide slag, 1 kg water glass, 0.1 kg sodium carbonate, 0.05 kg lignosulfonate, 0.01 kg boric acid, 0.2 kg calcium stearate, 0.3 kg modified wollastonite, and 1 kg styrene-butadiene rubber latex.

[0025] The preparation process is as described in Example 1.

[0026] Example 4: An alkali-activated cementitious material, the raw materials used are: 4 kg of mineral powder, 2 kg of steel slag, 2 kg of molybdenum tailings (D50=9.1μm), 0.5 kg of calcium carbide slag, 0.8 kg of water glass, 0.2 kg of sodium carbonate, 0.03 kg of lignin sulfonate, 0.02 kg of boric acid, 0.1 kg of calcium stearate, 0.5 kg of wollastonite, and 0.8 kg of styrene-butadiene rubber latex.

[0027] During preparation, refer to steps 2)-3) of Example 1.

[0028] Example 5: An alkali-activated cementitious material, the raw materials used are: 4 kg of mineral powder, 2 kg of steel slag, 2 kg of molybdenum tailings (D50=9.1μm), 0.8 kg of water glass, 0.2 kg of sodium carbonate, 0.03 kg of lignosulfonate, 0.02 kg of boric acid, 0.1 kg of calcium stearate, 0.5 kg of modified wollastonite, and 0.8 kg of styrene-butadiene rubber latex.

[0029] The preparation process is as described in Example 1.

[0030] Example 6: An alkali-activated cementitious material, the raw materials used are: 4 kg of mineral powder, 2 kg of steel slag, 2 kg of molybdenum tailings (D50=9.1μm), 0.5 kg of calcium carbide slag, 0.8 kg of water glass, 0.03 kg of lignosulfonate, 0.02 kg of boric acid, 0.1 kg of calcium stearate, 0.5 kg of modified wollastonite, and 0.8 kg of styrene-butadiene rubber latex.

[0031] Example 7: An organic-inorganic composite alkali-activated cementitious material, using the following raw materials: 4 kg of mineral powder, 2 kg of steel slag, 2 kg of molybdenum tailings (D50=9.1μm), 0.5 kg of calcium carbide slag, 0.8 kg of water glass, 0.2 kg of sodium carbonate, 0.03 kg of lignin sulfonate, 0.02 kg of boric acid, 0.1 kg of calcium stearate, and 0.5 kg of modified wollastonite.

[0032] The preparation process is as described in Example 1.

[0033] The alkali-activated gel materials prepared in Examples 1-7 were subjected to performance tests. The splitting tensile strength was tested according to GB / T 50081-2019; the compressive strength and flexural strength were tested according to GB / T 50081-2019; the elastic modulus was tested according to GB / T 50082-2009; the drying linear shrinkage was tested according to GB / T 50082-2009; and the durability (resistance to sulfate attack) was tested according to GB / T 50082-2009. The obtained data are shown in Table 1 below. When unmodified wollastonite is used in Example 4, due to its limited activity, it cannot effectively participate in the reaction in an alkaline-activated environment, cannot form CASH gel, and the hybridization system cannot be constructed. As a result, the splitting tensile strength, flexural strength, and durability resistance to sulfuric acid corrosion decrease, while the drying shrinkage value increases.

[0034] In Examples 5 and 6, the absence of calcium carbide slag or sodium carbonate resulted in the loss of some nucleation sites, which prevented the low surface activation energy silicon-oxygen tetrahedra, iron-oxygen tetrahedra, and aluminum-oxygen octahedra in molybdenum tailings from participating in the hydration reaction. This had a certain impact on the formation of the hybrid system and thus directly affected the strength of the cementitious material.

[0035] When styrene-butadiene rubber latex is lacking in Example 7, a polymer film cannot be formed, which affects the toughness of the system. It also lacks alkaline bonding with the gelling material, resulting in a decrease in splitting tensile strength and a significant increase in drying shrinkage.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. An organic-inorganic composite alkali-activated cementitious material, characterized in that, By weight, it includes the following raw materials: 30-50 parts mineral powder, 10-30 parts steel slag, 10-25 parts molybdenum tailings, 3-8 parts calcium carbide slag, 5-10 parts water glass, 1-3 parts sodium carbonate, 0.1-0.5 parts lignin sulfonate, 0.05-0.3 parts retarder, 0.5-2 parts calcium stearate, 3-9 parts modified wollastonite, and 5-10 parts styrene-butadiene rubber latex.

2. The organic-inorganic composite alkali-activated cementitious material according to claim 1, characterized in that: The modified wollastonite is prepared by the following steps: calcining wollastonite at 800-1050℃ for 1-4 hours, grinding, adding weak acid to wollastonite, soaking, washing, and drying to obtain modified wollastonite.

3. The organic-inorganic composite alkali-activated cementitious material according to claim 1 or 2, characterized in that: The weak acid is citric acid, acetic acid, dilute phosphoric acid, or formic acid.

4. The organic-inorganic composite alkali-activated cementitious material according to claim 1 or 2, characterized in that: The retarder is boric acid or citric acid.

5. The preparation method of the organic-inorganic composite alkali-activated cementitious material according to any one of claims 1-4, characterized in that, Includes the following steps: Wollastonite was calcined at 800-1050℃ for 1-4 hours, ground, soaked in a weak acid, washed, and dried to obtain modified wollastonite. The modified wollastonite was mixed with mineral powder, steel slag, molybdenum tailings, carbide slag, sodium carbonate, lignin sulfonate, retarder, and calcium stearate. Styrene-butadiene rubber latex and water glass were mixed evenly, and then added to the mixed powder obtained in step 2) and mixed evenly to obtain an organic-inorganic composite alkali-activated gelling material.

6. The preparation method according to claim 4, characterized in that: In step 1), the drying process is carried out at 105-120℃ for 3-5 hours.

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