Solid waste-based self-leveling repair mortar and preparation method thereof

Abstract

The application discloses a kind of solid waste-based self-leveling repair mortar and preparation method thereof, the mortar includes cementitious material, alkali activator, polypropylene fiber, water and sand;Cementitious material includes the following mass parts of raw materials: granulated blast furnace slag 70~90 parts and 10~30 parts of class volcanic ash raw material;Alkali activator mass is calculated as 5wt% by alkali equivalent;Polypropylene fiber mass is 0.3~0.5wt% of cementitious material mass;Water mass is calculated as water-binder ratio 0.40;Sand mass is calculated as mortar-sand ratio 1:1.5~1.7.The application overcomes the defects and deficiencies of existing solid waste-based repair mortar process, with the advantages of simple construction process, low shrinkage, high flexural strength, environmental friendly, low cost, good comprehensive performance, fully absorbs and utilizes bulk industrial solid waste, improves the utilization rate of resources.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a solid waste-based self-leveling repair mortar and its preparation method. Background Technology

[0002] Cracks are prevalent in concrete structures. Traditional cement-based repair materials are brittle, have low tensile strength, and insufficient durability, easily leading to secondary cracking and structural failure. Concrete cracks provide pathways for the penetration of harmful substances (CO2, sulfates, etc.), accelerating structural corrosion and threatening service life. Traditional inorganic repair materials face problems such as high cost, long setting time, insufficient bond strength, harsh construction conditions, and high resource consumption and emissions. Researching solid waste-based materials as raw materials for repair mortars aligns with current green and low-carbon development requirements.

[0003] Alkali-activated materials use industrial solid waste (slag, metakaolin, fly ash, and other polymers) as precursors, requiring no high-temperature calcination. They also reduce CO2 emissions by 80% compared to ordinary cement, and their life-cycle carbon emissions by 70%-80%, combining the advantages of low carbon footprint and solid waste resource utilization. Furthermore, alkali-activated cementitious materials exhibit rapid setting and hardening, high early strength, high strength, and excellent impermeability, making them suitable for repair materials and other fields. However, alkali-activated cementitious materials face challenges such as insufficient supply of high-quality raw materials and rising costs. Existing alkali-activated cementitious materials suffer from technical bottlenecks such as efflorescence and large shrinkage, restricting their application in engineering. Solving the problems of large shrinkage and efflorescence is key to the widespread application of alkali-activated materials in engineering.

[0004] Mine overburden contains heavy metals and acidic pollutants, and traditional stockpiling leads to ecological damage; its silicon and aluminum components provide potential raw materials for geopolymers. Solid waste from mine overburden and low-grade limestone industries can be lightly burned at 800℃ to produce volcanic ash-like raw materials, achieving a low-carbon and green goal. This not only alleviates stockpiling pollution and land occupation but also aligns with the "dual carbon" objective.

[0005] Patent CN112079594A discloses a geopolymer high-strength mortar for concrete structure repair and its preparation method. Its cementitious materials include mineral powder, metakaolin, and fly ash, while the fibers used are steel fibers and polyvinyl alcohol fibers. The use of metakaolin to prepare the pozzolanic material presents several challenges. First, metakaolin is a high-quality solid waste, found only in limited areas, and has a high calcination decomposition temperature, generally between 800℃ and 1000℃. This significantly increases the demand for coal, leading to increased CO2 emissions and hindering the goal of low carbon emissions. Second, steel fibers are expensive, and the addition of polyvinyl alcohol fibers negatively impacts the fluidity of the repair mortar.

[0006] Patent CN108585649A discloses a fly ash and mineral powder-based polymer fast-setting rigid repair mortar and its preparation method. The raw materials are tailings fine sand, fly ash, and mineral powder. To ensure the workability of the repair mortar, various admixtures, including redispersible latex powder, retarders, and water-retaining agents, are added. However, the large variety of admixtures does not consider compatibility with concrete, and the cost is relatively high. Summary of the Invention

[0007] To overcome the shortcomings and deficiencies of existing solid waste-based repair mortar construction processes, such as complex processes, large shrinkage, high emissions, and high pollution, this invention provides a repair mortar with simple construction process, low shrinkage, high flexural strength, environmental friendliness, low cost, and good comprehensive performance, as well as its preparation method. This fully utilizes large quantities of industrial solid waste and improves resource utilization.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] On the one hand, a solid waste-based self-leveling repair mortar is provided, comprising cementitious materials, alkali activator, polypropylene fiber, water, and sand; the cementitious materials comprise the following raw materials in parts by weight: 70-90 parts of granulated blast furnace ore powder and 10-30 parts of pozzolanic-like raw materials; the alkali activator is calculated based on an alkali equivalent of 5 wt%; the polypropylene fiber is 0.3-0.5 wt% of the cementitious materials; the water is calculated based on a water-cement ratio of 0.40; and the sand is calculated based on a cement-sand ratio of 1:1.5-1.7.

[0010] Furthermore, the granulated blast furnace ore powder is S95 grade ore powder.

[0011] Furthermore, the granulated blast furnace ore powder comprises the following chemical composition by mass percentage: CaO: 39.7 wt%, SiO2: 28.9 wt%, Al2O3: 14.0 wt%.

[0012] Furthermore, the volcanic ash-like raw material is prepared by lightly burning mine stripping waste soil and low-grade limestone, as detailed below:

[0013] Mine stripping waste soil and low-grade limestone were weighed according to a CaO / SiO2 molar ratio of 0.9 and pressed into cakes with water. The cakes were then placed in a muffle furnace and heated to 800°C at a rate of 15°C / min, and lightly calcined for 1 hour. After naturally cooling to room temperature, the cakes were then ground in a vibratory mill to a specific surface area of ​​400 m². 2 / kg.

[0014] Furthermore, the mine stripping waste soil comprises the following chemical composition by mass percentage: SiO2: 42.5–45.1 wt%, Al2O3: 12.4–14.2 wt%, CaO: 1.8–2.0 wt%.

[0015] The main mineral phases of the waste soil stripped from the mine are feldspar, quartz, muscovite, etc.

[0016] Furthermore, the low-grade limestone comprises the following chemical composition by mass percentage: SiO2: 5.8–6.2 wt%, Al2O3: 1.5–2.0 wt%, CaO: 46.1–47.5 wt%.

[0017] Furthermore, the alkali activator is a mixture of water glass, NaOH, and water with a modulus of 1.2 and a solid content of 25 wt%; the water glass is sodium water glass with a modulus of 3.01.

[0018] Furthermore, the polypropylene fiber has a length of 6 mm and a diameter of 20 μm.

[0019] Furthermore, the sand is natural river sand with a maximum particle size of 2.36 mm.

[0020] On the other hand, a method for preparing solid waste-based self-leveling repair mortar is provided, comprising the following steps:

[0021] S1. Mix the cementitious material, polypropylene fiber, and sand evenly in proportion to obtain a mixed dry material;

[0022] S2. Divide the water into two parts. Use one part to prepare the alkali activator, and mix the other part with the prepared alkali activator. Stir well and then pour it into a vertical mortar mixing pot.

[0023] S3. Pour the mixed dry materials into the vertical mortar mixing pot, stir at 60 r / min for 60 seconds, then stir at 120 r / min for 30 seconds, let stand still for 90 seconds, and then stir at 120 r / min for 60 seconds.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The raw materials for preparing solid waste-based self-leveling repair mortar are simple. Through the efficient utilization of bulk industrial solid waste (granulated blast furnace ore powder, mine stripping waste soil, low-grade waste limestone, etc.), a closed loop of "environmental governance-material development-engineering application" is realized. It has the advantages of low carbon, low cost and high performance, and is a key direction for promoting the transformation of green building materials.

[0026] 2. The volcanic ash raw material of this invention is prepared from mine overburden and low-grade limestone, solving the problems of land occupation and environmental pollution. From the perspective of raw materials, mine overburden differs from high-quality kaolin with high aluminum content, and has lower requirements for soil quality. Moreover, for mine overburden and low-grade limestone from different regions, similar effects can be achieved by controlling their calcium-silicon ratio, with minimal performance fluctuations.

[0027] 3. This invention uses a pozzolanic-like raw material to partially replace blast furnace ore powder. Due to the synergistic effect of the blast furnace ore powder and the pozzolanic-like raw material, the number of crystals in the hydration products increases, making the mortar system more compact. This effectively inhibits shrinkage caused by CASH gelation and significantly enhances the flexural strength of the repair mortar. In addition, the low water absorption of the pozzolanic-like raw material reduces the water demand of the system and greatly increases the fluidity of the self-leveling repair mortar.

[0028] 4. When the alkali activator is prepared using water glass in this invention, the slurry has good fluidity, and after hardening, it also has high mechanical properties, durability, good cost control, and good environmental adaptability.

[0029] 5. The solid waste-based self-leveling repair mortar prepared by this invention has good fluidity, high interfacial bonding strength, flexural strength and compressive strength, reduces shrinkage and enhances the repair effect. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] Example 1

[0032] As a preferred embodiment of the present invention, the solid waste-based self-leveling repair mortar of this embodiment includes (by mass parts) 90 parts granulated blast furnace ore powder, 10 parts volcanic ash-like raw materials, 43.3 parts alkali activator, 0.3 parts polypropylene fiber, 150 parts sand, and 7.53 parts water. The water mass is calculated by subtracting the water mass in the alkali activator from the total water mass calculated with a water-cement ratio of 0.40.

[0033] Example 2

[0034] As a preferred embodiment of the present invention, the solid waste-based self-leveling repair mortar of this embodiment includes (by mass parts) 80 parts granulated blast furnace ore powder, 20 parts volcanic ash-like raw materials, 43.3 parts alkali activator, 0.4 parts polypropylene fiber, 160 parts sand, and 7.53 parts water. The water mass is calculated by subtracting the water mass in the alkali activator from the total water mass calculated with a water-cement ratio of 0.40.

[0035] Example 3

[0036] As a preferred embodiment of the present invention, the solid waste-based self-leveling repair mortar of this embodiment includes (by mass parts) 70 parts granulated blast furnace ore powder, 30 parts volcanic ash-like raw materials, 43.3 parts alkali activator, 0.5 parts polypropylene fiber, 170 parts sand, and 7.53 parts water. The water mass is calculated by subtracting the water mass in the alkali activator from the total water mass calculated with a water-cement ratio of 0.40.

[0037] Comparative Example 1

[0038] The mortar composition of this comparative example is the same as that of Example 2, except that the cementitious material is replaced with P·O 42.5 cement and no alkali activator is added.

[0039] Comparative Example 2

[0040] The mortar composition of this comparative example is the same as that of Example 2, except that the cementitious material contains only granulated blast furnace ore powder.

[0041] Comparative Example 3

[0042] The mortar composition in this comparative example is the same as that in Example 2, except that the pozzolanic raw material is replaced with P·O 42.5 cement.

[0043] Test case

[0044] The basic properties of the mortars in each embodiment and comparative example were tested, and the test results are shown in Table 1.

[0045] Table 1. Basic performance test results of mortars in each embodiment and comparative example.

[0046]

[0047] The data in Table 1 show that the flexural strength, compressive strength, and bond strength of the repair mortars in Examples 1 to 3 all meet the standards. The addition of pozzolanic raw materials in the examples significantly improved the flowability of the repair mortars, and Example 2 has better overall performance.

[0048] Compared to Comparative Example 1, which only added P·O 42.5 cement, Example 2 showed an increase in 3-day and 28-day flexural strength of 73.0% and 50.0%, respectively; an increase in 3-day and 28-day compressive strength of 63.5% and 43.4%, respectively; and an increase in bond strength of 41.4%. Compared to Comparative Example 2, which only added blast furnace slag powder, Example 2 showed an increase in 3-day and 28-day flexural strength of 51.4% and 41.9%, respectively; an increase in 3-day and 28-day compressive strength of 24.3% and 28.5%, respectively; and an increase in bond strength of 32.3%. Compared to Comparative Example 3, Example 2 showed an increase in 3-day and 28-day flexural strength of 23.9% and 14.8%, respectively; an increase in 3-day and 28-day compressive strength of 19.9% ​​and 20.9%, respectively; and an increase in bond strength of 20.6%.

[0049] In summary, the solid waste-based self-leveling repair mortar of this invention exhibits good flowability and high flexural strength even in its early stages. The addition of pozzolanic-like raw materials significantly improves the flowability of this self-leveling repair mortar. This is due, on the one hand, to the low water requirement of the pozzolanic-like raw materials; and on the other hand, the increased glass content of the pozzolanic-like raw materials, obtained by lightly calcining mine stripping waste soil and low-grade limestone, reduces the frictional stress of the mortar system, thus increasing flowability. The synergistic effect of the pozzolanic-like raw materials and blast furnace ore powder increases the system's density and strength.

[0050] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A self-leveling repair mortar based on solid waste, characterized in that, The product includes cementitious materials, alkali activator, polypropylene fiber, water, and sand. The cementitious materials consist of the following raw materials by weight: 70-90 parts granulated blast furnace ore powder and 10-30 parts pozzolanic-like raw materials; the alkali activator is calculated based on an alkali equivalent of 5 wt%; the polypropylene fiber is 0.3-0.5 wt% of the cementitious materials; the water is calculated based on a water-cement ratio of 0.40; and the sand is calculated based on a cement-sand ratio of 1:1.5-1.

7. The volcanic ash-like raw material is prepared by lightly burning mine stripping waste soil and low-grade limestone, as detailed below: Mine stripping waste soil and low-grade limestone were weighed according to a CaO / SiO2 molar ratio of 0.9 and pressed into cakes with water. The cakes were then placed in a muffle furnace and heated to 800°C at a rate of 15°C / min, and lightly calcined for 1 hour. After naturally cooling to room temperature, the cakes were then ground in a vibratory mill to a specific surface area of ​​400 m². 2 / kg; The alkaline activator is a mixture of water glass, NaOH and water with a modulus of 1.2 and a solid content of 25 wt%.

2. The self-leveling repair mortar for solid waste base according to claim 1, characterized in that, The granulated blast furnace ore powder is S95 grade ore powder.

3. The self-leveling repair mortar for solid waste base according to claim 1, characterized in that, The granulated blast furnace ore powder comprises the following chemical composition by mass percentage: CaO: 39.7wt%, SiO2: 28.9wt%, Al2O3: 14.0wt%.

4. The self-leveling repair mortar for solid waste base according to claim 1, characterized in that, The mine overburden includes the following chemical composition by mass percentage: SiO2: 42.5~45.1wt%, Al2O3: 12.4~14.2wt%, CaO: 1.8~2.0wt%.

5. The self-leveling repair mortar for solid waste base according to claim 1, characterized in that, The low-grade limestone comprises the following chemical composition by mass percentage: SiO2: 5.8~6.2wt%, Al2O3: 1.5~2.0wt%, CaO: 46.1~47.5wt%.

6. The self-leveling repair mortar based on solid waste according to claim 1, characterized in that, The water glass is sodium silicate with a modulus of 3.

01.

7. The self-leveling repair mortar for solid waste base according to claim 1, characterized in that, The polypropylene fiber has a length of 6 mm and a diameter of 20 μm.

8. The self-leveling repair mortar for solid waste base according to claim 1, characterized in that, The sand is natural river sand with a maximum particle size of 2.36 mm.

9. A method for preparing a solid waste-based self-leveling repair mortar according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Mix the cementitious material, polypropylene fiber, and sand evenly in proportion to obtain a mixed dry material; S2. Divide the water into two parts. One part is used to prepare the alkali activator, and the other part is mixed with the prepared alkali activator and stirred evenly. Then pour it into the vertical mortar mixing pot. S3. Pour the mixed dry materials into the vertical mortar mixing pot, stir at 60 r / min for 60 seconds, then stir at 120 r / min for 30 seconds, let stand still for 90 seconds, and then stir at 120 r / min for 60 seconds.

Images