Industrial solid waste cementing material for roads and preparation method thereof

Abstract

The invention relates to the technical field of building materials, in particular to an industrial solid waste cementing material for roads and a preparation method thereof. The industrial solid waste cementing material for roads comprises the following components in parts by weight: 50-70 parts of slag powder; 20 to 30 parts of fly ash; 1-20 parts of steel slag; 3-10 parts of desulfurized gypsum; 5-30 parts of a composite activator; and 0-10 parts of a functional additive. Through the synergistic effect of the composite exciting agent, mechanical activation and the functional additive, the contradiction between strength and expansion rate caused by a single exciting agent is solved, and the high performance of the solid waste cementing material is realized. The harsh requirements of road engineering on strength and durability are met, the heavy metal leaching concentration is lower than the national standard limit value, and green transformation of road construction is promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to an industrial solid waste cementitious material for roads and a preparation method thereof. BACKGROUND

[0002] With the rapid development of transportation infrastructure, the performance requirements of cementitious materials for road engineering are increasingly stringent. Traditional cement-based materials are prone to cracking, peeling and other problems under heavy traffic, temperature changes and chemical corrosion. Traditional cement production has high energy consumption (about 8% of global carbon emissions) and large resource consumption, so it is urgent to develop low-carbon and environmentally friendly alternative materials. Traditional industrial solid wastes (such as slag powder, fly ash, and steel slag) have potential cementitious activity, but direct utilization has the following problems: the inert layer on the surface of solid waste particles hinders the hydration reaction, resulting in slow strength development; the hydration expansion of free calcium oxide (f-CaO) in steel slag easily causes cracking; single activator (such as alkali activation) easily leads to microcracks, and the composition of solid waste is complex, so it is difficult to precisely control the hydration rate and strength development with a single activation method.

[0003] In the prior art, the active components (such as CaO, SiO2, and Al2O3) of industrial solid waste (such as slag, fly ash, and steel slag) usually exist in the form of glass or stable crystals, which are difficult to hydrate quickly at room temperature. The activator efficiency is insufficient: if the concentration of alkali activator (such as NaOH and water glass) is too low or the dosage of sulfate (such as gypsum) is insufficient, it is difficult to quickly destroy the glass structure of solid waste, resulting in a small amount of early hydration products (such as C-S-H gel). The generation of early hydration products (such as C-S-H gel) is the core of the strength development of cementitious materials, and the insufficient generation will directly affect the early strength, setting time, and durability of the material. SUMMARY

[0004] The present application provides an industrial solid waste cementitious material for roads and a preparation method thereof to solve the technical problem of the contradiction between strength and expansion rate and setting time caused by the lack of activator and the defect of activation mechanism when the traditional solid waste material has a large amount of admixture in the prior art.

[0005] To solve the above problems, the present application provides an industrial solid waste cementitious material for roads and a preparation method thereof, which adopts the following technical scheme: The industrial solid waste cementitious material for roads comprises the following components by weight: 50-70 parts of slag powder, 20-30 parts of fly ash, 1-20 parts of steel slag, 3-10 parts of desulfurization gypsum, 5-30 parts of a composite activator, and 0-10 parts of a functional additive.

[0006] Further, the composite activator comprises an alkali activator and a sulfate activator, and the molar ratio of the alkali activator to the sulfate activator is (0.5-2) : 1.

[0007] Furthermore, the alkaline activator is NaOH or water glass or a mixture of both.

[0008] Furthermore, the sulfate activator is gypsum or Na2SO4 or a mixture of both.

[0009] Furthermore, the functional additive is 1-3 parts of nano-SiO2, wherein the particle size of nano-SiO2 is 10-50 nm and the specific surface area is ≥500 m² / g.

[0010] Furthermore, the functional additive is 5-10 parts of aluminate cement.

[0011] Furthermore, the functional additive is 5-10 parts of a chemical coagulant, wherein the chemical coagulant is at least one of CaCl2 and Na2CO3.

[0012] A method for preparing an industrial solid waste cementitious material for road use, as described above, includes the following steps: S1. Raw material pretreatment: Slag powder, fly ash, steel slag and desulfurized gypsum are respectively subjected to ultrafine grinding to a specific surface area ≥500 m² / kg; To prevent steel slag from expanding later, it is necessary to store it in an open-air manner. The open-air storage period for steel slag is 12-15 days. S2. Activation treatment: Mix the pretreated raw materials evenly according to the required weight parts, then add the composite activator and perform mechanical activation treatment. S3, Durability Control Treatment: Functional additives are added to the S2 material and mixed evenly.

[0013] Furthermore, the mechanical activation treatment specifically involves ball milling, and the ball milling time is at least 30 minutes.

[0014] Furthermore, after the mixture in S3 is thoroughly mixed, it is subjected to steam curing treatment, specifically at 60~80℃ for 4~8 hours.

[0015] The beneficial effects of the road industrial solid waste cementitious material and its preparation method provided by this invention are: 1. This invention achieves synergistic and complementary activation. The alkali:sulfate molar ratio (0.5-2:1) balances hydration rate and volume stability. Examples 1-3 show an expansion rate ≤0.05%, superior to traditional solid waste materials. Through the synergistic effect of composite activators, mechanical activation, and functional additives, the contradiction between strength and expansion rate caused by a single activator is resolved, achieving high performance in solid waste cementitious materials. Performance is comparable to ordinary cement (28-day strength 40-60 MPa), with an expansion rate ≤0.05%, meeting the stringent strength and durability requirements of road engineering. With a solid waste content ≥80%, carbon emissions are reduced by more than 50%, and heavy metal leaching concentrations are below national standard limits, promoting the green transformation of road construction.

[0016] 2. Synergistic effect of mechanical activation and chemical stimulation. The specific surface area of ​​solid waste is ≥500 m² / kg, which promotes the penetration and reaction of activators. The increased surface defects of particles after ball milling increase the density of hydration active sites. Nano-SiO2 fills microcracks, and the micro-expansion of steel slag compensates for shrinkage, providing dual protection to reduce the risk of cracking. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Those skilled in the art should understand that the embodiments described below are only some, not all, of the embodiments disclosed. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] The principles and spirit of the present invention will be explained in detail below with reference to several representative embodiments.

[0019] Example 1 of an industrial solid waste cementitious material for road use provided by the present invention: It comprises the following components by weight: 60 parts slag powder; 25 parts fly ash; 10 parts steel slag; 5 parts desulfurized gypsum; 20 parts composite activator; and 3 parts functional additives.

[0020] The molar ratio of the alkali activator NaOH to the sulfate activator Na2SO4 is 1:1.

[0021] The functional additive is 1-3 parts of nano-SiO2, wherein the particle size of nano-SiO2 is 10-50nm and the specific surface area is ≥500 m² / g.

[0022] The above-mentioned method for preparing industrial solid waste cementitious materials for roads includes the following steps: S1. Raw material pretreatment: Slag powder, fly ash, steel slag and desulfurized gypsum are respectively subjected to ultrafine grinding to a specific surface area ≥500 m² / kg; To prevent the steel slag from expanding later, it is stored in an open-air manner for 14 days.

[0023] S2. Activation treatment: Mix the pretreated raw materials evenly according to the required weight proportions, then add the composite activator and perform mechanical activation treatment. Specifically, the mechanical activation treatment involves ball milling for 50 minutes.

[0024] S3. Durability conditioning treatment: Functional additives are added to the S2 material and mixed evenly. Then, steam curing is performed at 60-80℃ for 4-8 hours.

[0025] Example 2 of an industrial solid waste cementitious material for road use provided by the present invention: It includes the following components by weight: 52 parts slag powder; 30 parts fly ash; 5 parts steel slag; 8 parts desulfurized gypsum; 25 parts composite activator; and 8 parts functional additives.

[0026] The molar ratio of the alkali activator water glass to the sulfate activator gypsum is 1.5:1.

[0027] The functional additive is 8 parts of aluminate cement.

[0028] The above-mentioned method for preparing industrial solid waste cementitious materials for roads includes the following steps: S1. Raw material pretreatment: Slag powder, fly ash, steel slag and desulfurized gypsum are respectively subjected to ultrafine grinding to a specific surface area ≥500 m² / kg; To prevent the steel slag from expanding later, it is stored in an open-air manner for 15 days. S2. Activation treatment: Mix the pretreated raw materials evenly according to the required weight proportions, then add the composite activator and perform mechanical activation treatment. Specifically, the mechanical activation treatment involves ball milling for 30 minutes.

[0029] S3. Durability control treatment: Add functional additives to the S2 material and mix thoroughly. After thorough mixing, perform steam curing treatment, specifically at 60~80℃ for 4~8 hours.

[0030] Example 3 of an industrial solid waste cementitious material for road use provided by the present invention: It comprises the following components by weight: 70 parts slag powder; 20 parts fly ash; 1 part steel slag; 3 parts desulfurized gypsum; 5 parts composite activator; and 10 parts functional additives.

[0031] The molar ratio of the alkali activator NaOH to the sulfate activator gypsum is 0.5:1.

[0032] The functional additive is 1 part of nano-SiO2, wherein the particle size of nano-SiO2 is 10-50nm and the specific surface area is ≥500 m² / g.

[0033] The functional additives also include 8 parts of a chemical coagulant, wherein the chemical coagulant is CaCl2.

[0034] The above-mentioned method for preparing industrial solid waste cementitious materials for roads includes the following steps: S1. Raw material pretreatment: Slag powder, fly ash, steel slag and desulfurized gypsum are respectively subjected to ultrafine grinding to a specific surface area ≥500 m² / kg.

[0035] To prevent the steel slag from expanding later, it is stored in an open-air manner for 15 days. S2. Activation treatment: Mix the pretreated raw materials evenly according to the required weight proportions, then add the composite activator and perform mechanical activation treatment. Specifically, the mechanical activation treatment involves ball milling for 30 minutes.

[0036] S3, Durability Control Treatment: Functional additives are added to the S2 material and mixed evenly.

[0037] Comparative Example 1 Ordinary PO 42.5 cement was selected, and the aggregate was standard sand according to ISO 679.

[0038] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that no composite activator was added and no mechanical activation treatment was performed during the preparation process.

[0039] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that only 10 parts of the alkaline activator NaOH in the composite activator were added.

[0040] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that only 10 parts of the sulfate activator Na2SO4 in the composite activator were added.

[0041] Comparative Example 5 The difference between Comparative Example 4 and Example 1 is that the mechanical activation treatment by ball milling during the preparation process takes 10 minutes.

[0042] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that no mechanical activation treatment is performed during the preparation process.

[0043] Comparative Example 7 The difference between Comparative Example 7 and Example 1 is that the molar ratio of the alkali activator NaOH to the sulfate activator gypsum is 0.2:1.

[0044] Comparative Example 8 The difference between Comparative Example 8 and the Example is that the molar ratio of the alkali activator NaOH to the sulfate activator gypsum is 3:1.

[0045] 1. Strength test: Samples from Examples 1-3 and Comparative Examples 1-6 were subjected to phased strength tests.

[0046] 2. The initial setting time and final setting time were determined in accordance with GB / T 1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement".

[0047] 3. Conduct expansion rate testing according to GB / T 23439-2017.

[0048] 4. Heavy metal leaching test shall be conducted in accordance with GB 5085.3-2007.

[0049] As shown in the table below: Comparing the above test data, Examples 1-3 and Comparative Example 3 exhibit the drawbacks of using a single activator. With only an alkali activator, the 28-day strength is only 22 MPa, the expansion rate is 0.08%, and excessive OH⁻ easily leads to microcracks. In Comparative Example 4, with only a sulfate activator, the early strength is high at 6.8 MPa / 1 day, but the expansion rate is only 0.15%, making it prone to expansion and cracking. In Comparative Example 7, excessive sulfate activator results in a high expansion rate and a tendency to crack. Similarly, in Comparative Example 8, excessive alkali activator prolongs the setting time (final setting at 9 hours) and causes a decline in strength in the later stages.

[0050] In Examples 1-3, the lightness is equivalent to pure cement, and the expansion rate is low.

[0051] Compared with Comparative Example 5, the ball milling time was insufficient, and the strength at 28 days was 30 MPa, which was 33% lower than that of Example 1, indicating insufficient activation. Compared with Comparative Example 6, the strength at 28 days was 28 MPa, and the reaction efficiency was significantly reduced. Ball milling for 30 minutes or more resulted in the optimal strength.

[0052] In summary, the present invention has a solid waste content greater than 80%, and its performance is comparable to that of ordinary cement. It exhibits volume stability (expansion rate ≤0.05%), which is superior to traditional solid waste materials (typically ≥0.1%). Furthermore, the heavy metal leaching concentration is more than 50% lower than the national standard limit, making it more environmentally friendly and safer.

[0053] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. An industrial solid waste cementitious material for roads, characterized by, The composite cement includes the following components by weight: 50-70 parts of slag powder; 20-30 parts of fly ash; 1-20 parts of steel slag; 3-10 parts of desulfurization gypsum; 5-30 parts of composite activator; and 0-10 parts of functional additive. The composite activator includes an alkali activator and a sulfate activator, and the molar ratio of the alkali activator to the sulfate activator is (0.5-2) :

1.

2. The industrial solid waste cementitious material for road use according to claim 1, characterized by, The alkali activator is NaOH or water glass or a mixture of the two. The sulfate activator is gypsum or Na2SO4 or a mixture of the two.

3. The industrial solid waste cementitious material for road use according to claim 2, characterized by, The functional additive is 1-3 parts of nano-SiO2, wherein the particle size of the nano-SiO2 is 10-50 nm, and the specific surface area is ≥500 m² / g. The functional additive is 5-10 parts of aluminate cement.

4. The industrial solid waste cementitious material for road use according to claim 2, characterized by, The functional additive is 5-10 parts of a chemical setting accelerator, wherein the chemical setting accelerator is at least one of CaCl2 and Na2CO3. The method includes the following steps:

5. The industrial solid waste cementitious material for road use according to claim 1, characterized by, S1, raw material pretreatment, the slag powder, fly ash, steel slag and desulfurization gypsum are respectively superfine ground to a specific surface area of ≥500 m² / kg; The steel slag is subjected to leakage stacking treatment to avoid later expansion, wherein the leakage stacking time of the steel slag is 12-15 days; 6. The industrial solid waste cementitious material for road use according to claim 1, characterized by, S2, activation treatment, the pretreated raw materials are mixed according to the required weight parts, then the composite activator is added and subjected to mechanical activation treatment; S3, durability regulation treatment, the functional additive is added to the material of S2 and mixed uniformly.

7. The industrial solid waste cementitious material for road use according to claim 1, characterized by, The mechanical activation treatment is specifically ball milling treatment, and the ball milling treatment time is at least 30 min. After mixing uniformly in S3, steam curing treatment is performed, and specifically, curing is performed at 60-80℃ for 4-8 h.

8. A method for producing an industrial solid waste cementitious material for roads according to any one of claims 1 to 7, characterized by, ​ ​ ​ ​ ​ 9. The method for producing an industrial solid waste cementitious material for roads according to claim 8, characterized by, ​ 10. The method for producing an industrial solid waste cementitious material for roads according to claim 8, characterized by, ​

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