Background
China has become the world with the longest highway mileage, but the highway network needs to be continuously improved, and the task of highway construction remains difficult. The highway construction engineering quantity is large, a large amount of high-quality natural aggregates are consumed, the natural aggregates are deficient, and excessive mining seriously damages the environment. Therefore, the search for alternative materials of high-quality natural aggregates is an important problem which needs to be solved urgently at present. On the other hand, steel slag produced in China per year exceeds 1 hundred million tons, but the comprehensive utilization rate of the steel slag is only 20 percent, and the rest of a large amount of steel slag is laid everywhere and is mostly treated by landfill or accumulation. Because the steel slag contains heavy metal components, the soil can be polluted by landfill, and irreversible environmental damage is caused. The accumulation not only occupies urban land, but also can generate harmful particles, pollute atmosphere and threaten the health of residents. Therefore, it is very important to realize the resource utilization of the steel slag and improve the utilization rate of the steel slag.
The steel slag has high compressive strength, rough surface, wear resistance, skid resistance and other advantages. Therefore, it can replace natural stone to be applied to road construction. Research has shown that the asphalt concrete prepared by using the fully aged steel slag has excellent high-temperature stability and water stability. Under the condition of the shortage of high-quality aggregates in China at present, the steel slag partially or completely replaces natural aggregates to be applied to the asphalt mixture, so that the steel slag asphalt mixture has huge development potential, is beneficial to sustainable development of the steelmaking industry, is also beneficial to avoiding excessive exploitation of high-quality stones, and protects the natural environment.
However, unaged steel slag contains significant amounts of free calcium oxide (f-CaO) and magnesium oxide, which react with water to form hydroxides, which produce significant volume expansion. If the steel slag is directly applied to road engineering, the asphalt mixture can expand, and the pavement can crack. Natural aging often takes a lot of time, far slower than the production speed of steel slag. Therefore, in order to realize the large-scale application of the steel slag on the asphalt pavement, a more efficient method for solving the problem of volume expansion of the steel slag must be found.
According to different stages of steel slag modification treatment, the steel slag volume stabilization treatment can be divided into pretreatment and post-treatment. The pretreatment is mainly carried out on the molten steel slag under the high-temperature condition by utilizing the high SiO content2、Al2O3The modifier (such as river sand, fly ash, coal gangue and other materials) modifies the thermal state steel slag and eliminates free active ingredients in the steel slag through chemical reaction. The modification method changes the chemical composition of the steel slag in the steel slag production process, and fundamentally reduces the content of active ingredients in the steel slag.
The post-treatment mainly aims at cooling solid steel slag and can be divided into three types according to the difference of the modification principle of the steel slag. Firstly, the steel slag is promoted to be hydrated as much as possible. Expansion of steel slagThe expansion potential is released before use, so that the later-stage volume expansion of the steel slag is relieved, and the main modification modes comprise aging treatment, steam pressure treatment and steam treatment; the most common method is used in aging treatment, but the time is long, and the large-scale utilization of the steel slag is not utilized; the autoclaved treatment and the steam treatment can lead the steel slag to reach stable volume in a short time, but the treatment process is complex, the cost is higher, and the popularization and the utilization of the steel slag are not facilitated. Secondly, carbonating the steel slag. Under high temperature and high pressure, CO is utilized2Pretreating the steel slag to form a layer of compact CaCO on the surface of the steel slag3Like the above-mentioned treatment methods, the treatment process is complicated and the cost is high. And thirdly, the steel slag is wrapped by inorganic materials (lime, cement, silica fume and the like) and organic materials such as organic silicon resin and the like, so that the contact between the steel slag and water is blocked, the hydration volume expansion of active substances cannot be carried out, but the modification treatment of cement paste is inconvenient, and the water absorption of the modified steel slag is not well improved. Organic silicon resin belongs to thermosetting plastics, has high brittleness, can be completely cured at high temperature, has high viscosity at normal temperature, and is often used after being diluted by being matched with organic solvents, and the solvents have toxicity, can pollute the environment and harm the health of operators
Disclosure of Invention
The technical problem is as follows: aiming at the problems of the existing steel slag modification technology, the invention provides the water-resisting steel slag aggregate with strong adhesion with asphalt and the preparation method thereof, the method modifies the steel slag, and the obtained modified water-resisting steel slag aggregate has low water absorption, high compressive strength, wear resistance and strong adhesion with the asphalt and meets the use requirements of road specifications; the preparation method is operated at normal temperature and normal pressure, the treated steel slag does not need to be aged for a long time, the requirements on equipment and sites are low, the preparation process is simple, the materials are environment-friendly, and the production efficiency is high; the steel slag asphalt mixture produced by using the water-resisting steel slag aggregate has good water stability.
The technical scheme is as follows: the invention provides a water-proof steel slag aggregate with strong adhesion with asphalt, which is common converter steel slag with a composite water-proof material covered on the surface, and the composite water-proof material comprises the following components in parts by weight:
wherein:
the grain size distribution range of the water-resisting steel slag aggregate is 31.5 mm-4.75 mm, wherein the content of free calcium oxide f-CaO is less than 5 wt%.
The solid content of the silicon rubber emulsion is 50-65%.
The siliceous material used by the alkaline silica sol is silicon dioxide, and the solid content of the siliceous material is 25 to 27 percent.
The binder is one of cationic SBS emulsified asphalt or anionic SBS emulsified asphalt.
The dispersing agent is dimethyl silicone oil, the film-forming assistant is ethyl acetate, the catalyst is dibutyltin dilaurate, and the dispersing medium is distilled water.
The cross-linking agent comprises the following components in parts by weight: 1-3 parts of ethyl orthosilicate, 5-10 parts of a silane coupling agent and 20-30 parts of an alcohol aqueous solution; wherein the alcohol aqueous solution is ethanol aqueous solution or propanol aqueous solution, and the weight ratio of absolute ethanol to distilled water in the ethanol aqueous solution is 19: 1-9: 1, the weight ratio of the propanol to the distilled water in the propanol aqueous solution is 19: 1-9: 1.
the water absorption rate of the water-proof steel slag aggregate is less than 1.7 percent.
The invention also provides a preparation method of the water-resisting steel slag aggregate with strong adhesion with asphalt, which comprises the following steps:
1) adding the silicone rubber emulsion, the alkaline silica sol, the binder, the dispersant, the film-forming assistant and the catalyst into a dispersion medium according to a proportion, and stirring at a rotating speed of 400-600 rpm for 15-25 min to obtain a mixed solution;
2) adding ethyl orthosilicate and a silane coupling agent into an alcohol aqueous solution according to a ratio, and stirring at a rotating speed of 200-300 rpm for 5-15 min to obtain a cross-linking agent;
3) adding the cross-linking agent into the mixed solution in proportion, and stirring at the rotating speed of 150-300 rpm for 5-10 min to obtain the composite waterproof material;
4) spraying the composite water-proof material obtained in the step 3) on the surface of the steel slag, enabling the composite water-proof material to be uniformly wrapped on the surface of the steel slag aggregate, and curing for 2-5 hours at room temperature to obtain the water-proof steel slag aggregate.
Wherein:
the steel slag aggregate is pretreated by washing and drying before modification;
and 4) spraying the obtained composite water-proof material on the surface of the steel slag, wherein the composite water-proof material accounts for 1-5% of the mass of the steel slag.
The silicon-oxygen group in the composite waterproof material prepared by the invention can react with the active group on the surface of the steel slag through chemical bonding and is solidified to form a high-strength waterproof film; secondly, strong interface acid-base action can be formed between the water-resisting steel slag aggregate with alkaline surface and the acid asphalt, so that the adhesion between the asphalt and the steel slag is enhanced; finally, after the surface of the modified steel slag is modified by the water-based material, the rough texture is still kept, the contact area of the asphalt and the surface of the steel slag is increased, and the waterproof film and the asphalt film are firmly adhered to the surface of the steel slag through the mechanical chelation between the asphalt and the surface of the steel slag; a double-layer hydrophobic effect layer consisting of a water-resisting layer and an asphalt layer is formed on the surface of the steel slag, so that the hydration volume expansion of the steel slag is inhibited, and the durability of the film layer is enhanced.
Has the advantages that: compared with the prior art, the invention has the following advantages:
(1) the composite waterproof material covers the surface of the waterproof steel slag aggregate, so that the contact between active ingredients in the steel slag and water is effectively isolated, the expansion inhibition effect is good, and the content of free calcium oxide in the steel slag can be relaxed;
(2) the waterproof steel slag aggregate provided by the invention has strong adhesion with asphalt, the durability of a waterproof layer is good, the waterproof layer is not easy to desorb from the surface of steel slag, and the capability of resisting water damage is enhanced;
(3) the preparation process of the water-proof steel slag aggregate provided by the invention is simple, the construction is carried out at normal temperature, the modification time is short, and when the asphalt is mixed, the steel slag aggregate improves the adhesive strength with the asphalt through the acid-base interface action and the mechanical chelation action, so that an asphalt film is firmly adhered to the surface of the steel slag aggregate, thereby being beneficial to inhibiting the volume expansion of the steel slag and enhancing the durability of the water-proof film;
(4) special equipment is not needed, the cost is low, the absorption of the steel slag to the asphalt is reduced, the using amount of the asphalt is reduced, and the cost is saved;
(5) the method is environment-friendly, uses water-based materials, realizes the resource utilization of wastes, and improves the utilization rate of the steel slag;
(6) the asphalt mixture prepared from the water-resisting steel slag aggregate provided by the invention has excellent water stability and meets the standard requirement;
(7) the composite water-proof material covered on the surface of the water-proof steel slag aggregate provided by the invention has low-temperature flexibility, and the low-temperature crack resistance of the asphalt mixture is improved;
(8) the waterproof steel slag aggregate obtained by modifying the steel slag can still keep the surface roughness and the strength.
Detailed Description
The present invention will be further described with reference to the following examples.
Example 1
A preparation method of a water-resisting steel slag aggregate with strong adhesion with asphalt comprises the following steps:
(1) adding 180 parts of silicone rubber emulsion, 50 parts of alkaline silica sol, 7 parts of binder, 1 part of dispersant, 8 parts of film-forming additive and 2 parts of catalyst into 200 parts of dispersion medium, and stirring for 15 minutes at a stirring speed of 400rpm to obtain a mixed solution;
(2) adding 1 part of tetraethoxysilane and 5 parts of silane coupling agent into 20 parts of ethanol water solution (the weight ratio of absolute ethanol to distilled water is 9: 1), and stirring at the rotating speed of 200rpm for 5min to obtain a crosslinking agent;
(3) adding 25 parts of the cross-linking agent prepared in the step (2) into the mixed solution prepared in the step (1), and stirring at a stirring speed of 150rpm for 5 minutes to obtain a composite waterproof material;
(4) and (3) spraying the composite water-proof material obtained in the step (3) on the surface of the steel slag, wherein the composite water-proof material accounts for 1% of the mass of the steel slag, continuously stirring the steel slag while spraying, uniformly wrapping the composite water-proof material on the surface of the steel slag, and curing for 2 hours at room temperature to obtain the water-proof steel slag aggregate.
Wherein:
the grain size distribution range of the water-resisting steel slag aggregate is 31.5 mm-4.75 mm, wherein the content of free calcium oxide f-CaO is 2.06%.
The solid content of the silicone rubber emulsion is 50%.
The siliceous material used by the alkaline silica sol is silicon dioxide, and the solid content of the siliceous material is 25 to 27 percent.
The binder is anionic SBS emulsified asphalt.
The dispersing agent is dimethyl silicone oil, the film-forming assistant is ethyl acetate, the catalyst is dibutyltin dilaurate, and the dispersing medium is distilled water.
The composite waterproof material is covered on the surface of the waterproof steel slag aggregate obtained by the preparation method, and comprises the following components in parts by weight:
the water absorption rate of the water-resisting steel slag aggregate is 1.78%.
Example 2
A preparation method of a water-resisting steel slag aggregate with strong adhesion with asphalt comprises the following steps:
(1) adding 190 parts of silicone rubber emulsion, 55 parts of alkaline silica sol, 8 parts of binder, 1 part of dispersant, 10 parts of film-forming assistant and 2 parts of catalyst into 230 parts of dispersion medium, and stirring at the stirring speed of 450rpm for 18 minutes to obtain a mixed solution;
(2) adding 1 part of tetraethoxysilane and 6 parts of silane coupling agent into 23 parts of ethanol water solution (the weight ratio of absolute ethanol to distilled water is 12: 1, and stirring at the rotating speed of 230rpm for 8min to obtain a crosslinking agent;
(3) adding 28 parts of the cross-linking agent prepared in the step (2) into the mixed solution prepared in the step (1), and stirring at a stirring speed of 180rpm for 7 minutes to obtain a composite waterproof material;
(4) and (3) spraying the composite water-proof material obtained in the step (3) on the surface of the steel slag, wherein the composite water-proof material accounts for 2% of the mass of the steel slag, continuously stirring the steel slag while spraying, uniformly wrapping the composite water-proof material on the surface of the steel slag, and curing for 3 hours at room temperature to obtain the water-proof steel slag aggregate.
Wherein:
the grain size distribution range of the water-resisting steel slag aggregate is 31.5 mm-4.75 mm, wherein the content of free calcium oxide f-CaO is 2.78%.
The solid content of the silicone rubber emulsion is 55%.
The siliceous material used by the alkaline silica sol is silicon dioxide, and the solid content of the siliceous material is 25 to 27 percent.
The binder is anionic SBS emulsified asphalt.
The dispersing agent is dimethyl silicone oil, the film-forming assistant is ethyl acetate, the catalyst is dibutyltin dilaurate, and the dispersing medium is distilled water.
The composite waterproof material is covered on the surface of the waterproof steel slag aggregate obtained by the preparation method, and comprises the following components in parts by weight:
the water absorption rate of the water-resisting steel slag aggregate is 1.54 percent.
Example 3
A preparation method of a water-resisting steel slag aggregate with strong adhesion with asphalt comprises the following steps:
(1) adding 200 parts of silicone rubber emulsion, 60 parts of alkaline silica sol, 10 parts of binder, 2 parts of dispersant, 12 parts of film-forming aid and 3 parts of catalyst into 260 parts of dispersion medium, and stirring at a stirring speed of 500rpm for 20 minutes to obtain a mixed solution;
(2) adding 2 parts of ethyl orthosilicate and 8 parts of silane coupling agent into 26 parts of ethanol water solution (the weight ratio of absolute ethanol to distilled water is 15: 1, and stirring at the rotating speed of 250rpm for 10min to obtain a crosslinking agent;
(3) adding 32 parts of the cross-linking agent prepared in the step (2) into the mixed solution prepared in the step (1), and stirring at a stirring speed of 250rpm for 8 minutes to obtain a composite waterproof material;
(4) and (3) spraying the composite water-proof material obtained in the step (3) on the surface of the steel slag, wherein the modified material accounts for 3% of the mass of the steel slag, continuously stirring the steel slag while spraying, uniformly wrapping the modified material on the surface of the steel slag, and curing for 4 hours at room temperature to obtain the water-proof steel slag aggregate.
Wherein:
the grain size distribution range of the water-resisting steel slag aggregate is 31.5 mm-4.75 mm, wherein the content of free calcium oxide f-CaO is 3.97%.
The solid content of the silicone rubber emulsion is 60%.
The siliceous material used by the alkaline silica sol is silicon dioxide, and the solid content of the siliceous material is 25 to 27 percent.
The binder is anionic SBS emulsified asphalt.
The dispersing agent is dimethyl silicone oil, the film-forming assistant is ethyl acetate, the catalyst is dibutyltin dilaurate, and the dispersing medium is distilled water.
The composite waterproof material is covered on the surface of the waterproof steel slag aggregate obtained by the preparation method, and comprises the following components in parts by weight:
the water absorption rate of the water-resisting steel slag aggregate is 1.36 percent.
Example 4
A preparation method of a water-resisting steel slag aggregate with strong adhesion with asphalt comprises the following steps:
(1) adding 210 parts of silicone rubber emulsion, 65 parts of alkaline silica sol, 12 parts of binder, 3 parts of dispersant, 14 parts of film-forming aid and 4 parts of catalyst into 290 parts of dispersion medium, and stirring at the stirring speed of 550rpm for 23 minutes to obtain a mixed solution;
(2) adding 3 parts of tetraethoxysilane and 10 parts of silane coupling agent into 29 parts of ethanol water solution (the weight ratio of absolute ethanol to distilled water is 18: 1, and stirring at the rotating speed of 280rpm for 13min to obtain a crosslinking agent;
(3) adding 36 parts of the cross-linking agent prepared in the step (2) into the mixed solution prepared in the step (1), and stirring at a stirring speed of 280rpm for 10 minutes to obtain a composite waterproof material;
(4) and (3) spraying the composite water-proof material obtained in the step (3) on the surface of the steel slag, wherein the modified material accounts for 4% of the mass of the steel slag, continuously stirring the steel slag while spraying, uniformly wrapping the modified material on the surface of the steel slag, and curing for 5 hours at room temperature to obtain the water-proof steel slag aggregate.
Wherein:
the grain size distribution range of the water-resisting steel slag aggregate is 31.5 mm-4.75 mm, wherein the content of free calcium oxide f-CaO is 4.81%.
The solid content of the silicone rubber emulsion is 65%.
The siliceous material used by the alkaline silica sol is silicon dioxide, and the solid content of the siliceous material is 25 to 27 percent.
The binder is anionic SBS emulsified asphalt.
The dispersing agent is dimethyl silicone oil, the film-forming assistant is ethyl acetate, the catalyst is dibutyltin dilaurate, and the dispersing medium is distilled water.
The composite waterproof material is covered on the surface of the waterproof steel slag aggregate obtained by the preparation method, and comprises the following components in parts by weight:
the water absorption rate of the water-resisting steel slag aggregate is 1.18 percent.
Example 5
A preparation method of a water-resisting steel slag aggregate with strong adhesion with asphalt comprises the following steps:
(1) adding 220 parts of silicone rubber emulsion, 70 parts of alkaline silica sol, 12 parts of binder, 3 parts of dispersant, 14 parts of film-forming additive and 4 parts of catalyst into 300 parts of dispersion medium, and stirring at a stirring speed of 600rpm for 25 minutes to obtain a mixed solution;
(2) adding 3 parts of ethyl orthosilicate and 10 parts of silane coupling agent into 30 parts of ethanol water solution (the weight ratio of absolute ethanol to distilled water is 19: 1), and stirring at the rotating speed of 300rpm for 15min to obtain a crosslinking agent;
(3) adding 38 parts of the cross-linking agent prepared in the step (2) into the mixed solution prepared in the step (1), and stirring at the stirring speed of 300rpm for 10 minutes to obtain a composite waterproof material;
(4) and (3) spraying the composite water-proof material obtained in the step (3) on the surface of the steel slag, wherein the modified material accounts for 5% of the mass of the steel slag, continuously stirring the steel slag while spraying, uniformly wrapping the modified material on the surface of the steel slag, and curing for 5 hours at room temperature to obtain the water-proof steel slag aggregate.
Wherein:
the grain size distribution range of the water-resisting steel slag aggregate is 31.5 mm-4.75 mm, wherein the content of free calcium oxide f-CaO is 4.98%.
The solid content of the silicone rubber emulsion is 65%.
The siliceous material used by the alkaline silica sol is silicon dioxide, and the solid content of the siliceous material is 25 to 27 percent.
The binder is anionic SBS emulsified asphalt.
The dispersing agent is dimethyl silicone oil, the film-forming assistant is ethyl acetate, the catalyst is dibutyltin dilaurate, and the dispersing medium is distilled water.
The composite waterproof material is covered on the surface of the waterproof steel slag aggregate obtained by the preparation method, and comprises the following components in parts by weight:
the water absorption rate of the water-resisting steel slag aggregate is 1.03%.
For comparison, the water-resistant steel slag aggregates prepared in examples 1 to 5 are compared with ordinary converter steel slag aggregates (the parameters of which are the same as those in example 1) which are not subjected to surface treatment with a modified material and ordinary basalt aggregates, and the performances of the aggregates are shown in table 1, and the test method refers to road engineering asphalt and asphalt mixture test specification (JTG E20-2011).
TABLE 1 basic Properties of the various aggregates
As can be seen from the attached table, after the steel slag is modified, the water absorption is reduced, the mechanical strength is slightly enhanced, and the adhesion with asphalt is better.
In order to further verify the performance of the steel slag asphalt mixture prepared by the water-resisting steel slag aggregate provided by the invention, the following tests are firstly compared:
experiment 1, preparing a steel slag asphalt mixture by using water-proof steel slag aggregate: wherein, the coarse aggregate with the thickness of more than 4.75mm adopts the water-proof steel slag aggregate prepared in the embodiment 1, other aggregates adopt basalt aggregate, mineral powder adopts limestone mineral powder, and asphalt adopts SBS modified asphalt.
Experiment 2, preparing a steel slag asphalt mixture by using water-proof steel slag aggregate: wherein, the coarse aggregate with the thickness of more than 4.75mm adopts the water-proof steel slag aggregate prepared in the embodiment 2, other aggregates adopt basalt aggregate, mineral powder adopts limestone mineral powder, and asphalt adopts SBS modified asphalt.
Experiment 3, preparing a steel slag asphalt mixture by using water-proof steel slag aggregate: wherein, the coarse aggregate with the thickness of more than 4.75mm adopts the water-proof steel slag aggregate prepared in the embodiment 3, other aggregates adopt basalt aggregate, mineral powder adopts limestone mineral powder, and asphalt adopts SBS modified asphalt.
Experiment 4, preparing a steel slag asphalt mixture by using an unmodified common steel slag aggregate: wherein, the coarse aggregate with the thickness of more than 4.75mm adopts unmodified common steel slag, other aggregates adopt basalt aggregate, the mineral powder adopts limestone mineral powder, and the asphalt adopts SBS modified asphalt.
Experiment 5, basalt aggregates are adopted to prepare the asphalt mixture, basalt is adopted for coarse and fine aggregates, limestone mineral powder is adopted for mineral powder, and SBS modified asphalt is adopted for asphalt.
The water stability of various asphalt mixtures prepared in tests 1 to 5 is shown in the attached table 2, and the performance test method refers to the test procedure for road engineering asphalt and asphalt mixtures (JTG E20-2011).
TABLE 2 Water stability Properties of various asphalt mixtures
Item
|
Volume expansion ratio (%)
|
Stability of immersion residue (%)
|
Freeze-thaw split strength ratio (%)
|
Test 1
|
1.51
|
94.7
|
92.55
|
Test 2
|
1.29
|
97.21
|
93.69
|
Test 3
|
1.17
|
91.42
|
96.13
|
Test 4
|
2.06
|
85.11
|
83.79
|
Test 5
|
0.38
|
97.96
|
97.37 |
As can be seen from the attached table, compared with the common steel slag asphalt mixture, the asphalt mixture prepared from the water-resisting steel slag aggregate can greatly improve the water stability (volume stability, water immersion Marshall performance and freeze-thaw cleavage performance) of the steel slag asphalt mixture.