1. An admixture characterized by: the composite material comprises the following raw materials in parts by weight: 10-20 parts of hydration inhibition slow-release type water-absorbing resin, 30-50 parts of magnesium oxide, 5-10 parts of calcium oxide, 5-10 parts of sodium hydroxide, 10-20 parts of sodium sulfate, 0.1-0.6 part of retarder, 0-5 parts of sodium bromide, 0-10 parts of nano calcium silicate and 0-10 parts of nano silicon dioxide.

2. An admixture according to claim 1 wherein: the hydration inhibition slow release type water-absorbing resin is prepared by mixing and stirring 40-60% of corn starch dextrin and 40-60% of porous acrylic acid water-absorbing resin in a molten state, and selecting a part with the diameter of less than 75 micrometers through spray cooling.

3. An admixture according to claim 1 wherein: the magnesium oxide is coarse-particle magnesium oxide, the firing temperature is 700-800 ℃, and particles of 50-200 meshes are taken after grinding.

4. An admixture according to claim 1 wherein: the retarder is any one or more of sodium gluconate, sodium citrate and boric acid.

5. Use of an admixture according to any one of claims 1 to 4 wherein: the additive is used for replacing cement in a cement stabilizing crushed stone layer with the cement replacing rate of 50-80%.

6. Use of an admixture according to claim 5, wherein: the dosage of the additive is 2 to 5 percent of the weight of the additive in the cement stabilized gravel layer.

7. Use of an admixture according to claim 5, wherein: hydration inhibition slow-release type water absorption resin, magnesium oxide, calcium oxide, sodium hydroxide, sodium sulfate, retarder and sodium bromide in the admixture form a solid component, and nano calcium silicate and nano silicon dioxide form a liquid component; when the admixture is added, the solid component and the admixture are mixed to form a solid mixture, and then the solid mixture is mixed with the liquid component.

8. A water stable base layer to which the admixture of any one of claims 1 to 4 is applied, characterized in that: the composition comprises the following raw materials in parts by weight: 100 parts of aggregate, 2.5-4 parts of admixture, 0.05-0.2 part of admixture, 1-2.5 parts of cement and 5-6.5 parts of water.

9. The stabilized water base layer with the additive as claimed in claim 8, wherein: the dosage of the additive is 2 to 5 percent of the dosage of the admixture.

10. A method for preparing a water-stable base layer using the admixture according to any one of claims 1 to 4, wherein: the method comprises the following steps:

s1, uniformly mixing the solid raw materials in the admixture with the admixture to obtain a solid mixture; uniformly mixing the liquid raw materials in the admixture with part of water to obtain a liquid mixture;

s2, mixing the solid mixture and the liquid mixture and uniformly stirring to obtain an additional admixture;

and S3, mixing the admixture, the cement and the rest water, adding the aggregate after uniformly stirring, and uniformly stirring to obtain the cement.

Background

The cement stabilized macadam layer is a cement stabilized macadam layer for short, namely cement is adopted to solidify graded macadam, and compaction and maintenance are carried out. The technical Specification for the construction of road base courses (JT J034-2000) specifies the delay between the addition of water to cement stabilization aggregates and the completion of compaction: concentrated plant mixing is adopted for no more than 2 hours, and road mixing is adopted for no more than 3-4 hours. This is difficult to achieve for some units where construction equipment and organizational management conditions are not ideal. Particularly, when the strength grade of cement is improved, the implementation of the cement ISO standard has the problems of fine fineness, reduced mixing amount of mixed materials, higher hydration speed, insufficient strength tolerance coefficient of water-stabilizing materials, low compaction degree, poor core sample integrity, poor scouring resistance and the like caused by delayed rolling. In addition, with the higher and higher requirements of the country on environmental protection, the price of cement is also increased in a saving way, so that the cost of the cement stabilized macadam is increased by about 5-10 yuan.

In the existing roller compacted concrete technology, a method for replacing cement with fly ash or other admixture with pozzolanic activity is adopted, the cement consumption is reduced, the cement hydration can be slowed down to a certain extent, and the advantages of high compactness, high later strength, high durability and low cost of a water stabilizing material are realized by utilizing the characteristics that the admixture such as fly ash has lower density than the cement, the pozzolanic effect and the economy is low, so that the win-win of the technology and the economy is achieved. However, the application effect of admixtures such as fly ash in cement stabilized macadam can not achieve the expectation, which is mainly shown in the following: the requirement of 7d strength of the cement stabilized macadam limits the mixing amount of the fly ash, and because the early activity of the fly ash is low, the fly ash can only be used as a filler with low mixing amount in a cement stabilized macadam layer, the volcanic ash effect is not exerted, and the economic benefit is limited.

At present, various chemical reagents are added to stimulate the early activity of the fly ash, but the stimulating effect is not ideal, the maximum mixing amount of the fly ash can only reach 30-50%, the cement dosage needs to be increased simultaneously under the mixing amount, and the economic benefit generated by replacing cement with admixtures such as the fly ash is weakened. Therefore, the admixture such as fly ash is used for replacing cement in the conventional cement stabilized macadam, and the problems of low fly ash mixing amount, poor early strength, short construction time from stirring production to rolling completion, maintenance requirement in pozzolanic effect generation and later active reaction after moisture retention and maintenance for 7 days, large shrinkage deformation and easy cracking of the cement stabilized macadam and the like still exist.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides an additive, a cement stabilized base layer applying the additive and a preparation method thereof.

The invention aims to provide an additive, which comprises the following raw materials in parts by weight: 10-20 parts of hydration inhibition slow-release type water-absorbing resin, 30-50 parts of magnesium oxide, 5-10 parts of calcium oxide, 5-10 parts of sodium hydroxide, 10-20 parts of sodium sulfate, 0.1-0.6 part of retarder, 0-5 parts of sodium bromide, 0-10 parts of nano calcium silicate and 0-10 parts of nano silicon dioxide.

The invention can inhibit C in cement particles by adopting hydration inhibition slow-release type water-absorbing resin to be matched with the retarder₃Hydration rate of A, inhibition of C in cement particles₃And the hydration rate of S in the age of 1-2 d effectively regulates and controls the cement hydration acceleration period process under the action of nano calcium silicate and nano silicon dioxide, and the promotion effect of the nano calcium silicate and nano silicon dioxide on the hydration degree of 3-7 d is not influenced while the early hydration rate is delayed.

Meanwhile, the admixture is applied to a water-stable low-gel material gel system of low-volume cement and large-volume admixture, and the retarder is continuously dissolved and adsorbed in an alkaline solution environment to cement, nano calcium silicate and nano dioxideThe silicon plays a role in dispersing, the nano calcium silicate and the nano silicon dioxide consume calcium hydroxide in the alkaline solution, the formation of hydration products is accelerated to provide 3-7 d early strength, and the defect that the early hydration degree of a glue material system with a large amount of admixture and low cement is insufficient is overcome. And alkalis and salt components in the alkaline solution act together to excite the potential activity of the admixture: from OH in solution^-The method comprises the steps of breaking partial Si-O bonds and Al-O bonds in an original glassy network with higher polymerization degree to form unsaturated active bonds, promoting network depolymerization and dissolution and diffusion of silicon and aluminum to form hydration products, and accelerating the generation of the hydration products by salts to promote the development of the admixture on the early and later performances of a gel system.

Furthermore, the hydration inhibition slow release type water-absorbing resin is obtained by mixing and stirring 40-60% of corn starch dextrin and 40-60% of porous acrylic acid water-absorbing resin in a molten state, and selecting a part with the diameter of less than 75 micrometers through spray cooling.

The hydration inhibition slow-release water-absorbing resin disclosed by the invention is combined with water to generate natural expansion, and the binding effect of starch dextrin in the hydration inhibition slow-release water-absorbing resin on water molecules in a gel state is further improved, so that the water in the gel is difficult to lose, the water storage stability of the hydration inhibition slow-release water-absorbing resin in an alkaline solution is enhanced, a micro water storage reservoir is formed in the hydration inhibition slow-release water-absorbing resin, and then the hydration inhibition slow-release water-absorbing resin is slowly evaporated and released under the action of ambient temperature and air. Therefore, on one hand, the inside moisture curing of the cement paste can be ensured, the drying shrinkage of the cement paste is inhibited, and on the other hand, water required by the hydration of the magnesium oxide and the admixture can be provided under the dry condition to accelerate the generation of hydration products. The magnesium oxide can make the gel system generate micro-expansion in the later hydration process, and the hydration product magnesium hydroxide can effectively fill gaps and micro-cracks, so that the later volume stability of the system is good, the temperature shrinkage deformation is effectively compensated, and the occurrence of temperature shrinkage cracks is favorably prevented.

Furthermore, the magnesium oxide is coarse-particle magnesium oxide, the firing temperature is 700-800 ℃, and particles of 50-200 meshes are taken after grinding.

Further, the retarder is any one or more of sodium gluconate, sodium citrate and boric acid.

The second purpose of the invention is to provide the application of the admixture for cement stabilized macadam layer with admixture replacing cement rate of 50-80%. By applying the cement stabilizing gravel layer with high-doping-amount admixture replacing cement, the cement replacing cement by a large amount of admixture is beneficial to reducing the early hydration rate of a gel system, and the retarder, the hydration inhibition slow-release water-absorbent resin and the like are matched to inhibit C in cement particles₃And the hydration rate of S in the age of 1-2 days.

Furthermore, the dosage of the admixture is 2 to 5 percent of the weight of the admixture in the cement stabilized gravel layer.

Furthermore, hydration inhibition slow-release type water absorption resin, magnesium oxide, calcium oxide, sodium hydroxide, sodium sulfate, a retarder and sodium bromide in the admixture form a solid component, and nano calcium silicate and nano silicon dioxide form a liquid component; when the admixture is added, the solid component and the admixture are mixed to form a solid mixture, and then the solid mixture is mixed with the liquid component.

The invention also provides a cement stabilized base layer applying the admixture, which comprises the following raw materials in parts by weight: 100 parts of aggregate, 2.5-4 parts of admixture, 0.05-0.2 part of admixture, 1-2.5 parts of cement and 5-6.5 parts of water.

Furthermore, the dosage of the admixture is 2 to 5 percent of the dosage of the admixture.

The fourth purpose of the invention is to provide a preparation method of a water stable base layer applying the admixture, which comprises the following steps:

s1, uniformly mixing the solid raw materials in the admixture with the admixture to obtain a solid mixture; and uniformly mixing the liquid raw materials in the admixture with part of water to obtain a liquid mixture.

And S2, mixing the solid mixture and the liquid mixture and uniformly stirring to obtain the additional admixture.

And S3, mixing the admixture, the cement and the rest water, adding the aggregate after uniformly stirring, and uniformly stirring to obtain the cement.

The invention has the beneficial effects that:

1) the admixture can excite the early activity of the admixture, ensure that the strength of 7d meets the requirement, and properly prolong the construction time from stirring production to rolling completion, wherein the gel system of the admixture is basically not hydrated or is slightly hydrated in the construction time. Meanwhile, moisture can be provided for the volcanic ash effect and the later-period activity reaction in the later period of the cement stabilized macadam, so that the gel system of the high-doping-amount admixture added with the admixture has the later-period self-curing function. In addition, the additive can improve the volume stability of the cement-stabilized macadam and reduce the shrinkage deformation and cracking of the cement-stabilized macadam.

2) The additive is mainly applied to the cement stabilized gravel layer with the cement replacing rate of 50-80% of that of the admixture, meets the 7d strength requirement, improves the cement replacing rate of the admixture, is beneficial to reducing the manufacturing cost of the cement stabilized gravel layer and improves the economic benefit of the cement stabilized gravel layer.

3) The rolling and forming time of the cement stabilized base layer adopting the additive can be widened to 4 hours, the 7d unconfined compressive strength of the cement stabilized macadam exceeds 10% of pure cement stabilized macadam, the compaction degree is improved by more than 1%, the core sample integrity rate is improved by more than 1%, the single cost is reduced by 5-10 yuan, and the cement stabilized macadam has the advantages of long age, high splitting strength, high bending and pulling strength, high scour resistance, low shrinkage deformation and the like, is favorable for prolonging the service life of roads, and simultaneously realizes solid waste utilization, low cost, environmental protection and economy.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.

The invention provides an additive: the composite material comprises the following raw materials in parts by weight: 10-20 parts of hydration inhibition slow-release type water-absorbing resin, 30-50 parts of magnesium oxide, 5-10 parts of calcium oxide, 5-10 parts of sodium hydroxide, 10-20 parts of sodium sulfate, 0.1-0.6 part of retarder, 0-5 parts of sodium bromide, 0-10 parts of nano calcium silicate and 0-10 parts of nano silicon dioxide. Wherein, the hydration inhibition slow release type water-absorbing resin is prepared by mixing and stirring 40-60% of corn starch dextrin and 40-60% of porous acrylic acid water-absorbing resin in a molten state according to the mass percentage, stirring for 15min at a stirring speed of 40-80 r/min, and then rapidly cooling by spraying to select a part with the diameter of less than 75 microns.

The magnesium oxide and the calcium oxide in the formula are coarse-grained products, the firing temperature of the magnesium oxide is 700-800 ℃, and the magnesium oxide is ground in a ball milling mode to obtain 50-200-mesh particles. The magnesium oxide particles obtained in the way are in a polygonal sphere-like shape, and the swelling reaction time is mainly concentrated in 3-180 days. The granularity of the coarse-grained calcium oxide is between 100 and 300 meshes, and the main hydration reaction time is between 6 and 24 hours. The retarder adopted by the invention is one or more of sodium gluconate, sodium citrate and boric acid, and the mixing amount of the retarder is 1-3% of cement tricalcium aluminate or tetracalcium aluminoferrite in the water-stable base layer formula. Meanwhile, the sodium hydroxide, the sodium bromide and the sodium sulfate are all solid flaky or coarse granular industrial products, the content is not lower than 98%, and the time required for complete dissolution exceeds 4 hours. The nano calcium silicate and the nano silicon dioxide in the formula are liquid or sol, the solid contents of the nano calcium silicate and the nano silicon dioxide are both in the range of 20-40%, and the hydration reaction time of the nano calcium silicate is 6 h-7 d.

The invention also provides the application of the admixture, which is used for replacing cement in a cement stabilized macadam layer with the cement replacing rate of 50-80%. The dosage of the additive is 2 to 5 percent of the weight of the additive in the cement stabilized gravel layer. The using method comprises the following steps: the solid component is first mixed with the admixture to form a solid mixture, and the solid mixture is then mixed with the liquid component.

The invention also provides a cement stabilized base layer applying the admixture, which comprises the following raw materials in parts by weight: 100 parts of aggregate, 2.5-4 parts of admixture, 0.05-0.2 part of admixture, 1-2.5 parts of cement and 5-6.5 parts of water. Wherein the dosage of the additive is kept to be 2-5% of the dosage of the admixture. The aggregate in the formula is designed according to a compact structure of aggregate, and the aggregate proportion of each particle size is as follows: 19.0-31.5 mm: 9.5-19.0 mm: 4.75-9.5 mm: 0.075-4.75 mm: 0-0.075 mm is 14-32%: 28% -48%: 16% -36%: 22% -32%: 0 to 3 percent.

The admixture in the formula is an admixture with volcanic ash activity, and comprises one or more of fly ash, mineral powder, phosphorous slag powder and the like. Wherein when the admixture adopts fly ash, the fly ash can be I-grade fly ash, II-grade fly ash, III-grade fly ash, lower-quality bottom ash, wet ash or fly ash placed for many years, and SiO thereof₂The content is not less than 20 percent, and the density is 1900-2800 kg/m³(ii) a The activity index of 7d is more than 50 percent, the activity index of 28d is more than 50 percent, and the activity index of 90d is more than 60 percent. When the admixture adopts mineral powder, the mineral powder can be a product obtained by processing residues after refining iron slag, vanadium-titanium slag, manganese slag, lithium slag, zirconium slag and other metals. SiO 2₂The content is not less than 40 percent, and the specific surface area is 200-1000 m²The particle shape is mainly polygonal cube or spheroid; the activity index of 7d is more than 50 percent, the activity index of 28d is more than 60 percent, and the activity index of 90d is more than 70 percent. The phosphorus slag powder used as additive is extracted from yellow phosphorus, the molten phosphorus slag is extracted and cooled in saturated lime water, and then is ground and air-separated to obtain P₂O₅The content is 0.5-1.5%, the content of active components is not less than 60%, and the specific surface area is 250-600 m²Per kg, density 2600-3000 kg/m³(ii) a The activity index of 7d is more than 50 percent, the activity index of 28d is more than 50 percent, and the activity index of 90d is more than 60 percent.

The invention finally provides a preparation method of the water-stable base layer applying the admixture, which comprises the following steps:

s1, uniformly mixing the solid raw materials in the admixture with the admixture to obtain a solid mixture; and uniformly mixing the liquid raw materials in the admixture with part of water to obtain a liquid mixture.

And S2, mixing the solid mixture and the liquid mixture and uniformly stirring to obtain the additional admixture.

And S3, mixing the admixture, the cement and the rest water, adding the aggregate after uniformly stirring, and uniformly stirring to obtain the cement.

Example one

The embodiment provides an admixture, 60g of hydration inhibition slow release type water-absorbent resin, 180g of magnesium oxide, 30g of calcium oxide, 30g of sodium hydroxide, 60g of sodium sulfate and 0.6g of retarder are weighed respectively, the hydration inhibition slow release type water-absorbent resin adopted in the embodiment is obtained by mixing and stirring 40% of corn starch dextrin and 60% of porous acrylic acid water-absorbent resin in a molten state, and after spray cooling, a part with the diameter of less than 75 micrometers is selected. In the embodiment, the magnesium oxide and the calcium oxide both adopt coarse-grained products, and the retarder adopts sodium gluconate. The components in the formula are uniformly mixed to obtain an additive product.

Example two

This example provides an admixture, which is prepared by weighing 100g of hydration inhibition slow release type water absorbent resin, 250g of magnesium oxide, 50g of calcium oxide, 50g of sodium hydroxide, 100g of sodium sulfate, 3g of retarder, 25g of sodium bromide, 50g of nano calcium silicate and 50g of nano silicon dioxide. The hydration inhibition slow-release type water-absorbent resin adopted in the embodiment is obtained by mixing and stirring 60% of corn starch dextrin and 40% of porous acrylic acid water-absorbent resin in a molten state, and selecting a part with the diameter of less than 75 micrometers after spray cooling. In the embodiment, the magnesium oxide and the calcium oxide both adopt coarse grain products, and the retarder adopts sodium citrate. The hydration inhibition slow-release type water absorption resin, magnesium oxide, calcium oxide, sodium hydroxide, sodium sulfate and a retarder in the formula are uniformly mixed to form a solid component, and then the nano calcium silicate and the nano silicon dioxide are mixed to form a liquid component.

EXAMPLE III

The embodiment provides an admixture, wherein 75g of hydration inhibition slow release type water absorbent resin, 200g of magnesium oxide, 40g of calcium oxide, 40g of sodium hydroxide, 75g of sodium sulfate, 2g of retarder, 15g of sodium bromide, 25g of nano calcium silicate and 25g of nano silicon dioxide are weighed respectively, the hydration inhibition slow release type water absorbent resin adopted in the embodiment is obtained by mixing and stirring 40% of corn starch dextrin and 60% of porous acrylic acid water absorbent resin in a molten state, and selecting a part with the diameter of less than 75 micrometers after spraying and cooling. The magnesium oxide and the calcium oxide of the embodiment both adopt coarse-grained products, and the retarder adopts sodium gluconate and boric acid according to the weight ratio of 1: 1, a compounded product. The hydration inhibition slow-release type water absorption resin, magnesium oxide, calcium oxide, sodium hydroxide, sodium sulfate and a retarder in the formula are uniformly mixed to form a solid component, and then the nano calcium silicate and the nano silicon dioxide are mixed to form a liquid component.

Example four

This example provides a water-stable foundation layer, which is prepared by weighing 50kg of aggregate, 1.25kg of fly ash, 25g of admixture, 1.25kg of cement and 2.75kg of water, and then:

s1, uniformly mixing the solid components in the admixture with the admixture to obtain a solid mixture; and uniformly mixing the liquid components in the admixture with part of water to obtain a liquid mixture.

And S2, mixing the solid mixture and the liquid mixture and uniformly stirring to obtain the additional admixture.

And S3, mixing the admixture, the cement and the rest water, adding the aggregate after uniformly stirring, and uniformly stirring to obtain the cement.

In this example, the additive used is the additive prepared in example three, and the fly ash is dry fly ash of a power plant, low-activity and equal-external ash, and the specific properties thereof are shown in table 1.

TABLE 1 fly ash Performance test results

EXAMPLE five

The present embodiment is different from the fourth embodiment in that: the formula of the water-stable base layer in the embodiment is as follows: 50kg of aggregate, 2kg of mineral powder, 100g of admixture, 0.5kg of cement and 3.15kg of water. The performance test results of the ore powder used in this example are shown in table 2.

Table 2 mineral powder property test results

EXAMPLE six

The present embodiment is different from the fourth embodiment in that: the formula of the water-stable base layer in the embodiment is as follows: 50kg of aggregate, 1.5kg of phosphorous slag powder, 60g of admixture, 1kg of cement and 3kg of water. The performance test results of the phosphorous slag powder of this example are shown in Table 3.

TABLE 3 phosphorus slag powder Performance test results

Comparative example 1

The comparative example differs from the fourth example mainly in that: the formula of the water-stable base layer of the comparative example is as follows: 50kg of aggregate, 2.5kg of cement and 3kg of water; no additive is added.

The unconfined compressive strength, tensile strength at split and modulus of resilience at split, flexural tensile strength, drying shrinkage and scour resistance of the stabilized water base layers prepared in the fourth to sixth examples and the first comparative example were tested, and the test results are shown in tables 4 to 8.

TABLE 4 unconfined compressive strength test results

TABLE 5 tensile strength at cleavage and modulus of resilience at cleavage

TABLE 6 flexural tensile Strength test results

TABLE 7 Dry shrinkage test results

TABLE 8 results of the antiscour test

Scheme(s)	90d scouring amount (g)	90d scouring mass loss (%)	Compared with the reference
				Comparative example 1	9.6	0.15	100％
Example 1	6.4	0.10	67％
				Example 2	7.1	0.11	73％
Example 3	6.2	0.10	67％

As can be seen from tables 4-8, the cement stabilized macadam prepared according to the examples of the present invention has better performance than the cement stabilized macadam of comparative example I, and is significantly better than the pure cement stabilized macadam in terms of unconfined compressive strength, fracture tensile strength, fracture modulus of resilience, flexural tensile strength, shrinkage and scour resistance. Therefore, the invention realizes the preparation of the cement-high-admixture stabilized macadam with low price and excellent performance by the matching of the admixture and the admixture.

The foregoing is illustrative of the preferred embodiments of this invention, and it is to be understood that the invention is not limited to the precise form disclosed herein and that various other combinations, modifications, and environments may be resorted to, falling within the scope of the concept as disclosed herein, either as described above or as apparent to those skilled in the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.