A pervious concrete admixture and pervious concrete pavement comprising the same

Abstract

The application provides a pervious concrete additive, which comprises the following components in the following weight percentage: 5-8 wt% of boric acid, 3-9 wt% of sodium fluorosilicate, 12-15 wt% of magnesium chloride, 2-8 wt% of sodium hexametaphosphate, 2-4 wt% of silicon nitride powder, 4-10 wt% of potassium chloride, 10-12 wt% of calcium chloride, 0.1-0.2 wt% of chelating dispersant, 0.05-0.09 wt% of sodium gluconate, and the balance of water. The pervious concrete and the pervious concrete pavement prepared by using the pervious concrete additive disclosed in the application have excellent mechanical properties, durability and low-temperature pervious properties, and can solve the defects of low strength and poor frost resistance of the pervious concrete.

Description

Technical Field

[0001] This application generally relates to a permeable concrete admixture, and more particularly to a freeze-thaw resistant, high-strength concrete pavement comprising the permeable concrete admixture. Background Technology

[0002] Permeable concrete is a porous concrete structure, generally composed of single-graded aggregates, cementitious materials, water, and admixtures mixed in a certain proportion to form a porous, lightweight concrete with continuous pores. It possesses properties such as water permeability, air permeability, and sound absorption, and is widely used in the construction of sidewalks, non-motorized vehicle lanes, plazas, residential areas, and parking lots. It can effectively solve the problems of urban rainwater flooding and groundwater recharge, and is receiving increasing attention in my country's ecological city and road engineering construction. However, because permeable concrete transfers loads through a framework formed by point contact between aggregates, and is cemented by a cement paste film encapsulating the aggregate surface, its strength is generally in the range of 15–30 MPa, often lower in practical applications, making it difficult to meet the requirements of actual engineering applications. Furthermore, in the cold regions of northern my country, freeze-thaw damage to concrete has always been a major headache. Permeable concrete, with its inherent low strength and large porosity, is subject to freeze-thaw damage far more severely than ordinary concrete in cold regions. When water in the pores of permeable concrete cools and solidifies, it expands in volume, causing localized frost heave and cracking, significantly reducing its mechanical properties and even directly leading to quality loss and structural damage. To address the low strength of permeable concrete, admixtures are typically used to enhance its strength. CN 112094071 A discloses a permeable concrete reinforcing agent composed of a water-reducing agent, micro-powder, alkali-resistant glass fiber powder, hydroxypropyl methylcellulose, and sodium lignosulfonate. It can improve the fluidity and slump of concrete and, to some extent, enhance the compressive and flexural strength of permeable concrete. However, because this reinforcing agent is made from organic raw materials, it is easily affected by time and the environment, resulting in poor durability. Existing technology also discloses a permeable and moisture-retaining concrete admixture made of boric acid, sodium fluorosilicate, magnesium chloride, sodium hexametaphosphate, silicon nitride powder, potassium chloride, etc. The permeable concrete prepared by this admixture has high compressive strength and flexural strength, and while meeting the requirements of high strength, it still has good porosity and permeability coefficient. However, the high porosity is very easy to cause freeze-thaw damage in low-temperature environments, which weakens the freeze-thaw resistance of permeable concrete pavement and needs to be improved. Summary of the Invention

[0003] To address the shortcomings of existing permeable concrete, such as low strength and poor frost resistance, this invention discloses a permeable concrete admixture and a permeable concrete pavement containing the admixture, comprising the following embodiments:

[0004] Implementation Method 1. A permeable concrete admixture, characterized in that it comprises the following components in the following weight fraction ratio: 5-8 wt% boric acid, 3-9 wt% sodium fluorosilicate, 12-15 wt% magnesium chloride, 2-8 wt% sodium hexametaphosphate, 2-4 wt% silicon nitride powder, 4-10 wt% potassium chloride, 10-12 wt% calcium chloride, 0.1-0.2 wt% chelating dispersant, 0.05-0.09 wt% sodium gluconate, and the balance being water.

[0005] Implementation Method 2. The permeable concrete admixture according to Implementation Method 1 is characterized in that the weight fraction of the components is: 6-7 wt% boric acid, 5-7 wt% sodium fluorosilicate, 13-14 wt% magnesium chloride, 4-6 wt% sodium hexametaphosphate, 2.5-3.5 wt% silicon nitride powder, 5-8 wt% potassium chloride, 10.5-11.5 wt% calcium chloride, 0.13-0.17 wt% chelating dispersant, 0.06-0.08 wt% sodium gluconate, and the balance being water.

[0006] Implementation Method 3. The permeable concrete admixture according to Implementation Method 1 is characterized in that the weight fraction of the components is: 6.5 wt% boric acid, 6 wt% sodium fluorosilicate, 13.5 wt% magnesium chloride, 5 wt% sodium hexametaphosphate, 3 wt% silicon nitride powder, 6.5 wt% potassium chloride, 11 wt% calcium chloride, 0.15 wt% chelating dispersant, 0.07 wt% sodium gluconate, and the balance being water.

[0007] Implementation Method 4. The permeable concrete admixture according to Implementation Method 1, characterized in that the chelating dispersant is at least one selected from maleic acid-acrylic acid copolymer, aminotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentamethylenephosphonic acid, diethylenetriaminepentaacetic acid, and sodium ethylenediaminedi-o-phenylacetate.

[0008] Implementation Method 5. The permeable concrete admixture according to Implementation Method 1, characterized in that the boric acid, sodium fluorosilicate, magnesium chloride, sodium hexametaphosphate, silicon nitride powder, potassium chloride and calcium chloride are of analytical grade.

[0009] Embodiment 6. A method for preparing a permeable concrete admixture according to any one of Embodiments 1 to 5, comprising the following steps:

[0010] Step 1: Add boric acid, sodium fluorosilicate, magnesium chloride, sodium hexametaphosphate, silicon nitride powder, calcium chloride, chelating dispersant, and sodium gluconate to appropriate amounts of water to prepare boric acid solution, sodium fluorosilicate solution, magnesium chloride solution, sodium hexametaphosphate solution, silicon nitride powder solution, calcium chloride solution, chelating dispersant solution, and sodium gluconate solution for later use.

[0011] Step 2: Slowly add potassium chloride granules to the stirred boric acid solution until the temperature rises to 80-85℃, then stop feeding and add room temperature water. When the temperature inside the vessel drops to 60-65℃, continue feeding. Repeat this step until the amount of potassium chloride granules added reaches 35-45% of the total amount, then add room temperature water.

[0012] Step 3: When the temperature drops to 60-65℃, add sodium fluorosilicate solution and stir for 10-15 minutes; add magnesium chloride solution and stir for 10-15 minutes; add sodium hexametaphosphate solution and stir for 10-15 minutes, keeping the temperature below 65℃; then add silicon nitride powder solution, keeping the temperature below 60℃ and stirring for 10-15 minutes; finally add calcium chloride solution and stir for 10-15 minutes.

[0013] Step 4: Slowly add potassium chloride granules for the second time. Stop feeding when the temperature reaches 80℃, add room temperature water, and continue feeding when the temperature drops to 60-65℃ until all the remaining potassium chloride granules are added.

[0014] Step 5: Add the chelating dispersant, stir for 10-15 minutes, then add sodium gluconate and the remaining room temperature water, and stir continuously for 48-50 hours.

[0015] Implementation Method 7. A permeable concrete pavement, comprising:

[0016] A cement concrete base layer, and a permeable concrete layer laid on the cement concrete base layer.

[0017] The materials used to prepare the permeable concrete layer include: 16-20 parts by weight of cement, 80-84 parts by weight of crushed stone, water to achieve a water-cement ratio of 0.33 to 0.36, an inorganic reinforcing agent, and optional pigments.

[0018] The inorganic reinforcing agent includes the permeable concrete admixture described in any one of embodiments 1 to 5.

[0019] Embodiment 8. The permeable concrete pavement according to Embodiment 7, characterized in that the content of the permeable concrete admixture in the material for preparing the permeable concrete layer is 0.4 to 1 wt%, for example, 0.4 to 0.7 wt%.

[0020] Implementation Method 9. The permeable concrete pavement according to Implementation Method 7, characterized in that the permeable concrete layer preparation material further includes 3-5 wt% fine sand.

[0021] Implementation Method 10. The permeable concrete pavement according to Implementation Method 7, characterized in that the crushed stone comprises a combination of the following two types of stone:

[0022] 20wt% to 40wt% of aggregate with a particle size greater than or equal to 5mm and less than 10mm, and

[0023] 60wt% to 80wt% of the stone has a particle size of 3mm or greater to less than 5mm.

[0024] Implementation Method 11. The bus station ground according to Implementation Method 7, characterized in that a cement slurry layer is provided between the permeable concrete layer and the cement concrete base layer for bonding the cement concrete base layer and the permeable concrete layer, and the cement slurry layer is prepared by the permeable concrete admixture.

[0025] Implementation Method 12. The bus station ground according to Implementation Method 11, characterized in that the cement slurry layer is prepared from the following raw materials: 30-35 wt% slurry cement, 0.4 to 1.5 wt% of the permeable concrete admixture, and the balance water.

[0026] Using the permeable concrete admixture disclosed in this application enables permeable concrete to possess excellent mechanical and durability properties. The resulting concrete exhibits extremely high compressive and flexural strength, along with excellent frost resistance. Since the permeable concrete admixture is made entirely of inorganic materials, it is unaffected by environmental and climatic conditions, can withstand high and low temperature changes, and is suitable for a wide range of outdoor environments. The inorganic salt components in the raw materials promote snow melting and inhibit road icing, making it particularly suitable for paving permeable pavements in cold regions. It can keep the road surface dry during rain and snow while significantly inhibiting snow and ice formation, improving vehicle safety, slowing down road aging, and extending the service life of the pavement. Furthermore, the technical solution of this application brings many other advantages, which will be described in detail in the specific embodiments. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure.

[0028] Figure 1 This is a schematic diagram of the permeable concrete pavement structure.

[0029] Figure 2 This is a diagram illustrating the low-temperature water seepage test of this application.

[0030] Figure label:

[0031] 1-Permeable concrete layer, 2-Cement grout layer, 3-Cement concrete base layer. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0033] In this application, unless otherwise specified or the meaning may be derived differently from the context, the terms have the meaning as commonly understood in the art.

[0034] This application discloses a permeable concrete admixture, characterized by comprising the following components in the following weight percentages: 5-8 wt% boric acid, 3-9 wt% sodium fluorosilicate, 12-15 wt% magnesium chloride, 2-8 wt% sodium hexametaphosphate, 2-4 wt% silicon nitride powder, 4-10 wt% potassium chloride, 10-12 wt% calcium chloride, 0.1-0.2 wt% chelating dispersant, 0.05-0.09 wt% sodium gluconate, and the balance being water. The permeable concrete admixture contains positively charged magnesium, calcium, potassium, and sodium ions, which can replace cations on the surface of cement colloids, giving them stronger adhesion and forming a stronger coating on the aggregates in the concrete. The permeable concrete admixture also contains special chemical components such as boric acid, sodium fluorosilicate, and silicon nitride powder, which can chemically react with cement, promoting cement setting and solidification, thereby effectively improving the compressive and flexural strength of the permeable concrete. The permeable concrete admixture contains calcium chloride, magnesium chloride, and potassium chloride. These chloride salts have significant snow-melting and ice-inhibiting effects. The applicant unexpectedly discovered that adding a certain proportion of these chloride salts to the permeable concrete admixture can significantly enhance the freeze-thaw resistance of permeable concrete while maintaining its strength, thus solving the problems of low strength and freeze-thaw damage. The volume expansion of liquid water after solidification is considered a significant factor in freeze-thaw damage to permeable concrete. The enhanced freeze-thaw resistance in this application can be explained by the presence of chloride salts inhibiting the solidification of liquid water in the pores of the permeable concrete under low-temperature conditions.

[0035] In this application, "road surface" and "ground surface" have the same meaning. "Parts by weight" in this application refers to the relative weight ratio between the components in the same composition. "Weight percentage" (wt%) refers to the relative weight of each component in the composition relative to the whole composition.

[0036] The term "permeable concrete layer" refers to a concrete layer on the ground that has a certain amount of interconnected pores to meet the requirements of permeability.

[0037] The term "water-cement ratio" has the common meaning understood by those skilled in the art, namely, the weight ratio of water to cement in concrete.

[0038] The term "crushed stone" refers to stone or natural pebbles made by crushing rocks. There are no particular limitations on its shape and size, as long as it serves as a skeleton and filler in the permeable concrete layer.

[0039] The term "inorganic reinforcing agent" refers to an additive mainly made of inorganic raw materials used to improve the mechanical properties of concrete. However, it should be understood that, firstly, reinforcing agents whose main raw materials are inorganic substances but contain a small amount of organic substances also belong to the inorganic reinforcing agents described in this application. Secondly, the technical effects produced by adding the inorganic reinforcing agent are not limited to the improvement of the mechanical properties of concrete.

[0040] In some embodiments, the weight fraction of the components is: 6-7 wt% boric acid, 5-7 wt% sodium fluorosilicate, 13-14 wt% magnesium chloride, 4-6 wt% sodium hexametaphosphate, 2.5-3.5 wt% silicon nitride powder, 5-8 wt% potassium chloride, 10.5-11.5 wt% calcium chloride, 0.13-0.17 wt% chelating dispersant, 0.06-0.08 wt% sodium gluconate, and the balance being water.

[0041] In some embodiments, the weight fractions of the components are: 6.5 wt% boric acid, 6 wt% sodium fluorosilicate, 13.5 wt% magnesium chloride, 5 wt% sodium hexametaphosphate, 3 wt% silicon nitride powder, 6.5 wt% potassium chloride, 11 wt% calcium chloride, 0.15 wt% chelating dispersant, 0.07 wt% sodium gluconate, and the balance being water.

[0042] In some embodiments, the chelating dispersant is at least one selected from maleic acid-acrylic acid copolymer, aminotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentamethylphosphonic acid, diethylenetriaminepentaacetic acid, and sodium ethylenediaminedi-o-phenylacetate.

[0043] In some embodiments, the boric acid, sodium fluorosilicate, magnesium chloride, sodium hexametaphosphate, silicon nitride powder, potassium chloride, and calcium chloride are of analytical grade.

[0044] This application also discloses a method for preparing the permeable concrete admixture, comprising the following steps:

[0045] Step 1: Add boric acid, sodium fluorosilicate, magnesium chloride, sodium hexametaphosphate, silicon nitride powder, calcium chloride, chelating dispersant, and sodium gluconate to appropriate amounts of water to prepare boric acid solution, sodium fluorosilicate solution, magnesium chloride solution, sodium hexametaphosphate solution, silicon nitride powder solution, calcium chloride solution, chelating dispersant solution, and sodium gluconate solution for later use.

[0046] Step 2: Slowly add potassium chloride granules to the stirred boric acid solution until the temperature rises to 80-85℃, then stop feeding and add room temperature water. When the temperature inside the vessel drops to 60-65℃, continue feeding. Repeat this step until the amount of potassium chloride granules added reaches 35-45% of the total amount, then add room temperature water.

[0047] Step 3: When the temperature drops to 60-65℃, add sodium fluorosilicate solution and stir for 10-15 minutes; add magnesium chloride solution and stir for 10-15 minutes; add sodium hexametaphosphate solution and stir for 10-15 minutes, keeping the temperature below 65℃; then add silicon nitride powder solution, keeping the temperature below 60℃ and stirring for 10-15 minutes; finally add calcium chloride solution and stir for 10-15 minutes.

[0048] Step 4: Slowly add potassium chloride granules for the second time. Stop feeding when the temperature reaches 80℃, add room temperature water, and continue feeding when the temperature drops to 60-65℃ until all the remaining potassium chloride granules are added.

[0049] Step 5: Add the chelating dispersant, stir for 10-15 minutes, then add sodium gluconate and the remaining room temperature water, and stir continuously for 48-50 hours.

[0050] This application also discloses a permeable concrete pavement, comprising: a cement concrete base layer, and a permeable concrete layer laid on the cement concrete base layer. The permeable concrete layer is prepared from materials including: 16-20 parts by weight of cement, 80-84 parts by weight of crushed stone, water to achieve a water-cement ratio of 0.33 to 0.36, an inorganic reinforcing agent, and optional pigments. The inorganic reinforcing agent includes the permeable concrete admixture. The permeable concrete layer possesses excellent permeability, allowing surface water to infiltrate rapidly. The cement concrete base layer is impermeable conventional cement concrete, capable of withstanding the heavy load transmitted by the permeable concrete layer. While stabilizing the ground structure, it prevents infiltrated water from further infiltrating into the underlying base structure, thus ensuring the long-term stability of the ground. The permeable concrete prepared using the mix proportions provided in this application has a good pore structure, exhibiting excellent permeability, and also possesses extremely high compressive and flexural strength. Because the permeable concrete admixture contains a significant amount of calcium chloride, magnesium chloride, and an appropriate amount of potassium chloride, it can significantly inhibit water solidification and freezing inside and on the surface of the permeable concrete layer under low-temperature conditions, and allow rainwater or melted snow to quickly infiltrate and drain away. This significantly improves the freeze-thaw damage of permeable concrete in cold regions, keeps the road surface dry in rainy and snowy weather while significantly inhibiting snow and ice formation, improving vehicle safety, slowing down road aging, and extending the service life of the road surface. In some preferred embodiments, the permeable concrete layer also includes pigments, allowing the color of the permeable concrete pavement to be designed according to actual needs.

[0051] In some embodiments, the content of the permeable concrete admixture in the material for preparing the permeable concrete layer is 0.4 to 1 wt%, for example, 0.4 to 0.7 wt%.

[0052] In some embodiments, the permeable concrete layer also includes 3-5 wt% fine sand in its preparation materials.

[0053] In some embodiments, the crushed stone comprises a combination of two types of stone: 20 wt% to 40 wt% of stone with a particle size greater than or equal to 5 mm and less than 10 mm, and 60 wt% to 80 wt% of stone with a particle size greater than or equal to 3 mm and less than 5 mm. The crushed stone used in this application is typically prepared from diabase, basalt, or limestone. The applicant has found that using a ratio of two different particle sizes of crushed stone can achieve higher mechanical properties, and a higher proportion of 3 mm to 5 mm stone, such as 60 wt% to 80 wt%, enables the permeable concrete to exhibit better permeability at low temperatures.

[0054] In some embodiments, a cement slurry layer is provided between the permeable concrete layer and the cement concrete base layer to bond them together. The cement slurry layer is prepared using the permeable concrete admixture. This arrangement effectively prevents delamination between the cement concrete base layer and the permeable concrete layer during construction. By providing a cement slurry layer with the permeable concrete admixture at the interface, the cement concrete base layer and the permeable concrete layer are effectively bonded, preventing the aforementioned delamination. The composite of the two layers gives the ground higher compressive and flexural strength. During construction, roughening the surface of the cement concrete base layer to increase its roughness, combined with the cement slurry layer, further enhances the effect.

[0055] In some embodiments, the cement slurry layer is prepared from the following raw materials: 30-35 wt% slurry cement, 0.4 to 1.5 wt% of the permeable concrete admixture, and the balance water.

[0056] The scope described above can be used alone or in combination. The following examples will make this application easier to understand.

[0057] Example

[0058] The sources of raw materials used in the embodiments of this application are shown in Table 1. Other materials not listed in the table are all conventional commercially available products.

[0059] Table 1

[0060]

[0061] Example 1

[0062] 1. Preparation of permeable concrete admixtures

[0063] Weigh appropriate amounts of raw materials according to the weight fraction ratio shown in Table 2, and prepare permeable concrete admixtures using the method disclosed in this application. The prepared admixtures are numbered sequentially as 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, 1-7, 1-8, 1-9, and 1-10.

[0064] Table 2

[0065]

[0066] 2. Preparation and freezing of permeable concrete test blocks

[0067] After measuring and mixing 20 parts by weight of cement and 80 parts by weight of crushed stone, and after the mixture is evenly mixed, 7 parts by weight of water (water-cement ratio 0.35) and 0.5 parts by weight of the prepared permeable concrete admixture are added to the mixed cement and crushed stone. The mixture is then thoroughly mixed for approximately 120 seconds to prepare the permeable concrete mixture. Depending on the consistency of the mixture, the mechanical mixing time can be appropriately extended, but should not exceed 5 minutes. The cement used is PO.42.5 ordinary Portland cement produced by Conch Cement Co., Ltd., the water is tap water, and the crushed stone is diabase crushed stone produced by impact crusher technology. The crushed stone composition is: 40 wt% stone with a particle size greater than or equal to 5 mm and less than 10 mm, and 60 wt% stone with a particle size greater than or equal to 3 mm and less than 5 mm.

[0068] Permeable concrete mixtures were prepared into 100mm×100mm×150mm concrete blocks, numbered 2-1, 2-2, 2-3, 2-4, 2-5, 2-6, 2-7, 2-8, 2-9, and 2-10 according to different permeable concrete admixtures. The blocks were removed at 24 days of age and then soaked in 20℃ water for 4 days. At 28 days of age, the blocks were removed and placed in a water cup, with the water level just covering the top of the block. They were then placed in a -18℃ freezer for 4 hours. After freezing, the appearance of the permeable concrete was observed, and a low-temperature water permeability test was conducted. Another set of blocks was prepared for compressive strength testing at 28 days.

[0069] 3. Observation of freezing and icing and observation of low-temperature water seepage test

[0070] The procedure for observing freezing and icing is as follows: visually observe the distribution of ice crystals on the surface and in the pores of the permeable concrete test block to intuitively judge the freezing condition of the permeable concrete test block, and immediately conduct a low-temperature water permeability test after observation.

[0071] The procedure for the low-temperature permeability test is as follows: Place the permeable concrete specimen on a flat surface. If there is ice on the top surface of the specimen, remove the ice. Then, open a 600ml bottle of "Master Kong" brand mineral water (bottle opening diameter 2cm) and quickly pour it onto the top surface of the concrete specimen, allowing the water to flow naturally until the bottle dries out. Observe the flow and seepage of water on the specimen to visually determine its permeability. The results are shown in Table 3.

[0072] Table 3

[0073]

[0074]

[0075] The observations and measurement data above show that, based on the permeable concrete admixture components of Experiment 1-1, reducing the proportion of boric acid and adding potassium chloride, calcium chloride, and magnesium chloride significantly inhibits the freezing of water in the pores of permeable concrete under low-temperature conditions. The distribution of ice crystals within the pores is minimal, thus maintaining good permeability of the permeable concrete (refer to Experiments 2-8, 2-9, and 2-10). Adding only magnesium chloride or calcium chloride in addition to potassium chloride reduces the effectiveness of inhibiting water freezing. Even with fewer ice crystals observed in the surface pores, the permeability of the permeable concrete specimens after low-temperature freezing is still inhibited (refer to Experiments 2-2, 2-3, 2-4, 2-5, 2-6, and 2-7). Based on the 28-day compressive strength measurements of permeable concrete, the permeable concrete specimen prepared with the permeable concrete admixture component of test number 1-1 (test number 2-1) exhibited a higher 28-day compressive strength value, reaching 36.7 MPa. The 28-day compressive strength values ​​of the remaining permeable concrete specimens all showed varying degrees of decrease. Comparing the three groups of permeable concrete specimens (test numbers 2-8, 2-9, and 2-10) that demonstrated excellent low-temperature permeability, the permeable concrete specimens of tests 2-8 and 2-9 still exhibited high strength. This indicates that the appropriate proportions of the three chloride salts in the permeable concrete admixture can maintain high strength values ​​while ensuring excellent low-temperature permeability of the permeable concrete.

[0076] Example 2

[0077] 1. Preparation of permeable concrete admixtures

[0078] Weigh appropriate amounts of raw materials according to the weight fraction ratio shown in Table 4, and prepare permeable concrete admixtures using the method disclosed in this application, numbered sequentially as 3-1, 3-2, 3-3, and 3-4.

[0079] Table 4

[0080]

[0081] 2. Preparation and freezing of concrete test blocks

[0082] Permeable concrete specimens were prepared using the same method as in Example 1, and were numbered 4-1, 4-2, 4-3, and 4-4 according to different permeable concrete admixtures. Freezing and freezing observations, low-temperature water permeability tests, and 28-day compressive strength measurements were then conducted. The results are shown in Table 5.

[0083] Table 5

[0084]

[0085] The above observations and measurements show that when the permeable concrete admixture contains potassium chloride, calcium chloride, and magnesium chloride simultaneously, the water solidification within the permeable concrete is significantly inhibited, resulting in good permeability. However, when the potassium chloride content in the permeable concrete admixture is high (exceeding 10 wt%), the 28-day compressive strength of the permeable concrete specimens decreases significantly. To balance the strength and low-temperature permeability of permeable concrete, the potassium chloride content in the admixture needs to be controlled below 10 wt%. The ratio of calcium chloride to magnesium chloride can significantly affect the compressive strength of permeable concrete.

[0086] Example 3

[0087] In this embodiment, permeable concrete admixtures were prepared using different ratios of calcium chloride and magnesium chloride (the dosage of other components was the same as in test number 3-2). Permeable concrete test blocks were prepared using the same method as in Example 1, and the 28-day compressive strength values ​​under different ratios were measured. The test results are shown in Table 6, where a compressive strength value greater than or equal to 35 MPa is considered qualified, and a value less than 35 MPa is considered unqualified.

[0088] Table 6

[0089]

[0090]

[0091] As can be seen from the table above, based on test number 3-2, the admixture containing 10-12 wt% calcium chloride and 10-15 wt% magnesium chloride can achieve higher compressive strength (≥35 MPa).

[0092] Example 4

[0093] The permeable concrete admixture was prepared using the same method as in Example 1. The admixture was formulated as follows: 6 wt% boric acid, 6 wt% sodium fluorosilicate, 10 wt% magnesium chloride, 5 wt% sodium hexametaphosphate, 3 wt% silicon nitride powder, 5 wt% potassium chloride, 12 wt% calcium chloride, 0.15 wt% chelating dispersant (maleic acid-acrylic acid copolymer), 0.07 wt% sodium gluconate, and the balance being water.

[0094] Permeable concrete test blocks were prepared according to the mix proportions shown in Table 7 and frozen. Freezing and low-temperature permeability tests were then conducted. For tests 5-1 and 5-3, the aggregate composition was: 70 wt% aggregate with a particle size greater than or equal to 5 mm and less than 10 mm, and 30 wt% aggregate with a particle size greater than or equal to 3 mm and less than 5 mm. For tests 5-2 and 5-4, the aggregate composition was: 30 wt% aggregate with a particle size greater than or equal to 5 mm and less than 10 mm, and 70 wt% aggregate with a particle size greater than or equal to 3 mm and less than 5 mm. The fine sand used in tests 5-3 and 5-4 was river sand with a fineness of 20 mesh.

[0095] Table 7

[0096] Test number cement Crushed stone water admixtures fine sand 5-1 20 80 7 0.5 0 5-2 20 80 7 0.5 0 5-3 20 80 7 0.5 5 5-4 20 80 7 0.5 5

[0097] The results of the freezing and icing observations and the low-temperature water seepage test are shown in Table 8.

[0098] Table 8

[0099]

[0100]

[0101] The above results indicate that increasing the particle size of the aggregate from 3 mm to less than 5 mm and / or adding a small amount of fine sand can further inhibit the low-temperature solidification of water within the pores of permeable concrete, enhancing its low-temperature permeability. In the low-temperature permeability tests numbered 5-2, 5-3, and 5-4, water only diffused slightly around the top of the container before rapidly seeping downwards, exhibiting permeability consistent with that of permeable concrete at room temperature, indicating excellent low-temperature permeability. This can be explained by the fact that increasing the size of the aggregate or adding a small amount of fine sand reduces the formation of large, interconnected pores in the permeable concrete. In smaller pores, water is less likely to solidify and freeze, resulting in excellent low-temperature permeability. Furthermore, it inhibits the freezing of water within the pores, significantly reducing freeze-thaw damage and thus improving the permeability of the concrete.

[0102] Example 5

[0103] 1. Preparation of permeable concrete admixtures

[0104] Weigh appropriate amounts of raw materials according to the weight fraction ratio shown in Table 9, and prepare permeable concrete admixtures using the method disclosed in this application, numbered 6-1 and 6-2 in sequence.

[0105] Table 9

[0106]

[0107] 2. Preparation of permeable concrete

[0108] Permeable concrete was prepared using the same mix proportion as test number 5-1 in Example 4, and the permeable concrete admixture of test number 6-1 was used, corresponding to test number 7-1.

[0109] Permeable concrete was prepared using the same mix proportion as test number 5-4 in Example 4, and the permeable concrete admixture used was the same as that used in test number 6-2, corresponding to test number 7-2.

[0110] For the above-mentioned permeable concrete, testing was conducted in accordance with the "Technical Specification for Permeable Cement Concrete Pavement (CJJ / T135-2009)" and the test results are shown in Table 10.

[0111] Table 10

[0112]

[0113]

[0114] Conclusion: The freeze-thaw resistance is significantly improved. After 25 freeze-thaw cycles, the compressive strength and mass loss are minimal, the permeability meets the standards, and the compressive and flexural strengths are maintained. It has excellent mechanical and durability properties and is very suitable for addressing the problems of low strength and severe freeze-thaw damage of permeable concrete in cold regions.

[0115] Example 6

[0116] This embodiment discloses a permeable concrete pavement, which includes a base layer and a cement concrete base layer 3 laid on the base layer, and a permeable concrete layer 1 laid on the cement concrete base layer (as shown in the attached figure). Figure 1 As shown in the diagram, a cement grout layer 2 is provided between the cement concrete base layer and the permeable concrete layer to bond the cement concrete base layer and the permeable concrete layer. The cement concrete base layer is provided with a drainage structure. The permeable concrete pavement is laid as follows:

[0117] 1. Foundation layer, cement concrete base layer and drainage structure

[0118] The foundation layer is the basic structure, and its construction is consistent with that of conventional site base construction, such as the sequential process of compacting plain soil, backfilling with sand and gravel, and preparing graded crushed stone.

[0119] The cement concrete base layer 3 is made of impermeable C25 cement concrete, which can withstand the heavy pressure transmitted by the permeable concrete layer 1. While stabilizing the ground structure, it can prevent the seeping water from further seeping into the lower foundation structure, so that the ground has long-term stability.

[0120] The drainage structure is configured as follows: the upper surface of the cement concrete base layer is inclined at an angle of 0.1–2% towards the drainage system, and a groove connected to the drainage system is provided on the upper surface of the cement concrete base layer, thereby enabling the water infiltrated from the ground to be quickly guided into the drainage system.

[0121] 2. Preparation of permeable concrete admixtures

[0122] The permeable concrete admixture comprises: 6.5 wt% boric acid, 6 wt% sodium fluorosilicate, 13 wt% magnesium chloride, 5 wt% sodium hexametaphosphate, 3 wt% silicon nitride powder, 6.5 wt% potassium chloride, 11 wt% calcium chloride, 0.15 wt% chelating dispersant (maleic acid-acrylic acid copolymer), 0.07 wt% sodium gluconate, and the balance being water.

[0123] The permeable concrete admixture is prepared using the following process:

[0124] Step 1: Dissolve the measured boric acid, sodium fluorosilicate, magnesium chloride, sodium hexametaphosphate, silicon nitride powder, calcium chloride, chelating dispersant, and sodium gluconate in an appropriate amount of water to prepare boric acid solution, sodium fluorosilicate solution, magnesium chloride solution, sodium hexametaphosphate solution, silicon nitride powder solution, calcium chloride solution, chelating dispersant solution, and sodium gluconate solution for later use.

[0125] Step 2: Slowly add potassium chloride granules to the stirred boric acid solution until the temperature rises to 80-85℃, then stop feeding and add room temperature water. When the temperature inside the vessel drops to 60-65℃, continue feeding. Repeat this step until the amount of potassium chloride granules added reaches 35-45% of the total amount, then add room temperature water.

[0126] Step 3: When the temperature drops to 60-65℃, add sodium fluorosilicate solution and stir for 10-15 minutes; add magnesium chloride solution and stir for 10-15 minutes; add sodium hexametaphosphate solution and stir for 10-15 minutes, keeping the temperature below 65℃; then add silicon nitride powder solution, keeping the temperature below 60℃ and stirring for 10-15 minutes; finally add calcium chloride solution and stir for 10-15 minutes.

[0127] Step 4: Slowly add potassium chloride granules for the second time. Stop feeding when the temperature reaches 80℃, add room temperature water, and continue feeding when the temperature drops to 60-65℃ until all the remaining potassium chloride granules are added.

[0128] Step 5: Add the chelating dispersant, stir for 10-15 minutes, then add sodium gluconate and the remaining room temperature water, and stir continuously for 48-50 hours. The permeable concrete admixture is thus obtained.

[0129] 3. Cement grout layer

[0130] The cement slurry used in the cement slurry layer 2 is prepared by mixing the following raw materials in the following weight percentages: 35 wt% cement, 64.2 wt% water, and 0.8 wt% permeable concrete admixture. The cement used is PO.42.5 ordinary Portland cement produced by Conch Cement Co., Ltd., and the water is local tap water. The cement slurry is mixed on-site and then sprayed evenly onto the surface of the cement concrete base layer in a timely manner, with a thickness of less than 1 mm. The permeable concrete layer is then laid while the surface is moist, thus ensuring adhesion between the cement concrete base layer and the permeable concrete layer.

[0131] 4. Permeable concrete layer

[0132] The permeable concrete layer 1 is prepared using the following raw materials in parts by weight to form the permeable concrete mixture: 18 parts by weight of cement, 82 parts by weight of crushed stone, 6 parts by weight of water (water-cement ratio 0.33), and 0.6 parts by weight of permeable concrete admixture. The cement used is PO.42.5 ordinary Portland cement produced by Conch Cement Corporation, the water is local tap water, and the crushed stone is diabase crushed stone produced using impact crushing technology. Due to the high proportion of round and conical crushed stone and the low proportion of flaky crushed stone produced by impact crushing technology, the diabase crushed stone has better permeability. The permeable concrete layer exhibits excellent mechanical properties, significantly enhancing the compressive and flexural strength and impact resistance of the pavement. The crushed stone in this layer comprises 30 wt% aggregates with a particle size greater than or equal to 5 mm and less than 10 mm, and 70 wt% aggregates with a particle size greater than or equal to 3 mm and less than 5 mm. This combination of different particle sizes allows the permeable concrete to have smaller pores, thereby inhibiting the freezing of water within the pores and resulting in excellent low-temperature permeability. This significantly reduces freeze-thaw damage to the permeable concrete, thus improving its frost resistance. The permissible error for raw materials (by weight) should not exceed the following: cement ±1%, crushed stone ±2%, permeable concrete admixtures ±1%, water ±1%.

[0133] The permeable concrete layer mixture is prepared using the following process: the measured crushed stone and cement are put into a forced mixer and dry-mixed for 15 seconds. After the mixture is evenly mixed, the measured water and permeable concrete admixture are added to the mixer and thoroughly mixed for about 150 seconds. Depending on the consistency of the mixture, the mechanical mixing time can be appropriately extended, but it should not exceed 5 minutes.

[0134] During transportation, the permeable concrete mixture should be protected from segregation and initial setting. Maintaining the moisture content of the mixture is crucial. In hot weather or during transport exceeding 10 minutes, covering measures should be taken. The permeable concrete layer is 200mm thick and can be laid in a single pass to complete the permeable concrete pavement installation.

[0135] The present invention has been described through the above embodiments. However, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, those skilled in the art will understand that the present invention is not limited to the above embodiments, and many more variations and modifications can be made based on the teachings of the present invention, all of which fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A pervious concrete admixture characterized by The components include the following weight fractions Composition: 5-8wt% boric acid, 3-9wt% sodium fluorosilicate, 12-15wt% magnesium chloride, 2-8wt% sodium hexametaphosphate, 2-4wt% silicon nitride powder, 4-10wt% potassium chloride, 10-12wt% calcium chloride, 0.1-0.2wt% chelating dispersant, 0.05-0.09wt% sodium gluconate, and the balance water.

2. The pervious concrete admixture of claim 1, wherein The weight fractions of the components are: 6-7wt% boric acid, 5-7wt% sodium fluorosilicate, 13-14wt% magnesium chloride, 4-6wt% sodium hexametaphosphate, 2.5-3.5wt% silicon nitride powder, 5-8wt% potassium chloride, 10.5-11.5wt% calcium chloride, 0.13-0.17wt% chelating dispersant, 0.06-0.08wt% sodium gluconate, and the balance water.

3. The pervious concrete admixture of claim 1, wherein the weight fractions of the components are: 6.5wt% boric acid, 6wt% sodium fluorosilicate, 13.5wt% magnesium chloride, 5wt% sodium hexametaphosphate, 3wt% silicon nitride powder, 6.5wt% potassium chloride, 11wt% calcium chloride, 0.15wt% chelating dispersant, 0.07wt% sodium gluconate, and the balance water.

4. The pervious concrete admixture of claim 1, wherein the chelating dispersant is at least one of maleic acid-acrylic acid copolymer, amino triacetic acid, ethylenediaminetetraacetic acid, diethylenetriamine pentamethylene phosphonic acid, diethylenetriamine pentaacetic acid, and sodium ethylenediamine di-o-phenyl acetic acid.

5. The pervious concrete admixture of claim 1, wherein the boric acid, sodium fluorosilicate, magnesium chloride, sodium hexametaphosphate, silicon nitride powder, potassium chloride, and calcium chloride are all of analytical purity.

6. A method for preparing the pervious concrete admixture of any one of claims 1 to 5, comprising the following steps: First step: separately adding boric acid, sodium fluorosilicate, magnesium chloride, sodium hexametaphosphate, silicon nitride powder, calcium chloride, chelating dispersant, and sodium gluconate into appropriate amounts of water to prepare boric acid solution, sodium fluorosilicate solution, magnesium chloride solution, sodium hexametaphosphate solution, silicon nitride powder solution, calcium chloride solution, chelating dispersant solution, and sodium gluconate solution for standby; Second step: slowly adding potassium chloride particles to the stirring boric acid solution until the temperature rises to 80-85°C, stopping the addition, adding normal temperature water, and continuing the addition when the temperature in the kettle drops to 60-65°C, repeating the process until the amount of potassium chloride particles added reaches 35 to 45% of the total amount, and then injecting normal temperature water; Third step: when the temperature drops to 60-65°C, adding the sodium fluorosilicate solution, stirring for 10-15 minutes; adding the magnesium chloride solution, stirring for 10-15 minutes; adding the sodium hexametaphosphate solution, stirring for 10-15 minutes, and controlling the temperature below 65°C; then adding the silicon nitride powder solution, controlling the temperature below 60°C, and stirring for 10-15 minutes; and then adding the calcium chloride solution and stirring for 10-15 minutes. ​ Fourth step: secondly, slowly add potassium chloride particles, stop feeding when the temperature rises to 80℃, add normal temperature water, continue feeding until the remaining potassium chloride particles are completely added when the temperature drops to 60-65℃; Fifth step: add chelating dispersant, stir for 10-15 minutes, then add sodium gluconate and the remaining normal temperature water, continuously stir for 48-50 hours.

7. A pervious concrete pavement comprising: a cement concrete base, and a pervious concrete layer laid on the cement concrete base, the pervious concrete layer is prepared from 16-20 parts by weight of cement, 80-84 parts by weight of crushed stone, water with a water-cement ratio of 0.33 to 0.36, an inorganic reinforcing agent, and optionally pigments, the inorganic reinforcing agent comprises the pervious concrete admixture of any one of claims 1 to 5.

8. The pervious concrete pavement of claim 7, wherein, the content of the pervious concrete admixture in the pervious concrete layer is 0.4 to 1 wt%.

9. The pervious concrete pavement of claim 7, wherein, the pervious concrete layer further comprises 3-5 wt% of fine sand.

10. The pervious concrete pavement of claim 7, wherein, the crushed stone comprises a combination of two types of stone: 20 wt% to 40 wt% of stone with a particle size of greater than or equal to 5 mm to less than 10 mm, and 60 wt% to 80 wt% of stone with a particle size of greater than or equal to 3 mm to less than 5 mm.

11. The pervious concrete pavement of claim 7, wherein, a cement paste layer is provided between the pervious concrete layer and the cement concrete base for bonding the cement concrete base and the pervious concrete layer, the cement paste layer is prepared from the pervious concrete admixture.

12. The pervious concrete pavement of claim 11, wherein, the cement paste layer is prepared from: 30-35 wt% of paste cement, 0.4 to 1.5 wt% of the pervious concrete admixture, and the balance of water.

13. The pervious concrete pavement of claim 7, wherein, the content of the pervious concrete admixture in the pervious concrete layer is 0.4 to 0.7 wt%. the cement paste layer is prepared from: 30-35 wt% of paste cement, 0.4 to 1.5 wt% of the pervious concrete admixture, and the balance of water.

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