High flexural strength cement for road and bridge pavement and its preparation method

Abstract

The application belongs to the field of building engineering materials, and more particularly relates to a high-bending-resistance road and bridge pavement layer cement and a preparation method thereof. The high-bending-resistance road and bridge pavement layer cement comprises, in mass parts, 100-130 parts of gel material, 40-70 parts of filling material, 20-30 parts of reinforcing fiber, 120-240 parts of aggregate, 1.5-2.5 parts of water reducing agent, 0.5-2 parts of cellulose ether, 3-6 parts of toughening agent, 0.3-0.8 parts of defoaming agent, 10-20 parts of combined reinforcing agent, and 50-100 parts of water. The pavement cement prepared by the application has excellent workability and long-term durability, and can simultaneously greatly improve the bending strength, waterproofness and moisture resistance, thereby greatly improving the comprehensive performance of the pavement cement, improving the application effect and quality, and solving the problems in the prior art.

Description

Technical Field

[0001] This application belongs to the field of building materials, and more specifically relates to a high flexural strength cement for road and bridge pavement and its preparation method. Background Technology

[0002] Currently, road and bridge pavement layers are critical components bearing vehicle loads, environmental effects, and fatigue effects, and their performance directly impacts the safety and durability of road and bridge structures. In traditional road and bridge pavement projects, ordinary silicate cement concrete or high-strength concrete are commonly used as pavement materials. These materials primarily meet load-bearing requirements by increasing their strength grade, and their compressive strength is relatively well-developed; however, improvements in flexural strength are often limited. In actual engineering projects, pavement layers not only bear enormous vertical pressure but are also prone to flexural stress due to repeated impacts from vehicles, temperature gradient changes, and base layer deformation. When the flexural strength of the concrete is insufficient, it easily induces the generation and propagation of microcracks, leading to early cracking, spalling, and water seepage in the pavement layer, severely shortening the service life of roads and bridges and increasing subsequent maintenance costs.

[0003] To improve the flexural properties of cement concrete pavement, a series of technological explorations have been undertaken. For example, by incorporating short-cut fibers such as steel fibers and synthetic fibers into the concrete, the random distribution of fibers in the matrix can bridge cracks, thereby inhibiting crack propagation and improving flexural strength to some extent. In addition, some technical solutions employ polymer-modified cementitious materials, introducing polymer emulsions or redispersible latex powders into the cement paste to improve the toughness and bonding properties of the cement paste through polymer film-forming characteristics. Another common approach is to optimize aggregate gradation and incorporate active mineral admixtures such as silica fume, fly ash, and slag, indirectly enhancing the mechanical properties of the material by improving the density of the matrix and the performance of the interfacial transition zone. These measures can all produce certain improvements in the flexural properties of concrete under specific conditions.

[0004] However, the aforementioned existing technologies still have many limitations in practical applications. While the addition of fibers can improve flexural strength, it often comes with a significant decrease in the workability of concrete. Fibers are prone to clumping and uneven dispersion, which not only affects construction quality but also poses a risk of fiber debonding from the matrix under long-term dynamic loads, leading to a reduction in toughening effect. Polymer modification faces problems such as high cost, unstable aging resistance, and the potential introduction of excessive air bubbles that affect long-term strength. Furthermore, relying solely on mineral admixtures and gradation optimization offers limited improvement in flexural strength, making it difficult to meet the stringent requirements of high flexural performance for heavy-duty traffic bridges and roads. Summary of the Invention

[0005] In summary, how to provide a pavement cement material that ensures good workability and long-term durability while significantly and stably improving flexural strength has become an important issue facing existing researchers and manufacturers. Through in-depth research and practice in this technical field, the applicant has finally proposed a machine-made method for preparing high-flexural-strength road and bridge pavement cement. The pavement cement ultimately produced by this application not only possesses excellent workability and long-term durability but also significantly improves its flexural strength and waterproof and moisture-resistant properties, thereby greatly enhancing the overall performance of this type of pavement cement, improving application effects and quality, and solving existing technical problems.

[0006] A high flexural strength road and bridge pavement cement, by weight, comprises the following raw materials: 100-130 parts of gel material, 40-70 parts of filler material, 20-30 parts of reinforcing fiber, 120-240 parts of aggregate, 1.5-2.5 parts of water-reducing agent, 0.5-2 parts of cellulose ether, 3-6 parts of toughening agent, 0.3-0.8 parts of defoamer, 10-20 parts of combined reinforcing agent, and 50-100 parts of water.

[0007] Preferably, the gel material is a combination of ordinary silicate cement and silica fume.

[0008] Preferably, the mass ratio of the ordinary silicate cement to silica fume is (9~11):(2~3).

[0009] Preferably, the mass ratio of the ordinary silicate cement to silica fume is (10~10.5):(2~2.5).

[0010] Preferably, the ordinary silicate cement is PO 52.5 ordinary silicate cement or PO 52.5R ordinary silicate cement.

[0011] Preferably, the ordinary silicate cement is 52.5R ordinary silicate cement.

[0012] Preferably, the mass ratio of the gel material, reinforcing fiber, and combined reinforcing agent is (11~12):(2~2.5):(1.2~1.6).

[0013] Preferably, the mass ratio of the gel material, reinforcing fiber, and combined reinforcing agent is (11.5~12):(2.2~2.5):(1.3~1.5).

[0014] Preferably, the filler material is a combination of ground slag powder and ultrafine fly ash.

[0015] Preferably, the mass ratio of the ground slag powder to the ultrafine fly ash is (2.5~3.5):(1.5~2).

[0016] Preferably, the mass ratio of the ground slag powder to the ultrafine fly ash is (3~3.2):(1.8~2).

[0017] Preferably, the ground slag powder is of grade S95 or S105.

[0018] Preferably, the ground slag powder is grade S95.

[0019] Preferably, the average particle size D50 of the ultrafine fly ash is ≤12μm.

[0020] Preferably, the average particle size D50 of the ultrafine fly ash is 7.5~10μm.

[0021] Preferably, the reinforcing fiber is a combination of end-hooked steel fiber and modified polypropylene coarse fiber.

[0022] Preferably, the mass ratio of the end-hook type steel fiber to the modified polypropylene coarse fiber is (2~3):(0.5~1).

[0023] Preferably, the mass ratio of the end-hook type steel fiber to the modified polypropylene coarse fiber is (2.2~2.5):(0.6~0.7).

[0024] Preferably, the average length of the end-hook type steel fiber is 30~40mm.

[0025] Preferably, the aspect ratio of the hook-shaped steel fiber is 55~60.

[0026] Preferably, the average length of the modified polypropylene coarse fiber is 40-50 mm.

[0027] Preferably, the equivalent diameter of the modified polypropylene coarse fiber is 0.8~1mm.

[0028] Preferably, the aggregate is a composition of graded quartz sand and basalt manufactured sand.

[0029] Preferably, the mass ratio of the graded quartz sand to the basalt manufactured sand is (12~14):(7~10).

[0030] Preferably, the mass ratio of the graded quartz sand to the basalt manufactured sand is (12~13):(8~9).

[0031] Preferably, the water-reducing agent is a polycarboxylate-based water-reducing agent or a polycarboxylate amide-based water-reducing agent.

[0032] Preferably, the water-reducing agent is a high-performance polycarboxylate-based water-reducing agent.

[0033] Preferably, the cellulose ether is at least one selected from hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, carboxymethylcellulose, hydroxyethyl cellulose, and methylcellulose.

[0034] Preferably, the cellulose ether is hydroxypropyl methylcellulose and / or hydroxyethyl methylcellulose.

[0035] Preferably, the cellulose ether is hydroxypropyl methylcellulose and hydroxyethyl methylcellulose in a mass ratio of (3~5):(1~2).

[0036] Preferably, the mass ratio of hydroxypropyl methylcellulose to hydroxyethyl methylcellulose is (3~4):(1.2~1.5).

[0037] Preferably, the defoamer is at least one of silicone defoamers.

[0038] Preferably, the toughening agent is at least one of styrene-butadiene latex epoxy-modified acrylic emulsion, aqueous polyurethane dispersion emulsion, and nitrile latex.

[0039] Preferably, the combined reinforcing agent is a combination of epoxy-functionalized acrylic polymer and phosphonate.

[0040] Preferably, the mass ratio of the epoxy-functionalized acrylic polymer to the phosphonate is (3.5~4.5):(1~1.2).

[0041] Preferably, the mass ratio of the epoxy-functionalized acrylic polymer to the phosphonate is 4:1.

[0042] Preferably, the epoxy-functionalized acrylic polymer is Acronal® LR 9089, sourced from BASF, Germany.

[0043] Preferably, the phosphonate is a combination of aminotrimethylenephosphonic acid and hydroxyethylidene diphosphonic acid.

[0044] Preferably, the mass ratio of aminotrimethylenephosphonic acid to hydroxyethylidene diphosphonic acid is (2~3):1.

[0045] The composite reinforcing additive used in this application achieves a simultaneous and significant improvement in the flexural strength, toughness, and durability of cement materials used in road and bridge pavement layers. When the additive is introduced into the cement system, phosphonate ester molecules can be rapidly adsorbed onto the surface of cement particles and hydration products. On the one hand, this provides efficient dispersion and plasticization; on the other hand, the active phosphonate groups, in the alkaline environment of the cement paste, undergo ring-opening reactions with the active epoxy groups on the epoxy functionalized polymer molecular chains, forming strong covalent bonds. This fundamentally solves the core problem of weak interfacial bonding between the organic and inorganic phases in traditional modified materials. When the material is subjected to bending loads, stress is efficiently transferred from the brittle cement paste to the tough polymer phase through these chemical bonds, inducing the extension, slippage, and reorientation of the polymer molecular chains. This consumes a large amount of energy, effectively preventing the initiation and propagation of microcracks, resulting in excellent comprehensive properties such as high flexural strength, high toughness, and high durability.

[0046] A method for preparing high flexural strength road and bridge pavement cement includes the following steps: S1: All gel material, cellulose ether, aggregate and filler are put into a forced mixer and stirred at 30-50 rpm for 30-40 minutes until the materials are uniformly mixed. Then, 70 wt% water, water-reducing agent and defoamer are pre-mixed and then slowly poured into the forced mixer. The speed is increased to 60-80 rpm and stirred for 10-15 minutes. S2: Reinforcing fibers are added and stirring is continued for 10-15 minutes. At this time, the remaining 30 wt% water and combined reinforcing agent are mixed evenly and then added to the mixer and stirred for 10-15 minutes. After unloading, the material is allowed to stand and mature for 50-60 minutes. Before use, it is briefly re-stirred for 30-40 seconds to obtain the final product.

[0047] The application has practical and beneficial effects:

[0048] 1. The paving cement finally obtained by this application not only has excellent workability and long-term durability, but also significantly improves its flexural strength and waterproof and moisture-resistant properties, thereby greatly improving the overall performance of this type of paving cement, enhancing its application effect and quality, and solving existing technical problems.

[0049] 2. The most significant benefit of the high flexural strength road and bridge pavement cement provided in this application lies in the successful synergistic optimization of the material's macroscopic mechanical properties and long-term durability through innovative reinforcing additive design. This scheme utilizes the in-situ crosslinking reaction between epoxy functionalized polymers and phosphonate compounds to construct a robust chemical bond bridge between the rigid inorganic skeleton of the cement stone and the flexible organic polymer phase. This unique structure fundamentally improves the performance of the interfacial transition zone, enabling the material to effectively transfer and dissipate stress when subjected to flexural loads, thus exhibiting flexural strength and fracture toughness far exceeding that of ordinary concrete. Simultaneously, the dense composite network structure significantly enhances the material's volume stability and impermeability, enabling it to effectively resist the erosion of harmful media such as moisture and chloride ions, greatly extending the service life of the road and bridge pavement in harsh service environments, and fundamentally overcoming the technical bottleneck of traditional pavement layers being prone to cracking and damage.

[0050] 3. The composite reinforcing additive used in this application achieves a simultaneous leapfrog improvement in the flexural strength, toughness, and durability of cement materials in road and bridge pavement layers. When the additive is introduced into the cement system, phosphonate ester molecules can be rapidly adsorbed onto the surface of cement particles and hydration products. On the one hand, this provides efficient dispersion and plasticization; on the other hand, its active phosphonate groups, in the alkaline environment of the cement stone, undergo ring-opening reactions with the active epoxy groups on the epoxy functionalized polymer molecular chains, forming strong covalent bonds. This fundamentally solves the core problem of weak interfacial bonding between the organic and inorganic phases in traditional modified materials. When the material is subjected to bending loads, stress is efficiently transferred from the brittle cement stone to the tough polymer phase through these chemical bonds, inducing the extension, slippage, and reorientation of the polymer molecular chains. This consumes a large amount of energy, effectively preventing the initiation and propagation of microcracks, resulting in excellent comprehensive performance such as high flexural strength, high toughness, and high durability. Detailed Implementation

[0051] Example 1

[0052] A high flexural strength road and bridge pavement cement, by weight, comprises the following raw materials: 120 parts gel material, 55 parts filler, 25 parts reinforcing fiber, 180 parts aggregate, 2.2 parts water-reducing agent, 1.2 parts cellulose ether, 4.2 parts toughening agent, 0.5 parts defoamer, 14.5 parts composite reinforcing agent, and 75 parts water.

[0053] The gel material is a composition of ordinary silicate cement and silica fume in a mass ratio of 10:2.

[0054] The ordinary Portland cement is 52.5R ordinary Portland cement.

[0055] The filler material is a composition of ground slag powder and ultrafine fly ash in a mass ratio of 3.2:1.8.

[0056] The finely ground slag powder is grade S95; the average particle size D50 of the ultrafine fly ash is 8μm.

[0057] The reinforcing fiber is a composition of hooked steel fibers and modified polypropylene coarse fibers in a mass ratio of 2.4:0.6. The hooked steel fibers are Bekaert DRAMIX 65 / 35BN, sourced from Bekaert, Belgium. The modified polypropylene coarse fibers are ET-PP48, sourced from Enka, USA.

[0058] The average length of the hook-shaped steel fiber is 35 mm, and the aspect ratio is 60. The average length of the modified polypropylene coarse fiber is 45 mm, and the equivalent diameter is 0.8 mm.

[0059] The aggregate is a composition of graded quartz sand and basalt manufactured sand in a mass ratio of 13:9. The average particle size of the graded quartz sand is 1.88 mm, and the average particle size of the basalt manufactured sand is 2.58 mm.

[0060] The water-reducing agent is a high-performance polycarboxylate-based water-reducing agent, CP1200, sourced from Shanghai Hengchuang Chemical Co., Ltd., China.

[0061] The cellulose ether is hydroxypropyl methylcellulose and hydroxyethyl methylcellulose in a mass ratio of 3.5:1.2.

[0062] The defoamer is silicone defoamer BYK-066N. The toughening agent is waterborne polyurethane dispersion emulsion PU-8249, manufactured by Shanghai Bolino New Materials.

[0063] The composite reinforcing agent is a combination of epoxy-functionalized acrylic polymer and phosphonate in a mass ratio of 4:1.

[0064] The epoxy-functionalized acrylic polymer is specifically Acronal® LR 9089, sourced from BASF, Germany. The phosphonate is specifically a combination of aminotrimethylenephosphonic acid and hydroxyethylidene diphosphonic acid in a mass ratio of 2:1.

[0065] A method for preparing high flexural strength road and bridge pavement cement includes the following steps: S1: All gel material, cellulose ether, aggregate and filler are put into a forced mixer and stirred at 40 rpm for 35 min until the material is uniformly mixed. Then, 70 wt% water, water-reducing agent and defoamer are pre-mixed and then slowly poured into the forced mixer. The speed is increased to 80 rpm and stirred for 10-15 min. S2: Reinforcing fiber is added and stirred for 15 min. At this time, the remaining 30 wt% water and combined reinforcing agent are mixed evenly and then added to the mixer and stirred for 12 min. After unloading, the material is allowed to stand and mature for 50 min. Before use, it is briefly re-stirred for 30-40 s to obtain the final product.

[0066] Example 2

[0067] The only difference between this embodiment and Embodiment 1 is as follows: A high flexural strength road and bridge pavement cement, by weight, comprises the following raw materials: 115 parts gel material, 55 parts filler material, 22 parts reinforcing fiber, 180 parts aggregate, 2.2 parts water-reducing agent, 1.2 parts cellulose ether, 0.5 parts defoamer, 15.8 parts combined reinforcing agent, and 78 parts water.

[0068] Example 3

[0069] The only difference between this embodiment and Embodiment 1 is as follows: A high flexural strength road and bridge pavement cement, by weight, comprises the following raw materials: 110 parts gel material, 55 parts filler material, 20 parts reinforcing fiber, 180 parts aggregate, 2.2 parts water-reducing agent, 1.2 parts cellulose ether, 0.5 parts defoamer, 12.5 parts combined reinforcing agent, and 70 parts water.

[0070] Comparative Example 1

[0071] The only difference between this comparative example and Example 1 is as follows: A high flexural strength road and bridge pavement cement, by weight, comprises the following raw materials: 120 parts gel material, 55 parts filler material, 12.5 parts reinforcing fiber, 180 parts aggregate, 2.2 parts water-reducing agent, 1.2 parts cellulose ether, 0.5 parts defoamer, 14.5 parts combined reinforcing agent, and 75 parts water.

[0072] All other implementation schemes are the same.

[0073] Comparative Example 2

[0074] The only difference between this comparative example and Example 1 is as follows: A high flexural strength road and bridge pavement cement, by weight, comprises the following raw materials: 120 parts gel material, 55 parts filler material, 25 parts reinforcing fiber, 180 parts aggregate, 2.2 parts water-reducing agent, 1.2 parts cellulose ether, 0.5 parts defoamer, 4.5 parts combined reinforcing agent, and 75 parts water.

[0075] All other implementation schemes are the same.

[0076] Comparative Example 3

[0077] The only difference between this comparative example and Example 1 is that the reinforcing fiber is a combination of hooked steel fiber and modified polypropylene coarse fiber in a mass ratio of 5:0.5.

[0078] All other implementation schemes are the same.

[0079] Comparative Example 4

[0080] The only difference between this comparative example and Example 1 is that the reinforcing fiber is a combination of hooked steel fiber and modified polypropylene coarse fiber in a mass ratio of 1:1.2.

[0081] All other implementation schemes are the same.

[0082] Comparative Example 5

[0083] The only difference between this comparative example and Example 1 is that the combined reinforcing agent is a combination of epoxy-functionalized acrylic polymer and phosphonate in a mass ratio of 8:1.

[0084] All other implementation schemes are the same.

[0085] Comparative Example 6

[0086] The only difference between this comparative example and Example 1 is that the combined reinforcing agent is a combination of epoxy-functionalized acrylic polymer and phosphonate in a mass ratio of 1:1.5.

[0087] All other implementation schemes are the same.

[0088] Performance Evaluation

[0089] 1. Flexural strength and compressive strength: The test was conducted in accordance with GB / T 17671-2021, and the average value of 10 tests was recorded in Table 1.

[0090] 2. Long-term freeze resistance: The test is conducted in accordance with GB / T 50082-2009. The relative dynamic modulus of elasticity before and after the test is taken, and the retention rate of the final relative dynamic modulus of elasticity is recorded. The average value of 10 tests is recorded in Table 1.

[0091] 3. Long-term resistance to chloride ion penetration: The test is conducted in accordance with GB / T 50082-2009. The electrical flux value is recorded over 6 hours, and the average value of 10 tests is recorded in Table 1.

[0092] 4. Abrasion resistance test: The test shall be conducted in accordance with GB / T 16925-1997. The average value of 10 tests shall be recorded in Table 1.

[0093] Table 1 Performance Evaluation Results

[0094]

[0095] The final performance test results of the examples and comparative examples show that the examples achieved superior test results compared to comparative examples 1-6. This is mainly because the limited composite reinforcing additive used in the examples of this application plays an efficient role in dispersion and plasticization. Furthermore, its active phosphonate groups, in the alkaline environment of cement stone, undergo a ring-opening reaction with the active epoxy groups on the epoxy functionalized polymer molecular chain, forming a strong covalent bond. This fundamentally solves the core problem of weak interfacial bonding between the organic and inorganic phases in traditional modified materials, thus achieving superior overall performance.

Claims

1. A high flexural road bridge pavement layer cement, characterized by: The raw materials include, in mass parts: 100-130 parts of gel material, 40-70 parts of filler material, 20-30 parts of reinforcing fiber, 120-240 parts of aggregate, 1.5-2.5 parts of water reducing agent, 0.5-2 parts of cellulose ether, 3-6 parts of toughening agent, 0.3-0.8 parts of defoaming agent, 10-20 parts of combined reinforcing agent, and 50-100 parts of water; The gel material is a combination of ordinary Portland cement and silica fume, with a mass ratio of (9-11):(2-3); The ordinary Portland cement is P.O 52.5 ordinary Portland cement or P.O 52.5R ordinary Portland cement; The reinforcing fiber is a combination of end-hook type steel fiber and modified polypropylene coarse fiber, with a mass ratio of (2-3):(0.5-1); The combined reinforcing agent is a combination of epoxy-functionalized acrylic polymer and phosphonate, with a mass ratio of (3.5-4.5):(1-1.2); The filler material is a combination of ground slag powder and ultra-fine fly ash, with a mass ratio of (2.5-3.5):(1.5-2).

2. The high flexural pavement layer cement of claim 1, wherein: The ground slag powder is S95 grade or S105 grade.

3. The high flexural pavement layer cement of claim 2, wherein: The average particle size D50 of the ultra-fine fly ash is ≤12 μm.

4. The high flexural pavement layer cement of claim 3, wherein: The average length of the end-hook type steel fiber is 30-40 mm, and the aspect ratio of the end-hook type steel fiber is 55-60.

5. The high flexural pavement layer cement of claim 4, wherein: The average length of the modified polypropylene coarse fiber is 40-50 mm, and the equivalent diameter of the modified polypropylene coarse fiber is 0.8-1 mm.

6. The high flexural pavement layer cement of claim 5, wherein: The aggregate is a combination of graded quartz sand and basalt machine-made sand, with a mass ratio of (12-14):(7-10).

7. The high flexural pavement layer cement of claim 6, wherein: The water reducing agent is polycarboxylic acid type or polycarboxylic acid amide type.

8. The high flexural pavement layer cement of claim 7, wherein: The cellulose ether is at least one of hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and methyl cellulose.

9. The high flexural pavement layer cement of claim 8, wherein: The toughening agent is at least one of butadiene-styrene latex epoxy-modified acrylic emulsion, water-based polyurethane dispersion emulsion, and butyronitrile latex.

10. A process for the preparation of a high flexural pavement layer cement according to any one of claims 1 to 9, characterized in that: Specifically comprising the following steps: S1: Put the gel material, cellulose ether, aggregate, and filler material into a forced mixer, stir at 30-50 rpm for 30-40 min until the materials are uniformly mixed, then pre-mix 70 wt% of water, water reducing agent, and defoaming agent, then slowly pour them into the forced mixer, increase the stirring speed to 60-80 rpm, and stir for 10-15 min; S2: add the reinforcing fiber and continue stirring for 10-15 min, at this time, mix the remaining 30 wt% of water with the combined reinforcing agent, then add them into the mixer and continue stirring for 10-15 min, after discharging, let the material stand for 50-60 min, and then perform a short stirring of 30-40 s before use.

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