Ecological pervious concrete and a method for preparing the same

Abstract

The application relates to the field of concrete, and discloses an ecological water-permeable concrete and a preparation method thereof. The ecological water-permeable concrete is prepared from the following raw materials in parts by mass: cement 68-85 parts; modified recycled coarse aggregate 150-200 parts; natural coarse aggregate 260-320 parts; waste tire rubber particles 4-8 parts; water 25-32 parts; water reducing agent 1-3 parts; and cellulose ether 0.5-1 part. The water-permeable concrete prepared by the application has excellent compressive strength and frost resistance, and is suitable for a sidewalk with a parking lot under a human load or a region with cold winters and large temperature differences.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete, in particular to an ecological pervious concrete and a preparation method thereof. BACKGROUND

[0002] At present, building a sponge city has become an effective way to realize sustainable development, and laying a pervious sidewalk in municipal roads, communities and squares can play an effective role. The pervious sidewalk is a new environmentally friendly and ecological type of road, which can quickly penetrate rainwater into the ground, effectively supplement groundwater, regulate ground problems, and alleviate heat island effect and urban waterlogging problems. At the same time, the pervious sidewalk can permeate the ground air, making the ground warm in winter and cool in summer, increasing comfort, and in addition, due to the high porosity of the pervious sidewalk, it can adsorb dust and also reduce noise.

[0003] The composition structure of the pervious sidewalk includes a surface layer, a leveling layer, a base layer, a cushion layer and a soil base, wherein the surface layer often uses pervious bricks, the leveling layer uses medium sand and dry hard cement mortar, the base layer uses pervious cement concrete, pervious cement stabilized gravel and pervious graded gravel, and the cushion layer uses natural gravel. The base layer plays the functions of mainly bearing load, permeating water and storing water, and needs to use pervious concrete.

[0004] Pervious concrete is essentially a building material mixed by aggregate, cementitious material, water and additives, mainly composed of coarse aggregate, paste and void, and the strength is mainly relied on the hardened cementitious material wrapped around the aggregate to bond the aggregate. The traditional pervious concrete has high water permeability coefficient, but the porous structure leads to poor compressive strength and frost resistance of the pervious concrete. When facing the demand of pedestrian sidewalk with crowd load and parking or in the region with cold winter and large temperature difference, the traditional pervious concrete cannot meet the use demand. SUMMARY

[0005] In order to improve the compressive strength and frost resistance of the pervious concrete, adapt to the pedestrian sidewalk with crowd load and parking or in the region with cold winter and large temperature difference, the present application provides an ecological pervious concrete and a preparation method thereof.

[0006] The ecological pervious concrete and the preparation method thereof provided by the present application adopt the following technical scheme:

[0007] In a first aspect, the present application provides an ecological pervious concrete made of the following mass parts of raw materials:

[0008] 68-85 parts of cement;

[0009] 150-200 parts of modified recycled coarse aggregate;

[0010] 260-320 parts of natural coarse aggregate;

[0011] Waste tire rubber particles 4-8 parts;

[0012] Water 25-32 parts;

[0013] Water reducing agent 1-3 parts;

[0014] Cellulose ether 0.5-1 parts.

[0015] By adopting the above technical scheme, fine aggregate is not added, and part of the modified recycled coarse aggregate is selected to replace natural coarse aggregate. The modified recycled coarse aggregate has a large porosity and a high water permeability coefficient, and the structural strength is improved through modification. The waste tire rubber particles can slow down the development of concrete cracks during the freeze-thaw cycle, effectively improving the frost resistance of the pervious concrete. The combination of waste tire rubber and modified recycled coarse aggregate saves energy and meets the green ecological concept. The cellulose ether has a retarding effect, so that the modified recycled coarse aggregate does not immediately hydrate and set, providing a relatively stable reaction environment for early hydration inside the recycled coarse aggregate. At the same time, it can improve the bonding degree of the aggregate and cement particles and waste tire rubber particles, improve the degree of hydration and crosslinking, and be beneficial to the improvement of the compressive strength of the pervious concrete. Through the synergy of various components, the pervious concrete has excellent compressive strength and frost resistance, and is suitable for pedestrian sidewalks with parking loads or areas with cold winters and large temperature differences.

[0016] Optionally, the preparation method of the modified recycled coarse aggregate is:

[0017] The waste concrete is crushed, washed and sieved to obtain recycled coarse aggregate;

[0018] A cement slurry is prepared using cement, water, PP wood-plastic particles and metakaolin, wherein the mass ratio of cement, water, PP wood-plastic particles and metakaolin is (80-88):100:(1.8-3):(4-9);

[0019] The recycled coarse aggregate is poured into the cement slurry, ensuring that the liquid level is higher than the recycled coarse aggregate, and stirring and soaking for 2-3 hours. The recycled coarse aggregate is taken out, sieved and naturally dried for standby, to obtain the modified recycled coarse aggregate.

[0020] By adopting the above technical scheme, the recycled coarse aggregate is treated and modified by using the cement mortar containing PP wood-plastic particles and metakaolin. The PP wood-plastic particles and metakaolin fill the voids in the recycled coarse aggregate along with the cement mortar, reducing the porosity and gas content in the voids of the recycled coarse aggregate and improving the compressive strength.

[0021] PP wood-plastic particles are made of thermoplastic and plant fibers such as wood powder, rice husk and bamboo powder, which can support the pores; metakaolin as a mineral admixture can change the interface transition zone of recycled concrete, and through the crosslinking of the two and the gel product of cement hydration, it is beneficial to improve the compressive strength and chloride ion resistance of pervious concrete and reduce the expansion of cracks.

[0022] Optionally, the waste tire rubber particles are sulfonated modified waste tire rubber particles prepared by the following steps:

[0023] The waste tire rubber particles are soaked in 1 mol / L sodium hydroxide solution for 22-24 h, washed with distilled water until neutral, and dried;

[0024] The dried waste tire rubber particles and hydrogen peroxide are placed in a reactor and oxidized in a constant temperature water bath at 50-53℃, and the pH is controlled at 5.0-5.5 with dilute sulfuric acid. After oxidation, wash until neutral and dry;

[0025] The dried waste tire rubber particles are added to a constant temperature saturated sodium sulfite solution at 60-65℃, and sulfonated for 2-2.5 h, washed until neutral, and dried to obtain sulfonated modified waste tire rubber particles.

[0026] By using the above technical solution, sodium hydroxide is used to remove impurities such as zinc stearate on the surface of the waste tire rubber particles, and then through the processes of oxidation and sulfonation, hydrophilic groups such as sulfonic acid groups are introduced into the waste tire rubber particles, thereby enhancing the compatibility and bonding strength of the waste tire rubber particles with the cement matrix, and improving the compressive strength of the pervious concrete.

[0027] Optionally, the particle size of the waste tire rubber particles is 5-8 mm.

[0028] By using the above technical solution, when 5-8 mm waste tire rubber particles are selected, the influence on the water permeability coefficient of the pervious concrete is small, and the porosity and water permeability coefficient can still be maintained.

[0029] Optionally, the cement slurry further comprises silane coupling agent KH-570, and the mass ratio of silane coupling agent KH-570 to water in the cement slurry is (0.8-1.5):100.

[0030] By using the above technical solution, the addition of silane coupling agent is beneficial to enhancing the dispersibility of PP wood-plastic particles and metakaolin in the cement slurry, improving the modification effect on the recycled coarse aggregate, and improving the stability of the modified recycled coarse aggregate.

[0031] Optionally, the natural coarse aggregate is selected from crushed stone with a particle size range of 8-10 mm, and the modified recycled coarse aggregate has a particle size range of 5-10 mm.

[0032] Optionally, the cement used is silicate cement with a strength grade of not less than 42.5 MPa.

[0033] Optionally, the water-reducing agent is a polycarboxylate water-reducing agent or a naphthalene-based high-efficiency water-reducing agent.

[0034] Optionally, the particle size of the PP wood-plastic granules is 2-4 mm.

[0035] Secondly, this application provides a method for preparing ecological permeable concrete, used in the aforementioned ecological permeable concrete, comprising the following steps:

[0036] Add water-reducing agent and cellulose ether to water, stir and mix to obtain a mixture;

[0037] Modified recycled coarse aggregate, natural coarse aggregate, waste tire rubber granules, and cement are added to a mixing tank in sequence, and the mixture is added while stirring. Ecological permeable concrete can be obtained by stirring.

[0038] By adopting the above technical solution, water-reducing agent, cellulose ether, and water are first mixed, and then other gelling materials and aggregates are added to obtain ecological permeable concrete with high compressive strength and high frost resistance.

[0039] In summary, this application has the following beneficial effects:

[0040] No fine aggregate was added; modified recycled coarse aggregate was used to replace some of the natural coarse aggregate. This modified recycled coarse aggregate has a higher porosity and permeability coefficient, which improves the structural strength through modification. Waste tire rubber granules slow down the development of concrete cracks during freeze-thaw cycles, effectively improving the frost resistance of permeable concrete. The combination of waste tire rubber and modified recycled coarse aggregate saves energy and aligns with green ecological principles. Cellulose ether acts as a retarder, preventing the modified recycled coarse aggregate from immediately hydrating and setting, providing a relatively stable reaction environment for early hydration within the recycled coarse aggregate. It also improves the bonding between the aggregate and cement particles and waste tire rubber granules, increasing the degree of hydration cross-linking and contributing to the improved compressive strength of permeable concrete. Through the synergistic effect of these components, permeable concrete exhibits excellent compressive strength and frost resistance, making it suitable for pedestrian walkways with pedestrian loads and parking areas, or areas with cold winters and large temperature differences. Detailed Implementation

[0041] The present application will be further described in detail below with reference to Examples 1-10 and Comparative Examples 1-3.

[0042] The waste concrete came from a building demolition site;

[0043] The waste tire rubber granules came from a waste rubber recycling and processing plant, with a particle size of 5-8mm.

[0044] Cellulose ethers were selected from Shanghai Kaiyin Chemical Co., Ltd.;

[0045] The cement used is PO.42.5 grade Portland cement;

[0046] Natural coarse aggregate is selected from crushed stone with a particle size range of 8-10mm;

[0047] The polycarboxylate superplasticizer, model HX-YZJ01, was purchased from Wuhan Huaxuan High-Tech Co., Ltd.

[0048] The naphthalene-based water-reducing agent, type XTY-042, was purchased from Shandong Xintengyue Chemical Co., Ltd.

[0049] The PP wood-plastic granules were purchased from Dongguan Yucheng Plastic Co., Ltd., with a particle size of 2-4mm.

[0050] Preparation Example

[0051] Preparation Example 1

[0052] Preparation of modified recycled coarse aggregate

[0053] The steel bars in the waste concrete are removed, and the concrete is crushed using a jaw crusher. The crushed pieces are then washed with water in an ultrasonic cleaner for 1 hour. The aggregate with a particle size of 3-7 mm is then screened out to obtain recycled coarse aggregate.

[0054] Put 100kg of water, 80kg of cement, 1.8kg of PP wood-plastic granules and 4kg of metakaolin into a mixing bucket, stir and disperse for 20 minutes to obtain cement slurry;

[0055] Pour 50 kg of recycled coarse aggregate into the cement slurry, ensuring that the liquid level is higher than the recycled coarse aggregate. Stir and soak for 2 hours. Take out the recycled coarse aggregate and sieve it to remove the detached solidified mortar. Let it air dry naturally for later use to obtain modified recycled coarse aggregate.

[0056] The particle size range of the modified recycled coarse aggregate is 5-10 mm.

[0057] Preparation Examples 2-4

[0058] The preparation of modified recycled coarse aggregate differs from that of Preparation Example 1 in that the raw material parameters and reaction time are different, as shown in Table 1.

[0059] Table 1

[0060]

[0061]

[0062] Preparation Example 5

[0063] Preparation of modified recycled coarse aggregate

[0064] The difference between this preparation example and Preparation Example 1 is that 0.8 kg of silane coupling agent KH-570 is further added in the cement slurry.

[0065] Preparation Example 6

[0066] Preparation of modified recycled coarse aggregate

[0067] The difference between this preparation example and Preparation Example 1 is that 1.5 kg of silane coupling agent KH-570 is further added in the cement slurry.

[0068] Preparation Example 7

[0069] Preparation of sulfonated modified waste tire rubber particles

[0070] The waste tire rubber particles are soaked in 1 mol / L sodium hydroxide solution for 22 h, washed with distilled water to neutral, and dried;

[0071] The dried waste tire rubber particles and hydrogen peroxide are placed in a reactor, and oxidation is carried out in a 50°C constant temperature water bath, with dilute sulfuric acid being used to control pH = 5.0. After oxidation is completed, washing is carried out to neutral, and drying is carried out.

[0072] The dried waste tire rubber particles are added to a constant temperature saturated sodium sulfite solution at 60°C, and sulfonation reaction is carried out for 2 h. Washing to neutral and drying obtain sulfonated modified waste tire rubber particles.

[0073] Preparation Example 8

[0074] The waste tire rubber particles are soaked in 1 mol / L sodium hydroxide solution for 24 h, washed with distilled water to neutral, and dried;

[0075] The dried waste tire rubber particles and hydrogen peroxide are placed in a reactor, and oxidation is carried out in a 53°C constant temperature water bath, with dilute sulfuric acid being used to control pH = 5.5. After oxidation is completed, washing is carried out to neutral, and drying is carried out.

[0076] The dried waste tire rubber particles are added to a constant temperature saturated sodium sulfite solution at 65°C, and sulfonation reaction is carried out for 2.5 h. Washing to neutral and drying obtain sulfonated modified waste tire rubber particles.

[0077] Example

[0078] Example 1

[0079] Preparation of ecological permeable concrete

[0080] 0.1 kg polycarboxylate superplasticizer, 0.05 kg cellulose ether were added into 2.5 kg water, and stirred and mixed for 1 min to obtain a mixed solution;

[0081] 15 kg of the modified recycled coarse aggregate prepared in Preparation Example 1, 26 kg of natural coarse aggregate, 0.4 kg of waste tire rubber particles and 6.8 kg of cement were sequentially added into a stirring kettle, and the mixed solution was added while stirring, and stirred for 6 min to obtain the ecological permeable concrete.

[0082] Examples 2-4

[0083] Examples 2-4 are different from Example 1 in that the raw materials, raw material parameters and reaction time are different, as shown in Table 2.

[0084] Table 2

[0085]

[0086]

[0087] Example 5

[0088] This example is different from Example 1 in that the modified recycled coarse aggregate in this example is the modified recycled coarse aggregate prepared in Preparation Example 5.

[0089] Example 6

[0090] This example is different from Example 1 in that the modified recycled coarse aggregate in this example is the modified recycled coarse aggregate prepared in Preparation Example 6.

[0091] Example 7

[0092] This example is different from Example 1 in that the waste tire rubber particles in this example are the sulfonated modified waste tire rubber particles prepared in Preparation Example 7.

[0093] Example 8

[0094] This example is different from Example 1 in that the waste tire rubber particles in this example are the sulfonated modified waste tire rubber particles prepared in Preparation Example 8.

[0095] Example 9

[0096] This example is different from Example 1 in that the modified recycled coarse aggregate in this example is the modified recycled coarse aggregate prepared in Preparation Example 6; and the waste tire rubber particles in this example are the sulfonated modified waste tire rubber particles prepared in Preparation Example 8.

[0097] Example 10

[0098] The difference between this embodiment and Example 1 is that the modified recycled coarse aggregate in this embodiment is the modified recycled coarse aggregate obtained in Preparation Example 5; and the waste tire rubber granules in this embodiment are the sulfonated modified waste tire rubber granules obtained in Preparation Example 7.

[0099] Comparative Example

[0100] Comparative Example 1

[0101] The difference between this comparative example and Example 1 is that 15 kg of recycled coarse aggregate was used instead of 15 kg of the modified recycled coarse aggregate prepared in Example 1 in the raw materials of this comparative example.

[0102] Comparative Example 2

[0103] The difference between this comparative example and Example 1 is that 0.4 kg of waste tire rubber particles were not added to the raw materials of this comparative example.

[0104] Comparative Example 3

[0105] The difference between this comparative example and Example 1 is that in the preparation step of the modified recycled coarse aggregate in this comparative example, the cement slurry is prepared by mixing 100kg of water and 80kg of cement, and does not contain PP wood-plastic particles and metakaolin.

[0106] Performance testing

[0107] The permeable ecological concrete prepared in Examples 1-10 and Comparative Examples 1-3 were made into specimens. The compressive strength, permeability coefficient and freeze-thaw resistance of each specimen were tested, and the test results are recorded in Table 3.

[0108] Compressive strength: tested according to GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete"; Permeability coefficient: tested according to the provisions of GB / T25993-2010 "Permeable Paving Bricks and Permeable Paving Panels" for permeable concrete;

[0109] Freeze-thaw resistance: Tested according to ASTM / C666, "Standard Test Method for Rapid Freeze-Thaw Resistance of Concrete".

[0110] Table 3

[0111]

[0112]

[0113] According to Table 3, the water permeability coefficient of the ecological pervious concrete prepared in the application is > 2 mm / s, the compressive strength of the ecological pervious concrete prepared in the application is > 20 MPa after 28 d curing, and the water absorption of the modified recycled coarse aggregate is < 8%, and the effective porosity is > 15%, which meets the design standard of the pervious cement concrete of the pervious sidewalk base. The ecological pervious concrete of the application has high compressive strength and good frost resistance, and is thus suitable for the sidewalk with human load and parking or the area with cold winter and large temperature difference.

[0114] Example 4-5 is improved compared with Example 1, and the modified recycled coarse aggregate in the raw material component is improved, and the silane coupling agent KH-570 is added in the modified cement slurry, which promotes the dispersion of the PP wood-plastic particles and the metakaolin in the cement slurry, and improves the filling performance of the PP wood-plastic particles and the metakaolin to the recycled coarse aggregate, thereby promoting the improvement of the compressive strength of the concrete.

[0115] Example 6-7 is improved compared with Example 1, and the waste tire rubber particles in the raw material component are modified, and the hydrophilic groups are introduced into the waste tire rubber particles through oxidation-sulfonation, which enhances the compatibility and bonding strength of the cement matrix, and plays a partial crosslinking filling role, so that the compressive strength and frost resistance are improved.

[0116] Comparative Example 1 is improved compared with Example 1, and the unmodified recycled coarse aggregate is selected, the compressive strength of the recycled coarse aggregate is low, the water permeability coefficient is high, and the load of the sidewalk cannot be borne.

[0117] Comparative Example 2 is improved compared with Example 1, and the waste ceramic rubber particles are not added in the raw material component, and the frost resistance of the prepared pervious concrete is poor, and the use requirement in the area with cold winter and large temperature difference cannot be met.

[0118] Comparative Example 3 is improved compared with Example 1, and the PP wood-plastic particles and the metakaolin are not added in the cement slurry for modifying the recycled coarse aggregate, and the pure cement slurry is used, the filling property of the recycled coarse aggregate is reduced, and the compressive strength of the ecological concrete is reduced.

[0119] The specific embodiment is only an explanation of the application, and is not a limitation of the application, and the person skilled in the art can make modifications to the specific embodiment without creative contribution according to the needs after reading the specification, but as long as the application is within the scope of the claims, it is protected by the patent law.

Claims

1. An ecological permeable concrete, characterized in that, Made from the following parts by weight of raw materials: 68-85 parts cement; 150-200 parts of modified recycled coarse aggregate; 260-320 parts of natural coarse aggregate; 4-8 parts of waste tire rubber granules; 25-32 parts water; 1-3 parts water-reducing agent; 0.5-1 part of cellulose ether; The method for preparing the modified recycled coarse aggregate is as follows: Waste concrete is crushed, washed, and screened to obtain recycled coarse aggregate. Cement slurry is prepared using cement, water, PP wood-plastic granules, and metakaolin. The mass ratio of cement, water, PP wood-plastic granules, and metakaolin is (80-88):100:(1.8-3):(4-9). PP wood-plastic granules are made by mixing thermoplastic plastics with wood flour, rice husks, and bamboo flour. Pour the recycled coarse aggregate into the cement slurry, ensuring that the liquid level is higher than the recycled coarse aggregate. Stir and soak for 2-3 hours. Remove the recycled coarse aggregate, sieve it, and let it air dry naturally for later use to obtain the modified recycled coarse aggregate. The waste tire rubber granules are sulfonated modified waste tire rubber granules, which are prepared through the following steps: Soak waste tire rubber granules in a 1 mol / L sodium hydroxide solution for 22-24 hours, wash with distilled water until neutral, and then dry. The dried waste tire rubber granules and hydrogen peroxide are placed in a reactor and oxidized in a constant temperature water bath at 50-53℃. The pH is controlled at 5.0-5.5 with dilute sulfuric acid. After oxidation, the mixture is washed until neutral and then dried. The dried waste tire rubber granules were added to a constant-temperature saturated sodium sulfite solution at 60-65℃ and sulfonated for 2-2.5 hours. After washing until neutral, the sulfonated modified waste tire rubber granules were obtained.

2. The ecological permeable concrete according to claim 1, characterized in that: The particle size of the waste tire rubber granules is 5-8mm.

3. The ecological permeable concrete according to claim 1, characterized in that: The cement slurry also contains silane coupling agent KH-570, and the mass ratio of silane coupling agent KH-570 to water in the cement slurry is (0.8-1.5):

100.

4. The ecological permeable concrete according to claim 1, characterized in that: The natural coarse aggregate is selected from crushed stone with a particle size range of 8-10 mm, and the modified recycled coarse aggregate has a particle size range of 5-10 mm.

5. The ecological permeable concrete according to claim 1, characterized in that: The cement used is silicate cement with a strength grade of not less than 42.5 MPa.

6. The ecological permeable concrete according to claim 1, characterized in that: The water-reducing agent is either a polycarboxylate water-reducing agent or a naphthalene-based high-efficiency water-reducing agent.

7. The ecological permeable concrete according to claim 1, characterized in that: The particle size of the PP wood-plastic granules is 2-4 mm.

8. A method for preparing ecological permeable concrete, characterized in that, The method for preparing an ecological permeable concrete according to any one of claims 1-7 includes the following steps: Add water-reducing agent and cellulose ether to water, stir and mix to obtain a mixture; Modified recycled coarse aggregate, natural coarse aggregate, waste tire rubber granules, and cement are added to a mixing tank in sequence, and the mixture is added while stirring. Ecological permeable concrete can be obtained by stirring.

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