Full-lime-hua aggregate pervious concrete and preparation method thereof

Abstract

The application discloses a kind of whole loess aggregate water permeable concrete, the water permeable concrete is prepared from the following weight parts of raw materials: water 55.125~134.2 parts, cement 248.063~670.8 parts, water reducing agent 2.45~5.96267 parts, silica ash 30.625~74.5334 parts, cement substitute 27.5625~268.32 parts, loess aggregate: 1225 parts, and the cement substitute is desert sand or glass powder.The application first uses 100% loess broken aggregate (particle size 3-5 mm or particle size 10-15 mm) as the only aggregate, completely discards natural aggregate, realizes the full resource utilization of a large amount of waste stone generated in the process of loess mining and processing, and greatly reduces the mining of natural aggregate and the damage to the ecological environment.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to a permeable concrete made entirely of travertine aggregate and its preparation method. Background Technology

[0002] Permeable concrete, as an eco-friendly building material that can effectively reduce urban surface runoff and replenish groundwater, is widely used in sponge city construction. Traditional permeable concrete uses natural crushed stone (such as basalt, granite, and limestone) as aggregate and ordinary Portland cement as binder. However, the mining of natural aggregates damages the ecological environment, and cement production emits large amounts of CO2. Therefore, utilizing industrial waste and construction waste to replace natural aggregates and cement has become an important research direction in the field of permeable concrete.

[0003] Travertine is a porous carbonate rock, and its mining and processing generate a large amount of waste rock. Previous research has shown that crushed travertine aggregate can be used to prepare lightweight permeable concrete. For example, the applicant's previously granted invention patent (ZL 2024 1 0106734.1) discloses a travertine permeable concrete mixed with powdered waste and its preparation method, in which travertine aggregate partially replaces limestone aggregate (replacement rate 25%), and travertine powder and limestone powder replace a small amount of cement. Although this technology achieves partial utilization of travertine waste, it still has the following shortcomings: First, natural aggregate (limestone) still accounts for more than 75% of the total aggregate, failing to eliminate dependence on natural aggregate; second, the powdered waste replacing cement is limited to carbonate fine powder, and the replacement content does not exceed 20%, without evaluating the situation of high-content travertine powder and limestone powder. Furthermore, the application of high-content desert sand and waste glass powder as substitutes for cementitious materials in permeable concrete is not addressed.

[0004] Desert sand is a type of natural fine-grained sand widely distributed in desert regions. With the development of desertification control and engineering construction in wind-blown sand areas, large quantities of desert sand need to be transported or disposed of, making its resource utilization a new research topic. Currently, the application of desert sand in building materials mainly focuses on two aspects: firstly, as a partial replacement of river sand as fine aggregate in the preparation of mortar or concrete; and secondly, as roadbed filler. However, using desert sand directly as a cement substitute in permeable concrete faces the following technical challenges: (1) Desert sand has extremely fine particle size, large specific surface area, and high water demand. Under a fixed water-cement ratio, it will significantly reduce the fluidity of the cement paste, making it difficult for the paste to uniformly coat the aggregate particles, resulting in a "sticky bottom" or "dry" phenomenon; (2) The volcanic ash activity of desert sand is extremely low. At room temperature, it is difficult to undergo a secondary hydration reaction with the cement hydration product Ca(OH)2, and it only plays the role of micro-aggregate filling. Excessive substitution of cement will lead to a significant decrease in bonding strength; (3) When the aggregate system uses 100% travertine waste aggregate (instead of traditional natural aggregate), travertine aggregate itself has the characteristics of low strength and rough, porous surface, which places higher demands on the bonding performance of the paste. At present, there is no permeable concrete technical solution that simultaneously meets the two conditions of "100% travertine aggregate replacing natural aggregate" and "desert sand replacing part of the cement".

[0005] Waste glass is another type of waste generated in huge quantities. The glass powder obtained after grinding it contains a large amount of amorphous SiO2, which has potential pozzolanic activity. Currently, research on the application of glass powder in concrete mainly focuses on ordinary concrete, with very few reports on its application in permeable concrete. When attempting to use glass powder as a cement substitute in permeable concrete with 100% travertine aggregate, a series of unique technical challenges arise: (1) Glass powder particles have smooth, angular surfaces and high water content, which can lead to decreased slurry fluidity and difficulty in uniformly coating aggregates after replacing cement; (2) The active SiO2 in glass powder may undergo alkali-silica reaction (ASR) in the alkaline environment of cement hydration, causing later expansion and cracking of concrete. Travertine aggregate itself is carbonate rock, and its alkaline environment may further exacerbate this risk; (3) When using travertine aggregate with a larger particle size (10-15 mm), the porosity between aggregates increases, requiring higher bonding strength and dosage of cementitious materials; (4) The ratio of aggregate to cementitious material (bone-to-cement ratio) is a key parameter affecting the skeleton structure and performance of permeable concrete. However, existing studies have not found any optimization reports on permeable concrete under the "all-travertine aggregate + glass powder replacing cement" system or on evaluating the performance effects of different bone-to-cement ratios (such as 2, 2.5, 3, 4).

[0006] Therefore, overcoming the degradation of paste properties (such as loss of fluidity, decreased workability, and reduced cementitious strength) caused by replacing cement with desert sand or glass powder, and achieving effective matching with the all-travertine aggregate system to prepare permeable concrete that meets the requirements of CJJ / T135-2009, while systematically evaluating the impact of reduced cement content on the comprehensive performance of all-travertine aggregate permeable concrete, has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] Purpose of the Invention: The purpose of this invention is to provide a permeable concrete made entirely of travertine aggregate and its preparation method, in order to solve the technical problems in existing permeable concrete technology, such as low natural aggregate substitution rate (difficult to achieve 100% substitution) and loss of slurry fluidity and insufficient bonding strength caused by excessively fine particle size, high water demand, and low activity when using high-content desert sand, glass powder, travertine powder, and limestone powder (up to 40%) as cement substitutes. Under the premise of ensuring that the mechanical properties and permeability of permeable concrete meet the specifications, this invention achieves full utilization of travertine aggregate and resource utilization of waste.

[0008] Technical solution: The permeable concrete of the present invention is prepared from the following raw materials in parts by weight: water 55.125~134.2 parts, cement 248.063~670.8 parts, water-reducing agent 2.45~5.96267 parts, silica fume 30.625~74.5334 parts, cement substitute 27.5625~268.32 parts, travertine aggregate 1225 parts, and the cement substitute is desert sand or glass powder.

[0009] Preferably, the permeable concrete is prepared from the following raw materials in parts by weight: water 98.16~134.16 parts, cement 402.48~670.8 parts, silica fume 54.5334~74.5334 parts, water-reducing agent 4.36268~5.96267 parts, desert sand 67.08~268.32 parts, and travertine aggregate 1225 parts.

[0010] The desert sand is natural desert fine sand with a particle size of less than 250 μm; the travertine aggregate has a particle size of 3 to 5 mm.

[0011] In the aforementioned technical solution, desert sand is directly used as a cement substitute in permeable concrete. This involves replacing cement with desert sand (particle size <250 μm) at a ratio of 0-40% by mass, which not only reduces cement usage and CO2 emissions but also opens up new avenues for the large-scale resource utilization of desert sand. While travertine aggregate is characterized by low strength and a rough, porous surface, desert sand has disadvantages such as extremely fine particle size, high water demand, and low pozzolanic activity. Using both together leads to loss of paste fluidity, weak aggregate-paste interface bonding, and a significant decrease in concrete strength. The above technical solution successfully solved the above problems through the synergistic effect of the following technical means: fixing a low water-cement ratio (0.18) and strictly controlling the amount of water used; adding silica fume (54.5~74.5 parts) to compensate for the loss of cementitious activity after desert sand replaces cement by utilizing its high pozzolanic activity and micro-aggregate filling effect, and strengthening the interface transition zone; adopting the cement-coated stone method (step-by-step mixing process) to make the slurry preferentially and uniformly coat the surface of the aggregate, avoiding the agglomeration of desert sand; optimizing the aggregate particle size (3-5 mm single gradation) to form a stable skeleton structure and ensure unobstructed water permeability channels.

[0012] In the above technical solution, using desert sand directly as a cement substitute for permeable concrete has significant environmental benefits. Specifically, it eliminates solid waste: each cubic meter of concrete can eliminate approximately 1225 kg (about 0.5 tons) of travertine waste aggregate, while simultaneously eliminating 0-268 kg of desert sand; it reduces carbon emissions: based on replacing 30% of cement with desert sand, each cubic meter of concrete can reduce cement usage by approximately 80 kg, correspondingly reducing CO2 emissions by approximately 60 kg (estimated at 0.75 tons of CO2 emissions per ton of cement); and it protects natural resources: it reduces the mining of natural crushed stone aggregate, protecting the ecological environment of riverbeds and mountains.

[0013] Preferably, the permeable concrete is prepared from the following raw materials in parts by weight: water 55.125~110.25 parts, cement 248.063~551.25 parts, silica fume 30.625~61.25 parts, glass powder 27.5625~220.5 parts, water-reducing agent 2.45~4.9 parts, and travertine aggregate 1225 parts.

[0014] The glass powder has a particle size of less than 250 μm, and the travertine aggregate has a particle size of 10~15 mm.

[0015] The cement is silicate cement, and the water-reducing agent is BASF high-efficiency water-reducing agent. The silica fume is a mineral admixture with a specific surface area ≥15000 m² / kg and a SiO2 content ≥85%.

[0016] This invention provides a method for preparing permeable concrete using all-travertine aggregate, which employs a cement-coated aggregate method to prepare the permeable concrete.

[0017] The preparation method includes the following steps:

[0018] (1) Mix all the travertine aggregate to make the aggregate evenly dispersed;

[0019] (2) Add half the amount of water-reducing agent and half the amount of water to the travertine aggregate obtained in step (1), stir, and make the surface of the aggregate evenly wet;

[0020] (3) Add cementitious materials to the travertine aggregate obtained in step (2). The cementitious materials include cement, silica fume and cement substitutes. Stir to make the cementitious materials evenly coat the surface of the aggregate to obtain a mixture.

[0021] (4) Add the remaining half of the water and half of the water-reducing agent to the mixture obtained in step (3), stir, so that the slurry is fully dispersed and evenly coats the aggregate to obtain freshly mixed permeable concrete;

[0022] (5) After molding, initial curing, demolding and curing, the freshly mixed permeable concrete is obtained as described in the whole travertine aggregate permeable concrete.

[0023] In step (5), the freshly mixed permeable concrete is put into a mold that has been pre-coated with release oil, vibrated to compact it, and the surface is smoothed. It is then left to stand at room temperature to complete the molding and initial curing. The permeable concrete is then demolded and placed in a water tank for curing to complete the demolding and curing.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0025] (1) Achieved 100% replacement of natural aggregate with travertine waste aggregate: In existing permeable concrete technology, travertine aggregate can only replace 25% to 30% of natural aggregate (such as limestone), with the remainder still relying on natural crushed stone. This invention is the first to use 100% travertine crushed aggregate (particle size 3-5 mm or 10-15 mm) as the sole aggregate, completely eliminating natural aggregate, and realizing the full resource utilization of the large amount of waste stone generated during travertine mining and processing, greatly reducing the mining of natural aggregate and the damage to the ecological environment.

[0026] (2) The product exhibits excellent mechanical and permeability properties, meeting the specifications: Tests show that the permeable concrete (7 mix proportions) prepared using all travertine aggregate and waste materials to replace cement prepared according to this invention all meet the requirements of CJJ / T 135-2009 "Technical Specification for Permeable Cement Concrete Pavement". Specific performance characteristics are as follows:

[0027] (3) The process is simple, the cost is low, and it is suitable for industrial production: The raw materials used in this invention (travertine waste stone, desert sand, glass powder, travertine powder, limestone powder, 42.5 ordinary silicate cement, silica fume, BASF water-reducing agent) are all common materials with wide sources and controllable costs. The preparation process is a conventional concrete mixing process (cement-coated stone method), which does not require special equipment and is easy to promote and implement in existing concrete mixing plants. Detailed Implementation

[0028] Example 1

[0029] The permeable concrete with all travertine aggregate in this embodiment is prepared from the following raw materials in parts by weight: 603.72 parts cement, 134.16 parts water, 74.5334 parts silica fume, 67.08 parts desert sand, 5.96267 parts water-reducing agent, and 1225 parts travertine. The travertine aggregate is the granules obtained after crushing travertine waste rock, and the travertine particle size is 3-5 mm.

[0030] The desert sand is natural fine desert sand with a particle size of less than 250 μm and a density of 2650 kg / m³. 3 .

[0031] The cement is ordinary Portland cement with a strength grade of 42.5 and a density of 3110 kg / m³. 3 .

[0032] The water-reducing agent is BASF's SKY 8860 high-efficiency water-reducing agent, with a water reduction rate of approximately 20%.

[0033] The silica fume is a mineral admixture with a specific surface area ≥15000 m² / kg and a SiO2 content ≥85%.

[0034] The permeable concrete made entirely of travertine aggregate in this embodiment is prepared using the cement-coated aggregate method (or "two-stage feeding method"), and the specific steps are as follows:

[0035] (1) Aggregate pretreatment: Weigh the travertine aggregate with a particle size of 3-5 mm according to the proportion and set aside.

[0036] (2) First mixing: Pour all the travertine aggregate into a forced mixer and dry mix for 60 seconds to make the aggregate evenly dispersed.

[0037] (3) Second mixing (half water and water-reducing agent): Add half the amount of water-reducing agent and half the amount of water, and continue mixing for 90 seconds to make the surface of the aggregate evenly wet.

[0038] (4) Third mixing (adding cementitious materials): Add cement, silica fume and desert sand, and continue mixing for 90 seconds to make the cementitious materials evenly coat the surface of the aggregate.

[0039] (5) Fourth mixing (remaining water and water-reducing agent): Add the remaining half of the water and half of the water-reducing agent, and continue mixing for 90 seconds to fully disperse the slurry and evenly coat the aggregate to obtain freshly mixed permeable concrete.

[0040] (6) Molding and initial curing: Pour the mixed concrete into a mold that has been coated with release oil, gently vibrate to compact it, smooth the surface, and let it stand at room temperature for 24 hours.

[0041] (7) Demolding and curing: Demold the sample after 24 hours, mark the sample, and immediately put it into the water tank for curing for 27 days (total curing period of 28 days). The curing water temperature is 20±2℃.

[0042] (8) Performance testing: After curing, the compressive strength, porosity, and permeability coefficient of the specimens shall be tested in accordance with the methods specified in the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081-2019) and the "Technical Specification for Permeable Cement Concrete Pavement" (CJJ / T 135-2009). Three parallel specimens shall be prepared for each mix proportion, and the arithmetic mean shall be taken as the test result.

[0043] Unless otherwise stated, the raw material specifications used in the following examples and comparative examples are the same as those in Example 1.

[0044] Example 2

[0045] The permeable concrete with all travertine aggregate in this embodiment is prepared from the following raw materials in parts by weight: 536.64 parts cement, 134.16 parts water, 74.5334 parts silica fume, 134.16 parts desert sand, 5.96267 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size is 3-5 mm.

[0046] In this embodiment, the preparation method of the permeable concrete made entirely of travertine aggregate is the same as that described in Example 1.

[0047] Example 3

[0048] The permeable concrete made entirely of travertine aggregate in this embodiment is prepared from the following raw materials in parts by weight: 469.56 parts cement, 134.16 parts water, 74.5334 parts silica fume, 201.24 parts desert sand, 5.96267 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size is 3-5 mm.

[0049] In this embodiment, the preparation method of the permeable concrete made entirely of travertine aggregate is the same as that described in Example 1.

[0050] Example 4

[0051] The permeable concrete made entirely of travertine aggregate in this embodiment is prepared from the following raw materials in parts by weight: 402.48 parts cement, 134.16 parts water, 74.5334 parts silica fume, 268.32 parts desert sand, 5.96267 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size is 3-5 mm.

[0052] In this embodiment, the preparation method of the permeable concrete made entirely of travertine aggregate is the same as that described in Example 1.

[0053] Comparative Example 1

[0054] The concrete in this comparative example was prepared from the following raw materials in parts by weight: 670.8 parts cement, 134.16 parts water, 74.5334 parts silica fume, 0 parts desert sand, 5.96267 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size was 3-5 mm.

[0055] In the preparation method of this comparative example, the raw materials do not contain desert sand, and the remaining steps are exactly the same as in Example 1.

[0056] Comparative Example 2

[0057] The concrete in this comparative example was prepared from the following raw materials in parts by weight: 580.801 parts cement, 116.16 parts water, 64.5334 parts silica fume, 0 parts desert sand, 5.16268 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size is 3-5 mm.

[0058] In the preparation method of this comparative example, the raw materials do not contain desert sand, and the remaining steps are exactly the same as in Example 1.

[0059] Comparative Example 3

[0060] The concrete in this comparative example was prepared from the following raw materials in parts by weight: 490.801 parts cement, 98.16 parts water, 54.5334 parts silica fume, 0 parts desert sand, 4.36268 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size is 3-5 mm.

[0061] In the preparation method of this comparative example, the raw materials do not contain desert sand, and the remaining steps are exactly the same as in Example 1.

[0062] The detailed component ratios of the above embodiments and comparative examples are shown in Table 1.

[0063] Table 1. Mix design of desert sand replacing cement

[0064]

[0065] The physical properties of the permeable concrete made entirely of travertine aggregate prepared in the above embodiments and comparative examples were tested. Detailed test results for compressive strength, permeability coefficient, and continuous porosity are summarized in Table 2.

[0066] Table 2 Performance test results of concrete in Examples 1-4 and Comparative Examples 1-3

[0067]

[0068] Example 5

[0069] The permeable concrete with all travertine aggregate in this embodiment is prepared from the following raw materials in parts by weight: 496.125 parts cement, 110.25 parts water, 61.25 parts silica fume, 55.125 parts glass powder, 4.9 parts water-reducing agent, and 1225 parts travertine. The travertine aggregate is the granules obtained after crushing travertine waste stone, and the travertine particle size is 10-15 mm.

[0070] The glass powder is waste glass powder with a particle size of less than 250 μm and a density of 2500 kg / m³. 3 .

[0071] The desert sand is natural fine desert sand with a particle size of less than 250 μm and a density of 2650 kg / m³. 3 .

[0072] The cement is ordinary Portland cement with a strength grade of 42.5 and a density of 3110 kg / m³. 3 .

[0073] The water-reducing agent is a BASF high-efficiency water-reducing agent with a water reduction rate of approximately 20%.

[0074] The silica fume is a mineral admixture with a specific surface area ≥15000 m² / kg and a SiO2 content ≥85%.

[0075] The permeable concrete made entirely of travertine aggregate in this embodiment is prepared using the cement-coated aggregate method (or "two-stage feeding method"), and the specific steps are as follows:

[0076] (1) Aggregate pretreatment: Weigh the travertine aggregate with a particle size of 10-15 mm according to the proportion and set aside.

[0077] (2) First mixing: Pour all the travertine aggregate into a forced mixer and dry mix for 60 seconds to make the aggregate evenly dispersed.

[0078] (3) Second mixing (half water and water-reducing agent): Add half the amount of water-reducing agent and half the amount of water, and continue mixing for 90 seconds to make the surface of the aggregate evenly wet.

[0079] (4) Third mixing (adding cementitious materials): Add cement, silica fume and glass powder, and continue mixing for 90 seconds to make the cementitious materials evenly coat the surface of the aggregate.

[0080] (5) Fourth mixing (remaining water and water-reducing agent): Add the remaining half of the water and half of the water-reducing agent, and continue mixing for 90 seconds to fully disperse the slurry and evenly coat the aggregate to obtain freshly mixed permeable concrete.

[0081] (6) Molding and initial curing: Pour the mixed concrete into a mold that has been coated with release oil, gently vibrate to compact it, smooth the surface, and let it stand at room temperature for 24 hours.

[0082] (7) Demolding and curing: Demold the sample after 24 hours, mark the sample, and immediately put it into the water tank for curing for 27 days (total curing period of 28 days). The curing water temperature is 20±2℃.

[0083] (8) Performance testing: After curing, the compressive strength, porosity, and permeability coefficient of the specimens shall be tested in accordance with the methods specified in the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081-2019) and the "Technical Specification for Permeable Cement Concrete Pavement" (CJJ / T 135-2009). Three parallel specimens shall be prepared for each mix proportion, and the arithmetic mean shall be taken as the test result.

[0084] Unless otherwise stated, the raw material specifications used in the following examples and comparative examples are the same as those in Example 5.

[0085] Example 6

[0086] The permeable concrete made entirely of travertine aggregate in this embodiment is prepared from the following raw materials in parts by weight: 441 parts cement, 110.25 parts water, 61.25 parts silica fume, 110.25 parts glass powder, 4.9 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size is 10-15 mm.

[0087] In this embodiment, the preparation method of the permeable concrete made entirely of travertine aggregate is the same as that described in Example 5.

[0088] Example 7

[0089] The permeable concrete with all travertine aggregate in this embodiment is prepared from the following raw materials in parts by weight: 385.875 parts cement, 110.25 parts water, 61.25 parts silica fume, 165.375 parts glass powder, 4.9 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size is 10-15 mm.

[0090] In this embodiment, the preparation method of the permeable concrete made entirely of travertine aggregate is the same as that described in Example 5.

[0091] Example 8

[0092] The permeable concrete with all travertine aggregate in this embodiment is prepared from the following raw materials in parts by weight: 330.75 parts cement, 110.25 parts water, 61.25 parts silica fume, 220.5 parts glass powder, 4.9 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size is 10-15 mm.

[0093] In this embodiment, the preparation method of the permeable concrete made entirely of travertine aggregate is the same as that described in Example 5.

[0094] Example 9

[0095] The permeable concrete with all travertine aggregate in this embodiment is prepared from the following raw materials in parts by weight: 396.9 parts cement, 88.2 parts water, 49 parts silica fume, 44.1 parts glass powder, 3.92 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size is 10-15 mm.

[0096] In this embodiment, the preparation method of the permeable concrete made entirely of travertine aggregate is the same as that described in Example 5.

[0097] Example 10

[0098] The permeable concrete with all travertine aggregate in this embodiment is prepared from the following raw materials in parts by weight: 330.75 parts cement, 73.5 parts water, 40.8333 parts silica fume, 36.75 parts glass powder, 3.26667 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size is 10-15 mm.

[0099] In this embodiment, the preparation method of the permeable concrete made entirely of travertine aggregate is the same as that described in Example 5.

[0100] Example 11

[0101] The permeable concrete made entirely of travertine aggregate in this embodiment is prepared from the following raw materials in parts by weight: 248.063 parts cement, 55.125 parts water, 30.625 parts silica fume, 27.5625 parts glass powder, 2.45 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size is 10-15 mm.

[0102] In this embodiment, the preparation method of the permeable concrete made entirely of travertine aggregate is the same as that described in Example 5.

[0103] Comparative Example 4

[0104] The concrete in this comparative example was prepared from the following raw materials in parts by weight: 551.25 parts cement, 110.25 parts water, 61.25 parts silica fume, 0 parts glass powder, 4.9 parts water-reducing agent, and 1225 parts travertine, wherein the travertine particle size was 10-15 mm.

[0105] In the preparation method of this comparative example, the raw materials do not contain glass powder, and the remaining steps are exactly the same as in Example 1.

[0106] The detailed component ratios of the above embodiments and comparative examples are shown in Table 3.

[0107] Table 3 Mix design for glass powder replacing cement

[0108]

[0109] The physical properties of the permeable concrete made entirely of travertine aggregate prepared in the above embodiments and comparative examples were tested. Detailed test results for compressive strength, permeability coefficient, and continuous porosity are summarized in Table 4.

[0110] Table 4. Performance test results of concrete in Examples 5-11 and Comparative Example 4

[0111]

[0112] Comparative Example 5

[0113] The permeable concrete with all travertine aggregate in this comparative example was prepared from the following raw materials in parts by weight: 551.25 parts cement, 110.25 parts water, 61.25 parts silica fume, 4.9 parts water-reducing agent, 1225 parts travertine, with a travertine particle size of 10-15 mm and a travertine powder particle size of less than 250 μm.

[0114] In the preparation method of this comparative example, the raw materials do not contain glass powder, and the remaining steps are exactly the same as in Example 1.

[0115] Comparative Example 6

[0116] The permeable concrete with all travertine aggregate in this comparative example was prepared from the following raw materials in parts by weight: 496.125 parts cement, 110.25 parts water, 61.25 parts silica fume, 55.125 parts travertine powder, 4.9 parts water-reducing agent, and 1225 parts travertine. The travertine particle size was 10-15 mm, and the travertine powder particle size was less than 250 μm.

[0117] The permeable concrete made entirely of travertine aggregate in this comparative example was prepared using the cement-coated aggregate method (or "two-stage feeding method"), and the specific steps are as follows:

[0118] (1) Aggregate pretreatment: Weigh the travertine aggregate with a particle size of 3-5 mm according to the proportion and set aside.

[0119] (2) First mixing: Pour all the travertine aggregate into a forced mixer and dry mix for 60 seconds to make the aggregate evenly dispersed.

[0120] (3) Second mixing (half water and water-reducing agent): Add half the amount of water-reducing agent and half the amount of water, and continue mixing for 90 seconds to make the surface of the aggregate evenly wet.

[0121] (4) Third mixing (adding cementitious materials): Add cement, silica fume and travertine powder, and continue mixing for 90 seconds to make the cementitious materials evenly coat the surface of the aggregate.

[0122] (5) Fourth mixing (remaining water and water-reducing agent): Add the remaining half of the water and half of the water-reducing agent, and continue mixing for 90 seconds to fully disperse the slurry and evenly coat the aggregate to obtain freshly mixed permeable concrete.

[0123] (6) Molding and initial curing: Pour the mixed concrete into a mold that has been coated with release oil, gently vibrate to compact it, smooth the surface, and let it stand at room temperature for 24 hours.

[0124] (7) Demolding and curing: Demold the sample after 24 hours, mark the sample, and immediately put it into the water tank for curing for 27 days (total curing period of 28 days). The curing water temperature is 20±2℃.

[0125] (8) Performance testing: After curing, the compressive strength, porosity, and permeability coefficient of the specimens shall be tested in accordance with the methods specified in the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081-2019) and the "Technical Specification for Permeable Cement Concrete Pavement" (CJJ / T 135-2009). Three parallel specimens shall be prepared for each mix proportion, and the arithmetic mean shall be taken as the test result.

[0126] Comparative Example 7

[0127] The permeable concrete with all travertine aggregate in this comparative example was prepared from the following raw materials in parts by weight: 441 parts cement, 110.25 parts water, 61.25 parts silica fume, 110.25 parts travertine powder, 4.9 parts water-reducing agent, and 1225 parts travertine. The travertine particle size was 10-15 mm, and the travertine powder particle size was less than 250 μm.

[0128] This comparative example uses the same preparation method as Comparative Example 6.

[0129] Comparative Example 8

[0130] The permeable concrete with all travertine aggregate in this comparative example was prepared from the following raw materials in parts by weight: 385.875 parts cement, 110.25 parts water, 61.25 parts silica fume, 165.375 parts travertine powder, 4.9 parts water-reducing agent, and 1225 parts travertine. The travertine particle size was 10-15 mm, and the travertine powder particle size was less than 250 μm.

[0131] This comparative example uses the same preparation method as Comparative Example 6.

[0132] Comparative Example 9

[0133] The permeable concrete with all travertine aggregate in this comparative example was prepared from the following raw materials in parts by weight: 330.75 parts cement, 110.25 parts water, 61.25 parts silica fume, 220.5 parts travertine powder, 4.9 parts water-reducing agent, and 1225 parts travertine. The travertine particle size was 10-15 mm, and the travertine powder particle size was less than 250 μm.

[0134] This comparative example uses the same preparation method as Comparative Example 6.

[0135] Comparative Example 10

[0136] The permeable concrete with all travertine aggregate in this comparative example was prepared from the following raw materials in parts by weight: 496.125 parts cement, 110.25 parts water, 61.25 parts silica fume, 55.125 parts limestone powder, 4.9 parts water-reducing agent, and 1225 parts travertine. The travertine particle size was 10-15 mm, and the limestone powder particle size was less than 250 μm.

[0137] The preparation method of this comparative example is the same as that of comparative example 6, the only difference being that the travertine powder in the raw materials is replaced with limestone powder.

[0138] Comparative Example 11

[0139] The permeable concrete with all travertine aggregate in this comparative example was prepared from the following raw materials in parts by weight: 441 parts cement, 110.25 parts water, 61.25 parts silica fume, 110.25 parts limestone powder, 4.9 parts water-reducing agent, and 1225 parts travertine. The travertine particle size was 10-15 mm, and the limestone powder particle size was less than 250 μm.

[0140] The preparation method of this comparative example is the same as that of comparative example 6, the only difference being that the travertine powder in the raw materials is replaced with limestone powder.

[0141] Comparative Example 12

[0142] The permeable concrete with all travertine aggregate in this comparative example was prepared from the following raw materials in parts by weight: 385.875 parts cement, 110.25 parts water, 61.25 parts silica fume, 165.375 parts limestone powder, 4.9 parts water-reducing agent, and 1225 parts travertine. The travertine particle size was 10-15 mm, and the limestone powder particle size was less than 250 μm.

[0143] The preparation method of this comparative example is the same as that of comparative example 6, the only difference being that the travertine powder in the raw materials is replaced with limestone powder.

[0144] Comparative Example 13

[0145] The permeable concrete with travertine aggregate in this comparative example was prepared from the following raw materials in parts by weight: 330.75 parts water, 110.25 parts silica fume, 61.25 parts limestone powder, 220.5 parts water-reducing agent, 4.9 parts travertine, and 1225 parts travertine. The travertine particle size was 10-15 mm, and the limestone powder particle size was less than 250 μm.

[0146] The preparation method of this comparative example is the same as that of comparative example 6, the only difference being that the travertine powder in the raw materials is replaced with limestone powder.

[0147] The detailed component ratios of the above embodiments and comparative examples are shown in Table 5:

[0148] Table 5. Mix design for cement replacement with travertine powder or limestone powder

[0149]

[0150] The physical properties of the permeable concrete made entirely of travertine aggregate prepared in the above comparative examples were tested. Detailed test results for compressive strength, permeability coefficient, and continuous porosity are summarized in Table 6.

[0151] Table 6 Performance test results of concrete in Comparative Examples 5-13

[0152]

Claims

1. A permeable concrete using travertine aggregate, characterized in that, It is prepared from the following raw materials in parts by weight: water 55.125~134.2 parts, cement 248.063~670.8 parts, water-reducing agent 2.45~5.96267 parts, silica fume 30.625~74.5334 parts, cement substitute 27.5625~268.32 parts, travertine aggregate 1225 parts, and the cement substitute is desert sand or glass powder.

2. The permeable concrete made entirely of travertine aggregate according to claim 1, characterized in that, It is prepared from the following raw materials in parts by weight: water 98.16~134.16 parts, cement 402.48~670.8 parts, silica fume 54.5334~74.5334 parts, water-reducing agent 4.36268~5.96267 parts, desert sand 67.08~268.32 parts, and travertine aggregate 1225 parts.

3. The permeable concrete made entirely of travertine aggregate according to claim 2, characterized in that, The desert sand is natural desert fine sand with a particle size of less than 250 μm; the travertine aggregate has a particle size of 3~5 mm.

4. The permeable concrete made entirely of travertine aggregate according to claim 1, characterized in that, It is prepared from the following raw materials in parts by weight: water 55.125~110.25 parts, cement 248.063~551.25 parts, silica fume 30.625~61.25 parts, glass powder 27.5625~220.5 parts, water-reducing agent 2.45~4.9 parts, and travertine aggregate 1225 parts.

5. The permeable concrete made entirely of travertine aggregate according to claim 4, characterized in that, The glass powder has a particle size of less than 250 μm; the travertine aggregate has a particle size of 10~15 mm.

6. The permeable concrete made entirely of travertine aggregate according to claim 1, characterized in that, The cement is silicate cement, and the water-reducing agent is BASF high-efficiency water-reducing agent.

7. The permeable concrete made entirely of travertine aggregate according to claim 1, characterized in that, The silica fume is a mineral admixture with a specific surface area ≥15000 m² / kg and a SiO2 content ≥85%.

8. A method for preparing permeable concrete using all travertine aggregate as described in any one of claims 1-7, characterized in that, The permeable concrete was prepared using the cement-coated stone method.

9. The preparation method according to claim 8, characterized in that, The preparation method includes the following steps: (1) Mix all the travertine aggregate to make the aggregate evenly dispersed; (2) Add half water-reducing agent and half water to the travertine aggregate obtained in step (1), stir, and make the surface of the aggregate evenly wet; (3) Add cementitious materials to the travertine aggregate obtained in step (2). The cementitious materials include cement, silica fume and cement substitutes. Stir to make the cementitious materials evenly coat the surface of the aggregate to obtain a mixture. (4) Add the remaining half of the water and half of the water-reducing agent to the mixture obtained in step (3), stir, so that the slurry is fully dispersed and evenly coats the aggregate to obtain freshly mixed permeable concrete; (5) After molding, initial curing, demolding and curing, the freshly mixed permeable concrete is obtained as described in the whole travertine aggregate permeable concrete.

10. The preparation method according to claim 9, characterized in that, In step (5), the freshly mixed permeable concrete is put into a mold that has been pre-coated with release oil, vibrated to compact it, and the surface is smoothed. It is then left to stand at room temperature to complete the molding and initial curing. The permeable concrete is then demolded and placed in a water tank for curing to complete the demolding and curing.

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