A surface layer pervious concrete mix proportion design method

Abstract

The present application relates to a surface pervious concrete mix proportion design method, selecting suitable aggregate, cementing material and additive; determining the cementing material slurry water-binder ratio; calculating the cementing material slurry density; determining the design theoretical porosity, determining the cementing material slurry required for a single pervious concrete under a certain initial porosity according to the volume method; forming test pieces under different gradient compaction strengths; curing the surface pervious concrete test pieces under standard conditions, and testing the porosity, water permeability coefficient and compressive strength of the test pieces at the specified age; determining the linear relationship between the compaction strength and the construction compaction strength, fitting out the relationship curve between the unit mass compaction strength of the surface pervious concrete and the porosity, water permeability coefficient and compressive strength; determining the mix proportion and compaction strength of the pervious concrete. The prepared surface wear-resistant pervious concrete has controllable effective porosity, high compressive strength, high surface wear resistance, small deviation between construction performance and laboratory test performance, and can guide the selection of compaction equipment (selecting appropriate compaction output power) to a certain extent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a pervious concrete mix proportion design method, and more particularly to a surface pervious concrete mix proportion design method. BACKGROUND

[0002] With the continuous advancement of urbanization construction, the disadvantages of traditional infrastructure in cities are gradually exposed, resulting in increasingly prominent urban environmental problems such as urban flood disasters and heat island effects. Pervious concrete is a kind of porous cement concrete mixed by aggregates, cementitious materials, water and additives, etc., which has strong water permeability and irreplaceable decorative functions, etc., and has unique advantages in creating good physical and ecological environments such as sound, light and heat, and is the main building material for building "sponge cities" and "park cities", which has great promoting significance for energy saving, environmental improvement and low-carbon society creation.

[0003] At present, the pervious concrete mix proportion design basically refers to the (absolute) volume method calculation in the Technical Specification for Pervious Cement Concrete Pavement CJJ / T135, that is, the amount of unit volume aggregate and the volume of paste are calculated according to the close-packed density of aggregate and the design porosity, the amount of cementitious material and water is calculated after setting the water-cement ratio, and thus the final mix proportion is determined, but the parameters of the pervious concrete prepared by this method deviate from the theoretical design parameters. Especially for surface pervious concrete, in order to prevent impurities from entering the interior of the pervious concrete and blocking the pores, making the water permeability ineffective, the surface structure pervious concrete is generally prepared by using small particle aggregates (1.18mm-9.5mm), which has a large particle surface area and needs more paste to wrap its surface. At the same time, the cohesiveness of pervious concrete is large, which is easy to agglomerate, resulting in a large deviation of the actual parameters of surface pervious concrete from the theoretical parameters, and some even as high as 20%, which brings great risk to the control of the quality of pervious concrete.

[0004] CN 108548914 A discloses a pervious concrete mix proportion design method based on the characteristics of aggregate and the thickness of paste wrapping, which uses the volume method to design the mix proportion of pervious concrete with the close-packed density of aggregate, the specific surface area of aggregate and the thickness of paste wrapping as the main design parameters according to the close-packed principle of aggregate and the uniform wrapping model of paste. However, the thickness of paste and the specific surface area are obtained by simultaneous calculation and are an ideal state. In practice, the adhesion between the wrapped particles is not a "point-to-point" contact adhesion, but a lap joint between "surface-to-surface". The number of contact points, the adhesion width of contact points and other conditions are closely related to the working state, mechanical properties and water permeability of pervious concrete and other key indicators.

[0005] CN 109305781 A discloses a mix design method for high-strength, high-permeability concrete based on a skeleton structure. This method designs the mix proportion of permeable concrete according to the target performance based on the relationship between the skeleton structure parameters, performance indicators, and mix proportion parameters of the permeable concrete. The invention considers the number of contact points N, the width of the contact area W, and the thickness of the slurry between aggregates T. However, this method is more theoretical, the formula is more complex, and the number of contact points, the width of the contact area, and the thickness of the slurry between aggregates are measured from the surface of the permeable concrete slice. The actual operation is more complicated and it is not suitable for actual production of premixed permeable concrete.

[0006] In permeable concrete structures, the lower layer is typically composed of large-particle aggregates, and the overlap area of ​​the grout in the contact zone is negligible compared to the aggregate particles, essentially representing a "point-to-point" contact. In contrast, the surface layer of permeable concrete uses smaller-particle aggregates. Due to the finer particles, the contact area between the grout-coating aggregates is more significant, and the larger specific surface area results in greater cohesion and agglomeration. This leads to a significant discrepancy between actual parameters and theoretical mix design parameters, hindering quality control and construction. In fact, during permeable concrete paving, the parameters of the surface layer are significantly affected by compaction. The compressive strength and permeability of the surface layer are closely related to its degree of compaction. Higher compaction results in more severe compression of the grout-coating aggregates, reducing permeability and increasing compressive strength. Conversely, lower compaction leads to insufficient inter-particle contact, resulting in more permeable pores and lower compressive strength.

[0007] In addition, since the surface structure is in contact with the outside world and directly bears the impact and friction generated by external activities, the surface particles are easily peeled off or worn, so special attention is needed when preparing permeable concrete for the surface.

[0008] Therefore, when designing permeable surface concrete, the actual construction conditions should be considered, including the effect of compaction machinery on the permeable surface concrete and the influence of compaction strength (compaction conditions) on the performance of the permeable surface concrete. This will ensure that the performance indicators of the permeable surface concrete after construction deviate little from the design parameters. At the same time, wear-resistant aggregate particles should be selected to enhance the wear resistance of the permeable surface concrete, thereby giving it excellent comprehensive properties such as anti-clogging, permeability, and wear resistance. Summary of the Invention

[0009] Based on the shortcomings of the prior art, the technical problem solved by the present invention is to provide a mix proportion for permeable concrete on the surface, mainly targeting the surface structure of permeable concrete pavement structural layers.

[0010] To address the aforementioned technical problems, this invention provides a method for designing the mix proportions of permeable surface concrete, comprising the following steps:

[0011] 1) Select appropriate aggregates, binders, and admixtures;

[0012] 2) Determine the water-cement ratio w of the binder slurry;

[0013] 3) Calculate the density of the binder slurry;

[0014] 4) Determine the theoretical porosity and determine the required binder slurry for a given initial porosity using the volumetric method;

[0015] 5) Prepare permeable surface concrete, and mold permeable surface concrete with different compaction strengths in a molding box. For each mix proportion, there are multiple different gradients of compaction strength, and multiple specimens are molded under each compaction strength.

[0016] 6) Curing surface permeable concrete specimens under standard conditions and testing their porosity, permeability coefficient and compressive strength at the specified age;

[0017] 7) Based on the loss of construction compaction strength, determine the linear relationship between compaction strength and construction compaction strength. Plot the porosity, permeability coefficient and compressive strength of the permeable concrete per unit mass on the XY plane coordinate axis respectively, and fit the relationship curves between the permeable concrete per unit mass compaction strength and porosity, permeability coefficient and compressive strength respectively.

[0018] 8) On the relationship diagram, select the compressive strength and corresponding compaction strength range that meet the conditions, select the porosity and permeability coefficient that meet the conditions and the corresponding compaction strength range, and select the optimal compaction strength and corresponding permeability coefficient, porosity and compressive strength according to cost and actual conditions, and then determine the mix proportion of permeable concrete.

[0019] 9) If the mix proportion cannot meet the requirements, the mix proportion shall be adjusted, and the relationship curve between the unit mass compaction strength of the permeable concrete and the porosity, permeability coefficient and compressive strength shall be re-determined to determine the concrete mix proportion and compaction strength that meet the conditions.

[0020] Specifically, the steps are as follows:

[0021] 1) Select appropriate aggregates and determine their compacted bulk density, porosity, water absorption rate, and apparent density;

[0022] Select a high-strength, wear-resistant single-size aggregate with a particle size of 1.18mm–2.36mm, 2.36mm–4.75mm, or 4.75mm–9.5mm, and test the compacted bulk density ρ of the aggregate. 堆 Water absorption rate I 吸 and apparent density ρ 石Therefore, the aggregate compaction porosity V can be obtained. 空 (1-ρ) 堆 / ρ 石 )×100%;

[0023] 2) Determine the water-cement ratio. Due to the high requirements for strength and wear resistance of the surface permeable concrete, the water-cement ratio is generally in the range of 0.15 to 0.30. At the same time, the spread of the binder slurry is controlled to be 180mm ± 20mm by the amount of admixture (1.0% to 3.0% of the mass of cementitious materials).

[0024] 3) Calculate the density of the cementitious slurry based on the water-cement ratio w, the composition and density of the cementitious material (ignoring air content):

[0025]

[0026] Where: ρ 胶 The density of the binder slurry;

[0027] m 水 The mass of water added is expressed in kg.

[0028] ρ 水 The density of water is kg / m³. 3 ;

[0029] m c The mass of cement added is expressed in kg.

[0030] ρ c The density of the cement added, kg / m³ 3 ;

[0031] m i矿 The mass of the i-th mineral admixture added is expressed in kg.

[0032] ρ i矿 The density of the added mineral admixture is expressed in kg / m³. 3 .

[0033] 4) Determine the theoretical design porosity e0, and calculate the required volumetric binder slurry (required volume ratio V) per cubic meter of permeable concrete at the initial porosity e0-Δe using the (absolute) volumetric method in the "Technical Specification for Permeable Cement Concrete Pavement" CJJ / T135. 空 -(e0-Δe)-V 引气 ), where Δe is the difference between the initial porosity and the theoretical porosity, which can be positive, negative or 0. In particular, when Δe > 0, the effect of compaction strength on porosity should be considered. When Δe ≤ 0, the effect of compaction strength on porosity can be disregarded, because under this condition, the porosity of the permeable concrete prepared is greater than the design theoretical porosity e0, and there is no situation where the porosity drops below e0 due to excessive compaction strength.

[0034] 5) Prepare permeable surface concrete and mold permeable surface concrete with different compaction strengths in a molding box. Each mix proportion has at least 6 different gradients of compaction strength, and at least 3 specimens are molded under each compaction strength.

[0035] During the molding of the cubic compressive strength specimen, the permeable surface concrete is poured freely into the mold from the top of the sleeve, flush with the top end of the sleeve, through the hollow interior of the sleeve. Each time, 500g ± 5g of permeable surface concrete is poured. Using a knife, the concrete is evenly compacted 5 times from one side of the mold to the other in two perpendicular directions. Then, it is compacted with a compaction hammer. For the first compaction, the hammer is dropped freely from a position where its lower edge is 25 ± 1mm ​​above the top end of the sleeve. This compaction is repeated a certain number of times. Then, the permeable surface concrete is poured again. The concrete was compacted a certain number of times (l) using a compaction hammer. With each layer, the hammer's free-fall position was 25mm ± 1mm ​​higher than the previous free-fall position. This process was repeated, adding and compacting the permeable surface concrete until the final layer of permeable concrete exceeded the top of the mold by more than 10mm. The scale reading (k) corresponding to the upper surface of the specimen in the sleeve and the number of times the permeable surface concrete was added (c) were recorded. From this, the compaction strength (w) per unit mass of the permeable surface concrete can be calculated. 透 Specimen molding should be completed before the initial setting of the permeable concrete.

[0036]

[0037] In the formula, w 透 The compaction strength per unit mass of the permeable concrete surface layer is expressed in J / kg.

[0038] m 锤 The mass of the hammer is measured in kg.

[0039] g is the acceleration due to gravity, 9.8 m / s². 2 ;

[0040] h 落 The free fall height of the hammer is measured in meters (m).

[0041] l represents the number of times the compaction hammer strikes each layer;

[0042] c represents the number of times the permeable surface concrete is applied;

[0043] m 透 The mass of the permeable concrete surface layer poured into each layer is expressed in kg.

[0044] Because m 锤 g, m 透It is known that, since the compaction hammer was added 25mm ± 1mm ​​at the point of impact at each layer, the height variation caused by the presence of permeable surface concrete in the test mold was approximately offset. The free fall height h of the compaction hammer was... 落 The concrete strength per unit mass can be considered as the sum of the sleeve height and the internal height of the mold, i.e., 0.6m. Therefore, the compaction strength per unit mass of permeable concrete can be approximated as:

[0045] w 透 =11.76l (3) After compaction, remove the sleeve, remove the surface permeable concrete particles that exceed the upper edge of the mold and smooth the surface. After 24 hours, demold the surface permeable concrete, and the cubic compressive strength specimen is prepared. It can be seen from formula (3) that the unit mass compaction strength is only related to the number of compactions per layer. By changing the number of compactions, the performance parameters of surface permeable concrete with different gradient compaction strengths can be obtained.

[0046] 6) Curing the demolded permeable concrete specimens under standard conditions and testing their porosity, permeability coefficient and compressive strength at the specified age (28d). The test results of the specimens at each compaction strength shall be determined with reference to the Technical Specification for Permeable Cement Concrete Pavement (CJJ / T135).

[0047] 7) Based on the actual compaction strength loss during construction, determine the linear relationship between the compaction strength and the compaction strength of the construction machinery. The compaction strength and the actual compaction strength during construction have the following relationship: w 透 =αw 施 Where α is the conversion factor between actual compaction strength and impact strength during construction, that is, the effective strength coefficient of the compaction strength of construction machinery during actual construction. Because some of the work is often lost during actual construction, the value of α is less than 1.0, and it can generally be taken as 0.50 to 0.95, depending on the effective output compaction work of the construction machinery. The surface permeable concrete unit mass compaction strength corresponding to porosity, permeability coefficient, and compressive strength is plotted on the XY plane coordinate axes, and the relationship curves between the surface permeable concrete unit mass compaction strength and porosity, permeability coefficient, and compressive strength are fitted by software, as shown in the figures below. Figure 6 , Figure 7 and Figure 8 As shown;

[0048] like Figure 6 In the middle, v 理The theoretical minimum porosity, which is the porosity of the permeable surface concrete obtained using the volumetric mix proportion method, is mainly affected by the vibration packing void ratio of the aggregate and the volume ratio of binder to aggregate. However, it cannot be achieved in practice. Compaction or compaction can only approach it infinitely because some binder is always located at the interface between aggregates, preventing direct contact between aggregates. Therefore, the porosity of the permeable surface concrete obtained by the volumetric mix proportion method can never be reached. With the increase of compaction strength, it can only approach the porosity of the permeable surface concrete obtained by the volumetric mix proportion method.

[0049] v 初 The initial porosity of the un-compacted permeable concrete surface layer is related to the initial working state and relative dosage of the binder. The greater the vibration spread of the binder, the higher the initial porosity v. 初 The smaller, the greater, v 初 The larger the initial porosity, the less it affects the theoretical minimum porosity. Simultaneously, the higher the relative amount of binder used, the higher the initial porosity v. 初 The smaller, the greater, v 初 The larger the initial porosity, the less favorable it is to the bonding between permeable concrete particles, as both excessive and insufficient initial vibratory spread of the binder are detrimental to the bonding and affect the theoretical minimum porosity. Generally, the binder spread is 180mm ± 20mm, therefore the initial porosity v... 初 It is directly related to the amount of binder.

[0050] Aggregate volume in the test mold

[0051] The volume of the slurry in the test mold

[0052] In the formula: L 石 m is the volume of the aggregate in the mold. 3 ;

[0053] L 浆 m is the volume of the binder in the mold. 3 ;

[0054] m 石 The mass of aggregate added when preparing permeable concrete, in kg;

[0055] m 浆 The mass of grout added during the preparation of permeable concrete, expressed in kg;

[0056] ρ 石 Aggregate density, kg / m³ 3 ;

[0057] ρ 浆 The density of the slurry is calculated using the formula, in kg / m³. 3 ;

[0058] c represents the number of times the permeable surface concrete is applied;

[0059] m 透 The mass of the permeable concrete surface layer poured into each layer is expressed in kg.

[0060] k is the scale reading k,m, on the upper surface of the specimen after compaction in the sleeve;

[0061] The volume of the trial mold was 0.001 m³. 3 The corresponding porosity of the specimen

[0062] Figure 7 This is a graph showing the relationship between compaction strength and permeability coefficient of permeable concrete. Figure 7 and Figure 6 The trends are quite similar, but... Figure 7 When no compaction strength is applied, testing the permeability coefficient is meaningless. Therefore, it cannot intersect the Y-axis when X=0. Furthermore, when the compaction strength of permeable concrete is infinitely large, the porosity tends to the theoretical minimum porosity, while the permeability coefficient tends to 0. This is because under infinite compaction strength, the interconnected pores will be blocked by grout flow, thus making it impossible for water to pass through, but the porosity will always exist.

[0063] from Figure 8 As can be seen, when the surface permeable concrete has no compaction strength, it is difficult to form strength due to the loose bond between the aggregates. As the compaction strength increases, the compressive strength first increases rapidly. This is because compaction makes the bond between the mortar-coated aggregates tight and reduces the porosity, thus rapidly increasing the compressive strength of the permeable concrete. Then, as the compaction strength increases, the compressive strength increases slightly. This is because the porosity has approached the theoretical minimum porosity, and the bond between the mortar-coated aggregates is already very tight, leaving little room for further increase in compressive strength. At a certain compaction strength, its strength reaches its maximum value. Subsequently, as the compaction strength increases, it decreases slightly. This is because as the compaction strength continues to increase, the aggregates are already in close contact. Further increases in compaction strength will damage the aggregate particles, causing micro-cracks at the bonding points and inside the aggregates, thereby reducing the mechanical properties of the surface permeable concrete.

[0064] 8) Select the compressive strength and corresponding compaction strength range that meet the conditions from the relationship curve obtained in step 7), select the porosity and permeability coefficient that meet the conditions and the corresponding compaction strength range, and select the optimal compaction strength and corresponding permeability coefficient, porosity and compressive strength according to cost and actual situation, and then determine the mix proportion of permeable concrete.

[0065] 8) On the relationship diagram, select the compressive strength and corresponding compaction strength range that meet the conditions, and select the porosity and permeability coefficient and corresponding compaction strength range that meet the conditions (e.g., when the conditions are met). Figure 6Point A in the diagram requires a porosity greater than A. Y At that time, the compaction strength of permeable concrete should not exceed A. X ; Figure 7 Point B in the diagram requires a permeability coefficient greater than B. Y At that time, the compaction strength of permeable concrete should not exceed B. X ; Figure 8 Point C in the equation requires a compressive strength greater than C. Y When compaction strength of permeable concrete is not less than C, the compaction strength should not be less than C. X The overlapping area within the range is the suitable compaction strength and performance range under this mix proportion. If there is no overlapping area, the mix proportion should be adjusted and the test should be repeated. Based on cost and actual conditions, the optimal compaction strength and the corresponding permeability coefficient, porosity and compressive strength should be selected, and then the mix proportion of permeable concrete should be determined.

[0066] 9) If the mix proportion cannot meet the requirements (there is no overlapping area of ​​compaction strength), the mix proportion shall be adjusted (the water-cement ratio, cementitious material composition, initial design porosity, air entrainment of admixtures, etc. can be adjusted), and the relationship curve between the unit mass compaction strength of the permeable concrete surface layer and porosity, permeability coefficient and compressive strength shall be re-determined to determine the concrete mix proportion and appropriate compaction strength that meet the conditions.

[0067] As a preferred embodiment of the above technical solution, the surface permeable concrete mix design method provided by the present invention further includes some or all of the following technical features:

[0068] As an improvement to the above technical solution, the cement is ordinary Portland cement or Portland cement with a strength grade of not less than 42.5; the mineral admixture is one or more of silica fume, Class I fly ash, and S95 mineral powder.

[0069] As an improvement to the above technical solution, the aggregate is a single-sized aggregate, further comprising one of 1.18mm~2.36mm, 2.36mm~4.75mm, or 4.75mm~9.5mm, wherein the parent rock strength is not less than 150MPa, and the rock's soundness coefficient f≥10; the content of its needle-like and flaky particles is not greater than 5% according to the test of "Aggregates for High-Performance Concrete" JG / T568; and the aggregate's water absorption rate is not greater than 2%.

[0070] As an improvement to the above technical solution, the admixture is a composite admixture with a water reduction rate of 15% to 20%, which also has multiple functions such as air entrainment and water retention, and introduces air content V. 引气 The micropores (existing in the slurry) account for 2% to 5% of the bulk volume of the concrete, and the moisture evaporation rate of permeable concrete transported to the construction site is no more than 2%.

[0071] As an improvement to the above technical solution, the molding box sleeve, test mold, and compaction hammer are used. The test mold is made of steel with internal dimensions of 100mm×100mm×100mm and a thickness of not less than 10mm. The upper part has a convex interface to connect with the sleeve. The sleeve is made of transparent material, hollow inside, with internal dimensions of 100mm×100mm×500mm and a thickness of not less than 10mm. The lower end has a concave interface to connect with the test mold. The sleeve has graduations on the outside, with each graduation being 1mm. The 0 graduation is located at the contact position with the test mold, and the measuring range is not less than 50mm. The compaction hammer is a rectangular block of 99mm×99mm×50mm, weighing 1000g±5g. It can be used to apply compaction work to the surface permeable concrete and simultaneously form a 100mm×100mm×100mm cubic compressive strength test specimen.

[0072] As an improvement to the above technical solution, in step 2), the water-cement ratio is determined, and the water-cement ratio of the binder slurry is 0.15 to 0.30. According to the "Test Method for Homogeneity of Concrete Admixtures" GB T8077-2012, the spread of the binder slurry is tested to be 180mm ± 20mm.

[0073] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0074] (1) This invention takes into account the strength of the action of construction machinery on permeable concrete during actual construction, and introduces the compaction strength into the mix design of surface permeable concrete, so that the design parameters of surface permeable concrete are more in line with the actual construction parameters, and improves the construction quality control.

[0075] (2) The surface permeable concrete directly bears the load and the effects of the external environment, so its performance requirements are relatively high. Reasonable preparation and compaction are crucial. Considering the compaction strength provides a good reference for selecting reasonable compaction machinery and equipment for construction, and plays a positive role in the reasonable arrangement of construction.

[0076] (3) The porosity of the permeable surface can be easily calculated based on parameters such as the scale reading. It can be used to test the porosity of the permeable surface concrete during on-site construction, thereby controlling its compaction quality.

[0077] (4) The surface permeable concrete is prepared using wear-resistant materials. The prepared permeable concrete has excellent comprehensive properties such as controllable porosity and permeability coefficient, high compressive strength, and good wear resistance.

[0078] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, the following detailed description is provided in conjunction with preferred embodiments. Attached Figure Description

[0079] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below.

[0080] Figure 1 Schematic diagram of point-to-point contact between mortar-coated particles in permeable concrete;

[0081] Figure 2 Schematic diagram of the "face-to-face" contact between mortar-coated particles in permeable concrete;

[0082] Figure 3 : Schematic diagram of the trial molding;

[0083] Figure 4 : Sleeve schematic diagram;

[0084] Figure 5 Schematic diagram of molding box;

[0085] Figure 6 Schematic diagram showing the relationship between compaction strength and porosity of permeable concrete;

[0086] Figure 7 Schematic diagram showing the relationship between compaction strength and permeability coefficient of permeable concrete;

[0087] Figure 8 Schematic diagram showing the relationship between compaction strength and permeable concrete strength;

[0088] Figure 9 Schematic diagram showing the relationship between compaction strength and porosity of permeable concrete when the design porosity is 15% and the initial porosity is 14%;

[0089] Figure 10 Schematic diagram showing the relationship between compaction strength and permeability coefficient of permeable concrete when the design porosity is 15% and the initial porosity is 14%;

[0090] Figure 11 Schematic diagram showing the relationship between compaction strength and permeable concrete strength when the design porosity is 15% and the initial porosity is 14%;

[0091] Figure 12 Schematic diagram showing the relationship between compaction strength and porosity of permeable concrete when the design porosity is 15% and the initial porosity is 18%;

[0092] Figure 13 Schematic diagram showing the relationship between compaction strength and permeability coefficient of permeable concrete when the design porosity is 15% and the initial porosity is 18%;

[0093] Figure 14 Schematic diagram showing the relationship between compaction strength and permeable concrete strength when the design porosity is 15% and the initial porosity is 18%. Detailed Implementation

[0094] The following detailed description of specific embodiments of the present invention is part of this specification. The principles of the present invention are illustrated through examples, and other aspects, features and advantages of the present invention will become apparent from this detailed description.

[0095] Example

[0096] Includes the following steps:

[0097] (1) P·O 42.5 cement, Grade I fly ash as binder, and aggregates of 2.36mm to 4.75mm were selected to prepare the surface wear-resistant concrete. The properties of each raw material met the requirements of the claims of this invention, and the cement density was set at 3100kg / m³. 3 The density of Class I fly ash is 2300 kg / m³. 3 The aggregate density is 2700 kg / m³. 3 The compacted bulk density is 1650 kg / m³. 3 The parent rock has a strength of 160 MPa, a rock firmness coefficient f = 10, a flaky / needle particle content of 5%, and an aggregate water absorption rate of 2%; the aggregate compaction porosity V0 空 The water content is 38.89%, it is a composite admixture, the water reduction rate is 16%, the air content introduced is 4% of the concrete volume, and the water evaporation rate of the permeable concrete transported to the construction site is 2%.

[0098] (2) The initial water-cement ratio is set to 0.25, the amount of Class I fly ash is 30% of the cementitious material, and the spread of the cementitious slurry is controlled to 180mm±20mm by the amount of admixture (1.0% to 3.0% of the mass of cementitious material);

[0099] (3) Based on the water-cement ratio of 0.25, the composition and density of the cementitious material (ignoring air content), the density of the cementitious slurry is calculated using the formula:

[0100]

[0101] Example 1

[0102] (4) The theoretical design porosity e0 is set to 15%, and referring to the (absolute) volume method in the "Technical Specification for Permeable Cement Concrete Pavement" CJJ / T135, the required binder slurry volume fraction for a single cubic meter of permeable concrete with an initial porosity of 14% (e0-Δe is a value less than e0, so that a porosity of e0 can be obtained under a certain compaction strength) is calculated to be 20.89%. Assuming an initial 1m 3 If the aggregate in the permeable concrete surface layer is 1650 kg, then the required mass of grout is 430 kg.

[0103] (5) Prepare permeable surface concrete according to the theoretical volume ratio in (4), and form permeable surface concrete with different compaction strengths in the molding box. Each mix ratio has at least 6 different gradients of compaction strength (e.g., when the number of compaction times for the 8 gradients are 2, 4, 6, 8, 10, 12, 14, and 16, the compaction strengths are 23.52 J / kg, 47.04 J / kg, 70.56 J / kg, 94.08 J / kg, 117.6 J / kg, 141.12 J / kg, 164.64 J / kg, and 188.16 J / kg, respectively). Form 3 specimens under each compaction strength and record the scale reading k on the upper surface of the specimen in the sleeve after compaction.

[0104] After compaction, remove the sleeve, remove the surface permeable concrete particles that extend beyond the upper edge of the mold, and smooth the surface. After 24 hours, demold the surface permeable concrete, and the cubic compressive strength specimen is ready.

[0105] (6) Curing the permeable concrete specimens after demolding under standard conditions, and testing their porosity, permeability coefficient and compressive strength at the specified age (28d). The test results of the specimens under each compaction strength shall be determined with reference to the Technical Specification for Permeable Cement Concrete Pavement (CJJ / T135).

[0106] (7) Based on the strength loss during compaction of the permeable concrete surface layer by the construction machinery, determine the effective output coefficient α of the compaction strength. Setting the loss value to 10%, the effective strength coefficient α is 0.9. 施 =w 透 ÷α, the unit mass compaction strength converted to the unit mass compaction strength during construction is 26.12 J / kg, 52.27 J / kg, 78.40 J / kg, 104.53 J / kg, 130.67 J / kg, 156.80 J / kg, 182.93 J / kg, 209.07 J / kg).

[0107] (8) Plot the unit mass compaction strength of the permeable concrete surface layer corresponding to the porosity, permeability coefficient, and compressive strength on the XY plane coordinate axes, respectively. Then, use software to fit the relationship curves between the unit mass compaction strength of the permeable concrete surface layer and the porosity, permeability coefficient, and compressive strength, as shown in the figures below. Figure 9 , Figure 10 and Figure 11 As shown;

[0108] (9) The porosity of the surface permeable concrete shall be not less than 15%, the permeability coefficient shall be not less than 10 mm / s, and the compressive strength shall be not less than 30 MPa. Figure 9 , Figure 10 and Figure 11Find the corresponding suitable range of compaction strength. When the porosity is not less than 15%, the construction compaction strength of permeable concrete should not exceed 115.2 J / kg (a(115.2,15)); when the permeability coefficient is greater than 10 mm / s, the construction compaction strength of permeable concrete should not exceed 101.3 J / kg (b(101.3,10)); when the compressive strength is greater than 30 MPa, the construction compaction strength of permeable concrete should not be less than 86.5 J / kg (c(86.5,30)). The overlapping compaction strength range is 86.5 J / kg to 101.3 J / kg. Therefore, the suitable unit mass compaction strength for surface permeable concrete construction is 86.5 J / kg to 101.3 J / kg, and appropriate construction compaction equipment can be selected accordingly.

[0109] If the porosity is controlled at 16% and the air entrainment rate is 4%, then the volume content of aggregate and slurry per unit volume is 0.80 m³. 3 The required compaction strength is 98.6 J / kg. In the initial mix design, the mass of aggregate and grout are 1650 kg and 430 kg respectively. Therefore, 0.80 m... 3 The mass ratio of slurry to aggregate remains 430:1650, and the densities of the slurry and aggregate are known. Therefore, the mass of the slurry per unit volume is 425 kg / m³. 3 The mass of aggregate per unit volume is 1630 kg / m³. 3 Therefore, the mix proportion is revised to 1610 kg / m³ of aggregate per cubic meter of permeable concrete. 3 The mass of the slurry is 420 kg / m³. 3 (Cement mass is 258 kg / m³) 3 The fly ash mass is 78 kg / m³ 3 The water mass is 84 kg / m³ 3 Since the amount of admixtures used is extremely small, they can be disregarded. The main consideration is the effect of admixtures on the fluidity and air content of the slurry.

[0110] The prepared surface wear-resistant permeable concrete was tested after construction at a compaction strength of 98.6 J / kg. Its porosity was 15.9%, its permeability coefficient was 11.8 mm / s, its 28-day compressive strength was as high as 32.5 MPa, and its wear resistance Ia (the ratio of grinding head revolutions (thousand revolutions) to grinding groove depth (mm)) was 2.5. It has good comprehensive performance and fully meets the design requirements.

[0111] Furthermore, the porosity, permeability coefficient, and compressive strength corresponding to a given compaction strength can be identified. This allows for the determination of whether the surface permeable concrete performance meets the predetermined design requirements under the specified strength of the construction machinery during actual construction. (For example, if the compaction strength of the construction machinery can only meet 80 J / kg, it is impossible to simultaneously meet good porosity, permeability coefficient, and compressive strength. The mix proportion should be adjusted so that the construction machinery can simultaneously meet multiple performance requirements when constructing permeable concrete.) This facilitates quality control of the surface permeable concrete.

[0112] Example 2

[0113] (4) Under the condition that the performance parameters of various raw materials remain unchanged in the embodiments, the theoretical porosity e0 is set to 15%, and the volume ratio of the binder slurry required per cubic meter of permeable concrete is calculated to be 16.89% with the (absolute) volume method in the "Technical Specification for Permeable Cement Concrete Pavement" CJJ / T135 when the initial porosity is 18% (the porosity can be guaranteed, and when the compaction strength is infinitely large, the porosity is infinitely close to 18%, which is greater than 15%). Assuming 1m 3 If the aggregate in the permeable concrete surface layer is 1600 kg, then the required mass of grout is 348 kg.

[0114] (5) Prepare permeable surface concrete according to the theoretical volume ratio in (4), and form permeable surface concrete with different compaction strengths in the molding box. Each mix ratio has at least 6 different gradients of compaction strength (e.g., when the number of compaction times for the 8 gradients are 2, 4, 6, 8, 10, 12, 14, and 16, the compaction strengths are 23.52 J / kg, 47.04 J / kg, 70.56 J / kg, 94.08 J / kg, 117.6 J / kg, 141.12 J / kg, 164.64 J / kg, and 188.16 J / kg, respectively). Form 3 specimens under each compaction strength and record the scale reading k on the upper surface of the specimen in the sleeve after compaction.

[0115] After compaction, remove the sleeve, remove the surface permeable concrete particles that extend beyond the upper edge of the mold, and smooth the surface. After 24 hours, demold the surface permeable concrete, and the cubic compressive strength specimen is ready.

[0116] (6) Curing the permeable concrete specimens after demolding under standard conditions, and testing their porosity, permeability coefficient and compressive strength at the specified age (28d). The test results of the specimens under each compaction strength shall be determined with reference to the Technical Specification for Permeable Cement Concrete Pavement (CJJ / T135).

[0117] (7) Based on the strength loss during compaction of the permeable concrete surface layer by the construction machinery, determine the effective output coefficient α of the compaction strength. Setting the loss value to 10%, the effective strength coefficient α is 0.9. 施 =w 透 ÷α, the unit mass compaction strength converted to unit mass compaction strength is 26.12 J / kg, 52.27 J / kg, 78.40 J / kg, 104.53 J / kg, 130.67 J / kg, 156.80 J / kg, 182.93 J / kg, 209.07 J / kg).

[0118] (8) Plot the unit mass compaction strength of the permeable concrete surface layer corresponding to the porosity, permeability coefficient, and compressive strength on the XY plane coordinate axes, respectively. Then, use software to fit the relationship curves between the unit mass compaction strength of the permeable concrete surface layer and the porosity, permeability coefficient, and compressive strength, as shown in the figures below. Figure 12 , Figure 13 and Figure 14 As shown;

[0119] (9) The porosity of the surface permeable concrete shall be not less than 15%, the permeability coefficient shall be not less than 10 mm / s, and the compressive strength shall be not less than 30 MPa. Figure 12 The porosity of all components meets the requirements. Figure 13 and Figure 14 Find the corresponding suitable range of compaction strength. When the permeability coefficient is greater than 10 mm / s, the compaction strength of permeable concrete should not exceed 116.2 J / kg (b(117.2, 10)); when the compressive strength is greater than 30 MPa, the compaction strength of permeable concrete should not be less than 128.8 J / kg (c(129.4, 30)). There are no overlapping compaction strength ranges, so the requirements are not met under this mix proportion, and the mix proportion should be readjusted.

[0120] In summary, the present invention, in conjunction with the construction machinery, clarifies the influence of compaction strength on the performance of permeable concrete. It can determine the appropriate compaction strength of permeable concrete based on existing mix proportions, providing a reference for the rational selection of construction machinery and the preparation of suitable surface wear-resistant permeable concrete, ensuring that the performance indicators of permeable concrete pavement achieve the expected results.

[0121] All the raw materials listed in this invention, as well as the upper and lower limits and ranges of the raw materials and the upper and lower limits and ranges of the process parameters (such as temperature, time, etc.), can realize this invention. Examples are not listed one by one here.

[0122] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for designing the mix proportions of permeable surface concrete, characterized in that, It includes the following steps: 1) Select appropriate aggregates, binders, and admixtures; 2) Determine the water-cement ratio w of the binder slurry; 3) Calculate the density of the binder slurry; 4) Determine the theoretical porosity and determine the required binder slurry for a given initial porosity using the volumetric method; 5) Prepare permeable surface concrete, and mold permeable surface concrete with different compaction strengths in a molding box. For each mix proportion, multiple compaction strengths are prepared, and multiple specimens are molded at each compaction strength. The compaction strength and the construction compaction strength are related as follows: ,in This is the conversion factor between construction compaction strength and impact compaction strength. The value is less than 1.0; 6) Curing surface permeable concrete specimens under standard conditions and testing their porosity, permeability coefficient and compressive strength at the specified age; 7) Based on the loss of construction compaction strength, determine the linear relationship between compaction strength and construction compaction strength. Plot the porosity, permeability coefficient and compressive strength of the permeable concrete per unit mass on the XY plane coordinate axis respectively, and fit the relationship curves between the permeable concrete per unit mass compaction strength and porosity, permeability coefficient and compressive strength respectively. 8) On the relationship diagram, select the compressive strength and corresponding compaction strength range that meet the conditions, select the porosity and permeability coefficient that meet the conditions and the corresponding compaction strength range, and select the optimal compaction strength and corresponding permeability coefficient, porosity and compressive strength according to cost and actual conditions, and then determine the mix proportion of permeable concrete. 9) If the mix proportion cannot meet the requirements, the mix proportion shall be adjusted, and the relationship curve between the unit mass compaction strength of the permeable concrete and the porosity, permeability coefficient and compressive strength shall be re-determined to determine the concrete mix proportion and compaction strength that meet the conditions. The admixture is a composite admixture with a water reduction rate of 15%–20% and introduces an air content of V. 引气 These are tiny pores that exist in the slurry, accounting for 2% to 5% of the gross volume of the concrete. The water evaporation rate of permeable concrete transported to the construction site is no more than 2%.

2. The method for designing the mix proportion of permeable surface concrete according to claim 1, characterized in that, The aggregate is a high-strength, wear-resistant single-size aggregate with a particle size of 1.18mm to 2.36mm, 2.36mm to 4.75mm, or 4.75mm to 9.5mm. The parent rock strength is not less than 150MPa, the rock's firmness coefficient f≥10, the content of needle-like and flaky particles is not greater than 5%, and the aggregate's water absorption rate is not greater than 2%.

3. The method for designing the mix proportion of permeable surface concrete according to claim 1 or 2, characterized in that, The binder is made of cement and mineral admixtures.

4. The method for designing the mix proportion of permeable surface concrete according to claim 3, characterized in that, The cement is ordinary Portland cement or Portland cement with a strength grade of not less than 42.5; the mineral admixture is one or more of silica fume, Class I fly ash, and S95 mineral powder.

5. The method for designing the mix proportion of permeable surface concrete according to claim 1, characterized in that, The water-cement ratio ranges from 0.15 to 0.30, and the spread of the binder slurry is 180 mm ± 20 mm.

6. The method for designing the mix proportion of permeable surface concrete according to claim 1, characterized in that, The molding box used in step 5) consists of a sleeve, a test mold, and a tamping hammer. The test mold is made of steel and has a convex interface at the top that connects to the sleeve. The sleeve is made of transparent material, hollow inside, and has a concave interface at the bottom that connects to the test mold. The sleeve has graduations on the outside, with each graduation being 1mm. The 0 graduation is located at the contact position with the test mold, and the range is not less than 50mm. The tamping hammer is a rectangular block with a weight of 1000g ± 5g.

7. The method for designing the mix proportion of permeable surface concrete according to claim 6, characterized in that, The internal dimensions of the test mold are 100mm×100mm×100mm, and the thickness is not less than 10mm; the internal dimensions of the sleeve are 100mm×100mm×500mm, and the thickness is not less than 10mm; the dimensions of the tamping hammer are 99mm×99mm×50mm.

8. A method for designing the mix proportion of permeable surface concrete according to claim 6 or 7, characterized in that, During the molding of cubic compression specimens in the molding box, the permeable concrete surface layer falls freely into the mold from the top of the sleeve, flush with the top end of the sleeve, through the hollow interior of the sleeve. Each time it is filled... The surface permeable concrete was compacted multiple times in two perpendicular directions from one side of the test mold to the other using a tool. It was then compacted with a compaction hammer. For the first compaction, the hammer was dropped freely from a position h above the upper end of the sleeve at its lower edge. This compaction was repeated a certain number of times. Afterwards, the surface layer of permeable concrete is applied again and compacted a certain number of times with a compaction hammer. Each time the hammer is dropped, its position is h higher than the previous position. This process of adding and compacting the surface layer of permeable concrete is repeated until the final layer of permeable concrete reaches a position above the top of the mold. The corresponding scale reading on the sleeve is then recorded. And the number of times the surface permeable concrete is poured. Therefore, the compaction strength per unit mass of the surface permeable concrete can be calculated. After compaction, remove the sleeve, remove the surface permeable concrete particles that extend beyond the upper edge of the mold, and smooth the surface. After the predetermined molding time, demold the surface permeable concrete, and the cubic compressive strength specimen is thus prepared.

Images