Design method of mix proportion of road premixed concrete with large slump based on filling property

Abstract

A method for designing mix proportions of high-slump ready-mixed concrete for roads based on fillability is disclosed, relating to the field of road construction. This method involves determining the permissible values ​​of concrete spread and slump time in an inverted slump cone; conducting trial mix design for the concrete pavement; calculating the standard values ​​of concrete spread and slump time in an inverted slump cone respectively; calculating temperature correction coefficients and transport time correction coefficients and adjusting the standard values ​​of spread and slump time in an inverted slump cone to obtain design values; and determining whether the design values ​​of concrete spread and slump time in an inverted slump cone simultaneously meet the permissible values ​​of both. This method can predict and ensure that the fillability of the prepared concrete meets construction requirements during the concrete mix design stage, thereby guaranteeing concrete quality.

Description

Technical Field

[0001] This application relates to the field of road construction, and more specifically, to a mix design method for high-slump ready-mixed concrete for roads based on filling properties. Background Technology

[0002] Ready-mixed concrete for roads has been widely used in cement concrete pavement construction in my country due to its excellent workability, energy saving, and environmental protection advantages. However, ready-mixed concrete for roads also has the following drawbacks: First, ready-mixed concrete has high unit water consumption, large cement content, high water-cement ratio, high sand ratio, and large slump, which leads to a large heat of hydration and significant drying and thermal shrinkage, making the pavement prone to early and severe cracking, resulting in the actual service life of the pavement not meeting the design life requirements. Second, there are no regulations governing the mix design technical requirements and parameters for high-slump ready-mixed concrete for roads. The content related to pavement concrete mix design in domestic industry standards only applies to concrete with a slump of 5-40mm, which cannot meet the construction requirements of ready-mixed cement concrete pavements for urban roads.

[0003] The filling property of ready-mixed concrete refers to its ability to uniformly and densely compact without external force. Insufficient filling property can easily lead to poor uniformity and insufficient density of ready-mixed concrete, resulting in segregation and cracking of the mixture. This can cause insufficient local strength of the pavement and easily lead to pavement structural damage. The filling property of ready-mixed concrete is mainly characterized by its spread and the emptying time in the inverted slump cone.

[0004] Currently, there is a lack of mix design methods for high-slump ready-mixed concrete for roads based on filling control, resulting in the current high-slump ready-mixed concrete for roads falling far short of the construction requirements of urban road surfaces. Summary of the Invention

[0005] The purpose of this application is to provide a mix design method for high slump ready-mixed road concrete based on fillability, which can predict and ensure that the fillability of the prepared concrete meets the construction requirements during the concrete mix design stage, thereby ensuring the quality of the concrete.

[0006] This application is implemented as follows:

[0007] This application provides a mix design method for high-slump ready-mixed concrete for roads based on filling properties, which includes the following steps:

[0008] Determine the permissible values ​​for the spread of concrete and the emptying time of the inverted slump cone, respectively;

[0009] Based on the design parameters of the concrete pavement, conduct trial mixing design of the concrete pavement mix proportion;

[0010] Based on the design trial mix of concrete pavement proportions, the standard values ​​of concrete spread and slump cone emptying time were calculated respectively.

[0011] Calculate the temperature correction factor and the transportation time correction factor;

[0012] The design values ​​for concrete spread and inverted slump cone emptying time are calculated based on the standard values ​​of the concrete spread and inverted slump cone emptying time adjusted by the temperature correction coefficient and the transportation time correction coefficient.

[0013] Determine whether the design values ​​of concrete spread and inverted slump cone evacuation time simultaneously meet the allowable values ​​of concrete spread and inverted slump cone evacuation time.

[0014] In some alternative implementations, the design parameters for concrete pavement include the design grade of concrete flexural strength, urban road grade, site temperature, and concrete transport time.

[0015] In some alternative implementations, the permissible spread of concrete is 430–520 mm for expressways, 420–520 mm for main roads, 410–520 mm for secondary roads, and 400–520 mm for branch roads; the permissible slump time for concrete is 6–9 s for expressways, 6–10 s for main roads, 6–12 s for secondary roads, and 6–15 s for branch roads.

[0016] In some alternative implementation schemes, when designing and testing the mix proportions of the concrete pavement based on the design parameters, the water-cement ratio is 0.44–0.48 and the paste volume is 310–340 L / m³ when the allowable flexural tensile strength of the concrete pavement is 4.5 MPa. 3 The volumetric sand ratio is 42-46%, and the slag powder content is less than 40%; when the allowable flexural tensile strength of the concrete pavement is 5 MPa, the water-cement ratio is 0.4-0.44, and the slurry volume is 320-350 L / m³. 3 The volumetric sand ratio is 40-44%, and the slag powder content is less than 40%.

[0017] In some alternative implementations, the standard value L of the concrete's spreadability is calculated. k Use the following formula:

[0018] The standard value t for calculating the evacuation time of the inverted slump cone for concrete. k Use the following formula:

[0019] in, V is the water-to-glue ratio. p The volume of the slurry (L / m³) 3 ), β represents the volumetric sand ratio (%), and β represents the slag powder content (%).

[0020] In some alternative implementations, the following formula is used when calculating the temperature correction factor: ζ T = 1 + 0.0052T - 2.08 × 10 -4 T 2 , where ζ T is the temperature correction factor; T is the ambient temperature, °C.

[0021] In some alternative implementations, the following formula is used when calculating the transit time correction factor: In the formula: ξ t t is the time correction factor. i The transit time is in hours (h).

[0022] In some alternative implementations, the design value L for the concrete spread is calculated. d Use the following formula: L d =ξ T ξ c L k ; Calculate the design value t for the slump time of concrete in the inverted slump cone. d Use the following formula:

[0023] In some alternative implementations, determining whether the design values ​​of concrete spread and inverted slump cone evacuation time simultaneously meet the allowable values ​​of concrete spread and inverted slump cone evacuation time means that the design values ​​of spread and inverted slump cone evacuation time are both within the allowable ranges of spread and inverted slump cone evacuation time. Furthermore, if the design values ​​of spread and inverted slump cone evacuation time are not within the allowable ranges of spread and inverted slump cone evacuation time, then the aforementioned design trial mix design work for the concrete pavement proportion based on the design parameters of the concrete pavement is repeated.

[0024] The beneficial effects of this application are as follows: The method for designing the mix proportion of ready-mixed concrete for roads based on filling properties provided in this application includes the following steps: determining the allowable values ​​of concrete spread and inverted slump cone emptying time respectively; conducting design trial mix design work for concrete pavement based on the design parameters of the concrete pavement; calculating the standard values ​​of concrete spread and inverted slump cone emptying time based on the design trial mix design work for the concrete pavement; calculating the temperature correction coefficient and the transportation time correction coefficient; adjusting the standard values ​​of concrete spread and inverted slump cone emptying time based on the temperature correction coefficient and the transportation time correction coefficient to calculate the design values ​​of concrete spread and inverted slump cone emptying time; and determining whether the design values ​​of concrete spread and inverted slump cone emptying time simultaneously meet the allowable values ​​of concrete spread and inverted slump cone emptying time. The high-slump road ready-mixed concrete mix design method based on fillability provided in this application can predict and ensure that the fillability of the prepared concrete meets the construction requirements during the concrete mix design stage, thereby ensuring the quality of the concrete. It has the advantages of simple operation and strong applicability, and can be widely promoted and applied in urban road pavement construction. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating the mix design method for high-slump road ready-mixed concrete based on filling properties, provided in an embodiment of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Therefore, the following detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] The following detailed description of the features and performance of the fill-based high-slump road ready-mixed concrete mix design method of this application, in conjunction with embodiments, provides further insight into its characteristics and performance.

[0029] This application provides a mix design method for high-slump ready-mixed concrete for roads based on filling properties, which includes the following steps:

[0030] Step 1: Determine the design parameters for the concrete pavement; optionally, the design parameters for the concrete pavement include the design grade of the concrete's flexural strength, the urban road grade, the site temperature, and the concrete transportation time; the concrete transportation time is the time it takes for the concrete to be transported from the concrete mixing plant to the construction site.

[0031] Step 2: Determine the spread L of the concrete. k and the emptying time t of the inverted slump cylinder k The permissible values ​​are as follows: Optionally, the permissible spread of concrete is 430–520 mm for expressways, 420–520 mm for main roads, 410–520 mm for secondary roads, and 400–520 mm for branch roads; the permissible slump time for concrete inverted cones is 6–9 s for expressways, 6–10 s for main roads, 6–12 s for secondary roads, and 6–15 s for branch roads; s is the unit of time, seconds.

[0032] Step 3: Conduct trial mix design of the concrete pavement based on the design parameters; optionally, when the allowable flexural tensile strength of the concrete pavement is 4.5 MPa, the water-cement ratio is 0.44–0.48, and the slurry volume is 310–340 L / m³. 3 The volumetric sand ratio is 42-46%, and the slag powder content is less than 40%; when the allowable flexural tensile strength of the concrete pavement is 5 MPa, the water-cement ratio is 0.4-0.44, and the slurry volume is 320-350 L / m³. 3 The volumetric sand ratio is 40-44%, and the slag powder content is less than 40%.

[0033] Step 4: Based on the design trial mix of the concrete pavement, calculate the standard values ​​of the concrete spread and the emptying time of the inverted slump cone.

[0034] Optionally, calculate the standard value L of concrete flowability. k Use the following formula:

[0035] Optionally, calculate the standard value t for the slump time of the concrete in the inverted slump cone. k Use the following formula:

[0036] in, V is the water-to-glue ratio. p The volume of the slurry (L / m³) 3 ), β represents the volumetric sand ratio (%), and β represents the slag powder content (%).

[0037] Step 5: Calculate the temperature correction factor and the transportation time correction factor; optionally, the following formula can be used to calculate the temperature correction factor: ξT=1+0.0052T-2.08×10 -4 T 2 , where ξ T Here, T is the temperature correction factor; T is the ambient temperature, in °C. Optionally, the following formula can be used when calculating the transportation time correction factor: In the formula: ξ t t is the time correction factor. i The time is the transportation time, where h is the unit of time, hours.

[0038] Step Six: Adjust the standard values ​​of concrete spread and inverted slump cone emptying time based on the temperature correction factor and transport time correction factor to obtain the design values ​​of concrete spread and inverted slump cone emptying time; optionally, calculate the design value L of concrete spread. d Use the following formula: Ld ＝ ξ T ξ c L k Optionally, calculate the design value t for the slump time of the concrete in the inverted slump cone. d Use the following formula:

[0039] Step 7: Determine whether the design values ​​of concrete spread and inverted slump cone emptying time simultaneously meet the allowable values ​​of concrete spread and inverted slump cone emptying time. Determining whether the design values ​​of concrete spread and inverted slump cone emptying time simultaneously meet the allowable values ​​means that both the design values ​​of spread and inverted slump cone emptying time are within the allowable ranges of spread and inverted slump cone emptying time. If the design values ​​of spread and inverted slump cone emptying time are not simultaneously within the allowable ranges of spread and inverted slump cone emptying time, repeat the above-mentioned design and trial mixing of concrete pavement proportions based on the design parameters of the concrete pavement.

[0040] The mix design method for ready-mixed concrete for high-slump roads based on filling properties provided in this application addresses the gap in existing pavement design methods regarding filling properties in pumped concrete for high-slump roads. Through long-term experience and statistical analysis, a formula for calculating the pressure bleeding rate of concrete is derived and corrected using construction temperature and concrete transport time. The final calculated design values ​​for concrete spread and inverted slump cone emptying time are compared with the allowable values ​​specified in construction regulations. This allows for prediction and assurance that the filling properties of the prepared concrete meet construction requirements during the mix design stage, ensuring concrete quality and avoiding or reducing defects such as segregation and cracking caused by poor uniformity and insufficient density in high-slump pumped concrete. It also prevents pavement structural damage due to insufficient local strength. This method is simple to operate and highly applicable, and can be widely promoted and applied in urban road pavement construction.

[0041] Example 1

[0042] This application provides a mix design method for high-slump ready-mixed concrete for roads based on filling properties, which includes the following steps:

[0043] Step 1: Determine the design parameters of the concrete pavement; Select a newly built main road in a city, which requires the preparation of a continuously reinforced surface concrete layer with a flexural tensile strength of 5.0MPa. The temperature at the construction site is 30℃ and the concrete transportation time is 0.5h.

[0044] Step 2: Determine the allowable value of concrete spread L as 420-520mm and the allowable value of slump bucket emptying time t as 6-10s.

[0045] Step 3: Conduct trial mix design for high-slump concrete based on the design parameters for the concrete pavement. The mix design parameters are: water-cement ratio of 0.44 and paste volume of 340 L / m³. 3 The volumetric sand ratio is 44%, and the slag powder content is 30% (all cementing materials are by mass).

[0046] Step 4: Calculate the standard value L of the expansion degree. k for:

[0047]

[0048] Calculate the standard value t of the evacuation time of the inverted slump cone k for:

[0049]

[0050] Step 5: Calculate the temperature correction factor and the transportation time correction factor; where the temperature correction factor ξ TFor: ξ T = 1 + 0.0052T - 2.08 × 10 -4 T 2 = 1 + 0.0052 × 30 - 2.08 × 10 -4 ×302=0.969; the transportation time correction factor ξt is:

[0051] Step Six: Adjust the standard value L of concrete spreadability based on the temperature correction factor and the transport time correction factor. k Standard value t for evacuation time of inverted slump cone k Calculate the design value L of concrete flowability. d Design value t for evacuation time of inverted slump cylinder d for:

[0052] L d =ξ T ξ t L k =0.969×0.982×445.9=424.0mm;

[0053]

[0054] Step 7: Determine the design value L for the concrete spread. d Design value t for evacuation time of inverted slump cylinder d Does it meet the requirements for the allowable spread value L of concrete and the allowable slump time t of the inverted slump cone? d =424.0∈[L]=[420.520],L d =424.0∈[L]=[420.520]. It can be seen that the design values ​​for the concrete spread and the design values ​​for the slump cone emptying time both meet the allowable requirements.

[0055] Example 2

[0056] This application provides a mix design method for high-slump ready-mixed concrete for roads based on filling properties, which includes the following steps:

[0057] Step 1: Determine the design parameters of the concrete pavement; Select a newly built secondary trunk road in a city, which requires the preparation of surface concrete with a flexural strength of 4.5MPa. The temperature at the construction site is 25℃ and the concrete transportation time is 1 hour.

[0058] Step 2: Determine the allowable value of concrete spread L as 430-520mm and the allowable value of slump bucket emptying time t as 6-12s.

[0059] Step 3: Conduct trial mix design for high-slump concrete based on the design parameters for the concrete pavement. The mix design parameters are: water-cement ratio of 0.46 and paste volume of 320 L / m³. 3 The volumetric sand ratio is 46%, and the slag powder content is 20% (all cementing materials are by mass).

[0060] Step 4: Calculate the standard value L of the expansion degree. k for:

[0061]

[0062] The standard value tk for the evacuation time of the inverted slump cone is calculated as follows:

[0063]

[0064] Step 5: Calculate the temperature correction factor and the transportation time correction factor; where the temperature correction factor ξ T For: ξ T = 1 + 0.0052T - 2.08 × 10 -4 T 2 = 1 + 0.0052 × 25 - 2.08 × 10 -4 ×25 2 =1; Transportation time correction factor ξ t for:

[0065] Step Six: Adjust the standard value L of concrete spreadability based on the temperature correction factor and the transport time correction factor. k Standard value t for evacuation time of inverted slump cone k Calculate the design value L of concrete flowability. d Design value t for evacuation time of inverted slump cylinder d for:

[0066] L d =ξ T ξ t L k =1×0.927×483.5=447.9mm;

[0067]

[0068] Step 7: Determine the design value L for the concrete spread. d Design value t for evacuation time of inverted slump cylinder d Does it meet the requirements for the allowable spread value L of concrete and the allowable slump time t of the inverted slump cone? d =447.9∈[L]=[430.520], t d=10.80∈[t]=[6.12]. It can be seen that the design values ​​of concrete spread and slump cone emptying time both meet the allowable requirements.

[0069] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A mix design method for high-slump ready-mixed concrete for roads based on filling properties, characterized in that, It includes the following steps: Determine the permissible values ​​for the spread of concrete and the emptying time of the inverted slump cone, respectively; Based on the design parameters of the concrete pavement, conduct trial mixing design of the concrete pavement mix proportion; Based on the design trial mix of the concrete pavement proportion, the standard values ​​of concrete spread and slump cone emptying time were calculated respectively. Calculate the standard value L of the concrete's spreadability. k Use the following formula: ; The standard value t for calculating the slump time of the inverted slump cone for the concrete is calculated. k Use the following formula: ;in, This refers to the water-to-glue ratio. The volume of the slurry is expressed in L / m³. 3 , β is the volumetric sand ratio, %; β is the slag powder content, %; Calculate the temperature correction factor and the transit time correction factor; the following formula is used to calculate the temperature correction factor: ,in, This is the temperature correction factor; T is the ambient temperature, in °C. The following formula is used to calculate the transportation time correction factor: In the formula: This is a time correction factor. For transportation time, h; Based on the temperature correction coefficient and the transportation time correction coefficient, the standard values ​​of the concrete spread and the inverted slump cone emptying time are adjusted to obtain the design values ​​of the concrete spread and the inverted slump cone emptying time; the design value L of the concrete spread is calculated. d Use the following formula: ; Calculate the design value t for the slump time of the inverted concrete slump cone. d Use the following formula: ; Determine whether the design values ​​of the concrete spread and the slump cone emptying time simultaneously meet the allowable values ​​of the concrete spread and the slump cone emptying time.

2. The mix design method for high-slump ready-mixed concrete for roads based on filling properties according to claim 1, characterized in that, The design parameters for the concrete pavement include the design grade of concrete flexural strength, urban road grade, site temperature, and concrete transportation time.

3. The mix design method for high-slump ready-mixed concrete for roads based on filling properties according to claim 1, characterized in that, The permissible spread of the concrete is 430-520mm for expressways, 420-520mm for main roads, 410-520mm for secondary roads, and 400-520mm for branch roads; the permissible slump time for the concrete in the inverted slump cone is 6-9s for expressways, 6-10s for main roads, 6-12s for secondary roads, and 6-15s for branch roads.

4. The method for designing mix proportions of high-slump ready-mixed concrete for roads based on filling properties according to claim 1, characterized in that, When designing and testing the concrete pavement mix proportions based on the aforementioned design parameters, when the allowable flexural tensile strength of the concrete pavement is 4.5 MPa, the water-cement ratio is 0.44~0.48, and the slurry volume is 310~340 L / m³. 3 The volumetric sand ratio is 42-46%, and the slag powder content is less than 40%; when the allowable flexural tensile strength of the concrete pavement is 5MPa, the water-cement ratio is 0.4-0.44, and the slurry volume is 320-350L / m³. 3 The volumetric sand ratio is 40-44%, and the slag powder content is less than 40%.

5. The method for designing mix proportions of high-slump ready-mixed concrete for roads based on filling properties according to claim 1, characterized in that, Determining whether the design values ​​of the concrete spread and the slump cone emptying time simultaneously meet the allowable values ​​of the concrete spread and the slump cone emptying time means that the design values ​​of the spread and the slump cone emptying time are both within the corresponding allowable values ​​of the spread and the slump cone emptying time. Furthermore, if the design values ​​of the spread and the slump cone emptying time are not within the allowable values ​​of the spread and the slump cone emptying time, then the above-mentioned design trial mix design work for the concrete pavement based on the design parameters of the concrete pavement is repeated.

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