Cement-based material rheological property regulation method based on ceramsite pore structure matching

Abstract

The application belongs to the technical field of building materials, and discloses a cement-based material rheological property regulation method based on ceramic granule pore structure matching. The method is based on ceramic granule pore structure characteristic parameters (BET specific surface area, MIP open pore volume and 48h water absorption rate) to predict and regulate the rheological property of the cement-based material, and abandons the traditional experience judgment which only depends on the bulk density or total water absorption rate, so that a quantitative mapping relationship between the micro pore structure and the macro rheological property is established. After the ceramic granule (such as 10-15mm ceramic granule) screened by the method is mixed into the cement-based material, the dynamic yield stress can be as low as 4.0Pa, and the spread can reach 735mm, so that the rheological property of the lightweight aggregate concrete is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a method for controlling the rheological properties of cement-based materials based on matching the pore structure of ceramsite. Background Technology

[0002] Lightweight aggregate concrete is increasingly widely used in high-rise buildings, long-span bridges, and precast components due to its advantages such as low density, high specific strength, and good thermal insulation properties. While expanded clay aggregate, the most commonly used lightweight coarse aggregate, imparts lightweight characteristics to concrete through its porous structure, it also presents the challenge of controlling its rheological properties in the freshly mixed state.

[0003] In existing technologies, the mix design of expanded clay concrete typically employs a trial mix method. This involves selecting the type and dosage of expanded clay based on experience, and repeatedly adjusting the water and water-reducing agent dosages to achieve the target slump or spread. This method has the following drawbacks: High trial-and-error costs: There are many types of ceramsite (shale ceramsite, fly ash ceramsite, porcelain slag ceramsite, etc.), with a wide particle size range (5-20mm). The performance of different batches of ceramsite fluctuates greatly, and a large number of tests are required to determine the appropriate ratio.

[0004] Lack of scientific predictive basis: Traditionally, the bulk density or total water absorption rate of expanded clay aggregates is used to assess their impact on concrete workability. However, studies have shown that expanded clay aggregates with the same water absorption rate exhibit significantly different rheological behaviors in concrete. For example, fly ash expanded clay aggregates (48h water absorption rate 25.95%) and porcelain slag expanded clay aggregates (48h water absorption rate 10.18%) have significantly different water absorption rates, but their effects on concrete yield stress are not simply linearly correlated. This indicates that existing single indicators are insufficient to explain the microscopic mechanisms underlying the rheological differences among different expanded clay aggregates.

[0005] It is difficult to achieve reverse engineering of performance: When a project requires specific rheological properties (such as low yield stress required for pumped concrete), existing methods cannot deduce which type of ceramsite should be selected from the target performance.

[0006] Therefore, developing a method that can rapidly predict the impact of ceramsite pore structure characteristics on the rheological properties of cement-based materials is of great significance for improving the mix design efficiency of lightweight aggregate concrete and reducing trial mixing costs. Summary of the Invention

[0007] The purpose of this invention is to overcome the limitations of existing technologies that rely solely on bulk density or total water absorption rate to evaluate the influence of expanded clay on the rheological properties of concrete, and to provide a method for predicting and controlling the rheological properties of cement-based materials based on the characteristic parameters of expanded clay pore structure (BET specific surface area, MIP open pore volume, 48h water absorption rate).

[0008] The method for controlling the rheological properties of cement-based materials based on the matching pore structure of ceramsite provided by this invention includes: Using multiple linear or nonlinear regression methods, based on the pore structure parameters SSA and V of the ceramsite... open and W 48 Establish the rheological property function of cement-based materials: τ d =a×SSA+b×V open +c, SF=d×W 48 +e×(1 / SSA)+f; Where SSA is the BET specific surface area of ​​ceramsite (unit: m²). 2 / g), V open The volume of open pores in the MIP of expanded clay aggregate (unit: cm³) 3 / g), W 48 The water absorption rate of ceramsite after 48 hours, τ d is the dynamic yield stress (in Pa), SF is the expansion (in mm), and a, b, c, d, e, and f are regression coefficients; The pore structure parameters of ceramsite were optimized using a method based on ceramsite pore structure matching to obtain the optimal rheological properties of cement-based materials.

[0009] Furthermore, when the ceramsite satisfies SSA < 2m 2 / g, V open <0.03cm 3 / g and W 48 When the content is in the range of 5%-15%, this expanded clay is the preferred expanded clay, and the concrete produced is expected to have low dynamic yield stress (≤50Pa) and high spread (≥600mm).

[0010] Furthermore, when the ceramsite satisfies SSA≥2m 2 / g, this type of expanded clay aggregate is not recommended because its well-developed pores and severe surface water loss will significantly increase the yield stress and plastic viscosity of concrete. It is predicted that the addition of this expanded clay aggregate will negatively impact the τ of cement-based materials. d >50Pa and SF<600mm.

[0011] Furthermore, when the ceramsite satisfies V ope ≥0.03cm 3 / g and W 48 When the content exceeds 15%, this expanded clay aggregate should be used with caution. It is necessary to increase the dosage of water-reducing agent or extend the pre-wetting time. The predicted τ value of cement-based materials with added expanded clay aggregate should be considered. d >50Pa and SF<600mm.

[0012] Furthermore, the particle size of the ceramsite is 10-15mm. Within this particle size range, the ceramsite has the best packing state and open pore connectivity, and its rheological properties are the easiest to control.

[0013] Furthermore, the volumetric content of the ceramsite is 25%-35% of the total volume of the coarse aggregate.

[0014] Furthermore, the ceramsite is selected from one or more of shale ceramsite, porcelain slag ceramsite, or fly ash ceramsite; among which porcelain slag ceramsite has the lowest specific surface area (0.19-0.45m²). 2 / g), making it most suitable for preparing ultra-high fluidity concrete; shale ceramsite has a moderate specific surface area (0.15-1.76m²). 2 / g), which can achieve good workability while ensuring a certain strength; fly ash ceramsite has the highest specific surface area (24-27m²). 2 / g), not recommended for use in high-flowability concrete.

[0015] The present invention also provides ceramsite obtained by screening by the above method, and most preferably, the ceramsite enables cement-based materials to obtain optimal rheological properties.

[0016] The present invention also provides a cement-based material containing the above-mentioned ceramsite, and most preferably, the cement-based material has the best rheological properties.

[0017] The present invention also provides the above method and the use of the ceramsite screened by the above method in regulating the rheological properties of cement-based materials. Based on the pore structure parameters of the ceramsite, cement-based materials with the expected rheological properties can be obtained.

[0018] The beneficial effects of this invention are as follows: 1. Scientific and precise, establishing a micro-macro mapping: This invention is the first to simultaneously introduce BET specific surface area and MIP open pore volume into the rheological performance evaluation system of cement-based materials, revealing the quantitative relationship between micropore structure and macroscopic workability, and proposing a specific threshold (SSA < 2m). 2 / g, V open <0.03cm 3 / g, W 48 (between 5% and 15%), predicting the rheological properties of cement-based materials.

[0019] 2. High efficiency and low consumption, shortening the design cycle: Through the pre-established pore structure-rheological mapping model function, the applicability of ceramsite can be quickly determined without conducting a large number of trial mixes. Compared with the traditional trial mix method, this invention can shorten the mix design cycle by more than 50%, significantly reducing labor and material costs.

[0020] 3. Significant effects and thorough verification: The preferred ceramsite selected by the method of this invention (such as 10-15mm porcelain slag ceramsite) can achieve a dynamic yield stress as low as 4.0 Pa, an expansion of up to 735 mm, and a significant reduction in plastic viscosity, while eliminating the shear thickening phenomenon under high dosage. Actual test data are in high agreement with predicted values, verifying the effectiveness of the threshold.

[0021] 4. Strong universality and wide range of applications: The method of this invention is applicable to various lightweight aggregates such as shale ceramsite, fly ash ceramsite, and porcelain slag ceramsite. It can be widely applied to the mix design of various lightweight aggregate concretes, providing a scientific basis for the engineering application of lightweight aggregate concrete. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method of the present invention.

[0023] Figure 2 This is a comparison chart of the specific surface areas of different types of ceramsite.

[0024] Figure 3 This is a map showing the MIP pore size distribution of different types of ceramsite.

[0025] Figure 4 The graph shows the 48-hour water absorption rate of different types of ceramsite.

[0026] Figure 5 A comparison diagram of the actual dynamic yield stress of different types of ceramsite cement-based materials.

[0027] Figure 6 This is a graph showing the slump and spread of fly ash ceramsite cementitious materials.

[0028] Figure 7 This is a graph showing the slump and spread of ceramic slag ceramsite cement-based materials.

[0029] Figure 8 This is a graph showing the slump and spread of shale ceramsite cementitious materials. Detailed Implementation

[0030] The present invention will now be described in detail with reference to specific embodiments.

[0031] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0032] When a mass, concentration, temperature, time, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, it should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, the range 1-50 should be understood to include any number, combination of numbers, or subranges selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all decimal values ​​between the integers mentioned above, such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. Regarding subranges, specifically consider "nested subranges" extending from any endpoint of the range. For example, nested sub-ranges of the exemplary range 1-50 may include 1-10, 1-20, 1-30 and 1-40 in one direction, or 50-40, 50-30, 50-20 and 50-10 in another direction.

[0033] The singular form includes the plural objects of discussion unless the context clearly indicates otherwise. "Optional" or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event occurs and the possibility that the event does not occur.

[0034] Approximate terms used in the specification and claims to modify quantities indicate that the invention is not limited to that specific quantity, but also includes acceptable modifications close to that quantity that do not alter the relevant essential function. Correspondingly, the use of "about," "approximately," etc., to modify a numerical value means that the invention is not limited to that precise value. In some instances, approximate terms may correspond to the precision of the instrument used to measure the value. In this application's specification and claims, scope definitions can be combined and / or interchanged, unless otherwise stated, these scopes include all subscopes contained therein.

[0035] Furthermore, the indefinite articles “a” and “an” preceding the elements or components of this invention do not impose any limitation on the quantity requirement (i.e., the number of times) of the elements or components. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers to the singular form.

[0036] Figure 1The flowchart of the method of the present invention determines whether it is a preferred target ceramsite by establishing a predictive relationship between the pore structure parameters of ceramsite and the rheological properties of cement-based materials.

[0037] The present invention will be further described below with reference to specific embodiments.

[0038] The pore structure parameters of the ceramsite selected in this embodiment are as follows: Figure 2-4 As shown in Table 1, the preferred pore structure parameters of the ceramsite with a particle size of 10-15 mm used in this invention are as follows: Table 1 The above-mentioned expanded clay aggregate was used to replace ordinary crushed stone, and combined with manufactured sand, cement, silica fume, mineral powder, water, and water-reducing agent to prepare expanded clay aggregate concrete. The specific formula is shown in Table 2 below: Table 2 Its actual rheological parameters were tested using a rheometer, and the results are as follows: Figure 5 and Figure 6 As shown: Lightweight aggregate concrete 1 exhibits a dynamic yield stress of 4.0 Pa, a spread of 735 mm, low plastic viscosity, and no shear thickening. Its 7-day autogenous shrinkage and drying shrinkage are the lowest among the three types of lightweight aggregate, demonstrating excellent rheological properties and good volume stability. Lightweight aggregate concrete 3, on the other hand, has a dynamic yield stress of 8.9 Pa, a spread of only 580 mm, and a low goodness of fit between torque and rotational speed, indicating high flow resistance and poor workability.

[0039] The method of multiple linear regression was used, based on the pore structure parameters SSA and V of the ceramsite. open and W 48 The rheological property function of the above-mentioned ceramsite concrete was established to predict its dynamic yield stress and spread, and the equation is as follows: τ d =0.184×SSA-1.50×V open +4.0, SF = 13.57 × W 48 +69.71×(1 / SSA)+225.25; The calculation results are shown in Table 3 below: Table 3 The above results show that the method of the present invention can accurately predict the rheological properties of cement-based materials through the pore structure parameters of ceramsite, and thereby screen out target cement-based materials with low dynamic yield stress and high expansion. Among them, the predicted yield stress and expansion of porcelain slag ceramsite and fly ash ceramsite are in high agreement with the actual data. However, due to the low water absorption rate of shale ceramsite, the actual yield stress is much higher than the predicted value. The regression model is only not applicable to this case, but it still has accuracy in predicting its expansion.

[0040] It is understood that the above specific embodiments are all further illustrations of the present invention and are not intended to limit the scope of protection of the present invention. For those skilled in the art, all other modifications and refinements obtained without creative effort are within the scope of protection of the present invention.

Claims

1. A method for controlling the rheological properties of cement-based materials based on matching the pore structure of ceramsite, characterized in that, include: Using multiple linear or nonlinear regression methods, based on the pore structure parameters SSA and V of the ceramsite... open and W 48 Establish the rheological property function of cement-based materials: t d =a×SSA+b×V open +c, SF=d×W 48 +e×(1 / SSA)+f; Where SSA is the BET specific surface area of ​​the ceramsite, V open W represents the volume of the open pores of the ceramsite MIP. 48 The water absorption rate of ceramsite after 48 hours, τ d , where is the dynamic yield stress, SF is the expansion, and a, b, c, d, e, and f are regression coefficients; The pore structure parameters of ceramsite were optimized using a method based on ceramsite pore structure matching to obtain the optimal rheological properties of cement-based materials.

2. The method for controlling the rheological properties of cement-based materials based on the matching pore structure of ceramsite according to claim 1, characterized in that, When SSA < 2m 2 / g, V open <0.03cm 3 / g and W 48 Within the range of 5%-15%, the predicted cement-based material τ with added ceramsite is... d ≤50Pa and SF≥600mm.

3. The method for controlling the rheological properties of cement-based materials based on the matching pore structure of ceramsite according to claim 1, characterized in that, When SSA≥2m 2 / g, predicting the cement-based material τ with added ceramsite. d >50Pa and SF<600mm.

4. The method for controlling the rheological properties of cement-based materials based on the matching pore structure of ceramsite according to claim 1, characterized in that, When V is satisfied ope ≥0.03cm 3 / g and W 48 When the content is greater than 15%, the predicted τ of cement-based materials with added ceramsite is... d >50Pa and SF<600mm.

5. The method for controlling the rheological properties of cement-based materials based on the matching pore structure of ceramsite according to claim 1, characterized in that, The particle size of the ceramsite is 10-15 mm.

6. The method for controlling the rheological properties of cement-based materials based on the matching pore structure of ceramsite according to claim 1, characterized in that, The volumetric content of the ceramsite is 25%-35% of the total volume of the coarse aggregate.

7. The method for controlling the rheological properties of cement-based materials based on the matching pore structure of ceramsite according to claim 1, characterized in that, The ceramsite is one or more of shale ceramsite, porcelain slag ceramsite, or fly ash ceramsite.

8. A type of ceramsite, characterized in that, The method described in any one of claims 1-7 is used for screening.

9. A cement-based material, characterized in that, It contains the ceramic particles as described in claim 8.

10. Use of the method of claim 1 in regulating the rheological properties of cement-based materials.

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