Methods and systems for determining the creep of cement paste

Abstract

This application relates to a method and system for measuring the creep of cement slurry. The method includes: etching a pre-prepared cement slurry sample using a focused ion beam etching device to obtain cement slurry micropillars; applying stress to the cement slurry micropillars using a flat indenter of an instrumented nano-addition loading device and recording the indentation data; and determining the short-term creep data of the cement slurry based on the indentation data. This method can quickly determine the short-term creep data of cement slurry.

Description

Technical Field

[0001] This application relates to the field of civil engineering technology, and in particular to a method and system for measuring the creep of cement slurry. Background Technology

[0002] Cement paste, as a multi-scale, multi-phase material, exhibits creep from the micro-scale hydration product calcium silicate gel (CSH) to the macro-scale concrete structure.

[0003] In terms of microscopic experiments, nanoindentation creep testing is one of the important methods for studying CSH creep. Its significant feature is that by applying extremely high stress (close to 1 GPa) through the indenter, it can quickly characterize the long-term creep data of CSH.

[0004] However, the stress applied in the nanoindentation creep test is too high, making it difficult to determine short-term creep data using this method. Summary of the Invention

[0005] Therefore, it is necessary to provide a method and system for measuring the creep of cement paste, which can quickly determine the short-term creep data of cement paste, in order to address the above-mentioned technical problems.

[0006] In a first aspect, this application provides a method for determining the creep of cement paste, the method comprising:

[0007] A pre-prepared cement slurry sample was etched using a focused ion beam etching device to obtain cement slurry micropillars;

[0008] Stress was applied to cement slurry microcolumns using a flat pressure head of an instrumented nano-addition loading device, and the pressure head data was recorded.

[0009] Short-term creep data of cement paste are determined based on pressure head data.

[0010] In one embodiment, the above-mentioned cement slurry sample is etched using a focused ion beam etching device to obtain cement slurry micropillars, including:

[0011] A focused ion beam etching device was used to perform multiple circumferential cutting processes on preset points on the cement slurry sample to obtain cement slurry micropillars of preset size.

[0012] In one embodiment, before performing multiple circumferential etching processes on preset points on the cement slurry sample using a focused ion beam etching device, the method further includes:

[0013] A protective layer is sprayed onto the preset points using a focused ion beam etching device.

[0014] In one embodiment, the above-mentioned flat pressure head using an instrumented nano-addition loading device applies stress to the cement slurry micro-column, including:

[0015] Multi-stage stress loading was applied to the top of the cement slurry micro-column using a flat pressure head of an instrumented nano-addition loading device.

[0016] In one embodiment, the load variation of the above-mentioned multi-stage stress loading increases exponentially; each stage of stress loading includes three phases: loading, holding, and unloading.

[0017] In one embodiment, the head data includes the applied pressure and head displacement, and the determination of short-term creep data of the cement paste based on the head data includes:

[0018] The amount of base settlement deformation is determined based on the pressure applied by the indenter and a pre-established settlement effect model;

[0019] The deformation of the indenter is determined based on the pressure applied by the indenter and the sinking effect model.

[0020] The deformation of the micro-column is determined based on the displacement of the indenter, the settlement deformation of the base, and the deformation of the indenter.

[0021] Short-term creep data of cement paste microcolumns were determined based on the pressure applied by the pressure head, the deformation of the microcolumn, and the settling effect model.

[0022] In one embodiment, the determination of short-term creep data for cement paste microcolumns based on the pressure applied by the pressure head, microcolumn deformation, and subsidence effect model includes:

[0023] Substituting the pressure applied by the indenter and the deformation of the micro-column into the first relation of the subsidence effect model, the specific creep compliance is calculated to obtain the short-term creep data of the cement paste micro-column.

[0024] The first relationship includes the correspondence between the micro-column deformation and the micro-column deformation flexibility, the pressure applied by the pressure head, the initial height of the cement slurry micro-column, and the planar cross-sectional area; the micro-column deformation flexibility is determined based on the Young's modulus and specific creep flexibility of the cement slurry micro-column; the planar cross-sectional area of ​​the cement slurry micro-column is determined based on the top diameter and bottom diameter of the cement slurry micro-column.

[0025] In one embodiment, determining the base settlement deformation based on the pressure applied by the indenter and a pre-established settlement effect model includes:

[0026] Substitute the pressure applied by the pressure head into the second relation of the subsidence effect model to calculate the deformation amount and obtain the subsidence deformation amount of the base.

[0027] The second relationship includes the correspondence between the amount of subsidence deformation and the subsidence flexibility, and the pressure applied by the pressure head; the subsidence flexibility is determined based on the contact area between the cement paste micro-column and the subsidence, the Young's modulus of the subsidence, and Poisson's ratio.

[0028] In one embodiment, determining the indenter deformation based on the indenter applied pressure and the sinking effect model includes:

[0029] The deformation amount of the indenter is obtained by substituting the pressure applied by the indenter into the third relation of the subsidence effect model.

[0030] The third relationship includes the correspondence between the indenter deformation amount, the indenter deformation flexibility, and the pressure applied by the indenter. The indenter deformation flexibility is determined based on the top area of ​​the cement paste micro-column, the Young's modulus of the indenter, and the Poisson's ratio.

[0031] Secondly, this application also provides a system for measuring the creep of cement paste. This system includes a focused ion beam etching device, an instrumented nano-addition loading device, and a computer device;

[0032] A focused ion beam etching device is used to etch pre-prepared cement slurry samples to obtain cement slurry micropillars.

[0033] An instrumented nano-addition loading device is used to apply stress to cement slurry micro-columns through a flat pressure head and record the pressure head data;

[0034] Computer equipment used to determine short-term creep data of cement paste based on pressure head data.

[0035] The aforementioned method and system for determining cement slurry creep involves using a focused ion beam etching (FIB) device to etch a pre-prepared cement slurry sample, obtaining cement slurry micropillars. A flat indenter from an instrumented nano-addition loading device is then used to apply stress to the cement slurry micropillars, and the indenter data is recorded. The short-term creep data of the cement slurry is determined based on the indenter data. This application utilizes FIB etching technology to prepare cement slurry micropillars suitable for creep testing, and the flat indenter allows for precise and controllable stress application to the cement slurry micropillars at the microscopic level, thereby rapidly determining the short-term creep data of the cement slurry. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1This is a diagram illustrating the application environment of the cement paste creep measurement method in one embodiment.

[0038] Figure 2 This is a flowchart illustrating a method for determining the creep of cement paste in one embodiment;

[0039] Figure 3a This is a schematic diagram of the cement slurry sample preparation process in one embodiment;

[0040] Figure 3b This is a schematic diagram of the cement slurry micropillar etching process in one embodiment;

[0041] Figure 4a This is a schematic diagram of four circumferential cutting processes in one embodiment;

[0042] Figure 4b This is a schematic diagram of the etching process in one embodiment;

[0043] Figure 5 This is a graph showing the indenter load versus time in one embodiment;

[0044] Figure 6 This is a flowchart illustrating the steps for determining short-term creep data of cement paste in one embodiment;

[0045] Figure 7 This is a cross-sectional view of a cement slurry micro-column in one embodiment;

[0046] Figure 8a This is a graph showing the indenter displacement and indenter load in one embodiment;

[0047] Figure 8b This is a graph showing the duration of load and the specific creep compliance in one embodiment;

[0048] Figure 9 This is a flowchart illustrating the method for determining the creep of cement paste in another embodiment;

[0049] Figure 10 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0051] First, before introducing the technical solutions of the embodiments of this application, the technical background or evolution of the embodiments of this application will be introduced. Cement paste, as a multi-scale, multi-phase material, exhibits creep from the micro-scale hydration product calcium silicate gel (CSH) to the macro-scale concrete structure. In terms of microscopic experiments, nanoindentation creep testing is one of the important methods for studying CSH creep. Its significant feature is that by applying extremely high stress (close to 1 GPa) with an indenter, it can quickly characterize the long-term creep data of CSH. However, the stress applied in nanoindentation creep testing is too high, making it difficult to determine short-term creep data. Currently, there is also a test method that uses micro-cutting technology to prepare micro-cantilever beam samples. However, the stress applied in this method is too small. Although it can determine short-term creep data, the test process is very long and the time cost is high.

[0052] To address the challenges of determining short-term creep data in nanoindentation creep tests and the lengthy testing processes in microcantilever beam tests, this application provides a method for determining the creep of cement slurry. This method employs focused ion beam etching to etch a pre-prepared cement slurry sample, obtaining cement slurry micropilles. A flat indenter from an instrumented nano-addition loading device is then used to apply stress to the cement slurry micropilles, and the indentation data is recorded. The short-term creep data of the cement slurry is determined based on the indentation data. This application utilizes focused ion beam etching technology to prepare cement slurry micropilles suitable for creep testing, and the flat indenter allows for precise and controllable stress application to the cement slurry micropilles at the microscopic level, thereby rapidly determining the short-term creep data of the cement slurry.

[0053] The method for determining the creep of cement paste provided in this application embodiment can be applied to, for example... Figure 1The application environment shown includes a cement slurry creep measurement system, which may include a focused ion beam etching device 101, an instrumented nano-addition loading device 102, and a computer device 103. The focused ion beam etching device 101 and the instrumented nano-addition loading device 102 can communicate with the computer device 103 via a network. The computer device 103 can control the focused ion beam etching device 101 and the instrumented nano-addition loading device 102, and can also acquire relevant data from them. The focused ion beam etching device 101 can use focused ion beam (FIB) technology for etching, and the ion source can be Xe ions. The instrumented nano-addition loading device 102 can be configured with indenters of various shapes. In this embodiment, a flat indenter is mainly used. The flat indenter can precisely control the stress, ensuring that the stress applied to the cement slurry micro-column is between tens of MPa and hundreds of MPa, solving the problems of excessive stress only determining long-term creep data and insufficient stress leading to a long test process. Computer equipment 103 may be, but is not limited to, various personal computers, laptops, tablets, and independent servers or server clusters composed of multiple servers.

[0054] In one embodiment, such as Figure 2 As shown, a method for determining the creep of cement paste is provided, and this method is applied to... Figure 1 Taking the cement paste creep measurement system as an example, the following steps are included:

[0055] Step 201: The pre-prepared cement slurry sample is etched using a focused ion beam etching device to obtain cement slurry micropillars.

[0056] like Figure 3a As shown, the preparation process of a cement paste sample may include:

[0057] 1) Inject the freshly mixed cement slurry into the plastic pipe and seal it, then place the plastic pipe containing the cement slurry into the concrete curing room; the inner diameter of the plastic pipe can be 10mm.

[0058] 2) Remove the cement slurry that has been cured to a certain age from the plastic tube, and use a cutting machine to cut a cylinder of the first preset thickness for epoxy resin mounting; wherein, the first preset thickness can be 5mm.

[0059] 3) After the epoxy resin has hardened, the sample is mounted on silicon carbide sandpaper and polished to obtain a sample with a second preset thickness; wherein, the silicon carbide sandpaper used for polishing can be 400 grit, 1200 grit and 2500 grit in sequence, and the second preset thickness can be slightly greater than 2 mm.

[0060] 4) Polish the ground sample to obtain a cement slurry sample; the polishing time can be 90 min, the polishing liquid is a 1 μm diamond suspension, and the thickness of the cement slurry sample is 2 mm.

[0061] After the cement slurry sample is prepared, it is bonded to the sample stage of a focused ion beam etching (FBE) system. Silver paste can be used as the bonding material. Due to the poor conductivity of cement-based materials, the bonded sample needs to undergo carbon or gold plating to allow for clear observation of its microstructure and different phases under an electron microscope. The carbon or gold plating process can last for one hour. In practical applications, the BSE (Back Scattered Electron) mode of the FBE system can be used to select appropriate locations and etch cement slurry micropillars, such as... Figure 3b As shown.

[0062] It should be noted that, in order to provide a safe and operable space for the subsequent pressure-applying flat head, the outer diameter of the groove of the cement slurry micro-column should be larger than the diameter of the flat head. For example, a cement slurry micro-column with a top diameter of 5 μm is used with a flat head with a diameter of 20 μm; therefore, the outer diameter of the groove of the cement slurry micro-column can be set to 25–30 μm.

[0063] Step 202: Stress is applied to the cement slurry micro-column using a flat pressure head of an instrumented nano-addition loading device, and the pressure head data is recorded.

[0064] The pressure head data may include pressure head displacement, pressure applied by the pressure head, and pressure loading duration.

[0065] A pressure head using an instrumented nano-addition loading device was used to apply pressure to cement slurry microcolumns, causing them to deform. During the pressure application process, pressure data such as head displacement, applied pressure, and loading duration were recorded.

[0066] Step 203: Determine the short-term creep data of the cement paste based on the pressure head data.

[0067] Among them, short-term creep data is used to characterize the short-term creep behavior of cement paste, which may include specific creep compliance.

[0068] When a cement paste micro-column is pressurized by a pressure head, its bottom will sink into the substrate; this phenomenon is called the "sinking effect." Simultaneously, the pressure head will also undergo slight deformation under the pressure of the cement paste micro-column. Based on the sinking effect and the pressure head deformation, a sinking effect model can be established, which includes the creep function of the cement paste. By using this sinking effect model to calculate pressure head data such as displacement and applied pressure, the short-term creep data of the cement paste can be determined.

[0069] In the above embodiments, a focused ion beam etching (FIBBE) device is used to etch a pre-prepared cement slurry sample to obtain cement slurry micropillars. A flat indenter from an instrumented nano-addition loading device is used to apply stress to the cement slurry micropillars, and the indenter data is recorded. The short-term creep data of the cement slurry is determined based on the indenter data. This application utilizes focused ion beam etching technology to prepare cement slurry micropillars suitable for creep testing. The flat indenter allows for precise and controllable stress application to the cement slurry micropillars at the microscopic level, thereby rapidly determining the short-term creep data of the cement slurry.

[0070] In one embodiment, the step of etching a pre-prepared cement slurry sample with a focused ion beam etching device to obtain cement slurry micropillars may include: performing multiple circumferential cutting processes on preset points on the cement slurry sample using a focused ion beam etching device to obtain cement slurry micropillars of preset size.

[0071] In this embodiment, the focused ion beam etching equipment can employ multiple circumferential cutting steps to gradually etch cement slurry micropillars with relatively ideal dimensions. Taking the fabrication of a cement slurry micropillar with a top diameter of 5 μm and a height of 10 μm as an example, the focused ion beam etching equipment uses Xe ions as the ion source, an accelerating voltage of 30 kV, and employs four circumferential cutting processes. The currents are set sequentially to 7 nA, 4 nA, 1 nA, and 0.4 nA, sequentially removing trenches of 30 μm–9 μm, 9 μm–6 μm, 6 μm–5.6 μm, and 5.6 μm–5 μm at preset points. Figure 4a As shown.

[0072] Optionally, before performing multiple circumferential cutting processes on the preset points on the cement slurry sample using a focused ion beam etching device, the embodiments of this application may further include: spraying a protective layer onto the preset points using a focused ion beam etching device.

[0073] In practical applications, after preparing the cement slurry sample, it is adhered to the sample stage of the ion etching equipment, and a conductive treatment such as carbon plating is applied to the surface of the sample. Then, the cement slurry sample is placed in the focused ion beam etching equipment, which selects the processing point and sprays a protective layer onto that point. The material of the protective layer can be tungsten. The purpose of spraying the protective layer is to prevent ion sputtering from altering the top surface shape of the cement slurry micropillar. Afterward, the focused ion beam etching equipment performs four circumferential cutting processes to obtain cement slurry micropillars of a preset size, such as... Figure 4b As shown.

[0074] In the above embodiments, a focused ion beam etching device is used to perform multiple circumferential cutting processes on preset points on the cement slurry sample to obtain cement slurry micropillars of preset dimensions. This application provides a stable and reliable preparation process and parameters for cement slurry micropillars, which can produce cement slurry micropillars of relatively ideal dimensions and improve the success rate of their preparation.

[0075] In one embodiment, the step of applying stress to the cement slurry micro-column using the flat pressure head of the instrumented nano-addition loading device may include: applying multi-stage stress loading to the top of the cement slurry micro-column using the flat pressure head of the instrumented nano-addition loading device.

[0076] Because the compressive strength of cement paste microcolumns exhibits highly variable dispersion, the load is gradually increased from low to high when stress is applied. This ensures that effective creep data is obtained for each sample. Furthermore, by employing multi-stage stress loading, the nonlinear characteristics of creep in cement paste microcolumns can be analyzed. The indentation load and time for multi-stage stress loading are as follows: Figure 5 As shown.

[0077] Optionally, the load variation of multi-stage stress loading increases exponentially. For example, the applied loads are successively 0.5mN, 1mN, 2mN, 4mN, 8mN, and 16mN. During the test, the failure load of the cement paste micro-column with a top diameter of 5μm and a height of 10μm was between 4mN and 8mN.

[0078] The stress loading process includes three stages: loading, holding, and unloading. The loading stage can last for 10 seconds, the holding stage for 180 seconds, and the unloading stage for 10 seconds. It should be noted that the duration of each stage can be set according to actual conditions.

[0079] In the above embodiments, a flat pressure head of an instrumented nano-addition loading device is used to apply multi-level stress loading to the top of the cement paste micro-column. This application's embodiment employs multi-level stress loading, which allows testing to be conducted at a suitable stress / strength ratio. This not only enables the measurement of effective short-term creep data for each sample but also allows for the analysis of the nonlinear characteristics of the cement paste micro-column creep.

[0080] In one embodiment, such as Figure 6 As shown, the pressure head data includes the pressure applied by the pressure head and the pressure head displacement. The process of determining the short-term creep data of the cement paste based on the pressure head data may include the following steps:

[0081] Step 301: Determine the amount of base settlement deformation based on the pressure applied by the pressure head and the pre-established settlement effect model.

[0082] When the cement slurry micro-column is pressurized by the indenter, the micro-bottom of the cement slurry sinks into the substrate. Simultaneously, the indenter undergoes slight deformation due to the pressure from the cement slurry micro-column. Based on this sinking effect and indenter deformation, a sinking effect model can be established. This model decomposes the indenter displacement into micro-column deformation, substrate sinking deformation, and indenter deformation. Furthermore, this sinking effect model includes a mapping relationship between the pressure applied by the indenter and the substrate sinking deformation.

[0083] During the application of pressure to the cement slurry micro-column, an instrumented nano-addition loading device records pressure and displacement data of the indenter. Then, by substituting the applied pressure into the aforementioned mapping relationship, the amount of subsidence deformation of the base can be determined.

[0084] Step 302: Determine the deformation of the indenter based on the pressure applied by the indenter and the sinking effect model.

[0085] The subsidence effect model can also include a mapping relationship between the pressure applied by the indenter and the deformation of the indenter. By substituting the pressure applied by the indenter into this mapping relationship, the deformation of the indenter can be determined.

[0086] Step 303: Determine the micro-column deformation based on the indenter displacement, the base settlement deformation, and the indenter deformation.

[0087] The subsidence effect model decomposes the indenter displacement into micro-column deformation, base subsidence deformation, and indenter deformation, as shown in formula (1):

[0088] δ measure =δ pillar +δ sub +δ indenter -----------------------(1)

[0089] Where, δ measure For the displacement of the pressure head, δ pillar δ represents the deformation of the micro-column. sub δ represents the base settlement deformation. indenter For example, the deformation of the indenter Figure 7 As shown.

[0090] After determining the displacement of the indenter, the amount of subsidence deformation of the base and the amount of indenter deformation, the amount of micro-column deformation can be determined according to formula (1).

[0091] Step 304: Determine the short-term creep data of the cement paste microcolumn based on the pressure applied by the pressure head, the deformation of the microcolumn, and the settling effect model.

[0092] The subsidence effect model can also include a mapping relationship between the microcolumn deformation and the pressure applied by the indenter and the specific creep flexibility of the cement paste microcolumn. After determining the pressure applied by the indenter and the microcolumn deformation, substituting the pressure applied by the indenter and the microcolumn deformation into this mapping relationship allows us to determine the specific creep flexibility of the cement paste microcolumn, thus obtaining the short-term creep data of the cement paste microcolumn.

[0093] like Figure 8a As shown in the figure, the horizontal axis represents the indentation head displacement, and the vertical axis represents the indentation head load. During the multi-stage stress loading process, the indentation head load is gradually increased. Each stress loading stage includes three phases: loading, holding, and unloading. The figure shows that the cement paste micro-column failed in the 5th test cycle, with a maximum load of 6.35 mN at failure.

[0094] like Figure 8b As shown in the figure, the horizontal axis represents the holding time, and the vertical axis represents the specific creep compliance. In this figure, the specific creep compliance measured at 180s from the first test cycle (head load of 0.5mN) is too high. This is because the contact between the indenter and the cement paste micro-column was insufficient during the initial loading, resulting in an inflated creep test result. Such results can be discarded in subsequent short-term creep data analysis.

[0095] In the above embodiments, the base settlement deformation is determined based on the pressure applied by the indenter and a pre-established settlement effect model; the indenter deformation is determined based on the pressure applied by the indenter and the settlement effect model; the micro-column deformation is determined based on the indenter displacement, base settlement deformation, and indenter deformation; and the short-term creep data of the cement paste micro-column is determined based on the pressure applied by the indenter, micro-column deformation, and settlement effect model. In this embodiment, the indenter displacement is decomposed into micro-column deformation, base settlement deformation, and indenter deformation. Thus, the short-term creep data of the cement paste can be determined based on the applied pressure and indenter displacement, reducing the difficulty of characterizing the creep behavior of cement paste micro-columns.

[0096] In one embodiment, the step of determining the short-term creep data of cement paste microcolumns based on the pressure applied by the indenter, the microcolumn deformation, and the subsidence effect model may include: substituting the pressure applied by the indenter and the microcolumn deformation into the first relation of the subsidence effect model to calculate the specific creep compliance, thereby obtaining the short-term creep data of the cement paste microcolumns.

[0097] The first relationship includes the correspondence between the micro-column deformation amount and the micro-column deformation flexibility, the pressure applied by the pressure head, the initial height of the cement paste micro-column and the planar cross-sectional area, as shown in formula (2).

[0098]

[0099] Where, δ pillar C represents the deformation of the micro-column. pillarThe flexibility related to the deformation of the cement paste microcolumn, i.e., the microcolumn deformation flexibility, is given by F, where F is the pressure applied by the indenter, H0 is the initial height of the cement paste microcolumn, and A... P The cross-sectional area of ​​the cement slurry micro-column can be half the sum of the top and bottom areas, or the area of ​​the cross-section at half the height of the cement slurry micro-column.

[0100] Micro-column deformation compliance C pillar Analogous to the creep function J(t, t') obtained in the uniaxial creep test of concrete, the deformation flexibility of the micro-column can be determined based on the Young's modulus and specific creep flexibility of the cement paste micro-column, as shown in formula (3).

[0101]

[0102] Among them, E pillar C(t) represents the Young's modulus of the cement paste micro-column, and C(t) represents the specific creep flexibility of the cement paste micro-column.

[0103] The cross-sectional area of ​​the cement slurry micro-column can be determined based on the top and bottom diameters of the cement slurry micro-column, as shown in formula (4).

[0104]

[0105] Among them, D top D is the top diameter of the cement paste micro-column. bottom The bottom diameter of the cement paste micro-column is, for example... Figure 7 As shown.

[0106] After determining the pressure applied by the indenter and the deformation of the micro-column, the pressure applied by the indenter and the deformation of the micro-column are substituted into the above formula for calculation to obtain the specific creep flexibility of the cement paste micro-column. The calculated specific creep flexibility of the cement paste micro-column is used as the short-term creep data of the cement paste micro-column.

[0107] In the above embodiments, the pressure applied by the indenter and the deformation of the microcolumn are substituted into the first relationship of the subsidence effect model to calculate the specific creep compliance, thereby obtaining the short-term creep data of the cement paste microcolumn. This application provides a formula for calculating the deformation of the microcolumn, which can more accurately characterize the short-term creep behavior of the cement paste microcolumn.

[0108] In one embodiment, the step of determining the base settlement deformation based on the pressure applied by the indenter and the pre-established settlement effect model may include: substituting the pressure applied by the indenter into the second relationship of the settlement effect model to calculate the deformation and obtain the base settlement deformation.

[0109] The second relationship includes the correspondence between the amount of base settlement deformation and the base deformation flexibility and the pressure applied by the indenter, as shown in formula (5).

[0110] δ sub =C Sneddon_base F---------------------------------(5)

[0111] Where, δ sub C represents the base settlement deformation. Sneddon_base The compliance related to substrate deformation, i.e., substrate deformation compliance, is represented by F, which is the pressure applied by the indenter.

[0112] Considering that the cement slurry micro-column is a rigid cylinder and the cement slurry substrate is an elastic half-space, the substrate deformation flexibility can be determined based on the contact area between the cement slurry micro-column and the substrate, the Young's modulus and Poisson's ratio of the substrate, as shown in formula (6).

[0113]

[0114] Among them, C Sneddon_base For the base deformation compliance, A base E represents the contact area between the cement paste micro-column and the substrate. base Young's modulus based on v base Poisson's ratio with a base of 1.

[0115] After determining the pressure applied by the indenter, substitute the applied pressure into the above formula to calculate the deformation amount and obtain the base settlement deformation amount.

[0116] In the above embodiments, the pressure applied by the pressure head is substituted into the second relationship of the settlement effect model to calculate the deformation, thereby obtaining the settlement deformation of the base. This application provides a formula for calculating the settlement deformation of the base, supporting the subsequent determination of the short-term creep behavior of cement paste microcolumns.

[0117] In one embodiment, the step of determining the deformation of the indenter based on the pressure applied by the indenter and the sinking effect model may include: substituting the pressure applied by the indenter into the third relation of the sinking effect model to calculate the deformation, thereby obtaining the deformation of the indenter.

[0118] The third relationship includes the correspondence between the indenter deformation amount, the indenter deformation compliance, and the pressure applied by the indenter, as shown in formula (7).

[0119] δ indenter =C Sneddon_ind F--------------------------(7)

[0120] Where, δ indenter C represents the deformation of the indenter. Sneddon_ind F represents the compliance related to indenter deformation, i.e., indenter deformation compliance, where F is the pressure applied by the indenter.

[0121] The flexibility of the indenter can be determined based on the top surface area of ​​the cement paste micro-column, the Young's modulus of the indenter, and the Poisson's ratio, as shown in formula (8).

[0122]

[0123] Among them, C Sneddon_ind For the indenter deformation compliance, A top E represents the top area of ​​the cement paste micro-column. ind v is the Young's modulus of the indenter. ind is the Poisson's ratio of the pressure head.

[0124] After determining the pressure applied by the indenter, substitute the applied pressure into the above formula to calculate the deformation amount and obtain the deformation amount of the indenter.

[0125] In the above embodiments, the pressure applied by the indenter is substituted into the third relation of the subsidence effect model to calculate the deformation, thus obtaining the indenter deformation. This application provides a formula for calculating the indenter deformation, supporting the subsequent determination of the short-term creep behavior of cement paste microcolumns.

[0126] Based on the above embodiments, a coefficient ψ(t) can be defined to quantify the ratio of the micro-column deformation to the total deformation (head displacement). Assuming the cement slurry micro-column is a purely elastic material, it can be found that ψ(t) is a constant value that does not change with time, as shown in the following formula (9).

[0127]

[0128] Where, δ pillar δ represents the deformation of the micro-column. measure E represents the displacement of the pressure head. pillar Let F be the Young's modulus of the cement paste micro-column, F be the pressure applied by the indenter, H0 be the initial height of the cement paste micro-column, and A be the initial height of the cement paste micro-column. P C is the cross-sectional area of ​​the cement paste micro-column. Sneddon_base For the substrate deformation compliance, C Sneddon_ind For the indenter deformation compliance, D top D is the top diameter of the cement paste micro-column. bottom E represents the bottom diameter of the cement paste micro-column. base Young's modulus based on v base Poisson's ratio with basis, E ind v is the Young's modulus of the indenter. ind is the Poisson's ratio of the pressure head.

[0129] Substituting D into the above formula top =5μm, cone angle θ=3°, H0=10μm, E pillar =E base=30Gpa, v base =0.24, E ind =1141GPa, v ind =0.07, from which we can calculate ψ(t) = 72.3%.

[0130] It should be noted that the half-space material (cement paste substrate) in the above model is elastic, but the hardened cement paste is a viscoelastic material. To account for the settling effect in the analytical method, an approximation can be made, that is, E in formula (9) is... base Replace with 1 / C pillar This will take the sinking effect into account to the greatest extent. Accordingly, the derivation of ψ(t) is shown in Equation (10).

[0131]

[0132] Where, δ pillar δ represents the deformation of the micro-column. measure E represents the displacement of the pressure head. pillar Let F be the Young's modulus of the cement paste micro-column, F be the pressure applied by the indenter, H0 be the initial height of the cement paste micro-column, and A be the initial height of the cement paste micro-column. P C is the cross-sectional area of ​​the cement paste micro-column. Sneddon_base For the substrate deformation compliance, C Sneddon_ind For the indenter deformation compliance, D top D is the top diameter of the cement paste micro-column. bottom E represents the bottom diameter of the cement paste micro-column. base Young's modulus based on v base Poisson's ratio with basis, E ind v is the Young's modulus of the indenter. ind is the Poisson's ratio of the pressure head.

[0133] As can be seen from formula (10), although the coefficient ψ(t) changes with time, the change is small. Therefore, 72.3% of the displacement of the pressure head can be taken as the deformation of the micro-column.

[0134] In one embodiment, such as Figure 9 As shown, a method for determining the creep of cement paste is provided, which may include the following steps:

[0135] Step 401: Prepare cement slurry samples.

[0136] Step 402: A protective layer is sprayed onto the preset points on the cement slurry sample using a focused ion beam etching device, and the preset points on the cement slurry sample are subjected to multiple circumferential cutting processes to obtain cement slurry micropillars of preset size.

[0137] Step 403: Using an instrumented nano-addition loading device, a flat pressure head is used to apply multi-level stress to the top of the cement slurry micro-column, and the pressure head data is recorded.

[0138] Among them, the load variation of multi-stage stress loading increases exponentially; each stage of stress loading includes three phases: loading, holding, and unloading. Indenter data includes the pressure applied by the indenter and the displacement of the indenter.

[0139] Step 404: Substitute the pressure applied by the pressure head into the second relation of the subsidence effect model to calculate the deformation amount and obtain the subsidence deformation amount of the base.

[0140] The second relationship includes the correspondence between the amount of subsidence deformation and the subsidence flexibility, and the pressure applied by the pressure head; the subsidence flexibility is determined based on the contact area between the cement paste micro-column and the subsidence, the Young's modulus of the subsidence, and Poisson's ratio.

[0141] Step 405: Substitute the pressure applied by the indenter into the third relation of the subsidence effect model to calculate the deformation amount and obtain the deformation amount of the indenter.

[0142] The third relationship includes the correspondence between the indenter deformation amount, the indenter deformation flexibility, and the pressure applied by the indenter. The indenter deformation flexibility is determined based on the top area of ​​the cement paste micro-column, the Young's modulus of the indenter, and the Poisson's ratio.

[0143] Step 406: Determine the micro-column deformation based on the indenter displacement, the base settlement deformation, and the indenter deformation.

[0144] Step 407: Substitute the pressure applied by the pressure head and the deformation of the micro-column into the first relation of the subsidence effect model to calculate the specific creep compliance, and obtain the short-term creep data of the cement paste micro-column.

[0145] The first relationship includes the correspondence between the micro-column deformation and the micro-column deformation flexibility, the pressure applied by the pressure head, the initial height of the cement slurry micro-column, and the planar cross-sectional area; the micro-column deformation flexibility is determined based on the Young's modulus and specific creep flexibility of the cement slurry micro-column; the planar cross-sectional area of ​​the cement slurry micro-column is determined based on the top diameter and bottom diameter of the cement slurry micro-column.

[0146] Given the complex and variable microstructure of cement paste, this application proposes a stable and reliable preparation process and parameters for cement paste micropillars. Since cement paste is a multiphase material, the compressive strength of the micropillars is unpredictable and exhibits significant dispersion. Therefore, this application proposes a specific creep testing regime to ensure that the creep test is conducted at a suitable stress / strength ratio, ranging from 0.3 to 0.6. Because the micropillars experience a "sinking effect" under axial compression, quantifying the creep deformation becomes complex. Therefore, this application proposes a calculation formula that accurately quantifies the deformation caused by the "sinking effect," thereby establishing the true stress-strain relationship of the micropillars in the creep test.

[0147] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0148] In one embodiment, such as Figure 1 As shown, this application provides a cement slurry creep testing system. The system includes a focused ion beam etching device 101, an instrumented nano-addition loading device 102, and a computer device 103; the focused ion beam etching device 101 is used to etch a pre-prepared cement slurry sample to obtain cement slurry micropillars; the instrumented nano-addition loading device 102 is used to apply stress to the cement slurry micropillars through a flat indenter and record the indenter data; the computer device 103 is used to determine the short-term creep data of the cement slurry based on the indenter data.

[0149] In this embodiment, a focused ion beam etching device 101 etches a pre-prepared cement slurry sample to obtain cement slurry micropillars; an instrumented nano-addition loading device 102 applies stress to the cement slurry micropillars using a flat indenter and records the indentation data. A computer device 103 calculates the indentation data using the formulas in the above embodiment to determine the short-term creep data of the cement slurry.

[0150] The aforementioned computer device 103 can be a terminal, and its internal structure diagram can be as follows: Figure 10As shown, the computer device includes a processor, memory, input / output interface, communication interface, display unit, and input device. The processor, memory, and input / output interface are connected via a system bus, and the communication interface, display unit, and input device are also connected to the system bus via the input / output interface. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The input / output interface is used for exchanging information between the processor and external devices. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it implements a method for measuring the creep of cement slurry. The display unit is used to form a visually visible image and can be a display screen, projection device, or virtual reality imaging device. The display screen can be an LCD screen or an e-ink screen. The input device of the computer device can be a touch layer covering the display screen, or buttons, trackballs, or touchpads set on the casing of the computer device, or external keyboards, touchpads, or mice, etc.

[0151] Those skilled in the art will understand that Figure 10 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0152] In one embodiment, a non-transitory computer-readable storage medium including instructions is also provided, such as a memory including instructions, which can be executed by a processor of computer device 103 to complete the step of determining short-term creep data of cement paste based on pressure head data. The non-transitory computer-readable storage medium may be a ROM, random access memory (RAM), CD-ROM, magnetic tape, floppy disk, or optical data storage device, etc.

[0153] In one embodiment, a computer program product is also provided, which, when executed by a processor, can perform the steps described above for determining short-term creep data of cement paste based on head data. The computer program product includes one or more computer instructions. When these computer instructions are loaded and executed on a computer, some or all of the above-described methods can be implemented, in whole or in part, according to the processes or functions described in the embodiments of this application.

[0154] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0155] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0156] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for determining the creep of cement paste, characterized in that, The method includes: A pre-prepared cement slurry sample was etched using a focused ion beam etching device to obtain cement slurry micropillars; Stress was applied to the cement slurry micro-column using a flat pressure head of an instrumented nano-addition loading device, and the pressure head data was recorded. The short-term creep data of the cement paste are determined based on the pressure head data; The pressure head data includes the pressure applied by the pressure head and the pressure head displacement. Determining the short-term creep data of the cement paste based on the pressure head data includes: The deformation is calculated by substituting the pressure applied by the indenter into the second relationship of the subsidence effect model; wherein, the second relationship includes the correspondence between the subsidence deformation of the base and the base deformation flexibility and the pressure applied by the indenter; the base deformation flexibility is determined based on the contact area between the cement paste micro-column and the base, the Young's modulus and Poisson's ratio of the base; The deformation amount is calculated by substituting the pressure applied by the indenter into the third relation of the subsidence effect model; wherein, the third relation includes the correspondence between the deformation amount of the indenter, the deformation compliance of the indenter, and the pressure applied by the indenter, and the deformation compliance of the indenter is determined based on the top area of ​​the cement paste micro-column, the Young's modulus and Poisson's ratio of the indenter; The deformation of the microcolumn is determined based on the displacement of the indenter, the subsidence deformation of the base, and the deformation of the indenter. The pressure applied by the indenter and the deformation of the micro-column are substituted into the first relationship of the subsidence effect model to calculate the specific creep compliance, thereby obtaining the short-term creep data of the cement paste micro-column; wherein, the first relationship includes the correspondence between the micro-column deformation and the micro-column deformation compliance, the pressure applied by the indenter, the initial height of the cement paste micro-column, and the planar cross-sectional area; the micro-column deformation compliance is determined based on the Young's modulus and specific creep compliance of the cement paste micro-column; the planar cross-sectional area of ​​the cement paste micro-column is determined based on the top diameter and bottom diameter of the cement paste micro-column.

2. The method according to claim 1, characterized in that, The process of etching a pre-prepared cement slurry sample using a focused ion beam etching device to obtain cement slurry micropillars includes: The cement slurry sample is subjected to multiple circumferential cutting processes at preset points using the focused ion beam etching equipment to obtain cement slurry micropillars of preset size.

3. The method according to claim 2, characterized in that, Before performing multiple circumferential etching processes on the preset points on the cement slurry sample using the focused ion beam etching equipment, the method further includes: The focused ion beam etching equipment is used to spray a protective layer onto the preset points.

4. The method according to claim 1, characterized in that, The method of applying stress to the cement slurry micro-column using a flat pressure head of an instrumented nano-addition loading device includes: The instrumented nano-addition loading device is used to apply multi-stage stress loading to the top of the cement slurry micro-column.

5. The method according to claim 4, characterized in that, The load variation of the multi-stage stress loading is exponential; each stage of stress loading includes three phases: loading, holding, and unloading.

6. A system for measuring the creep of cement paste, characterized in that, The system includes a focused ion beam etching device, an instrumented nano-addition loading device, and a computer device; The focused ion beam etching equipment is used to etch a pre-prepared cement slurry sample to obtain cement slurry micropillars. The instrumented nano-addition loading device is used to apply stress to the cement slurry micro-columns through a flat pressure head and record the pressure head data; The computer device is used to determine short-term creep data of cement paste according to the method of any one of claims 1-5.

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