A method of determining the operable time of a cement slurry

Abstract

The present application belongs to the technical field of cement grouting, and particularly relates to a method for determining the operable time of cement slurry. The present application is based on the test data of apparent viscosity of cement slurry with different water-cement ratios under different temperature and stirring time conditions and mechanical strength of stone body, combined with three-dimensional curved surface data analysis fitting method, to construct temperature-stirring time-apparent viscosity function relationship model and temperature-stirring time-corresponding age compressive strength function relationship model. Then, the longest stirring time for ensuring the flow performance of slurry and the longest stirring time for ensuring the mechanical strength of stone body with corresponding age are compared, and the smaller value is taken as the best operable time of slurry or the slurry abandonment time. The method provided by the present application can be used to guide the grouting engineering design, quickly determine, optimize and pre-evaluate the grouting construction parameters, and can increase the purposiveness of grouting design and construction, and effectively improve the quality of on-site grouting construction.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cement grouting, and particularly relates to a method for determining the operable time of cement slurry. BACKGROUND

[0002] Cement grouting is the most mature anti-seepage reinforcement technology, which has been widely used in water conservancy, transportation, mineral industry and other industries. The engineering practice experience is rich, the grouting process and the corresponding technology are mature, and the performance difference of the same cement material is small, which is convenient for the application of material and corresponding engineering experience. Cement slurry is a suspension of water and cement particles, with high particle fineness. High-speed mixers (stirring speed ≥ 1200 r / min) are used for forced stirring and dispersion during slurry preparation, and then the slurry is stored for use. During the grouting construction process, the slurry needs to be continuously stirred at a low speed (stirring speed of about 100 r / min) to prevent the slurry from precipitating and to maintain the dispersion stability and uniformity of the slurry. However, there are few studies on the influence of long-term slow stirring on the flow performance of cement slurry and the mechanical properties of the solidified body, and the corresponding rules are not clear, which leads to difficulties in determining the operable time or discarding time of the slurry in grouting engineering. According to the relevant engineering experience, the Technical Code for Cement Grouting Construction of Hydraulic Structures (SL / T 62-2020) stipulates that the time from preparation to use of ordinary cement slurry should not be greater than 4 h.

[0003] According to the analysis of literature and research results, low temperature (≤10℃) or high temperature (≥35℃) has a significant influence on the construction performance of cement slurry. Many scholars have conducted sufficient research on the physical and mechanical properties of cement-based and modified materials under low temperature or high temperature conditions. Based on the research results and grouting engineering experience, the Technical Code for Cement Grouting Construction of Hydraulic Structures (SL / T 62-2020) stipulates that the temperature of ordinary cement slurry should be maintained at 5-40℃. When the construction environment temperature is too high (≥35℃) or too low (≤5℃), special temperature control measures should be taken during grouting. Most parts of China belong to subtropical and temperate monsoon climate, and the temperature in spring, summer and autumn mainly ranges from 10-35℃. For the temperature range of 10-35℃, the inhibition or promotion effect on the hydration reaction of cement slurry is not as significant as that under low temperature or high temperature conditions, because it meets the temperature conditions required for cement slurry hydration and solidification. For construction cost reasons, the influence of this temperature range on the construction performance of cement slurry is generally not considered during on-site grouting construction, and temperature control measures are not used. The influence of the corresponding temperature change on the performance of the slurry has not been specially studied.

[0004] The stirring time and the temperature change in the temperature range of 10 DEG C to 35 DEG C have influences on the flow performance of the cement slurry and the mechanical strength of the stone body, the influences of the stirring time and the temperature on the construction performance of the slurry will be more obvious, and it is very likely to cause the rheological property of the slurry to increase greatly and the mechanical strength of the stone body to decrease greatly, and then the cement grouting construction quality is seriously affected. At present, the influences of the stirring time and the temperature on the construction performance of the slurry have not been studied, the performance of the cement slurry in the actual grouting process cannot be truly reflected, the grouting design and construction are blind to a certain extent, and the grouting construction parameters are not suitable for the site engineering, and the workload of the site grouting test is greatly increased. SUMMARY

[0005] Therefore, the present application aims to provide a method for determining the operable time of cement slurry, which can consider the influences of temperature and stirring time on the construction performance of the slurry, so as to determine the more accurate operable time of the slurry.

[0006] In order to achieve the above object, the present application provides a method for determining the operable time of cement slurry, comprising the following steps:

[0007] After the cement and water are mixed, the cement slurry to be tested under different temperatures and stirring times is obtained by stirring under different temperatures and stirring times;

[0008] The apparent viscosity of the cement slurry to be tested under different temperatures and stirring times is tested, the temperature and the stirring time are taken as independent variables, the apparent viscosity is taken as dependent variable, a function relationship model between the temperature, the stirring time and the apparent viscosity under the water-cement ratio is constructed based on three-dimensional surface fitting, and the water-cement ratio of the cement slurry to be tested is known;

[0009] The temperature-stirring time-apparent viscosity function relationship model is shown as formula I:

[0010]

[0011] In formula I, η0, B, E, H, T ηc , t ηc , D and G are constants obtained based on three-dimensional surface fitting;

[0012] T is the temperature, the unit is DEG C; t is the continuous stirring time of the cement slurry, the unit is min; and η is the apparent viscosity;

[0013] The cement slurry to be tested is cured for different ages, the stone body corresponding to the temperature and the stirring time is obtained, the compressive strength of the stone body is tested, the temperature and the stirring time are taken as independent variables, the compressive strength is taken as dependent variable, a function relationship model between the temperature, the stirring time and the compressive strength is constructed based on three-dimensional surface fitting function, and the temperature-stirring time-compressive strength relationship model is shown as formula II:

[0014]

[0015] In formula II, p is the compressive strength; p0, A, T c ηc and C are constants based on three-dimensional surface fitting;

[0016] According to the predetermined temperature, the predetermined apparent viscosity and formula I, a first stirring time of the to-be-tested slurry under the predetermined apparent viscosity is obtained;

[0017] According to the predetermined temperature, the predetermined compressive strength and formula II, a second stirring time of the to-be-tested slurry under the predetermined compressive strength is obtained;

[0018] Taking the smaller value of the first stirring time and the second stirring time as the operable time of the cement slurry.

[0019] Preferably, the temperature is 10-35℃.

[0020] Preferably, the to-be-tested cement slurry comprises cement and water; and the water-cement ratio is 0.5-1:1.

[0021] Preferably, when the water-cement ratio of the to-be-tested cement slurry is 0.8:1, the temperature-stirring time-apparent viscosity function relationship model is:

[0022]

[0023] Preferably, when the water-cement ratio of the to-be-tested cement slurry is 0.8:1, the temperature-stirring time-compressive strength relationship model is:

[0024]

[0025] The present application provides a method for determining the operable time of a cement slurry, comprising the following steps: mixing cement and water, and then stirring under different temperatures and stirring times to obtain to-be-tested cement slurries under different temperatures and stirring times;

[0026] Testing the apparent viscosities of the to-be-tested cement slurries under different temperatures and stirring times, taking the temperature and the stirring time as independent variables and the apparent viscosity as a dependent variable, constructing a function relationship model between the temperature, the stirring time and the apparent viscosity under the water-cement ratio based on three-dimensional surface fitting, the water-cement ratio of the to-be-tested cement slurry being known; the temperature-stirring time-apparent viscosity function relationship model is shown in formula I:

[0027] In formula I, η0, B, E, H, T ηc ηc ​​, D and G are constants based on three-dimensional surface fitting; T is temperature, unit is ℃; t is the cement paste continuous stirring time, unit is min; η is apparent viscosity; the cement paste to be measured is cured for different ages to obtain the corresponding temperature and stirring time of the stone body; the compressive strength of the stone body is tested, the temperature and stirring time are taken as independent variables, and the compressive strength is taken as dependent variable, a function relationship model between temperature, stirring time and compressive strength is constructed based on three-dimensional surface fitting function, and the temperature-stirring time-compressive strength relationship model is shown as formula II: In formula II, p is the compressive strength; p0, A, T c , t c , and C are constants based on three-dimensional surface fitting; the first stirring time of the slurry to be measured under the predetermined apparent viscosity is obtained according to the predetermined temperature, the predetermined apparent viscosity and formula I; the second stirring time of the slurry to be measured under the predetermined compressive strength is obtained according to the predetermined temperature, the predetermined compressive strength and formula II; the smaller value of the first stirring time and the second stirring time is taken as the operable time of the cement slurry. The present application is based on the corresponding water-cement ratio cement slurry apparent viscosity and stone body mechanical strength test data under different temperature and stirring time conditions, and a three-dimensional surface data analysis fitting method is combined to construct a temperature-stirring time-apparent viscosity function relationship model and a temperature-stirring time-corresponding age compressive strength function relationship model. Then, the longest stirring time for ensuring the flow performance of the slurry and the longest stirring time for ensuring the mechanical strength of the corresponding age stone body are compared, and the smaller value of the two is taken as the best operable time or the slurry abandonment time of the slurry. The method provided by the present application can be used to guide the grouting engineering design, quickly determine the grouting construction parameters, optimize and pre-evaluate the grouting effect, increase the purposiveness of grouting design and construction, effectively improve the quality of on-site grouting construction, greatly reduce the amount of grouting construction site test engineering, and is beneficial to shorten the construction period and save engineering investment. BRIEF DESCRIPTION OF DRAWINGS

[0028] Fig. 1 The temperature-stirring time-apparent viscosity function relationship model of the water-cement ratio 0.8:1 slurry is shown as formula I:

[0029] Fig. 2 The temperature-stirring time-7d compressive strength function relationship model of the water-cement ratio 0.8:1 slurry is shown as formula II. DETAILED DESCRIPTION

[0030] The present application provides a method for determining the operable time of cement slurry, which comprises the following steps:

[0031] After the cement and water are mixed, the cement paste to be measured is stirred under different temperatures and stirring times to obtain the cement paste to be measured under different temperatures and stirring times;

[0032] Test the apparent viscosity of the to-be-tested cement slurry under different temperatures and stirring times, take the temperature and the stirring time as independent variables, and take the apparent viscosity as dependent variable, construct a function relation model between the temperature, the stirring time and the apparent viscosity under the water-cement ratio based on three-dimensional surface fitting, wherein the water-cement ratio of the to-be-tested cement slurry is known;

[0033] The temperature-stirring time-apparent viscosity function relation model is shown as formula I:

[0034]

[0035] In formula I, η0, B, E, H, T ηc , t ηc , D and G are constants obtained based on three-dimensional surface fitting;

[0036] T is the temperature, the unit is ℃; t is the continuous stirring time of the cement slurry, the unit is min; η is the apparent viscosity;

[0037] Cure the to-be-tested cement slurry for different ages to obtain the corresponding temperature and stirring time of the stone body; test the compressive strength of the stone body, take the temperature and the stirring time as independent variables, and take the compressive strength as dependent variable, construct a function relation model between the temperature, the stirring time and the compressive strength based on three-dimensional surface fitting function, and the temperature-stirring time-compressive strength relation model is shown as formula II:

[0038]

[0039] In formula II, p is the compressive strength; p0, A, T c , t c and C are constants obtained based on three-dimensional surface fitting;

[0040] According to the predetermined temperature, the predetermined apparent viscosity and formula I, the first stirring time of the to-be-tested slurry under the predetermined apparent viscosity is obtained.

[0041] According to the predetermined temperature, the predetermined compressive strength and formula II, the second stirring time of the to-be-tested slurry under the predetermined compressive strength is obtained.

[0042] Take the smaller value of the first stirring time and the second stirring time as the operable time of the cement slurry.

[0043] The cement and water are mixed, and then stirred under different temperatures and stirring times to obtain the to-be-tested cement slurry under different temperatures and stirring times;

[0044] Test the apparent viscosity of the to-be-tested cement slurry under different temperatures and stirring times, take the temperature and stirring time as independent variables, and take the apparent viscosity as dependent variable, construct a function relationship model between the temperature, stirring time and apparent viscosity under the water-cement ratio based on three-dimensional surface fitting, and the water-cement ratio of the to-be-tested cement slurry is known.

[0045] In the present application, the water-cement ratio is preferably 0.5-1:1, and more preferably 0.8:1.

[0046] In the present application, the temperature is preferably 10-35℃. In the embodiments of the present application, it is specifically preferred to be 10℃, 15℃, 20℃, 25℃, 30℃ and 35℃.

[0047] In the embodiments of the present application, the stirring time is specifically preferred to be 0 min, 30 min, 60 min, 90 min, 120 min, 150 min, 180 min, 210 min and 240 min. In the present application, the stirring speed is preferably 100 rpm.

[0048] In the present application, the apparent viscosity is obtained by a rotary viscometer.

[0049] In the present application, the temperature-stirring time-apparent viscosity function relationship model is shown in formula I.

[0050]

[0051] In formula I, η0, B, E, H, T ηc , t ηc , D and G are constants obtained based on three-dimensional surface fitting;

[0052] T is the temperature, unit: ℃; t is the continuous stirring time of the cement slurry, unit: min; η is the apparent viscosity;

[0053] In the present application, the stirring slurry obtained at different temperatures and different stirring times is cured for different ages to obtain the stone body corresponding to the temperature and stirring time; the compressive strength of the stone body is tested, the temperature and stirring time are taken as independent variables, and the compressive strength is taken as dependent variable, a function relationship model of the temperature, stirring time and compressive strength is constructed based on three-dimensional surface fitting function, and the temperature-stirring time-compressive strength relationship model is shown in formula II.

[0054]

[0055] In formula II, p is the compressive strength; p0, A, T c , t c and C are constants obtained based on three-dimensional surface fitting.

[0056] The present application obtains the first stirring time of the slurry to be tested under a predetermined apparent viscosity according to the predetermined temperature, the predetermined apparent viscosity and formula I, obtains the second stirring time of the slurry to be tested under a predetermined compressive strength according to the predetermined temperature, the predetermined compressive strength and formula II, and takes the smaller value of the first stirring time and the second stirring time as the operable time of the cement slurry.

[0057] In order to further illustrate the present application, the schemes of the present application are described in detail below in combination with examples, but they should not be understood as limiting the protection scope of the present application.

[0058] Example 1

[0059] (1) The test conditions of different temperatures and stirring times (see Table 1) were set in the temperature range of 10-35℃, and the Qilianshan PO.42.5 cement slurry with a water-cement ratio of 0.8:1 was selected for testing, and the cement slurry was numbered according to Table 1.

[0060] Table 1 Test scheme of temperature and stirring time

[0061]

[0062] (2) The cement slurry with a water-cement ratio of 0.8:1 was prepared, the water temperature for preparing the slurry was the same as the corresponding set environment temperature, after the preparation of the slurry was completed, the stirring speed of the stirrer was adjusted to 100 r / min, and the stirring time was started to be counted, and the prepared slurry was stirred according to the stirring time set in the corresponding scheme number, to simulate the slurry storage process during the field grouting construction.

[0063] (3) During the continuous stirring, the slurry was sampled according to the stirring time set in the corresponding scheme number, the sample was taken by using a special test cup for a rotary viscometer, the sample amount met the test requirements, the rotary viscometer speed was set to 600 r / min, and the viscosity value of the cement slurry at this speed was tested The apparent viscosity calculation formula of the cement slurry is The apparent viscosity of the slurry under the corresponding stirring time was obtained, and the corresponding test data are shown in Table 2.

[0064] Table 2 Test data of temperature-stirring time-apparent viscosity of slurry with a water-cement ratio of 0.8:1

[0065]

[0066] (4) After the slurry has been continuously stirred for the specified stirring time for the corresponding numbered test, compressive strength specimens are cast using the corresponding slurry. The compressive strength specimens are cuboids with dimensions of 40mm × 40mm × 160mm. Six specimens are tested for each group of tests, and the arithmetic mean of the six specimens is taken as the compressive strength value of that group of specimens. Under the temperature conditions specified for the corresponding numbered test, the relative humidity of the air is maintained at ≥90%, and the specimens are cured for 7 days. The 7-day compressive strength of the slurry aggregate is tested using a pressure tester, and the 7-day compressive strength of the slurry aggregate under the set stirring time is obtained, i.e., the temperature ~ stirring time ~ 7-day compressive strength test data. The corresponding test data are shown in Table 3 below.

[0067] Table 3. Water-cement ratio 0.8:1 slurry temperature-stirring time-7d compressive strength test data

[0068]

[0069] (5) Based on experimental data and numerical analysis software, a spatial distribution was established with temperature and stirring time as independent variables and apparent viscosity of slurry and compressive strength of stone bodies at corresponding ages as dependent variables. The experimental data were then fitted using a three-dimensional fitting function.

[0070] (6) By comparing the fitting error and the surface type, the temperature-stirring time-apparent viscosity function relationship model and the temperature-stirring time-corresponding age compressive strength function relationship model are selected. For cement slurry with a water-cement ratio of 0.8:1, the temperature-stirring time-apparent viscosity function relationship is the ExtremeCum function, and the fitting error R0 is 1. 2 It is 0.99048;

[0071] The temperature-stirring time-7d compressive strength function is a Gaussian 2D function with a fitting error R0. 2 The value is 0.99527; the corresponding function model is as follows: Figs. 1-2 As shown. Fig. 1 The corresponding function expression is:

[0072]

[0073] Fig. 2 The corresponding function expression is:

[0074]

[0075] (7) Based on numerical analysis software and programming methods, write a function solving module to solve the corresponding function relationship model; by solving the function relationship model, calculate the slurry fluidity and the compressive strength performance index of the stone body at the corresponding curing age under the actual temperature and stirring time conditions at the engineering site.

[0076] Taking five working conditions (13℃, 17℃, 22℃, 26℃, and 33℃) as examples, and mixing times of 60min, 90min, 105min, 120min, 135min, 150min, 165min, and 180min respectively, i.e., T = 13, 22, 26, 33, t = 60, 90, 105, 120, 135, 150, 165, 180, the apparent viscosity and 7-day compressive strength of the slurry were calculated by substituting these values ​​into the function solver. The corresponding construction performance indicators are shown in Table 4 (η is in mPa·s, p is in MPa).

[0077] Table 4 Calculated values ​​of apparent viscosity and 7-day compressive strength of 0.8:1 slurry

[0078]

[0079]

[0080] (8) By comparing the longest stirring time required to ensure the fluidity of the slurry with the corresponding water-cement ratio and the longest stirring time required to ensure the mechanical strength of the corresponding aggregate under corresponding temperature conditions, the smaller of the two values ​​is taken as the optimal workable time and disposal time of the slurry. The apparent viscosity of the cement slurry is controlled at 50 mPa·s, and the longest stirring time required to ensure the fluidity of the slurry with the corresponding water-cement ratio is the stirring time when the apparent viscosity of the cement slurry is close to 50 mPa·s. The 7-day compressive strength loss rate of the aggregate is controlled to be no more than 5%, and the compressive strength loss rate is the 7-day compressive strength p of the aggregate under the corresponding temperature and stirring conditions. y The 7-day compressive strength p of the stone mass in freshly prepared slurry (stirring time 0 min) under the same temperature conditions j The difference (Vp) is the ratio of the 7-day compressive strength of the newly prepared grout to the 7-day compressive strength p of the newly prepared grout. j It can be based on the relational formula The calculations were performed with t=0. The maximum mixing time required to ensure the mechanical strength of the aggregate at the corresponding water-cement ratio is reached, i.e., the mixing time during which the 7-day compressive strength loss of the aggregate does not exceed 5%. The expression for the workable time or disposal time of the slurry is as follows:

[0081] t = min(t) ηmax , t pmax )

[0082] Based on the calculation results in Table 4 above, the optimal workable time or disposal time of the slurry can be determined under five working conditions: construction temperature of 13℃, 17℃, 22℃, 26℃, and 33℃.

[0083] 13℃, t 可操作 =t 弃浆 =min(t) ηmax ,t pmax) = min(200, 165) = 165 min

[0084] 17℃, t 可操作 = t 弃浆 = min(t ηmax , t pmax ) = min(200, 165) = 165 min

[0085] 22℃, t 可操作 = t 弃浆 = min(t ηmax , t pmax ) = min(200, 150) = 150 min

[0086] 26℃, t 可操作 = t 弃浆 = min(t ηmax , t pmax ) = min(200, 135) = 135 min

[0087] 33℃, t 可操作 = t 弃浆 = min(t ηmax , t pmax ) = min(90, 120) = 120 min

[0088] Through the calculation, the apparent viscosity of the cement slurry with the water-cement ratio of 0.8:1 and the 7d compressive strength of the stone body under the conditions of the corresponding temperature and stirring time can be obtained. Based on the corresponding indexes, the grouting construction parameters such as the water-cement ratio of the slurry, the stirring time and the best operable time can be quickly determined in combination with the grouting engineering requirements, and the grouting effect can be evaluated according to the fluidity of the slurry and the mechanical strength index of the stone body, so as to increase the purposiveness of the grouting design and construction, improve the quality of the on-site grouting construction, reduce the workload of the on-site test, thereby shorten the construction period and save the engineering investment.

[0089] Although the above embodiment has made a detailed description of the present application, it is only a part of the embodiments of the present application, but not all the embodiments, and other embodiments can be obtained according to the present embodiment without creativity, and these embodiments all belong to the protection scope of the present application.

Claims

1. A method for determining the workable time of cement grout, characterized in that, Includes the following steps: After mixing cement and water, the mixture is stirred at different temperatures and stirring times to obtain cement slurry samples to be tested at different temperatures and stirring times. The water-cement ratio of the cement slurry to be tested is known. The apparent viscosity of the cement slurry to be tested is measured at different temperatures and stirring times. With temperature and stirring time as independent variables and apparent viscosity as dependent variable, a functional relationship model between temperature, stirring time and apparent viscosity at the water-cement ratio is constructed based on three-dimensional surface fitting. The temperature-stirring time-apparent viscosity function relationship model is shown in Equation I: In Equation I, η0, B, E, H, T ηc t ηc D and G are constants obtained based on three-dimensional surface fitting; T represents temperature in °C; t represents the continuous mixing time of the cement slurry in minutes. η is the apparent viscosity; The cement slurry to be tested was cured for different ages to obtain stone bodies at corresponding temperatures and mixing times. The compressive strength of the stone bodies was tested. With temperature and mixing time as independent variables and compressive strength as dependent variable, a functional relationship model between temperature, mixing time and compressive strength was constructed based on a three-dimensional surface fitting function. The temperature-mixing time-compressive strength relationship model is shown in Equation II: In Equation II, p is the compressive strength; p0, A, T c t c C and C are constants obtained based on three-dimensional surface fitting; Based on the predetermined temperature, the predetermined apparent viscosity, and Formula I, the first stirring time of the slurry to be tested at the predetermined apparent viscosity is obtained. Based on the predetermined temperature, predetermined compressive strength, and Formula II, the second stirring time of the slurry to be tested under the predetermined compressive strength is obtained; The smaller of the first mixing time and the second mixing time is taken as the workable time of the cement slurry.

2. The method according to claim 1, characterized in that, The temperature is 10–35°C.

3. The method according to claim 1, characterized in that, The cement slurry to be tested includes cement and water; the water-cement ratio is 0.5 to 1:

1.

4. The method according to claim 3, characterized in that, When the water-cement ratio of the cement slurry to be tested is 0.8:1, the temperature-stirring time-apparent viscosity function relationship model is as follows:

5. The method according to claim 3, characterized in that, When the water-cement ratio of the cement slurry to be tested is 0.8:1, the temperature-stirring time-compressive strength relationship model is as follows:

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