Cement solidification silt strength prediction method based on glue air ratio

Abstract

The application discloses a cement solidified silt strength prediction method based on a glue-air ratio, and steps include: step 1, the specific gravity of silt and a cement-based solidifying agent is determined, and the initial porosity is calculated; step 2, indoor experiments are carried out, the hydration degree of the cement-based solidifying agent under different curing ages is determined, and the volume expansion rate of the cement-based solidifying agent is calculated; step 3, the glue-air ratio of the cement solidified silt under different curing ages is calculated through the initial porosity, the hydration degree and the volume expansion rate; and step 4, the glue-air ratio is substituted into a strength prediction model, and the unconfined compressive strength of the cement solidified silt under different curing ages can be predicted. The application firstly uses the glue-air ratio to predict the strength of the cement solidified silt, without needing to carry out pretests, and can efficiently and accurately predict the strength of the cement-based material solidified silt under different proportions and curing ages, and greatly improves the prediction efficiency and accuracy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a cement solidified silt strength prediction method based on a cement-paste ratio. BACKGROUND

[0002] In the process of urban infrastructure construction, the excavated soil is often treated as waste, which not only wastes land resources, but also increases unnecessary construction costs due to transportation and storage of the soil. In fact, if these soils can be reasonably utilized, they can play an important role in many fields. High-quality soil can not only be used for roadbed filling, but also be effectively applied in many fields such as construction, environmental protection, landscape design, etc. For poor quality soil such as silt, it can be transformed into a material with practical value through appropriate pretreatment. For example, silt improved by cement-based materials not only has improved strength, but also can be applied to various engineering structures such as foundation treatment, dam construction, land improvement, etc.

[0003] Due to the significant differences in water content, particle distribution and cement content of silt between different batches, these variables have a direct impact on the mechanical properties of improved soil. At present, the unconfined compressive strength test (UCT) is an important means to evaluate the engineering applicability of improved soil, but it has high requirements for experimental conditions and resources. In order to reduce experimental costs and improve prediction efficiency, it is particularly important to develop a numerical calculation method that can predict the unconfined compressive strength of improved soil. The application of this method is not limited to roadbed filling, but can provide efficient solutions for many fields such as construction, environmental remediation, land development, etc.

[0004] In engineering practice, digital design methods based on numerical calculation have shown their wide application prospects. However, traditional methods still have room for improvement in terms of accuracy and applicability. Therefore, studying a new strength prediction method for cement-based material solidified silt not only improves the accuracy of the prediction, but also provides a solid theoretical basis for engineering practice, which has far-reaching significance. SUMMARY

[0005] In view of the problems in the prior art, the application provides a cement solidified silt strength prediction method based on a cement-paste ratio. The method defines the cement-paste ratio of cement-based material solidified silt, and proposes a solidified silt strength prediction formula with the cement-paste ratio as the only variable, which can realize rapid prediction of the strength under different proportions and different ages.

[0006] In order to achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0007] A cement solidified silt strength prediction method based on a cement-paste ratio, comprising the following specific steps:

[0008] Step 1, the specific gravity of silt and cement-based solidifying agent is determined, and then the initial porosity of the solidified silt is calculated according to the mass, volume and mixing ratio of the solidified silt;

[0009] Step 2, indoor experiments are carried out to determine the hydration degree of the cement-based solidifying agent under different curing ages, and the specific gravity under the corresponding curing age is recorded, and then the volume expansion rate of the cement-based solidifying agent is calculated;

[0010] Step 3, the initial porosity, hydration degree and volume expansion rate calculated are substituted into the glue-air ratio calculation formula, so as to obtain the glue-air ratio of the cement solidified silt under different curing ages;

[0011] Step 4, the glue-air ratio is substituted into the strength prediction model to predict the unconfined compressive strength of the cement solidified silt under different curing ages.

[0012] The strength prediction model is shown in the following formula:

[0013] q u =y0+A×e Bx

[0014] In the formula, y0, A and B are fitting parameters, q u represents the unconfined compressive strength of the solidified silt, and x represents the glue-air ratio GSR of the solidified silt;

[0015] The calculation formula of the glue-air ratio GSR is as follows:

[0016]

[0017] In the formula, m cd , W s (t), P and G cd are the addition amount (kg) of the cement-based material, the hydration degree (%), the volume expansion rate (%) and the specific gravity of the cement-based material respectively; g is the acceleration of gravity (9.8 m / s 2 ); n0 and V are the initial porosity (%) of the solidified silt and the volume (m 3 ), respectively; and γ w is the specific gravity of water (kN / m 3 ).

[0018] Further, the determination method of the hydration degree W s (t) comprises the following steps:

[0019] Step 1: After the cement-based material is mixed with water according to the standard consistency water amount, it is placed in a standard curing condition (temperature is 20±2℃, relative humidity is above 95%) for curing for 3, 7, 14, 28, 60 and 90 days;

[0020] Step 2: The cement-based material reaching the curing age is taken out, freeze-dried, crushed, and sieved through a 2mm sieve to obtain a sieved sample;

[0021] Step 3: 5g of the sieved sample at different curing ages are respectively placed in a 1000℃ muffle furnace for 2 hours, and the sample mass is measured after cooling in a dry environment, denoted as m t , t is the curing age (t = 3, 7, 14, 28, 60, 90), and the non-evaporable water weight of the cement-based material at time t is (5-m t ), and the non-evaporable water content of the cement-based material at time t is defined as L t , which is calculated using the following formula:

[0022]

[0023] Step 4: The non-evaporable water content L t (t = 3, 7, 14, 28, 60, 90) of the cement-based material at the six curing ages is fitted using the function shown in the following formula to obtain L t , which is a nonlinear function of the curing age t;

[0024]

[0025] Step 5: The non-evaporable water content L t of the cement-based material at the six curing ages obtained in Step 4 is used to predict the non-evaporable water content of the completely hydrated cement-based material, and when the non-evaporable water content change rate ΔL t is less than 0.01% / d, it is considered that the cement-based material has been completely hydrated, and the non-evaporable water content at this time is the non-evaporable water content after complete hydration, denoted as L ∞ ;

[0026] Step 6: The hydration degree W s (t) of the cement-based material at time t is calculated using the following formula:

[0027]

[0028] Further, the method for measuring the volume expansion rate P includes the following steps:

[0029] Step 1: The sieved sample is taken, and the specific gravity of the sieved sample at different curing ages is measured using the specific gravity bottle method, denoted as G t , t is the curing age (t = 3, 7, 14, 28, 60, 90);

[0030] Step 2: The sieved sample is composed of unhydrated cement-based material and hydrated cement-based material, and the proportions of unhydrated cement-based material and hydrated cement-based material are R an and R hp , respectively, calculated using the following formula:

[0031]

[0032] where γ is the mass of the fully hydrated cementitious material per unit mass of cementitious material, and its value is equal to (1+L ∞ );

[0033] Step 3: Calculate the specific gravity of the hydration product G sh according to the following formula:

[0034]

[0035] where G cd is the initial specific gravity of the cementitious material, which is determined by the specific gravity bottle method;

[0036] Step 4: Calculate the volume expansion rate P of the cementitious material when it is fully hydrated according to the following formula:

[0037]

[0038] Further, the initial porosity n0 is calculated according to the following formula:

[0039]

[0040] where V represents the total volume of the solidified silt; m cd , m s represent the mass of the cementitious material and silt in the solidified silt, respectively; G s represents the specific gravity of the silt particles, which is determined by the specific gravity bottle method; γ w ≈10kN / m 3 is the specific weight of water, g≈10×10 3 kg·m / s 2 is the acceleration of gravity.

[0041] Further, the initial values of the fitting parameters y0, A, B are-1000, 1000 and 0.1, respectively, and the correction steps are as follows:

[0042] Step 1: Take the silt and cementitious material at the construction site to prepare 6 groups of samples with different proportions or curing ages, and carry out unconfined compressive strength test after standard curing to the target age. The measured strength obtained by the test is denoted as q u,s .

[0043] Step 2: Calculate the glue-air ratio GSR and the predicted strength q u,y of the 5 groups of different proportioning samples in Step 1 according to the formula.

[0044] Step 3: Compare the measured strength q u,s with the predicted strength q u,yM value is calculated according to the following formula, and the minimum value of M is solved by using a programming solution method, and three coefficients y0, A and B are set as variable quantities, and the three parameters are solved and corrected:

[0045] M = ∑ (q u,s -q u,y (GSR) 2 .

[0046] The cement-based material solidified silt glue-air ratio (GSR) concept is innovatively proposed in the present application, aiming to quantify the strength characteristics of cement-based material solidified silt. On this basis, a prediction model based on GSR is proposed to accurately predict the unconfined compressive strength of cement-based material solidified silt. The GSR index comprehensively considers the initial porosity n0, the amount of solidification agent m cd , the volume expansion rate P and the hydration degree W s (t) and other key factors affecting the strength of solidified silt, providing a quantitative means for evaluating the synergistic effect of these factors on the unconfined compressive strength. The advantage of the prediction method is that it can accurately predict the unconfined compressive strength of cement-based material solidified silt without the need for pre-test to obtain fitting coefficients, significantly improving the professionalism and efficiency of the prediction process. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 The construction method of the prediction model in the present application.

[0048] Figure 2 The comparative results of the measured strength, the preliminary predicted strength and the final predicted strength in Example 1 of the present application.

[0049] Figure 3 The comparative results of the measured strength, the preliminary predicted strength and the final predicted strength in Example 2 of the present application. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present application will be described in detail below with reference to the examples. It should be understood that the following examples are given only for the purpose of illustration and are not intended to limit the scope of the present application. Those skilled in the art can make various modifications and substitutions to the present application without departing from the spirit and principles of the present application.

[0051] The experimental methods used in the following examples are conventional methods unless otherwise specified.

[0052] The materials, reagents, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0053] Example 1

[0054] The soil sample used in Example 1 was taken from a subway construction site in Tianjin, a coastal city in northern China. The natural moisture content of the soil sample was measured to be 24.1% at the site, and the specific gravity G s was 2.69. The coarse grain content (>75um) of the soil sample was 55.6%, the silt grain content (5-75um) was 37.6%, and the clay grain content (<5um) was 6.8%. The liquid limit, plastic limit, and plasticity index of the soil sample were measured to be 32.5%, 27.2%, and 5.3%, respectively.

[0055] The cement-based material used was ordinary Portland cement (OPC, 42.5R / N), and the specific gravity of the cement was measured to be 3.11.

[0056] Step 1: 100g of cement was mixed with deionized water according to the standard consistency water requirement for 180 seconds. The mixed slurry was then poured into a 200mL plastic bottle, sealed with a lid, and placed in a 20°C environment for curing. When the sample reached the specified age (3, 7, 14, 28, 60, 90 days), the sample was transferred to 6 freeze-drying sample pans, vacuum freeze-dried for 24 hours, crushed, and sieved through a 2mm sieve to obtain a powdery sample. 15g of the powdery sample at different curing ages was taken, and the specific gravity of the sample was measured using the specific gravity bottle method. 5g of the powdery sample was placed in a 1000°C muffle furnace for 2 hours, then removed and cooled to room temperature in a dry environment. The non-evaporable water content of the sample was measured. The results of the specific gravity and non-evaporable water content measurements are shown in Table 1:

[0057] Table 1: Measurement results of specific gravity and non-evaporable water content in Example 1

[0058] Curing age 3 days 7 days 14 days 28 days 60 days 90 days Specific gravity G t ]] 2.43 2.26 2.13 2.07 2.03 1.96 Non-evaporable water content / % 7.02 11.02 13.14 15.59 15.87 17.57

[0059] The function was used to fit the non-evaporable water content L t of the cement-based material at 6 curing ages (t=3, 7, 14, 28, 60, 90), and the function L t was obtained, which is a nonlinear function of the curing age t.

[0060]

[0061] The derivative function ΔL t of the function L t with respect to the curing age t was calculated, and the result was ΔL t ≤0.01% / d when the curing age t=105 days, and L t equals 17.48 at this time. Therefore, L ∞ equals 17.48.

[0062] Further, the hydration degree W s of the cement-based material at time t was calculated using the formula W s (t), and the results are shown in Table 2:

[0063]

[0064] Table 2 Hydration degree W of cement-based material at each curing age in Example 1 s (t) Calculation result

[0065] Curing age 3 days 7 days 14 days 28 days 60 days 90 days Degree of hydration W s (t) / %]] 40.15 63.04 75.18 89.20 90.78 100.00

[0066] Step 2, the ratio R of unhydrated cement-based material to hydrated cement-based material was calculated from the following equation an and R hp , and the results are shown in Table 3:

[0067]

[0068] In the equation, γ is the mass of the cement-based material after complete hydration per unit mass, and has a value equal to (1 + L ∞ ).

[0069] Table 3 Calculation results of R an and R hp in Example 1

[0070] Curing age 3 days 7 days 14 days 28 days 60 days 90 days [R an ]] 0.56 0.33 0.22 0.09 0.08 0.00 [R hp ]] 0.44 0.67 0.78 0.91 0.92 1.00

[0071] Further, the specific gravity G of the hydration product was calculated from the following equation sh , and the results are shown in Table 4:

[0072]

[0073] In the equation, G cd is the initial specific gravity of the cement-based material, and was measured using a specific gravity bottle method.

[0074] Table 4 Calculation results of specific gravity G of hydration product in Example 1 sh

[0075] Curing age 3 days 7 days 14 days 28 days 60 days 90 days Specific gravity G sh ]] 1.90 1.99 1.96 2.00 1.97 1.96

[0076] Further, the volume expansion rate P of the cement-based material after complete hydration was calculated from the following equation, and the results are shown in Table 5, with an average value of 186.1% taken as the volume expansion rate P of the cement-based material.

[0077]

[0078] Table 5 Calculation results of volume expansion rate P in Example 1

[0079] Curing age 3 days 7 days 14 days 28 days 60 days 90 days Volume expansion P 192 184 187 182 185 187

[0080] ​Step 3. Take 138.5 g of oven-dried soil sample (moisture content of 1.4%) and add 33 g of deionized water. Stir for 5 minutes and then place in a sealed plastic bag for 24 hours. Weigh 8.5 g of cement and add to the wet soil and stir well to ensure homogeneity. Press the mixture into a cylindrical mold with a diameter of 50 mm and a height of 50 mm. After demolding, seal with plastic film to prevent moisture loss. Repeat the process to prepare 5 samples. After 3, 7, 14, 28, 60, and 90 days of curing in a curing room (temperature of 20 ± 2°C and humidity of 95%), perform unconfined compressive strength tests on the samples. The results are shown in Table 6:

[0081] Table 6 Unconfined compressive strength of cement-solidified silt in Example 1

[0082] Curing age 3 days 7 days 14 days 28 days 60 days 90 days measured intensity q u,s / kPa 249.30 380.07 488.02 653.06 783.70 828.93

[0083] The initial porosity n0 of the cement-solidified silt is calculated using the following formula:

[0084]

[0085] In the formula, V is equal to the volume of the cylindrical test block, which is 98.175 cm3. 3 .

[0086] Further, the gel-sol ratio GSR of the cement-solidified silt is calculated using the following formula, and the results are shown in Table 7:

[0087]

[0088] Table 7 Gel-sol ratio GSR of cement-solidified silt in Example 1

[0089] Curing age 3 days 7 days 14 days 28 days 60 days 90 days Gel to air ratio GSR / % 1.96 3.08 3.69 4.38 4.46 4.94

[0090] Step 4. The unconfined compressive strength of the cement-solidified silt is preliminarily predicted using the following formula:

[0091] q u,y = y0 + A x e Bx

[0092] In the formula, y0, A, and B are fitting parameters, and the initial values are -1000, 1000, and 0.1, respectively. q u,y represents the preliminary prediction of the unconfined compressive strength of the cement-solidified silt, and x represents the gel-sol ratio GSR of the cement-solidified silt.

[0093] Table 8 Preliminary prediction of unconfined compressive strength of cement-solidified silt in Example 1

[0094] Curing age 3 days 7 days 14 days 28 days 60 days 90 days Predicted intensity q u,y / kPa 216.52 360.70 446.28 549.60 562.05 638.85

[0095] Further, the measured strength q u,swith the predicted strength q u,y The M value is calculated according to the following formula, and the minimum value of M is solved by using a programming solving method, and the three coefficients y0, A, and B are set as variable quantities, and the three parameters are solved and corrected, and the corrected y0, A, and B are -49.64, 135.67, and 0.384:

[0096] M = ∑(q u,s -q u,y (GSR)) 2

[0097] The three fitting parameters y0, A, and B after correction are substituted into the above formula as the prediction method of the unconfined compressive strength of the cement-based material solidified silt, which provides a basis for engineering design and construction control.

[0098] Example 2

[0099] The soil sample used in Example 2 was taken from a subway construction site in Tianjin, a coastal city in northern China. The natural moisture content of the soil sample taken was 24.1%, and the specific gravity G s was 2.69. The content of coarse particles (>75um) in the soil sample taken was 55.6%, the content of silt particles (5-75um) was 37.6%, and the content of clay particles (<5um) was 6.8%. The liquid limit, plastic limit, and plasticity index of the soil sample taken were determined to be 32.5%, 27.2%, and 5.3%, respectively.

[0100] The cement used was ordinary Portland cement (OPC, 42.5R / N). The phosphogypsum came from a chemical plant in Luhe, Nanjing, Jiangsu. The specific gravities of the cement and phosphogypsum were measured to be 3.11 and 3.01, respectively.

[0101] 83.33g of cement and 16.67g of phosphogypsum were thoroughly mixed, deionized water was added according to the water requirement for standard consistency, and stirred for 180 seconds. The stirred slurry was poured into a 200mL plastic bottle, sealed with a lid, and placed in a 20℃ environment for curing. When the sample reached the specified age (3, 7, 14, 28, 60, 90 days), the sample was transferred to 6 freeze-dried sample pans, vacuum freeze-dried for 24h, crushed, and sieved through a 2mm sieve to obtain a powdery sample. 15g of the powdery sample at different curing ages was taken, and the specific gravity was measured by the specific gravity bottle method. 5g of the powdery sample was placed in a 1000℃ muffle furnace for 2 hours, then taken out and placed in a dry environment to cool to room temperature, and the non-evaporative water content of the sample was measured. The results of the specific gravity and non-evaporative water content measurements are shown in Table 9:

[0102] Table 9 Measurement results of specific gravity and non-evaporative water content in Example 2

[0103] Curing age 3 days 7 days 14 days 28 days 60 days 90 days Specific gravity G t ]] 2.32 2.14 2.03 1.96 1.92 1.87 Non-evaporable water content / % 8.10 13.08 14.94 18.10 21.01 24.62

[0104] The function The non-evaporable water content L of the cement-based material at 6 curing ages t (t = 3, 7, 14, 28, 60, 90) is fitted to obtain L t a non-linear function of the curing age t;

[0105]

[0106] The derivative function ΔL t with respect to the curing age t is calculated to obtain the curing age t = 390 days when ΔL t ≤ 0.01% / d, at which time L t equals 30.86, and L ∞ equals 30.86.

[0107] Further, the hydration degree W s (t) of the cement-based material at time t is calculated using the following formula, and the results are shown in Table 10:

[0108]

[0109] Table 10 Calculation results of the hydration degree W s (t) of the cement-based material at each curing age in Example 2

[0110] Curing age 3 days 7 days 14 days 28 days 60 days 90 days Degree of hydration W s (t) / %]] 26.26 42.37 48.41 58.65 68.09 79.79

[0111] Further, the ratio R an of the unhydrated cement-based material and the hydrated cement-based material is calculated using the following formula, and the results are shown in Table 11: hp

[0112]

[0113] In the formula, γ is the mass of the cement-based material after complete hydration per unit mass, and its value is equal to (1 + L ∞ ).

[0114] Table 11 Calculation results of R an and R hp in Example 2

[0115] Curing age 3 days 7 days 14 days 28 days 60 days 90 days [R an ]]> 0.68 0.51 0.45 0.35 0.26 0.16 [R hp ]]> 0.32 0.49 0.55 0.65 0.74 0.84

[0116] Further, the specific gravity G sh of the hydration product is calculated using the following formula, and the results are shown in Table 12:

[0117]

[0118] In the formula, G cd is the initial specific gravity of the cement-based material, which is measured using a specific gravity bottle method.​

[0119] Table 12 Specific gravity G of the hydration product in Example 2 sh Calculation results

[0120] Curing age 3 days 7 days 14 days 28 days 60 days 90 days Specific gravity G sh ]] 1.57 1.65 1.61 1.65 1.70 1.75

[0121] Further, the volume expansion ratio P of the cement-based material when fully hydrated was calculated according to the following equation, and the results are shown in Table 13, with the average value of 236.9% being the volume expansion ratio P of the cement-based material.

[0122]

[0123] Table 13 Calculation results of the volume expansion ratio P in Example 2

[0124] Curing age 3 days 7 days 14 days 28 days 60 days 90 days Volume expansion P 249 237 243 237 231 224

[0125] A dried soil sample of 968 g (oven-dried moisture content of 1.4%) was taken, 226 g of deionized water was added, and after stirring for 5 min, it was placed in a sealed plastic bag and left to stand for 24 h. 58 g of cement and 11.6 g of phosphogypsum were weighed and added to the wet soil and stirred thoroughly to ensure homogeneity. 170 g, 175 g, 180 g, 185 g, 190 g, and 195 g of the mixture were respectively pressed into cylindrical molds with a diameter of 50 mm and a height of 50 mm. After demolding, a plastic film was used to seal to prevent water loss. The samples were placed in a curing room (temperature 20 ± 2°C, humidity 95%) for 28 days, and then unconfined compressive strength tests were performed, with the results shown in Table 14:

[0126] Table 14 Unconfined compressive strength of the solidified silt in Example 2

[0127] Specimen weight 170g 175g 180g 185g 190g 195g measured intensity q u,s / kPa 698.84 863.94 967.64 1008.37 1101.88 1251.56

[0128] The initial porosity n0 of the above solidified silt was calculated using the following equation, with the results shown in Table 15:

[0129]

[0130] In the equation, V is equal to the volume of the cylindrical test block, which is 98.175 cm 3 .

[0131] Table 15 Initial porosity of the solidified silt in Example 2

[0132] Specimen weight 170g 175g 180g 185g 190g 195g Initial porosity n0 / % 47.53 45.89 44.36 42.97 41.38 40.02

[0133] Further, the gel-space ratio GSR of the above solidified silt was calculated using the following equation, with the results shown in Table 16:

[0134]

[0135] Table 16 Cured silt glue-air ratio GSR in Example 8

[0136] Specimen weight 170g 175g 180g 185g 190g 195g Gel to air ratio GSR / % 5.21 5.56 5.92 6.26 6.68 7.07

[0137] Furthermore, the following formula is used to make a preliminary prediction of the unconfined compressive strength of silt solidified with cement-based materials:

[0138] q u,y =y0+A×e Bx

[0139] Where y0, A, and B are fitting parameters, and their initial values ​​are -1000, 1000, and 0.1 respectively; q u,y represents the preliminary prediction result of the unconfined compressive strength of the solidified silt, and x represents the gel-spatial ratio GSR of the solidified silt.

[0140] Table 17 Preliminary prediction results of unconfined compressive strength of solidified silt in Example 1

[0141] Curing age 3 days 7 days 14 days 28 days 60 days 90 days Predicted intensity q u,y / kPa 683.71 743.68 807.60 870.12 950.33 1027.90

[0142] Furthermore, compared with the measured intensity q u,s and the predicted intensity q u,y Calculate the M value according to the following formula, and use the planning solution method to solve the minimum value of M. Set the three coefficients y0, A, and B as variables, solve and correct the three parameters, and obtain the corrected y0, A, and B as -1750, 1380, and 0.11:

[0143] M=∑(q u,s -q u,y (GSR) 2

[0144] The modified fitting parameters y0, A, and B are substituted into the above formula as a prediction method for the unconfined compressive strength of cement-based material-solidified silt in this project, providing a basis for engineering design and construction control.

Claims

1. A method for predicting the strength of cement-solidified silt based on the ratio of cement to air, characterized in that: The following steps are involved: Step 1: Determine the specific gravity of silt and cement-based curing agent and calculate their initial porosity; Step 2: Conduct indoor experiments to determine the hydration degree of the cement-based curing agent at different curing ages and calculate the volume expansion rate of the cement-based curing agent; The degree of hydration W s The determination method of (t) comprises the following steps: (1) After mixing the cement-based material with water according to the standard consistency, the mixture was placed under standard curing conditions for 3, 7, 14, 28, 60 and 90 days; (2) The cement-based material that has reached the curing age is taken out, freeze-dried, crushed, and passed through a 2 mm sieve to obtain a sieved sample; (3) Take 5g of sieved samples of different curing ages, place them in a muffle furnace at 1000℃ for 2 hours, cool them in a dry environment, and weigh the sample mass, which is recorded as m t , t is the curing age, then the weight of non-evaporated water of cement-based materials at time t is (5-m t ), the non-evaporable water content of cement-based materials at time t is defined as L t , calculated using the following formula: (4) The non-evaporable water content L of cement-based materials at 6 curing ages is calculated using the function shown in the following formula: t Perform fitting and obtain L t Regarding the nonlinear function of curing age t, (5) Using the above steps, we can obtain L t Regarding the nonlinear function of curing age t, the non-evaporable water content of cement-based materials when fully hydrated is predicted. When the non-evaporable water content change rate ΔL t When the water content is less than 0.01% / d, the cement-based material is considered to be fully hydrated. The non-evaporable water content at this time is the non-evaporable water content after complete hydration, which is recorded as L ∞ ; (6) The hydration degree W of cement-based materials at time t is calculated using the following formula: s (t): The method for measuring the volume expansion rate P comprises the following steps: (1) Take the above sieved samples and use the pycnometer method to determine the specific gravity of the sieved samples at different curing ages, which is recorded as G t , t is the curing age; (2) The sieved sample consists of two parts: unhydrated cement-based material and hydrated cement-based material. The ratios of unhydrated cement-based material and hydrated cement-based material are calculated by the following formula: R an and R hp : Where γ is the mass of cement-based material after complete hydration, and its value is equal to (1+L ∞ ); (3) Calculate the specific gravity G of the hydration product according to the following formula sh : Where G cd is the initial specific gravity of the cement-based material, determined by the pycnometer method; (4) Calculate the volume expansion rate P of the cement-based material when it is fully hydrated according to the following formula: Step 3, calculating the cement-solid void ratio at different curing ages by using the initial porosity, hydration degree and volume expansion rate; The initial porosity n0 is calculated using the following formula: Where V represents the total volume of solidified silt; m cd 、m s Respectively represent the mass of cement-based materials and silt in the solidified silt; G s Indicates the specific gravity of silt particles, measured using the pycnometer method; γ w ≈10kN / m 3 , g≈10×10 3 kg·m / s 2 ; The calculation formula of the gas-to-air ratio GSR is as follows: Where m cd 、W s (t), P and G cd are the addition amount, hydration degree, volume expansion rate and specific gravity of cement-based materials; g is the acceleration of gravity; n0 and V are the initial porosity and volume of the solidified silt, respectively; γ w is the weight of water; Step 4: Substitute the cement-air ratio into the strength prediction model to predict the unconfined compressive strength of cement-cured silt at different curing ages; The prediction model is shown below: q u =y0+A×e Bx In the formula, y0, A, B are fitting parameters, q u represents the unconfined compressive strength of the solidified silt, and x represents the gel-spatial ratio (GSR) of the solidified silt; The initial values ​​of the fitting parameters y0, A, and B are -1000, 1000, and 0.1, respectively. The correction steps are as follows: (1) Six groups of samples with different mix ratios or curing ages were prepared from silt and cement-based materials at the construction site. After standard curing to the target age, unconfined compressive strength tests were conducted. The measured strength obtained in the test was recorded as q u,s ; (2) According to the calculation, the glue-air ratio GSR and predicted strength q of the six groups of samples with different ratios in the above steps are obtained. u,y ; (3) Comparison with measured intensity q u,s and the predicted intensity q u,y Calculate the M value according to the following formula, and use the planning solution method to solve the minimum value of M. Set the three coefficients y0, A, and B as variables, and solve and correct the three parameters: M=∑(q u,s -q u,y (GSR)) 2 。

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