Slurry creep multi-scale calculation method

Abstract

The invention provides a slurry creep multi-scale calculation method. The method comprises the following steps: S1, acquiring volume fractions of calcium hydroxide, pores and unhydrated particles in a sample to be detected; s2, the ratio of the LD C-S-H to the HD C-S-H is calculated through a Tennis-Jennings method, the mass fraction of the LD C-S-H and the mass fraction of the HD C-S-H are calculated, and then the mass fraction of the LD C-S-H and the mass fraction of the HD C-S-H are converted into the volume fraction of the LD C-S-H and the volume fraction of the HD C-S-H according to the mass fraction of the LD C-S-H and the mass fraction of the HD C-S-H; s3, the contact creep modulus of the LD C-S-H, the contact creep modulus of the HD C-S-H, the contact creep modulus of the calcium hydroxide and the unhydrated particles are obtained through a nanoindentation test, and then the contact creep modulus of C-S-H is calculated through the contact creep modulus of the LD C-S-H, the contact creep modulus of the HD C-S-H, the contact creep modulus of the calcium hydroxide and the unhydrated particles; and S4, calculating the creep modulus of the slurry through the contact creep modulus of the C-S-H. According to the method, the cost for testing the creep performance of the slurry is effectively reduced by establishing the database, overlong-time maintenance and a large number of nanoindentation experiments required by creep of the slurry are avoided, calculation is easy and convenient, and precision is high.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering, and in particular to a method for multi-scale calculation of slurry creep. Background Art

[0002] Creep is the delayed deformation of concrete under continuous stress. Creep performance will affect the crack resistance and volume stability of concrete. The main creep of concrete occurs in the paste. Reducing the creep of the paste is conducive to increasing the durability of the concrete structure. At the same time, under the current policy background of the dual carbon target, different mineral admixtures are usually added to concrete to reduce the environmental burden, which requires the molding of different test blocks for creep testing. At the same time, the curing time of long-term creep of concrete is usually 180 days or more, which is cumbersome and time-consuming, resulting in a large loss of manpower and material resources.

[0003] So far, there are many studies on the multi-scale creep of pastes, and the widely used and high-precision methods include nanoindentation test method, numerical and analytical homogenization method and Mori-Tanaka method. Among them, the nanoindentation test method needs to make a large number of indentation points in different areas of the specimen in order to obtain high-precision results. In addition, the nanoindentation test needs to distinguish different phases, which is costly; the numerical and analytical homogenization method is generally used to simulate the early-age creep of pastes, and for long-term creep, a lot of calculation costs are required, and the equipment requirements are high; the Mori-Tanaka method is used to study simple paste microstructures, without considering the evolution of microstructures caused by cement hydration. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the shortcomings of the prior art, the present invention provides a method for multi-scale calculation of slurry creep. By establishing a database, the cost of slurry creep performance testing can be effectively reduced, and the excessively long curing time and large number of nanoindentation experiments required for slurry creep can be avoided. The calculation is simple and the accuracy is high, which solves the problems raised in the above-mentioned background technology.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A method for multi-scale calculation of slurry creep comprises the following steps:

[0009] S1. Obtaining the volume fractions of calcium hydroxide, pores and unhydrated particles in the sample to be tested;

[0010] S2. The ratio between LD CSH and HD CSH is calculated by the Tennis-Jennings method, the mass fractions of LDC-SH and HD CSH are calculated, and then the mass fractions of LD CSH and HD CSH are converted into the volume fractions of LD CSH and HD CSH;

[0011] S3, the contact creep modulus of LD CSH, HD CSH, calcium hydroxide and unhydrated particles are obtained by nanoindentation test, and then the contact creep modulus of CSH is calculated by the contact creep modulus of LD CSH, HD CSH, calcium hydroxide and unhydrated particles;

[0012] S4. Calculate the creep modulus of the paste through the contact creep modulus of CSH.

[0013] Preferably, in step S1, the volume fraction of the pores is obtained by positron testing, and the volume fractions of the calcium hydroxide and unhydrated particles are obtained by terahertz spectroscopy analysis.

[0014] Preferably, in step S2, the mass fraction of LD CSH is obtained by the following calculation equation:

[0015]

[0016] Where M L is the mass fraction of LD CSH in the total CSH;

[0017] is the water-to-binder ratio;

[0018] ρ cement =3.2, that is, the specific gravity of cement is 3.2;

[0019] P cs =0.07mL / g, that is, the chemical shrinkage rate of each gram of cement is 0.07mL / g;

[0020] k is a first-order constant related to cement composition, particle size distribution and curing temperature;

[0021] t is the curing time.

[0022] Preferably, in step S3, the contact creep modulus of the CSH is obtained by the following calculation equation:

[0023]

[0024] In the formula, C C-S-H is the contact creep modulus of CSH;

[0025] fm is the volume fraction of LD CSH;

[0026] C m is the contact creep modulus of LD CSH;

[0027] f i is the volume fraction of HD CSH;

[0028] C i is the contact creep modulus of HD CSH.

[0029] Preferably, in step S4, the creep modulus of the slurry is obtained by the following calculation equation:

[0030]

[0031] In the formula, f C-S-H is the volume fraction of CSH;

[0032] C C-S-H is the contact creep modulus of CSH;

[0033] C paste is the contact creep modulus of the paste;

[0034] f Clinker is the volume fraction of clinker;

[0035] C Clinker is the contact creep modulus of clinker;

[0036] f CH is the volume fraction of calcium hydroxide;

[0037] C CH is the contact creep modulus of calcium hydroxide.

[0038] In the present invention, "LD CSH" stands for "low density calcium silicate hydrate gel";

[0039] "HD CSH" stands for "High Density Calcium Silicate Hydrate Gel".

[0040] (III) Beneficial effects

[0041] The present invention provides a method for multi-scale calculation of slurry creep, which has the following beneficial effects:

[0042] 1. The method for multi-scale calculation of slurry creep provided in this scheme obtains the contact creep modulus of the physical phase through a small number of nanoindentation experiments, and at the same time establishes a database to calculate the creep of the slurry by searching the database. The experimental time is short and the application range is wide. Compared with the existing slurry multi-scale calculation technology, the number of nanoindentation experiments is significantly reduced, and it has higher technical accuracy, precision and reliability.

[0043] 2. The method for multi-scale calculation of slurry creep provided in this scheme has an average relative error of less than 5% between the calculated multi-scale creep modulus and the actual multi-scale creep modulus obtained in the experiment, and the relative error of all results is less than 10%, with high accuracy and reliability.

[0044] 3. The multi-scale calculation method of paste creep provided in this scheme combines positron test and terahertz spectroscopy test to obtain the creep modulus of paste. Compared with the existing concrete creep modulus obtained through a large amount of nanoindentation data, the experimental cost and experimental cycle are significantly reduced. DETAILED DESCRIPTION

[0045] In order to better illustrate the content of the present invention, a detailed description is given below in conjunction with specific embodiments.

[0046] Example 1

[0047] Step 1, the volume fraction of the pores of the sample to be tested is obtained by positron testing, and the volume fraction of calcium hydroxide and unhydrated particles of the sample to be tested is obtained by terahertz spectroscopy analysis. The sample to be tested includes pure cement concrete with a water-binder ratio of 0.3, recorded as Control-0.3; pure cement concrete with a water-binder ratio of 0.4, recorded as Control-0.4; pure cement concrete with a water-binder ratio of 0.5, recorded as Control-0.5; concrete with a water-binder ratio of 0.4 and a sludge powder doping amount of 10%, recorded as WTS10-0.4; concrete with a water-binder ratio of 0.4 and a sludge powder doping amount of 15%, recorded as WTS15-0.4; concrete with a water-binder ratio of 0.4 and a sludge powder doping amount of 20%, recorded as WTS15-0.4; concrete with a water-binder ratio of 0.4 and a sludge powder doping amount of 20%, recorded as WTS15-0.4. % concrete, recorded as WTS20-0.4; concrete with a water-binder ratio of 0.4 and a fly ash doping amount of 10%, recorded as FA10-0.4; concrete with a water-binder ratio of 0.4 and a fly ash doping amount of 15%, recorded as FA15-0.4; concrete with a water-binder ratio of 0.4 and a fly ash doping amount of 20%, recorded as FA20-0.4; concrete with a water-binder ratio of 0.4 and a granulated blast furnace slag doping amount of 10%, recorded as GGBS10-0.4; concrete with a water-binder ratio of 0.4 and a granulated blast furnace slag doping amount of 15%, recorded as GGBS15-0.4; concrete with a water-binder ratio of 0.4 and a granulated blast furnace slag doping amount of 20%, recorded as GGBS20-0.4;

[0048] The volume fractions (%) of the pores, calcium hydroxide and unhydrated particles of the above-mentioned samples to be tested are shown in Table 1:

[0049] Table 1

[0050] serial number Calcium hydroxide Porosity Unhydrated particles Control-0.3 11.3 5.2 16.3 Control-0.4 13.5 6.2 14.2 Control-0.5 14.8 6.6 12.3 WTS10-0.4 13.4 5.3 12.8 WTS15-0.4 13.1 5 13.1 WTS20-0.4 12.8 4.6 13.3 FA10-0.4 10.4 4.8 14.8 FA15-0.4 10.1 4.3 15.1 FA20-0.4 9.5 3.9 15.5 GGBS10-0.4 10.5 5.1 14.5 GGBS15-0.4 10.1 4.6 14.8 GGBS20-0.4 9.6 4.2 15.3

[0051] Step 2: Calculate the ratio of LD CSH to HD CSH using the Tennis-Jennings method, and calculate the mass fraction of LD CSH in the total CSH according to equation 1, denoted as M L , according to the ratio between LD CSH and HD CSH and M L , the mass fraction (%) of HD CSH in the total amount of CSH can be calculated, as shown in Table 2, and then the volume fractions of LD CSH and HD CSH can be converted according to the mass fractions of LD CSH and HD CSH, where the density of LD CSH is 1.44 g / cm 3 The density of HD CSH is 1.75 g / cm 3 .

[0052] The calculation equation shown in Formula 1 is:

[0053]

[0054] Among them, M L is the mass fraction of LD CSH in the total CSH; is the water-binder ratio; cement =3.2; P cs =0.07mL / g; k is a first-order constant; t is the curing time.

[0055] Table 2

[0056] serial number LDC-SH HDC-SH Control-0.3 44.5 55.5 Control-0.4 44.0 56.0 Control-0.5 43.6 56.4 WTS10-0.4 44.0 56.0 WTS15-0.4 43.2 56.8 WTS20-0.4 42.2 57.8 FA10-0.4 44.0 56.0 FA15-0.4 42.7 57.8 FA20-0.4 41.5 58.5 GGBS10-0.4 43.9 56.1 GGBS15-0.4 43.2 56.8 GGBS20-0.4 42.5 57.5

[0057] Table 3 shows the volume fraction (%) of LD CSH and HD CSH:

[0058] Table 3

[0059]

[0060]

[0061] Step 3: The contact creep modulus (MPa) of LD CSH, HD CSH, calcium hydroxide and unhydrated particles is calculated by nanoindentation, as shown in Table 4. According to the calculation equation shown in Formula 2, the contact creep modulus (MPa) of CSH is calculated, as shown in Table 5.

[0062] The calculation equation of formula 2 is:

[0063]

[0064] Among them, C C-S-H is the contact creep modulus of CSH; f m is the volume fraction of LD CSH; C m is the contact creep modulus of LD CSH; f i is the volume fraction of HD CSH; C i is the contact creep modulus of HD CSH.

[0065] Table 4

[0066] serial number LDC-SH HDC-SH Calcium hydroxide Unhydrated particles Control-0.3 84.76±19.56 147.73±30.48 314.24±33.17 1465.32±459.07 Control-0.4 82.38±17.34 152.28±21.65 310.47±40.99 1452.58±463.09 Control-0.5 80.19±15.24 159.62±27.62 308.62±37.46 1448.57±455.23 WTS10-0.4 91.54±21.75 165.43±25.36 302.28±42.23 1405.56±334.39 WTS15-0.4 87.43±20.31 159.22±24.62 292.31±38.69 1433.72±447.21 WTS20-0.4 83.26±18.49 154.91±22.41 283.72±35.32 1496.37±481.07 FA10-0.4 94.68±23.76 163.53±31.71 308.54±31.88 1449.82±498.44 FA15-0.4 87.76±19.51 178.24±35.36 306.63±35.46 1456.22±477.12 FA20-0.4 85.46±18.13 183.43±36.97 305.97±36.22 1458.03±463.48 GGBS10-0.4 93.91±23.58 165.58±31.68 308.67±32.66 1447.38±461.07 GGBS15-0.4 92.37±22.68 170.42±34.16 307.28±33.52 1452.77±470.37 GGBS20-0.4 90.07±21.24 176.49±35.07 306.69±39.27 1455.67±474.25

[0067] Table 5

[0068] serial number Contact creep modulus of CSH (GPa) Control-0.3 112.50 Control-0.4 108.24 Control-0.5 105.70 WTS10-0.4 120.47 WTS15-0.4 116.33 WTS20-0.4 112.97 FA10-0.4 122.81 FA15-0.4 124.46 FA20-0.4 126.18 GGBS10-0.4 123.05 GGBS15-0.4 124.62 GGBS20-0.4 126.03

[0069] Step 4: According to the calculation equation shown in Formula 3, the creep modulus (MPa) of the slurry is calculated by the contact creep modulus of CSH, as shown in Table 6;

[0070] The calculation equation shown in Formula 2 is:

[0071]

[0072] Among them, f C-S-H is the volume fraction of CSH; C C-S-H is the contact creep modulus of CSH; C paste is the contact creep modulus of the paste; f Clinker is the volume fraction of clinker; C Clinker is the contact creep modulus of clinker; f CH is the volume fraction of calcium hydroxide; C CH is the contact creep modulus of calcium hydroxide.

[0073] Table 6

[0074]

[0075]

[0076] According to the data in Table 6, it can be seen that the method for multi-scale calculation of slurry creep provided by the present invention has high accuracy and reliability. The multi-scale creep modulus results of slurry can be obtained through simple experiments, and a database is established, which reduces the cost of creep testing.

[0077] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for multi-scale calculation of slurry creep, characterized by: The following steps are involved: S1. Obtaining the volume fractions of calcium hydroxide, pores and unhydrated particles in the sample to be tested; S2. The ratio between LDC-SH and HDC-SH is calculated by the Tennis-Jennings method, the mass fractions of LDC-SH and HDC-SH are calculated, and then the mass fractions of LDC-SH and HDC-SH are converted into the volume fractions of LDC-SH and HDC-SH; S3, the contact creep modulus of LDC-SH, HDC-SH, calcium hydroxide and unhydrated particles are obtained by nanoindentation test, and the contact creep modulus of CSH is calculated by the contact creep modulus of LDC-SH, HDC-SH, calcium hydroxide and unhydrated particles; S4. Calculate the creep modulus of the paste through the contact creep modulus of CSH.

2. The method for multi-scale calculation of slurry creep according to claim 1, characterized in that: In step S1, the volume fraction of the pores is obtained by positron testing, and the volume fractions of the calcium hydroxide and unhydrated particles are obtained by terahertz spectroscopy analysis.

3. The method for multi-scale calculation of slurry creep according to claim 1, characterized in that: In step S2, the mass fraction of LDC-SH is calculated by the following calculation equation: Where M L is the mass fraction of LDC-SH in the total amount of CSH; is the water-to-binder ratio; r cement =3.2; P cs =0.07mL / g; k is a first-order constant; t is the curing time.

4. The method for multi-scale calculation of slurry creep according to claim 1, characterized in that: In step S3, the contact creep modulus of the CSH is obtained by the following calculation equation: In the formula, C C-S-H is the contact creep modulus of CSH; f m is the volume fraction of LD CSH; C m is the contact creep modulus of LD CSH; f i is the volume fraction of HD CSH; C i is the contact creep modulus of HD CSH.

5. The method for multi-scale calculation of slurry creep according to claim 1, characterized in that: In step S4, the creep modulus of the slurry is obtained by the following calculation equation: In the formula, f C-S-H is the volume fraction of CSH; C C-S-H is the contact creep modulus of CSH; C paste is the contact creep modulus of the paste; f Clinker is the volume fraction of clinker; C Clinker is the contact creep modulus of clinker; f CH is the volume fraction of calcium hydroxide; C CH is the contact creep modulus of calcium hydroxide.

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