CN103105485A - Hardened ordinary cement paste thermal expansion coefficient multiscale predication method - Google Patents

Abstract

The invention discloses a hardened ordinary cement paste thermal expansion coefficient multiscale predication method. The method comprises the following steps of: step A: dividing hardened ordinary cement paste into different scales according to microstructure composition, wherein the different scales comprise different typical phases; step B. acquiring the volume percentage composition of each phase in different scales of the hardened ordinary cement paste; and step C. sequentially calculating the thermal expansion coefficient of each scale of the hardened ordinary cement paste from the minimum scale by adopting an upward gradual homogenization method, wherein the thermal expansion coefficient of the maximal scale is the thermal expansion coefficient of the hardened ordinary cement paste. According to the invention, a hardened ordinary cement paste thermal expansion coefficient multiscale predication model is established according to cement and hydration product essential attributes as well as cement paste microstructure composition and development principle, so that the relationship between the cement paste microstructure and macro-properties is established, and the problems of multiple influence factors on the macro-properties of cement-based materials and high discretization of test data are solved essentially.

Description

The sclerosis Portland cement is starched thermal expansivity multi-scale prediction method only

Technical field

The present invention relates to a kind of sclerosis Portland cement and only starch thermal expansivity multi-scale prediction method, belong to the cement-based material technical field.

Background technology

The thermal expansivity of hardening cement base material is one of its basic parameter, it is also one of parameter of structural design emphasis care, its value size direct relation is the structural internal force size all, and then arrangement of reinforcement quantity, sectional dimension are selected to produce significant impact, becomes sometimes design and controls parameter.The thermal expansivity value of research cement paste is the basis of research cement-based material thermal expansivity.But the method for traditional mensuration cement paste thermal expansivity, take time and effort and produce discarded object, due to reasons such as starting material, match ratio, environmental baseline, testing apparatus and method of testing and testing crew operative techniquies, the thermal expansivity discreteness that provides is larger simultaneously, even mutually contradiction.

The overall performance of compound substance depends on performance, geometric shape and the topological structure of composition material.Cement paste is the non-homogeneous composite material of very complex, and its component is various, the solid, liquid, gas three-phase coexistence, and disorder distribution, the range scale of these species distribution is wide, and from the nanometer to the micron, millimeter has a distribution, and it forms structure and at hydration process, larger variation occurs.Multi-scale method can be considered the composition material feature on different scale, realization is from the material property simulation of microcosmic-thin sight the-macroscopic view, set up the relation between material constituent performance, micromechanism and macro property, and fundamentally explain the change mechanism of material macro property, this is for promoting that investigation of materials is significant.Research for the cement paste thermal expansivity at present focuses mostly in experimental study, rests on the level of macroscopical presentation, and the conclusion that draws is only meaningful in limited scope, has greatly limited its engineering range of application.

Summary of the invention

Technical matters to be solved by this invention is to overcome the prior art deficiency, provide a kind of sclerosis Portland cement only to starch thermal expansivity multi-scale prediction method, can be according to the essential attribute of composition material component and hydrated product, based on cement paste micromechanism formation and evolution process, adopt multiple dimensioned and homogenization method to determine that hardened cement starches thermal expansivity only, thereby provide accurate parameter for the early stage mechanics of cement-based material, deformation performance research and Numerical Simulation Analysis.

Sclerosis Portland cement of the present invention is starched thermal expansivity multi-scale prediction method only, comprises the following steps:

Steps A, the clean slurry of the Portland cement that will harden are divided into different scale according to microstructure, and different scale comprises different typical phases;

Step B, obtain the sclerosis Portland cement only starch the volumn concentration of each phase in different scale;

Step C, from smallest dimension, adopt upwards progressively homogenization method, calculate successively according to following formula the thermal expansivity that the sclerosis Portland cement is starched each yardstick only:

${\mathrm{\α}}_X^{\mathrm{hom}}={\mathrm{\κ}}_X^{\mathrm{hom}}/K_X^{\mathrm{hom}},$

In formula,

Be the thermal expansivity of current yardstick,

With

Be respectively Thermal Stress Coefficient and the bulk modulus of this yardstick, calculate according to the following equation:

${\mathrm{\κ}}_X^{\mathrm{hom}}=\underset{r}{\mathrm{\Σ}}{f}_r{\mathrm{\κ}}_r[1+{\mathrm{\α}}_0(\frac{k_r}{k_0}-1){]}^{-1}\×\{\underset{r}{\mathrm{\Σ}}{f}_r[1+{\mathrm{\α}}_0(\frac{k_r}{k_0}-1){]}^{-1}\},$

$K_X^{\mathrm{hom}}=\underset{r}{\mathrm{\Σ}}{f}_r{k}_r[1+{\mathrm{\α}}_0(\frac{k_r}{k_0}-1){]}^{-1}\×\{\underset{r}{\mathrm{\Σ}}{f}_r[1+{\mathrm{\α}}_0(\frac{k_r}{k_0}-1){]}^{-1}\},$

In formula, k _r, κ _r, f _rBe respectively bulk modulus, Thermal Stress Coefficient, the volumn concentration of this yardstick r phase, r=1,2 ..., N, N is comprised the phase sum by this yardstick; k ₀Be the bulk modulus as this yardstick blank medium phase; α ₀Calculate according to the following equation:

${\mathrm{\α}}_0=\frac{1}{1+\frac{{4g}_0}{{3k}_0}},$

In formula, g ₀Be the modulus of shearing as this yardstick blank medium phase;

The thermal expansivity of out to out is the thermal expansivity of the clean slurry of sclerosis Portland cement.

Can adopt different partition of the scale methods according to actual conditions in steps A, the present invention preferably adopts following partition of the scale method:

Be divided into altogether 4 yardsticks, be followed successively by from small to large: yardstick I, yardstick II, yardstick III, yardstick IV; The yardstick I comprises low-density hydrated calcium silicate and high density hydrated calcium silicate; The yardstick II comprises the hydrated calcium silicate after yardstick I homogenising, and the hydrated product such as calcium hydroxide, entringite, aluminate; The yardstick III comprises the hydrated product after yardstick II homogenising, and hydrated cement particle not; Yardstick IV comprises the cement slurry solid phase after yardstick III homogenising, and pore water and pore space.

As a preferred version of the present invention, when adopting upwards progressively homogenization method to calculate hardened cement only to starch the thermal expansivity of each yardstick, use the Self-Consistent method, each yardstick blank medium is itself.

As another preferred version of the present invention, when adopting upwards progressively homogenization method to calculate hardened cement only to starch the thermal expansivity of each yardstick, use the Mori-Tanaka method, the self-reference medium of yardstick I, II, III, IV is respectively low-density hydrated calcium silicate, hydrated calcium silicate, hydrated product, cement slurry solid phase.

Compared to existing technology, the present invention has following beneficial effect:

The present invention is based on the cement-based material thermal expansivity with the essential characteristic of development of age, it is the essential attribute of composition material component and hydrated product, and micromechanism is with the development and change in the length of time, build hardened cement and only starched the multi-scale prediction model of thermal expansivity, thereby cement paste micromechanism and macro property are set up contact, and cement-based material macro property influence factor is many from having solved in essence, the discrete large problem of test figure.By the inventive method, can more conveniently obtain the thermal expansivity of the clean slurry of any moment in length of time hardened cement, and not need not carry out Real-Time Monitoring by a cover proving installation.

Description of drawings

Fig. 1 is the multiple dimensioned division schematic diagram of the clean slurry of hardened cement in embodiment;

The Different Water-Cement Ratio sclerosis Portland cement that Fig. 2 obtains for employing the inventive method is starched the comparison of thermal expansivity and trial value only.

Embodiment

Below in conjunction with accompanying drawing, technical scheme of the present invention is elaborated:

The present invention is based on Microstructure of Cement-based Material forms and with development, the sclerosis Portland cement to be starched the thermal expansivity Changing Pattern only and study, set up the sclerosis Portland cement by cement paste micromechanism and composition material and phase essential attribute and only starch thermal expansivity multi-scale prediction model, and according to this forecast model, the sclerosis Portland cement is starched thermal expansivity only and carry out Accurate Prediction.

Cement-based material life period, the intrinsic multiple dimensioned characteristic in space, for example high and low density hydrated calcium silicate is at nanoscale, and the hydrated products such as calcium hydroxide, hydrated cement particle, large pore be not at micro-meter scale, cement paste is at mm-scale.Multi-scale method considers that the space across features such as the mechanics of materials of yardstick, distortion, is important method and the technology of finding the solution the complicated mechanics problems of various materials.Wherein, homogenization theory has advantages of that as a kind of effective multiscale simulation method theory is rigorous, be easy to Numerical Implementation material macro equivalent performance, is the important method of composite Materials Design, performance prediction and structure optimization.At high density hydrated calcium silicate, low-density hydrated calcium silicate, calcium hydroxide, not on the yardstick such as hydrated cement particle, the thermal expansivity that forms phase on different scale is each phase build-in attribute, with conditional independences such as water cement ratio, the length of times, adopt multiple dimensioned and homogenization method, in conjunction with the micromechanism of the clean slurry of hardened cement, can be from predicting in essence its thermal expansivity.

Sclerosis Portland cement of the present invention is starched thermal expansivity multi-scale prediction method only, specifically comprises the following steps:

Step 1, the clean slurry of the Portland cement that will harden are divided into different scale according to microstructure, and different scale comprises different typical phases.

The multiple dimensioned division of cement paste can be carried out flexibly according to actual conditions, the present invention preferably adopts following division methods (as shown in Figure 1): cement paste is divided into 4 yardsticks according to micromechanism, is followed successively by from small to large: yardstick I, yardstick II, yardstick III, yardstick IV; The yardstick I comprises low-density hydrated calcium silicate (LD C-S-H) and high density hydrated calcium silicate (HD C-S-H); The yardstick II comprises the hydrated calcium silicate (C-S-H) after yardstick I homogenising, and the hydrated product such as calcium hydroxide (CH), entringite, aluminate; The yardstick III comprises the hydrated product after yardstick II homogenising, and hydrated cement particle not; Yardstick IV comprises the cement slurry solid phase after yardstick III homogenising, and pore water and pore space.The multiple dimensioned division methods clear physical concept of this kind cement paste, and each phase thermal expansivity can adopt existing test figure or inverting value, and be easy to arithmetic programming and realize.

Step 2, obtain the sclerosis Portland cement only starch the volumn concentration of each phase in different scale.

in each yardstick, the volumn concentration of each phase can (for example be obtained by test, the environmental scanning electronic microscope test), perhaps by Powers model (Powers T.C., Brownyard T.L.Studies of the Physical Properties of Hardened Portland Cement Paste.Part5.Studies of the Hardened Paste by Means of Specific-Volume Measurements[J] .Journal of American Concrete Institute, 1947, 18 (6): 669-711.) or Jennings-Tennis model (Jennings H.M., Tennis P.D.Model for the Developing Microstructure in Portland Cement Pastes[J] .Journal of the American Ceramic Society, 1994, 7 (12): 3161-3172.) or HYMOSTRUC model (van Breugel K.Simulation of hydration and formation of structure in hardening cement-based materials, PhD thesis, Delft University of Technology, Delft, 1991.) calculate.

Step 3, from smallest dimension, adopt upwards progressively homogenization method, calculate successively according to following formula the thermal expansivity that the sclerosis Portland cement is starched each yardstick only:

${\mathrm{\α}}_X^{\mathrm{hom}}={\mathrm{\κ}}_X^{\mathrm{hom}}/K_X^{\mathrm{hom}},$

In formula,

Be the thermal expansivity of current yardstick,

With

Be respectively Thermal Stress Coefficient and the bulk modulus of this yardstick, calculate according to the following equation:

${\mathrm{\κ}}_X^{\mathrm{hom}}=\underset{r}{\mathrm{\Σ}}{f}_r{\mathrm{\κ}}_r[1+{\mathrm{\α}}_0(\frac{k_r}{k_0}-1){]}^{-1}\×\{\underset{r}{\mathrm{\Σ}}{f}_r[1+{\mathrm{\α}}_0(\frac{k_r}{k_0}-1){]}^{-1}\},$

$K_X^{\mathrm{hom}}=\underset{r}{\mathrm{\Σ}}{f}_r{k}_r[1+{\mathrm{\α}}_0(\frac{k_r}{k_0}-1){]}^{-1}\×\{\underset{r}{\mathrm{\Σ}}{f}_r[1+{\mathrm{\α}}_0(\frac{k_r}{k_0}-1){]}^{-1}\},$

In formula, k _r, κ _r, f _rBe respectively bulk modulus, Thermal Stress Coefficient, the volumn concentration of this yardstick r phase, r=1,2 ..., N, N is comprised the phase sum by this yardstick; k ₀Be the bulk modulus as this yardstick blank medium phase; α ₀Calculate according to the following equation:

${\mathrm{\α}}_0=\frac{1}{1+\frac{{4g}_0}{{3k}_0}},$

In formula, g ₀Be the modulus of shearing as this yardstick blank medium phase;

The thermal expansivity of out to out is the thermal expansivity of the clean slurry of sclerosis Portland cement.

In this embodiment, when adopting upwards progressively homogenization method to calculate hardened cement only to starch the thermal expansivity of each yardstick, can use the Self-Consistent method (referring to [Eshelby J.D.The Determination of the Elastic Field of an Ellipsoidal Inclusion and Related Problems[C] .Proceedings of the Royal Society of London Series A, 1957.]), each yardstick blank medium is itself; Also can use the Mori-Tanaka method (referring to [Mori T., Tannaka K.Average Stress in Matrix and Average Elastic Energy of Materials with Misfitting Inclusions[J] .Acta Metallurgica, 1973,21 (5): 571-574.]), the self-reference medium of yardstick I, II, III, IV is respectively low-density hydrated calcium silicate, hydrated calcium silicate, hydrated product, cement slurry solid phase.Specifically comprise the following steps:

The thermal expansivity of step 301, calculating yardstick I: take the low-density hydrated calcium silicate as blank medium, for being mingled with, employing Mori-Tanaka method is calculated the thermal expansivity of the hydrated calcium silicate after homogenising with the high density hydrated calcium silicate; Perhaps with hydrated calcium silicate this as blank medium, adopt the Self-Consistent method to calculate the thermal expansivity of the hydrated calcium silicate after homogenising;

Step 302, calculate the thermal expansivity of yardstick II: the hydrated calcium silicate that calculates take step 301 is as blank medium, for being mingled with, adopts the thermal expansivity of the hydrated product after Mori-Tanaka method calculating homogenising with hydrated products such as calcium hydroxides; Perhaps with hydrated product this as blank medium, adopt the Self-Consistent method to calculate the thermal expansivity of the hydrated product after homogenising;

Step 303, calculate the thermal expansivity of yardstick III: the hydrated product that calculates take step 302 is as blank medium, for not being mingled with, adopts the thermal expansivity of the cement slurry solid phase after Mori-Tanaka method calculating homogenising with hydrated cement particle; Perhaps with the cement slurry solid phase this as blank medium, adopt the Self-Consistent method to calculate the thermal expansivity of the cement slurry solid phase after homogenising;

Step 304, calculate the thermal expansivity of yardstick IV: the cement slurry solid phase that calculates take step 303 is as blank medium, for being mingled with, adopts the cement slurry thermal expansivity after Mori-Tanaka method calculating homogenising with pore water (and/or space); Perhaps, originally as blank medium, for being mingled with, employing Self-Consistent method is calculated the thermal expansivity of the cement slurry after homogenising with pore water (and/or space) with required object yardstick IV.The thermal expansivity of the yardstick IV that tries to achieve at last is the thermal expansivity of the clean slurry of sclerosis Portland cement.

Step 4, adopt different match ratios, the cement paste mixture of variety classes cement, repeating step 2 ~ step 3 obtains the thermal expansivity of different mixture ratio under this curing temperature; Obtain under different curing hardened cement and only starch the volumn concentration of each phase by different curing temperatures is set in step 2, the hardened cement that can obtain different mixture ratio under different curing is starched thermal expansivity only.

The present invention does not need to carry out Real-Time Monitoring by a cover proving installation, can adopt MatLAB, VB etc. according to above-mentioned steps establishment computer software, carries out rapid solving.

In order to verify the effect of the inventive method, carried out following verification experimental verification:

Type I Portland portland cement is adopted in this test, and water cement ratio is 0.3,0.4,0.5,0.6, and the standard curing sclerosis Portland cement of 28 days is starched only, measures its thermal expansivity, and is analyzed with the predicted value of multi-scale prediction model of the present invention.Content of the test is specific as follows:

1, overview

1.1 test starting material

Cement adopts Type I Portland portland cement, its main oxides component such as table 1.

Table 1 cement main oxides component concentration

1.2 testing program

Sample dimensions is 100mm * 100mm * 500mm, builds and test specimen is moved into the standard curing box maintenance 28 days after complete, adopts afterwards thermal expansivity pilot system test thermal expansivity.

1.3 main phase thermal expansivity

The thermal expansivity of each phase of table 2

1.3 test data analyzer

Adopt Origin software to data analysis and drawing.

2, modelling verification and evaluation

Different Water-Cement Ratio hydrated cement paste thermal expansivity trial value and model predication value are as shown in Figure 2.Can find out multiple dimensioned model predication value in the middle of trial value, and have the goodness of fit preferably between prediction curve and measured value, illustrate that this forecast model can characterize the hydrated cement paste thermal expansivity preferably with the rule of development of water cement ratio.The present invention starches thermal expansivity multi-scale prediction model only according to the hardened cement with actual physics meaning parameter that cement component, hydrated product essential attribute and cement paste micromechanism formation and development rule are set up, thereby set up the contact between material microstructure and macro property, this is that prior art is difficult to realize.

Claims (5)

1. the sclerosis Portland cement is starched thermal expansivity multi-scale prediction method only, it is characterized in that, comprises the following steps:

Steps A, the clean slurry of the Portland cement that will harden are divided into different scale according to microstructure, and different scale comprises different typical phases;

Step B, obtain the sclerosis Portland cement only starch the volumn concentration of each phase in different scale;

Step C, from smallest dimension, adopt upwards progressively homogenization method, calculate successively according to following formula the thermal expansivity that the sclerosis Portland cement is starched each yardstick only:

${\mathrm{\α}}_X^{\mathrm{hom}}={\mathrm{\κ}}_X^{\mathrm{hom}}/K_X^{\mathrm{hom}},$

In formula,

Be the thermal expansivity of current yardstick,

With

Be respectively Thermal Stress Coefficient and the bulk modulus of this yardstick, calculate according to the following equation:

${\mathrm{\κ}}_X^{\mathrm{hom}}=\underset{r}{\mathrm{\Σ}}{f}_r{\mathrm{\κ}}_r[1+{\mathrm{\α}}_0(\frac{k_r}{k_0}-1){]}^{-1}\×\{\underset{r}{\mathrm{\Σ}}{f}_r[1+{\mathrm{\α}}_0(\frac{k_r}{k_0}-1){]}^{-1}\},$

$K_X^{\mathrm{hom}}=\underset{r}{\mathrm{\Σ}}{f}_r{k}_r[1+{\mathrm{\α}}_0(\frac{k_r}{k_0}-1){]}^{-1}\×\{\underset{r}{\mathrm{\Σ}}{f}_r[1+{\mathrm{\α}}_0(\frac{k_r}{k_0}-1){]}^{-1}\},$

In formula, k _r, κ _r, f _rBe respectively bulk modulus, Thermal Stress Coefficient, the volumn concentration of this yardstick r phase, r=1,2 ..., N, N is comprised the phase sum by this yardstick; k ₀Be the bulk modulus as this yardstick blank medium phase; α ₀Calculate according to the following equation:

${\mathrm{\α}}_0=\frac{1}{1+\frac{{4g}_0}{{3k}_0}},$

In formula, g ₀Be the modulus of shearing as this yardstick blank medium phase;

The thermal expansivity of out to out is the thermal expansivity of the clean slurry of sclerosis Portland cement.

2. the Portland cement that hardens is as claimed in claim 1 starched thermal expansivity multi-scale prediction method only, it is characterized in that,

The following partition of the scale method of concrete employing in steps A:

Be divided into altogether 4 yardsticks, be followed successively by from small to large: yardstick I, yardstick II, yardstick III, yardstick IV; The yardstick I comprises low-density hydrated calcium silicate and high density hydrated calcium silicate; The yardstick II comprises the hydrated calcium silicate after yardstick I homogenising, and the hydrated product such as calcium hydroxide, entringite, aluminate; The yardstick III comprises the hydrated product after yardstick II homogenising, and hydrated cement particle not; Yardstick IV comprises the cement slurry solid phase after yardstick III homogenising, and pore water and pore space.

3. the Portland cement that hardens is as claimed in claim 2 starched thermal expansivity multi-scale prediction method only, it is characterized in that, when adopting upwards that progressively homogenization method calculates the thermal expansivity of each yardstick of cement paste, use the Self-Consistent method, each yardstick blank medium is itself.

4. the Portland cement that hardens is as claimed in claim 2 starched thermal expansivity multi-scale prediction method only, it is characterized in that, when adopting upwards that progressively homogenization method calculates the thermal expansivity of each yardstick of cement paste, use the Mori-Tanaka method, the self-reference medium of yardstick I, II, III, IV is respectively low-density hydrated calcium silicate, hydrated calcium silicate, hydrated product, cement slurry solid phase.

5. the Portland cement that hardens is as claimed in claim 1 starched thermal expansivity multi-scale prediction method only, it is characterized in that, described sclerosis Portland cement starches only that in different scale, the volumn concentration of each phase is obtained by test, perhaps calculated by the Powers model, perhaps calculated by the Jennings-Tennis model, perhaps calculated by the HYMSTRUC model.

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