CN102288640B - Thermodynamic pore counting method for measuring cement-based material pore structure - Google Patents

Abstract

The invention relates to a method for measuring a cement-based material pore structure, in particular to a thermodynamic pore counting method for measuring internal micropore total volume, micropore shape, porosity, pore radius distribution and the like of a cement-based material. The invention provides a new calculation model for representing the cement-based material pore structure to overcome the defects of the thermodynamic pore counting method in theory from the thermodynamic angle, and then establishes the thermodynamic pore counting method for measuring the cement-based material pore structure by taking the characteristics of the cement-based material into consideration. Compared with other methods, the measuring method has the advantage of avoiding microstructure change caused by vacuum, so that the pore total volume of the micropore, the micropore shape, the porosity and the pore radius distribution can be analyzed and the corresponding relationship between ice and temperature in the cement-based material can be simulated by the thermodynamic pore counting method, and the thermodynamic pore counting method can be applied to further explaining mechanical and thermodynamic performance change mechanisms of the cement-based material at low temperature.

Description

A kind of hot hole meter method of measuring the cement-based material pore structure

Technical field

The present invention relates to a kind of method of measuring the cement-based material pore structure, relate in particular to internal capillary cumulative volume, micropore shape, porosity and pore radius distribution etc. that hot hole meter method is measured cement-based material.

Background technology

Chemistry and physical processes such as the various deterioration processes of xoncrete structure such as freeze thawing, carbonization, infiltration, steel bar corrosion; All relate generally to two main influence factors: water and concrete mesopore or crack, its mesopore and other architectural feature are one of principal elements that influences concrete durability.

At present, the feasible method of existing various mensuration pore structures all is applied to cement-based material.But hot hole meter method is as a kind of emerging hole analytical technology.Because of its saturated sample has been avoided the microstructure change that vacuum caused; And in suitable number of freezing and thawing; Can ignore advantages such as freeze-thaw damage influence, be used for silicon dioxide, titania at present; The research of holes such as elastic body, and be considered to the unique method that can effectively analyze fragility, flexible material and hydrogel hole.But because this technology is not carried out systematic study as yet, thereby fail to be widely used, especially the applied research in cement-based material is very few.Hot hole meter method can be 4nm≤d to diameter not only _DiameterThe micropore of≤100nm carries out size, shape and connective qualitative analysis, can also the quantitative test porosity, and therefore pore diameter distribution is worth using it for the hole research of cement-based material.

Hot hole meter method is applied to cement-based material hole research field also seldom abroad.Only American scholar has been carried out Primary Study to the cement-based material pore structure.Up to date, the domestic report of also not seeing hot hole meter method survey cement-based material pore structure.

Summary of the invention

The present invention adopts hot hole meter method (being also referred to as thermodynamics hole meter method) through differential scanning calorimetry (DSC) research cement-based material pore structure; Especially hot hole meter method is measured micropore cumulative volume, micropore shape, porosity and the pore radius distribution etc. of cement-based material; Purpose is thermodynamic principles of utilizing water in the hole, to freeze; Hot hole meter method is applied to study in the cement-based material, is that a kind of sample of avoiding is impaired, solves the coarse effective ways of other gaging hole technology.

To achieve these goals, the present invention adopts following technical scheme:

Earlier, improve the deficiency of hot hole meter method in theory, propose a kind of computation model of new sign cement-based material pore structure, will consider the cement-based material own characteristic at last, set up the method that hot hole meter method is measured the cement-based material pore structure from the thermodynamics angle.Between the finiteness of experimental apparatus, hot hole meter method has been carried out the research of empirical factor, like the span of experiment temperature range, sample quality optimum range, method for making sample and temperature rate etc.

1. theory part

Hot hole meter method TPM utilizes the icing degree of supercooling of hole solution and thing solidifying enthalpy change to set up aperture and pore volume relation, thereby the pore structure characteristic of porosint is analyzed.Hot hole meter method principle of the present invention describes from water change, the phase transformation of cement-based material hole solution and thing phase enthalpy change theory.

1.1 water alter opinion

Under different temperatures and pressure, water exists with gas-liquid-solid three-phase respectively, like Fig. 1.The O point is unique three-phase equilibrium point of water; The zone is a liquid phase between OC and the OA; The zone is a gas phase between OC and the OB; The zone is a solid phase between OA and the OB.When temperature or pressure change when making water can't reach into the nuclear potential energy requirement, supercooling phenomenon can appear in water, crosses cold-smoothing weighing apparatus curve like OC ' among Fig. 1.

1.2 cement-based material hole solution phase transformation theory

Because cement-based material hole solution pressure is relevant with solid/liquid interfaces curvature.Can set up liquid three-phase equilibrium point and solid/liquid interfaces curvature κ indirectly according to Gibbs-Thomson formula Eq. (1) _CLRelation:

${\mathrm{\γ}}_{\mathrm{CL}}{\mathrm{\κ}}_{\mathrm{CL}}={\∫}_T^{T_M(\∞)}\frac{(S_L-S_C)}{V_L}\mathrm{dT}---\left(1\right)$

Wherein, γ _CLBe the solid/liquid interfaces ability, S _LAnd S _CBe the molar entropy of liquid phase and solid phase, V _LBe the molar volume of liquid phase, T _M(∞) be the melt temperature of solid phase ice (radius is infinitely great).For porosint, the three-phase equilibrium point of its hole solution is determined by the curvature in hole, and the solid/liquid interfaces curvature is relevant with hole dimension, and is as shown in Figure 2.

1.3 thing phase enthalpy change is theoretical

In order to analyze the ice content in the TPM data, must introduce thermodynamics formula (2):

$\mathrm{\ΔS}={\left(\frac{\∂S}{\∂T}\right)}_P\mathrm{dT}+{\left(\frac{\∂S}{\∂P}\right)}_T\mathrm{dP}---\left(2\right)$

Wherein Δ S is an Entropy Changes, and p is a pressure, and v is a volume, and T is a kelvin degree.

Again by thermal capacitance Cp definition and Maxwell relation ${\left(\frac{\∂S}{\∂P}\right)}_T=-{\left(\frac{\∂V}{\∂T}\right)}_P,$ ${\left(\frac{\∂S}{\∂T}\right)}_P=\frac{\mathrm{Cp}}{T},$ Get formula (3):

$\mathrm{\ΔS}=\frac{\mathrm{Cp}}{T}\mathrm{dT}-{\left(\frac{\∂V}{\∂T}\right)}_P\mathrm{dP}---\left(3\right)$

Thus, can get the expression formula (4) that subcooled water solidifies enthalpy is:

$W_{\mathrm{th}}=({\mathrm{\&Delta;<figure-callout\; id="0"\; label="S"\; filenames="HDA0000083292030000011.png,HDA0000083292030000022.png"\; state="\{\{state\}\}">S</figure-callout>}}_0+{\mathrm{\&Delta;S}}_S-{\mathrm{\&Delta;S}}_l+{\mathrm{\&Delta;S}}_{\sup })\&CenterDot;T$

$\&ap;T\&CenterDot;\{{\mathrm{\&Delta;<figure-callout\; id="0"\; label="S"\; filenames="HDA0000083292030000011.png,HDA0000083292030000022.png"\; state="\{\{state\}\}">S</figure-callout>}}_0+{\&Integral;}_{T_0}^T\frac{C_S-C_l}{T}\mathrm{dT}+{[\left(\frac{\&PartialD;V_l}{\&PartialD;T}\right)-{\left(\frac{{\&PartialD;V}_S}{\&PartialD;T}\right)}_P]}_T(P_S-P_o)+\left[{\left(\frac{{\&PartialD;V}_l}{\&PartialD;T}\right)}_P\right](P_L-P_S)\}\&CenterDot;X---\left(4\right)$

Wherein Δ So is-1.2227Jg ^-1K ^-1, Δ Ss is the solid phase Entropy Changes, Δ S _lBe the liquid phase Entropy Changes, Δ Ssup is a surface entropy, and transfer function X is when when cooling, for During intensification, for

T is a kelvin degree, and To is 273.15K, W _ThBe the curing enthalpy change theory function of unit mass liquid phase, p _sBe the suffered pressure of solid phase, p _lBe the suffered pressure of liquid phase, the corresponding pressure Po of normal triple point is 4.58mmHg, and Vs is a solid volume, V _lBe liquid phase volume, solid phase thermal capacitance Cs is 2.114 (1+373.7 Δ T10 ^-5) Jg ^-1, liquid phase thermal capacitance C _lBe 2.114 (1+373.7 Δ T10 ^-5) Jg ^-1

1.4 pass hypothesis

When cement-based material is studied, suppose that usually its hole shape is ball-type or column type, and interconnect mostly between the Kong Yukong.Therefore the present invention supposes the pore size distribution simulation drawing of cement-based material, and intersection, two holes is called pore throat, and inside, hole is called vestibule, and is as shown in Figure 3.After it should be noted that ice crystal has only the pore throat of entering, could continue in vestibule, to grow; Ice is not restricted by pore throat in the hole, then, and is only relevant with the vestibule size.Therefore, the degree of supercooling that ice forms mutually in the temperature-fall period corresponding the pore throat size; And the melting point of icing in the melting process corresponding the vestibule size.

1.5 the computation model of hot hole meter method

Based on above theory and hypothesis, obtain the pore radius Distribution calculation model of hot hole meter method: the relational expression (5) of the long-pending Vice of degree of supercooling Δ T and corresponding ice body and heating up and the relational expression (6) of dv/dr and pore radius r during cooling, shown in (5) and (6).In the time of can adopting differential scanning calorimetry DSC technology respectively to heating and cooling thus; The degree of supercooling of solution and corresponding heat flux P measure in the hole, and according to enthalpy change W=P/v, wherein v is a temperature rate; Because the conventional freezing point of water is 0 ℃; Can be considered the degree of supercooling of water in the hole so DSC surveys the water freezing temperature, below the degree of supercooling Δ T=T with water in the sample well representes, and then obtains the data of the degree of supercooling Δ T and the corresponding enthalpy change w of water in the sample well; Coming the distribution situation of the pore structure of qualitative and quantitative analysis cement-based material, is analytical standard with the distribution situation of pore radius.

Because the degree of supercooling of the Kong Zhongshui of different sizes is different in the testing sample; Therefore the water in the sample begins to undergo phase transition in the process of all water completion phase transformations in the sample, the degree of supercooling of the just corresponding that part of water that under this temperature, undergoes phase transition of each sample temperature; The minimum temperature T of sample temperature T _MinBe not higher than sample interior the temperature of freezing fully of the water in porose, corresponding Δ T _Min=T _Min, maximum temperature T _MaxBe not less than sample interior the temperature of melting fully of the water in porose, corresponding Δ T _Max=T _Max, the unit of T is degree centigrade.

$V_{\mathrm{ice}}={\&Integral;}_{\mathrm{\&Delta;T}1}^{\mathrm{\&Delta;}T\max }\frac{W}{m_d{W}_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)\mathrm{\&rho;}\left(\mathrm{\&Delta;T}\right)}\mathrm{d\&Delta;T}---\left(5\right)$

Ice body in unit mass sample when wherein, sample temperature is Δ T1 amasss Vice.

$\frac{\mathrm{dV}}{\mathrm{dr}}=K(r,n)\&CenterDot;\frac{W}{m_d{W}_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)\mathrm{\&rho;}\left(\mathrm{\&Delta;T}\right)}\&CenterDot;\frac{\mathrm{d\&Delta;T}}{\mathrm{dr}}---\left(6\right)$

During cooling,

$W_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)=(273.15+\mathrm{\&Delta;T})\&CenterDot;\left(\frac{-1.2227-4.88\mathrm{Ln}(1+\frac{\mathrm{\&Delta;T}}{273.15})+10.126\&times;{10}^{-3}\mathrm{\&Delta;T}+1.256\&times;{10}^{-5}{\mathrm{\&Delta;<figure-callout\; id="2"\; label="T"\; filenames="HDA0000083292030000022.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{1-4.556\&CenterDot;{10}^{-5}(\mathrm{\&Delta;T}-0.227{\mathrm{\&Delta;T}}^2)}\right)\&CenterDot;\frac{40.9}{40.9+0.39\mathrm{\&Delta;T}}---\left(10\right)$

During intensification,

$W_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)=(273.15+\mathrm{\&Delta;T})\&CenterDot;\left(\frac{-1.2227-4.88\mathrm{Ln}(1+\frac{\mathrm{\&Delta;T}}{273.15})+10.126\&times;{10}^{-3}\mathrm{\&Delta;T}+1.256\&times;{10}^{-5}{\mathrm{\&Delta;<figure-callout\; id="2"\; label="T"\; filenames="HDA0000083292030000022.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{1-4.556\&CenterDot;{10}^{-5}(\mathrm{\&Delta;T}-0.227{\mathrm{\&Delta;T}}^2)}\right)\&CenterDot;\frac{40.9-0.39\mathrm{\&Delta;T}}{40.9+0.39\mathrm{\&Delta;T}}---\left(11\right)$

ρ(ΔT)≈0.9167-2.053×10 ^-4ΔT-1.357×10 ^-6ΔT ² (12)

$K(r,n)={\left(\frac{r}{r-0.8}\right)}^n---\left(13\right)$

Wherein, m _dBe the quality of dry sample, γ _CLBe solid-liquid body interface ability, shown in (7), V is a pore volume, and r is a pore radius, shown in (8) and (9); W by DSC survey heat up or temperature-fall period in the pairing enthalpy change of degree of supercooling Δ T (W is heat flux P divided by heating up or rate of temperature fall v gets, i.e. W=P/v) of water in the sample well, W _ThThe curing enthalpy theory function that the unit mass liquid phase was emitted when (Δ T) was intensification or cooling is shown in (10) and (11); ρ (Δ T) is a density function, shown in (12); K (r is the function relevant with pass and aperture n), and shown in (13), n is the pass empirical parameter, when micropore is cylindrical hole, and n=2; When micropore is the ball-type hole, n=3.

γ _CL＝(40.9+0.39ΔT)×10 ^-3Nm ^-1 (7)

During cooling, $r=-\frac{64.67}{\mathrm{\&Delta;\; T}}+0.57---\left(8\right)$

During intensification, $r=-\frac{32.33}{\mathrm{\&Delta;\; T}}+0.69---\left(9\right)$

And, can adopt formula (14) to obtain for the judgement of micropore pass.

$\mathrm{\&lambda;}\&ap;\frac{{\mathrm{\&Delta;T}}_{M-\mathrm{Vice}}}{{\mathrm{\&Delta;T}}_{F-\mathrm{Vice}}}---\left(14\right)$

Wherein, Δ T _M-ViceWith Δ T _F-ViceBe that ice content is the long-pending V of same ice body _IceThe time, temperature rise period pairing degree of supercooling Δ T _M-ViceAnd the pairing degree of supercooling Δ of temperature-fall period T _F-Viceλ is the pass coefficient, and when λ＜0.5, micropore is a ball-type; When λ >=0.5, micropore is a cylindrical hole.

According to pore volume and the long-pending transforming relationship formula (16) of ice body, pore volume is carried out integration can obtain formula (15), obtain the cumulative volume V of micropore _Always, with the cumulative volume V of micropore _AlwaysWith the long-pending V of population of samples _AppearanceCompare, can obtain the micropore porosity of sample.

V＝K(r，n)V _ice (16)

Wherein, Δ T _Min=T _Min, Δ T _Max=T _Max

2. experimental procedure and control requirement

According to hot hole meter ratio juris, can experimentize as testing tool by the differential scanning calorimeter of differential scanning calorimetry DSC.

When sample preparation, the reply sample is taked identical disposal route, makes the pore diameter distribution difference between the sample minimum.Should earlier sample be dried and claim appearance, put into deionized water again, saturated subsequent use through vacuum water, and the hole solution of assumes samples does not have the ion existence that influences water freezing.

The condition of DSC test: the DSC test comprises temperature rise period and temperature-fall period, and temperature rate is constant, and temperature rate v all is controlled to be the arbitrary value among 10～0.15 ℃/min; Wherein, the minimum temperature T of sample temperature T _MinBe not higher than sample interior the temperature of freezing fully of the water in porose, corresponding Δ T _Min=T _Min, maximum temperature T _MaxBe not less than sample interior the temperature of melting fully of the water in porose, corresponding Δ T _Max=T _Max, the unit of T is degree centigrade.

Preferable, the sample temperature of DSC test is controlled in-80 ℃～+ 10 ℃; Better, the sample temperature scope is controlled at-40 ℃～5 ℃; Best, the sample temperature scope is controlled at-40 ℃～0 ℃; The heating-cooling speed range all is controlled at 3～0.3 ℃/min.

Can obtain internal capillary cumulative volume, micropore shape, porosity and the pore radius distribution etc. of cement-based material according to above-mentioned method of testing, and obtain the pore structure situation of cement-based material thus.

With data by MoM and MEI; Advantage of the present invention mainly contains: avoided the microstructure change that vacuum caused; Make hot hole meter method not only can analyze size, shape, connectedness, porosity and the pore diameter distribution of micropore, can also simulate the corresponding relation of icing in the cement-based material with temperature.This can be used for further explaining cement-based material mechanics and thermal property change mechanism at low temperatures.

Description of drawings

Fig. 1 water becomes figure

Ice/water state the typical figure of the saturated porosint of Fig. 2 in carrying out hot hole meter method test process

Wherein, γ _SlRepresent the frozen water interfacial energy, r representative ice subsequent corrosion, r _pRepresent pore radius, the suffered pressure of Ps representative ice, P _lRepresent the suffered pressure of water, θ represents the contact angle of solid phase s and liquid phase l

Fig. 3 mixing pass distribution simulation figure

Fig. 4 DSC gained raw data

Ice content and the temperature relation figure of Fig. 5 sample in the freeze thawing circulation

The pore size distribution curve that Fig. 6 is obtained respectively at intensification-temperature-fall period by hot hole meter method

Embodiment

Further set forth the present invention below in conjunction with specific embodiment, should be understood that these embodiment only are used to the present invention is described and are not used in restriction protection scope of the present invention.

Embodiment 1

Present embodiment is that 0.6 cement stone is example with water cement ratio:

(1) processes sheet to sample earlier, can put into the DSC aluminium crucible of differential scanning calorimeter;

(2) put into 60 ℃ of drying boxes again and be dried to constant weight, claim its weight m _d=8.71mg; Measure the cumulative volume V of cement-based material sample _Appearance=18.47mm ³

(3) subsequently sample is put into deionized water, saturated processing is placed on crucible and waits for the DSC test through vacuum water.For making experimental data more accurate, need on sample, to drip kerosene, again crucible is sealed;

(4) experiment condition that DSC tests is set, wherein the sample temperature T of DSC test is controlled to be-40 ℃～+ 5 ℃, and heating-cooling speed is 0.3 ℃/min.Obtain the data of sample temperature T and corresponding heat flux P thus, raw data origin derives the graph of a relation that obtains P and T thus, and is as shown in Figure 4; Wherein, the minimum temperature T of sample temperature T _MinBe not higher than sample interior the temperature of freezing fully of the water in porose, corresponding Δ T _Min=T _Min, maximum temperature T _MaxBe not less than sample interior the temperature of melting fully of the water in porose, corresponding Δ T _Max=T _Max, the unit of T is degree centigrade.

(5) Fig. 4 is carried out after baseline handles, according to W=P/v, wherein v is a temperature rate; The degree of supercooling Δ T=T of water in the sample well; With heat flux P data conversion is enthalpy change W, obtains the data of degree of supercooling Δ T with the corresponding enthalpy change W of water in the sample well, the sample quality m that step (2) is measured _dIn enthalpy change W substitution formula (5), and bonding unit quality liquid phase is emitted curing enthalpy theory function W _Th(Δ T) formula (10) and formula (11)) and density function ρ (Δ T) formula (12), obtain the corresponding relation figure of degree of supercooling Δ T and the long-pending Vice of corresponding ice body, as shown in Figure 5.By the corresponding relation figure of degree of supercooling Δ T in the cement-based material with the long-pending Vice of corresponding ice body; Can qualitatively judge out in pore radius r less than freezing and the thawing curvilinear trend in the 100nm micropore; And quantitatively obtain in the sample under the long-pending Vice of same ice body temperature rise period pairing degree of supercooling Δ T _M-ViceWith the pairing degree of supercooling Δ of temperature-fall period T _F-Vice, from Fig. 5, also can quantitatively obtain the amount that institute's cryohydrate amasss in the sample well under a certain degree of supercooling, wherein the total ice amount in this hole dimension scope is 0.16mL/g.

$V_{\mathrm{ice}}={\&Integral;}_{\mathrm{\&Delta;}T\min }^{\mathrm{\&Delta;}T\max }\frac{W}{m_d{W}_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)\mathrm{\&rho;}\left(\mathrm{\&Delta;T}\right)}\mathrm{d\&Delta;T}---\left(5\right)$

During cooling,

$W_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)=(273.15+\mathrm{\&Delta;T})\&CenterDot;\left(\frac{-1.2227-4.88\mathrm{Ln}(1+\frac{\mathrm{\&Delta;T}}{273.15})+10.126\&times;{10}^{-3}\mathrm{\&Delta;T}+1.256\&times;{10}^{-5}{\mathrm{\&Delta;<figure-callout\; id="2"\; label="T"\; filenames="HDA0000083292030000022.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{1-4.556\&CenterDot;{10}^{-5}(\mathrm{\&Delta;T}-0.227{\mathrm{\&Delta;T}}^2)}\right)\&CenterDot;\frac{40.9}{40.9+0.39\mathrm{\&Delta;T}}$

(10)

During intensification,

$W_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)=(273.15+\mathrm{\&Delta;T})\&CenterDot;\left(\frac{-1.2227-4.88\mathrm{Ln}(1+\frac{\mathrm{\&Delta;T}}{273.15})+10.126\&times;{10}^{-3}\mathrm{\&Delta;T}+1.256\&times;{10}^{-5}{\mathrm{\&Delta;<figure-callout\; id="2"\; label="T"\; filenames="HDA0000083292030000022.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{1-4.556\&CenterDot;{10}^{-5}(\mathrm{\&Delta;T}-0.227{\mathrm{\&Delta;T}}^2)}\right)\&CenterDot;\frac{40.9-0.39\mathrm{\&Delta;T}}{40.9+0.39\mathrm{\&Delta;T}}---\left(11\right)$

ρ(ΔT)≈0.9167-2.053×10 ^-4ΔT-1.357×10 ^-6ΔT ² (12)

(6) obtain the micropore shape: with the long-pending pairing Δ T of Vice of resulting same ice body in the step (5) _M-ViceWith Δ T _F-ViceIn the substitution formula (14), obtain the value of pass coefficient lambda, and judge the shape of the micropore at the water place that correspondence undergoes phase transition under the long-pending Vice of this ice body according to the size of λ, judgment criterion is: λ＜0.5 o'clock, and micropore is the ball-type hole; λ>=0.5 o'clock, micropore is a cylindrical hole, and present embodiment obtains thus, and water cement ratio is that the micropore (λ is all>=0.5) at the water place that correspondence undergoes phase transition under the long-pending Vice of this ice body in 0.6 the cement stone sample is cylindrical hole;

$\mathrm{\&lambda;}\&ap;\frac{{\mathrm{\&Delta;T}}_{M-\mathrm{Vice}}}{{\mathrm{\&Delta;T}}_{F-\mathrm{Vice}}}---\left(14\right)$

(7) obtaining the micropore pore radius distributes: obtain the graph of a relation of dv/dr and pore radius r according to formula (6), wherein V represents pore volume, obtains respectively to heat up and pore radius distribution when lowering the temperature according to the graph of a relation of dv/dr and r; From Fig. 6, can know, survey that pairing pore radius distribution range is 3～60nm when heating up; Pairing pore radius distribution range is 3～90nm during cooling.And the most probable size is respectively 4nm and 6nm in cooling and the intensification institute corresponding aperture radius distribution;

$\frac{\mathrm{dV}}{\mathrm{dr}}=K(r,n)\&CenterDot;\frac{W}{m_d{W}_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)\mathrm{\&rho;}\left(\mathrm{\&Delta;T}\right)}\&CenterDot;\frac{\mathrm{d\&Delta;T}}{\mathrm{dr}}---\left(6\right)$

During cooling, $r=-\frac{64.67}{\mathrm{\&Delta;\; T}}+0.57---\left(8\right)$

During intensification, $r=-\frac{32.33}{\mathrm{\&Delta;\; T}}+0.69---\left(9\right)$

$K(r,n)={\left(\frac{r}{r-0.8}\right)}^n---\left(13\right)$

Wherein, and K (r n) is the function relevant with pass and pore radius, and n is the pass empirical parameter, when micropore is cylindrical hole, and n=2, when micropore is the ball-type hole, n=3;

Pore radius according to the micropore in the nitrogen absorption method of testing specimen of the prior art distributes, and its result shows the pore radius distribution basically identical with the present embodiment gained.

(8) obtain the micropore porosity: the cumulative volume V that obtains micropore according to formula (15) _Always, with the cumulative volume V of micropore _AlwaysWith the long-pending V of population of samples _AppearanceCompare, obtain the micropore porosity of sample; Obtained by the present embodiment experiment, the shared porosity of the micropore of pore radius r＜100nm is 0.13.

Wherein, Δ T _Min=T _Min, Δ T _Max=T _Max

Embodiment 2

Present embodiment is that 0.6 cement stone is example with water cement ratio:

(1) processes sheet to sample earlier, can put into the DSC aluminium crucible of differential scanning calorimeter;

(2) put into 60 ℃ of drying boxes again and be dried to constant weight, claim its weight m _d=8.80mg; Measure the cumulative volume V of cement-based material sample _Appearance=18.48mm ³

(3) subsequently sample is put into deionized water, saturated processing is placed on crucible and waits for the DSC test through vacuum water.For making experimental data more accurate, need on sample, to drip kerosene, again crucible is sealed;

(4) experiment condition that DSC tests is set, wherein the sample temperature T of DSC test is controlled to be-40 ℃～+ 0 ℃, and heating-cooling speed is 3 ℃/min.Obtain the data of sample temperature T and corresponding heat flux P thus, raw data origin derives the graph of a relation that obtains P and T thus; Wherein, the minimum temperature T of sample temperature T _MinBe not higher than sample interior the temperature of freezing fully of the water in porose, corresponding Δ T _Min=T _Min, maximum temperature T _MaxBe not less than sample interior the temperature of melting fully of the water in porose, corresponding Δ T _Max=T _Max, the unit of T is degree centigrade.

(5) according to W=P/v, wherein v is a temperature rate, and the degree of supercooling Δ T=T of water is enthalpy change W with heat flux P data conversion in the sample well, obtains the data of degree of supercooling Δ T with the corresponding enthalpy change W of water in the sample well, the sample quality m that step (2) is measured _dIn enthalpy change W substitution formula (5), and bonding unit quality liquid phase is emitted curing enthalpy theory function W _Th(Δ T) formula (10) and formula (11)) and density function ρ (Δ T) formula (12), obtain the corresponding relation figure of degree of supercooling Δ T and the long-pending Vice of corresponding ice body.By the corresponding relation figure of degree of supercooling Δ T in the cement-based material with the long-pending Vice of corresponding ice body; Can qualitatively judge out in pore radius r less than freezing and the thawing curvilinear trend in the 100nm micropore; And quantitatively obtain in the sample under the long-pending Vice of same ice body temperature rise period pairing degree of supercooling Δ T _M-ViceWith the pairing degree of supercooling Δ of temperature-fall period T _F-Vice, from figure, also can quantitatively obtain the amount that institute's cryohydrate amasss in the sample well under a certain degree of supercooling, wherein the total ice amount in this hole dimension scope is 0.17mL/g.

$V_{\mathrm{ice}}={\&Integral;}_{\mathrm{\&Delta;}T\min }^{\mathrm{\&Delta;}T\max }\frac{W}{m_d{W}_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)\mathrm{\&rho;}\left(\mathrm{\&Delta;T}\right)}\mathrm{d\&Delta;T}---\left(5\right)$

During cooling,

$W_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)=(273.15+\mathrm{\&Delta;T})\&CenterDot;\left(\frac{-1.2227-4.88\mathrm{Ln}(1+\frac{\mathrm{\&Delta;T}}{273.15})+10.126\&times;{10}^{-3}\mathrm{\&Delta;T}+1.256\&times;{10}^{-5}{\mathrm{\&Delta;<figure-callout\; id="2"\; label="T"\; filenames="HDA0000083292030000022.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{1-4.556\&CenterDot;{10}^{-5}(\mathrm{\&Delta;T}-0.227{\mathrm{\&Delta;T}}^2)}\right)\&CenterDot;\frac{40.9}{40.9+0.39\mathrm{\&Delta;T}}---\left(10\right)$

During intensification,

$W_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)=(273.15+\mathrm{\&Delta;T})\&CenterDot;\left(\frac{-1.2227-4.88\mathrm{Ln}(1+\frac{\mathrm{\&Delta;T}}{273.15})+10.126\&times;{10}^{-3}\mathrm{\&Delta;T}+1.256\&times;{10}^{-5}{\mathrm{\&Delta;<figure-callout\; id="2"\; label="T"\; filenames="HDA0000083292030000022.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}{1-4.556\&CenterDot;{10}^{-5}(\mathrm{\&Delta;T}-0.227{\mathrm{\&Delta;T}}^2)}\right)\&CenterDot;\frac{40.9-0.39\mathrm{\&Delta;T}}{40.9+0.39\mathrm{\&Delta;T}}---\left(11\right)$

ρ(ΔT)≈0.9167-2.053×10 ^-4ΔT-1.357×10 ^-6ΔT ² (12)

(6) obtain the micropore shape: with the long-pending pairing Δ T of Vice of resulting same ice body in the step (5) _M-ViceWith Δ T _F-ViceIn the substitution formula (14), obtain the value of pass coefficient lambda, and judge the shape of the micropore at the water place that correspondence undergoes phase transition under the long-pending Vice of this ice body according to the size of λ, judgment criterion is: λ＜0.5 o'clock, and micropore is the ball-type hole; λ>=0.5 o'clock, micropore is a cylindrical hole, and present embodiment obtains thus, and water cement ratio is that the micropore (λ is all>=0.5) at the water place that correspondence undergoes phase transition under the long-pending Vice of this ice body in 0.6 the cement stone sample is cylindrical hole;

$\mathrm{\&lambda;}\&ap;\frac{{\mathrm{\&Delta;T}}_{M-\mathrm{Vice}}}{{\mathrm{\&Delta;T}}_{F-\mathrm{Vice}}}---\left(14\right)$

(7) obtaining the micropore pore radius distributes: obtain the graph of a relation of dv/dr and pore radius r according to formula (6), wherein V represents pore volume, obtains respectively to heat up and pore radius distribution when lowering the temperature according to the graph of a relation of dv/dr and r; Can know that from figure it is 3～60nm that institute surveys when intensification pairing pore radius distribution range; Pairing pore radius distribution range is 3～90nm during cooling.And the most probable size is respectively 4nm and 6nm in cooling and the intensification institute corresponding aperture radius distribution;

$\frac{\mathrm{dV}}{\mathrm{dr}}=K(r,n)\&CenterDot;\frac{W}{m_d{W}_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)\mathrm{\&rho;}\left(\mathrm{\&Delta;T}\right)}\&CenterDot;\frac{\mathrm{d\&Delta;T}}{\mathrm{dr}}---\left(6\right)$

During cooling, $r=-\frac{64.67}{\mathrm{\&Delta;\; T}}+0.57---\left(8\right)$

During intensification, $r=-\frac{32.33}{\mathrm{\&Delta;\; T}}+0.69---\left(9\right)$

$K(r,n)={\left(\frac{r}{r-0.8}\right)}^n---\left(13\right)$

Wherein, and K (r n) is the function relevant with pass and pore radius, and n is the pass empirical parameter, when micropore is cylindrical hole, and n=2, when micropore is the ball-type hole, n=3;

Pore radius according to the micropore in the nitrogen absorption method of testing specimen of the prior art distributes, and its result shows the pore radius distribution basically identical with the present embodiment gained.

(8) obtain the micropore porosity: the cumulative volume V that obtains micropore according to formula (15) _Always, with the cumulative volume V of micropore _AlwaysWith the long-pending V of population of samples _AppearanceCompare, obtain the micropore porosity of sample; Obtained by the present embodiment experiment, the shared porosity of the micropore of pore radius r＜100nm is 0.132.

Wherein, Δ T _Min=T _Min, Δ T _Max=T _Max

Thermodynamics provided by the present invention hole meter method can remedy the deficiency of other hole measuring method, and can carry out qualitative comparatively all sidedly or quantitatively characterizing to the cement-based material pore structure.

Claims (6)

1. a method of measuring the cement-based material pore structure comprises that internal capillary cumulative volume, micropore shape, porosity and the pore radius of measuring cement-based material distribute, and specifically comprise the steps:

(1) with cement-based material sample drying to constant weight and claim its weight m _dMeasure the cumulative volume V of cement-based material sample _Appearance

(2) dried sample is put into deionized water, subsequent use through the saturated processing of vacuum water back;

(3) place the crucible of differential scanning calorimeter to carry out the DSC test in sample; Obtain the data of sample temperature T and corresponding heat flux P; According to enthalpy change W=P/v; Wherein v is a temperature rate, and the degree of supercooling Δ T=T of water in the sample well obtains the data of degree of supercooling Δ T with the corresponding enthalpy change W of water in the sample well; The controlled condition of said DSC test is: the DSC test comprises temperature rise period and temperature-fall period, and temperature rate is constant, and temperature rate v all is controlled to be the arbitrary value among 0.15 ~ 10 ° of C/min; Wherein, the minimum temperature T of sample temperature T _MinBe not higher than sample interior the temperature of freezing fully of the water in porose, corresponding Δ T _Min=T _Min, maximum temperature T _MaxBe not less than sample interior the temperature of melting fully of the water in porose, corresponding Δ T _Max=T _Max, the unit of T is degree centigrade;

(4), obtain the corresponding relation figure of the long-pending Vice of degree of supercooling Δ T and corresponding ice body according to formula (5);

$V_{\mathrm{ice}}={\&Integral;}_{\mathrm{\&Delta;T}1}^{\mathrm{\&Delta;}T\max }\frac{W}{m_d{W}_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)\mathrm{\&rho;}\left(\mathrm{\&Delta;T}\right)}\mathrm{d\&Delta;T}---\left(5\right)$

Ice body in unit mass sample when wherein, sample temperature is Δ T1 amasss Vice;

During cooling,

$W_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)=(273.15+\mathrm{\&Delta;T})\&CenterDot;\left(\frac{-1.2227-4.88\mathrm{Ln}(1+\frac{\mathrm{\&Delta;T}}{273.15})+10.126\&times;{10}^{-3}\mathrm{\&Delta;T}+1.256\&times;{10}^{-5}\mathrm{\&Delta;}{T}^2}{1-4.556\&CenterDot;{10}^{-5}(\mathrm{\&Delta;T}-0.227\mathrm{\&Delta;}{T}^2)}\right)\&CenterDot;\frac{40.9}{40.9+0.39\mathrm{\&Delta;T}}---\left(10\right)$

During intensification,

$W_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)=(273.15+\mathrm{\&Delta;T})\&CenterDot;\left(\frac{-1.2227-4.88\mathrm{Ln}(1+\frac{\mathrm{\&Delta;T}}{273.15})+10.126\&times;{10}^{-3}\mathrm{\&Delta;T}+1.256\&times;{10}^{-5}\mathrm{\&Delta;}{T}^2}{1-4.556\&CenterDot;{10}^{-5}(\mathrm{\&Delta;T}-0.227\mathrm{\&Delta;}{T}^2)}\right)\&CenterDot;\frac{40.9-0.39\mathrm{\&Delta;T}}{40.9+0.39\mathrm{\&Delta;T}}---\left(11\right)$

ρ(ΔT)≈0.9167-2.053×10 ^-4ΔT-1.357×10 ^-6ΔT ² (12)

Wherein, the curing enthalpy theory function that the unit mass liquid phase was emitted when Wth (Δ T) was intensification or cooling, ρ (Δ T) is a density function;

(5) according to degree of supercooling Δ T and the long-pending V of corresponding ice body _IceCorresponding relation figure, qualitatively judge among the pore radius r less than freezing and melt curvilinear trend in the 100nm micropore, and quantitatively obtain in the sample under the long-pending Vice of same ice body temperature rise period pairing degree of supercooling Δ T _M-ViceWith the pairing degree of supercooling Δ of temperature-fall period T _F-Vice

(6) obtain the micropore shape: with the long-pending pairing Δ T of Vice of resulting same ice body in the step (5) _M-ViceWith Δ T _F-ViceIn the substitution formula (14), obtain the value of pass coefficient lambda, and judge the shape of the micropore at the water place that correspondence undergoes phase transition under the long-pending Vice of this ice body according to the size of λ: λ＜0.5 o'clock, micropore is the ball-type hole; λ>=0.5 o'clock, micropore is a cylindrical hole;

$\mathrm{\&lambda;}\&ap;\frac{\mathrm{\&Delta;}{T}_{M-\mathrm{Vice}}}{\mathrm{\&Delta;}{T}_{F-\mathrm{Vice}}}---\left(14\right)$

(7) obtaining the micropore pore radius distributes: obtain the graph of a relation of dv/dr and pore radius r according to formula (6), wherein V represents pore volume, obtains respectively to heat up and pore radius distribution when lowering the temperature according to the graph of a relation of dv/dr and r;

$\frac{\mathrm{dV}}{\mathrm{dr}}=K(r,n)\&CenterDot;\frac{W}{m_d{W}_{\mathrm{th}}\left(\mathrm{\&Delta;T}\right)\mathrm{\&rho;}\left(\mathrm{\&Delta;T}\right)}\&CenterDot;\frac{\mathrm{d\&Delta;T}}{\mathrm{dr}}---\left(6\right)$

During cooling, $r=-\frac{64.67}{\mathrm{\&Delta;\; T}}+0.57---\left(8\right)$

During intensification, $r=-\frac{32.33}{\mathrm{\&Delta;\; T}}+0.69---\left(9\right)$

$K(r,n)={\left(\frac{r}{r-0.8}\right)}^n---\left(13\right)$

Wherein, and K (r n) is the function relevant with pass and pore radius, and n is the pass empirical parameter, when micropore is cylindrical hole, and n=2, when micropore is the ball-type hole, n=3;

(8) obtain the micropore porosity: the cumulative volume V that obtains micropore according to formula (15) _Always, with the cumulative volume V of micropore _AlwaysWith the long-pending V of population of samples _AppearanceCompare, obtain the micropore porosity of sample;

Wherein, Δ T _Min=T _Min, Δ T _Max=T _Max

2. the method for the mensuration cement-based material pore structure shown in claim 1 is characterized in that, in the step (3), the scope of said sample temperature T is controlled to be-80 ° of C ~+10 ° C.

3. the method for the mensuration cement-based material pore structure shown in claim 1 is characterized in that, in the step (3), said sample temperature scope is controlled to be-40 ° of C ~ 5 ° C.

4. the method for the mensuration cement-based material pore structure shown in claim 1 is characterized in that, in the step (3), the speed range of said heating-cooling all is controlled to be 0.3 ~ 3 ° of C/min.

5. the method for the mensuration cement-based material pore structure shown in claim 1 is characterized in that, in the step (1), processes sheet earlier before the said cement-based material sample drying.

6. like the application of method in the cement based porosint is measured and analyzed of the mensuration cement-based material pore structure shown in claim 1-5 is arbitrary.

Images