CN104050387A - Concrete thermal expansion coefficient prediction model construction method - Google Patents

Abstract

The invention discloses a concrete thermal expansion coefficient prediction model construction method and belongs to the technical field of cement-based materials. Concrete adopted in the method is a composite material formed by cement paste, sand and stone. The method includes the steps that influences of the related performance of component materials in the concrete such as the cement paste, the sand and the stone on concrete thermal expansion coefficients are studied, and influences of mutual actions and deformation characteristics of the cement paste, the sand and the stone on the concrete thermal expansion coefficients in the temperature change process are studied; the concrete thermal expansion coefficients are predicted according to the thermal expansion coefficients, the volume fraction and bulk modulus of the cement paste, the sand and the stone, and then a concrete thermal expansion coefficient prediction model is established. According to the method, the influences of the component materials and relative composition of the concrete on the concrete thermal expansion coefficients are considered, and the concrete thermal expansion coefficients can be conveniently and accurately predicted according to the thermal expansion coefficients, the volume fraction and the bulk modulus of the component materials.

Description

A kind of construction method of thermal expansion coefficient of concrete forecast model

Technical field

The present invention relates to a kind of construction method of thermal expansion coefficient of concrete forecast model, belong to cement-based material technical field.

Background technology

Thermal expansivity is one of concrete main thermal properties, is also the important characterization parameter of its volume stability.In Practical Project, the temperature deformation causing due to hydration heat is the one of the main reasons that causes xoncrete structure cracking, especially for large volume concrete structural.Thermal expansivity has directly determined the size of temperature deformation, and one of key that solves concrete temperature problem of Cracking is exactly determining of thermal expansivity.

At present for the value of thermal expansion coefficient of concrete, conventionally approximately adopt fixed value, and in fact concrete thermal expansivity is subject to various factors, as match ratio, thick, fine aggregate kind etc.To the research of thermal expansion coefficient of concrete under different operating modes, how present stage is undertaken by test method, but it is strongly professional that thermal expansion coefficient of concrete is tested required test apparatus, test operation process complexity, testing expenses are higher, and test findings is also subject to the impacts such as starting material, match ratio, environmental baseline and testing crew operative technique, the thermal expansivity discreteness often obtaining is larger, and generalization is inadequate.Therefore, explore one not only practicality but also rational thermal expansion coefficient of concrete forecast model, significant for control Concrete Structure Temperature cracking and the evaluation of ftractureing.

Summary of the invention

Technical matters to be solved by this invention is to overcome the existing deficiency of prior art, the invention provides a kind of construction method of thermal expansion coefficient of concrete forecast model, based on thin sight angle, the performance of research concrete different component material and the impact interacting each other on thermal expansion coefficient of concrete, directly predict concrete thermal expansivity according to each performance parameter of concrete component material, for the control of Temperature Cracks of Reinforced Concrete Structure provides reliable parameter.

For addressing the above problem, the present invention specifically by the following technical solutions:

A construction method for thermal expansion coefficient of concrete forecast model, is characterized in that: comprises the following steps,

Step (A), set up the mixed-mode of thermal expansion coefficient of concrete:

When concrete temperature variation, ignore the interaction between cement paste and sand, stone, respectively equal independent deformation mutually, calculates concrete thermal expansivity according to mixed-mode,

α _c1＝α _cpf _cp+α _sf _s+α _gf _g (1)

In formula (1), α _c1for the concrete thermal expansivity calculating by mixed-mode, α _cp, α _s, α _gbe respectively the thermal expansivity of cement paste, sand and stone, f _cp, f _sand f _gbe respectively cement paste, sand and stone shared volume fraction in concrete;

Step (B), set up the Turner model of thermal expansion coefficient of concrete:

When concrete temperature variation, cement paste and sand, stone bear uniform hydrostatic stress and are homogeneous deformation, calculate concrete thermal expansivity according to Turner model,

${\mathrm{\α}}_{c2}=\frac{{\mathrm{\α}}_{\mathrm{cp}}{f}_{\mathrm{cp}}{K}_{\mathrm{cp}}+{\mathrm{\α}}_s{f}_s{K}_s+{\mathrm{\α}}_g{f}_g{K}_g}{f_{\mathrm{cp}}{K}_{\mathrm{cp}}+f_s{K}_s+f_g{K}_g}---\left(2\right)$

In formula (2), α _c2for the concrete thermal expansivity calculating by Turner model, K _cp, K _sand K _gbe respectively the bulk modulus of cement paste, sand and stone;

Step (C), set up the forecast model of thermal expansion coefficient of concrete:

In reality, between concrete component material cement paste and sand, stone, exist and interact, and distortion is constraint mutually, between step (A), (B) described two kinds of situations, taking two kinds of models described in step (A), (B) as basis, set up the forecast model of thermal expansion coefficient of concrete, as follows

α _c＝λ ₁α _c1+λ ₂α _c2 (3)

${\mathrm{\α}}_c={\mathrm{\λ}}_1({\mathrm{\α}}_{\mathrm{cp}}{f}_{\mathrm{cp}}+{\mathrm{\α}}_s{f}_s+{\mathrm{\α}}_g{f}_g)+{\mathrm{\λ}}_2\·\frac{{\mathrm{\α}}_{\mathrm{cp}}{f}_{\mathrm{cp}}{K}_{\mathrm{cp}}+{\mathrm{\α}}_s{f}_s{K}_s+{\mathrm{\α}}_g{f}_g{K}_g}{f_{\mathrm{cp}}{K}_{\mathrm{cp}}+f_s{K}_s+f_g{K}_g}---\left(4\right)$

In formula (3) and formula (4), α _cfor the concrete thermal expansivity that prediction obtains, λ ₁, λ ₂for combination coefficient, and λ ₁+ λ ₂=1, λ ₁and λ ₂represent respectively press thermal expansion coefficient of concrete that mixed-mode and Turner model the calculate percentage contribution to concrete thermal expansivity under the actual conditions of predicting.

The construction method of aforesaid a kind of thermal expansion coefficient of concrete forecast model, is characterized in that: concrete is the three-phase composite material of cement paste, sand, stone composition.

The construction method of aforesaid a kind of thermal expansion coefficient of concrete forecast model, is characterized in that: in step (C), exist and interact and distortion constraint mutually between cement paste and sand, stone, combination coefficient is got respectively λ ₁=λ ₂=0.5, concrete thermal expansivity obtains by the direct prediction of following formula,

${\mathrm{\α}}_c=0.5({\mathrm{\α}}_{\mathrm{cp}}{f}_{\mathrm{cp}}+{\mathrm{\α}}_s{f}_s+{\mathrm{\α}}_g{f}_g)+0.5\·\frac{{\mathrm{\α}}_{\mathrm{cp}}{f}_{\mathrm{cp}}{K}_{\mathrm{cp}}+{\mathrm{\α}}_s{f}_s{K}_s+{\mathrm{\α}}_g{f}_g{K}_g}{f_{\mathrm{cp}}{K}_{\mathrm{cp}}+f_s{K}_s+f_g{K}_g}.---\left(5\right)$

The forecast model of this thermal expansion coefficient of concrete has considered the bulk modulus of the bulk modulus of the bulk modulus of the thermal expansivity of the thermal expansivity of the thermal expansivity of cement paste, sand, stone, cement paste, sand, stone, volume fraction, the volume fraction of sand and the impact of the volume fraction of stone on thermal expansion coefficient of concrete of cement paste in concrete, and has considered interaction and the impact of deformation constrain on thermal expansion coefficient of concrete mutually between cement paste and sand, stone.

Beneficial effect of the present invention: the construction method of a kind of thermal expansion coefficient of concrete forecast model provided by the invention, wherein concrete is the three-phase composite material being made up of cement paste and sand, stone, interaction and the impact of deformation constrain on concrete thermal expansivity between cement paste and sand, stone are considered, according to thermal expansivity, volume fraction and the bulk modulus of cement paste and sand, stone, measurablely obtain concrete thermal expansivity.The present invention is from thin sight level, research cement paste and sand, the performance of stone, interaction and the impact of deformation characteristics on thermal expansion coefficient of concrete each other, set up a kind of not only Applied economy but also computation model that can correct Prediction thermal expansion coefficient of concrete, pass through the inventive method, can obtain eaily concrete thermal expansivity, and do not need to test by proving installation, greatly save and tested time used, man power and material, save fund input, and it is reliable to predict the outcome, and is conducive to apply.

Embodiment

Below technical scheme of the present invention is elaborated.

Model building method of the present invention carries out according to following steps, and concrete is the three-phase composite material of cement paste and sand, stone composition, carries out on this basis following steps:

Step (A), set up the mixed-mode of thermal expansion coefficient of concrete:

When concrete temperature variation, suppose a kind of perfect condition, ignore the interaction between cement paste and sand, stone, and think each equal independent deformation mutually, calculate concrete thermal expansivity according to mixed-mode,

α _c1＝α _cpf _cp+α _sf _s+α _gf _g (1)

In formula (1), α _c1for the concrete thermal expansivity calculating by mixed-mode, α _cp, α _s, α _gbe respectively the thermal expansivity of cement paste, sand and stone, f _cp, f _sand f _gbe respectively cement paste, sand and stone shared volume fraction in concrete;

Step (B), set up the Turner model of thermal expansion coefficient of concrete:

When concrete temperature variation, suppose that perfect condition is, cement paste and sand, stone bear uniform hydrostatic stress and are homogeneous deformation, calculate concrete thermal expansivity according to Turner model,

${\mathrm{\α}}_{c2}=\frac{{\mathrm{\α}}_{\mathrm{cp}}{f}_{\mathrm{cp}}{K}_{\mathrm{cp}}+{\mathrm{\α}}_s{f}_s{K}_s+{\mathrm{\α}}_g{f}_g{K}_g}{f_{\mathrm{cp}}{K}_{\mathrm{cp}}+f_s{K}_s+f_g{K}_g}---\left(2\right)$

In formula (2), α _c2for the concrete thermal expansivity calculating by Turner model, K _cp, K _sand K _gbe respectively the bulk modulus of cement paste, sand and stone;

Step (C), set up the forecast model of thermal expansion coefficient of concrete:

In reality, between concrete component material cement paste and sand, stone, exist and interact, and distortion is constraint mutually, between step (A), (B) described two kinds of situations, taking two kinds of models described in step (A), (B) as basis, set up the forecast model of thermal expansion coefficient of concrete, as follows

α _c＝λ ₁α _c1+λ ₂α _c2 (3)

${\mathrm{\α}}_c={\mathrm{\λ}}_1({\mathrm{\α}}_{\mathrm{cp}}{f}_{\mathrm{cp}}+{\mathrm{\α}}_s{f}_s+{\mathrm{\α}}_g{f}_g)+{\mathrm{\λ}}_2\·\frac{{\mathrm{\α}}_{\mathrm{cp}}{f}_{\mathrm{cp}}{K}_{\mathrm{cp}}+{\mathrm{\α}}_s{f}_s{K}_s+{\mathrm{\α}}_g{f}_g{K}_g}{f_{\mathrm{cp}}{K}_{\mathrm{cp}}+f_s{K}_s+f_g{K}_g}---\left(4\right)$

In formula (3) and formula (4), α _cfor the concrete thermal expansivity that prediction obtains, λ ₁, λ ₂for combination coefficient, and λ ₁+ λ ₂=1, λ ₁and λ ₂represent respectively press thermal expansion coefficient of concrete that mixed-mode and Turner model the calculate percentage contribution to concrete thermal expansivity under the actual conditions of predicting.

Generally, exist and interact and distortion constraint mutually between cement paste and sand, stone, combination coefficient is got respectively λ ₁=λ ₂=0.5, therefore in step (C), concrete thermal expansivity is directly predicted and is obtained by following formula,

${\mathrm{\α}}_c=0.5({\mathrm{\α}}_{\mathrm{cp}}{f}_{\mathrm{cp}}+{\mathrm{\α}}_s{f}_s+{\mathrm{\α}}_g{f}_g)+0.5\·\frac{{\mathrm{\α}}_{\mathrm{cp}}{f}_{\mathrm{cp}}{K}_{\mathrm{cp}}+{\mathrm{\α}}_s{f}_s{K}_s+{\mathrm{\α}}_g{f}_g{K}_g}{f_{\mathrm{cp}}{K}_{\mathrm{cp}}+f_s{K}_s+f_g{K}_g}.---\left(5\right)$

This concrete thermal expansion coefficient prediction model has considered the bulk modulus of the bulk modulus of the bulk modulus of the thermal expansivity of the thermal expansivity of the thermal expansivity of cement paste, sand, stone, cement paste, sand, stone, volume fraction, the volume fraction of sand and the impact of the volume fraction of stone on thermal expansion coefficient of concrete of cement paste in concrete, and consider interaction and the impact of deformation characteristics on thermal expansion coefficient of concrete between cement paste and sand, stone in conjunction with actual conditions, more fit in practical situations.

In order to verify prediction effect of the present invention, carry out following verification experimental verification:

Test adopts home-made contrivance to carry out.Sample dimensions is 100mm × 100mm × 500mm, rapidly test specimen is moved into standard curing is indoor carries out maintenance after building, and measures thermal expansivity when maintenance to 28 day.Cement adopts Portland cement, and sand adopts river sand, and stone adopts grouan, and quality mixture ratio (water: cement: sand: stone) is 0.48:1:1.37:2.54, and the density of each component is got conventional numerical value, is respectively 1000kg/m ³(water), 3150kg/m ³(cement), 1400kg/m ³(sand), 2640kg/m ³(stone), volume fraction converts and obtains according to the ratio of quality and density.Cement paste, river sand, grouan and concrete thermal expansivity all record by test, are respectively 14.6 × 10 ^-6/ DEG C, 7.5 × 10 ^-6/ DEG C, 6.2 × 10 ^-6/ DEG C, 9.07 × 10 ^-6/ DEG C; The springform of cement paste measures 20Gpa, and the elastic modulus of sand, stone is all got 35Gpa, and Poisson ratio all gets 0.25, and bulk modulus obtains according to elastic modulus E and Poisson ratio ν conversion: K=E/3 (1-2 ν).

Concrete thermal expansivity forecasting process is as shown in table 1:

The concrete thermal expansivity reckoner of table 1

From analyzing above, between predicted value and measured value, there is the good goodness of fit, illustrate that institute of the present invention established model can be preferably for predicting concrete thermal expansivity.

More than show and described ultimate principle of the present invention, principal character and advantage.The technician of the industry should understand; the present invention is not restricted to the described embodiments; that in above-described embodiment and instructions, describes just illustrates principle of the present invention; without departing from the spirit and scope of the present invention; the present invention also has various changes and modifications, and these changes and improvements all fall in the claimed scope of the invention.The claimed scope of the present invention is defined by appending claims and equivalent thereof.

Claims (3)

1. a construction method for thermal expansion coefficient of concrete forecast model, is characterized in that: comprises the following steps,

Step (A), set up the mixed-mode of thermal expansion coefficient of concrete:

When concrete temperature variation, ignore the interaction between cement paste and sand, stone, respectively equal independent deformation mutually, calculates concrete thermal expansivity according to mixed-mode,

α _c1＝α _cpf _cp+α _sf _s+α _gf _g (1)

In formula (1), α _c1for the concrete thermal expansivity calculating by mixed-mode, α _cp, α _s, α _gbe respectively the thermal expansivity of cement paste, sand and stone, f _cp, f _sand f _gbe respectively cement paste, sand and stone shared volume fraction in concrete;

Step (B), set up the Turner model of thermal expansion coefficient of concrete:

When concrete temperature variation, cement paste and sand, stone bear uniform hydrostatic stress and are homogeneous deformation, calculate concrete thermal expansivity according to Turner model,

In formula (2), α _c2for the concrete thermal expansivity calculating by Turner model, K _cp, K _sand K _gbe respectively the bulk modulus of cement paste, sand and stone;

Step (C), set up the forecast model of thermal expansion coefficient of concrete:

In reality, between concrete component material cement paste and sand, stone, exist and interact, and distortion is constraint mutually, between step (A), (B) described two kinds of situations, taking two kinds of models described in step (A), (B) as basis, set up the forecast model of thermal expansion coefficient of concrete, as follows

α _c＝λ ₁α _c1+λ ₂α _c2 (3)

In formula (3) and formula (4), α _cfor the concrete thermal expansivity that prediction obtains, λ ₁, λ ₂for combination coefficient, and λ ₁+ λ ₂=1, λ ₁and λ ₂represent respectively press thermal expansion coefficient of concrete that mixed-mode and Turner model the calculate percentage contribution to thermal expansion coefficient of concrete under the actual conditions of predicting.

2. the construction method of a kind of thermal expansion coefficient of concrete forecast model according to claim 1, is characterized in that: concrete is the three-phase composite material of cement paste, sand, stone composition.

3. the construction method of a kind of thermal expansion coefficient of concrete forecast model according to claim 1, is characterized in that: in step (C), exist and interact and distortion constraint mutually between cement paste and sand, stone, combination coefficient is got respectively λ ₁=λ ₂=0.5, concrete thermal expansivity obtains by the direct prediction of following formula,

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