CN103926271A - Method for inverting adiabatic temperature rise of concrete - Google Patents

Abstract

A method for obtaining adiabatic temperature rise of concrete relates to method for measuring and acquiring temperature by the use of temperature sensors and a temperature acquisition module and inverting adiabatic temperature rise by measured temperature calculation. By arranging temperature sensors along the radial direction at different positions on the same section of concrete, temperatures of concrete at different measuring points and at different times are measured; a temperature field is calculated through difference; and inversion of adiabatic temperature rise is optimized by the utilization of measured temperature and calculated temperature. Instead of getting down to reducing heat radiation of concrete, temperature of concrete during the process of heat radiation is measured to invert adiabatic temperature rise. Through data analysis, it proves that a later exothermic process of concrete can be well reflected.

Description

A kind of method of inverting Adiabatic temperature rise of concrete

Technical field

The present invention relates to a kind of method of obtaining Adiabatic temperature rise of concrete, particularly obtain the adiabatic temperature rise in concrete heat release later stage.

Background technology

The temperature that adiabatic temperature rise is related in dam construction is controlled, and is an important performance of mass concrete.Generally only carry out at present the 28d adiabatic temperature rise test in the length of time, the thermal-insulating chamber of instrument will reach thermal insulative test condition, and the hydration heat of Binder Materials is not dispersed into external environment.Test specimen surface is exposed, and thermal-insulating chamber temperature will be followed the tracks of concrete sample central temperature, is more or less the same in ± 0.1 ℃.Along with the growth in the length of time, the accumulation of heat loss that the two temperature gap causes becomes large thereupon, thereby is difficult to warranty test precision.

On this test method basis, improve, formed a kind of new test method, at concrete sample coated outside heat-insulation layer, other steps are still undertaken by test method before, owing to there being heat-insulation layer, reduced equivalent coefficient of heat transfer, even if heat accumulating losses are slightly larger, also much smaller on the impact of concrete temperature rise.Heat-insulation layer coefficient of heat conductivity is less, and thickness is thicker, and test accuracy is higher.Although the method has reduced error to a certain extent, cannot stop concrete heat radiation completely, when longer in the length of time, can not reflect well later concrete exothermic process, test accuracy is still not high.

Summary of the invention

A kind of method that the object of this invention is to provide inverting Adiabatic temperature rise of concrete, by measuring the concrete temperature retrieval adiabatic temperature rise in heat radiation process, make it can obtain more accurately adiabatic temperature rise, and the exothermic process of energy reflected well later concrete, engineering reality more met.

The object of the invention is to be achieved through the following technical solutions:

A method for inverting Adiabatic temperature rise of concrete, is characterized in that the method comprises the steps:

1) first make drum type brake hollow mould, in hollow mould bottom, lay one layer of heat preservation material [2], be used for simulating radially one dimension heat radiation, in mould surrounding, lay respectively insulation material simultaneously, thickness is 1/3rd to 1/5th of bottom insulation material, is used for slowing down rate of heat dispation;

2), when casting concrete is to hollow mould intermediate altitude, in mould, radially arrange and fix a plurality of temperature sensors [3];

3) continue casting concrete, vibrated concrete, after having vibrated, the insulation material in the laying of mould top with bottom same thickness, puts into fog room maintenance immediately;

4) temperature signal of serviceability temperature acquisition module temperature sensor in set time Δ τ gathers concrete;

5) utilize difference method accounting temperature field, concrete in mould is divided into a plurality of thin annulus layers, the annulus center of circle is the mould center of circle, every layer thickness is made as h, examination is radially same and i-1 that adjacent distance between two points is h in taking out adjacent three layers, i, and 3 of i+1 analyze, 3 to distance of center circle from increasing successively, by heat-conduction equation and radially one dimension heat radiation obtain following formula:

$T_{i,\mathrm{\τ}+\mathrm{\Δ\τ}}=(1-2b)T_{i,\mathrm{\τ}}+(b-\frac{\mathrm{bh}}{2r})T_{i-1,\mathrm{\τ}}+(b+\frac{\mathrm{bh}}{2r})T_{i+1,\mathrm{\τ}}+\mathrm{\Δ\θ}---\left(1\right)$

b=aΔτ/h ² （2）

In formula, T _{i, τ}be that i point is at the temperature of time τ, T _{i, τ+Δ τ}be i point in the temperature of time τ+Δ τ, r be i point to distance of center circle from, h is thickness in monolayer, Δ τ is time step, a is thermal diffusivity, Δ θ be from τ to τ+thermal insulation temperature rise in the Δ τ time period, b is intermediate variable;

6) by (1) formula, obtained, i point, the temperature of time τ+Δ τ can be by time τ, i-1, i, 3 temperature of i+1 represent, wherein comprise two parameters, Δ θ and b, b≤1/2 o'clock (1) formula result of calculation is stable;

7) establishing temperature sensor point for measuring temperature quantity is n, n point is all radially same, point 1～n is to distance of center circle from increasing successively, and 2 temperature of 1, n are boundary condition, according to (1) formula, the temperature of being ordered by initial time 1～n and time Δ τ, the temperature that 1, n is 2, obtain time Δ τ, the accounting temperature T that 2～n-1 is ordered ₂～T _n-1, establish time Δ τ, the observed temperature that 2～n-1 is ordered is t ₂～t _n-1, be optimized to calculate and obtain Δ θ and b makes (3) formula minimum:

$\underset{i=2}{\overset{n-1}{\mathrm{\Σ}}}{(T_i-t_i)}^2---\left(3\right)$

Repeating step 7), by time Δ τ, 1～n each point temperature and times 2 Δ τ, 1, the temperature that n is 2 is calculated to obtain times 2 Δ τ, and the accounting temperature that 2～n-1 is ordered, with observed temperature comparison, be optimized and calculate Δ θ and the b that obtains this period, by that analogy, calculate the temperature rise of each period.

The present invention compared with prior art, has the following advantages and high-lighting effect: 1. due to the aggregated loss heat not having in classic method, this method can reflect the exothermic process of later concrete better.2. the formula that this method is used is short and sweet, is convenient to work out relative program and calculates.3. classic method is higher at heat release later stage concrete temperature, does not meet engineering reality.And this method can make test specimen temperature be consistent with concrete temperature variation in engineering by the method for the temperature that controls environment, resulting like this thermal insulation temperature rise more meets engineering reality.

Accompanying drawing explanation

Fig. 1 is drum type brake hollow mould longitudinal diagram.

Fig. 2 is drum type brake hollow mould drawing in side sectional elevation.

Fig. 3 is some temperature computation schematic diagram in drum type brake hollow mould.

Wherein: 1-concrete; 2-insulation material; 3-temperature sensor is respectively from left to right wherein 1～No. 7 temperature sensor in Fig. 2.

Embodiment

Below in conjunction with accompanying drawing, further illustrate embodiments of the present invention:

The present invention is by radially laying the temperature sensor of diverse location at concrete same profile, measure the concrete temperature of different time different measuring points, by difference method accounting temperature field, utilize the minimum Optimization inversion adiabatic temperature rise of the poor quadratic sum of observed temperature and accounting temperature again.Concrete mode can be implemented as follows:

1) first make drum type brake hollow mould, carrying and form removal are detachably convenient in both sides, box out both sides in intermediate altitude place, in hollow mould bottom, lay one layer of heat preservation material [2], be used for simulating radially one dimension heat radiation, lay respectively insulation material in mould surrounding, thickness is 1/3rd to 1/5th of bottom insulation material simultaneously, be used for slowing down rate of heat dispation, as shown in Figure 1;

2) when casting concrete is to hollow mould intermediate altitude, ready rectangular plastic tablet is put into mould by mould both sides aperture, on rectangular plastic tablet, press predeterminable range and lay aperture, orifice size is identical with sensor temperature measuring head, temperature sensor [3] is inserted in the reserved hole of rectangular pieces and radially according to certain intervals, fixed with assurance sensing station, and sensor is laid mode as shown in Figure 2;

3) continue casting concrete, vibrated concrete, after having vibrated, the insulation material in the laying of mould top with bottom same thickness, puts into fog room maintenance immediately;

4) temperature signal of serviceability temperature acquisition module temperature sensor in set time Δ τ gathers concrete;

5) difference method accounting temperature field, the heat-conduction equation of cylindrical coordinates form is:

$\frac{\∂T}{\∂\mathrm{\τ}}=a(\frac{{\∂}^{2}T}{{\∂r}^2}+\frac{1}{r}\frac{\∂T}{\∂r}+\frac{1}{r^2}\frac{{\∂}^{2}T}{{\∂\mathrm{\φ}}^2}+\frac{{\∂}^{2}T}{{\∂z}^2})+\frac{\∂\mathrm{\θ}}{\∂\mathrm{\τ}}$

In formula, T is temperature, and a is thermal diffusivity, and θ is adiabatic temperature rise, and τ is the time, and r is for radially, and z is that axially φ is angle direction.

Due to the radially one dimension heat radiation of this test simulation, so can suppose that z, φ direction do not conduct heat, above formula can be reduced to:

$\frac{\∂T}{\∂\mathrm{\τ}}=a(\frac{{\∂}^{2}T}{{\∂r}^2}+\frac{1}{r}\frac{\∂T}{\∂r})+\frac{\∂\mathrm{\θ}}{\∂\mathrm{\τ}}$

Concrete in mould is divided into a plurality of thin annulus layers, and the annulus center of circle is the mould center of circle, and every layer thickness is made as h, examination is radially same and i-1 that adjacent distance between two points is h in taking out adjacent three layers, i, and 3 of i+1 analyze, 3 are arrived distance of center circle from increasing successively, as shown in Figure 3.

According to differential principle, ignore truncation error, each stage partial derivative of temperature can be expressed as follows:

${\left(\frac{\∂T}{\∂r}\right)}_{i,\mathrm{\τ}}=\frac{1}{2h}(T_{i+1,\mathrm{\τ}}-T_{i-1,\mathrm{\τ}})$

${\left(\frac{\∂T}{\∂r}\right)}_{i+h/2,\mathrm{\τ}}=\frac{1}{h}(T_{i+1,\mathrm{\τ}}-T_{i,\mathrm{\τ}})$

${\left(\frac{\∂T}{\∂r}\right)}_{i-h/2,\mathrm{\τ}}=\frac{1}{h}(T_{i,\mathrm{\τ}}-T_{i-1,\mathrm{\τ}})$

$\begin{array}{c}{\left(\frac{{\∂}^{2}T}{{\∂r}^2}\right)}_{i,\mathrm{\τ}}=\frac{1}{h}[{\left(\frac{\∂T}{\∂r}\right)}_{i+h/2,\mathrm{\τ}}-{\left(\frac{\∂T}{\∂r}\right)}_{i-h/2,\mathrm{\τ}}]\\ =\frac{1}{h^2}(T_{i-1,\mathrm{\τ}}+T_{i+1,\mathrm{\τ}}-2T_{i,\mathrm{\τ}})\end{array}$

With forward difference, calculate and

${\left(\frac{\∂T}{\∂r}\right)}_{i,\mathrm{\τ}}=\frac{1}{\mathrm{\Δ\τ}}(T_{i+1,\mathrm{\τ}}-T_{i,\mathrm{\τ}})$

${\left(\frac{\∂\mathrm{\θ}}{\∂\mathrm{\τ}}\right)}_{i,\mathrm{\τ}}=\frac{\mathrm{\θ}(\mathrm{\τ}+\mathrm{\Δ\τ})-\mathrm{\θ}\left(\mathrm{\τ}\right)}{\mathrm{\Δ\τ}}=\frac{\mathrm{\Δ\θ}}{\mathrm{\Δ\τ}}$

In above various generation,, in cylindrical coordinates One-dimensional Heat Conduction Equation, is obtained:

$T_{i,\mathrm{\τ}+\mathrm{\Δ\τ}}=(1-2b)T_{i,\mathrm{\τ}}+(b-\frac{\mathrm{bh}}{2r})T_{i-1,\mathrm{\τ}}+(b+\frac{\mathrm{bh}}{2r})T_{i+1,\mathrm{\τ}}+\mathrm{\Δ\θ}$

b=aΔτ/h ²

In formula, T _{i, τ}be that i point is at the temperature of time τ, T _{i, τ+Δ τ}be i point in the temperature of time τ+Δ τ, r be i point to distance of center circle from, h is thickness in monolayer, Δ τ is time step, a is thermal diffusivity, Δ θ be from τ to τ+thermal insulation temperature rise in the Δ τ time period, b is intermediate variable;

6) by above formula, obtained, i point, the temperature of time τ+Δ τ can be by time τ, i-1, i, 3 temperature of i+1 represent, wherein comprise two parameters, Δ θ and b, b≤1/2 o'clock above formula result of calculation is stable;

7) establishing sensor point for measuring temperature quantity is n, n point is all radially same, point 1～n is to distance of center circle from increasing successively, and 2 temperature of 1, n are boundary condition, according to above formula, the temperature of being ordered by initial time 1～n and time Δ τ, the temperature that 1, n is 2, obtain time Δ τ, the accounting temperature T that 2～n-1 is ordered ₂～T _n-1, establish time Δ τ, the observed temperature that 2～n-1 is ordered is t ₂～t _n-1, be optimized to calculate and obtain Δ θ and b makes following formula minimum:

$\underset{i=2}{\overset{n-1}{\mathrm{\Σ}}}{(T_i-t_i)}^2$

Repeating step 7), by time Δ τ, 1～n each point temperature and times 2 Δ τ, 1, the temperature that n is 2 is calculated to obtain times 2 Δ τ, and the accounting temperature that 2～n-1 is ordered, with observed temperature comparison, be optimized and calculate Δ θ and the b that obtains this period, by that analogy, calculate the temperature rise of each period.

Embodiment:

In concrete enforcement, right cylinder interior diameter 400mm, high 600mm.Insulation material adopts rubber-plastic sponge, and the insulation material of 80mm is laid in top and the bottom, and surrounding is laid respectively the insulation material of 20mm.On intermediate altitude section, lay altogether seven temperature sensors, one of them is in the center of circle, radially arranges, transducer spacing is 50mm, as shown in Figure 2.Within every 5 minutes, read temperature one time, getting time step Δ τ is 5min, and every layer thickness h is 50mm.

Seven measuring positions are divided into two groups, and every group of measuring point, all radially same, is respectively No. 1234 Sensors and No. 7654 Sensors shown in Fig. 2.The initial measured value of getting every group is starting condition, and first group of 1, No. 4 measurement value sensor is boundary condition, and second group of 7, No. 4 sensor is boundary condition.

First by initial value, calculate the temperature value after 5 minutes, and make comparisons with observed temperature value, be optimized and calculate the obtain thermal diffusivity adiabatic temperature rise of period therewith, make each calculating location, be i.e. the quadratic sum minimum of 2,3,5, No. 6 sensing station accounting temperatures and the difference of observed temperature.By the temperature value after 5 minutes, calculate the temperature value after 10 minutes again, with the comparison of observed temperature value, be optimized and calculate thermal diffusivity and the adiabatic temperature rise of obtaining this period.By that analogy, calculate the adiabatic temperature rise of each period, draw adiabatic temperature rise curve.

Carry out subsequently the classic method of same match ratio concrete heat isolation room temperature tracking concrete sample central temperature and carry out adiabatic temperature rise test, draw adiabatic temperature rise curve, and compare with calculating adiabatic temperature rise curve before.Relatively draw, in the initial exotherm stage, both are more approaching, growth along with the length of time, the former tends towards stability, and the latter is still keeping given pace to rise, both gaps widen gradually, thereby can prove that this method can embody the later concrete exothermic process that classic method cannot embody.

Claims (1)

1. a method for inverting Adiabatic temperature rise of concrete, is characterized in that the method comprises the steps:

1) first make drum type brake hollow mould, in hollow mould bottom, lay one layer of heat preservation material [2], be used for simulating radially one dimension heat radiation, in mould surrounding, lay respectively insulation material simultaneously, thickness is 1/3rd to 1/5th of bottom insulation material, is used for slowing down rate of heat dispation;

2), when casting concrete is to hollow mould intermediate altitude, in mould, radially arrange and fix a plurality of temperature sensors [3];

3) continue casting concrete, vibrated concrete, after having vibrated, the insulation material in the laying of mould top with bottom same thickness, puts into fog room maintenance immediately;

4) temperature signal of serviceability temperature acquisition module temperature sensor in set time Δ τ gathers concrete;

5) utilize difference method accounting temperature field, concrete in mould is divided into a plurality of thin annulus layers, the annulus center of circle is the mould center of circle, every layer thickness is made as h, examination is radially same and i-1 that adjacent distance between two points is h in taking out adjacent three layers, i, and 3 of i+1 analyze, 3 to distance of center circle from increasing successively, by heat-conduction equation and radially one dimension heat radiation obtain following formula:

b＝aΔτ/h ² (2)

In formula, T _{i, τ}be that i point is at the temperature of time τ, T _{i, τ+Δ τ}be i point in the temperature of time τ+Δ τ, r be i point to distance of center circle from, h is thickness in monolayer, Δ τ is time step, a is thermal diffusivity, Δ θ be from τ to τ+thermal insulation temperature rise in the Δ τ time period, b is intermediate variable;

6) by (1) formula, obtained, i point, the temperature of time τ+Δ τ can be by time τ, i-1, i, 3 temperature of i+1 represent, wherein comprise two parameters, Δ θ and b, b≤1/2 o'clock (1) formula result of calculation is stable;

7) establishing temperature sensor point for measuring temperature quantity is n, n point is all radially same, point 1～n is to distance of center circle from increasing successively, and 2 temperature of 1, n are boundary condition, according to (1) formula, the temperature of being ordered by initial time 1～n and time Δ τ, the temperature that 1, n is 2, obtain time Δ τ, the accounting temperature T that 2～n-1 is ordered ₂～T _n-1, establish time Δ τ, the observed temperature that 2～n-1 is ordered is t ₂～t _n-1, be optimized to calculate and obtain Δ θ and b makes (3) formula minimum:

Repeating step 7), by time Δ τ, 1～n each point temperature and times 2 Δ τ, 1, the temperature that n is 2 is calculated to obtain times 2 Δ τ, and the accounting temperature that 2～n-1 is ordered, with observed temperature comparison, be optimized and calculate Δ θ and the b that obtains this period, by that analogy, calculate the temperature rise of each period.