Method and system for prediction of concrete maturity

Abstract

A method for predicting the maturity of a concrete during the curing process is disclosed. The method comprises the following steps: predicting at least one future temperature within the concrete; performing at least one temperature measurement, preferably a real-time temperature measurement of the concrete; transmitting the at least one temperature measurement wirelessly from at least one temperature sensor to an external device; and determining the energy production within the concrete.

Claims

1. A method for predicting a maturity of a concrete during an early-stage curing process, characterized in that the method comprises the following steps: predicting at least one future temperature within the concrete by using information about a relationship between temperature and energy production in the concrete, wherein said prediction is carried out after: performing at least one real-time temperature measurement of the concrete; transmitting the at least one real-time temperature measurement wirelessly from at least one temperature sensor to an external device, wherein said least one temperature sensor is used for performing the at least one real-time temperature measurement of the concrete; and by using the external device determining energy production (ΔQ.sub.n) within the concrete, wherein the step of determining the energy production within the concrete is carried out by applying information about the real-time temperature of the concrete; wherein in the step of predicting at least one future temperature within the concrete, the temperature used for the prediction is carried out on the basis of a measured temperature being the real-time temperature measurement, and wherein the step of performing at least one real-time temperature measurement of the concrete is carried out on a continuous basis.

2. A method according to claim 1, characterized in that the step of transmitting the at least one temperature measurement comprises transmitting the at least one temperature measurement to the external device comprising a server via the internet.

3. A method according to claim 1, characterized in that environmental parameters are saved to form historical data, wherein at least some of the historical data are used for predicting at least one future temperature within the concrete.

4. A method according to claim 3, characterized in that the environmental parameters include at least one of (a) one or more environmental temperatures, (b) one or more air circulation measurements, and (c) one or more humidity measurements.

5. A system for predicting a maturity of a concrete during an early-stage curing process, characterized in that the system comprises: a predicting unit configured to predict at least one future temperature within the concrete; at least one temperature sensor configured to perform real time temperature measurements of the concrete; and an energy production estimator configured to estimate energy production (ΔQ.sub.n) within the concrete, wherein the at least one temperature sensor is arranged and configured to transmit at least one temperature measurement wirelessly to an external device and wherein the predicting unit is configured to apply a) the real time temperature measurements of the concrete made by the at least one temperature sensor and b) the estimated energy production (ΔQ.sub.n) within the concrete estimated by the energy production estimator to predict the at least one future temperature, wherein the system is configured to carry out at least one real-time temperature measurement of the concrete on a continuous basis.

6. A system according to claim 5, characterized in that the system comprises: one or more environmental parameter determination units configured to determine one or more environmental parameters influencing the temperature of the concrete.

7. A system according to claim 5, characterized in that the system is configured to store one or more environmental parameters to form historical data, wherein at least some of the historical data are used for predicting at least one future temperature within the concrete.

8. A system according to claim 5, characterized in that the at least one temperature sensor is configured to transmit the temperature measurements to the external device comprising a server via the internet.

Description

DESCRIPTION OF THE DRAWINGS

(1) The invention will become more fully understood from the detailed description given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative of the present invention. In the accompanying drawings:

(2) FIG. 1A shows a schematic view of the setting time of concrete constructions produced on six production lines;

(3) FIG. 1B shows a cross-sectional view of a concrete construction being made by means of a casting frame in a production facility, in which the concrete emits heat to air above the concrete;

(4) FIG. 1C shows a cross-sectional view of the concrete construction shown in FIG. 1B, in a situation, in which the concrete receives heat from the air above the concrete;

(5) FIG. 2A shows a graph depicting measurement values from a calorimetric test, in which temperature is shown as function of time;

(6) FIG. 2B shows a curve for a standard curing process and an accelerated curing process;

(7) FIG. 3A shows an example of, how the method according to the invention can be used to adjust the environmental influence to predict the temperature development and hereafter the maturity and corresponding strength of the concrete;

(8) FIG. 3B shows another example of, how the method according to the invention can be used to adjust the environmental influence to predict the temperature development and hereafter the maturity and corresponding strength of the concrete;

(9) FIG. 4 shows a flowchart illustrating the steps carried out to predict the maturity of concrete according to one embodiment of the method of the invention;

(10) FIG. 5 shows an example of, how the method according to the invention can be used to adjust the environmental influence to predict the temperature development and hereafter the maturity and corresponding strength of the concrete;

(11) FIG. 6A shows a cross-sectional view of a casting frame and two mounting devices according to the invention each attached to a rod, and

(12) FIG. 6B shows the casting frame shown in FIG. 6A while concrete has been poured into the casting frame.

(13) FIG. 7A shows a graph of the relationship between setting of cement, reaction time and temperature,

(14) FIG. 7B shows a graph illustrating the relationship between the duration of the setting and the concrete temperature.

DETAILED DESCRIPTION OF THE INVENTION

(15) Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, FIG. 1A illustrates a schematic view of the curing time T.sub.c (setting time) of concrete constructions produced on six production lines L.sub.1, L.sub.2, L.sub.3, L.sub.4, L.sub.5, L.sub.6 arranged in a production facility to produce the same construction.

(16) The curing time TC of the production lines L.sub.1, L.sub.2, L.sub.3, L.sub.4, L.sub.5, L.sub.6 is indicated by boxes filled with dots. The estimated (safe) curing time E is indicated on the curing time axis. It can be seen, that the curing time of the first production line L.sub.1 is shorter than the estimated (safe) curing time E. Accordingly, there is a “capacity available” CA.sub.i. This means that the construction process of the first production line L.sub.1 could have been terminated and a new production process could have been initiated. Accordingly, time could have been saved.

(17) The curing time of the second production line L.sub.2 is even shorter than the curing time of the first production line L.sub.1 and therefore also shorter than the estimated curing time E. Therefore, there is a “capacity available” CA.sub.2 and the construction process of the production line L.sub.2 may have been terminated in order to initiate a new production process.

(18) The curing time of the third production line L.sub.3 is longer than the estimated curing time E. Therefore, a construction process is actually terminated before the construction has received the required maturity and strength. Accordingly, the construction cannot be used and will therefore be waste.

(19) The curing time of the fourth production line L.sub.4 is shorter than the curing time of the first production lines L.sub.1 and L.sub.2 as well as the estimated curing time E. Thus, there is a “capacity available” CA.sub.3 and the construction process of the production line L.sub.4 could have been terminated in order to use the production line L.sub.4 and initiate a new production process.

(20) The curing time of the fifth production line L.sub.5 corresponds to the estimated curing time E.

(21) The curing time of the sixth production line L.sub.6 is shorter than the estimated curing time E. Accordingly, there is a “capacity available” CA.sub.4 and the construction process of the production line L.sub.6 may have been terminated in order to initiate a new production process.

(22) FIG. 1A illustrates that even when constructing the same construction, environmental influences makes it very difficult to estimate the curing time. Even though an additional safety-time is added to the estimated curing time E errors occur. Furthermore, a lot of time is wasted.

(23) FIG. 1B illustrates a cross-sectional view of a concrete construction being made by means of a casting frame 38 in a production facility, in which the concrete 36 emits heat 8 to the surrounding air above the foil 28 covering the top side of the concrete 36. The casting frame 38 is part of a support unit 4 shaped as a table with legs and an integrated heating unit 24 comprising electrical heating wires supplied with power from an electrical connection (socket) 12 connected to a power supply by means of an electric plug 14. Alternatively, heating tubes may be arranged and configured to circulate a heating fluid (e.g. water) inside the casting frame 38.

(24) The heating unit 24 generates heat 6 that is transferred to the concrete 36 in order to initiate or speed op the curing process. A system 50 according to the invention is applied to monitor the concrete construction process on a continuous basis. The system 50 comprises two sensors 26, 26′ arranged to monitor the temperature inside the concrete 36. Each sensor 26, 26′ measures the temperature of the concrete 36. The first sensor 26′ measures the temperature of the concrete 36 by means of a cable 20 comprising a thermocouple embedded in the concrete 36. The other sensor 26 is embedded in the concrete and measures the temperature of the concrete 36 and sends a wireless signal to a receiving unit. The cable 20 and the sensor 26 are attached to an elongated body (a rebar) 10 embedded in the concrete 36.

(25) The system 50 comprises a humidity sensor 16 arranged to measure the humidity of the surrounding air. The system 50 also comprises an airflow (velocity) sensor 22 arranged and configured to measure the flow of the circulating air 18 surrounding the top portion of the concrete 36.

(26) The sensors 16, 22, 26, 26′ are arranged and configured to transmit the collected data wirelessly to an external device such as a server 44 via the Internet 42. The sensors 16, 22, 26, 26′ may be configured to communicate directly with an external device such as a smartphone 46. The smartphone 46 may communicate wirelessly with the Internet 42 and/or an Internet-based server 44.

(27) FIG. 1C illustrates a cross-sectional view of the concrete construction shown in FIG. 1B, in a situation, which the concrete 36 receives heat 9 from the air above the concrete 36.

(28) FIG. 2A illustrates a graph depicting measurement values from a calorimetric test (e.g. a Quasi-adiabatic test), in which temperature 34 is shown as function of time 32.

(29) A Quasi-adiabatic test makes it possible to estimate the heat being released due to the hydration of cement contained in the concrete specimen. The test incorporates all possible interactions between concrete components, including the effects of admixtures.

(30) The calorimeter used for carrying out the test is typically a double-walled caisson filled with an insulating material (e.g. polyurethane foam). The external wall may be made of polyvinyl chloride (PVC) and the internal wall may be of fiberglass-reinforced polyester.

(31) The test is conducted on the concrete compound in order to be able to perform temperature predictions using the test results. The test determines the produced energy from the exotherm process in the concrete as a function of the maturity in the concrete. The test may be conducted in accordance with standards such as the “NT BUILD 388” standard or the “DS 423.37” e.g. a Quasi-adiabatic calorimetry test.

(32) The method according to the invention applies the information about, how energy development in the concrete occurs as function of time and the method applies real-time measurements in the concrete as well as the environment. This information makes it possible to isolate the environmental factor from the structures surrounding the concrete and assess the influence this will have on the future development (curing process).

(33) The duration Δt.sub.1 of the first time interval (t.sub.1 to t.sub.2) equals the duration Δt.sub.2 of the second time interval (t.sub.2 to t.sub.3) and the duration Δt.sub.3 of the third time interval (t.sub.3 to t.sub.4). The time intervals Δt.sub.1, Δt.sub.2, Δt.sub.3 may e.g. be 60-1200 seconds, such as 120-900 seconds, preferably 300-900 seconds such as 450-800 second. In one test scenario, the time intervals Δt.sub.1, Δt.sub.2, Δt.sub.3 are 600 seconds.

Example 1

(34) In one example, the following values may be recorded:

(35) Δt.sub.1, Δt.sub.2, Δt.sub.3=600 seconds;

(36) ΔE.sub.1=320 Joule, ΔE.sub.2=540 Joule, ΔE.sub.3=920 Joule;

(37) θ.sub.1=25° C., θ.sub.2=27° C., θ.sub.3=30° C., θ.sub.4=38° C.;

(38) The quasi-adiabatic test identifies the amount of generated energy within the concrete in a 100% isolated environment. This reveals the relationship between the energy development and maturity of the concrete in a 100% isolated environment.

(39) FIG. 2B illustrates a curve 56 for a standard curing process as well as a curve 54 for an accelerated curing process, in which the strength 52 is plotted as function of time 32. The curing process is typically considered to be accomplished after 28 days. The initial inclination of the curve 56 for the standard curing process is lower than the initial inclination of the curve 54 for the accelerated curing process. Accordingly, application of the accelerated curing process enables a much faster removal of construction produced e.g. in a production concrete panel factory.

(40) FIG. 3A illustrates a graph depicting measurement values during a concrete curing process, in which temperature 34 is shown as function of time 32. Four first measurement points B.sub.1, B.sub.2, B.sub.3, B.sub.4 are plotted in the graph. The theoretical point (calculated assuming 100% insulation) A.sub.1 is plotted next to these points. A fifth measurement point B.sub.5 is plotted in the graph below the theoretical point A.sub.1. The difference between the fifth measurement point B.sub.5 and the theoretical point A.sub.1 is caused by environmental influence X. When using the method according to the invention, temperature measurements of the concrete are carried out (preferably in real-time). Accordingly, it is possible to calculate the maturity of the concrete and match that with the energy development in the concrete. This enables determination of the amount of energy developed in the concrete, which energy can be correlated with the actual temperature development.

(41) FIG. 3B illustrates an example of, how the method according to the invention can be used to adjust the environmental influence to predict the temperature development and hereafter the maturity and corresponding strength of the concrete. The graph comprises the same points as the graph shown in FIG. 3A, however a projected point Z.sub.1 is added. The projected point Z.sub.1 is estimated by using the method according to the invention applying the steps shown in the flowchart shown in FIG. 4. It can be seen, that the projected point Z.sub.1 is below the theoretical point A.sub.2 (assuming 100% insulation). The difference between the projected point Z.sub.1 and the theoretical point A.sub.2 is caused by environmental influence X. The environmental temperature C is shown in FIG. 3B.

(42) In one embodiment according to the invention, the method comprises the step of collecting environmental influence data. Hereby, it is possible to apply the data to improve the prediction precession of the method.

(43) In one embodiment according to the invention, the temperature of a support unit (e.g. a table) can be measured and collected (and preferably stored in a data storage). This temperature influences the curing process and may therefore be used to perform optimized future predictions.

(44) In one embodiment according to the invention, the humidity of the surrounding air is measured and stored in a data storage. The specific heat capacity of humid air is greater than dry air and humid air will take more energy to heat by a given amount. Accordingly, the humidity of the surrounding air influences the curing process and may therefore be used to perform optimized future predictions.

(45) In one embodiment according to the invention, the velocity of an airflow adjacent to the concrete and/or the frame, into which the concrete is poured, is measured and stored in a data storage. The velocity of an airflow adjacent to the concrete and/or the frame influences the curing process. Accordingly, the velocity of an airflow adjacent to the concrete and/or the frame may therefore be used to perform optimized future predictions.

(46) In a preferred embodiment according to the invention, the temperature C of the surroundings is measured and stored in a data storage on a continuous basis. The temperature of the surroundings influences the curing process and therefore, it may be advantageous to apply the temperature of the surroundings to perform optimized future predictions.

(47) FIG. 4 illustrates a flowchart illustrating the steps carried out to predict the maturity of concrete according to one embodiment of the method of the invention. Step I is a step of calculating the maturity of the concrete. Step I is carried out on the basis of an estimated temperature (carried out in Step four IV). Initially, when no temperature is estimated (in Step four IV), measured temperature values are applied. The temperatures are preferably measured by means of temperature sensors embedded in the concrete.

(48) Step II represents the step of projecting the internal energy generated inside the concrete. This can be applied by using the previously mentioned equation (6):

(49) $\begin{array}{cc}\begin{array}{c}\Delta Q_n=\Delta Q_{\mathrm{acc},n}+\Delta Q_{\mathrm{trans},n}\\ =\left({\theta }_{n+1}-{\theta }_n\right).Math.C_c.Math.\frac{{\rho }_c}{C}+\\ \left[\frac{a_t.Math.{\rho }_c}{m_c.Math.C}.Math.\frac{f_{c,n}+f_{c,n+1}}{2}.Math.\Delta t_n\right]\end{array}& \left(6\right)\end{array}$

(50) Step III represents the step of applying environmental influencing factors. This step may include applying information about the temperature of a support unit (e.g. a table), the humidity of the surrounding, the velocity of an airflow adjacent to the concrete and/or the frame, the temperature of the surroundings.

(51) Step IV represents the step of estimating concrete temperature. This is effected by using historic data collected, preferably in the production facility and even better in the actual production line within the production facility.

(52) Performing an analysis on the historical data enables the method according to the invention to take into account the influences (e.g. the temperature of a support unit (e.g. a table) and/or the humidity of the surrounding and/or the velocity of an airflow adjacent to the concrete and/or the frame and/or the temperature of the surroundings) of the environment in which the concrete is manufactured. Accordingly, the historical data can be used to improve the prediction of the future temperature development.

(53) The process for estimating the next data point is illustrated by the flowchart: The current maturity is calculated in Step I, the energy development is determined in Step II, the environment is accounted in Step III. Step III makes it possible to derive at the next temperature point in Step IV.

(54) The process steps illustrated in FIG. 4 can now be repeated. Hereby, it is possible to estimate the remaining temperature development as illustrated in FIG. 5.

(55) Each repetition may factor in the new maturity and the corresponding energy development in the concrete. The environmental influence is adjusted according to surrounding parameters such as temperature, humidity and air circulation.

(56) FIG. 5 illustrates an example of, how the method according to the invention can be used to adjust the environmental influence to predict the temperature development and hereafter the maturity and corresponding strength of the concrete.

(57) The graph depicts concrete temperature as function of time. The first portion of the graph corresponds to the graph shown in FIG. 3B. Further points have been added. These points are: A.sub.3, A.sub.4, A.sub.5, A.sub.6, A.sub.7, Z.sub.2, Z.sub.3, Z.sub.4, Z.sub.5 and Z.sub.6 corresponding to the “remaining” curing period.

(58) Once the temperature development is predicted, the maturity of the concrete is predicted by using the steps shown in FIG. 4. The corresponding strength of the concrete can also be determined. In this manner, the method according to the invention, enables one to derive at the estimated time of completion for an element.

(59) In a preferred embodiment according to the invention, for each new data point measured by sensors, a recalculate the entire method is carried out to improve accuracy and improve the data model for estimating the environmental influence.

(60) FIG. 6A illustrates a cross-sectional view of a casting frame 38 and two mounting devices 2 configured to be used to attach thermocouples to rebar 10. FIG. 6B illustrates the casting frame 38 shown in FIG. 6A while concrete 36 has been poured into the casting frame 38. Concrete 36 is poured into the casting frame 38 by means of a concrete nozzle 40.

(61) The sensors 26 may be configured to communicate wirelessly with an external device such as a server 44 via the Internet 42. The sensors 26 may be configured to communicate directly wirelessly with an external device such as a smartphone 46. The smartphone 46 may communicate wirelessly with the Internet 42 and/or an Internet-based server 44.

(62) In one embodiment according to the invention, the sensor 26′ may be integrated in the mounting device 2 or detachably attached to the mounting device 2. Hereby, the server 26′ may be attached to a rebar 10 by means of a mounting device 2′ according to the invention. In such a solution, wireless communication may be provided between the sensor 26′ and an external device such as a server 44 via the Internet 42. The sensors 26′ may also be configured to communicate directly and wirelessly with an external device such a smartphone 46.

(63) The rebar 10 is part of a rebar cage (steel mesh). Each mounting device 2 is attached to a cable 20 that is plugged into a sensor 26. The sensors 26 may be configured to perform real-time temperature and maturity monitoring of the concrete 36. The temperature may be detected by means of a cable 20 comprising a thermocouple having two dissimilar conductors forming electrical junctions at differing temperatures which are capable of producing a temperature-dependent voltage.

LIST OF REFERENCE NUMERALS

(64) 2, 2′ Mounting device 4 Support unit (table with integrated heating unit) 6 Heat from the support unit 8 Heat from the concrete to the surrounding 9 Heat from the surroundings to the concrete 10 Elongated body 12 Electrical connection (socket) 14 Electric plug 16 Humidity sensor 18 Circulating air 20 Cable 22 Airflow sensor 24 Heating unit 26, 26′ Sensor 28 Foil 30 Missing curing time 32 Time 34 Temperature 36 Concrete 38 Frame 40 Concrete nozzle 42 Internet 44 Server 46 External device 50 System 52 Strength 54, 56 Curve X Longitudinal axis T.sub.c Curing time E Prior art estimated curing time CA.sub.1, CA.sub.2, CA.sub.3, CA.sub.4 Capacity available L.sub.1, L.sub.2, L.sub.3, L.sub.4, L.sub.5, L.sub.6 Production line θ.sub.n, θ.sub.n+1, θ.sub.1, θ.sub.2, θ.sub.3, θ.sub.4 Concrete temperature ΔQ.sub.acc,n Change of accumulated energy in the concrete ΔQ.sub.trans,n Change of transmitted energy from the concrete C Content of cement ρ.sub.c Density of concrete C.sub.c Specific heat of the concrete f.sub.c,n, f.sub.c,n+1 Output from box wall transducer m.sub.c Weight of the concrete sample a.sub.t Calibration factor Q Heat development Δt.sub.n, Δt.sub.1, Δt.sub.2, Δt.sub.3 Time interval (t.sub.n+1-t.sub.n) B.sub.1, B.sub.2, B.sub.3, B.sub.4, B.sub.5 Measurement point A.sub.1, A.sub.2, A.sub.3, A.sub.4 Theoretical point (100% insulation) A.sub.5, A.sub.6, A.sub.7 Theoretical point (100% insulation) Z.sub.1, Z.sub.2, Z.sub.3, Z.sub.4, Z.sub.5, Z.sub.6 Projected point X Environmental influence I Calculation of maturity II Projection of internal energy III Applying environmental influencing factors IV Estimating concrete temperature