Intelligent crack control and prevention system for concrete

Abstract

The invention discloses a concrete intelligent crack control and prevention system, and the system comprises a temperature monitoring device which comprises a plurality of temperature sensors disposed in and on the surface of a concrete structure, and a data collection device which is used for collecting the temperature data monitored by the temperature sensors; the curing device is a heating curing device and is arranged on the periphery of the concrete structure; the control device is connected with the data acquisition device and the curing device and used for receiving the temperature data of the interior and the surface of the concrete structure, calculating the tensile strength and the surface tensile stress of the concrete and controlling the curing device to adjust the curing temperature according to the relation between the tensile strength and the surface tensile stress of the concrete. The curing device can be intelligently controlled in the early stage of concrete pouring, specific, economical and reasonable curing measures are provided, concrete cracking is prevented, meanwhile, energy consumption of concrete curing is reduced, and excessive curing is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete pouring construction, and more specifically, to an intelligent concrete crack control and prevention system. Background Art

[0002] The cement in concrete releases heat during the hydration reaction with water, and the hydration reaction leads to the formation of cement colloid gel, which is a key step in the hardening of concrete. The heat released during the hardening process is unevenly distributed in the volume of concrete. Usually, the temperature of the concrete surface is relatively low due to the cooling effect of the external environment, while the temperature inside the concrete is relatively high due to the heat released by the hydration reaction. Due to the uneven distribution of heat, the interior and surface of the concrete produce different degrees of volume expansion and contraction. The volume change caused by contraction will produce tensile stress on the surface of the concrete. When these stresses exceed the tensile strength of the concrete, temperature cracks will occur. In the prior art, after collecting the internal surface temperature of the concrete structure at the initial stage of pouring, it is generally used to warn of concrete cracking. No specific and economically reasonable maintenance adjustment measures can be given. There is still a risk of over-maintenance, resulting in energy waste. Summary of the invention

[0003] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0004] In order to achieve these purposes and other advantages according to the present invention, a concrete intelligent crack control and prevention system is provided, comprising:

[0005] A temperature monitoring device, comprising a plurality of temperature sensors respectively arranged inside and on the surface of the concrete structure, and a data acquisition device for acquiring temperature data monitored by each of the temperature sensors;

[0006] The curing device is a heating curing device and is arranged on the periphery of the concrete structure;

[0007] A control device is connected to the data acquisition device and the curing device, and is used to receive temperature data inside and on the surface of the concrete structure, calculate the tensile strength and surface tensile stress of the concrete, and control the curing device to adjust the curing temperature according to the relationship between the tensile strength and the surface tensile stress of the concrete.

[0008] Preferably, the maintenance device includes an electric heating film covering the periphery of the concrete structure and a polyurethane plate arranged above the electric heating film.

[0009] Preferably, the process of the control device controlling the curing device to adjust the curing temperature according to the relationship between the tensile strength of concrete and the surface tensile stress specifically includes:

[0010] When k1σs ≥f t When determining whether the tensile strength of concrete and the surface tensile stress are in the same order of magnitude, if they are in the same order of magnitude, the curing device is controlled to increase the curing temperature by ΔT1; if they are not in the same order of magnitude, the curing device is controlled to increase the curing temperature by ΔT2, ΔT2=nΔT1;

[0011] When k1σ s ≤f t ≤k2σ s When the maintenance device is adjusted, there is no need to adjust the maintenance device;

[0012] When f t ≥k2σ s When determining whether the tensile strength of concrete and the surface tensile stress are in the same order of magnitude, if they are in the same order of magnitude, controlling the curing device to reduce the curing temperature by ΔT1, and if they are not in the same order of magnitude, controlling the curing device to reduce the curing temperature by ΔT2;

[0013] Among them, f t is the tensile strength of concrete, σ s is the tensile stress on the concrete surface, k1 is the temperature-controlled anti-cracking safety factor for limiting cracks at level III, k2 is the temperature-controlled anti-cracking safety factor for limiting cracks at level II, n is the order of magnitude of the difference between the tensile strength of concrete and the surface tensile stress, and ΔT1 is an empirical value.

[0014] Preferably, when f t ≥k2σ s When the lowered curing temperature is lower than the natural curing temperature, the curing device is closed.

[0015] Preferably, the concrete tensile strength is calculated by the following formula:

[0016]

[0017] M=Σ(T+15)×Δt

[0018] In the above formula, a and b are fitting coefficients, M is the maturity of concrete curing, and T is the average temperature of concrete in the time period Δt.

[0019] Preferably, the concrete surface tensile stress is calculated by the following formula:

[0020]

[0021] M=Σ(T+15)×Δt

[0022] In the above formula, σ s(t) is the tensile stress of the concrete surface at age t, α is the linear expansion coefficient of concrete, E(t) is the elastic modulus of concrete at age t, a, b, are fitting coefficients, M is the maturity of concrete curing, T is the average temperature of concrete in the time period Δt, ΔT ab (t) is the temperature difference between the inner and outer surfaces of concrete at age t; K P Stress relaxation coefficient caused by concrete creep.

[0023] Preferably, the data acquisition device collects data once every hour.

[0024] The present invention has at least the following beneficial effects:

[0025] The intelligent concrete crack control and prevention system provided by the present invention monitors the internal surface temperature of the concrete structure and calculates the tensile strength and surface tensile stress of the concrete, and then controls the curing device to adjust the curing temperature according to the relationship between the tensile strength and the surface tensile stress of the concrete. The curing device is intelligently controlled in the early stage of concrete pouring, and specific and economically reasonable curing measures are provided to prevent concrete cracking, while reducing the energy consumption of concrete curing and avoiding excessive curing.

[0026] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the concrete tensile strength-maturity fitting curve of Examples 1 to 3 of the present invention;

[0028] Figure 2 is the concrete elastic modulus-maturity fitting curve of Examples 1 to 3 of the present invention;

[0029] Figure 3 This is a graph of temperature changes after curing using the intelligent concrete crack control and prevention system according to Example 1 of the present invention;

[0030] Figure 4 This is a graph of concrete tensile strength and surface tensile stress after the intelligent concrete crack control and crack prevention system is used in Example 1 of the present invention;

[0031] Figure 5 This is a graph of temperature changes after curing using the intelligent concrete crack control and prevention system according to Example 2 of the present invention;

[0032] Figure 6 This is a graph of concrete tensile strength and surface tensile stress after the intelligent concrete crack control and crack prevention system is used in Example 2 of the present invention;

[0033] Figure 7This is a graph of temperature changes after curing using the intelligent concrete crack control and prevention system according to Example 3 of the present invention;

[0034] Figure 8 This is a graph of concrete tensile strength and surface tensile stress after the intelligent concrete crack control and crack prevention system is used in Example 3 of the present invention;

[0035] Fig. 9 This is a schematic diagram of the cracking risk area of ​​Comparative Example 4 of the present invention;

[0036] Fig.10 This is a schematic diagram of the cracking risk area of ​​Comparative Example 5 of the present invention;

[0037] Fig.11 This is a schematic diagram of the cracking risk area of ​​Comparative Example 6 of the present invention;

[0038] Fig.12 The tensile strength of concrete and 1.2 times the surface tensile stress of comparative examples 7 to 9 of the present invention are shown in FIG. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0040] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0041] like Figures 1 to 12 As shown, the present invention provides a concrete intelligent crack control and crack prevention system, comprising:

[0042] A temperature monitoring device, comprising a plurality of temperature sensors respectively arranged inside and on the surface of the concrete structure, and a data acquisition device for acquiring temperature data monitored by each of the temperature sensors;

[0043] The curing device is a heating curing device and is arranged on the periphery of the concrete structure;

[0044] A control device is connected to the data acquisition device and the curing device, and is used to receive temperature data inside and on the surface of the concrete structure, calculate the tensile strength and surface tensile stress of the concrete, and control the curing device to adjust the curing temperature according to the relationship between the tensile strength and the surface tensile stress of the concrete.

[0045] In this technical solution, the plurality of temperature sensors include a deeply buried temperature sensor disposed inside the concrete structure and a surface mounted temperature sensor disposed on the surface of the concrete structure, the deeply buried temperature sensor is used to monitor the internal temperature of the concrete, and the surface mounted temperature sensor is used to monitor the surface temperature of the concrete. The data acquisition device is used to collect and record the internal surface temperature data of the concrete, generally once every hour.

[0046] Specifically, the curing device includes an electric heating film covering the outer periphery of the concrete structure and a polyurethane plate arranged above the electric heating film. The curing system adopts a heating curing method, and the control system adjusts the curing temperature by controlling the heating temperature of the electric heating film.

[0047] The process of the control device controlling the curing device to adjust the curing temperature according to the relationship between the tensile strength of concrete and the surface tensile stress specifically includes:

[0048] When k1σ s ≥f t When determining whether the tensile strength of concrete and the surface tensile stress are in the same order of magnitude, if they are in the same order of magnitude, the curing device is controlled to increase the curing temperature by ΔT1; if they are not in the same order of magnitude, the curing device is controlled to increase the curing temperature by ΔT2, ΔT2=nΔT1;

[0049] When k1σ s ≤f t ≤k2σ s When the maintenance device is adjusted, there is no need to adjust the maintenance device;

[0050] When f t ≥k2σ s When determining whether the tensile strength of concrete and the surface tensile stress are in the same order of magnitude, if they are in the same order of magnitude, controlling the curing device to reduce the curing temperature by ΔT1, and if they are not in the same order of magnitude, controlling the curing device to reduce the curing temperature by ΔT2;

[0051] Among them, f t is the tensile strength of concrete; s is the tensile stress on the concrete surface; k1 is the temperature-controlled anti-cracking safety factor for limiting cracks at level III, which can be taken as 1.2; k2 is the temperature-controlled anti-cracking safety factor for limiting cracks at level II, which can be taken as 1.4; n is the order of magnitude of the difference between the tensile strength of concrete and the surface tensile stress; ΔT1 is an empirical value, which can be taken as 0.5℃.

[0052] Furthermore, when f t ≥k2σ s When the lowered curing temperature is lower than the natural curing temperature, the curing device is closed.

[0053] According to the data collection frequency of the data collection device, the concrete tensile strength and surface tensile stress are recalculated regularly based on the real-time data of the internal and external temperature difference, and the relationship between the concrete tensile strength and the surface tensile stress is judged again. The curing temperature is adjusted according to the above process until the purpose of preventing concrete cracking and green energy saving is achieved, thereby effectively solving the problem of easy cracking in the early stage of pouring.

[0054] Specifically, the concrete tensile strength is calculated by the following formula:

[0055]

[0056] M=Σ(T+15)×Δt (2)

[0057] In formula (1) and formula (2), a and b are fitting coefficients, M is the concrete curing maturity, and T is the average temperature of concrete in the time period Δt.

[0058] The concrete surface tensile stress is specifically calculated by the following formula:

[0059]

[0060] M=∑(T+15)×Δt (5)

[0061] In formula (3) to formula (5), σ s (t) is the tensile stress of the concrete surface at age t, α is the linear expansion coefficient of concrete, E(t) is the elastic modulus of concrete at age t, a, b, are fitting coefficients, M is the maturity of concrete curing, T is the average temperature of concrete in the time period Δt, ΔT ab (t) is the temperature difference between the inner and outer surfaces of concrete at age t; K P Stress relaxation coefficient caused by concrete creep.

[0062] The fitting coefficients a, b, a1, and b1 are obtained by fitting the known temperature data and the corresponding concrete elastic modulus and concrete tensile strength.

[0063] The following is a further explanation of the intelligent crack control and crack prevention system for concrete according to the present invention through specific examples. Examples 1 to 3 use ordinary silicate cement and commercially available fly ash and sandstone, and the mix ratios are shown in Table 1. The tensile strength and elastic modulus of the obtained concrete structure are shown in Table 2. The tensile strength and elastic modulus of the concrete are obtained by fitting the maturity model according to formula (1) and formula (4), respectively. The fitting curves of the two are shown as follows: Figure 1 and Figure 2 shown.

[0064] Table 1 Concrete mix ratio of Examples 1 to 3

[0065] Strength level cement Mineral powder Fly ash Xiaoshi Dashi sand water Water reducing agent Example 1 C30 112.8 206.8 56.4 342 798 60 200 3.6 Example 2 C40 301 34 63 302 706 92 65 6 Example 3 C50 245 171.5 73.5 327.3 763.7 27 47 7

[0066] Table 2 Concrete tensile strength and elastic modulus of Examples 1 to 3

[0067]

[0068] Examples 1 to 3 use the intelligent concrete crack control and crack prevention system of the present invention for maintenance. Figure 3 to Figure 8 It can be seen that the intelligent concrete crack control and crack prevention system can timely and appropriately adjust the curing temperature to meet the requirement that the tensile strength of the concrete is greater than 1.2 times the surface tensile stress, and there is no risk of cracking of the concrete, while effectively reducing energy loss.

[0069] Comparative Examples 4 to 6 have the same concrete mix ratio, raw materials and preparation methods as Examples 1 to 3, except that Comparative Examples 4 to 6 are naturally cured at 20°C, and the risk of cracking is Figures 9-11 .Depend on Figures 9-11 It can be seen that if concrete is naturally cured at 20° without special curing, there is a risk of cracking before 76 hours.

[0070] Comparative Examples 7 to 9 have the same concrete mix ratio, raw materials and preparation methods as Examples 1 to 3, respectively. The difference is that in Comparative Examples 7 to 9, heating and heat preservation are first performed at 60° for 72 hours, and then naturally cured at 20°. The tensile strength of concrete and 1.2 times the surface tensile stress are shown in the figure below: Fig.12 The energy consumption comparison of Comparative Examples 7 to 9 and Examples 1 to 3 in the first 72 hours is shown in Table 3. Fig.12 It can be seen that although there is no risk of concrete cracking in comparative examples 7 to 9 in the first 72 hours, the traditional heating and thermal insulation curing cannot adjust the curing temperature in time, and the energy consumption is significantly higher than the energy consumed by the intelligent concrete crack control and crack prevention system of the present invention.

[0071] Table 3 Energy consumed by intelligent crack control and crack prevention system and traditional heating and insulation maintenance in the first 72 hours

[0072] Serial number Intelligent crack control and prevention system Traditional heating and thermal insulation maintenance Save energy Example 1 / Comparative Example 7 3820(T*h) 4320(T*h) 500(T*h) Example 2 / Comparative Example 8 2740(T*h) 4320(T*h) 1580(T*h) Example 3 / Comparative Example 9 1625(T*h) 4320(T*h) 2695(T*h)

[0073] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A concrete intelligent crack control and crack prevention system, characterized in that: include: A temperature monitoring device, comprising a plurality of temperature sensors respectively arranged inside and on the surface of the concrete structure, and a data acquisition device for acquiring temperature data monitored by each of the temperature sensors; The curing device is a heating curing device and is arranged on the periphery of the concrete structure; A control device is connected to the data acquisition device and the curing device, and is used to receive temperature data inside and on the surface of the concrete structure, calculate the tensile strength and surface tensile stress of the concrete, and control the curing device to adjust the curing temperature according to the relationship between the tensile strength and the surface tensile stress of the concrete.

2. The intelligent concrete crack control and prevention system according to claim 1, characterized in that: The maintenance device comprises an electric heating film covering the outer periphery of the concrete structure and a polyurethane plate arranged above the electric heating film.

3. The intelligent concrete crack control and prevention system according to claim 1, characterized in that: The process of the control device controlling the curing device to adjust the curing temperature according to the relationship between the tensile strength of concrete and the surface tensile stress specifically includes: When k1σ s ≥f t When determining whether the tensile strength of concrete and the surface tensile stress are in the same order of magnitude, if they are in the same order of magnitude, the curing device is controlled to increase the curing temperature by ΔT1; if they are not in the same order of magnitude, the curing device is controlled to increase the curing temperature by ΔT2, ΔT2=nΔT1; When k1σ s ≤f t ≤k2σ s When the maintenance device is adjusted, there is no need to adjust the maintenance device; When f t ≥k2σ s When determining whether the tensile strength of concrete and the surface tensile stress are in the same order of magnitude, if they are in the same order of magnitude, controlling the curing device to reduce the curing temperature by ΔT1, and if they are not in the same order of magnitude, controlling the curing device to reduce the curing temperature by ΔT2; Among them, f t is the tensile strength of concrete, σ s is the tensile stress on the concrete surface, k1 is the temperature-controlled anti-cracking safety factor for limiting cracks at level III, k2 is the temperature-controlled anti-cracking safety factor for limiting cracks at level II, n is the order of magnitude of the difference between the tensile strength of concrete and the surface tensile stress, and ΔT1 is an empirical value.

4. The intelligent concrete crack control and prevention system according to claim 3, characterized in that: When f t ≥k2σ s When the lowered curing temperature is lower than the natural curing temperature, the curing device is closed.

5. The intelligent concrete crack control and prevention system according to claim 3, characterized in that: The concrete tensile strength is specifically calculated by the following formula: M=Σ(T+15)×Δt In the above formula, a and b are fitting coefficients, M is the concrete curing maturity, and T is the concrete curing temperature within the time period Δt.

6. The intelligent concrete crack control and prevention system according to claim 3, characterized in that: The concrete surface tensile stress is specifically calculated by the following formula: M=Σ(T+15)×Δt In the above formula, σ s (t) is the tensile stress of the concrete surface at age t, α is the linear expansion coefficient of concrete, E(t) is the elastic modulus of concrete at age t, a, b, are fitting coefficients, M is the concrete curing maturity, T is the concrete curing temperature in the time period Δt, ΔT ab (t) is the temperature difference between the inner and outer surfaces of concrete at age t; K P Stress relaxation coefficient caused by concrete creep.

7. The intelligent concrete crack control and prevention system according to claim 1, characterized in that: The data acquisition device collects data once every hour.

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