Concrete monitoring system and method

Abstract

The invention discloses a concrete monitoring system and a concrete monitoring method. The concrete monitoring system comprises at least one piezoelectric aggregate which can be embedded into a concrete structure; and a controller. The controller is configured to: perform a plurality of frequency scans on the at least one piezoelectric aggregate to obtain a plurality of phase angles; and determining a state of the concrete structure based on a phase angle change between several phase angles of the plurality of phase angles.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of priority to Singapore Patent Application No. 10202251418X, filed on October 18, 2022, the content of which is hereby incorporated by reference in its entirety for all purposes. Technical field

[0003] This application relates to a concrete monitoring system and a concrete monitoring method. Background art

[0004] Concrete is a mixture of cement (cement paste), water, and fine / coarse aggregates. During the forming or manufacturing process of fresh concrete, the cement reacts with water through a process called hydration. During the hydration process, the concrete gradually hardens over time. Concrete finishing is a post - forming process used to produce a smooth and durable surface on the formed concrete structure. Since concrete finishing must start before the concrete structure has fully hardened, determining the start time of concrete finishing plays an important role in the final surface finish. Improper finishing can result in low - strength, defective concrete slabs with poor appearance. Therefore, construction workers closely monitor the state of the concrete when determining the appropriate time for concrete finishing. However, existing methods such as Bar Dropping tests typically lack precision and often have an adverse impact on the integrity of the concrete structure. Summary of the invention

[0005] According to one aspect, a concrete monitoring system is provided herein. The concrete monitoring system includes at least one piezoelectric aggregate that can be embedded in a concrete structure; and a controller. The controller is configured to: perform a plurality of frequency scans on the at least one piezoelectric aggregate to obtain a plurality of phase angles; and determine the state of the concrete structure based on a change in phase angle between some of the plurality of phase angles.

[0006] According to another aspect, a concrete monitoring method is disclosed herein. The concrete monitoring method includes: performing a plurality of frequency scans on at least one piezoelectric base aggregate embedded in a concrete structure to obtain a plurality of phase angles; and determining the state of the concrete structure based on a change in phase angle between some of the plurality of phase angles. Brief description of the drawings

[0007] The different embodiments of this application are described below with reference to the following drawings:

[0008] Figure 1 is a schematic diagram of a concrete monitoring system according to an embodiment of this application;

[0009] Figure 2 is a flowchart of a concrete monitoring method according to an embodiment;

[0010] Figure 3 is an example output obtained from multiple impedance measurements of a single piezoelectric aggregate;

[0011] Figure 4 is Figure 3 a detailed view of;

[0012] Figure 5 is a diagram showing the change of peak phase frequency over time;

[0013] Figure 6 is a diagram showing the change of peak phase amplitude over time;

[0014] Figure 7 is a perspective view of a piezoelectric aggregate according to an embodiment of the present application;

[0015] Figure 8 is Figure 7 an exploded view of;

[0016] Figure 9 is Figure 8 a sectional view of;

[0017] Figure 10 is a schematic diagram of a piezoelectric structure according to an embodiment of the present application, the piezoelectric structure including a circular piezoelectric cylinder and a concrete cylinder;

[0018] Figure 11 is Figure 10 a lumped parameter schematic diagram of the piezoelectric structure shown;

[0019] Figures 12A to 12D is for manufacturing Figure 7 a perspective view of the mold 400 for the piezoelectric aggregate shown;

[0020] Figures 13A to 13C is showing the use of Figure 12D an image of the method for manufacturing intelligent aggregates using the mold shown;

[0021] Figure 14 is a schematic diagram of a concrete measurement system according to an embodiment of the present application;

[0022] Figure 15 is a schematic diagram of a first wireless solution of a concrete measurement system according to an embodiment of the present application;

[0023] Figure 16 is a schematic diagram of a second wireless solution of a concrete measurement system according to an embodiment of the present application;

[0024] Figure 17Shows a schematic working flowchart of a concrete monitoring system according to different embodiments of the present application;

[0025] Figure 18 Is a flowchart showing an algorithm for automatically processing data;

[0026] Figure 19 Shows the correlation between the peak phase frequency and the penetration depth;

[0027] Figure 20 Shows the correlation between the peak phase amplitude and the penetration depth. Detailed Description of Specific Embodiments

[0028] The following detailed description is made with reference to the accompanying drawings, which show the details and embodiments of the present application for illustrative purposes. Features described in the context of one embodiment can be correspondingly applied to the same or similar features in other embodiments, even if not explicitly described in these other embodiments. The application and / or combination and / or substitution described for features in the context of one embodiment can be correspondingly applied to the same or similar features in other embodiments.

[0029] In the context of different embodiments, the articles "a", "an", and "the" used with respect to features or elements include references to one or more features or elements.

[0030] In the context of different embodiments, the term "about" or "approximately" applied to a numerical value encompasses the exact value and a reasonable difference commonly understood in the relevant technical field, such as within 10% of the specified value.

[0031] As used herein, the term "and / or" includes any combination and all combinations of one or more of the listed related items.

[0032] For the sake of brevity, the term "phase angle" can be used to represent any one or more of the terms "peak phase angle", "phase angle curve", "phase angle diagram", "phase angle data point", "maximum phase angle", "peak in the phase angle diagram", "peak in the phase angle curve", "measured phase angle", "phase angle database", etc., as will be understood from the context.

[0033] As used herein, the term "aggregate" refers to gravel, sand, crushed rock, and / or different inert materials applied to concrete other than cement and water. Conventional aggregates can be in a refined specific size or in a coarser particle form. Aggregates are applied to a mixture of cement (such as ordinary Portland cement) and water and ultimately form part of a hardened concrete structure, and it is known that aggregates affect the properties of freshly mixed (not yet fully hardened) concrete as well as the properties of fully hardened concrete.

[0034] For the sake of brevity, the term "freshly mixed concrete" will refer to the mixture before the mixture containing cement and water is fully hardened. The term "concrete" will substantially refer to a mixture or structure containing cement and water, including fully hardened concrete, but not limited thereto.

[0035] The term "condition" as used in relation to a concrete structure will substantially refer to one or more properties of the concrete structure that can be evaluated, measured, calculated, estimated, or otherwise determined, and the term "condition" as used in relation to a concrete structure can be described based on one property or a combination of multiple qualitatively and / or quantitatively determined properties of the concrete structure. Quantitatively determined properties include, but are not limited to: water content; porosity; brittleness; mechanical properties such as elasticity, strength, fracture toughness, etc.; electrical properties such as electrical resistance, conductivity, impedance, admittance, dielectric properties, etc.; thermal properties such as coefficient of thermal expansion, thermal conductivity, etc.; acoustic properties such as acoustic impedance, stiffness coefficient, etc.

[0036] For the purpose of aiding understanding and without limitation, different embodiments of the concrete monitoring system 100 and the concrete monitoring method 200 will be described below with reference to the accompanying drawings. The concrete monitoring system 100 and the concrete monitoring method 200 can also be described as systems and methods that can monitor and measure the condition of a newly formed concrete structure or a freshly mixed concrete structure. For the sake of brevity, different examples related to the concrete monitoring system and method will be described below, but it will be understood that the system 100 and the method 200 can be used in multiple application scenarios related to concrete structure monitoring and are not limited to the specific examples disclosed herein.

[0037] Figure 1 is a schematic diagram of a concrete monitoring system 100 for monitoring a concrete structure 80 according to different embodiments of the present application. As Figure 1As shown, the concrete monitoring system 100 may include one or more sensor devices (hereinafter each referred to as "smart aggregate") 110. The piezoelectric aggregate 110 may also be referred to as an Electromechanical Impedance Measurement-based Smart Aggregate (EIM-SMA). Different numbers of smart aggregates 110 may be distributed and embedded in different parts of the concrete structure 90. In some embodiments where the concrete structure 80 is relatively small, one smart aggregate 110 may be sufficient to monitor the entire concrete structure 80. In the example shown, three smart aggregates 110 are embedded in the concrete structure 80 at approximately the same depth and spaced apart from each other. In other examples, multiple smart aggregates 110 may be embedded at different depths from the same surface of the concrete structure 80. In some examples, each of the multiple smart aggregates 110 may be used to determine the state of a local volume or a local region of the concrete structure 80.

[0038] Multiple smart aggregates 110 may be jointly used to determine the state of a relatively large volume of concrete. In some examples, data collected by the controller 120 from the distribution of multiple smart aggregates 110 may be used to display different parts of the concrete structure in their respective states. The use of smart aggregates 110 allows for the selection of one or more target regions / volumes for monitoring. For example, to monitor the state of the concrete structure 80 closer to the surface, the smart aggregate may be embedded near the surface of the concrete structure 80. Alternatively, to monitor the state deep below the surface of the concrete structure 80, the smart aggregate 110 may be embedded deeper in the concrete structure 80.

[0039] In some embodiments, the concrete monitoring system 100 may further include a controller 120. During operation, the controller 120 is in signal communication with one or more smart aggregates 110. In some examples, as Figure 1 shown, the controller 120 may be in signal communication with one or more smart aggregates 110 through one or more wired connections. In other embodiments, the controller may be in signal communication with the smart aggregates 110 through a wireless connection.

[0040] The controller 120 can be set to execute a concrete monitoring method. The controller 120 is set to execute instructions stored in a computer-readable memory and perform a method for determining the state of the concrete structure 80. In some embodiments, the controller 120 can send signals to or receive signals from each of the smart aggregates 110, and based on the signals, process and / or calculate an output corresponding to the state of the concrete structure 80. In some embodiments, the concrete monitoring system 100 includes one or more transmitters 130 that are set to enable signal communication between one or more of the smart aggregates 110 and the controller 120. In some embodiments, the controller 120 can be coupled to a display 121. The controller 120 can be set to convey the state of the concrete structure 80 to a user, such as via the display 121, thereby displaying an output corresponding to the state of the concrete structure 80 to the user or a worker.

[0041] In some embodiments, the controller 120 can include an impedance analyzer for processing signals emitted from each of the smart aggregates 110. The impedance analyzer measures the impedance of the smart aggregate within a frequency range. In some embodiments, the controller 120 can include a driver for driving each of the smart aggregates 110. For example, the driver can be a piezoelectric driver or a piezoelectric drive circuit to drive the piezoelectric aggregate.

[0042] During use, such as when the cement mixture is freshly poured, the smart aggregates 110 can be placed or embedded in the fresh concrete. Each of the plurality of smart aggregates 110 can be embedded in the concrete structure 80 during the forming / fabrication process of the concrete structure. In other words, when the concrete structure 80 is still in a relatively fluid / wet state and has not hardened, the smart aggregates 110 are placed or set inside the concrete structure 80. After embedding the smart aggregates 110 in the fresh concrete structure 80, monitoring of the state of the concrete structure 80 can begin.

[0043] On the one hand, the concrete monitoring method includes continuously or intermittently obtaining signals from the smart aggregates 110 over a period of time during which a fresh concrete structure (in which the smart aggregates 110 are provided) matures or changes from an initial state towards a fully hardened state (mature). In some applications, the controller 120 is set to determine for a user a recommended time or time period for performing a finishing operation on the concrete structure 80. In some embodiments, the state of the concrete structure 80 can be related to the hydration state for the purpose of concrete finishing. Since concrete finishing must start before the concrete structure is fully hardened, determining the hydration state of the concrete structure can affect the final surface finish. Therefore, the method can be iteratively performed during the hardening or maturation process of the concrete in the concrete structure 80 to determine the state of the concrete structure.

[0044] Figure 2 A process flow diagram showing a concrete monitoring method 200 according to different embodiments of the present application. The method 200 may include, in stage 210, performing a plurality of frequency scans on one or more smart aggregates 110, such as piezoelectric aggregates. In some embodiments, the smart aggregate 110 may be calibrated first before performing the frequency scans. In some embodiments, performing each of the plurality of frequency scans may include driving each of the plurality of piezoelectric aggregates 110 within a frequency range and obtaining a corresponding electrical signal from each of the plurality of piezoelectric aggregates 110 within the same frequency range. The electrical signal obtained from each of the plurality of piezoelectric aggregates 110 may correspond to an impedance measurement of the corresponding piezoelectric aggregate 110 within the frequency range. In some embodiments, performing each of the plurality of frequency scans may include measuring the impedance of the corresponding piezoelectric aggregate 110 within a frequency range. In some embodiments, each of the measured impedances may include a corresponding magnitude of the impedance and a corresponding phase angle of the impedance. For some embodiments, a plurality of phase angles are obtained when performing a plurality of frequency scans on one or more piezoelectric aggregates 110. To avoid ambiguity, the phase angle of each impedance may be a continuous measurement, a discrete measurement, a discrete measurement value, a plurality of segments of a continuous measurement, a plurality of segments of a discrete measurement, a plurality of discrete measurement values, etc.

[0045] Thus, each frequency scan may result in a measurement or signal obtained from the corresponding piezoelectric aggregate. In some embodiments, a plurality of frequency scans may be performed over a period of time. A single frequency scan performed on a single aggregate at one moment may produce a unique signal. Thus, a plurality of frequency scans performed on a single aggregate over a period of time may produce a plurality of unique signals. Additionally, a single frequency scan performed on a plurality of aggregates at one moment may also produce a plurality of unique signals.

[0046] In some embodiments, the plurality of frequency scans may be performed iteratively based on a measurement cycle rate. For example, the measurement cycle rate may be described as performing one frequency scan for each piezoelectric aggregate every 30 minutes or every 10 minutes. In some embodiments, there may be a plurality of embedded piezoelectric aggregates. The frequency scans may be performed in an overlapping manner such that only a single frequency scan is performed at each moment. This ensures weaker interference occurs between the plurality of piezoelectric aggregates during their respective frequency scans.

[0047] Alternatively, the plurality of frequency scans may be performed in an orderly manner based on a measurement schedule. For example, a preset schedule may be provided first to perform frequency scans according to a schedule such as 10 minutes, 30 minutes, 80 minutes, 150 minutes, etc. after the piezoelectric aggregate is embedded.

[0048] In some examples, refer to Figure 3, each impedance measurement may include a phase angle plot within a frequency range, for example, between 30 kHz and 100 kHz. In other examples, the frequency range may be between 50 kHz and 80 kHz. The frequency range may be determined based on system settings, aggregate components, or the grade mix of the concrete. In Figure 3 , multiple impedance measurement results obtained from corresponding multiple frequency scans are shown. It can be seen that in each impedance measurement, the phase angle plot may show a peak phase angle or a peak phase amplitude. The peak phase angle or the peak phase amplitude may correspond to a peak phase frequency. As an example, referring to Figure 4 , the peak phase amplitude (p n ) corresponds to the peak phase frequency (f n ). Since the phase angle of a typical impedance measurement is bounded within a range of -90 degrees to +90 degrees, it is relatively convenient to locate the peak phase angle in a frequency scan because there may be only a single peak. Therefore, the drift or change of the peak phase angle can be easily observed. Compared with observing the peak impedance amplitude (the amplitude of the impedance) that may exhibit several local peaks, this is beneficial for achieving the localization of the peak phase angle for determining the state of the concrete structure.

[0049] In some embodiments, the impedance measurement results may be received and output as one or more discrete values, such as the peak phase amplitude, the peak phase frequency, or a combination of both. In other embodiments, the impedance measurement results may be received and output as a list corresponding to one or both of the peak phase amplitude and the peak phase frequency.

[0050] In some embodiments, method 200 may further include, at stage 220, determining the state of the concrete structure based on the phase angle change between selected phase angles among multiple phase angles. The phase angles are obtained from previously performed frequency scans. In other words, the state of the concrete structure may be determined based on the change in the phase angle of the piezoelectric aggregate when performing multiple frequency scans. In some embodiments, the state of the concrete structure is determined based on the phase angle change between selected multiple phase angles obtained from the same piezoelectric aggregate. In some embodiments, method 200 includes determining the state of the concrete structure during the maturation process of the concrete structure. In some embodiments, to obtain the corresponding phase angle change, each piezoelectric aggregate is monitored and observed individually. In other words, the signals emitted from each piezoelectric aggregate are independently collected and analyzed. Therefore, for this scenario, the state of the concrete structure determined from one piezoelectric aggregate may correspond to the "local" state of the concrete structure or to a local region of the concrete structure. In embodiments with multiple piezoelectric aggregates, each "local" state of the concrete structure may be used to jointly determine the "overall" state of the concrete structure.

[0051] In some embodiments, method 200 may further include, at stage 230, determining a target state of the concrete structure based on a phase angle change between selected phase angles among a plurality of phase angles. In some embodiments, a preset threshold or condition for the phase angle change may be set to determine the target state of the concrete structure. In some embodiments, the target state of the concrete structure may be a state suitable for a post-forming process such as concrete finishing. Thus, the target state may include a finishable state of the concrete structure, in which the concrete structure is suitable for concrete surface finishing.

[0052] Referring Figure 4 and Figure 5 , in some embodiments, the change in the phase angle corresponds to a drift of the peak phase frequency between each of the phase angles obtained from a frequency scan. The peak phase frequency corresponds to the frequency at which the phase angle diagram / curve presents a peak, for example, at f1 or f n . For example, the change in the phase angle (Δf) corresponds to a drift of the peak phase frequency from f1 to f n , or in other cases, from f n to f n+1 . It can be understood that the drift of the peak phase frequency does not necessarily occur between two consecutive phase angle peaks. In some embodiments, the drift of the peak phase frequency is determined between the peak phase frequency (f1) of an initial frequency scan and the peak phase frequency of a subsequent frequency scan (for example, f n or f n+1 ). Before embedding the concrete structure, the peak phase angle of the initial frequency can be determined during the calibration process of the piezoelectric aggregate. Alternatively, the peak phase angle of the initial frequency can be determined based on the first measurement result performed after the piezoelectric aggregate is embedded. In some embodiments, for determining the target state of the concrete structure, the drift of the peak phase frequency between the peak phase angle (f1) of the initial frequency scan and the peak phase angle (f n+1 ) of a subsequent frequency scan needs to satisfy a preset frequency range, for example, between 2 kHz and 10 kHz, such as 6 kHz between f1 and f n .

[0053] Still referring Figure 4 and Figure 6 , in some embodiments, the phase angle change corresponds to a change (Δp) in the peak phase amplitude between each of the phase angles obtained from a plurality of frequency scans. The peak phase amplitude corresponds to the phase amplitude at which the phase angle diagram / curve presents a peak, for example, at p1 or p n . For example, the change in the peak phase amplitude corresponds to a change or decrease in the peak phase amplitude from p n to p n+1 , or in other cases, from p1 to p nChange or reduction. In some embodiments, the change in the peak phase amplitude is determined between the corresponding peak phase amplitudes obtained in two successive frequency scans, i.e., between p n and p n+1 . In some embodiments, to determine the target state of the concrete structure, the change in the peak phase amplitude between two successive frequency scans needs to satisfy the peak phase amplitude within a preset amplitude range, for example, a 6-degree reduction from p n to p n+1 . The preset amplitude range is, for example, a range from 3 degrees to 8 degrees.

[0054] In some embodiments, to determine the target state of the concrete structure, both the preset conditions of a preset frequency range and the preset conditions of a preset amplitude range need to be satisfied. These preset conditions can correspond to a concrete bar dropping test with a penetration depth of 2 cm to 5 cm.

[0055] Figures 7 to 9 Shows examples of piezoelectric aggregates 110 (also referred to as EIM-SMA or smart aggregates) according to different embodiments of the present application. The piezoelectric aggregate may include a piezoelectric element 112 sandwiched between two concrete members 114 / 116. The two concrete members 114 / 116 together form a pellet of concrete mass. In some embodiments, the mass pellet can be a cylindrical or plate-shaped member, the thickness (Tp) of which in the thickness direction 90 is substantially less than the radius in the radial dimension 92. The piezoelectric element 112 may also have a thickness thinner than that of the concrete members 114 / 116. In some examples, the piezoelectric element 112 may have a thickness (Tp) of 1 mm to 2 mm, and each of the concrete members 114 / 116 may have a thickness (Tc) of about 5 mm. In some examples, the thickness ratio between the piezoelectric element 112 and each of the concrete members 114 / 116 is in the range of 1:5 to 2:5.

[0056] In some embodiments, the piezoelectric element 112 may be a piezoelectric thin plate having corresponding surfaces coated with a metallic paint, such as a Direct to Rust paint like Hammerite. In some embodiments, the piezoelectric element 112 may be a piezoelectric thin plate having corresponding surfaces coated with a thinner waterproof layer. The diameter (Dp) of the piezoelectric element 112 may be smaller than the diameter (Dc) of each of the concrete members 114 / 116. Thus, it is allowed that the piezoelectric element 112 is disposed between the two concrete members 114 / 116 in the thickness direction 90 and centered between the two concrete members 114 / 116 in the radial direction 92. For example, the two concrete members 114 / 116 may be made of the same concrete composition to set the centroid (M) on the plane of symmetry (P), where the plane of symmetry coincides with the interface between the two concrete members 114 / 116. For example, the two concrete members 114 / 116 may be substantially identical so that a plane of mirror symmetry is set for the mass block between the two concrete members 114 / 116. The piezoelectric element 112 may be described as being disposed in the plane of symmetry of the mass block and substantially encapsulated by the mass blocks 114 / 116. The piezoelectric element 112 may be substantially surrounded by the mass blocks 114 / 116 on all sides. It will be understood that this does not prevent providing one or more wires extending from the piezoelectric element (disposed within the mass blocks 114 / 116) to the outside of the mass blocks 114 / 116. Before putting the piezoelectric aggregate 110 into use, for example, before disposing the piezoelectric aggregate 110 in fresh concrete to monitor the curing or hardening of the fresh concrete, the mass blocks 114 / 116 are fully hardened concrete blocks.

[0057] In some embodiments, each of the concrete members 114 / 116 may be made of a mixture of cement, sand and gravel, and water. Without any intention of limitation, an example volume ratio of the mixture of cement, sand and gravel may be 1:0.5:0.4, respectively. In other examples, other combinations of concrete / mortar may also be viable candidate combinations for the concrete members 114 / 116.

[0058] Figure 10 and Figure 11 Illustrates the working principle of the piezoelectric aggregate 110. The working principle of the piezoelectric aggregate 110 may be based on the impedance method and the electromechanical coupling theory. According to the electromechanical coupling theory, the dynamic characteristics of the piezoelectric structure 310 including the piezoelectric element 312 and the coupling structure 314 are controlled by the interaction between the piezoelectric element 312 and the structure 314. The impedance of the piezoelectric structure 310 is determined by the characteristics of the piezoelectric element 312, the relative position of the piezoelectric element 312 with respect to the structure 314, the boundary conditions of the structure 314, the rigidity of the structure 314, etc.

[0059] Figure 10Schematic diagram showing a piezoelectric structure 310, which includes a circular piezoelectric cylinder 312 and a concrete cylinder 314. To better explain the dynamic interaction of the piezoelectric structure, Figure 11 Lumped parameter schematic diagram showing the piezoelectric structure 310. The piezoelectric element 312 has a certain piezoelectric coupling effect and elastic stiffness. When minimum manufacturing tolerances are not considered, piezoelectric elements 312 of the same model produced by reliable manufacturers can have assumed substantially similar or even exactly the same characteristics (i.e., piezoelectric coupling effect and elastic stiffness).

[0060] The concrete cylinder 314 is simplified and represented by a single degree of freedom (SDOF) mechanical oscillator, whose impedance is:

[0061]

[0062] where m, K s and c are respectively the mass, spring constant, and damping coefficient of the single degree of freedom mechanical oscillator.

[0063] Figure 11 The admittance (reciprocal of impedance) of the shown lumped model can be derived as:

[0064]

[0065] where and d A and h A are respectively the diameter and thickness of the piezoelectric cylinder. d 32 is the piezoelectric constant. For piezoelectric materials, ρ, η, and are respectively the mass density of the piezoelectric material, modulus at zero electric field, mechanical loss factor, and dielectric constant at zero stress.

[0066] When cement is mixed with water, a hydration reaction occurs, which results in shrinkage and hardening. In other words, the "stiffness" (k s ) of the concrete increases. Referring to calculation formula (1), the change in stiffness (k s ) will change the dynamic characteristics of the coupled system composed of the piezoelectric element 312 and the concrete material 314. Based on the above principle, the impedance of fresh concrete can be used for concrete monitoring.

[0067] In some embodiments, the piezoelectric aggregate 110 may be a smart aggregate (SMA) based on electromechanical impedance measurement (EIM) for monitoring fresh concrete or newly formed concrete. The piezoelectric aggregate may be suitable for mass production. In different embodiments, the smart aggregate is a piezoelectric aggregate or a piezoelectric-based aggregate that includes a piezoelectric element made of a piezoelectric material and operates using the piezoelectric element made of the piezoelectric material.

[0068] In some embodiments, the concrete monitoring method 200 may include obtaining a measured impedance value or result from the piezoelectric aggregate, which is directly or indirectly post-processed to represent the state of the concrete structure, such as the hardening condition of fresh concrete. In addition, the monitoring method 200 is simple and easy to implement, and can be automated to reduce the need for manual intervention. Therefore, the concrete monitoring system 100 and the concrete monitoring method 200 can be widely applied to construction sites or construction fields. In addition, since the concrete system 100 and method 200 have the characteristics of being simple and easy to implement and automated, the construction site workers may not need to have any prior knowledge or understanding of the working principles of the system 100 and method 200.

[0069] Figures 12A to 12D A mold 400 showing some embodiments for producing the piezoelectric aggregate 310 is shown. The mold 400 can be used for the rapid production of the proposed EIM-SMA or piezoelectric aggregate. The mold can be presented in different settings, where this application is an example. In this embodiment, the mold 400 includes two layers 410 / 420, such as Figure 12A the bottom layer 410 shown and such as Figure 12B the top layer 420 shown. Each layer 410 / 420 of the mold can be further divided into two parts, that is, the bottom layer 410 can be composed of two parts 412 / 414, and the top layer 420 can be composed of two parts 422 / 424. All parts 412 / 414 / 422 / 424 can be provided with handles to facilitate the demolding of the piezoelectric aggregate.

[0070] Pairs of screw holes may be provided at the edges of the parts 412 / 414 / 422 / 424 for assembly and fastening, thus forming a complete mold in the casting process of the piezoelectric aggregate (EIM-SMA) 110. After each layer among the multiple layers 410 / 420 is assembled (independently of any other layer among the multiple layers), the bottom layer can form a base having a protruding annular portion at the center, and the protruding annular portion has a diameter ( Figure 12A ); meanwhile, the top layer has a circular hole, and the circular hole has an inner diameter (Figure 12B )。The bottom layer and the top layer 410 / 420 can be further assembled by nested connection ( Figure 12C ). Molds can be manufactured using a 3D printer, thus significantly reducing the bare cost.

[0071] Figures 13A to 13C is an image showing the steps of manufacturing piezoelectric aggregates using the mold 400. The casting process of EIM - SMA can be performed in a few steps. As Figures 13A to 13C shown, the method of manufacturing piezoelectric aggregates may include:

[0072] Step 1: Pour concrete into the bottom layer of the mold and fill the bottom layer;

[0073] Step 2: Place a lead zirconate titanate (PZT) sheet at the center of the bottom layer and let the ends of the wires protrude from the mold; and

[0074] Step 3: Assemble the top layer onto the bottom layer by nested connection and fill the top layer with concrete.

[0075] Figure 14 shows the application of the concrete monitoring system 100, where three piezoelectric aggregates 110 are arranged at intervals with a minimum spacing (S). The three piezoelectric aggregates 110 can be arranged in an overlapping setting. The minimum spacing (S) minimizes the interference between the multiple piezoelectric aggregates 110, or results in minimized interference between the multiple piezoelectric aggregates 110. In some examples, the minimum spacing is about 1 meter. This embodiment can be an alternative to frequency scanning of the overlap of each of the multiple piezoelectric aggregates 110, so that the overall state of the concrete structure can be jointly determined at one time.

[0076] Refer to Figure 15 and Figure 16 , according to different embodiments of the concrete monitoring system, in addition to in - situ monitoring or wired mode, two wireless solutions are also proposed to make the measurement process more efficient and flexible. For some embodiments, the smart aggregates 110 are embedded in the slab 80a and column 80b of the concrete structure 80. In some embodiments, the smart aggregates 110 can be embedded in positions of the concrete structure 80 that are far from the formwork 82 and rebars 84.

[0077] Figure 15Shows the first scenario (Scenario I), in which each smart aggregate 110 can be connected to a transmitter 130 placed at the construction site. Alternatively, a multi-channel transmitter can be provided, allowing a single transmitter to communicate with multiple smart aggregates. The transmitter 130 can be provided with the function of an impedance analyzer. In other words, the transmitter 130 can perform impedance measurements locally. Subsequently, the impedance measurement or impedance spectrum results can be sent to the receiver 122. The receiver 122 can be physically located away from the construction site through wireless communication. When receiving the data or results, a computer 124 including a customized software program at the receiving end can be set to analyze and present detailed information related to the measurement results, such as but not limited to the visualization of the impedance spectrum. In Scenario I, the transmitter 130 includes an impedance analyzer function, which is set to perform local analysis of the impedance measurement results.

[0078] Figure 16 Shows the second scenario (Scenario II), in which the impedance analyzer function is integrated at the receiving end. This scenario can beneficially reduce costs and reduce the risk of damage to the analyzer function (under relatively harsh on-site conditions). In this embodiment, the transmitter 130 is responsible for collecting and transmitting raw data, that is, voltage and / or current signals, and can be set without the analyzer function of Scenario I. The raw data can be sent to the receiver through wireless communication for reception at the receiver 122 for post-processing. The post-processing can include converting the raw data (raw data of voltage and / or current signals) into impedance measurement results or impedance spectra. Subsequently, the computer 124 communicating with the analyzer 126 can be used to analyze and present detailed information of the measurement results, such as but not limited to the visualization of the impedance spectrum.

[0079] Figure 17Schematic working flowcharts of concrete monitoring systems according to different embodiments of the present application are shown. The workflow may include embedding piezoelectric aggregates or EIM-SMA units into fresh concrete at a construction site. Wires of each piezoelectric aggregate may be connected to an impedance analyzer. As an example, a precision impedance analyzer 6500B of Wayne Kerr Electronics Limited may be used to measure the impedance of the piezoelectric aggregate. As another example, Sciospec ISX3 may be used as the impedance analyzer to measure the impedance of the piezoelectric aggregate. The frequency scan range of the impedance analyzer may be up to 120 MHz at most, where the impedance measurement accuracy is ±0.05%. The measurement data may be saved as a.CSV file. In addition to the above settings, the 6500B series impedance analyzers may provide a General Purpose Interface Bus (GPIB) interface, that is, a parallel port designed to enable communication between the instrument and a control terminal such as other personal computers (PCs). In addition, the impedance analyzer also provides a Local Area Network (LAN) connector of a standard Registered Jack 45 (RJ45), which enables connection to a Fast Ethernet network. In other words, the impedance analyzer has an extended function that allows remote control.

[0080] Subsequently, the impedance analyzer may be controlled or set to measure at fixed time intervals, such as every 10 minutes to 30 minutes, and record the results. The measurement results are collected in the raw data format and stored in the same folder. For a given piezoelectric aggregate under free conditions or before being embedded in a concrete structure, a frequency scan may be performed over a frequency range of 20 kHz to 200 kHz. For example, any distinct frequency peaks at about 60 kHz are noted. After the piezoelectric aggregate is embedded in the concrete, it is noted that the resonance frequency of the piezoelectric aggregate under restricted conditions will increase. Therefore, the measurement frequency range is set within the range of 40 kHz to 100 kHz to account for this frequency increase.

[0081] Impedance is a complex number that can be represented according to its real part and imaginary part. Alternatively, impedance can also be represented according to its magnitude and phase angle. The magnitude of the impedance and its decomposed real and imaginary parts are related to many factors and can vary within a large range. During the process of concrete hardening, the magnitude of the impedance of the piezoelectric aggregate may increase monotonically.

[0082] The peak (impedance amplitude) corresponding to the electromechanical coupling resonance in the impedance plot may exhibit a local maximum. The peaks of the impedance amplitude are generally difficult to detect or identify with consistent repeatability.

[0083] In terms of instrument settings, this method involves obtaining the amplitude and phase angle of the impedance as parameters to be measured. Under current conditions, the natural limit of the phase angle is between -90 degrees and 90 degrees, and the peaks in the phase angle plot tend to correspond to global maxima. Once the instrument settings are determined, the instrument settings can be stored (during the setting process) in the memory of the controller and / or computing device. This allows other operators without prior knowledge of the system setting parameters to load the settings from the memory for rapid measurements.

[0084] In the tests performed, a written Matlab program was provided to automatically identify the raw data, analyze the evolution of the impedance, and / or parse the state of the concrete, such as the hydration state or the maturity of the concrete. In other examples, Python scripts and the ISX3 impedance analyzer of Sciospec that provides impedance data can also be used for testing. The tests are described below as examples for illustrative purposes only and are not limiting. To monitor the state of the concrete, repeated measurements of the impedance are performed every 10 minutes to 30 minutes. By implementing an advanced impedance analyzer based on the method proposed herein, the instrument can automatically and even remotely complete the task of determining the strength of the concrete structure in a consistent manner at different times over a period. This advantageously enables a relatively large amount of data collection to be obtained and processed during the entire acquisition process of the measurement data without the need for personnel to be constantly on-site.

[0085] In the Matlab program, a file naming scheme was proposed to enable automatic identification of the raw data files to be post-processed. The raw data files can be named with the same prefix, such as agg4. A delimiter, such as a hyphen (-) or an underscore (_), can be after the prefix. Time information is preferably represented after the delimiter. The following are some examples of acceptable file names: "agg4-30mins.csv", "agg5_210mins.csv", etc.

[0086] Before executing the Matlab algorithm, the program file and the test data file are placed in the same folder. Figure 18It is a flowchart showing an example of an algorithm for automatically processing data. The algorithm first searches for all.CSV files in the current directory. If there are no.CSV files in the current directory, the algorithm will display an error message to the user. According to the prefixes and delimiters that appear in the file names, the algorithm will first filter out all the files and identify the test data files. Subsequently, according to the test time information contained in the file names, the data files are sorted. The algorithm will read the data in those files in sequence. If the data file format is incorrect, the algorithm will display an error message to remind the user. Assuming that the data in the file is successfully read by the algorithm, the data will be stored in the Matlab workspace. Then, the peak search algorithm will be used to identify the peaks and refine the corresponding frequency and amplitude information. Subsequently, the peak evolution trend will be plotted with reference to time to reflect the development process of the hydration state or maturity of the concrete. The diagram will be saved as a.jpeg format picture in the current directory.

[0087] Two separate Matlab programs were developed to implement the above algorithm. Matlab Program I is responsible for identifying and sorting the.CSV files in the current directory. Matlab Program II is responsible for post-processing the identified.CSV files. The following Table 1 and Table 2 provide a detailed description of the functions, inputs, and outputs of the Matlab programs.

[0088] Table 1: Matlab Program I

[0089]

[0090]

[0091] Table 2: Matlab Program II

[0092]

[0093] Calibration and Correlation Analysis

[0094] According to different embodiments of the present application, the method proposed herein includes predicting the maturity or hardening condition based at least on the phase angle of the measured impedance. This prediction can be based on one or more reference data developed to assist in the analysis of impedance measurement results. For example, in the tests performed, a set of reference data is developed based on the conventional falling rod test. Alternatively or additionally, reference data related to concrete maturity and based on other tests can be used. As an illustrative example, the falling rod test is selected for experimentation because users are accustomed to describing the maturity of concrete based on the results of the falling rod test. The method does not exclude the use of reference data obtained by other means. The method does not exclude the feasibility that correlation back reference becomes unnecessary for the analysis of impedance measurement results. For example, the method is widely accepted in the industry and / or incorporated into industry standards. In the tests performed, the measured impedance is correlated with the falling rod depth to represent the maturity of the concrete. Table 3 lists the mixing ratios of the constituent materials of the concrete used for testing and monitoring in the experiment.

[0095] Table 3: Summary of Mixing Ratios

[0096]

[0097] To ensure that the established correlation mapping relationship is indeed applicable to multiple piezoelectric aggregates, the multiple piezoelectric aggregates are calibrated to exhibit the same initial impedance characteristics under free conditions, i.e., before being embedded in fresh concrete. Multiple piezoelectric aggregates calibrated with a common reference can be used in different scenarios without the need for recalibration. This means that compared to, for example, the falling rod test, the change in concrete maturity can be monitored over a period of time with more consistent and quantifiable results. The results of the falling rod test can be affected to some extent by the inherent random manner of releasing the object by hand and the inherent random manner of the object hitting the ground. The results of the falling rod test can include significant fluctuations. For example, although the penetration depth generally decreases over time, the actual measurement results show that the change in penetration depth is not necessarily a monotonic change. In a feasible application scenario, piezoelectric aggregates can be mass-produced and calibrated according to standard references so that they can be directly used by construction workers on-site without the need for each construction worker to perform individual calibration for each concrete structure to be monitored. This will help solve the volatility problem in the falling rod tests performed on-site.

[0098] As an example, Figure 19 and Figure 20Shows a correlation map between a series of impedance results (obtained from the present method and piezoelectric aggregates) and the results obtained from a conventional drop-weight test. In this example, the test is performed on G40 concrete. The peaks of the impedance phase include two aspects: the drift of the peak phase frequency and the change in the peak phase amplitude. The Figure 19 and Figure 20 two figures are plotted to show the correlation between the peak phase frequency (obtained using the proposed piezoelectric aggregates) and the peak phase amplitude (obtained using the proposed piezoelectric aggregates) and the penetration depth (obtained using the conventional drop-weight test). As the concrete hardens, it can be observed that the penetration depth decreases with time.

[0099] It can be observed that the peak phase frequency or the impedance peak frequency increases monotonically during this process, indicating an increase in the "stiffness" of the concrete, which is consistent with the hardening process of the concrete. During the hardening process of this concrete, the peak phase amplitude decreases monotonically and provides another indicator reflecting the maturity or hardening condition of the concrete. Association or calibration includes establishing a look-up table or a fitting function applicable to correlating the impedance results (obtained from piezoelectric aggregates) with the drop-weight test or other reference results.

[0100] Once the calibration is completed, for a given impedance measurement result (peak phase frequency and peak phase amplitude), the state or the hardening condition of the concrete can be analyzed by referring to the look-up table or by using the fitting function. Once the correlation map is established, a reference in the form of a look-up table, a fitting function, etc. can be used to analyze the impedance measurement results for any standardized piezoelectric aggregate. The "standardized piezoelectric aggregate" used in this article refers to a piezoelectric aggregate or an EIM-SMA unit that has been calibrated (pre-calibrated) according to the same or similar reference. The drift of the peak phase frequency and the change in the peak phase amplitude can be refined. Subsequently, the state or the maturity development condition of the concrete can be obtained by referring to the correlation map. The greater the drift of the peak frequency, the higher the degree of curing of the concrete; and the greater the change in the peak amplitude, the higher the degree of curing of the concrete.

[0101] From the description provided above, several beneficial applications of the proposed system and method can be understood. For example, for the purpose of monitoring concrete structures, it is known that the conventional drop-weight test provides relatively inconsistent measurement values. In addition, the drop-weight test can cause irreversible damage to the concrete structure, such as the formation of internal cracks or damage to the external surface. Another disadvantage of the drop-weight test is that it needs to be repeatedly performed by workers on-site. These problems and other problems can actually be alternatively solved by using the system and method proposed in this article.

[0102] The drop weight test can be affected by many external factors. Therefore, several parallel drop weight tests usually produce non-negligible differences. Compared with the results of the drop weight test, the impedance curve is relatively smooth and has better monotonicity. In addition, impedance measurement can be automatically performed by the instrument without manual intervention. This indicates that it is feasible to avoid or significantly reduce operator-related external factors, and for monitoring the state of concrete structures, the proposed system and method are more reliable solutions.

[0103] On the one hand, different embodiments of the present application include a concrete monitoring system. The concrete monitoring system includes at least one piezoelectric aggregate that can be embedded in a concrete structure; and a controller. The controller is configured to: perform a plurality of frequency scans on the at least one piezoelectric aggregate to obtain a plurality of phase angles; and determine the state of the concrete structure based on the phase angle change between some of the plurality of phase angles. In different embodiments, the state of the concrete structure corresponds to the hydration state of the concrete structure. In different embodiments, the state of the concrete structure includes the screeding state of the concrete structure, where in this screeding state, the concrete structure is suitable for screeding the concrete surface. In different embodiments, the phase angle change between some of the plurality of phase angles includes the phase angle change between some of the plurality of phase angles of the same piezoelectric aggregate. In different embodiments, the phase angle change includes the drift of the peak phase frequency between some of the plurality of phase angles. In different embodiments, the drift of the peak phase frequency is determined between an initial frequency scan and a subsequent frequency scan. As an example, the drift of the peak phase frequency is in the range of 2 kHz to 10 kHz.

[0104] In different embodiments, the change in the phase angle includes the change in the peak phase amplitude between some of the plurality of phase angles. In different embodiments, the change in the peak phase amplitude is determined between the corresponding some of the plurality of phase angles of two consecutive frequency scans. In different embodiments, the change in the peak phase amplitude corresponds to a decrease in the peak phase amplitude in the range of 3 degrees to 8 degrees. In different embodiments, the plurality of frequency scans are performed orderly based on a measurement schedule.

[0105] In different embodiments, the plurality of frequency scans are performed iteratively based on a measurement cycle rate. For example, the measurement cycle rate is one frequency scan every 30 minutes or less than 30 minutes. In some examples, each of the plurality of frequency scans is performed within a scan frequency range, and the range of the scan frequency is between 30 kHz and 100 kHz.

[0106] In different embodiments, each of the at least one piezoelectric aggregate includes a piezoelectric element sandwiched between two concrete members. In some examples, the thickness ratio between the piezoelectric element and each of the plurality of concrete members is 2:5 or less than 2:5. In different embodiments, the piezoelectric element is a piezoelectric thin plate having corresponding surfaces coated with a metal coating. In different embodiments, the corresponding surfaces of the piezoelectric element are coated with a thin waterproof layer. In different embodiments of the concrete monitoring system, the at least one piezoelectric aggregate includes two piezoelectric aggregates separated by a minimum spacing, where the minimum spacing corresponds to the minimal interference between the two piezoelectric aggregates. In different embodiments, the controller is further configured to determine the state of the concrete structure during the maturation process of the concrete structure.

[0107] According to another aspect of the present application, in different embodiments, a concrete monitoring method is disclosed. The method includes performing a plurality of frequency scans on at least one piezoelectric base aggregate embedded in a concrete structure to obtain a plurality of phase angles; and determining the state of the concrete structure based on a phase angle change between some of the plurality of phase angles. In different embodiments, the method further includes determining a target state of the concrete structure based on the change in the phase angle, where in the target state, the concrete structure is suitable for finishing the concrete surface. In different embodiments, the method further includes determining the state of the concrete structure during the maturation process of the concrete structure.

[0108] All examples described herein, whether of apparatus, method, material, or product, are presented for illustrative and aiding understanding purposes and are not intended to be limiting or exhaustive. Those of ordinary skill in the art may make modifications without departing from the scope of the claims of the present application.

Claims

1. A concrete monitoring system, comprising: At least one piezoelectric aggregate that can be embedded in a concrete structure; And A controller, the controller being configured to: Perform a plurality of frequency scans on the at least one piezoelectric aggregate to obtain a plurality of phase angles; And Determine the state of the concrete structure based on a phase angle change between some of the plurality of phase angles.

2. The system according to claim 1, wherein the state of the concrete structure corresponds to the hydration state of the concrete structure.

3. The system according to claim 1 or 2, wherein the state of the concrete structure includes the screeding state of the concrete structure, wherein in the screeding state, the concrete structure is suitable for concrete surface screeding.

4. The system according to any one of claims 1 to 3, wherein the phase angle change between some of the plurality of phase angles includes a phase angle change between some of the plurality of phase angles of the same piezoelectric aggregate.

5. The system according to any one of claims 1 to 4, wherein the phase angle change includes a drift of the peak phase frequency between some of the plurality of phase angles.

6. The system according to claim 5, wherein the drift of the peak phase frequency is determined between an initial frequency scan and a subsequent frequency scan.

7. The system according to claim 5 or 6, wherein the drift of the peak phase frequency is in the range of 2 kHz to 10 kHz.

8. The system according to any one of claims 1 to 7, wherein the phase angle change includes a change in the peak phase amplitude between some of the plurality of phase angles.

9. The system according to claim 8, wherein the change in the peak phase amplitude is determined between corresponding ones of the plurality of phase angles of two consecutive frequency scans.

10. The system according to claim 8 or 9, wherein the change in the peak phase amplitude corresponds to a decrease in the peak phase amplitude in the range of 3 degrees to 8 degrees.

11. The system according to any one of claims 1 to 10, wherein the plurality of frequency scans are performed in an orderly manner based on a measurement schedule.

12. The system according to any one of claims 1 to 11, wherein the plurality of frequency scans are performed iteratively based on a measurement cycle rate.

13. The system according to claim 12, wherein the measurement cycle rate is one frequency scan every 30 minutes or less than 30 minutes.

14. The system according to any one of claims 1 to 13, wherein each of the plurality of frequency scans is performed within a scan frequency range that is between 30 kHz and 100 kHz.

15. The system according to any one of claims 1 to 14, wherein each of the at least one piezoelectric aggregate includes: A piezoelectric element sandwiched between two concrete members.

16. The system according to claim 16, wherein the thickness ratio between the piezoelectric element and each of the concrete members is 2:5 or less than 2:

5.

17. The system according to claim 15 or 16, wherein the piezoelectric element is a piezoelectric thin plate having a respective surface coated with a metal coating.

18. The system according to claim 17, wherein the respective surface of the piezoelectric element is coated with a thin waterproof layer.

19. The system according to any one of claims 1 to 18, wherein the at least one piezoelectric aggregate includes two piezoelectric aggregates separated by a minimum spacing, and the minimum spacing corresponds to the minimum interference between the two piezoelectric aggregates.

20. The system according to any one of claims 1 to 19, wherein the controller is further configured to determine the state of the concrete structure during the maturation process of the concrete structure.

21. A method for monitoring concrete, comprising: performing a plurality of frequency scans on at least one piezoelectric base aggregate embedded in a concrete structure to obtain a plurality of phase angles; and determining the state of the concrete structure based on a phase angle change between some of the plurality of phase angles.

22. The method according to claim 19, further comprising: determining a target state of the concrete structure based on the phase angle change, wherein in the target state, the concrete structure is suitable for finishing the concrete surface.

23. The method according to claims 21 to 22, further comprising determining the state of the concrete structure during the maturation process of the concrete structure.

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