RU2535239C2 - Method and system for analysis of chemically active material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method and system for determining a period of a chemically active material setting are claimed. The method includes continuous measurement of an electric property of the material in order to obtain the time dependence of the specific resistance or its representation. The time dependence is used for the determination of the time of the setting beginning and the time of setting ending. The time of the setting beginning is determined as the time when the fastest rise of the specific resistance starts and the time of the setting ending is determined as the time of the local maximum of the specific resistance.

EFFECT: increase of the method efficiency.

28 cl, 15 dwg, 1 tbl

Description

FIELD AND BACKGROUND

The present invention, in some embodiments, relates to the analysis of a material and, more specifically, but not exclusively, to the analysis of a reactive material that undergoes a hardening process, such as, but not limited to, a cementitious material, such as concrete.

Chemically active material often needs to be analyzed to determine its structural properties, for example, strength and other physicomechanical properties of the final aged product, such as its shrink potential. The final strength of a reactive capillary-porous material is determined by the properties of the raw materials, mixing and compaction conditions, specific composition, for example, the ratio of mineral binder and aggregate, the ratio of water to cement, the ratio of water to aggregate, etc. [Neville E.M. (Neville A.M.), Concrete Properties, Longman Scientific & Technical, 1981].

The process of solidification of a chemically active material can be considered as a series of successive transitions between different states of the material.

Initially, the material is a densified structure, the physical and mechanical properties of which are determined mainly by the compressive action of capillary pressure on the water-air boundaries. This condition is characterized by the intensive development of chemical reactions, such as hydration and hydrolysis with the formation of a gel (the term “gel” was introduced into scientific practice in combination with cementing materials by T. Powers in an article entitled “Non-evaporative water content in hardened solutions Portland cement "published in ASTM Bulletin, 1949, No.158, and was used by E. Neville in an article entitled" Concrete Properties "published in Longman Scientific & Technical, 1961).

In the second after the initial state, the material develops a coagulation structure, which is a capillary-porous colloidal body having chemically active dispersions of water-silicate.

In the third state, the material develops a colloidal crystalline structure, which is a quasi-solid capillary porous body. In this state, the gel begins to age and crystalline structures form.

In the fourth state, crystalline structures condense, and the material has a solid capillary-porous body, the conditions in which are determined by laws governing the interaction of particles and particle clusters in the solid phase.

In any single state, the chemically active material has a polydisperse structure of a moist capillary-porous body. The liquid phase of the material is therefore an informative component indicating the porosity of the material and, therefore, its strength. Water (in liquid and gaseous form) is always in a state of thermodynamic equilibrium with the porous solid phase with which it interacts. So, the properties of water change in strict accordance with the formation of the structure and subsequently with an increase in the strength of the hardened material. See, for example, Shtakelberg D.I. (Shtakelberg D.I.) and Sitkov M.M. (Sithcov M.M.), "Self-organization in dispersed systems", Riga, "Zinatne" Press, 1990; and Stackelberg D.I. (Shtakelberg D.I.), "Thermodynamics of structure formation in water-silicate dispersed materials", Riga, Zinatne, 1984; and Neville M. (Neville M.) "Concrete Properties", Longman Scientific & Technical. NT., 1988.

The duration of the above solidification process is usually quite long. For example, for cementitious materials, the curing time is of the order of one month, and during this period of time, cement passes through all the above conditions and becomes a solid structure with a certain compressive strength.

Due to the long duration of the hardening process until the final strength is reached, the chemically active material undergoes many complex physical and chemical processes that significantly affect its physical properties. It is generally recognized that any change, non-compliance or deviation from technological rules in the preparation of chemically active material, such as ready-mixed concrete or precast concrete, can irreversibly degrade the properties (e.g. strength) of the final product. The reasons for the poor quality of the final product include unexpected replacement of material suppliers, malfunctioning or equipment failure, etc.

The hardening and hardening of the reactive material begins immediately after completion of its compaction for a specific application. However, there may be many additional processes that affect the final quality. For example, in the case of concrete, transportation of the mixture from the manufacturer to the construction site usually occurs between the preparation of the mixture and its compaction. Although during transportation the concrete mixture is in constant motion inside the rotating drum to prevent setting or hardening, it is known that the final properties of cementitious products made after prolonged transportation of the mixture differ from the properties of the same products made from freshly prepared mixture.

Long-term transportation of the mixture naturally extends the period of time during which chemical reactions such as hydration and hydrolysis take place. So, upon arrival at the construction site, different transportation times lead to different initial conditions in the hardening and hardening processes.

Other factors that are known to change the hardening process include chemical additives for various functional purposes, temperature conditions during hardening, exposure conditions of freshly formed concrete, heterogeneity of the mixture, complexity and duration of the manufacturing process, etc.

Traditionally, the solidification process is controlled by mechanical means in one or several ways, such as testing a concrete mixture for a cone settlement, determining the Web stiffness, setting time testing, compressive strength testing, etc.

When testing a concrete mixture for sediment, a cone (called a cone for determining mobility) is placed on the base and filled with concrete. The cone is raised, leaving concrete that settles. The cone is placed on the base as a control and the difference in level between its top and the top of the concrete is measured. This test is usually applied to fresh concrete within the first three hours of the preparation of the concrete mix. Fast sludge (also referred to in the literature as "high" sludge) is observed when the amount of physically bound water in concrete is relatively large, and slow sediment occurs when the amount of physically bound water in concrete is relatively small.

When determining stiffness on the Web, the work required to compact concrete is measured. The concrete cone is placed on the table and raised as in a draft test. The table vibrates at a standard frequency. Measure the time required for concrete compaction. Web times range from 1 second for flowing concrete to over 12 seconds for hard concrete. The test on the Web is usually applied within 3-10 hours from the time of preparation of the concrete mixture.

When checking the setting time of concrete, the setting time is estimated by measuring the penetration resistance of a mortar obtained by passing a concrete mixture through a sieve. The penetrating device is in the form of a needle or wedge and is known as the Proctor penetrometer. Proctor penetrometer is usually used within 10-24 hours from the time of preparation of the concrete mix.

Compression strength testing is usually performed after exposure. A concrete sample is placed in a press and subjected to a gradually increasing compression pressure to determine the breaking load. Compressive strength is defined as the ratio between the breaking load and the cross-sectional area that resists the load. A peel test is also known in which an axial peel force is applied to a steel plate fixed to a concrete surface, and a shock test in which a smooth rod is driven into concrete and the penetration depth and / or peel force is measured.

In an article by Lee et al. (Li et al.) [Determination of concrete setting time using electrical resistivity measurements. ” Journal of Materials in Civil Engineering, Vol.19, No.5, 423-427 (2007)] discloses a method for determining the setting time of concrete by measuring electrical resistivity. Two critical points are determined on the resistivity curve and setting time is estimated as a linear function of the abscissa values of these critical points.

Other methods are disclosed in published international applications WO 2001/065282, WO 2005/047891 and WO 2005/124339 and in US patent No. 6,396,265, 7,181,978 and 7,225,682, the contents of which are incorporated by reference.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a method for determining the setting time of a reactive material is provided. The proposed method includes the continuous measurement of the electrical properties of the material to obtain the time dependence of this property, the property being resistivity or its representation; the use of the time dependence for determining the start time of setting and the end time of setting, where the start time of setting is defined as the time of the onset of the fastest rise in resistivity and the end time of setting is defined as the time of the local maximum of specific resistance; thus determining the setting time period of the material.

According to some embodiments of the invention, the method further comprises using a time relationship to detect a transition between the operating state of the material and the non-operational state of the material.

According to some embodiments of the invention, the method further comprises using a time dependence to detect a transition between the first working state of the material and the second working state of the material, which transition is equivalent to a sharp deceleration of precipitation, which would be observed if the material were subjected to a precipitation test.

According to some embodiments of the invention, the method further comprises using a time dependence to detect a transition between the gel state of the material and the capillary-porous colloidal state of the material.

According to some embodiments of the invention, the method further comprises using a time dependence to detect a transition between the capillary-porous colloidal state of the material and the colloidal-crystalline state of the material.

According to some embodiments of the invention, the method further comprises using a time dependence to detect a transition between the discontinuous crystalline state of the material and the continuous crystalline state of the material.

According to some embodiments of the invention, the method further includes using a time dependence to determine the compressive strength of the material.

According to another aspect of the present invention, there is provided a system for determining a setting period of a reactive material. The system comprises a measuring unit for continuously measuring the electrical property of a material in order to obtain a time dependence of such a property, the property being resistivity or its representation; and a processing unit for determining, based on a time dependence of the setting time and setting time, where the setting time is defined as the time of the fastest rise in resistivity and the time of setting to be determined as the local maximum resistance time.

According to some embodiments of the invention, the processing unit is configured to detect a transition between the operating state of the material and the inoperative state of the material based on the time dependence.

According to some embodiments of the invention, the transition between the operational and non-operational states is defined as the time of the local minimum of resistivity.

According to some embodiments of the invention, the transition between the operational and non-operational states is detected on a linear time scale.

According to some embodiments of the invention, a local minimum is detected using a time window having a width of about 2 hours.

According to some embodiments of the invention, the processing unit is configured to detect a transition between the first working state of the material and the second working state of the material based on the time dependence, the transition being equivalent to a sharp deceleration of the precipitation that would occur if the material were subjected to a precipitation test.

According to some embodiments of the invention, the transition between the first and second operating states is defined as the time corresponding to the inflection point of the resistivity curve.

According to some embodiments of the invention, the transition between the first and second operating states is detected on a linear time scale.

According to some embodiments of the invention, the inflection point of the curve is detected using a time window having a width of about 2 hours.

According to some embodiments of the invention, the processing unit is configured to detect a transition between the gel state of the material and the capillary-porous colloidal state of the material based on the time dependence.

According to some embodiments of the invention, the processing unit is configured to detect a transition between the capillary-porous colloidal state of the material and the colloidal-crystalline state of the material based on the time dependence.

According to some embodiments of the invention, the processing unit is configured to detect a transition between the discontinuous crystalline state of the material and the continuous crystalline state of the material based on the time dependence.

According to some embodiments of the invention, the processing unit is configured to determine the compressive strength of the material based on the time dependence.

According to some embodiments of the invention, each of the setting start time and the setting end time is identified on a linear time scale.

According to some embodiments of the invention, each of the beginning of the fastest rise in resistivity and local maximum resistivity is detected using a time window having a width of about 2 hours.

In some embodiments, the electrical property is measured by direct contact with the material.

In some embodiments, the electrical property is measured in a constant volume.

In some embodiments, the electrical property is measured by creating an electric field between the first electrode and the second electrode along a sufficiently long contour in the material.

According to some embodiments of the invention, the circuit has a length that is at least two times the distance between the electrodes.

Unless otherwise indicated, all technical and / or scientific terms used in the present description have the same meaning as is generally understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, illustrative methods and / or materials are described below. In the event of a conflict, a description of the invention, including definitions therein, takes precedence. In addition, the materials, methods and examples are illustrative only and are not intended to be limiting.

Implementation of a method and / or system according to embodiments of the invention may include performing or completing selected tasks manually, automatically, or in a combination of manual and automatic modes. Moreover, according to actual instruments and equipment for embodiments of the method and / or system of the present invention, several selected tasks can be performed by hardware, software, or firmware, or a combination thereof using an operating system.

For example, hardware for performing selected tasks according to embodiments of the invention may be implemented in the form of a chip or microcircuit. As software, selected tasks in accordance with embodiments of the invention may be implemented as a plurality of software instructions executed by a computer with any suitable operating system. In an exemplary embodiment of the invention, one or more tasks according to exemplary embodiments of the method and / or system described herein are performed by a data processor, such as a computer platform for executing a plurality of instructions. Optionally, the data processor includes a volatile memory for storing instructions and / or data and / or non-volatile memory, for example a magnetic hard disk and / or removable media, for storing instructions and / or data. Optionally, a network connection is also provided. Optionally, a display and / or user input device such as a keyboard or mouse are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are described here by way of example only with reference to the accompanying drawings. Now, with specific references to the detailed drawings, it is necessary to emphasize that the details given are by way of example only and for the purpose of illustratively describing embodiments of the invention. In this regard, the description taken along with the drawings will give those skilled in the art a clear understanding of how embodiments of the present invention can be practiced.

FIG. 1 is a flow chart of a method suitable for determining a setting period of a reactive material according to various illustrative embodiments of the present invention.

FIG.2 is a schematic representation of the time dependence of the electrical resistivity of a reactive material, measured according to the content of some embodiments of the present invention.

FIG. 3 is a schematic representation of a measuring device according to various illustrative embodiments of the present invention.

FIG. 4 is a schematic diagram of a system suitable for determining a setting period of a reactive material according to various illustrative embodiments of the present invention.

5 is the resistivity (pure squares) and strength (filled circles) as a function of time in hours, measured in experiments conducted according to some variants of implementation of the present invention.

FIGA-B - the results of mechanical tests (FIG.6A) and measurements of resistivity (FIG.6B), performed in accordance with some variants of implementation of the present invention in a period of time of 24 hours.

FIG.7 is a correlation between strength and electrical resistivity, measured in accordance with some variants of implementation of the present invention during the first 500 hours.

FIG. 8 is the electrical resistivity as a function of time in hours, measured in experiments conducted according to some embodiments of the present invention.

FIG.9 is a comparison between the energy of bound water and electrical resistivity for a standard cement-sand mixture according to one preferred embodiment of the present invention.

FIGURE 10 is the time dependence of the electrical resistivity of fine-grained concrete mixtures using fine-grained dolomite aggregates purchased in the quarry of Kohav-Ha-Shahar, Israel.

11 - time dependence of electrical resistivity of fine-grained concrete mixtures using fine-grained dolomite aggregates purchased in the quarry of Shfaram, Israel.

FIG.12A-C - comparisons between the time dependence of the compressive strength and electrical resistivity of fine-grained concrete mixtures with FIG.10 for the ratio of cement and water 0.60 (FIG.12A), 0.67 (FIG.12B) and 0.75 (FIG. 12C).

FIG.13A-C - comparisons between the time dependences of the compressive strength and electrical resistivity of fine-grained concrete mixtures with FIG.11 for the ratio of cement to water 0.60 (FIG.13A), 0.67 (FIG.13B) and 0.75 (FIG.13C).

FIG. 14 is a graphical representation of the correlation function between the time dependences of electrical resistance and compressive strength of fine-grained concrete mixtures with FIG. 10.

FIG. 15 is a graphical representation of the correlation function between the time dependences of the electrical resistance and compressive strength of the fine-grained concrete mixtures of FIG. 11.

DESCRIPTION OF SPECIFIC EMBODIMENTS FOR CARRYING OUT THE INVENTION

The present invention, in some embodiments, relates to the analysis of a material and, more specifically, but not exclusively, to the analysis of a reactive material that undergoes a hardening process, such as, but not limited to, a cementitious material, such as concrete.

Before a detailed explanation of at least one embodiment of the invention, it must be said that the invention is not necessarily limited in its application to the details of the construction and arrangement of the components and / or the methods set forth in the description below and / or illustrated in the drawings and / or Examples. The invention may have other embodiments and may be practiced in various ways.

As used herein, the term “reactive material” refers to a material that undergoes a hardening aging process. Representative examples of chemically active materials analyzed in the present embodiments include cementitious materials, such as concrete, mortar, and non-cementitious materials, such as gypsum, clay, and ash. Other reactive materials analyzed in the present embodiments are curable organic pastes, such as, but not limited to, epoxy based pastes.

Since concrete and similar cementitious materials are widely used because of their high versatility and low cost, embodiments are described below with particular emphasis on concrete. However, it should be understood that a more detailed reference to concrete should not be construed as in any way limiting the scope of the invention.

The hardening and hardening of cementitious materials occurs due to the joint development of complex physical and chemical processes. The energy of these processes leads to a chemical reaction of hydration, as well as hydrolysis of mineral binders (cement, gypsum, limestone, etc.) present in the material. As soon as a sufficient amount of the product of these reactions accumulates per unit volume, a capillary-porous structure begins to form, first as a coagulation structure (long-range and short-range) and then as a colloidal and crystallization structure.

Although at the beginning of the development of hydration and hydrolysis, the properties obtained by the material are reversible, after the formation of a short-acting coagulation structure, the properties of the material become irreversible.

The reason for the reversibility at the beginning of the development of hydration and hydrolysis is the long-range coagulation structure of the material. This structure has thixotropic properties that allow reverse processes, for example, after the application of a certain mechanical action. On the other hand, in a short-range coagulation structure, the formation of an initial crystalline framework completes all the mechanical transitions in the material, hindering the reverse processes.

Thus, the process of crystallization hardening deterministically develops from the initial conditions established at the time of formation of the short-range coagulation structure. Since these initial conditions depend on the mechanical state of the material, when its structure still has a long-range character, it is understood that the mechanical transitions occurring at this time substantially determine the subsequent crystallization of the material and its strength.

Now with reference to the drawings. FIG. 1 shows a flow chart of a method suitable for determining a setting time of a reactive material according to various illustrative embodiments of the present invention. You must understand that, unless otherwise indicated, the steps of the method described below can be performed simultaneously or sequentially in numerous combinations or execution orders. Specifically, the order of technological schemes should not be construed as limiting. For example, two or more operations mentioned in the following description or in technological schemes in a specific order can be performed in a different order (for example, in the reverse order) or in essence simultaneously. Additionally, several of the operations described below are optional and may not be performed.

The method starts at position 10 and moves to position 11, in which the electrical property of the material is measured to obtain a time dependence of such a property. In various illustrative embodiments, the electrical property is measured continuously. The electrical property is preferably the electrical resistivity ρ of the material, but it can also be a representation of electrical resistivity, such as electrical resistance, electrical impedance (real and / or imaginary part), electrical conductivity, electrical conductivity, etc. The average person skilled in the art will understand that although resistivity and conductivity are specific properties that depend on the type of material and its thermodynamic state, but not on its shape and size, resistance and electrical conductivity are nonspecific characteristics that depend on type, thermodynamic state , shape and size of the material. For any given shape and size of the material, a specific property can always be determined by a non-specific characteristic, and vice versa.

The electrical property can be measured by any method known in the art. Preferably, the electrical property is measured by direct contact with the material. Namely, two or more electrodes are brought into physical contact with the material and voltage is applied between the electrodes in order to measure the electrical property. In one preferred embodiment, the electrical property is measured by creating an electric field between the electrodes along a sufficiently long contour in the material. Typically, the circuit has a length that is at least two times the distance between the electrodes. In various illustrative embodiments, the electrical property is measured in a constant volume. The author of the present invention unexpectedly found that the use of a sufficiently long contour in the material allows the identification of transitions that cannot be identified by other methods. A preferred apparatus for measuring electrical property using a sufficiently long circuit is described below.

FIG. 2 schematically shows the time dependence of the electrical resistivity of a reactive material measured according to some embodiments of the present invention. Figure 2 shows several identifiable transition points (P ₁ -P ₄ ). As will be explained below, the method of embodiments of the present invention can identify at least several such points in time dependence and associate material state transitions for each identified point. In various illustrative embodiments of the invention, one or more, preferably all transition points are detected on a linear scale of the resistivity curve. In various illustrative embodiments of the invention, one or more, preferably all transition points, are detected using a time window having a width of about 2 hours.

In some embodiments, implementation of the present invention, the method moves to position 12, in which the transition from the first working state of the material to the second working state, using the time dependence. In this transition, the amount of physically bound water in the material decreases sharply due to the formation of chemical bonds between water molecules and the solid phase. Traditionally, this transition is detected by a cone draft test, where a sharp deceleration of precipitation is observed. For example, in the first working state, when the amount of physically bound water is relatively large, a typical precipitate is approximately 16-20 cm, and in the second working state, when the amount of physically bound water is reduced, a typical precipitate is less than 6 cm. In known analysis methods, when such a sharp deceleration of precipitation is observed; the cone test is replaced by the Web test. Thus, the present embodiments are capable of identifying a transition that is equivalent to a sharp deceleration of precipitation that would occur if the material were subjected to a precipitation test.

The transition between these two operating states is preferably associated with the inflection point of the resistivity curve (see point P ₁ in FIG. 2). In this embodiment, the transition time is defined as the time t ₁ that corresponds to the point P ₁ .

In some embodiments of the invention, the method moves to position 13, in which a transition from a working state of the material (usually the aforementioned second working state) to a non-working state of the material is detected. Traditionally, this transition is revealed by testing on the Web, in which a time plateau of the Web is observed. In traditional analysis methods when observing such a plateau, the Web test is replaced by the Proctor penetrometer test.

The transition between the operating and non-operating states is preferably associated with a local minimum resistivity point on the curve (see point P ₂ in FIG. 2). In this embodiment, the transition time is defined as the time t ₃ that corresponds to the point P ₃ .

In some embodiments, implementation of the present invention, the method moves to position 14, in which the method identifies the start time of setting of the material. The setting start time is preferably associated with the onset of the most rapid rise in the resistivity curve (see point P ₃ in FIG. 2). In this embodiment, setting start time is defined as time t ₃ that corresponds to point P ₃ .

In some embodiments, implementation of the present invention, the method moves to position 15, in which the method identifies the end of setting of the material. The end of the setting is preferably associated with a local maximum resistivity (see point P ₄ in FIG. 2). In this embodiment, the setting end time is defined as time t ₄ , which corresponds to point P ₄ .

In some embodiments, the setting time can be defined as the average between a time t ₂ corresponding to a local minimum of resistivity (point P ₃ ) and a time t ₄ corresponding to a local maximum of resistivity (point P ₃ ). So, in these embodiments, the setting start time is (t ₂ + t ₄ ) / 2 and the setting end is t ₄ .

After determining the setting time, the setting period is defined as the period between the start time of setting and the end time of setting. When the material is concrete, each of the transitions corresponding to the above points P ₁ -P ₄ is preferably identified when the age of the concrete is less than 24 hours.

The present embodiments also provide for the identification of other transitions, such as, but not limited to, a transition from a gel state to a capillary-porous colloidal state, a transition from a capillary-porous colloidal state to a colloidal crystalline state, and a transition from a discontinuous crystalline state to a continuous crystalline state. These operations are shown together by block 16 in FIG. 1 and can be performed in any order known in the art. For example, part or all of the operations disclosed in US Pat. No. 7,225,682 can be applied. An example of the identification of these transitions is given in the Examples section below.

In some embodiments, implementation of the present invention, the method moves to position 17, which determines the compressive strength based on at least partially time dependence. This can be done in any order known in the art, such as, but not limited to, the order disclosed in US Pat. No. 7,225,682 or part thereof. A preferred procedure for determining compressive strength is described below.

The method ends at position 18.

An advantage of the present embodiments is that, unlike other published methods, the identification of various transitions is performed directly by the time dependence of the resistivity curve. For example, in the method described by Li et al. (Li et al.) Above, the points that are detected on the resistivity curve are only indirectly related (via a phenomenological linear relationship) to the setting time.

Reference is now made to FIG. 3, which is a schematic illustration of a measuring device 20 according to various illustrative embodiments of the present invention. The device 20 can be applied by the method described above to measure the electrical properties of the reactive material. The device 20 contains a container 22 for a reactive material and at least two electrodes 24. The electrodes 24 are used to create an electric field 26 in the reactive material and to monitor the resistance of the reactive material to the electric field 26. The creation of an electric field 26 can be carried out by connecting the electrode 24 with a voltage source 28 of the conductor 54. The resistance of the reactive material can be monitored by measuring a specific component (real part or imaginary part) ktric current passing through the electrode 24.

According to one preferred embodiment of the present invention, the device 20 further includes a contouring device 30 for contouring the electric field 26 essentially along a predetermined path 32 in the reactive material. The contouring of the electric field 26 along the circuit 32 ensures that the density of the current supplied by the electrode 24, in fact, is always constant, which allows to obtain reliable measurement results. Preferably, but not necessarily, contouring device 30 is a passive contouring device. For example, as shown in FIG. 3, the contouring device 30 may include a dielectric barrier 34 located between the first electrode 24a and the second electrode 24b. In some embodiments of the present invention, the size and shape of the partition 34 is chosen so that the electric field lines circumvent the partition 34 along the path 32. The preferred shape of the partition 34 is a plane having a diameter approximately equal to the diameter of the vessel 22 and a height approximately equal to 75% of the height of the vessel 22. For example, when the container 22 is a cylinder having a diameter of about 10 cm and a height of about 16 cm, the baffle 34 is a plane with dimensions of about 10 cm in width and approximately but 8 cm in height. You must understand that these values should not be construed as limiting.

It is also contemplated to use an active contouring device, such as an active contouring device, disclosed in US Pat. No. 7,225,682 above.

Reference is now made to FIG. 4, which is a schematic illustration of a system 40 suitable for determining a setting period of a reactive material, according to various illustrative embodiments of the present invention. The system 40 comprises a measuring unit 42 for continuously measuring the electrical properties of the material, as detailed above. Block 42 is preferably configured to measure electrical property by direct contact with the material. For example, block 42 may include a device 20 for creating an electric field between two electrodes along a sufficiently long contour in the material, as described in detail above.

The system 40 further includes a processing unit 44, which extracts a time dependence of the electrical property. Block 44 may be, for example, a special processor or a special computer. In various illustrative embodiments of the invention, block 44 is configured to determine based on a time relationship of setting time and / or setting time of setting material. Thus, the processing unit may comprise a setting time module 46, which is designed and configured to determine setting time and setting time, as described above in detail.

Block 44 may also identify one or more other transitions based on the aforementioned time dependence, such as, but not limited to, a transition between the first and second operating states, a transition between operational and non-operational states. Thus, the processing unit may comprise a transition identification module 48, which is designed and configured to detect a transition between the first and second operational states and / or a transition between the operational and non-operational states, as described in detail above. Module 48 may also be configured to identify one or more other transitions, for example, from a gel to a capillary-porous colloidal state, and / or from a capillary-porous colloidal state to a colloidal crystalline state, and / or from a discontinuous crystalline state to a continuous crystalline state .

In various illustrative embodiments, block 44 is also configured to determine the compressive strength of the material. So block 44 may contain a module for calculating the strength, which is designed and configured to calculate the compressive strength of the material, as described in detail below.

One specific feature of some embodiments of the present invention is the ability to control the hardening process of the reactive material at a stage where it is still possible to adjust the properties of the material depending on the needs of the particular application for which the reactive material is produced. After the chemically active material has passed the reversible stage, it will go into the irreversible solidification stages, at which the manufacturer’s control over the quality of the final product is very limited. It is known that at the irreversible stages of solidification, the compressive strength, S, as a function of time, t, has a logarithmic form:

$$S(t)=S_n\frac{\log t}{\log n},(\mathrm{one})$$

where S _n is the compressive strength of the material at t = n.

According to some embodiments of the present invention, the measurement of electrical property is started well in advance before the compressive strength of the reactive material exhibits a logarithmic time dependence. For concrete, for example, the preferred age of the mixture in which the measurement is performed is less than about 2 hours.

One of ordinary skill in the art will understand that monitoring the concrete hardening process at such an early stage is extremely beneficial, since at this stage the concrete manufacturer has enough time to adjust the manufacturing process depending on its needs before the mixture moves to the aforementioned irreversible hardening stages .

In some embodiments of the present invention, the temporal dependence of electrical resistivity is correlated with compressive strength to obtain a correlation function. The correlation function can be implemented in several ways. So, in some embodiments, the correlation function has an analytical form, in some embodiments, the correlation function is numerically (for example, tables), and in some embodiments, the correlation function has a graphical form (calibration curve).

The correlation function can be used to parameterize the logarithmic time dependence S (t), which characterizes the development of compressive strength at later stages of solidification. More specifically, denoting the correlation function as φ, we can calculate the value of S (t) using the following equation:

from which you can obtain the parameterization of Equation 1 by choosing the appropriate initial time, n, and calculating S _n = S (t = n). In other words, if φ is known, the compressive strength of a reactive material, almost always when the material has a liquid phase, can be calculated using the following equation:

Alternatively, the same function φ can be used to calculate the compressive strength of a material at any time. This can be done by determining the correlation function at the stage when the compressive strength of the reactive material already has a logarithmic time dependence. For example, several mechanical measurements of compressive strength can be performed when the material is older than 50 or greater than 100. The results of these measurements can be correlated (for example, using linear regression or another fitting method) with the results of electrical measurements made in accordance with some embodiments of the present invention. to get the correlation function S = φ (ρ). Such a correlation function can be used to determine strength at any time.

Thus, the present embodiments successfully provide a method suitable for controlling the compressive strength of a reactive material of any age (for example, at least a month, at least a year, at least five years, at least 10 years, at least 15 years, for example, 20 years or more).

As used herein, the term “approximately” refers to ± 10%.

The terms “comprises,” “comprising,” “includes,” “including,” “having,” and their derivatives mean “including, but not limited to.”

The term “consisting of” means “inclusive and limited by something.”

The term “consisting essentially of” means that the composition, method or structure may include additional ingredients, steps or parts, but only if such additional ingredients, steps and / or parts do not significantly change the basic and new characteristics of the claimed composition, method and / or structure.

The singular form used here includes references to the plural, unless the context clearly indicates otherwise. For example, the term “compound” or “at least one compound” may include a number of compounds, including mixtures thereof.

Throughout this application, various embodiments of the invention may be presented in a range format. You must understand that the indication in the format of the range is given only for convenience and brevity and should not be construed as an inflexible limitation of the scope of the invention. Accordingly, the indication of the range should be perceived as specifically revealing all possible sub-ranges, as well as individual numerical values in such a range. For example, an indication of a range from 1 to 6 should be perceived as specifically revealing sub-ranges from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and also individual numerical values in such a range, for example, 1, 2, 3, 4, 5 and 6. This applies regardless of the latitude of the range.

If a numerical range is indicated in this document, it means that it includes any number (fractional or integer) in that range. The phrases "in the range between" the first indicated number and the second indicated number and "in the range from" the first indicated number "to" the second indicated number are used interchangeably herein and mean including the first and second indicated numbers and all fractional and integer numbers between them.

You must understand that certain features of the invention, which are described for clarity in the context of individual embodiments, may also be presented in combination in one embodiment. Conversely, various features of the invention, which for brevity are described in the context of one embodiment, may also be presented separately or in any suitable combination or as suitable in any other described embodiment of the invention. Some features described in the context of various embodiments should not be construed as essential features of such embodiments, unless the particular embodiment works without such elements.

Various embodiments and aspects of the present invention, which are described above and are included in the claims, find experimental support in the following examples.

EXAMPLES

Reference is now made to the following examples, which, together with the above description, illustrate some embodiments of the invention in a non-limiting manner.

EXAMPLE 1

Determination of the setting period and transitions until the end of setting

Embodiments of the present invention were used to analyze concrete B-30 modified with the following additives: a moderator (0.002C) and a means for reducing the water content (0.015C) at W / C = 0.68 and a maximum coarse aggregate particle size of 14 mm. In this Example, the setting start time was defined as the time corresponding to the most rapid rise of the resistivity curve, and the setting end time was defined as the time corresponding to the local maximum of the resistivity curve. In addition, transitions that occurred prior to the setting time were also identified.

Resistivity measurements according to the present embodiments were made using the device shown in FIG. 3. For comparison, the following mechanical tests were also performed: cone draft, Web test, and Proctor penetrometer test. A 5-inch cone was used for cone draft and Web tests.

Resistivity measurements were essentially continuous. Mechanical tests were performed at a frequency of approximately 4 measurements per hour. The cone draft was performed in the first 3 hours, the Web test was performed when the bud was 3 to 10 hours old, and the Proctor penetrometer tests were performed when the bud was 10 to 20 hours old. Additionally, strength tests were performed at 24, 48, 72, 168 and 672 hours.

All samples for mechanical tests, as well as measurements of electrical resistivity, were made from one batch of concrete. Samples were stored under the same conditions throughout the experiment.

FIG. 5 shows the resistivity (pure squares) and strength (filled circles) as a function of time in hours for a period of 2-168 hours. The resistivity values are marked on the left ordinate in units of Ω · m, and the strength values are marked on the right ordinate in units of MPa. Data for a period of 168-672 hours are not shown. As a representative example, after 28 days (672 hours), the measured resistivity was 455 Ω · m and the strength was 35.5 MPa. The results in FIG. 5 demonstrate that there are two main stages of solidification: the first stage, in which the change in resistivity is moderate, and the second stage, in which the change in resistivity is more pronounced. As shown, the transition between stages occurs after approximately 24 hours.

As will be demonstrated below (see FIG.6B), in the first stage, the resistivity curve is nonmonotonic as a result of the joint development of chemical and structural transformations. At this stage, chemical processes initially dominate, and the resistivity decreases as a result of an increase in the concentration of positively charged ions. Later, when the concentration of the reaction products increases, the thickness of the layers of water decreases, and the mobility of the ions decreases, leading to stabilization and a subsequent increase in resistivity. At the beginning of the first stage, concrete is a viscoplastic material capable of thixotropic dilution, which makes it working (convenient for laying). Shortly before the start time of setting, concrete becomes less working or non-working. During the setting period, coagulation and subsequently initial crystallization structures are formed.

The second stage is the crystallization hardening of concrete. This stage is characterized by monotonic changes in resistivity. The temporal dependence of resistivity in the second stage is logarithmic.

FIGS. 6A and 6B show the results of mechanical tests (FIG. 6A) and the results of measurements of resistivity (FIG. 6B) made in accordance with some embodiments of the present invention in a time period of 24 hours. For clarity of explanation, all mechanical test results are shown in a single graph. In FIG. 6B, different symbols indicate different time intervals (the dark square is the time interval in which the cone draft test was performed, the gray square is the time interval in which the Web test was performed, and the triangles are the time interval in which the test was performed Proctor penetrometer test), but they all correspond to the same type of measurement (resistivity). Different intervals are separated by dashed lines in FIG.6A-B.

A comparison of FIG.6A and FIG.6B shows that changes in the structural-wet state at an early stage of concrete hardening can be identified directly by the electrical resistivity curve without further correlation.

For example, a significantly sharp slowdown in precipitation (from 17.5 cm to 4.5 cm) ends at t = 2.75 hours (FIG.6A). This transition is detected by the resistivity curve as the inflection point of the curve (marked by arrow 62). The subsequent decrease in resistivity to its minimum value at t = 10.0 hours (FIG.6B, arrow 64) corresponds to the change in consistency measured by the viscometer in a Web test (FIG.6A). After a short stabilization period, the electrical resistivity begins to increase (FIG.6B). This coincides with the start of the setting process, as seen in FIG. 5.

The start and end of setting, which were determined by the standard Proctor method (ASTM C-403), occurred at t = 15.75 hours and t = 19.8 hours, respectively. This time can be determined directly from the resistivity curve of the present embodiments. The setting start time is identified as a point marking the onset of the most rapid increase in resistivity. This attack was observed at t = 15.97 hours (FIG.6B, arrow 66). The end of setting is detected as the local maximum of the resistivity curve. This attack was observed at t = 19.52 hours (FIG.6B, arrow 68).

This experiment demonstrates that the time of convenient laying and setting of concrete mixture can be determined by continuous measurements of electrical resistivity or its representation during the first 24 hours of solidification. This may allow the builder to precisely select additives and the water content of the mixture to achieve the desired laying and setting time.

A correlation between the strength measured by standard strength tests and the electrical resistivity measured in accordance with some embodiments of the present invention during the first 500 hours is shown in FIG. 7. As shown, a linear correlation is observed. The linear regression order was used to determine the following relationship between the strength S and the resistivity ρ, at R ² according to Pearson 0.9841:

S (ρ) = 0.0924ρ-5.9559.

EXAMPLE 2

Setting the setting period using the middle variant of implementation

Embodiments of the present invention were used to determine setting periods of various concrete mixtures. In this example, the setting start time, time, was defined as the average between the time corresponding to the local minimum of resistivity and the time corresponding to the local maximum of resistivity. The setting end time was defined as the time corresponding to the local maximum of resistivity.

Tests of 12 concrete mixtures (1-12) were conducted. The following types of cement were used: CEM II 42.5N for mixtures 1-8, 11 and 12, and CEM II 52.5N for mixtures 9 and 10. The batch used for mixtures 1-6, 11 and 12 was different from the batch used for mixtures 7 and 8.

Mixtures included quarry sand (QS) and sea sand (SS) with different densities and ratios. Some mixtures (1-4) included additional aggregates, which were measured on sieves with mesh sizes of 19 mm, 14 mm, 5 mm, 9 mm, and 2.36 mm. The designation X / Y below in relation to the aggregate means that the aggregate passes through a sieve X, but does not pass through a sieve Y. That is, the particle size of the aggregate is greater than Y and less than X.

Mix 1 was tested with the full composition of the concrete mix. Mixture 2 was tested according to ASTM C-403: all particles over 3/4 inch from the mixture were removed. Mixtures 11 and 12 were modified with Redycret-5 (3.96 kg / m ³ ) and Hostopur (0.014 kg / m ³ ) additives.

Concrete mixtures were kept either in an oven at a temperature of 30 ° C (for mixtures 1, 2, 4, 6, 8, 10, and 12) or at room temperature 20 ° C (for mixtures 3, 5, 7, 9, and 11).

Setting time was determined using a resistivity curve in accordance with some embodiments of the present invention and using a Proctor penetrometer test.

The results are summarized in Table 1. In this table, W / C is the amount of cement (C) and water (W), Pr is the result of the Proctor penetrometer test, and ρ is the result of the resistivity curve.

Table 1 shows that the procedure of the present embodiments is able to determine the setting period with high reliability. The correlations between the setting times obtained during testing with a Proctor penetrometer and using the resistivity curve are as follows: t _Pr = 0.916t _ρ +18.732 with a Pearson value of R ² = 0.9026 for setting time, and t _Pr = 1.0478t _ρ -6.9204 at a Pearson value of R ² = 0.9765 for the setting time, where t _Pr is the setting time measured when tested by the Proctor Penetrometer, and t _ρ is the setting time measured in accordance with these embodiments.

EXAMPLE 3

Determination of other transitions and predicted strengths

Electrical resistivity measurements were performed on various cement samples according to an embodiment of the present invention. The measurement results were continuously obtained when the age of the mixture was less than 48 hours.

FIG. 8 shows the electrical resistivity, ρ, in units of Ω · m as a function of time, t, in hours, measured for a standard cement-sand mixture (according to EC standard EN-196, Part 1: “Methods for testing cement. Determination of strength ”). The mixture was prepared using cement type CEM-1, strength class 42.5 N (EC standard EN-197, Part 1: “Composition, specification and conformity criteria for conventional cements”).

In accordance with some embodiments of the present invention, a time dependence of the resistivity is obtained and functional transitions of the time dependence are identified.

As used herein, the term “functional transition” refers to any identifiable mathematical transition of a function, including without limitation the transition of a given function (for example, a change in slope, a transition from increase to decrease or vice versa) and a transition from one characteristic functional behavior to another (for example , transition from linear to non-linear behavior or transition from the first non-linear behavior to the second, non-first, non-linear behavior).

Functional transitions can be identified, for example, by calculating the derivative of the time dependence and finding its zeros. An average person skilled in the art will understand that any transition of a function is characterized by zero of one of its derivatives. For example, the transition from increase to decrease, or vice versa, is characterized by the zero of the first derivative, the transition from the convex region to the concave region, or vice versa (the inflection points of the curve), is characterized by the zero of the second derivative, etc. According to one preferred embodiment of the present invention, any derivative of the time dependence can be used. Typically, functional transitions are preferably characterized by a sign reversal of the nth derivative of the time dependence, where n is a positive integer.

Additionally or alternatively, functional transitions can be identified by observing deviations in the temporal dependence of smoothness. In this embodiment, the functional transitions can be identified with or without calculation of the derivatives of the time dependence. For example, deviations from smoothness can be identified manually or by comparing the time dependence with a known smooth function. This embodiment has been applied in this Example.

As shown in FIG. 8, four structural states of the mixture were identified by checking the time dependence of the resistivity, ρ (t), and identifying functional transitions. These conditions are the gel state (indicated in this example and FIG. 8 as state I), the capillary-porous colloidal state (indicated in this example and FIG. 8 as state II), the colloidal crystalline state (indicated in this example and in FIG. 8 as state III) and a continuous crystalline state (indicated in this example and in FIG. 8 as state IV).

Transitions between states were observed at the following values of t: 4 (transition from state I to state II), 15 (transition from state II to state III) and 37 (transition from state III to state IV). An additional functional transition in which the increase in resistivity becomes more moderate was observed in the time interval between about 20 hours and about 25 hours. This transition characterizes the formation of three-dimensional cells before the growth of a continuous crystalline framework in which the electrical resistivity is stabilized, as described in detail above.

FIG. 9 shows a comparison between the energy of bound water in units of J / s and the electrical resistivity for a standard cement-sand mixture. As shown, electrical resistivity is more sensitive to transitions between structural changes in the mixture.

FIG. 10 and FIG. 11 show the time dependence of electrical resistivity, ρ (t), in units of Ω · m, for fine-grained concrete mixtures with water / cement ratios of 0.60, 0.67 and 0.75. The mixtures were prepared using fine-grained dolomite aggregates purchased in the quarry of Kohav-Ha-Shahar, Israel (FIG. 10) and in the quarry of Shfaram, Israel (FIG. 11), with the composition cement: sand: aggregates 1: 2: 3. As shown in FIGS. 10-11, similar functional transitions were observed during the first 48 hours of solidification, regardless of the water / cement ratio or type of aggregates. The functional transitions shown in FIGS. 10-11 are consistent with the functional transitions of a standard cement-sand mixture with FIG. 8 and FIG. 9. In addition, fine-grained concrete mixtures show a smaller increase in ρ (t), which characterizes the formation of three-dimensional cells in the third structural state of the mixture. Like this cement-sand mixture, a slowdown was observed between approximately t = 20 hours and t = 25 hours.

FIGS. 12A-C and FIGS. 13A-C show comparisons between the time dependences of the compressive strength, R (t), in units of MPa, and the electrical resistivity, ρ (t), in units of Ω · m, of fine-grained concrete mixtures with FIG.10 and 11, respectively. The water-cement ratios of 0.60 (FIG. 12A and 13A), 0.67 (FIG. 12B and 13B) and 0.75 (FIG. 12C and 13C) are shown. As shown in FIGS. 12A-13C, the R (t) and ρ (t) curves show similar behavior, in particular, a slowdown observed at approximately t = 20 hours and t = 25 hours. Thus, in accordance with preferred embodiments of the present invention, the functional transitions ρ (t) can be used to determine the hardening state of the material.

FIG. 14 and FIG. 15 show a graphical representation of the correlation function, φ, determined by correlation between the time dependences of the electrical resistance, ρ, and compressive strength, R, in the early stages of solidification. FIG. 14 corresponds to a fine-grained concrete mixture with FIG. 10, and FIG. 14 corresponds to a fine-grained concrete mixture with FIG. 11. φ (ρ) can thus be used to determine the compressive strength at various values of electrical resistivity. For example, φ (ρ) can be used to determine the compressive strength at, say, t = 50 hours, at which, as is known, the compressive strength has a logarithmic dependence.

Although the invention has been described in connection with its specific embodiments, it is obvious that many alternatives, modifications and changes will be apparent to those skilled in the art. Accordingly, it is intended to cover all such alternatives, modifications, and changes that fall within the spirit and broad scope of the appended claims.

All publications, patents and patent applications referred to in the present description, are incorporated into it in full by reference to the same extent as if each individual publication, patent or patent application was specifically and individually indicated as incorporated herein by reference . In addition, the citation or identification of any link in this application should not be construed as an assumption that such a link is contrasted as the prior art for the present invention. Section headings should not be construed as necessarily limiting.

Claims (28)

1. A method for determining the setting period of a reactive material, including:
continuous measurement of the electrical property of the material to obtain a time dependence of said property, wherein said property is resistivity or its representation; and
the use of said time dependence for determining the start time of setting and the end time of setting, wherein said start time of setting is defined as the time of the most rapid rise of said resistivity and said end time of setting is defined as the local maximum time of said specific resistance;
thereby determining the setting time of the material. 2. The method according to claim 1, further comprising using the aforementioned time dependence to detect a transition between the working state of the material and the non-working state of the material. 3. The method according to any one of claims 1 and 2, further comprising using the said time dependence to detect a transition between the first working state of the material and the second working state of the material, said transition being equivalent to a sharp deceleration of precipitation that would occur if the material were subjected sediment test. 4. The method according to any one of claims 1 and 2, further comprising using the said time dependence to detect a transition between the gel state of the material and the capillary-porous colloidal state of the material. 5. The method according to any one of claims 1 and 2, further comprising using the said time dependence to detect a transition between the capillary-porous colloidal state of the material and the colloidal-crystalline state of the material. 6. The method according to any one of claims 1 and 2, further comprising using the said time dependence to detect a transition between the discontinuous crystalline state of the material and the continuous crystalline state of the material. 7. The method according to any one of claims 1 and 2, further comprising using the said time dependence to determine the compressive strength of the material. 8. The method according to claim 2, characterized in that said transition between said working and said inoperative states is defined as the local minimum time of said resistivity. 9. The method according to claim 8, characterized in that said local minimum is detected using a time-movement window having a width of about 2 hours. 10. The method according to claim 2, characterized in that said transition between said working and said non-working states is detected on a linear scale of said time dependence. 11. A method according to any one of claims 1 and 2, characterized in that each of said setting time and said setting time is detected on a linear scale of said time dependence. 12. The method according to any one of claims 1 and 2, characterized in that each of the aforementioned occurrences of said most rapid rise of said resistivity and said local maximum of said resistivity is detected using a time-movement window having a width of about 2 hours. 13. The method according to any one of claims 1 and 2, characterized in that the said electrical property is measured by direct contact with the material. 14. The method according to any one of claims 1 and 2, characterized in that the said electrical property is measured in a constant volume. 15. A method according to any one of claims 1 and 2, characterized in that said electrical property is measured by creating an electric field between the first electrode and the second electrode along a sufficiently long contour in said material. 16. The method according to clause 15, wherein said circuit has a length that is at least two times the distance between the said electrodes. 17. A system for determining the setting period of a reactive material, comprising:
a measuring unit for continuously measuring the electrical property of a material in order to obtain a time dependence of said property, wherein said property is resistivity or its representation; and
a processing unit for determining, based on said time dependence of the setting time and setting time, said setting time is defined as the time of the most rapid rise in said specific resistance and said setting time is defined as the local maximum time of said specific resistance. 18. The system according to 17, characterized in that the said processing unit is configured to detect a transition between the working state of the material and the inoperative state of the material based on the aforementioned time dependence. 19. The system according to any one of paragraphs.17 and 18, characterized in that said processing unit is configured to detect a transition between a first working state of a material and a second working state of a material based on said time dependence, said transition being equivalent to a sharp deceleration of precipitation that would be observed if the material were subjected to a sludge test. 20. The system of claim 19, wherein said transition between said first and said second operating states is defined as a time corresponding to an inflection point of a curve of said resistivity. 21. The system according to claim 19, characterized in that said transition between said first and said second operating states is detected on a linear scale of said time dependence. 22. The system according to claim 20, characterized in that the said inflection point of the curve is detected using a window of the movement of time having a width of approximately 2 hours. 23. The system according to any one of paragraphs.17 and 18, characterized in that said processing unit is configured to detect a transition between the gel state of the material and the capillary-porous colloidal state of the material based on said time dependence. 24. The system according to any one of paragraphs.17 and 18, characterized in that said processing unit is configured to detect a transition between the capillary-porous colloidal state of the material and the colloidal-crystalline state of the material based on said time dependence. 25. The system according to any one of paragraphs.17 and 18, characterized in that said processing unit is configured to detect a transition between a discontinuous crystalline state of a material and a continuous crystalline state of a material based on said time dependence. 26. The system according to any one of paragraphs.17 and 18, characterized in that said processing unit is configured to determine the compressive strength of the material based on said time dependence. 27. The system according to any one of paragraphs.17 and 18, characterized in that the said electrical property is measured in a constant volume. 28. The system according to any one of paragraphs.17 and 18, characterized in that said electrical property is measured by creating an electric field between the first electrode and the second electrode along the contour in said material, said contour having a length greater than the distance between said electrodes.

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