KR20200056305A - Cement composite composition capable of self stress sensing - Google Patents

Abstract

According to the present invention, a self-stress sensible cement composite material composition includes cement, silica fume, silica powder, a conductive material, a high performance water reducing agent, and water, and the conductive material can include steel slag and steel fibers.

Description

CEMENT COMPOSITE COMPOSITION CAPABLE OF SELF STRESS SENSING}

The present invention relates to a cement composite material composition capable of self-stress sensing, and more specifically, the cement composite material itself comprises steel slag and steel fibers capable of sensing or measuring a change in self-stress capable of sensing a load state. It relates to a cement composite material composition.

The “concrete” structures manufactured through “composite materials” such as cement and “aggregate” are the most widely used structures in urban buildings and social infrastructure constructions. The demands for systems that can be detected or predicted in real time or in advance to reduce the risk of “collapse” are increasing.

In the existing concrete structure detection damage, various strain or displacement measuring devices are additionally installed to measure real time, and monitoring system and safety diagnosis method to measure damage and health.

In addition, various electrochemical methods can be applied. Among them, the non-destructive corrosion diagnosis method, which investigates the corrosion degree of reinforcing bars by measuring the specific resistance by applying a current to a concrete structure, is a typical example.

Patent Publication No. 2011-0010853 discloses a non-destructive corrosion diagnosis system capable of directly evaluating the electrical resistivity of a reinforced concrete structure and evaluating its corrosion environment and its condition, and has two current electrodes outside the concrete surface directly above the reinforcement. And, by installing two voltage electrodes on the inside at the same intervals in parallel to the longitudinal direction of the reinforcing bar, measure the response voltage generated by the current source, and estimate the surface resistivity of the reinforcing bar representing the corrosion environment of the reinforcing bar. The technical feature is to conduct regular inspections and regular monitoring on durability.

However, this method of permanently monitoring the corrosion and durability of the concrete structure has a limit to measure only the corrosion degree of the reinforcing bar, which is an electrically conductive material formed inside the concrete, and provides information on damage such as cracks in the entire concrete structure. There is a problem that cannot be.

Current monitoring systems that separately attach or embed a sensor that measures a separate strain or displacement to a structure cannot be used continuously for the entire life of the structure due to the very short sensor's endurance life compared to the structure's life. There is this. In addition, in the case of a monitoring system with a sensor, it is somewhat difficult to judge the integrity of the entire structure with a response only at the sensor position.

In addition, in Patent Publication No. 2005-0018744, cement paste or mortar polyethylene (PE) fiber or polyvinyl alcohol (PVA) fiber or polypropylene (PP) fiber as micro fiber, steel fiber (SF) or steel cord (SC) Or a high toughness cement composite prepared by using polyvinyl alcohol (PAV) fiber as a macro fiber has been proposed. The high toughness cement composite has a strain hardening property and multiple crack properties under flexural and tensile loads, resulting in high bending and Advantages of not only exerting tensile strength, deforming ability, and energy absorption ability, but also controlling the crack width, can suppress the penetration of various deterioration factors.

Recently, the results of detecting cracks and damages by incorporating carbon black with high conductivity into high toughness cement composites using polyvinyl alcohol fibers have been reported, but cracks occur due to the low electrical conductivity of polyvinyl alcohol fibers. Electrical resistance rather increased. Therefore, there is a need for an electrical resistance measuring device capable of measuring very low electrical conductivity.

To detect damage to existing structures, self-sensing cement-based composites reinforced with various conductive materials (Carbon fiber, CNT, Carbon black, Nickel powder, etc.) have deformation detection characteristics only within the pre-elastic section before cracking, cracking There is a problem of losing its detection ability after occurrence.

To compensate for these shortcomings, the electrical conductivity of the strain-hardening steel-fiber-reinforced concrete (SH-SFRC) incorporating steel fibers or the cement-based composite itself incorporating steel fibers and carbon black is increased, and at the same time, the detection ability after cracking occurs. It is known to be maintained.

As described above, most of the prior art suggests a self-sensing cement composite material having improved electromechanical sensitivity by using a carbon-based nano material having high electrical conductivity in a cement composite material.

However, it is inefficient to use expensive carbon-based nanomaterials in economic terms. In addition, carbon-based nanomaterials having a high cohesive force have difficulty in homogeneous dispersion due to their properties and reduce the mechanical performance of the cement composite material.

Therefore, it is necessary to develop a self-stress sensing cement composite material that can be implemented at a relatively low cost from an economical aspect, homogeneous dispersion, and does not degrade the mechanical performance of the cement composite material.

In order to solve the above problems, the applicant has proposed the present invention.

The present invention has been proposed to solve the above problems, cement using a steel slag fine aggregate processed with a sand particle size having a high iron content and having electrical conductivity and steel fibers having high tensile strength and electrical conductivity as a conductive material. It solves the problems of the prior art by reinforcing the composite material, and provides a cement composite material composition capable of self-stress sensing with maximized self-stress sensing capability.

The present invention provides a cement composite material composition capable of self-stress sensing capable of improving self-stress sensing ability using a low-cost conductive material.

The present invention provides a cement composite material composition capable of self-stress sensing capable of easily securing homogeneous dispersion.

The present invention provides a cement composite material composition capable of self-stress sensing capable of improving the self-capacity sensing ability without deteriorating the mechanical performance of the cement composite material.

The present invention provides a cement composite material composition capable of self-stress sensing using a material having a crack control performance secured from tensile stress.

The cement composite material composition capable of self-stress sensing according to the present invention for achieving the above-described problems includes cement, silica fume, silica powder, conductive material, high-performance water reducing agent, and water, and the conductive material includes steel slag and Steel fibers may be included.

Based on 100 parts by weight of the cement, it may include 15 parts by weight of the silica fume, 25 parts by weight of the silica powder, 50 to 100 parts by weight of the steelmaking slag, 5.1 parts by weight of the high performance water reducing agent and 20 parts by weight of the water.

The steel slag may be included in 100 parts by weight based on 100 parts by weight of the cement.

The cement may further include 50 parts by weight of sand based on 100 parts by weight, and the steel slag may be included as 50 parts by weight.

The steel slag may be provided with a steel slag fine aggregate formed of particles having a diameter of 0.39 mm or less.

The steel fiber may be included in 2% of the volume of the test body formed of the cement composite material composition.

The steel slag and the steel fiber may contact each other to form an electrical network, and when the compressive load is applied or the stress changes, the steel slag or the steel fiber intervening in the electrical network may increase.

The steel fiber may include a plurality of short smooth steel fibers.

The cement composite material composition capable of self-stress sensing according to the present invention can lower cost and increase productivity because it uses low-cost steel slag or steel slag fine aggregate having electrical conductivity.

The cement composite material composition capable of self-stress sensing according to the present invention includes silica fume and can ensure a homogeneous dispersion because the steelmaking slag is formed in the size of sand particles.

The cement composite material composition capable of self-stress sensing according to the present invention can prevent deterioration of mechanical performance of the cement composite material and ensure crack control performance from tensile stress.

1 is a view for explaining the principle of electrical resistance change of the cement composite material capable of self-stress sensing according to the present invention.
2 is a photograph of steel slag and steel fibers incorporated into a cement composite material composition capable of self-stress sensing according to the present invention.
3 is a view for explaining an electrical network change when a compressive load is applied to a cement composite material capable of self-stress sensing according to the present invention.
4 is a photograph of a test specimen of a cement composite material composition capable of self-stress sensing according to the present invention.
5 to 9 are graphs showing the results of experiments on the electro-mechanical performance of a self-stressing capable cement composite material composition according to the present invention.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited or limited by the embodiments. The same reference numerals in each drawing denote the same members.

1 is a view for explaining the principle of electrical resistance change of the cement composite material capable of self-stress sensing according to the present invention, FIG. 2 is a steel slag and steel fibers incorporated into the cement composite material composition capable of self-stress sensing according to the present invention Photo, FIG. 3 is a view for explaining an electrical network change when a compressive load is applied to a self-stress-sensitive cement composite material according to the present invention, and FIG. 4 is a self-stress-sensitive cement composite material composition according to the present invention Test body photographs, FIGS. 5 to 9 are graphs showing the results of experiments of electro-mechanical performance of a cement composite material composition capable of self-stress sensing according to the present invention.

Referring to FIG. 1, a cement composite material composition capable of self-stress sensing according to the present invention (100, hereinafter referred to as a 'cement composite material composition') includes cement, silica fume, and silica powder powder), conductive materials, high performance superplasticizers, and water.

Forming a concrete structure using the cement composite material composition 100 having the composition as described above, forming an electrode capable of flowing electricity to the concrete structure, and supplying current to the electrode to change the specific resistance of the concrete structure over time By measuring the self-sensing of the stress of the concrete structure comprising the cement composite material composition according to the present invention (self-sensing).

Cement, silica fume, silica powder, high performance water reducing agent and water contained or included in the cement composite material composition 100 according to the present invention are generally used as civil engineering materials or construction materials, silica fume, silica powder, high performance water reducing agent and If it is water, it is not particularly limited and can be used. However, the content of cement, silica fume, silica powder, high performance water reducing agent and water can be used in a desired amount by using the cement composite material composition according to the present invention, depending on the structure or structure to be constructed, construction time, construction method, construction period, etc. Can be.

Here, the conductive material included in the cement composite material composition 100 according to the present invention may include steel slag (Steel slag, 120) and steel fiber (Steel fiber, 110).

The steel slag 120 is a by-product of the steel industry and has high iron content and electrical conductivity. The steel slag 120 may be formed in the shape or size of sand particles. The steel slag 120 processed to a size of sand is referred to as a steel slag aggregate (SSA). The cement composite material composition 100 according to the present invention may contain steelmaking slag or steelmaking slag fine aggregate (SSA). Hereinafter, "steel slag" is a concept including "steel slag fine aggregate (SSA)".

As shown in FIG. 1, it is preferable that the steel slag 120 has electrical conductivity and is processed to a sand particle size of 0.39 mm or less in diameter.

As shown in (a) to (c) of FIG. 2, the cement composite material composition 100 according to the present invention does not use steelmaking slag powder, but can be used in combination with steelmaking slag made of sand particle size. have.

The steel slag 120 is used in the size (particle size) is about the size of the sand particles, it is preferable to be used alone as a steel slag without mixing with other fine aggregates. That is, the steel slag 120 processed to the size of sand particles is incorporated by replacing sand used in the existing cement composite material.

The steel slag 120 may include quicklime (CaO), iron trioxide (Fe ₂ O ₃ ), water-soluble silicon (SiO ₃ ), alumina (Al ₂ O ₃ ), magnesia (MgO), and the like. The content of each component is shown in the following [Table 1].

Meanwhile, as illustrated in (d) of FIG. 2, the steel fiber 110 may include a plurality of short smooth steel fibers. That is, the steel fiber 110 may be used by mixing a plurality of short short fibers.

The cement composite material composition 100 according to the present invention has a short length, excellent tensile strength, and excellent electrical conductivity, so that the steel fiber 110 is incorporated, thereby evaluating the electro-mechanical performance of the cement composite material, thereby providing excellent self-stress change detection capability. Cement composite materials can be obtained.

The steel fiber 110 is preferably formed to a length suitable for homogeneous dispersion in the structure 101 of the cement composite material composition 100 according to the present invention.

In addition, the steel slag 120 can be homogeneously dispersed in the cement composite material composition 100 according to the present invention because it uses a sand particle size.

Here, homogeneous dispersion of the steel slag 120 and the steel fibers 110 may be possible even by the silica fume. By containing less amount of silica fume than the steel slag 120, the steel slag 120 or the steel fiber 110 may be prevented from agglomeration, and the steel slag or steel fiber may be evenly dispersed within the cement composite material composition 100.

On the other hand, as shown in Figures 1 and 3, the size of the steel slag 120 is preferably larger than the diameter or thickness of the steel fiber 110. The steel slag 120 and the steel fiber 110 may be uniformly dispersed in the cement composite material composition 100 or cement paste.

Cement, silica fume, silica powder, conductive material, high performance superplasticizer and water included in the cement composite material composition 100 according to the present invention are as follows. It is preferable to have the optimum mixing ratio of [Table 2]. Here, the conductive materials are steel slag (SSA) and steel fibers (Fiber).

Table 2 below shows the optimum mixing ratio of the cement composite material composition according to the present invention.

In order to find the optimal blending ratio as shown in [Table 2], the present applicant evaluates the electro-mechanical performance of the cement composite material composition according to the conductive material, and the electro-mechanical performance of the cement composite material composition according to the steel slag size and the amount of conductive material incorporation. Evaluation experiments were conducted. The experiment will be described later.

Since the cement composite material composition 100 according to the present invention includes both the steel slag 120 and the steel fiber 110 as a conductive material, it may have excellent self-stress sensing capability.

3 (a) is a view showing a case where a compressive load (P) is applied to the cement composite material according to the present invention, and FIG. 3 (b) is cement when a compressive load (P) is applied as in (a) This diagram shows the change in the electrical network occurring inside the composite material.

First, referring to FIG. 3 (a), the steel slag 120 and the steel fibers 110 included in the cement composite material composition 100 according to the present invention may be in contact with or in contact with each other or may be separated from each other. . Among them, the steel slag 120a, 120b and steel fibers 110a, 110b that are in contact with or in contact with each other may form an electric network (EN). That is, current may flow through the steel slag 120a, 120b and the steel fibers 110a, 110b that are in contact with or in contact with each other.

In the case of Figure 3 (a), two steel fibers (110a, 110b) and two steel slags (120a, 120b) form one electrical network (EN).

As such, the cement composite material composition 100 according to the present invention may include steel slag 120 and steel fibers 110 that form an electrical network when contacted with each other.

In the state of Fig. 3 (a), that is, the two steel fibers (110a, 110b) are in contact with each other and the two steel fibers (110a, 110b), respectively, in the state of steelmaking slag (120a, 120b) in contact with each other, the compression load When (P) is applied, the state of FIG. 3 (b) is changed.

When a compressive load (P) is applied to the structure 101 made of the cement composite material composition 100 according to the present invention, a stress change occurs in the cement composite material composition 100, and accordingly, within the cement composite material composition 100 The steel slag 120 or the steel fiber 110 may move or change position.

As shown in FIG. 3 (b), the steel slag 120 or the steel fibers that contact or abut each other by the stress change (Δ) generated in the self-stress sensing cement composite material composition 100 by the applied compressive load (P) ( 110).

Referring to Figure 3 (b), due to the stress change (Δ) by the compressive load (P), the new steel between the steel slag (120a, 120b) in contact with each of the two steel fibers (110a, 110b) in contact with each other The slag 120c is positioned to contact the two steelmaking slags 120a, 120b simultaneously. In addition, the steel slag (120e, 120d) is in contact with each of the two steel fibers (110a, 110b), respectively. In addition to this, the new steel fiber 110c and another steel slag 120f are also electrically connected to the two existing steel fibers 110a and 110b. Accordingly, in the case of FIG. 3 (b), three steel fibers 110a, 110b, and 110c and six steel slags 120a to 120f form one electrical network EN.

In this way, the steel slag 120 and the steel fiber 110 come into contact with each other to form an electrical network EN, and when a compressive load is applied or a stress is changed, the steel slag 120 or steel fiber 110 intervening in the electrical network Can increase. That is, when the stress changes, the number of steel slag 120 or steel fibers 110 participating in the same electrical network may increase.

As described above, the cement composite material composition 100 according to the present invention is capable of self-sensing the stress change from the electrical network that is enlarged when the stress changes due to the evenly distributed multiple steel slag 120 and the steel fiber 110. Can improve the detection ability.

On the other hand, as described above, the present applicant, in order to find the optimum blending ratio of the cement composite material composition shown in [Table 2], electro-dynamic performance evaluation of the cement composite material composition according to the conductive material, steel slag size and conductive material An electro-dynamic performance evaluation experiment of the cement composite material composition according to the amount of mixing was conducted. Hereinafter, the experimental process and results will be described.

1) Evaluation of the electro-mechanical performance of the cement composite material composition according to the conductive material

Applicants, the cement composite material composition according to the present invention is reinforced with steel slag and steel fibers, and excellent electrical conductivity and multi-walled carbon nanotubes (MWCNT) excellent in electro-mechanical performance in the elastic region The electro-mechanical performance with the reinforced cement composite material was compared and evaluated.

To this end, (1) matrix (MF) using 2 vol.% Of steel fibers, (2) matrix (MFMW) using 0.5% multi-walled carbon nanotubes (MWCNT) and 2 vol.% Of steel fibers, (3) only steelmaking slag was used. Matrix (MS), (4) Steel matrix slag and 2 vol.% Of steel fibers (MSF) were used to construct a total of four matrices. The components, compressive strength and conductive material properties of the four matrices used are shown in [Table 3] and [Table 4], respectively.

In [Table 3], Defoamer defoamer and fc denote compressive strength.

[Table 4] shows the diameter, length, tensile strength and modulus of elasticity of the conductive materials such as steel fiber, steel slag (SSA), and multi-walled carbon nanotubes (MWCNT).

* Preparation of specimen

For the electro-mechanical performance comparison experiment, test specimens for the four matrices of [Table 3] were prepared.

The test specimen used in the electro-mechanical experiment was a cube-shaped compression specimen having a width X length X height of 50X50X50 mm, and an electrode for investigating the electro-mechanical response, as shown in FIG. 4, using a copper wire mesh as a buried electrode. Used. The buried electrodes were buried inside the specimen at 20 mm intervals.

A copper wire mesh electrode is illustrated in FIG. 4 (a), and a test body in which the copper wire mesh electrode is embedded is illustrated in FIG. 4 (b).

In the case of cement composite material (MSF) using steel slag and steel fiber, the formulation was dry blended with cement and admixture and steel slag excluding water and water reducing agent (SP, [Table 3]). In addition, water was divided into four times to prevent fluidity and material separation, and water-reducing agent (SP) was added in small portions according to the formulation, and steel fibers were mixed. The thus-prepared specimens were cured in 90 ± 2 ^o C high temperature water for 3 days.

The multi-walled carbon nanotube (MWCNT) -reinforced cement composite material (MFMW) is diluted in a multi-walled carbon nanotube with a water reducing agent (SP) and added to the blended water, and an amplitude of 50% is used using an ultrasonic sonicator. After dispersing for 2 hours under grinding conditions of frequency 20s, it was used for compounding. The order of mixing was cement, silica sand (sand), and silica powder was added to dry mix (A1) for 10 minutes. After dry blending, A1 was removed, and the prepared multi-walled carbon nanotubes were combined with silica fume for 5 minutes (A2). After the A2 compounding was completed, A1, which had been previously blended, was introduced into A2 to perform the blending for 5 minutes. Subsequently, the remaining amount of water and a water reducing agent (SP) were added to mix for 10 minutes, and then a defoamer was added and further mixed for 5 minutes to prepare a test body. After curing, the test specimen was naturally dried for 24 hours, and then an experiment was performed.

* Experimental method

For the electro-mechanical response investigation, an AC impedance analyzer (not shown) was used as the electrical resistivity measurement equipment, and the measurement was performed through a 2-probe resistance measurement method.

The measurement condition of the AC impedance analyzer used for the measurement was to measure the impedance change by sweeping the frequency at 10 steps / decade in the frequency range of 1 Hz to 1 MHz. The mechanical conditions were measured using a universal test machine (UTM) with a capacity of 300 ton to measure the change in electrical resistivity according to the compressive load size (20,40,60,80,100 MPa) through a load maintenance test method.

* Experiment result

The impedance measured according to the load condition through the AC impedance analyzer is plotted through the Nyquist diagram, and the x-axis is the real part impedance value (Z ') and the y-axis is the imaginary part impedance value (Z' '). It was represented as 5. 5 is an experimental result graph showing the behavior of impedance change for each of four matrices according to the compressive load magnitude (20, 40, 60, 80, 100 MPa) applied to the test body. 6 is a graph of experimental results showing the change in impedance of a cement composite material according to the size of a compressive load applied to a test body.

At this time, by using the real part impedance value at the natural frequency point for each test object as the electrical resistance (Rcusp), the electrical resistivity (ρ), a material characteristic not affected by the test object size, was calculated as shown in [Equation 1].

In [Equation 1], A is the area of the test body, and L is the length of the test body.

For analysis, based on the electrical resistivity (ρ ₂₀ ) under a compressive load of size 20 MPa, the ratio of electrical resistivity (ρ _x ) up to the electrical resistivity (ρ _x ) for each load state is as follows. Equation 2] is calculated and shown in FIG. 7 and [Table 5].

[Table 5] shows the rate of change of the electrical resistivity of the cement composite material according to the size of the compressive load, and FIG. 7 is a graph of experimental results showing the change of the electrical resistivity of the cement composite material according to the size of the compressive load.

As shown in FIG. 7 and [Table 5], it can be seen that all the test specimens of the four matrices exhibit a behavior in which the electrical resistivity decreases as the compressive load increases. At this time, the matrix (MSF) using a combination of steel slag and steel fiber had a size of 100 MPa, and the electrical resistivity change rate (FCR) was 15.1% at the compressive load, showing the highest electrical resistivity change rate compared to the matrix using other electrically conductive materials, The electrical resistivity change rate of 12.3% for the steel fiber-only matrix (MF), 9.8% for the multi-walled carbon nanotube and the steel fiber (MFMW), and 9.6% for the steel-slag-only matrix (MS) Looked.

Therefore, it can be seen from the results of FIG. 7 and [Table 5] that the matrix (MSF) using a combination of steel slag and steel fiber is most suitable as a cement composite material capable of self-stress sensing.

2) Evaluation of electro-mechanical performance of cement composite material according to the particle size of steel slag and the amount of conductive material incorporated

Applicants to derive the optimum mixing ratio of the cement composite material composition capable of self-stress sensing for the matrix (MSF) in which steel slag and steel fibers showing the best electro-mechanical behavior in FIGS. 7 and 5 are used together In order to evaluate the electro-mechanical performance of the cement composite material according to the particle size of the steelmaking slag and the mixing amount of the conductive material, a total of 8 matrices were constructed.

The eight matrices are:

(1) Matrix (F2S0) using sand (silica sand) 100% by weight of cement and 2 vol.% Of steel fibers: 100 parts by weight of sand based on 100 parts by weight of cement, and 2% of the volume of steel fibers Matrix

(2) Matrix with steel slag (diameter ≤ Ø 0.39 mm) using 100% by weight of cement and 2 vol.% Of steel fiber (F2S1-0.39): 100 parts by weight of steel slag with a diameter of 0.39 mm or less based on 100 parts by weight of cement The steel fiber is a matrix containing 2% of the volume of the specimen

(3) Matrix with steel slag (1-2 mm in diameter) using 100% of cement weight and 2 vol.% Of steel fiber (F2S1-2): 100 weight of steel slag with a diameter of 1 to 2 mm based on 100 parts by weight of cement The matrix is included, and the steel fiber is contained in 2% of the volume of the specimen.

(4) Steel slag (2-5 mm in diameter) Matrix using 100% by weight of cement and 2 vol.% Of steel fiber (F2S1-5): 100 parts by weight of steel slag with a diameter of 2 to 5 mm based on 100 parts by weight of cement Included, steel fibers are contained in 2% of the sample volume matrix

(5) Steel slag (diameter ≤ Ø 0.39 mm) and sand each 50% by weight of cement, and 2 vol.% Of steel fibers (F2S0.5-0.39): diameter of 0.39 mm or less based on 100 parts by weight of cement A matrix containing 50 parts by weight of steel slag and 50 parts by weight of sand, and steel fibers containing 2% of the volume of the test sample

(6) Steel slag (diameter ≤ Ø 0.39 mm) Matrix using 150% of cement weight and 2 vol.% Of steel fiber (F2S1.5-0.39): 150 parts by weight of steel slag with a diameter of 0.39 mm or less based on 100 parts by weight of cement Included, steel fibers are contained in 2% of the sample volume matrix

(7) Steel slag (diameter ≤ Ø 0.39 mm) Matrix using 200% by weight of cement and 2 vol.% Of steel fibers (F2S2-0.39): 200 parts by weight of steel slag with a diameter of 0.39 mm based on 100 parts by weight of cement is included , Steel fiber matrix containing 2% of the volume of the specimen

(8) Steel slag (diameter ≤ Ø 0.39 mm) Matrix using 100% by weight of cement and 1 vol.% Of steel fiber (F1S1-0.39): 100 parts by weight of steel slag with a diameter of 0.39 mm or less based on 100 parts by weight of cement is included , Steel fiber matrix containing 1% of the volume of the specimen

The components and compressive strength of the matrix used are shown in [Table 6] below.

[Table 6] shows the components of each matrix and the compressive strength of the matrix.

* Preparation of specimen

For the electro-mechanical performance comparison experiment, test specimens for the eight matrices of [Table 6] were prepared.

The test specimen used in the electro-mechanical experiment was a cube-shaped compression specimen having a width X length X height of 50X50X50 mm, and a copper wire mesh was used as a buried electrode as shown in FIG. 4 as an electrode for investigation of the electro-dynamic response. The buried electrodes were buried inside the specimen at 20 mm intervals.

The formulation was carried out by dry mixing with cement, admixture and fine aggregate (steel slag, sand) excluding water and water reducing agent (SP). In addition, water was divided into four times to prevent fluidity and material separation, and water-reducing agent (SP) was added in small portions according to the formulation, and steel fibers were mixed. The fabricated specimens were cured in 90 ± 2 ^o C high temperature water for 3 days. After the curing was completed, the specimen was naturally dried for 24 hours, and then an experiment was performed.

* Experimental method

For the electro-mechanical response investigation, an AC impedance analyzer was used as the electrical resistivity measurement equipment, and the measurement method was performed through a 2-probe resistance measurement method. The measurement was performed by examining the change in real-time electrical resistivity at a rate of 0.1 seconds / step using an AC impedance analyzer at a point corresponding to the natural frequency of the specimen. The mechanical condition was measured by using a 300 ton displacement-controlled universal test machine (UTM) to change the electrical resistivity of the cement composite material according to the compressive load condition.

* Experiment result

Based on the electrical resistivity (ρ) of the real part corresponding to the natural frequency range of the specimen measured by the AC impedance analyzer, the electrical resistivity (ρ _x ) and The initial electrical resistivity (ρ ₀ ) was used to calculate the rate of change of electrical resistivity (Fractional Change in Resistivity, FCR) as shown in [Equation 3] below.

8 is an experimental result graph showing the electro-mechanical response of the cement composite materials for each of the eight matrices under compressive load.

Referring to FIG. 8, before the maximum compressive stress (σ _p ) of all the specimens for each of the eight matrixes was reached, the electrical resistivity of the cement composite material decreased as the size of the compressive load increased, and the maximum compressive stress (σ _p ) was reached. Thereafter, the electrical resistivity tended to be maintained or increased.

At this time, referring to [Table 7], steel slag and silica sand having a diameter of 0.39 mm or less are 50% of the cement weight, respectively, and the steel fiber is a cement composite material reinforced with a volume ratio of 2% (F2S0.5-0.39), and a diameter of 0.39. It can be seen that the cement composite material (F2S1-0.39) in which the steel slag of mm or less is reinforced with 100% by weight of cement and 2% of the volume ratio of the test specimen shows the best electro-mechanical response among the eight matrices.

Table 7 shows the electro-mechanical response behavior for each of the eight matrices under compressive loading.

* Experimental results according to the size of steel slag particles

As a result of analyzing the electrical resistivity change behavior according to the diameter size of the steel slag particles, when reaching the maximum compressive stress for each specimen, the matrix (F2S1-) using 0.39 mm diameter steel slag as shown in Fig. 9 (a) The specimen of 0.39) showed an electrical resistivity change rate (FCR) of 34.4%, and the specimen of a matrix (F2S1-2) using a 1-2 mm diameter steel slag showed an electrical resistivity change rate of 25.3%, and 2-5 The test body of the matrix (F2S1-5) in which the steel-diameter slag of mm diameter was used showed a change rate of electrical resistivity of 15.5%. Therefore, it can be seen that the electro-mechanical sensitivity according to the particle size of the steel slag is the best of the test sample of the matrix (F2S1-0.39) having the smallest diameter size of the steel slag particles.

* Experimental results according to the amount of steel slag with a particle diameter of 0.39 mm

As a result of analyzing the behavior of change in electrical resistivity according to the amount of steel slag having a particle size of 0.39 mm diameter, as shown in FIG. 9 (b), sand without steel slag was used 100% by weight of cement (F2S0) The test specimen of 23.5% showed an electric resistivity change rate, and the matrix (F2S0.5-0.39) in which steel slag and silica sand were used 50% each compared to the cement weight showed an electric resistivity change rate of 42.9%, and the steel slag was 100 compared to the cement weight. % The matrix used (F2S1-0.39) showed an electrical resistivity change rate of 34.4%, the steel slag used 150% compared to the cement weight matrix (F2S1.5-0.39) showed an electrical resistivity change rate of 29.0%, and the steel slag was The matrix (F2S2-0.39) used for 200% by weight of cement showed a change rate of electrical resistivity of 20.0%. Therefore, the matrix (F2S0.5-0.39) in which steel slag and silica sand were used 50% by weight, respectively, showed the best electro-mechanical sensitivity, and then the matrix in which steel slag was used 100% by weight in cement (F2S1-0.39) It can be seen that) represents the second best electro-mechanical sensitivity.

* Experimental results according to the amount of steel fiber used

As a result of analyzing the electrical resistance change behavior of the cement composite material according to the amount of steel fiber used, as shown in FIG. 9 (c), when the steel slag having a particle size of 0.39 mm diameter was used 100% of the cement weight, The matrix (F2S1-0.39) in which the amount of steel fiber was used as a volume ratio of 2% of the specimen exhibited a change rate of 34.4%, and the matrix (F1S1-0.39) in which the amount of steel fibers was used as the volume ratio of the test sample showed a change rate of 26.7%. . Therefore, it can be seen that the matrix (F2S1-0.39) in which the steel fibers were used at a volume ratio of 2% of the test specimen exhibited the best electro-mechanical sensitivity.

3) Conclusion

Two experiments of 1) and 2) above were conducted to derive the optimum mixing ratio of the cement composite material composition capable of self-stress sensing with high electro-mechanical sensitivity using steel slag and steel fibers. Can be obtained.

(1) The cement composite material composition using a combination of steel slag and steel fiber shows superior electro-mechanical sensitivity compared to the case of using steel fiber, multi-walled carbon nanotubes (MWCNT), and steel fiber and multi-walled carbon nanotubes simultaneously. .

(2) Steel slag and silica sand having a particle size of 0.39 mm or less in diameter is 50% of the cement weight, respectively, and the cement composite material with steel fibers reinforced with 2% of the volume of the specimen (F2S0.5-0.39), and diameter Steel slag with a particle size of 0.39 mm or less is included in 100% by weight of cement, and cement composite material (F2S1-0.39) reinforced with 2% of the volume of the test body is made of steel slag diameter (≤0.39, 1 ~ 2). , 2-5 mm) and conductive material mixing amount (steel slag 0,50,100,150,200%; steel fiber vol 1,2%).

Finally, the compounding ratio of the cement composite material composition capable of self-stress sensing is as shown in [Table 2]. That is, based on 100 parts by weight of cement, 15 parts by weight of silica fume, 25 parts by weight of silica powder, 100 parts by weight of steel slag having a diameter of 0.39 mm or less, 5.1 parts by weight of high performance water reducing agent, and 20 parts by weight of water, steel fiber is a cement composite material Cement composite material composition (F2S1-0.39) included in 2% of the volume of the test body formed by the composition, and 15 parts by weight of silica fume, 25 parts by weight of silica powder, and 50 parts by weight of steel slag having a diameter of 0.39 mm or less based on 100 parts by weight of cement Part, 50 parts by weight of sand, 5.1 parts by weight of a high-performance water reducing agent and 20 parts by weight of water, and the steel fiber is the most excellent cement composite material composition (F2S0.5-0.39), which comprises 2% of the volume of the test sample formed of the cement composite material composition. It has electro-mechanical sensitivity.

Through the two experiments described above, it was confirmed that the cement composite material composition having the suggested formulation has superior sensing performance compared to the existing technology.

As described above, in the embodiment of the present invention, specific matters such as specific components and the like have been described by the limited embodiment and the drawings, but this is provided only to help the overall understanding of the present invention, and the present invention is limited to the above embodiment It will not be, and those skilled in the art to which the present invention pertains can make various modifications and variations from these descriptions. Accordingly, the spirit of the present invention should not be limited to the described embodiments, and should be defined, and all claims that are equivalent or equivalent to these claims, as well as the claims to be described later, belong to the scope of the spirit of the present invention.

100: cement composite material composition capable of self-stress sensing
110: steel fiber
120: steel slag
EN: Electrical network

Claims (8)

Contains cement, silica fume, silica powder, conductive materials, high performance water reducing agents and water,
The conductive material is characterized in that it comprises a steel slag and steel fibers, a self-stressing cement composite material composition capable of sensing.
According to claim 1,
Based on 100 parts by weight of the cement,
15 parts by weight of the silica fume, 25 parts by weight of the silica powder, 50 to 100 parts by weight of the steel slag, 5.1 parts by weight of the high performance water reducing agent, and 20 parts by weight of water, a cement composite material capable of self-stress sensing Composition.
According to claim 2,
The steel slag is based on 100 parts by weight of the cement, characterized in that contained in 100 parts by weight of the cement composite material composition capable of self-stress sensing.
According to claim 2,
The cement composite material composition capable of self-stress sensing, characterized in that it further comprises 50 parts by weight of sand based on 100 parts by weight of the cement, and the steel slag is included by 50 parts by weight.
The method of claim 3 or 4,
The steel slag is a cement composite material composition capable of self-stress sensing, characterized in that it is made of a steel slag fine aggregate formed of particles having a diameter of 0.39 mm or less.
The method of claim 5,
The steel fiber is a cement composite material composition capable of self-stress sensing, characterized in that contained in 2% of the volume of the test body formed of the cement composite material composition.
The method of claim 6,
The steel slag and the steel fiber are in contact with each other to form an electrical network,
A self-stressing cement composite material composition characterized in that the steel slag or the steel fibers intervening in the electrical network increases when a compressive load is applied or the stress changes.
The method of claim 7,
The steel fiber is a cement composite material composition capable of self-stress sensing, comprising a plurality of short smooth steel fibers.

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