**8. Damage detection of CNF concrete columns**

Gao et al expanded the work on self-sensing cement-based materials by studying 152.4 mm by 305 mm (6.00 in. by 12.00 in.) cylindars made of concrete containing CNF [12]. Gao et al crushed the cylinders monotonically and studied the electrical resistance variation. They observed electrical resistance variations up to 80% and concluded that concrete containing CNF can be used for self structural health monitoring.

Howser et al continued Gao et al's work and extended it to a full scale reinforced concrete column containing CNF [4, 12]. A self-consolidating CNF concrete (SCCNFC) column was built and tested under a reversed cyclic load. The structural behavior and the self-sensing ability were examined. The results were compared to the structural and self-sensing ability of a traditional self-consolidating reinforced concrete (SCRC) and a self-consolidating steel fiber concrete (SCSFC) specimen.

All of the columns were 508 mm (20.0 in.) tall with cross-sections of 305 mm by 305 mm (12.00 in. by 12.00 in.). Each specimen contained six #8 (25.4 mm or 1.00 in. diameter) rebar, which corresponded to 3.27% logitudinal steel by volume of concrete. The SCRC and SCCNFC columns contained #2 stirrups with a spacing of 120.7 mm (4.75 in.) providing transverse reinforcement of 0.287% by volume of concrete. Since the columns were designed to be shear critical, the maximum reinforcement spacing was chosen based on the ACI 318 specifications [25]. See Fig. 4 for the cross-section used for the SCRC and SCCNFC columns. SCSFC column contained no transverse reinforcement, as shown in Fig. 5. Each of the columns was rigidly connected to similar foundations. See Fig. 6 for the elevation view of the SCRC and SCCNFC columns and foundations. The SCSFC column is identical to that shown in Fig. 6, except it does not contain transverse reinforcement. Fig. 7 shows the experimental set-up.

**Figure 6.** Elevation View of the Strong Axis of the Shear-Critical SCRC and SCCNFC Columns and Foundations (dimen‐

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The properties of the materials used for the three mixes were as follows:

**a.** Cement: The cement used in all mixtures was ASTM Type III Portland cement.

**b.** Fly Ash: Class C fly ash was used for the SCSFC mix and Class F fly ash was used for the

sions in inches)

**Figure 7.** Experimental Set-Up

SCRC mix.

**Figure 4.** Cross-Section of SCRC and SCCNFC Columns (dimensions in inches)

**Figure 5.** Cross-Section of SCSFC Column (dimensions in inches)

**Figure 6.** Elevation View of the Strong Axis of the Shear-Critical SCRC and SCCNFC Columns and Foundations (dimen‐ sions in inches)

**Figure 7.** Experimental Set-Up

a traditional self-consolidating reinforced concrete (SCRC) and a self-consolidating steel fiber

All of the columns were 508 mm (20.0 in.) tall with cross-sections of 305 mm by 305 mm (12.00 in. by 12.00 in.). Each specimen contained six #8 (25.4 mm or 1.00 in. diameter) rebar, which corresponded to 3.27% logitudinal steel by volume of concrete. The SCRC and SCCNFC columns contained #2 stirrups with a spacing of 120.7 mm (4.75 in.) providing transverse reinforcement of 0.287% by volume of concrete. Since the columns were designed to be shear critical, the maximum reinforcement spacing was chosen based on the ACI 318 specifications [25]. See Fig. 4 for the cross-section used for the SCRC and SCCNFC columns. SCSFC column contained no transverse reinforcement, as shown in Fig. 5. Each of the columns was rigidly connected to similar foundations. See Fig. 6 for the elevation view of the SCRC and SCCNFC columns and foundations. The SCSFC column is identical to that shown in Fig. 6, except it does

not contain transverse reinforcement. Fig. 7 shows the experimental set-up.

**Figure 4.** Cross-Section of SCRC and SCCNFC Columns (dimensions in inches)

**Figure 5.** Cross-Section of SCSFC Column (dimensions in inches)

concrete (SCSFC) specimen.

132 Advances in Nanofibers

The properties of the materials used for the three mixes were as follows:


**c.** Coarse Aggregate: Crushed limestore with a maximum diameter of ¾" was used in the SCCNFC column. River rock with a maximum diameter of ¾" was used in the other columns.

The main goal of testing the SCCNFC column was to prove that concrete containing CNF can be used as a sensor. To test the electrical properties of the concrete, wire meshes were con‐ structed and embedded in each of the columns. The wire meshes were made of 12.7 mm (1/2 in.) hardware cloth with 14 gauge copper wire soldered to it. The wire extended outside of the column. The four probe method for measuring resistance was implemented, and the meshes were placed in the column as shown in Fig. 8. A power supply was attached to the top mesh that provided a current of approximately 31 V DC. An ammeter was attached to the bottom mesh and connected back to the power supply to complete a circuit. The current measured by the ammeter was recorded continuously during the tests by hand. Additional voltmeters were attached to the two middle meshes on both the north and south sides of the column to measure

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voltage. The voltage readings were also recorded continuously throughout the test.

The first step of the load program was to apply an axial load that would remain constant during the course of the test. The axial load equaled one-tenth of each of the columns calculated axial capacity. The axial capacity is dependent on the compressive strength of the concrete, so the

After the application of the axial load, a reversed-cyclic load was added using a 649 kN (146 kip) capacity actuator. The intended load path was to use force control to complete two cycles each of ±89 kN (20 k), ±178 kN (40 k), and ±267 kN (60 k). A positive force denotes a push by the actuator while a negative force represents a pull. At the point of longitudinal steel yielding, the test switched to displacement control and completed two cycles each at a displacement

**Figure 8.** Four Probe Method of Resistance Measurement

axial force for each specimen varied.


The mix proportions used for the three columns can be seen in Table 1. One percent fiber by volume was used for both of the fiber columns chosen based on literature review. It was discovered by Gao et al that CNF has an optimal dosage of approximately 1% by volume [12] [12]. It was found by many researchers that increased steel fiber increases concrete properties; however, after a percentage of 1% fibers by volume, the concrete becomes increasingly less workable, which could cause problems in construction such as honeycombing [39-41].


**Table 1.** Mix Proportions in kg/m3 (lb/yd3) of Concrete

The main goal of testing the SCCNFC column was to prove that concrete containing CNF can be used as a sensor. To test the electrical properties of the concrete, wire meshes were con‐ structed and embedded in each of the columns. The wire meshes were made of 12.7 mm (1/2 in.) hardware cloth with 14 gauge copper wire soldered to it. The wire extended outside of the column. The four probe method for measuring resistance was implemented, and the meshes were placed in the column as shown in Fig. 8. A power supply was attached to the top mesh that provided a current of approximately 31 V DC. An ammeter was attached to the bottom mesh and connected back to the power supply to complete a circuit. The current measured by the ammeter was recorded continuously during the tests by hand. Additional voltmeters were attached to the two middle meshes on both the north and south sides of the column to measure voltage. The voltage readings were also recorded continuously throughout the test.

**Figure 8.** Four Probe Method of Resistance Measurement

**c.** Coarse Aggregate: Crushed limestore with a maximum diameter of ¾" was used in the SCCNFC column. River rock with a maximum diameter of ¾" was used in the other

**d.** Fine Aggregate: Natural river sand with a fineness modulus of 2.71 was used in all mixes.

**e.** High Range Water Reducer (HRWR): Glenium® 3200HES was used in the SCCNFC column and Glenium® 3400 HES was used in the other columns. Both chemicals were

**f.** Viscosity Modifying Agent (VMA): RHEOMAC® VMA 450 was used in the specimens

**g.** Steel Fibers: Dramix® ZP305 fibers were used in the SCSFC mix. This was a hooked fiber with a specific gravity of 7.85. The diameter of the fiber is 0.55 mm (0.0217 in.) and the

**h.** Carbon Nanofibers: Pyrograf Products, Inc. PR-19-XT-LHT-OX fibers were used in this study. The specific gravity of the fibers was 0.0742. The diameter of the fibers was 149 nm (5.87e-6 in.) and the length was 19 µm (7.48e-4 in.) resulting in an aspect ratio of 128. The mix proportions used for the three columns can be seen in Table 1. One percent fiber by volume was used for both of the fiber columns chosen based on literature review. It was discovered by Gao et al that CNF has an optimal dosage of approximately 1% by volume [12] [12]. It was found by many researchers that increased steel fiber increases concrete properties; however, after a percentage of 1% fibers by volume, the concrete becomes increasingly less workable, which could cause problems in construction such as honeycombing [39-41].

> **Material SCRC Mix SCSFC Mix SCCNFC Mix Cement** 446 (752) 446 (752) 457 (771)

**Water** 224 (377) 224 (377) 182 (307)

**Fly Ash (Class C)** - 299 (504) - **Fly Ash (Class F)** 299 (504) - - **Fine Aggregate** 937 (1580) 937 (1580) 898 (1514)

**Coarse Aggregate (Limestone)** - - 859 (1448) **Coarse Aggregate (River Rock)** 491 (827) 491 (827) -

**Glenium® 3400HES** 2.81 (4.73) 2.81 (4.73) - **Glenium® 7700HES** - - 2.34 (3.94) **REHEOMAC® VMA 450** 5.69 (9.59) 5.69 (9.59) - **Steel Fibers** - 79.8 (134) - **Carbon Nanofibers** - - 3.23 (5.45)

polycarboxylate admixtures from BASF Chemical Co.

length is 30 mm (1.18 in.) resulting in an aspect ratio of 55.

and also supplied by BASF Chemical Co.

**Table 1.** Mix Proportions in kg/m3 (lb/yd3) of Concrete

columns.

134 Advances in Nanofibers

The first step of the load program was to apply an axial load that would remain constant during the course of the test. The axial load equaled one-tenth of each of the columns calculated axial capacity. The axial capacity is dependent on the compressive strength of the concrete, so the axial force for each specimen varied.

After the application of the axial load, a reversed-cyclic load was added using a 649 kN (146 kip) capacity actuator. The intended load path was to use force control to complete two cycles each of ±89 kN (20 k), ±178 kN (40 k), and ±267 kN (60 k). A positive force denotes a push by the actuator while a negative force represents a pull. At the point of longitudinal steel yielding, the test switched to displacement control and completed two cycles each at a displacement ductility of 2, 3, 4, etc. Once failure occurred, a descending branch on the load versus dis‐ placement curve was obtained in displacement control mode.

The load path followed forthe SCRC column specimen can be seen in Fig. 9 with the first cracks, switchtodisplacementcontrolandfailuremarked.Thefirstcrackonthesouthsideofthecolumn occurred at -178 kN (-40 k). The first shear crack formed on the column during the first -178 kN (-40 k) cycle at -178 kN (-40 k) on the west side. The column failed in shear and crushing of concrete at 276 kN (62 k). The west side of the column exhibited crushing of the concrete struts with large shear cracks. The east side exhibited local crushing at the actuator connection. The maximum displacement at the top of the column (drift) was 12.7 mm (0.50 in.).

**Figure 9.** SCRC Column Load Path

The load path followed for the SCSFC column can be seen in Fig. 10 with the first cracks and failure marked. The first shear and flexural cracks formed on the column during the second 178 kN (40 k) cycle at 178 kN (40 k) on the west and north sides, respectively. The second flexural crack formed on the south side during the second -178 kN (-40 k) cycle at -178 kN (-40 k). The column failed suddenly in shear and crushing at 347 kN (78.0 k) on the west side of the column before the rebar yielded. The maximum displacement was 8.38 mm (0.33 in.).

little correlation between the resistance plots and the force or strain plots for the SCRC or SCSFC column. Fig. 12 shows the relationship between the SCRC column's horizontal force, LVDT strain, and electrical resistance versus time on the north side of the column. There is no relationship between the peaks and valleys in the electrical resistance and the load or strain

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Fig. 13 shows the SCSFC column's force, strain, and resistance versus time on the north and south sides of the column, respectively. As shown by the grey vertical lines, there is not a relationship between the peaks and valleys in the resistance and load or strain until major cracking began to occur. After major cracking began to occur, the peaks and valleys in the electrical resistance began to correspond with the load and strain peaks and valleys. This point

Fig. 14 shows relationship between the SCCNFC column's horizontal load, LVDT strain and electrical resistance versus time on the north side of column. As shown by the vertical lines in

on the north side of the column.

**Figure 11.** SCCNFC Column Load Path

**Figure 10.** SCSFC Column Load Path

is shown by the dashed line in Fig. 13.

The actual load path followed for the SCCNFC column can be seen in Fig. 11. The pump shut down during the test, and the actuator unloaded during the fifth cycle of the test. The pump was turned back on and the test resumed. The first flexural crack formed on the column at 160 kN (36 k) on the east, west and north sides. The second flexural crack formed on the east, west and south sides at a load of -158 kN (-35.6 k). The column failed in the combined modes of shear and concrete crushing due to flexure at 298 kN (67 k) on the west side of the column. The maximum displacement was 10.16 mm (0.4 in.).

During each of the column tests, the electrical resistance was determined to check the selfsensing ability of the concrete. The electrical readings showed a great correlation between the peaks in the applied horizontal force, strain, and resistance plots for the SCCNFC column but

**Figure 10.** SCSFC Column Load Path

ductility of 2, 3, 4, etc. Once failure occurred, a descending branch on the load versus dis‐

The load path followed forthe SCRC column specimen can be seen in Fig. 9 with the first cracks, switchtodisplacementcontrolandfailuremarked.Thefirstcrackonthesouthsideofthecolumn occurred at -178 kN (-40 k). The first shear crack formed on the column during the first -178 kN (-40 k) cycle at -178 kN (-40 k) on the west side. The column failed in shear and crushing of concrete at 276 kN (62 k). The west side of the column exhibited crushing of the concrete struts with large shear cracks. The east side exhibited local crushing at the actuator connection. The

The load path followed for the SCSFC column can be seen in Fig. 10 with the first cracks and failure marked. The first shear and flexural cracks formed on the column during the second 178 kN (40 k) cycle at 178 kN (40 k) on the west and north sides, respectively. The second flexural crack formed on the south side during the second -178 kN (-40 k) cycle at -178 kN (-40 k). The column failed suddenly in shear and crushing at 347 kN (78.0 k) on the west side of the

The actual load path followed for the SCCNFC column can be seen in Fig. 11. The pump shut down during the test, and the actuator unloaded during the fifth cycle of the test. The pump was turned back on and the test resumed. The first flexural crack formed on the column at 160 kN (36 k) on the east, west and north sides. The second flexural crack formed on the east, west and south sides at a load of -158 kN (-35.6 k). The column failed in the combined modes of shear and concrete crushing due to flexure at 298 kN (67 k) on the west side of the column.

During each of the column tests, the electrical resistance was determined to check the selfsensing ability of the concrete. The electrical readings showed a great correlation between the peaks in the applied horizontal force, strain, and resistance plots for the SCCNFC column but

column before the rebar yielded. The maximum displacement was 8.38 mm (0.33 in.).

The maximum displacement was 10.16 mm (0.4 in.).

maximum displacement at the top of the column (drift) was 12.7 mm (0.50 in.).

placement curve was obtained in displacement control mode.

**Figure 9.** SCRC Column Load Path

136 Advances in Nanofibers

**Figure 11.** SCCNFC Column Load Path

little correlation between the resistance plots and the force or strain plots for the SCRC or SCSFC column. Fig. 12 shows the relationship between the SCRC column's horizontal force, LVDT strain, and electrical resistance versus time on the north side of the column. There is no relationship between the peaks and valleys in the electrical resistance and the load or strain on the north side of the column.

Fig. 13 shows the SCSFC column's force, strain, and resistance versus time on the north and south sides of the column, respectively. As shown by the grey vertical lines, there is not a relationship between the peaks and valleys in the resistance and load or strain until major cracking began to occur. After major cracking began to occur, the peaks and valleys in the electrical resistance began to correspond with the load and strain peaks and valleys. This point is shown by the dashed line in Fig. 13.

Fig. 14 shows relationship between the SCCNFC column's horizontal load, LVDT strain and electrical resistance versus time on the north side of column. As shown by the vertical lines in

**Figure 12.** SCRC Column Comparison of Horizontal Force, LVDT Strain and Electrical Resistance on North Side

at the top of the column for the first five cycles of the test. It is obvious from Fig. 15 that the column shows major damage at approximately a deflection of 2.03 mm (0.08 in.). This corre‐ sponds to the steel yielding in the SCCNFC column. This proves that SCCNFC can be used as

**Figure 14.** SCCNFC Column Comparison of Horizontal Force, LVDT Strain and Electrical Resistance on North Side

Figure 14.SCCNFC Column Comparison of Horizontal Force, LVDT Strain and Electrical Resistance on North Side

Because of the strong correlation found between the horizontal load, LVDT strain and electrical resistance verses time graphs for the SCCNFC column, the electrical resistance variation (ERV) was calculated and compared to the deflection at the top of the column. ERV is the measured electrical resistance minus the initial electrical resistance quantity divided by the initial electrical resistance. Fig. 15 shows the relationship between the ERV and deflection at the top of the column for the first five cycles of the test. It is obvious from Fig. 15 that the column shows major damage at approximately a deflection of 2.03 mm (0.08 in.). This corresponds to the steel yielding in the SCCNFC column. This proves that SCCNFC can be used as a type of self-structural health

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Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5

Self-consolidating carbon nanofiber concrete (SCCNFC) follows the definition for nanotechnology set forth by the National Science Foundation and National Nanotechnology Initiative [2]. The size range of the carbon nanofibers (CNF) is approximately 100 nanometers, the SCCNFC is able to measure damage in the composite, and the CNF have properties that are specific to the

Well-dispersed CNF improves the strength and stiffness of concrete. Excess concentration leads to poorly dispersed CNF clumps inside the concrete and has a negative effect on both strength and electrical sensitivity. Highly workable and stable selfconsolidation concrete (SCC) can maintain its workability and stability with the addition of fibers. SCC greatly increases the

As proven by Gao et al [12] and Howser et al [4], SCCNFC can be used as a reversible strain sensor. In Howser et al's test [4], the peaks and valleys in the electrical resistance readings of the SCCNFC match the peaks and valleys of the applied force and the strain in the concrete. While the peaks and valleys in the electrical resistance readings of the self-consolidating reinforced concrete and self-consolidating steel fiber concrete specimens occasionally matched, there was not enough correspondence to safely assume that these concretes could be used as a reversible strain sensor. It was concluded that when an appropriate dosage of CNF is used,

[2] Roco, M. C. National Nanotechnology Initiative - Past, Present, Future. In W. A. Goddard, D. Brenner, S. E. Lyshevski, & G. J. Iafrate (Eds.), Handbook of Nanoscience, Engineering, and Technology (2nd ed.). Boca Raton, FL: CRC Press 2007; 3.1-3.26. [3] Narayan, R. J., Kumta, P. N., Sfeir, C., Lee, D.-H., Choi, D., Olton, D. Nanostructured ceramics in medical devices: Applications

[4] Howser, R. N., Dhonde, H. B., Mo, Y. L. Self-sensing of carbon nanofiber concrete columns subjected to reversed cyclic

[5] Bartos, P. Nanotechnology in Construction: A Roadmap for Development. American Concrete Institute Special Publication

[6] Sanchez, F., Sobolev, K. Nanotechnology in concrete - A review. Construction and Building Materials 2010; 24, 2060-2071.

a type of self-structural health monitoring system.

Figure 15.SCCNFC Column ERV versus Horizontal Deflection

‐,0.07 ‐,0.02 ,0.03 ,0.08 ,0.13

**Deflection (in.)**

‐10

**Figure 15.** SCCNFC Column ERV versus Horizontal Deflection

0

10

20

30

40

50

60

70

80

dispersion of carbon nanofibers (CNF) [12].

SCCNFC can be used for self-structural health monitoring.

loading. Smart Materials and Structures 2011; 20 (8).

[1] Feynman, R. There's Plenty of Room at the Bottom. Engineering and Science 1960; 23, 22-36.

and prospects. Journal of the Minerals, Metals and Materials Society 2004; 56 (10), 38-43.

monitoring system.

**ERV**

**9. Conclusions** 

nanoscale.

**References** 

2008; 254, 1-14.

**Figure 13.** SCRC Column Comparison of Horizontal Force, LVDT Strain and Electrical Resistance on North Side

the grid, there is very good correlation between the force, strain and resistance. On the north side of the column, the peaks and valleys matched up until the point that the column was greatly damaged.

Because of the strong correlation found between the horizontal load, LVDT strain, and electrical resistance verses time graphs for the SCCNFC column, the electrical resistance variation (ERV) was calculated and compared to the deflection at the top of the column. ERV is the measured electrical resistance minus the initial electrical resistance quantity divided by the initial electrical resistance. Fig. 15 shows the relationship between the ERV and deflection

Carbon Nanofiber Concrete for Damage Detection of Infrastructure http://dx.doi.org/10.5772/57096 139

**Figure 14.** SCCNFC Column Comparison of Horizontal Force, LVDT Strain and Electrical Resistance on North Side

at the top of the column for the first five cycles of the test. It is obvious from Fig. 15 that the column shows major damage at approximately a deflection of 2.03 mm (0.08 in.). This corre‐ sponds to the steel yielding in the SCCNFC column. This proves that SCCNFC can be used as a type of self-structural health monitoring system. the SCCNFC column, the electrical resistance variation (ERV) was calculated and compared to the deflection at the top of the column. ERV is the measured electrical resistance minus the initial electrical resistance quantity divided by the initial electrical resistance. Fig. 15 shows the relationship between the ERV and deflection at the top of the column for the first five cycles of the test. It is obvious from Fig. 15 that the column shows major damage at approximately a deflection of 2.03 mm (0.08 in.). This corresponds to the steel yielding in the SCCNFC column. This proves that SCCNFC can be used as a type of self-structural health

Figure 14.SCCNFC Column Comparison of Horizontal Force, LVDT Strain and Electrical Resistance on North Side

Because of the strong correlation found between the horizontal load, LVDT strain and electrical resistance verses time graphs for

Self-consolidating carbon nanofiber concrete (SCCNFC) follows the definition for nanotechnology set forth by the National Science Foundation and National Nanotechnology Initiative [2]. The size range of the carbon nanofibers (CNF) is approximately 100 nanometers, the SCCNFC is able to measure damage in the composite, and the CNF have properties that are specific to the

Well-dispersed CNF improves the strength and stiffness of concrete. Excess concentration leads to poorly dispersed CNF clumps inside the concrete and has a negative effect on both strength and electrical sensitivity. Highly workable and stable selfconsolidation concrete (SCC) can maintain its workability and stability with the addition of fibers. SCC greatly increases the

As proven by Gao et al [12] and Howser et al [4], SCCNFC can be used as a reversible strain sensor. In Howser et al's test [4], the peaks and valleys in the electrical resistance readings of the SCCNFC match the peaks and valleys of the applied force and the strain in the concrete. While the peaks and valleys in the electrical resistance readings of the self-consolidating reinforced concrete and self-consolidating steel fiber concrete specimens occasionally matched, there was not enough correspondence to safely assume that these concretes could be used as a reversible strain sensor. It was concluded that when an appropriate dosage of CNF is used,

[2] Roco, M. C. National Nanotechnology Initiative - Past, Present, Future. In W. A. Goddard, D. Brenner, S. E. Lyshevski, & G. J. Iafrate (Eds.), Handbook of Nanoscience, Engineering, and Technology (2nd ed.). Boca Raton, FL: CRC Press 2007; 3.1-3.26. [3] Narayan, R. J., Kumta, P. N., Sfeir, C., Lee, D.-H., Choi, D., Olton, D. Nanostructured ceramics in medical devices: Applications

[4] Howser, R. N., Dhonde, H. B., Mo, Y. L. Self-sensing of carbon nanofiber concrete columns subjected to reversed cyclic

[5] Bartos, P. Nanotechnology in Construction: A Roadmap for Development. American Concrete Institute Special Publication

[6] Sanchez, F., Sobolev, K. Nanotechnology in concrete - A review. Construction and Building Materials 2010; 24, 2060-2071.

Figure 15.SCCNFC Column ERV versus Horizontal Deflection **Figure 15.** SCCNFC Column ERV versus Horizontal Deflection

dispersion of carbon nanofibers (CNF) [12].

SCCNFC can be used for self-structural health monitoring.

loading. Smart Materials and Structures 2011; 20 (8).

[1] Feynman, R. There's Plenty of Room at the Bottom. Engineering and Science 1960; 23, 22-36.

and prospects. Journal of the Minerals, Metals and Materials Society 2004; 56 (10), 38-43.

**9. Conclusions** 

nanoscale.

**References** 

2008; 254, 1-14.

monitoring system.

the grid, there is very good correlation between the force, strain and resistance. On the north side of the column, the peaks and valleys matched up until the point that the column was

**Figure 13.** SCRC Column Comparison of Horizontal Force, LVDT Strain and Electrical Resistance on North Side

**Figure 12.** SCRC Column Comparison of Horizontal Force, LVDT Strain and Electrical Resistance on North Side

Because of the strong correlation found between the horizontal load, LVDT strain, and electrical resistance verses time graphs for the SCCNFC column, the electrical resistance variation (ERV) was calculated and compared to the deflection at the top of the column. ERV is the measured electrical resistance minus the initial electrical resistance quantity divided by the initial electrical resistance. Fig. 15 shows the relationship between the ERV and deflection

greatly damaged.

138 Advances in Nanofibers
