Durability of Concrete in Cold Regions – Evaluation of deterioration from combined frost and salt damage using ultrasonic

waves – Fumio-TAGUCHI，Hirotake-ENDOH

Material Research Team, Civil Engineering Research Institute for Cold Region

Abstract: The purpose of this study was to establish a diagnosis technique that allows quick and simple evaluation of the

degree of deterioration caused by combined frost and salt damage (frost-salt damage) in concrete structures. In the

study, focus was placed on the theory of the surface scanning method, which is a nondestructive approach that can be

used to easily estimate the thickness of deteriorated areas from the surface, and the technique was applied to diagnosis

of frost-salt damage. The results revealed that surface scanning was effective as a nondestructive method of estimating

the thickness of the deteriorated area affected by frost-salt damage with a certain level of accuracy, and that the depth of

parts where the relative dynamic modulus of elasticity is lower than the value of the threshold (60%) can be estimated

from the slope of a graph created using the measurement data thus obtained.

Keywords: frost damage, deterioration from combined frost and salt damage, ultrasonic propagation velocity,

nondestructive method, surface scanning, diagnosis

1. Introduction

Concrete structures in cold regions are susceptible to

deterioration from frost damage or combined frost and salt

damage due to severe freeze-thaw action and other causes.

Such deterioration also results in reduced concrete strength,

an increased rate of chloride ion penetration and decreased

bond strength of reinforcements.

At present, frost deterioration of concrete is usually

diagnosed by evaluating its depth and degree based on

microscopic measurement of the air-bubble spacing factors of

core samples and examination of ultrasonic propagation

velocity in such core samples at certain depths. However,

core sampling causes damage to concrete components, and

investigating wide areas using such methods involves high

cost and takes a long time. There are also problems related

to work efficiency, such as the necessity of scaffolding for

boring machines.

Accordingly, an experimental study on frost damage

diagnosis using the surface scanning method1) was conducted

with the aim of establishing a diagnosis technique that can be

used to evaluate the degree of deterioration caused by

frost-salt damage in concrete structures through a quick and

simple nondestructive testing approach.

2. Surface scanning method

Surface scanning is a method of estimating the thickness of

deteriorated layers near the concrete surface through

nondestructive testing using ultrasonic waves 1).

If an ultrasonic emission sensor and a receiving sensor

are placed on the concrete surface and the receiving sensor is

moved away from the emission sensor at certain intervals as

shown in Fig. 1, ultrasonic waves passing through

deteriorated areas reach the receiving sensor first. However,

when the distance between the emission and receiving sensors

exceeds a certain level, ultrasonic waves spread mostly via

the top edge of the healthy area where the propagation

velocity becomes high and the spread time reaches its

minimum. The rate of increase in the ultrasonic spread time

becomes lower with greater distances between the emission

and receiving sensors, and the relationship between this

distance and the increase in ultrasonic spread time is as

indicated by the line graph shown in Fig. 1.

Assuming that the distance from the origin to the

inflection point where the slope of the line changes is X0 and

that the ultrasonic propagation velocity is Vd in the

deteriorated area and Vs at the edge of the healthy area (Vd

and Vs are both reciprocals of the graph slope), the thickness

of the deteriorated area t can be expressed using the equation

below1).

Receiving

Deteriorated area

Healthy area

Xo

t

Vd

Vs

Distance from the emission sensorto the receiving sensor

Ultr

ason

ic s

prea

d tim

eEmission

Fig. 1 Concept of the surface scanning method1)

ds

ds

VV

VVXt

2

0 (1)

The purpose of the present study was to apply this theory

to frost damage diagnosis. In other words, it was conducted

to determine whether the depth and degree of frost damage in

hardened concrete can be evaluated using a nondestructive

surface scanning method on the assumption that the

deteriorated area shown in Fig. 1 was affected by frost

damage.

3. Overview of the laboratory experiment

3.1 Specimen mix proportions

Table 1 shows the mix proportions of the specimens used.

The water-cement ratio was 55% – a value usually used in

cold, snowy regions to ensure resistance to frost damage.

The material parameters were determined with focus on

cement types and maximum size of coarse aggregate. Two

types of cement (normal Portland and Type B blast-furnace

slag) and three coarse aggregate conditions (mortar without

coarse aggregate, a maximum size of 20 mm and a maximum

size of 40 mm) were used. Hereafter, mix proportions will

be represented by symbols combining the type of cement

(normal: N; blast-furnace slag: B) and coarse aggregate (no

Table 1 Mix proportion of specimens

Symbol Cement Gmax

(mm)Unit (kg/m3)

W C S G

NG0 NP － 267 486 1,551 －

NG20 NP 20 154 280 893 1,119

NG40 NP 40 154 280 893 1,123

BG20 BB 20 154 280 889 1,115Note: NP is Normal, BB is Blast-furnace slag, Gmax is the maximum size of coarse aggregate, Unit is Quantity of material per unit volume of concrete, W is water, C is cement, S is fine aggregate and G is coarse aggregate. For all mix proportions, the water-cement ratio was 55% and the sand-coarse aggregate ratio was 44% (except for NG0 = mortar). To accelerate frost deterioration, no AE agent was used.

Single-surface freezing-thawing test by covering the flat surfaceof the specimen withapproximately 6 mm (1/4 in.)of water

After a certain numberof cycles, measurementusing the surface scanningmethod is conducted.

Specimens are then removed with a cutterand the ultrasonic propagation velocity(ultrasonic transmission method) in the depthdirection is measured.

150

150

100

100

400

100

Water (depth: approximately 6 mm (1/4 in.))

5

Fig. 2 Specimen and flow of the experiment

coarse aggregate: G0; max. size 20 mm: G20; max. size 40

mm: G40).

3.2 Specimens

The specimen dimensions were 100 x 100 x 400 mm (Fig. 2).

The specimens were wet-cured until an age of 7 days, and

were left standing in constant temperature and moisture

room (temperature: 20°C; humidity: 60%) until the 28th day.

At an age of 21 days, banks were attached to the placement

surface in the single-surface freezing-thawing test to keep

water on the concrete surface.

3.3 Single-surface freeze-thaw test and measurement

Figure 2 shows the flow of the experiment. Frost

deterioration was created in a single-surface freeze-thaw test

started at an age of 28 days. In the test (performed in

reference to ASTM C672), the water depth was kept at

approximately 6 mm on the concrete surface during 30, 59, 91

or 121 cycles of freeze-thaw action (1 cycle = 16 hours at

-18°C and 8 hours at 23°C in a day). Measurement using the

surface scanning method with an ultrasonic measurement

device was conducted at each cycle to examine the

relationship between the emission sensor-receiving sensor

distance and the ultrasonic spread time shown at the bottom

of Fig. 1. The emission sensor-receiving sensor distances

were 50, 100, 150, 200, 250, 300, 350 and 400 mm. The fre

quency of the measurement device was 28 kHz, and both the

emission and receiving sensors had diameters of 20 mm.

After measurement using the surface scanning method,

samples were removed from the center of the specimens using

a concrete cutter, and the ultrasonic propagation velocity

distribution between depths of 10 and 90 mm was examined

at intervals of 10 mm by placing ultrasonic emission and

receiving sensors on the cut surface of the samples (this

method is referred to here as the ultrasonic transmission

method).

4. Results of the laboratory experiment

4.1 Results of measurement using the surface scanning

method

Figure 3 shows an example of the relationship between the

emission sensor-receiving sensor distance and the ultrasonic

spread time found using the surface scanning method. The

line graph was created using a two-piece linear regression

software function2). Although there were no clear two-piece

lines before the start of the test (at zero cycles), they appeared

noticeably as the number of cycles increased.

4.2 Evaluation of the degree of frost damage using the surface

scanning method

Table 2 shows the results of calculating Vd and Vs (the

ultrasonic propagation velocity in deteriorated and healthy

areas, respectively) and t (the thickness of the deteriorated

area). In general, the accuracy of ultrasonic propagation

velocity measurement is assumed to be ±5%3). As the finite

difference between Vd and Vs at 91 cycles with BG20 was

±9% and slightly larger than 5%, t was not calculated for this

case on the assumption that there was no clear inflection

point.

Additionally, while the t value for BG20 at 121 cycles was

estimated to be 145 mm in calculation, it was assumed to be

100 mm because the upper limit was the specimen height of

100 mm.

The velocity Vd in the deteriorated area decreased with

0cyc

leS

prea

dtim

e（μ

s）

30cy

cle

Spr

ead

time

（μs）

59cy

cle

Spr

ead

time

（μs）

91cy

cle

Spr

ead

time

（μs）

121c

ycle

Spr

ead

time

（μs）

0cycle

30cycle

59cycle

91cycle

121cycle

0

50

100

0

50

100

0

50

100

0

50

100

0

50

100

200

150NG40

0 100 200 300 400

Distance between the emission andreceiving sensors(mm)

Fig. 3 Example measurement results obtained using the

surface scanning method (NG40)

Table 2 Calculation results for Vd, Vs and t

NG0 NG20

Cycles Vd Vs F1) t Vd Vs F1) t

30 3.0 4.2 17 21 3.0 3.8 12 14

59 2.9 5.7 33 88 2.6 5.1 33 56

91 3.0 6.1 33 96 2.0 4.0 33 53

121 3.1 4.6 19 64 2.5 4.4 28 63

NG40 BG20

Cycles Vd Vs F1) t Vd Vs F1) t

30 2.6 5.9 40 87 2.6 5.1 32 85

59 1.8 5.0 47 75 1.4 2.4 25 51

91 1.5 6.1 61 82 0.9 1.1 9 －2)

121 1.6 3.2 33 62 0.3 3.0 79 1003)

Note: The unit for Vd and Vs (the values of ultrasonic propagation velocity in deteriorated and healthy areas, respectively) is km/s.The unit for finite difference (the change ratio of Vs and Vd for the average value of Vs and Vd) is %.The unit for t (the thickness of the deteriorated area) is mm. 1) F is Finite difference 2) As the finite difference was small, it was judged that there

was no inflection point and t was not calculated. 3) Although the calculated value of t was 145 mm, it was

assumed to be 100 mm because the upper limit was the specimen height of 100 mm.

the progress of cycles in the series other than for NG0

(approx. 3.0 km/s), although there were variations, indicating

that damage to the deterioration section progressed as a result

of repeated freeze-thaw action.

4.4 Comparison of measurements obtained using the surface

scanning and ultrasonic transmission methods.

As an example, Fig. 4 shows the results of measurement for

NG40 using the ultrasonic transmission method. The

100

80

60

40

20

0

Dep

th fr

om s

urfa

ce(m

m)

10

30

50

70

90

Relative dynamic modulus of elasticity(%)0 20 40 60 80 100 120

NG40

Fig. 4 Results of measurement using the ultrasonic

transmission method

dynamic modulus of elasticity was calculated from the

ultrasonic propagation velocity using Eq. (2)4), and the

relative dynamic modulus of elasticity at each depth was

found from the calculated value using Eq. (3). The values

found are plotted in the figure.

708.20438.140387.4 2 nndn VVE (2)

1000

d

dn

E

ERE (3)

where Vn is the ultrasonic propagation velocity at n

cycles (km/s), Edn is the dynamic modulus of elasticity at n

cycles (GPa), RE is the relative dynamic modulus of elasticity

(%) and Ed0 is the dynamic modulus of elasticity before the

freeze-thaw test (GPa).

By including the t value calculated using the surface

scanning method (NG40 in Table 2) and the relative dynamic

modulus of elasticity at a depth of t in this figure, comparison

between the results of evaluation using the surface scanning

method and the ultrasonic transmission method were

performed. With the ultrasonic transmission method, the

relative dynamic modulus of elasticity decreased dramatically

for the NG40 specimen after 30 cycles, and the results

corresponded with those of evaluation using the surface

scanning method. While the depth of the deteriorated area

was diagnosed as approximately 80 mm with the ultrasonic

transmission method as the relative dynamic modulus of

elasticity at 80 mm or deeper exceeded the 60% threshold5) at

140

120

100

80

60

40

20

y=22.98x-0.94

Equation fromreference6)

Rel

ativ

e dy

nam

ic m

odul

us o

f el

astic

ityat

a d

epth

of

10 m

m(%

)

Slope of the graph between the origin andinflection point from the surface scanning method

0.4 0.6 0.8 1.00.20.0 1.2

NG0

Data fromreference6)

Fig. 5 Slope (origin – inflection point) and relative dynamic

modulus of elasticity at a depth of 10 mm

140

120

100

80

60

40

200.4 0.6 0.8 1.0

y=9.62x-1.33

Rel

ativ

e dy

nam

ic m

odul

us o

f el

astic

ityat

a d

epth

of

tmm

(%)

Slope of the graph after the inflection pointfrom the surface scanning method

0.20.0 1.2

Threshold of frost resistance(60%)

Average(75.8%)

59th cycle for BG20

Fig. 6 Slope (after the inflection point) and relative dynamic

modulus of elasticity at a depth of t

all cycles, the relative dynamic modulus of elasticity

calculated using the surface scanning method at a depth of t

(= 62, 75, 82, 87 cm) varied from approximately 40 to 90%.

However, the depth at which the relative dynamic modulus of

elasticity becomes equivalent to 60% was assumed to be

between around 60 and 80 cm. It was therefore presumed

that surface scanning was effective as a nondestructive

method of roughly estimating the depth of the deteriorated

area.

4.5 Diagnosis of the relative dynamic modulus of elasticity in

the deteriorated area using the surface scanning method

Next, diagnosis of the relative dynamic modulus of elasticity

in the deteriorated area using the surface scanning method

was examined. The reciprocal of the slope between the

origin and inflection point of Fig. 1 above represents the

ultrasonic propagation velocity of the deteriorated area Vd.

It can also be found from Eq. (2) that this velocity value is

closely related to the relative dynamic modulus of elasticity.

Figure 5 shows the relationship between this slope and the

relative dynamic modulus of elasticity at the shallowest point

(10 mm in depth) found using the ultrasonic transmission

method for specimens NG0 – 40 and BG20. The regression

equation obtained in a study conducted by the authors in the

previous year using concrete specimens6) is shown in the

figure. Looking at the plot values of concrete excluding data

for mortar (NG0), the tendency resembles that of the previous

year’s data6).

Next, focus was placed on the slope after the inflection

point of the line graph in Fig. 1. The reciprocal of this slope

represents the velocity of ultrasonic waves that pass through

the edge of the healthy area Vs. Similarly, Fig. 6 shows the

relationship between Vs and the ultrasonic propagation

velocity at depth t. The same tendency was observed again

at the edge of the healthy area. While the average relative

dynamic modulus of elasticity at depth t found using the

ultrasonic transmission method was 75.8%, the value found at

the edge of the healthy area using the surface scanning

method was higher than the 60%5) threshold of frost

resistance.

This means that if the ultrasonic velocity at depth t is

lower than the 60% threshold in surface scanning, the value

found by the more accurate ultrasonic transmission method

using core samples is almost certainly 60% or less and the

deteriorated area can be evaluated safely using the surface

scanning method.

From the above results, the relative dynamic modulus of

elasticity was estimated on the assumption that it decreases

linearly in the depth direction at a depth of 10 mm (the

measurable shallowest depth for the 20-mm-diameter sensor)

to t. Based on this concept, the estimated relative dynamic

modulus of elasticity at a random depth of h (within the

deteriorated area) from the surface can be expressed using the

equation below.

94.01

94.01

33.12 98.2210

10

98.2262.9

xht

xxREh

(4)

100

90

80

70

60

50

40

30

20

10

01009080706050403020100

It is highly likely that the relative dynamic modulus of elasticity is lower than the value of the threshold.

It is highly likely that the relativedynamic modulus of elasticity ishigher than the value of the threshold.

The relative dynamic modulus of elasticity may belower than the value of the threshold.

10

t

22.98x1-0.94 9.62x2-1.33

Dep

th fr

om s

urfa

ce(m

m)

Relative dynamic modulusof elasticity(%)

Estimated value

Det

erio

rate

d ar

ea

h

Measured value

Eq.(4)

Concept of calculation

Evaluation

MortarConcrete

Hea

lthy

area

Mea

sure

d va

lue(

%)

Estimated value(%)

Fig. 7 Estimated and measured values of the relative

dynamic modulus of elasticity

where REh is the estimated relative dynamic modulus of

elasticity (%) at a depth of h (10 mm ≤ h ≤ t), x1 is the slope

of the graph between the origin and inflection point, and x2 is

the slope of the graph after the inflection point.

Figure 7 shows the results. Since the relative dynamic

modulus of elasticity was assumed to decrease linearly at a

certain rate between a depth of 10 mm and t and the influence

of moisture7) was not taken into account, the relationship

between the estimated values found using the surface

scanning method and the measured values found using the

ultrasonic transmission method varied. The relative

dynamic modulus of elasticity could not be ascertained with

high accuracy. However, Eq. (4) was considered effective

as a method of estimating the depth of the part where the

relative dynamic modulus of elasticity is lower than the value

of the threshold (60%).

5. Surveys of actual structures using the surface scanning

method

5.1 Survey location

Next, surveys of actual structures were conducted using the

surface scanning method. The survey sections were

concrete of a control platform for a river sluice in Bifuka,

Hokkaido, and concrete of the control reservation on the

Soksa Interchange of the Korean expressway. Figure 8

shows a location map, and Photo 1 illustrates the survey

situation. Both areas are located in severe environments

where temperatures fall below -20°C in the coldest season.

Bifuka

Sapporo Korea

SeoulSoksa

Bifuka Soksa

Fig. 8 Location map (left: Bifuka, Hokkaido; right: Soksa,

Korea)

Photo 1 Survey situation (left: Bifuka; right: Soksa)

0 100 200 300 400

150

100

50

0

y=0.29xy=0.23x+8.55

X0=138

Distance between emission and receiving sensors(mm)

Ultr

ason

ic s

prea

d tim

e(μ

sec) Vd=1/0.29=3.4km/sec

Vs=1/0.23=4.3km/secX0=138

t=24mm

River sluice (Bifuka)

y=0.43x

y=0.23x+31.4

X0=155

Vd=1/0.43=2.3km/secVs=1/0.23=4.3km/secX0=155

t=42mm

Control reservation (Soksa)

0 100 200 300 400

150

100

50

0

Excluded from analysis

Distance between emission and receiving sensors(mm)

Ultr

ason

ic s

prea

d tim

e(μ

sec)

Fig. 9 Results from the surface scanning method (top: Bifuka;

bottom: Soksa)

5.2 Results of measurement using the surface scanning

method

Figure 9 shows the results of measurement using the surface

scanning method at the control platform and on the control

reservation. Finding Vs and Vd from the slope of each line

and the distance from the origin to the inflection point (X0)

allowed the use of Eq. (1) to calculate the thickness of the

deteriorated area, which was found to be 24 mm on the

control platform and 42 mm on the control reservation

By replacing h with 10 mm in Eq. (4), the relative

dynamic modulus of elasticity at a depth of 10 mm was

calculated to be 74% on the control platform and 50% on the

control reservation. The modulus at the edge of the healthy

area was found to be 69% for the control panel as a result of

replacing h with 24 mm and 68% for the control reservation

by replacing it with 42 mm.

6. Conclusion

In this study, a simple frost damage diagnosis technique using

the theory of surface scanning was examined. The findings

can be summarized as follows:

(1) Surface scanning is effective as a nondestructive method

for estimating the thickness of the deteriorated area

affected by frost damage with a certain level of accuracy.

(2) The depth of the part where the relative dynamic modulus

of elasticity is lower than the value of the threshold (60%)

can be estimated from the slopes (between the origin and

inflection point and after the inflection point) of a graph

created using the results of surface scanning.

7. Afterword

In addition to developing the above simple frost deterioration

diagnosis approach involving the ultrasonic surface scanning

method, the authors intend to link it effectively with the

results obtained by the Material Research Team in the

previous year in order to perform future application of

ultrasonic measurement technology to the durability

evaluation of concrete affected by combined frost and salt

damage.

Specifically, the relationships with the ultrasonic

propagation velocity produced by using the ultrasonic

transmission method and the core strength8), coefficient of

chloride ion diffusion8) and crack density9) have been found

1.0 2.0 3.0 4.0 5.0

y=-0.0116x+0.0596(R2=0.4894)

0-28cycle (①：R2=0.6641)

50-100cycle100-200cycle

0

0.05

0.10

0.15

0.20

Cra

ck d

ensi

ty(N

umbe

r/m

m)

①

70

60

50

40

30

20

Sm

all-d

iam

eter

co

re c

om

pre

ssiv

e st

reng

th(M

Pa

)

2 3 4 5Ultrasonic propagation velocity(km/sec)

Laboratory acceleration testy=26.959x-37.56(R2=0.933)

1

80

Actual structurey=31.3x-75.21(R2=0.6482)

2 3 4 5

Laboratory acceleration testy=-4.5237x+27.259(R2=0.8366)

Actual structurey=-4.911x+22.846(R2=0.4159)

1

100

10

1

Coe

ffic

ien

t of

chlo

ride

ion

diff

usi

on(×

10-8

cm2 /

s)

Ultrasonic propagation velocity(km/sec)

Ultrasonic propagation velocity(km/sec)

Laboratory acceleration test

Actual structure

Fig. 10 Relationship of ultrasonic propagation velocity

found using the transmission method with core

compressive strength, coefficient of chloride ion

diffusion and crack density8), 9)

for specimens used in the laboratory freeze-thaw test in the

previous year and cores collected from actual sites as shown

in Fig. 10. We therefore plan to further examine their

relationship with ultrasonic waves using the surface scanning

method.

Finally, the authors aim to be able to ascertain the degree

of frost deterioration, strength, crack conditions and other

related information easily using the nondestructive ultrasonic

surface scanning method, as well as to use the technique for

prediction of salt penetration in freeze-thaw and high-salinity

environments.

Acknowledgment: The survey in Bifuka, Hokkaido, was

supported by the Hokkaido Regional Development Bureau,

and that in Soksa, Korea, was supported by Research

Professor Dr. Ann of Yonsei University and the Korea

Expressway Corporation. The survey in Korea was

conducted under Japan Science and Technology Agency

Financial Support (representative researcher: Professor Ph. D.

Tamon Ueda) and a priority project research of the Public

Works Research Institute financed by grants for expenses.

The authors would like to express their gratitude to all parties

concerned.

References

1) Chuji KASHIWA, Toyoki AKASHI and Yoshi

KOSAKA: Nondestructive Testing Methods for

Concrete – research papers, standards and literature in

Japan, Europe and the USA, p. 42, 1980.

2) Two-piece linear regression, Gunma University website

(http://aoki2.si.gunma-u.ac.jp/lecture/stats-by-excel/vba/

html/oresen-kaiki.html).

3) Nondestructive Testing for Concrete Structures, ed.,

Japanese Society for Nondestructive Inspection,

Yokendo, p. 130, 1994.

4) Hidehiko OGATA, Tsuguhiro NONAKA, Takao

FUJIWARA, Ryuichi TAKADA and Kunio HATTORI:

Frost Damage Diagnosis of Concrete Channel by

Ultrasonic Pulse Method, Proceedings of JCI

Symposium on Estimating Methods for Concrete

Performance to Freezing-Thawing Action, Japan

Concrete Institute, pp. 63 – 70, Dec. 2006.

5) Japan Society of Civil Engineers: 2007 Standard

Specifications for Concrete Structures [design], p. 123,

Mar. 2008.

6) Hirotake ENDOH, Fumio TAGUCHI, Hiroshi

HAYASHIDA and Shogo KUSAMA: Nondestructive

Diagnosis of Frost Depth, Report/symposium of the

Committee on Evaluation Methods for Freeze-Thaw

Resistance of Concrete, pp. 293 – 298, Aug. 2008.

7) Hiroshi HAYASHIDA, Fumio TAGUCHI, Hirotake

ENDOH and Shogo KUSAMA: Diagnosis of Frost

Damage in Concrete Structures by Measurement of

Ultrasonic Propagation Velocity, Proceedings of the 62nd

JSCE Annual Meeting, V-571, pp. 1141 – 1142, Sept.

2007.

8) FY 2008 Priority Project Report, Civil Engineering

Research Institute for Cold Region, 2009.

9) Fumio TAGUCHI, Hiroshi HAYASHIDA, Hirotake

ENDOH and Shogo KUSAMA: Evaluation of the

Relationship between the Ultrasonic Propagation

Velocity of Concrete Affected by Frost Damage and the

Number of Cracks, 63rd JSCE Annual Conference,

V-274, pp. 547 – 548, Sept. 2008.