Physical and Thermal Properties of Concrete Subjected to

Physical and thermal properties of concrete subjected to hightemperature

Shohei Sawada, Keiichi Miyamoto Takahiro Momma, ,Norichika Kakae

Journal of Advanced Concrete Technology, volume ( ), pp.15 2017 190-212

Hitoshi Kumagai, Yukiharu Ohga,Hideo Hirai, Tetsuo Abiru

Mechanical Properties of Concrete with Cooling Conditions After High Temperature HeatingGyu Yong Kim , Gyeong Choel Choe Yeon Woo Kang, , Tae Gyu LeeJournal of Advanced Concrete Technology, volume ( ), pp.12 2014 82-90

A Review of Research on the High Temperature Resistance of Concrete Structures in Chinese NPPJianzhuang Xiao , Wengang Xie Qinghai Xie,Journal of Advanced Concrete Technology, volume ( ), pp.14 2016 335-343

https://www.jstage.jst.go.jp/article/jact/12/3/12_82/_pdf

https://www.jstage.jst.go.jp/article/jact/14/7/14_335/_pdf

http://www.editorialmanager.com/jact/default.aspx

http://www.j-act.org/index.html

Journal of Advanced Concrete Technology Vol. 15, 190-212, June 2017 / Copyright © 2017 Japan Concrete Institute 190

Scientific paper

Physical and Thermal Properties of Concrete Subjected to High Temperature Norichika Kakae1, Keiichi Miyamoto2, Takahiro Momma3, Shohei Sawada4*, Hitoshi Kumagai5, Yukiharu Ohga6, Hideo Hirai7, and Tetsuo Abiru8

Received 26 February 2017, accepted 6 May 2017 doi:10.3151/jact.15.190

Abstract The physical and thermal properties of concrete under high temperature are obtained in order to provide reference data for material models necessary to evaluate the structural integrity of steel plate concrete containment vessels (SCCV) under accident conditions. Various parameters, such as temperature, heating duration, temperature history (heating, cooling, and the post-cooling process), water binder ratio, cement type, and aggregate type, are considered. Data on the temperature dependence of physical properties (compressive strength, elastic modulus, strain at compressive strength, splitting tensile strength) and thermal properties (thermal expansion strain, specific heat, thermal conductivity) are ob-tained from concrete of the same mix proportion. The effects of the variables on the properties of concrete are clarified, and the differences between test results and existing codes, such as the Eurocode, are highlighted.

1. Introduction

Steel plate reinforced concrete (SC) structures are a composite structure composed of steel plates and con-crete connected by shear connectors and/or tie-bars. It is suitable for prefabrication, so that reduced construction periods for nuclear facilities are expected. In Japan, structural design methods for SC structures under nor-mal temperature conditions have already been estab-lished and are applied to several SC structures in nu-clear power plants and facilities. With the aim to apply the SC structure to the primary containment vessel (PCV) of nuclear power stations, development of the steel plate concrete containment vessel (SCCV) (see Fig. 1) has been conducted in Japan for an advanced boiling light water reactor. The R&D project for SCCV was started in fiscal 2008 as a Japanese national project. Several experimental and analytical studies were per-formed in order to assess structural performance of SCCV (Ohga et al. 2015; Hirama et al. 2015; Narita et al. 2015; Kitajima et al. 2015; Okayasu et al. 2015).

Since SCCV is subjected to high temperature and high pressure in case of an accident, the structural integ-rity of SCCV should be maintained under accident con-

ditions. Figure 2 shows the temperature conditions un-der a design basis accident (DBA) and a severe accident (SA) assumed for the next-generation advanced boiling light water reactor in Japan. The highest temperature in case of DBA is set to 180°C during the initial phase of an accident. For SA, the highest temperature is set to 300°C and lasts for 30 days. The difference in assump-tions compared to existing boiling light water reactors is that the temperature is much higher and continues for a longer duration.

To approximately evaluate the performance of SCCV against accident loads, numerical analysis, which con-sists of heat transfer analysis and stress analysis, must be applied. The analyses often use material models, such as the Eurocode model (Eurocode 2004), which defines the physical and thermal properties of concrete and steel under high temperatures. Many research stud-ies related to the physical and thermal properties of concrete under high temperature have been conducted as reviewed elsewhere (Naus 2006, 2010; Architectural Institute of Japan 2009). However, only limited data (Kasami et al. 1975; Carette et al. 1982; DeFigh-Price et al. 1984; Nasser et al. 1985; Carrette and Molhorta 1985; Suzuki et al. 1995; Kanazu et al. 1996) have been identified related to the effects of long-term high tem-perature exposure on concrete properties. Carette et al. (1982) obtained physical properties of a limestone ag-gregate concrete after exposure to temperature ranging from 75°C to 600°C for a maximum eight months. Compressive strength and splitting tensile strength pro-portionally decreased with the increase of temperature, but no significance differences between one month ex-posure and four or eight months exposure were identi-fied. The investigations conducted by Suzuki et al. (1995) and Kanazu et al. (1996) also showed results that the decrease in compressive strength and elastic modulus at temperatures up to 110°C basically ended

1Senior Research Engineer, Kajima Corporation, Japan.2Chief Research Engineer, Kajima Corporation, Japan.3Senior Manager, Kajima Corporation, Japan. 4Deputy Senior Manager, Kajima Corporation, Japan. *Corresponding author, E-mail: [email protected] 5Chief Research Engineer, Shimizu Corporation, Japan.6Senior Engineer, Hitachi-GE Nuclear Energy, Ltd., Japan. 7Senior Specialist, Toshiba Corporation, Japan. 8Manager, The Chugoku Electric Power Co., Inc., Japan.

N. Kakae, K. Miyamoto, T. Momma, and S. Sawada, et al. / Journal of Advanced Concrete Technology Vol. 15, 190-212, 2017 191

after three months. Nasser et al. (1985) carried out a study to examine the effect of temperature on sealed and unsealed concrete containing fly ash. The compressive strength and elastic modulus were obtained under dif-ferent temperatures ranging from -11°C to 232°C and different exposure periods from 1 to 180 days. The strength and elastic modulus of sealed concrete gener-ally decreased proportional to the increase of tempera-ture and exposure period. In the case of unsealed con-crete, however, the strength increased in general up to 28 days, and thereafter, it decreased slightly but did not go below the non-exposure result. These results were obtained at room temperature after cooling from high temperature, and do not directly represent the properties of concrete at high temperature under accident condi-tions.

The aim of this study is to provide additional data

using Japanese concrete materials on the physical prop-erties of concrete heated for a long time. In this study, the concrete properties at the time of high temperature are obtained by the newly proposed test method (Kakae et al. 2013). In addition, the effects of various parame-ters, such as temperature, heating duration, temperature history (heating, cooling, and the post-cooling process), water binder ratio, cement type, and aggregate type, are examined. Thermal properties are also obtained from concrete of the same mix proportion used for physical property tests, so that extensive and comprehensive data related to concrete properties under high temperature, which can be reference data for material model neces-sary to evaluate structural integrity of SCCV under high temperature, are presented in this study. Some results of concrete properties up to 300 °C were already reported by Ohga et al. (2015).

2. Experimental details

The following properties that constitute the material model for numerical analyses are obtained under vari-ous test parameters. Physical property • Compressive strength • Elastic modulus • Strain at compressive strength • Splitting tensile strength Thermal property • Thermal expansion strain • Specific heat • Thermal conductivity 2.1 Test parameters The test variables are temperature, heating duration and

30.0m43.0m

2.0m 2.0m

2.2m

29.5m

：SCCV (Cylindrical steel plate concrete structure)

Reactor Pressure Vessel (RPV)

RPV Pedestal

Diaphragm Floor

Fig. 1 Outline shape of SCCV considered in the nest-generation advanced boiling light water reactor.

0

50

100

150

200

250

300

350

1.E-01 1.E+01 1.E+03 1.E+05 1.E+07

Tem

pera

ture

（

）

Time （sec）

DBA

SA

300

180

(0.8sec)

(0.8sec)

(30days)

104

52(3x106）

(30min)

(6hr) 85

Fig. 2 Temperature conditions assumed in accidents for the next-generation advanced boiling light water reactor in Japan.


temperature history (heating, cooling, and the post-cooling process), water binder ratio (W/B), cement, and aggregate type.

The temperature for physical properties and thermal expansion strain ranges from 100°C to 700°C. Specific heat and thermal conductivity are obtained up to 800°C. These highest experimental temperatures are determined beyond the maximum temperature (300°C) assumed for severe accidents for next-generation advanced boiling light water reactors in Japan. For heating duration, a duration of 35 days that is beyond the assumed maxi-mum period (30 days) of high temperature in a severe accident is set as the basic variable. In addition, various durations from 1 day to 216 days are employed in order to confirm the effect of heating duration. Temperature history (heating, cooling, and the post-cooling process) is also a variable for physical properties. With respect to temperature history, temperature is first increased to 500°C or 700°C and then decreased to 200°C and

100°C as shown in Fig. 3. Water binder ratios of 45% and 55% are used, which are typical for the concrete structures design for nuclear facilities. Portland fly ash cement and moderate heat Portland cement are used to reduce the heat of hydration for mass concrete in nu-clear structures, so that those two cements are used in addition to ordinary Portland cement. Sandstone and

Table 2 Test case (Thermal property test: Thermal expansion strain).

Cement*1 Aggregate W/B[%]

Temperature [°C] Curing condition Mixture Number of

specimenN Sandstone 55 100, 200, 300, 400, 500, 600, 700 Sealed N55G1G2-3 3 N Sandstone 45 100, 200, 300, 400, 500, 600, 700 Sealed N45G1G2 3

NF Sandstone 55 100, 200, 300, 400, 500, 600, 700 Sealed + underwater curing NF55G1G2 3 M Sandstone 55 100, 200, 300, 400, 500, 600, 700 Sealed + underwater curing M55G1G2 3 N Limestone 55 100, 200, 300, 400, 500, 600, 700 Sealed N55G3 3 N Limestone 45 100, 200, 300, 400, 500, 600, 700 Sealed N45G3 3

*1 N: Ordinary Portland Cement, NF: Ordinary Portland Cement with fly ash, M: Moderate Heat Portland Cement

Tempe

rature

[]

1minute

1 200

15days

100

35days 63days

500 or 700

91days

Heating Cooling Post-cooling

Fig. 3 Schematic of heating, cooling, and the post-cooling conditions.

Table 1 Test case (Physical property test).

Cement*1 Aggregate W/B [%]

Temperature [°C]

Heating Duration[day] Curing condition Mixture Number of

specimen 1, 2, 3, 7 Sealed N55G1G2-1 14, 35 Sealed N55G1G2-2 100

35, 63, 91, 216 Sealed N55G1G2-3 1, 2, 3, 7 Sealed N55G1G2-1 14, 35 Sealed N55G1G2-2 200

35 Sealed N55G1G2-3 1, 2, 3, 7 Sealed N55G1G2-1 14, 35 Sealed N55G1G2-2 300

35 Sealed N55G1G2-3 500 7, 35 Sealed N55G1G2-3 700 7, 35 Sealed N55G1G2-3

500

35, 63, 91 (heating, cooling,

and the post-cooling)

Sealed N55G1G2-3

N Sandstone 55

700

35, 63, 91 (heating, cooling,

and the post-cooling)

Sealed N55G1G2-3

3 for each heating duration

N Sandstone 45 100, 200, 300, 500, 700 35 Sealed+ underwater curing N45G1G2

NF Sandstone 55 100, 200, 300, 500, 700 35 Sealed+ underwater curing NF55G1G2

M Sandstone 55 100, 200, 300, 500, 700 35 Sealed M55G1G2 N Limestone 55 100, 200, 300, 500, 700 35 Sealed N55G3 N Limestone 45 100, 200, 300, 500, 700 35 Sealed N45G3

3 for each temperature



limestone are used as typical types of aggregates in Ja-pan. The details of test cases are shown in Table 1 through Table 4.

2.2 Materials Table 5 shows the materials used. Cement consists of two types—ordinary Portland cement and moderate heat Portland cement. Type II of JIS A 6201 fly ash is used for mineral admixture. For aggregates, natural sand, crushed sandstone and crushed limestone are used. Ta-ble 6 shows the concrete mix proportion used.

2.3 Specimens The shapes of the specimens are shown in Tables 7, according to the test apparatus used. The specimens for physical properties with a size of 100 mm diameter/200 mm height and 150 mm diameter/200 mm height are fabricated by the method specified in JIS A 1132. The specimens for the thermal expansion strain are the same shape (100 mm diameter/200 mm height) as the speci-mens for the compressive strength test. The specimens for specific heat with a size of 16 mm diameter/30 mm height are extracted by coring from 100 mm diameter size specimens after the specified period of curing and

Table 4 Test case (Thermal property test: Thermal conductivity).

Cement*1 Aggregate W/B [%] Method Temperature

[°C] Curing condition Mixture Number

of specimen

100, 200, 300, 400, 500, 600, 700, 800 Sealed + absolute-dried N55G1G2-3 3 20, 40, 70 Sealed N55G1G2-3 3 N Sandstone 55 GHP 20, 40, 70 Sealed + absolute-dried N55G1G2-3 1

100, 200, 300, 500, 800 Sealed + absolute-dried N45G1G2 1 20, 40, 70 Sealed N45G1G2 1 GHP 20, 40, 70 Sealed + absolute-dried N45G1G2 1 N Sandstone 45

Hot-wire 100, 200, 300, 400, 500, 600, 700, 800 Sealed + absolute-dried N45G1G2 3 100, 200, 300, 500, 800 Sealed + absolute-dried NF55G1G2 1

20, 40, 70 Sealed + underwater cur-ing

NF55G1G2 1 GHP

20, 40, 70 Sealed + absolute-dried NF55G1G2 1 NF Sandstone 55

Hot-wire 100, 200, 300, 400, 500, 600, 700, 800 Sealed + absolute-dried NF55G1G2 3 100, 200, 300, 500, 800 Sealed + absolute-dried M55G1G2 1

20, 40, 70 Sealed + underwater cur-ing

M55G1G2 1 GHP

20, 40, 70 Sealed + absolute-dried M55G1G2 1 M Sandstone 55

Hot-wire 100, 200, 300, 400, 500, 600, 700, 800 Sealed + absolute-dried M55G1G2 3 100, 200, 300, 500, 800 Sealed + absolute-dried N55G3 1

20, 40, 70 Sealed N55G3 1 GHP 20, 40, 70 Sealed + absolute-dried N55G3 1 N Limestone 55

Hot-wire 100, 200, 300, 400, 500, 600, 700, 800 Sealed + absolute-dried N55G3 3 100, 200, 300, 500, 800 Sealed + absolute-dried N45G3 1

20, 40, 70 Sealed N45G3 1 GHP 20, 40, 70 Sealed + absolute-dried N45G3 1 N Limestone 45

Hot-wire 100, 200, 300, 400, 500, 600, 700, 800 Sealed + absolute-dried N45G3 3 *1 N: Ordinary Portland Cement, NF: Ordinary Portland Cement with fly ash, M: Moderate Heat Portland Cement

Table 3 Test case (Thermal property test: Specific heat).

Cement*1 Aggregate W/B [%]

Temperature [°C]

Curing condition Mixture Number of specimen

N Sandstone 55 20～800 Sealed N55G1G2-3 3 20～800 Sealed N45G1G2 3 N Sandstone 45 20～800 Sealed + absolute-dried N45G1G2 1 20～800 Sealed + underwater curing NF55G1G2 3 NF Sandstone 55 20～800 Sealed + absolute-dried NF55G1G2 1 20～800 Sealed + underwater curing M55G1G2 3 M Sandstone 55 20～800 Sealed + absolute-dried M55G1G2 1 20～800 Sealed N55G3 3 N Limestone 55 20～800 Sealed + absolute-dried N55G3 1 20～800 Sealed N45G3 3 N Limestone 45 20～800 Sealed + absolute-dried N45G3 1



then cut to the specified height. It is confirmed that specimens are free from defects (cracking, chipping, non-uniform distribution of the aggregate, etc.) and mass per unit volume for all specimens is almost con-stant (e.g. 2.34 g/cm3 for N55G1G2-3) and nearly iden-tical to the 100 mm diameter size specimen (e.g. 2.33 g/cm3 for N55G1G2-3). The specimens for thermal conductivity are fabricated according to JIS A 1412-1 and JIS R 2616 for the Guarded hot plate (GHP) method and hot-wire method, respectively.

Degree of hydration is very important for the heating test because insufficient hydration can affect the physi-cal properties of concrete under high temperature, i.e. increase of strength due to promotion of hydration by heating. Two curing methods are used depending on cement type. Specimens using ordinary Portland cement

(N55G1G2, N45G1G2, N55G3, and N45G3) are cured in the mold sealed in the plastic film at 20°C for two weeks. After demolded, the specimens are sealed in an aluminum bag and cured until the date of the test at 20°C for at least 91 days. For specimens using fly ash and moderate heat Portland cement (NF55G1G2 and M55G1G2), underwater curing is employed to acceler-ate hydration because hydration of those specimens is slow. After remaining sealed in the mold by plastic film and maintained at 20°C for four weeks, the specimens are demolded and cured in water at a temperature of 30˚ C for 11 months (sealed + underwater curing).

Some of the specimens for measurements of specific heat and thermal conductivity are dried at a temperature of 105°C in an electric oven for more than 24 hours to achieve an absolute dried condition before testing.

Table 7 Shape of specimen. Test type Properties obtained Shape of specimen [mm]

Compressive Strength Elastic modulus Strain at compressive strength

φ100×200 Physical Property Test

Splitting Tensile Strength φ150×200 Thermal Expansion Strain φ100×200 Specific Heat φ16×30 Thermal Conductivity (below 100°C、GHP Method) 300×300×50 Thermal Conductivity (above 100°C、GHP Method) φ300×50

Thermal Property Test

Thermal Conductivity (above 100°C、Hot-wire Method) 200×100×50 φ: diameter

Table 5 Materials. Materials Notation Property

N Ordinary Portland cement; density, 3.16g/cm3; Blaine, 3190-3200cm2/g Cement M Moderate-heat Portland cement; density, 3.21g/cm3; Blaine, 3250cm2/g Mineral admixture FA JIS A6201 Fly ash II; density, 2.28g/cm3; Blaine, 4420cm2/g

S1 Naturel Sand; density, 2.59g/cm3; absorption, 2.42-2.44% Fine aggregate S2 Crushed sandstone; density, 2.62-2.64g/cm3; absorption, 1.10-1.42% G1 Crushed sandstone; Max. size, 20 mm; density, 2.65g/cm3; absorption, 0.43-0.49% G2 Crushed sandstone, Max. size, 15mm; density, 2.64g/cm3; absorption, 0.59-0.61% Coarse aggregate G3 Crushed limestone, Max. size, 20 mm; density, 2.70g/cm3; absorption, 0.63% ad1 Air-entraining and high range water-reducing admixture ad2 Air entraining agent Chemical admixture ad3 Air adjusting agent

Table 6 Mix proportions of concrete.

Unit mass(kg/m3) Binder B

Cement CFine aggregate

S Coarse aggregate

G

Chemical admixture (B×%) Mixture W/B

(%) s/a*2 (%)

FA/C (%) Water

W N M FA S1 S2 G1 G2 G3 ad1 ad2 ad3 N55G1G2-1*1 55 48.7 0 175 318 0 0 261 610 373 560 0 3.811 0 0.633N55G1G2-2*1 55 48.7 0 175 318 0 0 261 609 415 507 0 3.498 0 0.318N55G1G2-3*1 55 48.7 0 175 318 0 0 261 609 417 510 0 0.95 0.0035 0.01

N45G1G2 45 48.7 0 165 367 0 0 257 600 417 510 0 1.30 0.0050 0.01 NF55G1G2 55 48.8 18.5 170 252 0 57 263 614 417 510 0 0.80 0.0150 0.01 M55G1G2 55 48.8 0 175 0 318 0 263 615 417 510 0 0.80 0.0055 0.01

N55G3 55 48.8 0 175 318 0 0 263 613 0 0 947 0.90 0.0070 0.01 N45G3 45 48.3 0 165 367 0 0 258 602 0 0 947 1.20 0.0070 0.01

*1: Slightly different mix proportions are used due to different timing of casting. *2: Sand (fine aggregate) total aggregate ratio


2.4 Test procedures 2.4.1 Physical property test (1) Compressive strength, elastic modulus, and strain at compressive strength Tests for obtaining physical properties of concrete can be generally categorized to hot or cold testing. A hot test is conducted with maintaining the specified high tem-perature and can obtain relative physical properties (high temperature properties). Whereas the cold test is conducted at the ambient temperature after cooling from high temperature and can obtain residual physical prop-erties (post high temperature properties). The hot test normally uses a compression test apparatus, which is attached to an electric oven. This apparatus can provide relative physical properties; however, the test is time consuming because only one test case (heating + load-ing) at a time can be conducted. It is difficult to conduct many long-term heating tests. The method employed in this study (Kakae et al. 2013), described below, can provide relative physical properties of many test cases within a reasonably short time.

The specimens are placed in the programmable elec-tric oven after its mass and dimensions (diameter and height) are measured. The heat insulation (ceramic fiber blanket) is also placed in the oven and heated with the specimen. The specimen is kept heated for the specified period of time in an unsealed condition. The start point of heating duration is defined as the core temperature of the specimen, which is measured in advance by an em-bedded thermocouple in the center of another specimen, reaches the specified temperature as shown in Fig. 4. After the specified heating duration, the specimens are taken from the oven and brought to the test apparatus. In order to minimize the temperature decrease, the speci-mens are wrapped with heated insulation and encapsu-lated in a stainless steel container during transport. Im-mediately after the specimen is removed from the con-tainer, the mass of the specimen is measured and the specimen is set up in the Amsler type compression test apparatus with the compression meter installed as shown in Fig. 5. The compression meter comprises two displacement gages connected to both sides of the specimen; the axial strain is measured as the average of the readings by two displacement gages. The tests are conducted according to the JIS A 1108. Total time nec-essary to conduct test after the specimen is taken from the oven is within 5 minutes. Elastic modulus is calcu-lated according to the JIS A 1149, i.e. it is obtained as the secant stiffness at 1/3 strength in a stress-strain curve.

(2) Splitting tensile strength The test procedure is the same as the test described in section 2.4.1 (1) before the loading test. Splitting tensile strength is measured according to JIS A 1113 using the Amsler type compression tester shown in Fig. 6. The maximum load is measured and the splitting tensile strength is calculated according to JIS A 1113. Most

previous tests determined the residual tensile strength, which is obtained after specimens are cooled from the specified high temperature to ambient, since conducting the tensile test under high temperature is difficult. This test however can obtain relative tensile strength by the test procedures described above. 2.4.2 Thermal property test (1) Thermal expansion strain Thermal expansion strain is measured using the appara-tus shown in Fig. 7. The strain of the specimen is meas-ured by the displacement gages connecting the silica glass rods that are attached on the surface of the center of the specimen. The electric oven can control the inside temperature according to the preprogrammed heating

Specimen

Displacement gage

Fig. 5 Configuration of compressive strength test.

Specimen

Displacement gage

Specimen

Fig. 6 Configuration of splitting tensile strength test.

Start point of the heating duration1

Time differences of surface and core temperature

Tempe

rature

[]

1minute

Time

Surface temperature

Core temperature

Fig. 4 Schematic of heating temperature and duration (Physical property test).


curve. The thermocouple is used to measure the tem-perature of the specimen allowing simultaneous meas-urement of strain and temperature. Heating is applied at a rate of 1°C/min up to 700°C and 90 minutes of ther-mally equalizing period is applied at each 100°C step to avoid large temperature differences between the surface and the core of the specimen as shown in Fig. 8. The time of 90 minutes is determined in advance by an em-bedded thermocouple in the center of another specimen. (2) Specific heat The specific heat is measured by the adiabatic continu-ous method where measurement is made by heating the specimen to the specified temperature in the adiabatic condition. Specific heat can be obtained by the follow-

ing equation.

pW t M CCM Mθ

′ ′×Δ ×= −

×Δ

where Δt [s] is the time required for temperature to rise by infinitesimal value of Δθ [K], M [g] is the mass of the specimen, W [W] is constant power in the adiabatic condition, M’ [g] is mass of the specimen holder and C’ [J/g/K] is specific heat of the specimen holder. (3) Thermal conductivity Thermal conductivity test is conducted according to the two methods of JIS A 1412-1 (GHP Method) and JIS R 2616 (Hot-wire Method). In the GHP method, two specimens are placed between one heating plate and two cooling plates as shown in Fig. 9. Heat is applied until the steady state condition is reached. Thermal conduc-tivity is calculated with electrical power supplied to maintain the steady state condition and the temperature difference between the heated and the cooled surface of the specimen by the following equation.

1 2( )d

A T Tφλ ×

=× −

where φ [W] is the average electrical power applied to the heating plate, d [m] is the average thickness of the specimen, A [m2] is the contact surface area between the heating plate and the specimen, T1 [K] is the average temperature of the specimen at high temperature side, and T2 [K] is the average temperature of the specimen at low temperature side.

In the hot-wire method, the heating wire is placed between two specimens as shown in Fig. 10. Thermal conductivity can be obtained by the following equation when amount of electrical current for given time inter-val of Δt(t2-t1) and temperature of the hot wire at time t1 and t2 are measured.

Specimen

Heater

Ceramic insulator

Fig. 7 Schematic of thermal expansion strain test.

Time

Tem

pera

ture

[

]

1minute

1

t_100

700

t_300t_400

t_500t_600t_200

t_700

Fig. 8 Schematic of heating temperature and duration (Thermal expansion strain test).

Hot‐wire

Specimen

Fig. 10 Configuration of hot-wire method.

Hot PlateSpecimen

Cool Plate

Cool Plate Fig. 9 Configuration of GHP method.


22 1

2 1

( / )4

ln t tI Rλπ θ θ×

= ×× −

where, I [A] is the value of current supplied to the hot wire, R [Ω/m] is resistivity of the hot wire, θ1 [°C] and θ2 [°C] are temperature of the hot wire at t1 [min] and t2 [min]. 3. Results and discussions

3.1 Physical properties 3.1.1 Results at room temperature Figure 11 shows the compressive strength, elastic modulus, strain at compressive strength, and splitting tensile strength obtained at room temperature for specimens made of different mix proportions shown in

Table 6. Tests are conducted according to the same pro-cedures (without heating) described in sections 2.4.1 and 2.4.2. The error bar shows one standard deviation. The values shown in Fig. 11 are used to calculate the relative ratio of high temperature properties to room temperature properties in subsequent sections. 3.1.2 Influence of test procedures Figure 12 shows the variation in the compressive strength ratio and elastic modulus ratio at a temperature of 200°C with time elapsed after specimens were re-moved from the oven. Compressive strength ratio and elastic modulus ratio are calculated by normalizing test results at 200°C to those at room temperature. The core temperature of the specimen drops to approximately 180°C by placing at room temperature for 90 minutes

01020304050607080

Com

pres

sive

stre

ngth

[N/m

m2 ]

0

10

20

30

40

50

60El

astic

mod

ulus

[kN

/mm

2 ]

(a) Compressive strength (b) Elastic modulus

0

500

1000

1500

2000

2500

3000

3500

Stra

inat

com

pre

sive

stre

ngth

[×10

-6]

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Split

ting

tesi

lest

reng

th[N

/mm

2 ]

(c) Strain at compressive strength (d) Splitting tensile strength

Fig. 11 Physical properties at room temperature for specimens made of different mix proportions.

0

0.2

0.4

0.6

0.8

1

1.2

0 30 60 90 120

Com

pres

sive

stre

ngth

ratio

[－]

Elapsed time (minute)

0

0.2

0.4

0.6

0.8

1

1.2

0 30 60 90 120

Ela

stic

mod

ulus

ratio

[－]

Elapsed time (minute) Fig. 12 Variation of compressive strength ratio and elastic modulus ratio at a temperature of 200°C with the time elapsed after specimens were removed from the oven.


(see Fig. 13); however, the compressive strength ratio and elastic modulus ratio are almost the same. Figure 12 shows the compressive strength ratio and elastic modulus ratio are almost unchanged regardless of the elapsed time up to 90 minutes. As mentioned in section 2.4.1, all physical property tests were completed within about 5 minutes after specimens were removed from the oven. Therefore, the test procedure is acceptable, and the results are considered to be sufficiently reliable on physical properties of concrete under high temperature obtained in this study.

3.1.3 Effect of heating temperature The typical compressive stress-strain relations of the specimen made of N30G1G2-3 (W/B55%, Ordinary Portland cement, Sandstone) under various temperature are shown in Fig. 14. Heating duration for all specimens shown in this section is 35 days. Figure 14 indicates that compressive strength and elastic modulus decrease with the increase in heating temperature; however, the strain at compressive strength increases. These trends are more clearly shown in Fig. 15. The compressive strength ratio relatively decreases more rapidly after 300°C. For the elastic modulus ratio, it decreases to 0.6

0

10

20

30

40

50

60

70

0 2000 4000 6000 8000 10000 12000

Stre

ss [N

/mm

2 ]

Strain [×10-6]

N55G1G2-3

Room temperature

100200

300

500

700

Fig. 14 Typical compressive stress – strain relations un-der various temperature (W/B55%, Ordinary Portland cement, Sandstone, Heating duration 35days).

0

50

100

150

200

250

0 30 60 90 120

Elapsed time (minute)

Tem

pera

ture

of o

core

of s

peci

men

[]

Fig. 13 Variation of temperature of core of specimen heated at 200°C with the time elapsed after specimens were removed from the oven.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800Com

pres

sive

stre

ngth

ratio

[－]

Temperature []

N55G1G2-2N55G1G2-3

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Elas

ticm

odul

usra

tio[－

]

Temperature []

N55G1G2-2N55G1G2-3

(a)Compressive strength ratio (b) Elastic modulus ratio

010002000300040005000600070008000

0 100 200 300 400 500 600 700 800Temperature []

N55G1G2-2N55G1G2-3

Stra

inat

com

pres

sive

stre

ngth

[×10

-6]

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800Split

ting

tesi

lest

reng

thra

tio[－

]

Temperature []

N55G1G2-2N55G1G2-3

(c) Strain at compressive strength (d) Splitting tensile strength ratio Fig.15 Temperature dependence of physical properties of concrete (W/B55%, Ordinary Portland cement, Sandstone, Heating duration 35 days).


at 100°C and 0.1 at 700°C. The strain at compressive strength steadily increases with temperatures up to 700°C. The splitting tensile strength ratio decreases with temperature similarly as the compressive strength ratio. Comparing to the previous research that obtained resid-ual properties of concrete (W/C50-60%, Ordinary Port-land cement, River gravel) subjected to high tempera-ture up to 300°C for 90 days (Kasami et al. 1975), the present results show similar temperature dependence trend, but the results of the compressive strength ratio and splitting tensile strength ratio show slightly greater values. 3.1.4 Effect of heating duration The compressive strength ratio with heating duration at temperature 100°C to 700°C for the specimen made of N55G1G2-1~3 (W/B55%, Ordinary Portland cement, Sandstone) are shown in Fig. 16. Figure 16(a) shows that the effect of heating duration is not significant up to 35 days except for the heating temperature of 100°C for less than seven days. The compressive strength ratio is recovered to 1.0 after seven days when the heating temperature is 100°C; however, for less than seven days, the compressive strength ratio is smaller than 1.0. It is also confirmed that the compressive strength ratio re-mains virtually unchanged at 1.0 even with a 216 days (seven months) long heating duration at a temperature of 100°C as shown in Fig. 16(b).

Figure 17 shows the variation of elastic modulus ra-tio with heating duration. Figure 17(a) shows elastic modulus ratio is almost constant and not much affected by the heating duration. The results obtained from longer heating duration at a temperature of 100°C shows that the elastic modulus remains consistent at about 0.6 even when the heating duration extends to as long as 216 days (7 months) (Fig. 17(b)).

Figure 18 shows the variation of splitting tensile strength ratio with heating duration. The results are slightly more scattered than the results of concrete strength ratio. The effect of heating duration is not sig-nificant except for the heating temperature of 100°C for less than 14 days and 200°C for less than seven days.

The tendency that concrete properties at high tem-perature remain virtually unchanged after initial heating phase (seven days for compressive strength and 14 days for splitting tensile strength) corresponds to the previous results obtained at room temperature after cooling (Su-zuki et al. 1995; Kanazu et al. 1996). A different trend for the compressive strength ratio obtained at a tem-perature of 100°C up to seven days and the splitting tensile strength ratio obtained at a temperature of 100°C and 200°C up to 14 days may relate to equilibrium state of water content in the concrete. The variation of the mass reduction ratios (i.e. ratio of changes in mass per initial mass of specimens) with heating duration up to 35 days is shown in Fig. 19. The mass reduction ratios

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40

Com

pres

sive

stre

ngth

ratio

[－]

Heating duration [days]

100(N55G1G2-1,2)

200(N55G1G2-1,2)

300(N55G1G2-1,2)

500(N55G1G2-3)

700(N55G1G2-3)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 60 120 180 240

Com

pres

sive

stre

ngth

ratio

[－]

Heating Duration [day]

100(N55G1G2-3)

(a) Heating duration of 1-35 days (b) Heating duration of 35-216 days

Fig.16 Variation of compressive strength ratio with heating duration (W/B55%, Ordinary Portland cement, Sandstone).

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40

Ela

stic

mod

ulus

ratio

[－]

Heating Duration [days]

100(N55G1G2-1,2)

200(N55G1G2-1,2)

300(N55G1G2-1,2)

500(N55G1G2-3)

700(N55G1G2-3)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 60 120 180 240

Elas

tic m

odul

us ra

tio[－

]


100(N55G1G2-3)

(a) Heating duration of 1-35 days (b) Heating duration of 35-216 days

Fig. 17 Variation of elastic modulus ratio with heating duration (W/B55%, Ordinary Portland cement, Sandstone).


are virtually consistent, except for the heating tempera-ture of 100°C and 200°C for less than 7 days. These tendencies correspond to the variation of compressive strength ratios and splitting tensile strength ratios as shown in Fig. 16(a) and Fig. 18(a). Figure 20 shows the variation of compressive strength, elastic modulus, and splitting tensile strength ratios with mass reduction ratio for a heating duration of 35 days. The compressive and splitting tensile strength ratios increase as the mass reduction ratio approaches the absolute-dried condition in which the mass reduction ratio is about 6.0% by weight, and then decrease with increase of the mass reduction ratio. As mentioned in Kishitani et al. (1982) and Kakae et al. (2013), it is considered that the strength of concrete may be influenced by the equilibrium state of water content in the concrete. The compressive and splitting tensile strength may become small when the absolute-dried condition of the concrete is not reached (i.e. the free water in the concrete is not sufficiently removed), since internal pressure by water vapor may have a negative impact on the strength of concrete. The elastic modulus may not be influenced by the equilib-rium state of water content, since elastic modulus ratios proportionally decrease with increase of the mass reduc-tion ratio as shown in Fig. 20(b).

3.1.5 Effect of temperature history The effect of temperature history (heating, cooling, and the post-cooling process) is shown in Fig. 21, in which the results of the specimens without cooling are also plotted. Regardless of cooling process, compressive strength ratio is almost consistent, except for the results of the specimens subjected to 100°C (91 days) when heated to 700°C. Strain at compressive strength slightly decreases in the case of 500°C; however, a greater in-crease in strain is shown in specimens subjected to 100°C (91 days) when heated to 700°C. The elastic modulus ratio of the specimens heated at 500°C seems to be not affected by the cooling process; however, in the case of 700°C, they gradually decrease. Especially, the result of the specimens subjected to 100°C (91days) when heated to 700°C shows extremely small values. The splitting tensile strength ratio seems to be affected by the cooling process, since they gradually decrease according to the cooling process.

The decrease tendency of the elastic modulus ratio and the splitting tensile strength ratio may relate to the effect of dehydration of the calcium hydroxide followed by expansive rehydration of lime after cooling that oc-curs with time as mentioned by Khoury (1992) and Mendes et al. (2008 and 2009). By visual inspection conducted before the strength test of the specimens subjected to 100°C (91 days) when heated to 700°C,

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0 10 20 30 40

Mas

s re

duct

ion

ratio

[－]


100 200 300 500 700

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0 10 20 30 40

Mas

s re

duct

ion

ratio

[－]


100 200 300 500 700

(a) φ100 × 200 specimens (b) φ150 × 200 specimens Fig. 19 Variation of mas reduction ratio with heating duration (1-35 days) (W/B55%, Ordinary Portland cement, Sand-stone).

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40

Spl

ittin

g te

nsile

stre

ngth

ratio

[－]


100(N55G1G2-1,2)

200(N55G1G2-1,2)

300(N55G1G2-1,2)

500(N55G1G2-3)

700(N55G1G2-3)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 60 120 180 240

Split

ting

tens

ile s

treng

th ra

tio[－

]


100(N55G1G2-3)

(a) Heating duration of 1-35 days (b) Heating duration of 35-216days Fig. 18 Variation of splitting tensile strength ratio with heating duration (W/B55%, Ordinary Portland cement, Sandstone).


which shows a notable decrease in the elastic modulus and an increase in strain at compressive strength, clearer expansion of cracks on the specimen surface is observed. In addition, larger mass gain is also observed in those

specimens subjected to a longer post cooling period (Fig. 22). According to the results of X-ray diffraction (XRD) of the specimen, the clear peak of calcium hydroxide (Ca(OH)2) that is not observed in other specimens is

0.00

0.20

0.40

0.60

0.80

1.00

1.20

withoutcooling

to 200（35days）

to 100（63days）

to 100（91days）

Com

pres

sive

stre

ngth

ratio

[－]

500700

0.00

0.20

0.40

0.60

0.80

1.00

1.20

withoutcooling

to 200（35days）

to 100（63days）

to 100（91days）

Elas

ticm

odul

usra

tio[－

] 500700

(a) Compressive strength ratio (b) Elastic modulus ratio

0

2000

4000

6000

8000

10000

12000

withoutcooling

to 200（35days）

to 100（63days）

to 100（91days）

500700

Stra

inat

com

pres

sive

stre

ngth

[×10

-6]

0.00

0.20

0.40

0.60

0.80

1.00

1.20

withoutcooling

to 200（35days）

to 100（63days）

to 100（91days）

Spl

ittin

gte

nsile

stre

ngth

ratio

[－]

500700

(c) Strain at compressive strength (d) Splitting tensile strength ratio

Fig. 21 Effect of post heating process (W/B55%, Ordinary Portland cement, Sandstone).

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.03 0.05 0.07 0.09 0.11 0.13

Com

pres

sive

stre

ngth

ratio

[－]

Mass reduction ratio [－]

100200300500700

noitidnocyrdetulosbA

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.03 0.05 0.07 0.09 0.11 0.13

Elas

ticm

odul

usra

tio[－

]


100200300500700

noitidnocyrdetulosbA

(a) Compressive strength (b) Elastic modulus

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.03 0.05 0.07 0.09 0.11 0.13

Spl

ittin

g te

nsile

stre

ngth

ratio

[－]


100200300500700

Absolute dry condition

(c) Splitting tensile strength

Fig. 20 Variation of compressive strength, elastic modulus and splitting tensile strength ratio with mass reduction ratio (W/B55%, Ordinary Portland cement, Sandstone).


detected as shown in Fig. 23. The content of Ca(OH)2 calculated by the results of thermogravimetry-differential thermal analysis (TG-DTA) also increases (Table 8). Ca(OH)2 may be generated by the reaction of CaO, which comes from the decomposition of cement hydrate by heating to 700°C, with water absorbed from the at-mosphere during the long cooling process. The expan-sion of Ca(OH)2 generated by such a reaction may cause

wider cracks resulting in the smaller stiffness of the specimens that are cooled to 100°C (91 days). Since the compressive strength ratio is almost unchanged, the stiffness and splitting tensile strength of the concrete may be more susceptible to cracks generated during the cooling process than compressive strength.

3.1.6 Effect of water binder ratio, type of cement and type of aggregate The effects of the water binder ratio on temperature de-pendence of physical properties are shown in Figs 24 and 25. In both sandstone and limestone concretes, the effect of water binder ratio seems to be not significant. These results are similar to previous research studies

5 10 15 20 25 30 35 40 45 50 55 602θ（°）

700 witout cooling700 to 100（63days）700 to 100（91days）

CaO↓

Ca(OH)2↓

CaO↓

Fig. 23 XRD charts of specimens heated at temperature 700°C (W/B55%, Ordinary Portland cement, Sandstone).

0.88

0.89

0.90

0.91

0.92

0 20 40 60 80 100

Wei

ghtr

atio

[-](a

fterh

eatin

g/b

efor

ehe

atin

g)


witout cooling

with cooling

Fig. 22 Variation of weight ratio of specimens heated at temperature 700°C with heating duration (W/B55%, Or-dinary Portland cement, Sandstone).

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Com

pres

sive

stre

ngth

ratio

[－]

Temperature []

W/B55%(N55G1G2-3)W/B45%(N45G1G2)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Elas

tic m

odul

us ra

tio[－

]

Temperature []

W/B55%(N55G1G2-3)W/B45%(N45G1G2)


0

2000

4000

6000

8000

10000

0 100 200 300 400 500 600 700 800

Stra

in a

t com

pres

sive

stre

ngth

[×10

-6]

Temperature []

W/B55%(N55G1G2-3)W/B45%(N45G1G2)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800Split

ting

tens

ile s

treng

th ra

tio[－

]

Temperature []

W/C55%(N55G1G2-3)

W/C45%(N45G1G2)


Fig. 24 Effect of water binder ratio (Sandstone).

Table 8 Ca(OH)2 content calculated by TG-DTA. Case Ca(OH)2 content (mass %)

700°C without cooling 0.8 700°C to 100°C (63days) 1.0 700°C to 100°C (91days) 8.2


(Khoury 1983; Castillo and Durrani 1990; Nagao and Nakane 1991; Arioz 2007), which indicate that the ef-fect of water cement ratio had little influence on resid-ual concrete physical properties.

The effects of cement type on temperature depend-ence of physical properties are shown in Fig. 26. The results of specimens made of ordinary Portland cement and specimens made of moderate heat Portland cement

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Com

pres

sive

stre

ngth

ratio

[－]

Temperature []

N(N55G1G2-3)M(M55G1G2)NF(NF55G1G2)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Elas

tic m

odul

us ra

tio[－

]

Temperature []



0

2000

4000

6000

8000

10000

0 100 200 300 400 500 600 700 800

Stra

in a

t com

pres

sive

stre

ngth

[×10

-6]

Temperature []


0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Split

ting

tens

ile s

treng

th ra

tio[－

]

Temperature []



Fig. 26 Effect of type of cement.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Com

pres

sive

stre

ngth

ratio

[－]

Temperature []

W/B55%(N55G3)W/B45%(N45G3)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Elas

tic m

odul

us ra

tio[－

]

Temperature []

W/B55%(N55G3)W/B45%(N45G3)


0

2000

4000

6000

8000

10000

0 100 200 300 400 500 600 700 800

Stra

in a

t com

pres

sive

stre

ngth

[×10

-6]

Temperature []

W/B55%(N55G3)W/B45%(N45G3)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Spl

ittin

g te

nsile

stre

ngth

ratio

[－]

Temperature []

W/B55%(N55G3)W/B45%(N45G3)


Fig. 25 Effect of water binder ratio (Limestone).


are almost identical. However, in the case of specimens made of ordinary Portland cement with fly ash, the de-crease tendency of physical properties depending on temperature is more significant than other types of ce-ment. In particular, decreases of compressive strength and splitting tensile strength are significant. Recently, the investigations related to the residual physical prop-erties of concrete containing fly ash subjected to high temperature were carried out and showed that the fly ash improved the performance of concrete at high tem-perature (Xu et al. 2001; Poon et al. 2001 and 2003; Li et al. 2004; Raju et al. 2004). However, periods of cur-ing before the heating test were not long enough (from 1 to 3 months) in these studies, so concrete strength might improve due to the effect of autoclave curing. As results obtained from the sufficiently hydrated specimens, Sar-shar et al. (1993) conducted high temperature tests us-ing cement paste specimens kept at 100% RH for at least one year before testing. In this study, specimens with fly ash showed greater compressive strength ratios than that made of ordinary Portland cement only. Sar-shar et al. (1993) suggested that this may be explained by the different calcium hydroxide content, i.e. the de-crease of compressive strength becomes significant at temperature above 300°C owing to increased micro cracking around the calcium hydroxide crystals, so fly ash cement paste which contains less calcium hydroxide showed better performance. The results shown in Fig. 26 indicate that the temperature dependence of the physical properties of concrete with fly ash shows an

opposite tendency in the case of cement paste. The dif-ferent results between concrete and cement paste may be related to the fact that the accumulated damage caused by differences in volume changes between the aggregate and mortar is an important role in the physical property change of concrete under drying and heating conditions as mentioned by Maruyama et al. (Maru-yama et al. 2014) .

The effect of the aggregate type on the physical prop-erties is shown in Figs 27 and 28. Sandstone concrete and limestone concrete show almost similar temperature dependencies of the physical properties, except that the compressive strength and splitting tensile strength of limestone concrete are smaller at 500°C. Harada et al. (1972) showed that the tensile strength ratio of the lime-stone aggregate concrete exhibited larger reductions than sandstone aggregate concrete, but Arioz (2007) and Hertz (2005) stated that a concrete made with limestone suffers less damage than a siliceous concrete. As de-scribed in subsequent section 3.2.1 (see Fig. 31), the thermal expansion strain of limestone concrete becomes larger than that of sandstone concrete above 500°C. The thermal expansion strain of limestone has large anisot-ropy (Kitano et al. 1988), so the micro damage of inter-face between mortar and aggregate, which is caused by the difference in the thermal expansion of limestone used in this study at a temperature of 500°C may result in a decrease in the strength of limestone concrete.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Com

pres

sive

stre

ngth

ratio

[－]

Temperature []

Sandstone(N55G1G2-3)Limestone(N55G3)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Ela

stic

mod

ulus

ratio

[－]

Temperature []



0

2000

4000

6000

8000

10000

0 100 200 300 400 500 600 700 800

Stra

in a

t com

pres

sive

stre

ngth

[×10

-6]

Temperature []


0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Split

ting

tens

ile s

treng

th ra

tio [－

]

Temperature []



Fig. 27 Effect of type of aggregate (W/B55%).


3.2 Thermal properties 3.2.1 Thermal expansion strain Figures 29 through 31 show thermal expansion strain with many parameters. The thermal expansion strain increases with the increase in temperature. Thermal ex-pansion strain results versus temperature for limestone aggregate having water binder content of 45% and 55% are similar, however, the results for sandstone aggregate concrete indicate that the thermal expansion strain at a comparable temperature for a water binder of 0.45 are greater than values for a water binder of 0.55. The re-sults for ordinary Portland cement and moderate heat Portland cement are almost consistent; however, the fly ash results are relatively greater. The thermal expansion strain with limestone aggregate increases more at a

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Com

pres

sive

stre

ngth

ratio

[－]

Temperature []

Sandstone(N45G1G2)Limestone(N45G3)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Elas

tic m

odul

us ra

tio[－

]

Temperature []



0

2000

4000

6000

8000

10000

0 100 200 300 400 500 600 700 800

Stra

in a

t com

pres

sive

stre

ngth

[×10

-6]

Temperature []


0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Spl

ittin

g te

nsile

stre

ngth

ratio

[－]

Temperature []



Fig. 28 Effect of type of aggregate (W/B45%).

0

2000

4000

6000

8000

10000

12000

14000

0 100 200 300 400 500 600 700 800

Ther

mal

expa

nsio

nst

rain

[×10

-6］

Temperature ［］

W/B55%W/B45%

0

2000

4000

6000

8000

10000

12000

14000

0 100 200 300 400 500 600 700 800

Ther

mal

expa

nsio

nst

rain

[×10

-6］

Temperature ［］

W/B55%W/B45%

(a) Sandstone (b) Limestone

Fig. 29 Temperature dependence of thermal expansion strain (Effect of water binder ratio).

0

2000

4000

6000

8000

10000

12000

14000

0 100 200 300 400 500 600 700 800

Ther

mal

expa

nsio

nst

rain

[×10

-6］

Temperature［］

NMNF

Fig. 30 Temperature dependence of thermal expansion strain (Effect of type of cement).


temperature higher than 500°C. Since the aggregate generally constitutes a major proportion of the concrete mix, it has a primal influence on the thermal expansion strain of concrete. Different rocks show different ther-mal expansion levels, but the same rock does not always show the same values. For example, one study shows that limestone has larger thermal expansion at tempera-ture ranges from 500°C to 700°C than sandstone (Ba-zant and Kaplan 1996), but the other study shows that limestone has lower thermal expansion (Hertz 2005). To examine the effect of aggregate on the thermal expan-sion of concrete, it may be necessary to identify the properties of the aggregate itself used. 3.2.2 Specific heat Figures 32 through 34 show temperature dependence of specific heat. In these figures, one of three results for each test case is plotted as typical result, since three results show almost the same trend. The figures show clear two peaks at near 120°C and 540°C for all test cases, which are similar temperature dependent change to the previous studies presented in the fib bulletin (fib 2007). The first peak at 120°C is due to evaporation of free water contained in concrete, and the difference can be confirmed after comparing the sealed and abso-lute-dried specimens. While the specific heat of the ab-solute-dried specimen does not increase abruptly, the specific heat of the sealed specimen increases to as

much as about 2.7 J/g/K. No difference in specific heat can be observed between sealed and absolute-dried specimens when the temperature is over 200°C. The different first peak level is observed in Fig. 32, which shows the comparison between W/B45% and W/B55%. The first peak of W/B55% is higher than that of W/B45%. This may be explained by smaller porosity of W/B45%, which means less water content. The second peak near 540°C may be explained by decomposition of calcium hydroxide contained in the concrete, since the second peak value of the specimen with fly ash is smaller than other specimens without fly ash, as shown in Fig. 33. This is because content of calcium hydroxide

0

2000

4000

6000

8000

10000

12000

14000

0 100 200 300 400 500 600 700 800

Ther

mal

expa

nsi

onst

rain

[×10

-6］

Temperature［］

SandstoneLimestone

0

2000

4000

6000

8000

10000

12000

14000

0 100 200 300 400 500 600 700 800

Ther

mal

expa

nsio

nst

rain

[×10

-6］

Temperature［］

SandstoneLimestone

(a) W/B55% (b) W/B45%

Fig. 31 Temperature dependence of thermal expansion strain (Effect of type of aggregate).

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600 700 800

Spe

cific

heat

[J/g

/K]

Temperature []

W/B55%_SealedW/B45%_SealedW/B45%_Absolute dried

Spe

cific

heat

[J/g

/K]

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600 700 80Temperature []

W/B55%_SealedW/B45%_SealedW/B45%_Abusolute dried


Fig. 32 Temperature dependence of specific heat (Effect of water binder ratio).

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600 700 80

Spe

cific

heat

[J/g

/K]

Temperature []

N_SealedM_SealedM_Abusolute driedNF_SealedNF_Abusolute dried

Fig. 33 Temperature dependence of specific heat (Effect of type of cement).


of the specimen made of concrete with fly ash is small due to pozzolanic reaction. The effect of type of aggre-gate is small as shown in Fig. 34. 3.2.3 Thermal conductivity Figures 35 through 37 show the temperature depend-ence of thermal conductivity. The figures show the trend of thermal conductivity generally changes at the point of 100°C. Thermal conductivity increases with temperature below 100°C; however, it gradually decreases with temperature over 100°C. This trend corresponds to pre-vious research studies (Blundell et al. 1976; Schneider et al. 1981). The thermal conductivity of uniform mate-rials, such as ceramics or water generally increase with the increase of temperature, so the results below 100°C are corresponding to them; however, the results above 100°C show the opposite tendency. It may be explained by generation of cracks by heating. The space of cracks is filled with air since free water in concrete is evapo-rated above 100°C. The increase in cracks according to the increase of temperature, i.e. the increase of air voids that have small thermal conductivity, may lead to the decrease in the thermal conductivity of concrete. The change in the thermal conductivity depending on water content can also be confirmed in the results where the thermal conductivity of absolute dried concrete is smaller than that of sealed concrete at temperatures be-low 100°C.

The effect of the water binder ratio, type of cement,

and type of aggregate on the thermal conductivity test results is not significant. However, the methods of thermal conductivity measurement affect the results significantly. When the results by the GHP method and by the hot wire method are compared, the measured values by the hot-wire method are generally higher. By the GHP method, the entire volume of the specimen is heated at a uniform temperature, whereas by the hot wire method, measurement is made by an increase in the temperature near the hot-wire and the measurement tends to represent the local value. This difference may be one of the causes for the higher results from the hot-wire method.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600 700 80

Spe

cific

heat

[J/g

/K]

Temperature []

Sandstone_SealedLimestone_SealedLimestone_Abusolute dried

Spe

cific

heat

[J/g

/K]

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600 700 80Temperature []

Sandstone_SealedLimestone_SealedLimestone_Abusolute dried

(a) W/B55% (b) W/B45%

Fig. 34 Temperature dependence of specific heat (Effect of type of aggregate).

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600 700 800

Ther

mal

cond

uctiv

ity[W

/m/K

]

Temperature []

W/B55%_Absolute dried（GHP）W/B45%_Absolute dried（GHP）W/B55％_Sealed（GHP）W/B45%_Sealed（GHP）W/B45%_Absolute dried（Hot-wire）

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600 700 800

Ther

mal

cond

uctiv

ity[W

/m/K

]

Temperature []

W/B55%_Absolute dried（GHP）W/B45%_Absolute dried（GHP）W/B55%_Sealed（GHP）W/B45％_Sealed（GHP）W/B55%_Absolute dried（Hot-wire）W/B45%_Absolute dried（Hot-wire）


Fig. 35 Temperature dependence of thermal conductivity (Effect of water binder ratio).

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600 700 800

Ther

mal

cond

uctiv

ity[W

/m/K

]

Temperature []

N_Absolute dried（GHP）M_Absolute dried（GHP）NF_Absolute dried（GHP）N_Sealed（GHP）M_Sealed（GHP）NF_Sealed（GHP）M_Absolute dried（Hot-wire）NF_Absolute dried（Hot-wire）

Fig. 36 Temperature dependence of thermal conductivity (Effect of type of cement).


3.3 Comparison with material models of exist-ing codes In this sections, the results are compared with the mate-rial models of the Eurocode (Eurocode 2004), which is commonly used in the evaluation of concrete structure under high temperature, and the AIJ Guidebook (Archi-tectural Institute of Japan 2009). 3.3.1 Comparison of physical properties Figure 38 compares present results, the Eurocode and AIJ Guidebook on the physical properties. As shown in Fig. 38(a), the results on the compressive strength ratio almost correspond to the model of siliceous aggregate in the Eurocode and that of the AIJ Guidebook, except for the results of concrete with fly ash and concrete with

limestone. The temperature dependence on the com-pressive strength of concrete with fly ash and concrete with limestone show lower values than the model of existing codes. In the Eurocode, the model for calcare-ous aggregate is set higher than that for siliceous aggre-gate. This is an opposite trend to the test results. The Eurocode is presumably based on the data obtained from the concretes made of European aggregates and materials. The difference between the Eurocode and the present results with Japanese aggregate and materials may indicate that the locality of the aggregate should be considered when the material model is used.

Figure 38(b) shows the difference on elastic modulus ratio among present results, the Eurocode and AIJ Guidebook. The elastic modulus of the Eurocode is cal-

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600 700 800

Ther

mal

cond

uctiv

ity[W

/m/K

]

Temperature []

Sandstone_Absolute dried(GHP)Limestone_Absolute dried(GHP)Sandstone_Sealed (GHP)Limestone_Sealed (GHP)Limestone_Absolute dried(Hot-wire)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600 700 800

Ther

mal

cond

uctiv

ity[W

/m/K

]

Temperature []

Sandstone_Absolute dried(GHP)Limestone_Absolute dried(GHP)Sandstone_Sealed (GHP）Limestone_Sealed (GHP)Sandstone_Absolute dried(Hot-wire)Limestone_Absolute dried(Hot-wire)

(a) W/B55% (b) W/B45%

Fig. 37 Temperature dependence of thermal conductivity (Effect of type of aggregate).

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Com

pres

sive

stre

ngth

ratio

[－]

Temperature []

ReferenceW/B45%MNFLimestoneLimestone(W/B45%)Eurocode(Siliceous)Eurocode(Calcareous)AIJ(W/B55%)AIJ(W/B45%)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Ela

stic

mod

ulus

ratio

[－]

Temperature []

ReferenceW/B45%MNFLimestoneLimestone(W/B45%)EurocodeAIJ


0

5000

10000

15000

20000

25000

30000

0 100 200 300 400 500 600 700 800

Stra

inat

com

pres

sive

stre

ngth

[×10

-6]

Temperature []

ReferenceW/b45%MNFLimestoneLimestone(W/B45%)Eurocode

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800

Spl

ittin

gte

nsile

stre

ngth

ratio

[－]

Temperature []

ReferenceW/B45%MNFLimestoneLimestone(W/B45%)Eurocode


Reference: W/B55%, Ordinary Portland cement, Sandstone Fig. 38 Comparison between test results and existing codes (Physical properties).


culated by the same method mentioned in section 3.1.1, i.e. it is calculated based on the secant stiffness at 1/3 strength in stress-strain curve proposed by the Eurocode. As shown in Fig. 38(b), almost all results show inter-mediate values between the model of the Eurocode and the AIJ Guidebook. The smaller values of the Eurocode may be explained by the fact that stress-strain relation-ships in the Eurocode have been artificially softened than real stress-strain relationship (fib 2008). This is clearly shown in Fig. 38(c), which compares the strain at compressive strength. Strain at compressive strength in the Eurocode is greater than test results throughout all temperature ranges and especially drastically increases at temperatures above 300°C. The stress strain relation-ship proposed in the Eurocode is varied depending on the value of strain at compressive strength, so the Eurocode softens the stress strain relationship by setting larger strain at compressive strength (fib 2008).

As shown in Fig. 38(d), all the test results of splitting tensile strength ratio show greater than the Eurocode at a temperature higher than 200°C.

3.3.2 Comparison of thermal properties Figure 39 compares the results and the Eurocode on thermal expansion strain. Any test results correspond to the model for calcareous aggregate in the Eurocode at temperatures below 500°C. At temperatures above 500°C, the results show intermediate values between the models for siliceous aggregate and calcareous aggregate in the Eurocode.

Figure 40 shows the difference on specific heat be-tween our results and the Eurocode. The temperature where the first peak, which results from free water evaporation, is observed is generally consistent between our test results and the Eurocode. However, the Euro-code ignores the second peak around 540°C as observed in the tests. The Eurocode shows specific heat lower than the test results throughout all temperature ranges. Figure 41 shows the relationship between peak values of the test results and water content with respect to the effect of water content near 120°C. The figure shows that the peak value of specific heat increases linearly with increase in the water content. When the Eurocode data are plotted similarly, generally the same trend is observed.

0

2000

4000

6000

8000

10000

12000

14000

16000

0 100 200 300 400 500 600 700 800

Ther

mal

expa

nsio

nst

rain

[×10

-6]

Temperature［］

ReferenceW/B45%MNFLimestoneLimestone(W/B45%)Eurocode（Siliceous）Eurocode（Calcareous）

Reference: W/B55%, Ordinary Portland cement,

Sandstone Fig. 39 Comparison between test results and Eurocode (Thermal expansion strain).

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600 700 800

Spe

cific

hea

t[J/

g/K

]

Temperature []

Eurocode_3%

Eurocode_1.5%

Eurocode_0%

ReferenceW/B45%_SealedM_SealedNF_SealedLimestone_SealedLimestone(W/B45%)_SealedW/B45%_Absolute driedM_Absolute driedNF_Absolute driedLimestone_Absolute driedLimestone(W/B45%)_Absolute dried

Reference: W/B55%, Ordinary Portland cement, Sandstone, Sealed Fig. 40 Comparison between test results and Eurocode (Specific heat).

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.00 1.00 2.00 3.00 4.00 5.00

Spec

ific

heat

[J/g

/K]

Water content [%]

Measured

Eurocode

Fig. 41 Dependence of specific seat at around 120°C on water content.


Figure 42 compares the results and the Eurocode on thermal conductivity. The Eurocode model relatively corresponds to the results obtained by the GHP method. The results obtained by the hot-wire method are higher than the Eurocode throughout all temperature ranges. The Eurocode does not show the change of the trend at the point of 100°C observed in the tests, where the Eurocode model monotonically decreases thermal con-ductivity with increase of temperature from room tem-perature.

4. Conclusion

In this study, the concrete properties at the time of high temperature, such as the compressive strength, elastic modulus, strain at compressive strength, splitting tensile strength, thermal expansion strain, specific heat, and thermal conductivity, are obtained. Those data are com-pared with the material model of the Eurocode and/or the AIJ Guidebook. The following are the summary of findings in this study. The effects of the variables on the properties of concrete (1) The high temperature properties of concrete heated

for 35 days show a similar temperature dependence trend to the previous results obtained at room tem-perature after heating, but the results of the com-pressive strength ratio and the splitting tensile strength ratio show slightly greater values.

(2) The strength of concrete may be influenced by the equilibrium state of water content in the concrete. Compressive strength may be smaller when the ab-solute-dried condition of the concrete is not main-tained, i.e. the strength of concrete, in which free water is not sufficiently removed, decreases by in-ternal vapor pressure.

(3) The effect of heating duration on physical proper-ties is not significant after the equilibrium state of water content in the concrete is achieved.

(4) Physical properties do not recover when concrete is

cooled after heating. Cooling process may have negative impact to physical properties of concrete depending on the cooling conditions.

(5) The effect of the water binder ratio on physical properties (compressive strength ratio, elastic modulus ratio, and splitting tensile strength ratio) is small for 45% and 55%.

(6) Compressive strength and splitting tensile strength ratios of concrete with fly ash tend to be lower when compared to concrete without fly ash at the same exposure temperature.

(7) Compressive strength and splitting tensile strength ratios of concrete containing limestone aggregate tend to be lower when compared to the concrete containing sandstone aggregate at the same expo-sure temperature.

(8) The effect of the type of aggregate is significant for thermal expansion strain. The specimen containing limestone shows rapid increase of thermal expan-sion strain at temperature 500°C or higher.

(9) Two peaks at temperature around 120°C and 540°C are observed for specific heat. The effect of water content on the first peak value is significant. The peak value of specific heat at near 120°C linearly increases with increase in water content.

(10) The tendency of thermal conductivity with heating temperature changes at 100°C. An increase in thermal conductivity below 100°C changes to a de-crease over 100°C. The effect of test method (GHP and Hot-wire) is significant.

The differences between present results and ex-isting codes (1) Correlation is good between compressive strength

ratio results for sandstone aggregate concrete and the model for siliceous aggregate concrete in the Eurocode. The compressive strength of concrete with fly ash and concrete with limestone shows lower values than the model of the Eurocode and AIJ Guidebook.

(2) Almost all results on the elastic modulus ratio show

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300 400 500 600 700 800

Ther

mal

Con

duct

ivity

[W/m

/K]

Temperature []

Eurocod e _Upper

Eurocode_Lower

Referen ce（GHP）W/B45%（GHP）M（GHP）NF（GHP）Limestone（GHP）Limestone(W/B45% )（GHP）W/B45%（Hot-wire）M（Hot-wire）NF（Hot-wire）Limestone（Hot-wir e）Limestone(W/B45% )（Hot-wire）

Reference: W/B55%, Ordinary Portland cement, Sandstone Fig. 42 Comparison between test results and Eurocode (Thermal conductivity).


intermediate values between the model of the Eurocode and AIJ Guidebook. The test results on strain at compressive strength are smaller than the Eurocode throughout all temperature ranges up to 700°C. These may be explained by the fact that stress-strain relationships in the Eurocode have been artificially softened.

(3) The results specify greater splitting tensile strength ratio than the model of the Eurocode at tempera-tures above 200°C.

(4) Regardless of type of aggregate, the results on thermal expansion strain shows good correlation with the model of calcareous concrete in Eurocode.

(5) The results on specific heat show generally greater values than the model of the Eurocode. The second peak at 540°C observed in the tests is ignored in the model of the Eurocode.

(6) The results on thermal conductivity obtained by the GHP method correspond to the model of the Euro-code. The change of the trend at the point of 100°C observed in the tests is not considered in the model of the Eurocode.

Acknowledgements This work was carried out during FY 2008-2009 as Japanese national project “Development of Innovative Construction Method (SC Structure)” and during FY 2012-2014 as Japanese national project “Upgrading of integrity evaluation method of primary containment vessel” with the participation of the Chugoku Electric Power Company, Inc.; Tohoku Electric Power Company, Inc.; Tokyo Electric Power Company, Inc.; Chubu Electric Power Company, Inc.; Hokuriku Electric Power Company, Inc.; The Japan Atomic Power Company; Electric Power Development Company, Ltd.; the Insti-tute of Applied Energy, Hitachi-GE Nuclear Energy, Ltd.; and Toshiba Corporation.

We would like to thank Emeritus Professor Nishi-kawa, T. at Tokyo Metropolitan University, Emeritus Professor Takiguchi, K. at Tokyo Institute of Technol-ogy, Professor Kitsutaka, Y. at Tokyo Metropolitan University, and Professor Maruyama, I. at Nagoya Uni-versity for valuable comments and discussions.

References Architectural Institute of Japan, (2009). “Guidebook for

fire-resistive performance of structural materials.” in Japanese

Arioz, O., (2007). “Effects of elevated temperatures on properties of concrete.” Fire Safety Journal, 42, 516-522.

Bazant, Z. P. and Kaplan, M. F., (1996). “Concrete at high temperature: Material properties and mathematical models.” Longman, London, UK.

Blundell, R., Diamond, C. and Browne, R., (1976). “The properties of concretes subjected to elevated temperatures.” Report No.9, Construction Industry Research and Information Association, Under water

Engineering Group, London, UK. Carette, G. G., Painter, K. E. and Malhora, V. M., (1982).

“Sustained high temperature effects on concretes made with normal Portland cement, normal Portland cement and slag, or normal Portland cement and fly ash.” Concrete International, 4(7), 41-51.

Carette, G. G. and Malhora, V. M., (1982). “Performance of dolostone and limestone at sustained high temperature.” Proceedings of Symposium Temperature Effects on Concrete, ASTM Special Technical Publication 858, 38-67.

Castillo, C. and Durrani, A. J., (1990). “Effect of transient high temperature on high-strength concrete.” ACI materials Journal, 87(1), 47-53.

DeFigh-Price. C et al., (1984). “Effects of long-term exposure to elevated temperature on mechanical properties of concrete.” ACI Symposium on Concrete and Cementitious Materials for Radioactive Waste Management, New York, USA.

Eurocode, (2004). “Eurocode 2: Design of concrete structures – Part1-2: General rules – Structural fire design.” EN 1992-1-2.

fib, (2007). “Fire design of concrete structures –materials, structures and modelling,” Bulletin 38.

fib, (2008). “Fire design of concrete structures –structural behavior and assessment,” Bulletin 46.

Harada, T., Takeda, T., Yamane, S. and Furumura, F., (1972). “Strength, elasticity and thermal properties of concrete subjected to elevated temperatures.” Paper SP-34-21 in Concrete for Nuclear Reactors, 377-406, ACI.

Hertz, K. D., (2005). “Concrete strength for fire safety.” Magazine of Concrete Research, 57(8), 445-453.

Hirama, T., Kumagai, H., Tanabe, M., Saigou, S., Sawada, S. and Akase, T., (2015) “Applicability evaluation of steel platereinforced concrete structure to primary containment vessel of BWRs, (2) Mechanical and thermal properties of steel under high temperature conditions.” Proceedings of 23rd International conference on Structural Mechanics in Reactor Technology (SMiRT23), Manchester, UK.

Kakae, N., Nishimura, K., Miyamoto, K., Sawada, S. and Momma, T., (2013) “Physical properties of concrete subjected to elevated temperatures up to 700°C.” Summaries of Technical Papers of Annual Meeting, Architectural Institute of Japan, 101-102. (in Japanese)

Kanazu, T., Matsumura, T. and Nishiuchi, T., (1996). “Changes in the mechanical properties of concrete subjected to long-term exposure to high tempera-tures.” Report No. U95037, Abiko Research Labo-ratory, Central Research Institute of Electric Power Industry.

Kasami, H., Okuno, T. and Yamane, S., (1975). “Properties of concrete exposed to sustained elevated temperature.” Proceedings of 3rd International conference on Structural Mechanics in Reactor Technology (SMiRT3), London, UK


Kishitani, K., Kasami, H., Oshida, F. and Okuno, T., (1982). “Property of concrete exposed to sustained elevated temperature ranging 20 to 300°C: Part 1 and 2” Summaries of technical Papers of the Annual Meeting of the Architectural Institute of Japan, 317-320. (in Japanese)

Kitajima, Y., Miyagawa, T., Hirako, S., Kojima, I., Hirama, T. and Akase, T., (2015). “Applicability Evaluation of Steel Plate Reinforced Concrete Structure to Primary Containment Vessel of BWRs, (4) Shear loading test of steel-plate reinforced-concrete structure under high temperature conditions.” Proceedings of 23rd International conference on Structural Mechanics in Reactor Technology (SMiRT23), Manchester, UK.

Kitano, K., Shin, K., Kinoshita, N., and Okuno, T., (1988). “Mechanical, thermal properties and Permeability of Rocks under High temperature.” Journal of the Japan Society of Engineering Georogy, 29-3, 36-47. (in Japanese)

Khoury, G. A., (1983). “Transient thermal creep of nuclear reactor pressure vessel type concretes.” Ph.D. Dissertation, University of London.

Khoury, G. A., (1992). “Compressive strength of concrete at high temperature: A reassessment.” Magazine of Concrete research, 44(161), 291-309.

Li, M., Qin, C. X. and Sun, W., (2004). “Mechanical properties of high-strength concrete after fire,” Cement and Concrete Research, 34, 1001-1005.

Maruyama, I., Sasano, H., Nishioka, Y., and Igarashi, G., (2014). “Strength and Young’s modulus change in concrete due to long-term drying and heating up to 90°C.” Cement and Concrete research, 66(0), 48-63.

Mendes, A., Sanjayan, J. and Collins, F., (2008). “Phase transformations and mechanical strength of OPC/Slag pastes submitted to temperature.” Materials and Structures, 41, 345-350.

Mendes, A., Sanjayan, J. and Collins, F., (2009). “Long-term progressive deterioration following fire exposure of OPC versus Slag blended pastes.” Materials and Structures, 42, 95-101.

Nagao, K. and Nakane, S., (1991). “Influences of various factors on physical properties of concretes heated to high temperatures.” Proceedings of 11th International conference on Structural Mechanics in Reactor Technology (SMiRT11), Tokyo, japan.

Narita, S., Osaka, M., Kurita, T., Kobayashi, T., Kakae, N. and Kobayashi, Y., (2015). “Applicability evaluation of steel plate reinforced concrete structure to primary containment vessel of BWRs, (3) Compressive loading test of steel-plate reinforced-concrete structure under high temperature conditions.” Proceedings of 23rd International conference on Structural Mechanics in Reactor Technology (SMiRT23), Manchester, UK.

Nasser, K. W. and Chakaborty, H., (1985). “Temperature effects on strength and elasticity of concrete containing admixtures.” Proceedings of

Symposium Temperature Effects on Concrete, ASTM Special Technical Publication 858, 118-133.

Naus, D. J., (2006). “The effect of elevated temperature on concrete materials and structures - A literature review.” NUREG/CR-6900 ORNL/TM-2005/553.

Naus, D. J., (2010). “A compilation of elevated temperature concrete material property data and information for use in assessments of nuclear power plant reinforced concrete structures.” NUREG/CR-7031 ORNL/TM-2009/175.

Ohga, Y., Saigo, S., Hirai, H., Kakae, N., Miyamoto, K., Kumagai, H. and Kobayashi, Y., (2015). “Applicability evaluation of steel plate reinforced concrete structure to primary containment vessel of BWRs, (1) Mechanical and thermal properties of concrete under high temperature conditions.” Proceedings of 23rd International conference on Structural Mechanics in Reactor Technology (SMiRT23), Manchester, UK.

Okayasu, T., Momma, T., Imamura, Y., Mimori, S. and Kobayashi, Y., (2015). “Applicability evaluation of steel plate reinforced concrete structure to primary containment vessel of BWRs, (5) Horizontal loading test of cylindrically-shaped steel-plate reinforced-concrete structure under high temperature conditions.” Proceedings of 23rd International conference on Structural Mechanics in Reactor Technology (SMiRT23), Manchester, UK.

Poon, C. S., Azhar, S., Anson, M., and Wong, Y. L., (2001). “Comparison of the strength of ordinary and high performance concrete.” Cement and Concrete Research, 31, 1291-1300.

Poon, C. S., Azhar, S., Anson, M., and Wong, Y. L., (2003). “Performance of metakaolin concrete at elevated temperature.” Cement and Concrete Composites, 25, 83-89.

Raju, M. P., Shobha, M. and Rambabu, K., (2004). “Flexural strength of fly ash concrete under elevated temperatures.” Magazine of Concrete Research, 56(2), 83-88.

Sarshar, R. and Khoury, A., (1993). “Material and environmental factors influencing the compressive strength of unsealed cement paste and concrete at high temperature.” Magazine of Concrete Research, 45(162), 51-61.

Schneider, U., Diererichs, C. and Ehm, C., (1981). “Effect of temperature on steel and concrete for PCRV’s.” Nuclear Engineering and Design, 67, 245-258.

Suzuki, T., Tabuchi, M. and Nagao, K., (1995). “Study on the degradation of concrete characteristics in the high temperature environment.” In: Concrete under Severe Conditions: Environment and Loading, 2, 1119-1128.

Xu, Y., Wong, Y. L., Poon, C. S. and Anson, M., (2001). “Impact of high temperature on PFA concrete.” Cement and Concrete Research, 31, 1065-1073.

Documents

Physical and Thermal Properties of Concrete Subjected to