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NBSIR 82-1658

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MECHANICAL PROPERTIES OF CONCRETE

MORTAR AT LOW TEMPERATURES

J. M. Arvidson

L. L. Sparks

E. Steketee

National Bureau of Standards

U.S. Department of Commerce

Boulder, Colorado 80303

February 1982

—QO—

100

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32-1653

1932

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NBSIR 82-1658

MECHANICAL PROPERTIES OF CONCRETE

MORTAR AT LOW TEMPERATURES

t Fracture and Deformation Division

National Measurement Laboratory

ft Thermophysical Properties Division

National Engineering Laboratory

National Bureau of Standards

U.S. Department of Commerce

Boulder, Colorado 80303

February 1982

Prepared for Maritime Administration

U.S. Department of Commerce

Washington, D.C. 20235

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BtTIUlAU OF STANDARDS

LIBRARY

J. M. Arvidsonf

L. L. Sparks tt

E. Steketeef

may 14 1982

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Director

Mechanical Properties of Concrete Mortar at Low Temperatures!

J. M. Arvidson, L. L. Sparks, and E. Steketee

This report includes test results conducted at ambient (295 K) , dry-ice and alcohol

(195 K) , liquid nitrogen (76 K) , and liquid helium (4 K) temperatures. The compressive

properties reported are Young's modulus, yield (at 0.2% offset) and maximum strengths, and

elongation (elastic and plastic). Test specimens (5.1 cm diameter x 10.2 cm) were instrumented with a specially designed, diametrically opposed, cryogenic strain-gaged extensometer that minimizes possible errors due to specimen bending during the test.

Key words: Compressive strength; concrete mortar; elongation; low temperature; maximum

strength; mechanical properties; yield strength; Young's modulus.

1. Introduction

Concretes are attractive materials for construction of large low- temperature installations because of lower material cost and economies of fabrication compared to alternative construction methods. Furthermore, they exhibit favorable mechanical and thermal

properties for use in low-temperature applications. Although these materials are presently used to some extent in LNG and LPG construction, lack of confidence in their

cryogenic behavior has restricted their use or has resulted in overly conservative and

expensive designs. This reflects the lack of dependable cryogenic thermal and mechanical

properties data and a poor understanding of the effect of field-fabrication variables on cryogenic performance.

Potential LNG- or LPG-oriented applications of concretes are diverse. Concrete is

currently used for barge hulls and for ground-based storage facilities [1,2]. Proposals

and designs for construction of large seagoing tankers and floating terminals, in which

both the hull and the primary LNG containment systems are made of concrete, are also being

considered. Possible applications of special concretes such as lightweight, cellular,

fiber reinforced, and polymer will depend on their cryogenic properties which are not

known at this time.

The research described below is part of a broader program to determine the thermal

and mechanical properties of aggregate composites. The mechanical properties of two

concrete mortars were determined at ambient (295 K) , dry-ice and alcohol (195 K) , liquid

nitrogen (76 K) , and liquid helium (4 K) temperatures. The properties reported here are compressive Young's modulus, yield strength (at 0.2% offset), maximum, ultimate, flexural,

and splitting strengths, K

Ic , and elastic and plastic elongations.

2. Materials Characterization

The physical properties of two concrete mortars (designated mix 1 and mix 2) were studied in this program. Mix 1 was made by a commercial-cement company and mix 2 was made

at the National Bureau of Standards. Both mixes utilized portland type I cement and a resin air-entraining agent. The aggregate used in mix 1 is commonly known as Elgin sand and

that used in mix 2 is commonly referred to as Clear Creek sand. The chemical makeup and

sieve analysis of each type of aggregate are shown in tables 1 and 2. Both mortars were mixed using the following ratios (by weight): water/cement = 0.5, aggregate/cement = 3.4.

The air content of the hardened mortars was 11.0 and 17.7 vol.%, respectively, and the

evaporable moisture contents were 8.1 and 10.8 wt.% relative to the oven-dry weight. The

mixing procedure described in ASTM C192 was utilized for both mixes.

Mix 1 was designed to produce a mortar with a compressive strength of approximately

17.2 MPa (2500 psi). To maintain this strength until testing, the 10-day-old specimens

were placed in a freezer held at 0°C. The hydration process, which causes concretes to increase in strength as they age, is slowed considerably at this temperature. Prior to the 0°C aging, the specimens were aged in covered glass molds for 24 h at 23°C and then

removed from the molds and placed in saturated-lime water at 23°C for 7 days. Upon removal

from the lime-water bath, they were wrapped in plastic and aluminum foil for shipment.

tThis work was done for the Department of Commerce, Maritime Administration, Department of

Commerce Building, Washington, D.C. 20235, under Program 193000, Project 12-410-54-425.
Table 1. Primary components of aggregates by percentage of

particle count remaining on standard sieves.

Mix Component

No. 8 (2.36 mm)

Standard Sieves

No . 16

(1.19 mm)

No. 30

(0.60 mm)

1 Carbonate 80.3 79.8 64.3

Chert 8.9 11.0 — Granite 3.6 2.4 — Basalts 3.4 2.0 1.2

Quartzite 3.0 4.3 — Quart z-Chalcedony — — 26.5

Feldspar — — 7.6

2 Granite 67.4 66.4 33.2

Metamorphics 7.2 3.7 1.5

Basalts 6.8 2.7 1.8

Quartz 12.4 17.2 44.9

Feldspar 5. 7 7.2 15.9

Table 2. Sieve analysis of the aggregates used in mix 1 and mix 2.

Standard Sieve Percent Passing

Number Size (mm) Mix 1 Mix 2 (Elgin) (Clear Creek)

4 4.75 100 99

8 2.36 78 80

16 1.18 63 59

30 0.60 46 29

50 0.30 10 7 100 0.15 0 0

Mix 2 was made in two batches separated by 8 months. Mix design and conditioning for

both batches were identical. The mortar was formed in airtight plastic molds and aged in

the mold for 2 days at 23°C. After removal from the molds, the specimens were immersed in

a saturated lime-water bath at 23°C. They remained in the bath until tested. The age of

the specimens at the time of testing was from 79 to 215 days.

3. Specimens

The solid core specimen geometry was chosen for the compression and splitting

strength tests; specimens measured 5.1 cm in diameter and 9.9 cm long, as recommended by

ASTM C469-65, C496-71, and C873-77T. The flexural strength test specimens were

5.3 cm x 1.8 cm x 4.6 cm per ASTM C78-75.

The ends of all specimens to be tested in compression were ground parallel and

perpendicular to the longitudinal axis to within ±6.3 x 10 4 cm. All mix 1 samples were completely saturated with lime-water solution a*id then kept at 0°C until the time for

testing. All mix 2 specimens were stored in a lime-water solution and were removed just

prior to testing.

4. Test Procedure

Tests were performed using a commercial 1.0 MN (2.2 x 10 5 lbf) servohydraulic

static/fatigue test machine. The manufacturer's specifications indicate that the load

2
weighing system accuracy is ±0.5% of indicated load or ±0.25% of the load range in use, whichever is greater, on all load ranges. The crosshead speed used for all tests was

0.

005 cm/min and is accurate to ±0.1% of set speed at all loads and speeds. Compression

specimens were instrumented with specially designed, diametrically opposed cryogenic

strain-gage extensometers . This method for sensing strain worked at all temperatures,

including total immersion in liquid nitrogen and liquid helium. Prior to each test,

particular care was taken to insure coaxial alignment of all test components (e.g.,

actuator ram, specimen, dewar) to insure uniaxial loading.

Specimen failure modes indicated a well-aligned system with a minimum of bending,

1.

e., uniform, conically shaped fractures emanating from the specimen ends to the center.

Some testing was carried out to determine plane strain fracture toughness of mix 2. Short-rod specimens with a single chevron in the configuration proposed by Barker and

Baratta [3] were prepared. The diameter was 5.1 cm and the length was 10.2 cm. Testing

at all temperatures was carried out in a newly designed fixture that operates like a pinch-type clothespin to load the chevron-notched specimen in tension.

This fixture has a lever-arm ratio of 2:1 and can be fitted into most universaltesting machines. The plane strain fracture toughness, SR, was calculated using the

following equation proposed by Baker and Baratta [3] and modified by Beech and Ingraffea

[4]:

AP

K, SR =

Ic b 3/2

where A is a dimensionless calibration constant

geometry), P^ is the load at crack instability,

With one exception the specimens fractured

in the body of the specimen.

v22.5 ± 15% (dependent on specimen

and B is the specimen diameter.

across the chevron; one specimen fractured

5. Results

The compressive Young's modulus for mix 1 increased in value from room temperature to 195 K, and then at 76 and 4 K it decreased by approximately 30 percent (table 3). The

compressive strength, however, increased as the test temperature decreased. Also, only at

195 K did mix 1 show a maximum compressive strength before reaching its ultimate.

The compressive modulus, proportional limit, and ultimate compressive strength for

mix 2 all increased in value as the test temperature decreased (table A) . As shown in

table 5, the splitting tensile strength increased from 295 to 195 K and then remained the same down to 76 K. The modulus of rupture (flexural strength), however, shows a peak

value at 195 K.

The plane strain fracture toughness, SR, for short-rod specimens of mix 2 are tabulated vs. temperature in table 6. The room temperature results on moist mix 2 mortar

are comparable to the fracture toughness reported for two kinds of rock [5]:

TYPE OF

ROCK

MPa* m

1/2

Kt SR

Ic

. . 1/2

ps i* m

Limestone 0.99 900

Granite 2.48 2250

The results in table 6 show that there was a substantial increase in SR as temperature

was lowered initially, but no additional increases as temperature was 'lowered further.

Splitting strength showed the same trend with decreasing temperature. It is likely that

the pronounced increase in toughness with decreasing temperature is related to changes in

the internal structure of the moist specimens as the water entrained in the pores freezes

3
and expands and then contracts with further cooling. Monfore and Lentz [6] discuss

possible effects of freezing on concrete.

The plane strain fracture toughness of mix 2 mortar /table 6) is low compared to the

fracture toughness of structured steels i.e., 54.9 MPa^m1 2 (50 ksi’in 2 2 ). This comparison suggests that concrete is not a suitable structural material under tensile loading.

Nevertheless, the low cost and widespread availability of concrete may favor its

application in compressive-loading situations.

Table 3. Effect of temperature on compressive Young's modulus and compressive

strength for moist concrete mortar (mix 1).

Test Compressive Compressive Strength

Temperature Young 'Modulus a Maximum!- a Ultimate!

K GPa ksi MPa ksi MPa ksi

295 15.9 2300 — — 23.0 3.34

8.6 1250 — — 21.8 3.16

22.4 3250 — — 23.4 3.40

x = 15.6 2270 22.7 3.30

195 —27.2 —3950

56.5 8.20 53.8 7.81 —38.1 —5530 49.1 7.12 47.6 6.90

57.4 8. 32 56.9 8.25

x = 32.7 4740 54.3 7.88 52.8 7.65

76 14.3 2070 71.1 10.31

31.0 4490 — — 107.8 15.64

17.7 2570 — — 90.9 13.18

22.8 3300 — — 87.9 12.75

x = 21.5 3110 89.4 12.97

4 23.0 3340 — — — —

+a Maximum: maximum stress the specimen reached during the test.

to Ultimate: stress at failure.

Table 4.. Effect of temperature on compressive properties

for moist concrete mortar (mix 2)

Test Compressive Proportional Ultimate Compressive

Temperature Young 'Modulus Limit Strength

K GPa ksi MPa ksi MPa ks i

295 15.25 2210 14.45 2.10 31.23 4.53

19.80 2800 15. 65 2.27 28.40 4.12

X = 17.26 2510 15.05 2. 19 29.82 4.32

195 30.65 4450 33.04 4. 79 89.19 12.94

33.78 4900 28.87 4.19 93.22 13.52

X = 32.22 4680 30.96 4.49 91.21 13.23

76 38.59 5600 120.9 17.53

44.71 6480 — 102.5 14.87

X = 41.65 6040 111.7 16.20

4
Table 5. Effect of temperature on splitting and flexural

strength of moist concrete mortar (mix 2)

.

Test

Temperature

K

Splitting Tensile

St rength*

MPa ksi

Modulus

MPa

of Ruptured

ksi

295 2.32 0.34 5.25 0.76

2.64 0.38 5.25 0.76

x = 2.48 0.36 5.72 0.83

x = 5.41 0.78

195 6,.62 0.96 13.44 1.95

9..69 1.41 13.88 2.01

x = 8

.

.15 1.19 x = 13.66 1.98

76 5..96 0.86 9.26 1.34

8..54 1.24 11.91 1.73

x = 7,.25 1.05 x = 10.59 1.54

*ASTM C496-71 splitting tensile strength = T = 2P/fr£,d

where: T = splitting tensile strength, MPa (or psi)

P = maximum applied load, N (or lbf)

1 = length, mm (or in)

d = diameter, mm (or in)

t ASTM C78-75

where: R =

P =

1 =

b =

d =

2 modulus of rupture = R = 3P£/2bd

modulus of rupture, MPa (or psi)

maximum applied load, N (or lbf)

span length, mm (or in)

average width of specimen, mm (or in)

average depth of specimen, mm (or in)

Table 6. Fracture toughness of short rod moist concrete mortar specimens (mix 2)*

Temperature, K KtIc 1/2 MPa-m 'SR

, . . 1/2. (psi'in )

P

c kg (lb)

295 0.88 (800) 41.0 (90.28)

0.95 (860) 41.8 (92.16)

0.88 (800) 39.3 (86.54)

195 2.26 (2060) 101.0 (222.56)

2.24 (2040) 99.9 (220.30)

2.04 (1860) 91.8 (202.32)

2.20 (2000)

t

97.9 (215.80)

76 1.91 (1740) 85.1 (187.70)

*A11 test

tSpecimen

• r ~ o +0 . 00 . ,

.

specimens were 5.08

^ ^

cm m diameter,

fractured in body away from chevron.

5
6. References

[1] B. C. Gerwick, "Design and Construction of Prestressed Concrete Vessels," Paper

Number OTC 1886, presented at the Fifth Annual Offshore Technology Conference,

Houston, Texas, (1973).

[2] B. C. Gerwick, "State of the Art Report - Durability of concrete Structures Under

Water," presented at the International Association Colloquium-Liege, Belgium (June 5,

1975) . [3] L. Barker and Barrata: Comparison of fracture toughness measurements by the short

rod and ASTM standard method of test for plane strain fracture toughness of metallic

materials (E 399-78), J. Test. Eval. 8(3): 97 (1980).

[4] J. F. Beech and A. R. Ingraffea, Three dimensional finite element calibration of the

short-rod specimen, accepted for publication in the Int ' 1 . J . Fract. , in press.

[5] A. R. Ingraffea and H. Y. Ko , Determination of the fracture parameters for rock,

paper to appear in: "Proceedings of the International Symposium on Absorbed Specific

Energy," Budapest, Hungary (Sept. 1980), in press.

[6] G. E. Monfore and A. E. Lentz, Physical properties of concrete at very low temperatures, JL_ PCA Res . Dev . Lab . 4(2) :33 (1962) . [7] Mindess, Sidney, "Application of Fracture Mechanics to Cement and Concrete," presented at the 81st Annual Meeting of the American Ceramic Society, Cincinnati, Ohio,

Paper 1-S II - 79 (1979).

6
NBS-1 14A (REV. 2-80

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

4. TITLE AND SUBTITLE

PUBLICATION OR

REPORT NO.

2. Performing Organ. Report No. 3. Publication Date

NBSIR 82-1658 February 1982

Mechanical Properties of Concrete Mortar at Low Temperatures

5. AUTHOR(S)

J. M. Arvidson, L. L. Sparks, and E. Steketee

6. PERFORMING ORGANIZATION (If joint or other than N BS. see in struction s) 7. Contract/Grant No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

Maritime Administration

U.S. Department of Commerce

Washington, DC 20235

10. SUPPLEMENTARY NOTES

] Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT ( A 200-word or less factual summary o f most significant information. I f document includes a significant

bibliography or literature survey, mention it here)

This report includes test results conducted at ambient (295 K)

,

dry-ice and alcohol (195 K) , liquid nitrogen (76 K) , and liquid helium

(4 K) temperatures. The compressive properties reported are Young's

modulus, yield (at 0.2% offset) and maximum strengths, and elongation

(elastic and plastic). Test specimens (5.1 cm diameter x 10.2 cm) were

instrumented with a specially designed, diametrically opposed, cryogenic

strain-gaged extensometer that minimizes possible errors due to specimen

bending during the test.

12. KEY WORDS (Six to twelve entries ; alphabetical order; capitalize only proper names; and separate key words by semicolon s) Compressive strength; concrete mortar; elongation; low temperature;

maximum strength; mechanical properties; yield strength; Young's

morinl ns.

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15. Price 20402.

[_Xj Order From National Technical Information Service (NTIS), Springfield, VA. 22161 $5.00

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1982-577-609/130 Region No. 8

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