The test method of freezing bricks : its influence on their durability

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Publisher’s version / Version de l'éditeur:

Journal of the Canadian Ceramic Society, 44, pp. 21-22, 1975

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The test method of freezing bricks : its influence on their durability

Ritchie, T.

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N a t i o n a l Research Council o f Canada

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THE TEST METHOD OF FREEZING BRICKS: ITS

INFLUENCE

ON THEIR DURABILITY

by T. R i t c h i e

9

R e p r i n t e d from

Journa

1 _{o f t h e Canadian Cerami c S o c i e t y}

Vol.

44,

1975,

DBR Paper No.

683 D i v i s i o n o f B u i l d i n g Research

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in t h e cold chamber, a n d freezing occurred by the unidirectional passage o f the freezing plane through t h e bricks. T h e bricks frozen unidirectionally were not in contact with water. After 20 hours in the cold room the bricks were removed for thawing. T h e trays containing bricks were immersed directly in water; the other bricks were first removed from the insulated box, then immersed in water. After four hours in t h e thawing tank the bricks were again placed in the tray a n d in t h e insulated box for another freezing. After 10 freezings, the bricks were air-dried for t w o days after thawing before the freeze-thaw procedure was continued. T h e air temperature of t h e cold c h a m b e r

(a

"walk-in" type) was usually in t h e range 0°F to -10°F

(-18°C

to

-23°C).

Tests with non-durable bricks

Back-up bricks obtained from the demolition of a building erected in Ottawa about 1920 were used in s o m e of the tests because of their suspected lack o f resistance to freezing a n d thawing. T h e s e were soft-mud bricks with sanded surfaces; they varied in colour from brown to red, the former bricks probably having been fired at a lower temperature than the latter. After selecting five brown bricks a n d five red bricks for test, each brick was cut in half, the first half to be frozen a n d thawed in the standard way, the other half to be frozen unidirectionnally.

T h e durability o f both the brown a n d red bricks was o f a very low order regardless of t h e test method. Most of the bricks showed s o m e indication of distress after the first o r second freezing and serious d e ~ e r i o r a t i o n occurred in all o f t h e m well before 10 freezings had been carried out. T h e m a n n e r in which t h e bricks failed differed appreciably. however. T h e bricks frozen in the standard way broke up in t h a t part o f the brick at o r beneath the surface of the water in which i t stood when frozen. T h e bricks frozen unidirectionally failed in the surface exposed to the freezing temperature, w h e r e pieces of the brick became detached from the body. After a few freezings about a quarter of the body o f each brick was shattered but the remainder appeared to be sound. T h e decayed portion in the case of the samples frozen unidirectionally extended into the brick from the face exposed to the cold-room air, while t h e bricks frozen in the standard way were shattered o n the opposite side.

Tests with old veneer bricks

Soft-mud bricks used as a veneer to cover wood-stud walls were obtained from :he demolition o f a house in Ottawa, erected about 1900. T h e bricks were red, with sanded surfaces, a n d were imprinted " R d 97" in the frog. Five bricks w e r e cut in half to compare durability by the two test methods.

T h e bricks frozen unidirectionally did n o t appear to be

damaged by 50 freezings, but three of the five bricks frozen a n d thawed by the tray method showed damage soon after the start o f the test. These samples were removed from test because of severe damage d o n e to them after 5 , 7 and 8 freezings, respectively. T h e fourth brick failed at 19 freezings. but the fifth brick tested by the tray method apppeared undamaged after 50 freezings. Failure occurred by pieces coming away from the body of the brick. mainly in that part of i t near o r below the level of water in which i t stood when frozen.

Test of modern bricks

Bricks of recent manufacture, made by stiff-mud extrusion at several plants, were included in the study. For o n e of the bricks. freezing by both methods produced damage before the completion of 50 freezings. Damage occurred much sooner a n d was more extensive. however. in the samples frozen by the standard method than in those frozen unidirectionally. In tests of bricks from two other plants, the samples frozen.by the standard method were daninged well before 50 freezings had been carried out, but samples frozen unidirectionally were undamaged.

Conclusions

A comparison of the two test methods s h o w s that the m a n n e r of brick failure is different. Since the unidirectional m e t h o d is designed as a more realistic simulation of the weathering of bricks. the damage that occurs through this process o f freezing m o r e closely approximates thc nctunl m o d e of failure of bricks in a wall than does the decay caused by the standard test. T h e standard test also induces damage niore rapidly. T h e A.S.T.M. a n d C.S.A. method of t c ~ t i n g bricks for freeze-thaw durability, therefore. does not corres- pond to the freezing conditions of bricks in a wall and thc unidirectional process is a more acceptable test merhod for brick durability.

References

( I ) Building Brick (Solitl Masonr!' LJnits Made from C'Iit!, or Sh;~lc). An1eric;tn Sucic~y for Testing ant1 Mi~!er~;il\. SL<~ndartl Spcc~fici~tion C62 -69. P h ~ l ~ ~ d e l p h ~ ~ ~ . P;I

( 2 ) Burned C'l;~y Brick. CanadIan St.lndartl5 Associa[~on. Stan-

dard A82 1 - 196.5. RcxdCilc. Ontario.

(3) J.W, McBurney and C.E. Lovcwcll Streng~li. Witter Ah\orl)- tion and We;~ther Res~stance of Build~ng Br~ckj Prod~lcetl in the United States. & ~ c ~ c ~ c ~ ~ b ~ r g \ . .1.57\433. Par! 11 (1933)- ( 4 ) H.D. Foster. Weathering Test Procctlures for Cli11 Protluct\

Proc,c~c~il~~ig\. 4STM 3 1 : Part 11 (1931 )

(5) W . E . Patterson. Accelcrared and Aclual Free~ing ant1 Thaw- ing Tests ol' S~ructural Ceramic Mnterlals. .I C ' i r ~ r . C ' e ~ ~ c r ~ r r $11. 2 (1933).

( 6 ) T. Rltchie. Freeze-thaw Action-on Brick, .I. ( ' i r ~ r ( ' c z ~ i r ~ i i Jot d l (1972).