The nature of frost action

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Proceedings of the Thirty-Eighth Convention of the Canadian Good Roads

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The nature of frost action

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C A N A D A

D I V I S I O N O F B U I L D I N G R E S E A R C H

THE NATURE

OF FROST

ACTIOT{

BY E. PENNER

A N A L Y Z E D

R E P R I N T E D F R O M B R O C E E D I N q S O F T H E T H T R T Y - E T G H T H C O N V E N T I O N O F T H E C A N A D I A N G O O D R O A D S A S S O C I A T I Q N , T E C H N I C A L P A P E R N O . 3 3 O F T H E D I V I S I O N O F B U I L D I N G R E S E A R C H

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Ihe l{afure

ol froil Acfion

By E. PENNER,

Division of Building Reseorch, Notionol Reseorch Council of Conodo

Rspnrxreo rnou PnocBnDrNGs oF THE Cexlorex Gooo Rolos AssocnrroN 1957 The eftect of frost action on such

engineering works as highways and streets, airport runways, building founda-tions, cold storages, ice rinks and many others is well known. The yearly eco-nomic loss to the nation in terms of maintenance and reconstruction directly attributable to this cause may well run as high as millions of dollars.

Destruction due to frost action can occur when water freezes and expands in the porous structure of solid materials. This is known to be important in many building materials when subjected to freezing but how important it is in soils is still not known. Secondly, when a thermal gradient is sustained in soils for a long period of time, sufficient moisture may accumulate to reduce its bearing str€ngth significantly. Thirdly, ice lenses may form in the material which cause heaving far in excess of the normal expansion when water freezes. Subse-quent thawing releases vast quantities of water which may, in the case of soils, reduce it from a substantially rigid ma-terial to the consistency of a slurry.

For frost heaving to occur as a result of ice lensing three factors are known to eiist in combination. These are: suf-ficiently cold temperatures to freeze some of the soil water, a supply of water available to the freezing zone, and a frost-susceptible soil. Ice lensing does not occur when any one of these factors is absent.

The Soil Mechanics Section of the Division of Building Research has been concerned with many of the broader aspects of frost action. Soil tenperatures and the relation between maximum depth of freezing and features of the climate such as air temperatures and snow cover have been studiedl' z. The possibility of deriving a climatic index as an indicator of the severity of spring break-up of highways has also been explored3. More recently, the nature of the mechanism by which .ice lensing is produced has been under extensive investigation in the laboratorYa' 5,

Much of the present knowledge about frost action stems from the early work of Tabero and BeskowT. More recently Haley et al8, ftu6kliie and Jumikislo' 11' 12 have made notable contributions. Present-day students of frost action are in a fortunate position since, in 1952, Johnsonls published a comprehensive review of literature in this field for the period 1865-1951.

Most cases of severe frost action in soils can be attributed to the formation of ice lenses which initially cause heaving and subsequently result in the loss of bearing strength. This paper deals with the mechanism of ice lensing at some length because it is believed to hold the key to the understanding of frost action in soils and should assist also in the formulation of more adequate frost action criteria.

Study of Frost Heoving in the Loborotory The study of frost action in the labora-tory may be attacked in two ways. In the more practical approach an attempt is made to subject soil specimens (either undisturbed or prepared) to the same conditions in the laboratory as exist in the field. In the past, such work has been largely motivated by the urgency for obtaining some guidance in predict-ing the performance of soil under season-al freezing conditions. To a large extent, this approach has been used by the U.S. Corps of Engineers, the Ontario Depart-ment of Highways and several other organizations. Often it serves as a basis for design recommendations. Recognizing the usefulness of this approach there are, nevertheless, many inherent disad-vantages. The main one is that the simulation in the laboratory of the com-plex natural field conditions is at best an approximation.

The second approach is more funda-mental and recognizes that field condi-tions cannot be reproduced with com-plete success. The research worker focuses attention on a limited aspect by arbitrarily, but eftectively, controlling the conditions involved. Such studies are designed to elucidate the fundamental nature of frost action and eventually to provide a realistic and rational approach to the solution of frost action problems, not only in soils but in all construction materials subjected to frost. This ap-proach was used to some extent bY Beskowz in his mpnumental work and more recently by Jumikisro' 12 and was adopted in the current work of the Divi-sion of Building Research.

A Description ol Frost Heaving The formation of ice lenses, which occurs in almost all frost action prob-lems in soils, can be easily achieved in an apparatus such as is shown in Fig. I' and normally results in frost heaving* in * The formation of ice lenses does not always cause heaving, as for instance, in shrinkage clay with no outside water supply. In soils where the solids form a rigid structure, the amount of heave is equal to the sum thickness of all the ice layers. Intermediate situations are also possible.

excess of the expansion when water freezes. The details of the apparatus have been previously describeda' 5; suf-fice it here to say that it provides a means of freezing a small soil specimen unidirectionally under closely controlled conditions of temperature and moisture supply. (Fig. 1)

For ice lensing to occur, a supply of water must be available either from an external source such as a high water table (open system) or from within the unfrozen soil mass which results in a reduced soil moisture content (closed system). It must also be realized that the freezing of soil, even though it is saturated, does not necessarily result in ice lensing. An arrangement of individual particles that provides small enough pores is also necessary. When these fine pores exist the freezing of the water in them

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S A L E I N I N C H E S

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S E C T I O N T H R O U G H F R O S T C E L L

produces an effect similar to that of drying at that point. As in the case of drying where water moves from wet regions to the drying face, so too water

will move to the freezing zone from the unfrozen soil. Liquid water moves from wet regions to dry regions in a homo-geneous soil because a difference in "suction" exists. The movement of water in soil due to a suction difference is not different from the action of dry blotting paper when brought in contact with a drop of ink. In the case of ice lensing, the suction is brought about by the change of water to ice at the freezing zone. Water flows from the unfrozen soil to the freezing zone to equalize the suction but at the same time the ice lens is growing and the suction difference is maintained.

It is of interest to consider the exact circumstances for a particular ice lens to continue growing and the circum-stances for the frost line to advance. When water freezes the process is ac-companied by the release of heat. If this heat is not removed from the zone of freezing it causes the temperature to rise at that point. There is also the "conducted" heat to consider which is the normal outflow of heat that is caused by the cold temperature at the surface of the ground and the warmer tempera-ture at depth in the soil. Thus the heat extracted from the frozen soil consists mainly of "conducted" heat and the heat released when water freezes which is called "heat of crystallization". When more heat is removed through the frozen soil than is conducted to the freezing zone, one of two things can happen: either the additional heat is made avail-able by lowering the temperature of the soil, or it may be supplied by the freezing of water. As long as sufficient water can be moved to the freezing zone to supply this additional heat the frost line re-mains stationary and the ice lens can grow indeflnitely. Should the supply of water be insufficient, the temperature of the soil is lowered and the frost line advances until a more favorable water supply is encountered. This results in multiple ice lens growth as shown in Fig. 2.

In recent literatures, rz it has been shown that a suction (also called negative pressure or moisture tension) is developed beneath the ice lens which acts as a "driving force" for moisture movement.

Fig. 2 Ice lenses (dark portion - ice; light portion - silt).

Whenever moisture movement is caused by a suction gradient rather than a posi-tive hydraulic pressure gradient the prin-ciples of unsdturqted not saturated moisl-ure flow must govern the moistmoisl-ure move-ment characteristics.

Within certain well known limitations the saturated permeability coefficient is independent of the hydraulic pressure. In unsaturated flow the coefficient of permeability is a function of the average moisture tension and is inversely related for any particular soil. This is adequately described in soil science literature.

A high rate of frost heaving is usually observed in silty soils and deserves special attention based on the present "suction theory" concept. The suction developed at the frost line depends on pore sizel that is: the smaller the pore, the higher the suction. In spite of the relatively high permeability of coarse-grained soils, the flow of moisture is limited by the suction potential. In heavy soils, the suction developed may be large but the flow is limited by the permeability. The intermediate condition in silty soils with respect to both permeability and suction appears to be conducive to a high rate of heave. This is shown diagrammatical-ly in Fig. 3.

The contribution in the vapor phase to the over-all moisture flow is also recognized. Although research workers agree it is of much less significance than liquid flow in most cases of frost action, the exact contribution is not known.

The over-all result of ice lens forma-tions is the apparent expansion of the

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soil and the simultaneous development of heaving pressures whe[ever this ex-pansion is resisted which are sometimes sufficient to disrupt large structures. The nine per cent expansion of water in freezing contributes to the total heave but is normally not considered to be a major factor in frost action. The pos-sibility of damage from this effect in certain cases should not, however, be ignored.

The Basic Process in Frost Heaving The formation of an ice lens in the soil obviously requires that a certain amount of work has to be done a) to lift the frozen soil plus any additional surcharge and b) to maintain a suction gradient acting as a driving force for the moisture movement.

As was shown in Fig. 3, if a coarse-grained soil such as a gravel or sand is frozen unidirectionally no ice segrega-tion occurs even when ample water is available. By mechanically reducing the grain size of the material, for example, to that of silt, characteristic ice segrega-tion occurs and heaving is observed. In essence, the only difference that exists in the two systems is in the size of the pores.

Fig. 4 shows an enlarged section of two soil pores representing two soils. This flgure illustrates that the temperature below freezing at which ice can propa-gate through the soil pore depends on the size of the pore*. The greater the freezing point depression, the more work the system can perform. Under these conditions one has a kind of heat engine which is capable of lifting the frozen soil and also of moving water to the frost line. The depression of the freezing point appears to be necessary for such a system to operate. (Fig. )

Surrounding each particle of soil is a layer of water known as the "adsorbed" layer. The ice lens sits directly on top 'n Theoretical justification for this

state-ment is based on the following equa-tion:

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r : radius of curvature of the spherical crystal in its own m e l t ;

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solid and liquid; Qr : heat of fusion;

Tm : the temperature of melting at zero curvature of the solid/liquid interface; and Al : the depression in freezing

ooint below Tm.

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A N E N L A R G E D S C H E M A T I C D I A G R A M O F T S O

of the soil particles separated only by the adsorbed layer of water. In the lens growing process, molecules of water from the adsorbed layer become attach-ed to the ice (and become part of it) which reduces its thickness. This can be replaced from water in the soil pores. In turn, the water removed from the pores can be replaced from a high water table. The connecting link between the pore water and the ice lens is the ad-sorbed layer of water on the soil parti-cles which is believed to have great significance in ice lens growth. In a "closed" system the ice lensing stops when a particular moisture suction is reached which is controlled by the size of the soil pores through their influence on freezing point depression.

Ice lensing can also be stopped by loading, even when an adequate water supply is present. The critical load to stop frost heaving increases with de-creasing pore size. Pressure on the ad-sorbed water between the soil particle and the ice lens lowers its freezing point, thus decreasing the resultant driving force. It is also known now that the positive pressure developed in frost heav-ing depends on the soil moisture status or, more precisely, on the moisture ten-sion. Current investigations under way at the Division of Building Research are concerned with the determination of the exact inter-relationships that exist.

Some experimental evidence support-ing the foregosupport-ing suggested mechanism is available. Table 1 shows the maximum soil moisture suction induced owing to ice segregation in a number of soils. The soils were all saturated at the beginning of the experiments. The lowest suction

induced was in the coarsest material used and the highest suction in the most finely textured soil. Subsequent experi-ments gave further substantial evidence that the moisture suction induced by ice segregation in a given material is depen-dent on pore size. In these experiments, the pore size was varied by changing the density. In the material used (Potter's flint) a moisture tension of 350 cm of water was developed at a density of 1.6 and 560 cm for a density of 1.74. In experiments now in progress the heaving pressures and moisture tensions are being measured simultaneously and appear to be inversely related. Such relationships are of practical and theoretical interest; more details on the theoretical aspects are given by Powersla and Goldl5.

Diickerr6 believes there is no dividing line between frost-susceptible and non-frost-susceptible soils on the basis of the mechanical components of the system, and stresses'the importance of the chem-ical and mineralogchem-ical nature of the clay fraction. The importance of the clay fraction is recognized by most workers in the field of frost action' Kaolinites are considered to be the most frost-susceptible and montmorillonites the least frost-susceptible with the illites occupying an intermediate position. The danger of iron oxides and colloidal or-ganic matter is also known. The in-fluence of these components would, to a large extent, depend on the pore struc-ture of the non-colloidal fraction. Frost action in soils is, nevertheless, a serious problem in the absence of all colloidal material and this merely adds one fur-ther complication. Suction (Ft. of Water) 164.5 1 5 . 0 4.4 1 . 0 Tesrr I

The Relation Between Soil Texture and the Maximum Tension Induced by Ice Segregation in a Closed System

.Sample Composition

55/o clay, 33Vo silt, l2Vo sarJ.d 4Vo clay, 787o srlt,

l8Vo sand Ottawa sand pass

325 Ottawa sand

200-325

Per cent Moisture Content when Frost Heaving Ceased

34.6 25.3 3 1 . 3 30.6

Frost Action Under Noturol Conditions Under natural conditions the frost action process does not proceed in the same orderly fashion that prevails in the laboratory. This is largely because of the influence of climate on two of the three important factors, namely, tem-perature and moisture supply. In addi-tion, the heterogeneity of the material is recognized as a further complication unless it is given special attention. Uni-formity of all conditions governing frost action are particularly desirable since, in the absence of uniformity, difierential heaving may be promoted. This is al-most always more serious than uniform heaving, particularly in highways.

While the nature of frost action is still not completely understood, the know-ledge gained from research does offer some basis for appraisal of the frost action problem in the field.

Air Temperatures and Vl/ater Supply as a Break-up Index

Frost-susceptible soils do not neces-sarily heave to the same extent each year, nor will spring break-up occur with equal severity. Because of this and the frost-susceptible nature of many im-portant roads in use, attempts have been made to predict the seriousness of spring break-up as a basis for regulating traffic loads during the critical period.

As an index for predicting spring break-up Dolchl? used the product of the freezing index* and the rainfall in the 30 days prior to freeze-up. This was in part modified by Crawford and Boyd3 by replacing the second factor with moisture stored in the soil at freeze-up. This also proved only partially success-ful. The use of such a break-up index implies that cold winters result in severe * The "freezing index" is a summation

of the "degree days" for any one year. The unit employed, "degree day", is the declination from 32'F in the mean air temperature for one day. For ex-ample, if the mean air temperature for a given day was 30'F this would constitute two "degree days". Long-term averages of the "freezing index" are sometimes used to depict general climatic resions.

spring break-up and for this there is no evidence. Colder winters than normal usually cause a deeper penetration of the frost line, other things being equal, which might result in greater frost action dam-age if frost-susceptible strata are inter-cepted at depth. On the other hand, during relatively mild winters severe frost heaving may occur resulting in serious .spring break-up because of the shallow position of the frost line. Fur-ther, it could not be expected that the conditions which intimately surround a particular location (micro climate) can be assessed on the basis of general tem-perature conditions and moisture stored over a large area.

Frost Penetration and Snow Cover The usefulness of the freezing index for predicting the soil temperature and depth of freezing is generally recognized. A map showing freezing index contours for Canada was prepared in 1953 by Wilkins and Dujayrs for runway design purposes. Many factors may influence the exact relationship between depth of frost and the freezing index that need not be discussed here except for the in-sulating effect of snow cover. Legget and Crawford2 concluded that at Ottawa snow cover will reduce frost penetration by an amount equal to or greater than its own thickness. The relationship be-tween freezing index, snow cover, and frost penetration is given in Fig. 5.

r y . 5 D t d d & d t u d t u k s d d d

When high snow banks are built up over the shoulders and ditches a distort-ed frost line will result. The frost line will penetrate more deeply in the snow-cleared road than in the snow-protected roadsides. Thus, the supply of water in a lateral direction may result in a shorter flow path than if the frost line had been permitted to penetrate uniformly. During the thawing period the snow-cleared road will thaw more quickly than the snow-protected sides, resulting in a "dished" thawing front which may cause water to pond in the roadbed arrd prevent moisture redistribution. Under such conditions, roads often become impassable due to the complete loss of bearing strength.

Soil Condition and Soil Moisture The most often quoted frost action criteria for soils are based on grain size and, to some extent, on grain-size distri-butionle. Well-graded soils are consider-ed frost-susceptible if more than three per cent by weight is finer than 0.02 mm. In a uniform soil up to 10 per cent finer than 0.02 mm is permitted. There are also countless variations of these criteria in the literature. Experience has shown that there are many cases where the criteria have proved inadequate. On the basis of current research, it appears that

the pore size and pore-size distribution of the soil should be a direct considera-tion in any frost acconsidera-tion criteria. It is believed that the characteristic moisture release curve of a soil, which is the relation between moisture suction and moisture content. should be considered in the evaluation of frost susceptibility. This curve can be interpreted in terms of pore diameter and pore-size distribu-tion.

Homogeneity of the subgrade and the sub-base in highways reduces differential heaving. It follows that the contamina-tion of sub-base materials with clay or other fine materials should be avoided. It has been shown experimentally that only slightly frost-susceptible soil may very effectively transmit water to clayey lenses intercepted by the frost line. Fig. 6 shows the heave-time relationships for a saturated soil which heaved 0.3 inches in a closed system. Its moisture content when heaving stopped was 25.3 per cent. The upper curve gives the heaving characteristics of the same soil but with the ice lens growing in a layer of clay. The ice lens growing in the clay was able to reduce the moisture content of the soil beneath it to 71.2 per cent. (Fig. 6)

1 . 4 1 . 3 1 . 2 t . l A t ' o

H . o

o 2 . 8 . 7 Ll

H . s

I DAY 2 D A Y S 3 D A Y S 4 D A Y S 5 DAYS F I G U R E 6 T H E A M O U N T O F H E A V E V E R S U S T I M E S H O W I N G T H E A D D E D H E A V E F R O M S A M P L E N o . 6 W H E N T H E F R E E Z I N G Z O N E I S L O C A T E D I N A L A Y E R O F F I N E R T E X T U R E D S O I L ( N o . 3 )

FINAL MOISTURE CONTENT

> S A M P W I T H - E N o 3 O V E R ! F R E E Z I N G Z O N ; A M P L E N o 6 -: l N N o 3 S A M P L E 6 i ,,' F I N A L M O I S T U R E C O N T E N T 2 5 3 % , p F 2 6 6 |

'Ihe _{question of drainage (internal and} external) is also of utmost importance. A soil showing no heaving characteristics under a limited water supply may be extremely dangerous when wet condi-tions occur. Critical locacondi-tions in road-ways, such as in soil cuts and rock-frll transitions, should be given special at-tention, particularly if borderline soils must be used.

The loss of bearing strength when the moisture content is increased depends on the nature of the soil. In addition to the high rate of heave in silty soils they are also known to be extremely sensitive to a small increase in moisture in the wet region. Complete loss of strength or stability may occur with a moisture increase of two to three per cent. The whole field of thawing and loss of stability appears to have been neglected thus far in frost action re-search, particularly in relation to soil type.

The Use of Additives to Reduc: Frost Heoving

The use of additives to reduce frost heaving in soil is becoming of more interest since in many areas the reserves of satisfactory materials have been depleted. In many cases, the materials available are satisfactory from every other standpoint except for the danger of frost action. It would be desirable under these conditions to render these materials non-frost-susceptible.

Dr. Lambe2o has described the results of a three-year search for additives car-ried out in co-operation between M.I.T. and the Arctic Construction and Frost Effects Laboratory. The additives studied were classified according to their action: a) void pluggers and cement, b) aggre-gants, c) dispersants, and d) water-proofers.

Dr. Lambe concludes that the disper-sants have shown promise both in the laboratory and in a small-scale field ex-periment but that more field testing is required. Uniform silts and moderately plastic clays were the least responsive to treatment but "dirty" gravels, sandy clays and silty sands, which were most responsive, could be economically treated. The use of waste sulphite liquor for preventing frost action damage has been

studied extensively at the University of Alberta. Hardyzr,22 reports on labora-tory tests with silty soil types treateC with waste sulphite liquor. Both in the labora-tory and under field conditions this treat-ment shows promise. The exact way in which sulphite liquor affects the ice lens-ing mechanism has still not been worked out other than it is known to reduce frost heaving.

Speciol Problems in Frost Action Unless certain special provisions are made, the soil may become permanently frozen beneath cold storages. This is because the cold regime in the cold storage dominates the temperature dis-tribution in the soil to some depth. In consequence, the soil remains frozen during the summer and frost line aC-vances during the winter until some equilibrium position is reached. The freezing of the soil beneath the floor of the cold storage in itself is not serious. However, if these soils are frost-suscep-tible all the manifestations of frost action become evident, such as moisture move-ment, development of pressures, and dis-placement due to ice lensing. Sufficient destruction to the building can ensue to completely disrupt its operation.

The problem of frost action is not confined to areas of seasonal frost but may be encountered also in areas of permafrost23,24 where, because of low average air temperatures, the earth's crust is frozen to considerable depths. A shal-low layer at the surface thaws each summer and is known as the "active" Iayer. It is in this layer that the prob-lems of frost action are similar to those in areas of seasonal frost.

Permafrost is normally a good founda-tion material provided it is not permitted to thaw. Stripping of the surface cover or other interference with the frozen character of the material results in severe subsidence due to the high ice content.

The forms of ice accumulation in the active layer appear similar to those at greater depth, consequently its thickness cannot be determined from borings in the frozen state. A method of identify-ing the active layer would be useful in exploratory surveys for new development sites, access roads and airports, etc.

While the character of the problem is different in permafrost, the important factors - temperature, soil, and water - _{are the same. The thick ice strata} sometimes encountered in the north have in the past been thought to be remnants of an ice age. This now appears doubtful since under the right conditions great thicknesses of ice can be formed by the ordinary frost heaving process described in this paper. One would then not ex-pect to be able to detect differences be-tween the active layer and the perma-nently frozen material on the basis of ice segregation.

Basic information on the nature of frost action is also important in estab-lishing performance evaluation tests for many rigid porous materials used in the construction industry which are period-ically subjected to freezing. Cyclical freezing may be particularly destructive as, for example, in bricks, mortar, and concrete. The formation of ice lenses undoubtedly occurs during the freezing of fresh concretes and mortars. It has not yet been established that in rigid materials the forces involved in ice lens-ing are significant and it may be that the main efiect will be found to be due primarily to the expansion of water on freezing.

Conclusions

Fundamental frost action research in the laboratory is useful in helping to understand the complex nature of frost heaving, and it is believed some sub-stantial advance has already been made. As more knowledge is gained about the processes involved, the search for more adequate frost action criteria and modi-fying additives can proceed in a more scientific way. While the paper has dealt with the heaving process at more length and in more detail, the influence of climate on soil temperatures and moisture is equally important. Frost acticn research consists of more than just a consideration of the properties of the porous material.

The research carried out so far by the Division of Building Research suggests that the frost action criteria concerned with the mechanical composition should be based on pore size and pore-size dis-tribution since the mechanism is

inti-mately associated with the pore system. This line of research is being pursued further by the Division of Building Re-search in addition to the continuing measurements of soil temperatures at many locations in Canada. Particular attention is being given to prediction of soil temperature distribution from me-teorological data.

Many scientific papers and also a few books have been written on the subject of frost action. Many of the ideas ex-pressed in this paper are not original and can be found in the literature. It is hoped, however, that the author, has re-stated some of the more important ele-ments of the phenomena in a way which will be helpful to the practising engineer.

Summory

(D Frost heaving generaily results from the growth of ice lenses in the soil, a process that occurs in most of the serious problems of frost action in the field; (iil _{It is believed the mechanism of ice} lensing can be best understood in terms of a theory based on the dimensions of the pore structure. In this way the heaving pressures and the suction gradient induced by ice segregation can be at least in part explained;

(iii) The most rational approach to the solution of the frost action problem in the field takes into account all of the known factors involved, namely: consti-tution of the soil, soil-moisture relations, and the influence of climate on moisture and temperature conditions;

(iv) Interference with a horizontal frost-line penetration due to snow removal and the lack of uniformity in soil conditions and drainage may seriously aggravate frost damage in roads.

Acknowledgments

The author wishes to express his ap-preciation to Dr. N. B. Hutcheon for l:is guidance in preparing this paper, and to Mr. R. F. Legget, Director of the Division of Building Research, for his continuing interest in frost action prob-lems and with whose approval this paper is published.

References

(1) Crawford, C. 8., "Soil temperatures (a review of published records)":

Highway Research Board, Special Report No. 2, 1952. p. l7-4O. (2) Legget, R. F. and C. B. Crawford,

"Soil temperatures in water works practice": Journal American Water Works Association, Vol. 44, No. 1 0 , 1 9 5 2 . p . 9 2 3 - 9 3 9 .

(3) Crawford, C. B. and D. W. Boyd, "Climate in relation to frost ac-tion": Highway Research Board, Bulletin No. 111, 1955. p. 63-75. (4) Penner, E., "Soil moisture

move-ment during ice segregation": High-way Research Board Bulletin No.

1 3 5 , 1 9 5 6 . p . 1 0 9 - 1 1 8 .

(5) Penner, E., "Soil moisture tension and ice segregation": Presented to 1957 Annual Meeting of the High-way Research Board. (In Press) (6) Taber, S., "Frost Heaving":

Jour-nal of Geology, Vol. 37, No. 5, 1924. p. 428-461.

(7) Beskow, G., "Soil freezing and frost heaving with special application to roads and railroads, (1935)": Tran-slated by J. O. Osterberg, Tech-nological Institute, Northwestern University, 1947.

(8) Haley, J. F. and C. W. Kaplar, "Cold room studies of frost action in soils": Highway Research Board, Special Report No. 2, 1952, p.246-267.

(9) Rucklii, R., "Der Frost im Bau-grund": Springer Verlag, Vienna 195O. 279 p.

(10) Jumikis, A. R., "Suction force in soils upon freezing": Proceedings American Society of Civil Engi-aeers, Vol. 80, No. 445, 14 p. 1954. (11) Jumikis, A. R., "The frost penetra-tion problem in highway engineer-ing": Rutgers University Press, 162 p. 1955.

(12) Jumikis, A. R., "The soil freezing experiment": Highway Research Board, Bulletin No. 135, 1957. p . 1 5 0 - 1 6 5 .

(13) Johnson, A. W., "Frost action in roads and airfields, A Review of Literature 1865-1951": Highway Research Board, Special Report No. 1, 1952. 287 p.

(14) Powers, T. C., "Resistance of con-crete to frost at early ages": Sym-posium on Winter Concreting, RILEM, Copenbagen. October 1956

(15) Gold, L. W., "A possible force mechanism associated with the freezing of water in porous ma-terials": Presented to 1957 Annual Meeting of the Highway Research Board. (In Press).

(16) Diicker, A., "Gibt es eine Grenze zwischen sicheren und frost-empfindlichen Lockergesteinen" : Strasse und Autobahn. Vol. 3. 1956. p. 78-82.

(17) Dolch, W. L., "A survey of winter weather": Indiana Preliminary Report, Purdue University, Septem-ber 1952. 4l p.

(18) Wilkins, F. B. and W. C. Dujay, "Freezing index data influencing frost action": Proceedings of the 7th Soil Mechanics Conference, National Research Council, Asso-ciate Committee on Soil and Snow Mechanics, Technical Memorandum No. 33, 1953. p. 36-4O. ( 19) Casagrande, ,{., "Discussion of

frost heaving": Proceedings, High-way Research Board, Vol. ll,1932. p. 168-172.

(20) Lambe, T. W., "Modification of frost heaving of soils with addi-tives": Highway Research Board Bulletin No. 135, 1956. p. l-23. (21) Hafty, R. M., "Research underway in the Department of Civil Engi-neering, University of Alberta": Proceedings of the Seventh Cana-dian Soil Mechanics Conference. National Research Council, Asso-ciate Committee on Soil and Snow Mechanics. Technical Memorandum No. 33, 1953. p. 23-27. (22) Hafiy, R. M., "Prevention of frost

heaving by injection of spent sul-phite liquor": Proceedings, Third International Conference on Soil Mechanics and Foundation Engi-neering, YoI.2, 1953. p. 103-106. (23) Pihlainen, J. A., "Permafrost

re-search": Proceedings of the Con-ference on Building Research. Na-tional Research Council, Division of Building Research, Bulletin No. l, p. ll7-r20, 1953.

(24) Legget, R. F., "Permafrost Re-search": Arctic Institute of North America, Special Publication No. 2,

A l l s t o f a l I P u b l l c a t J . o n s o f t h e D l v l s l o n o f B u l l d l n g R e s e a r a h 1 s a v a l l a b l e a n d m e y b e o b t a l n e d f r o m t h e P u b l l c a t l o n s S e c t l o n , D l v l s l o n o f B u l l d l n g R e s e a r c h , N a t l o n e l R e s e a r c h C o u n c 1 1 , 0 t t a w a , C a n a d a .