ENGINEERING, DESIGN, AND EQUIPMENT have any requirements for a period of several months but then may need delivery, within a day or two, of substantial quantity. Because of the erratic timing of orders and the fact that a single job may require many tons of stabilizer, large inventories of the product are essential. Furthermore, we have adopted the practice of sending one of our technical staff to advise the customer \?-hen a shipment of stabilizer is delivered. His presence can be important to the successful use of the product until the customer has become thoroughly familiar with it. This is a customary technical service in the chemical industry. Actually, the only sharp difference in marketing soil chemicals is the need to supply large quantities and a technical serviceman without advance notice. Special distribution channels will eventually be required for stabilizers since the number of potential customers is very large and scattered widely from a geographical standpoint. Thus, the development of soil stabilizers is, from start to
finish, a difficult task. What is the goal that apparently justifies these efforts? We believe the markets for chemicals that can modify the engineering properties of soil are extensive and practically unexplored. They represent virgin territory for chemical research and development and promise a sizable new outlet for chemicals. As I have tried to point out, this research and development requires some modifications in the techniques to which we in the chemical industry are accustomed. If we can be sufficiently aggressive and imaginative to adapt ourselves t o these new techniques, our efforts should be amply rewarded. Literature Cited (1) Lauritaen, C. W., IND. ENG.CHEU.,4 7 , 2245 (1955). R E C E I V Efor D review April 6, 1965.
ACCEPTEDJuly 19, 1955.
Civil Engineering Need for Soil Chemicals 7.WILLIAM L A M B E SOIL STAElLlZATlON LABORATORY. MASSACHUSETTS INSTITUTE O F T E C H N O L O G Y . CAMBRIDGE. MASS.
T h e article describes m a n y civil engineering problems for which chemicals t o alter oil pr perties are needed. While t h e m a x i m u m permissible price of soil additives varies f r o m less t h a n one cent a pound t o over $5.00 a pound, t h e most promising are those effective a t t r e a t m e n t levels of less t h a n 1% of t h e soil dry weight and costing less t h a n 10 cents a pound. T h e types of chemicals most promising and some of t h e development problems are discussed. W h i l e t h e prospects for soil additives are bright, m u c h work remains t o be done.
I'
RECENT years construction has become one of the largest industries in the United States; more striking than its growth is its change in nature. This increase in volume and change in character is most evident in the building of our transportation facilities, especially highways. The 10-year program, costing 101 billion dollars, proposed by President Eisenhower reflects the need of highway modernization and expansion for proper communication and commerce in the United States. The wheel loads to which our roads and airfields are being subjected have increased a t a more alarming rate than have any number of vehicle passes. The main causes are the expansion of the heavy trucking industry and development of large commercial planes-maximum airplane wheel loads are now five times heavier than those of 10 years ago. The severe loading conditions require that the most advanced methods of design and procedures of construction be employed. Accompanying the more severe design conditions is the rapidly dwindling supply of select construction and foundation soils. Granular soils used in pavement bases are already exhausted in many areas of the United States. Roads and airfields are being placed at sites which in past years would not have been considered because property damage costs involved in land takings have become the controlling factor in the selection of many highway locations, especially in metropolitan areas. All these factors-increased construction volume, more stringent design conditions, and growing shortages of select soilshave greatly extended and expanded the need and interest in I
2234
additives to alter soil properties. The alteration of soil behavior for engineering purposes, soil stabilization, has been furthered by two important things:
1. The significant progress made in delineating the chemical, structural, and physical nature of soils-soil technologyespecially those composed of fine-grained particles 2. The availability of many new chemicals Soil stabilization has marched from Edisonian experimentation to a budding science. The increasing interest of the research-minded chemical producers and equipment manufacturers in soil stabilization is encouraging and should prove an important contribution to the science. Certainly those who make potential soil additives and machines to incorporate them must take a major part in their development. For their own good these manufacturers should be prepared to give considerable aid and advice t o the engineer who use3 their products. Much study in soil stabilization has been furthered by military interests. While the requirements of civil and military engineers are quite similar, there are many civil applications that are of secondary military interest and have, therefore, received limited consideration in military sponsored projects. The construction industry and its engineers have not been as responsive to new materials and techniques as the researcher and promoter would like. This conservatism arises from several factors.
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 47, No. 11
SOIL STABILIZATION
WATER
Figure 1.
CONTENT
IN
% DRY SOIL W E I G H T
Strength of clay as function of moisture
cost of regular stabilizers is, however, severely limited. Pr oblems where regular stabilizers n ould be considered can usually be solved completely b y removing the troublesome soil and replacing i t with gravel. Gravel normally costs from 81.50 to $3.50 a cubic yard in place. A stabilizer, effective a t 10% level, would have to sell for one cent or less per pound to compete with replacement by gravel. While this price is the extreme case, it does furnish a guide post. The supply of gravel is dwindling in many parts of the country; in these places granular material is being made by crushing stone. Portland cement, the most widely used soil stabilizer, sells for less than one cent a pound, thus meeting the cost requirements. k new material has got to be cheaper, or be more effective, than cement or do something cement cannot in order to be a serious competitor for regular stabilization. There are many problems where only a relatively minor change in soil property is needed. The increasingly rigid specifications for pavement base-course material, for example, cause many soils t o be rejected even though they narrowly miss being acceptable. Millions of tons of these borderline soils are discarded that could be used if only a modest improvement in their properties could be effected. While the permissible additive cost per volume of soil treated is the same for trace FLS for regular stabilizers, the unit cost is higher because less is used. For treatment levels of 1 to O.Olyo,the perinissible unit cost ranges from 5 cents to over $1.00 per pound. IX
N O T E : SAMPLES MOLDED.DRIED.REWET. THEN TESTED
1. iZ large pekentage of construction involves public funds. 2 . There is usually little personal incentive to the designing engineer t o save money. 3. The designer is open t o sharp criticism for the failure of a new material or technique. 4. The civil engineer is often naturally more backward than other engineers because his, t h e oldest form of engineering, is built on more of an empirical technical base accumulated from extensive “field experience” than on scientific principles which are the products of research.
The civil engineer is, however, becoming more receptive to new materials to improve the soil. The purpose of this paper is to describe some of the many soil problems for which the engineer needs soil stabilizers. There is no such thing as one additive to correct the myriad problems in all soils. This paper describes some soil problems and suggest possible additives for their amelioration. At the outset it is important t o realize that any additive that can change any physical property of any soil is worth preliminary consideration. Practical problems are presented that illustrate the need for additives to alter all the major properties of soil either way-i.e., increase or decrease. The cases presented have come t o the author’s attention from three major sourceshis experience as a consulting soil engineer, his discussions with other engineers, and distress calls which have come to him. Permissible Costs of Soil Additives
The permissible unit cost for a soil additive to be used in military combat conditions is obviously much higher than that for materials to be used in military peacetime or civilian construction. Combat conditions are not considered in this paper. For cost considerations, soil additives can be divided into three groups :
1. Regular stabilizers, such as portland cement, normally used at levels of 5 t o 15y0 based on the soil dry weight 2. Trace additives, used at levels of 1% and less 3. Special additives, employed on unusual jobs of limited extent There is the greatest potential market volume for materials which fall in the first group-i.e., regular; the permissible unit
November 1955
I G b X II IS MOLDING
Figure 2.
It3
17
WATER
18
CONTENT
I
I
I
19
20
21
IN $6 DRY SOIL WEIGHT
Modest improvement i n water resistance of Virginia sandy clay
There are special problems, usually involving a limited volume of soil, where the cost of a n additive is of almost no concern. There are occasions where a few cubic yards of inaccessible soil must be treated; chemicals costing over $5.00 a pound would be used unhesitatingly t o solve many such problems. The potential market for these high priced, speciality chemicals is considerably smaller than for the regular or trace chemicals; the engineering know-how needed with the use of these specialities is, however, a t least as great and probably greater than with the other stabilizers. Alteration of Soil Strength
The great majority of all problems the soil enpirieer encounters involves soil strength; further, most of the soil strength problems arise with fine-grained soils. The chemical additives for which the engineer has the most critical need and for which there is the largest potential market are those which alter the strength characteristics of fine-grained soils. Strength additives are needed t o 1. Maintain soil strength under varying moisture conditionsi.e., give water resistance or waterproof 2. Increase soil strength 3. Decrease soil strength
INDUSTRIAL AND ENGINEERING CHEMISTRY
2235
ENGINEERING. DESIGN. AND EQUIPMENT
Figure 3.
Waterproofing Virginia sandy clay w i t h t r i chloromethylsilane
Water Resistance. The soft and sticky clays that plague the builder behave in an exemplary fashion when dried. Figure 1 shows a compressible clay, which has cost Bostonians millions of dollars in expensive structure foundations, has essentially no compressive strength a t its natural water content of 30 to 50y0 but 1600-pound per square inch strength when dried. On exposure to moisture the dry clay rapidly imbibes water and loses all its strength. The value of a treatment to prevent the deleterious effect of water attack on a dry soil is, therefore, apparent. A soil waterproofer could be used in many soil problems. Successful waterproofing would permit higher allowable footing loads, the use of clays for airfield and highway pavement bases, a great reduction in the erosion of unprotected clay slopes, construction of canal liners of clay, and construction of earth buildings. One major obstacle to the wide use of waterproofers is the need to dry the soil. How, for example, can a foundation clay below the water table be economically dried? A use of waterproofers that stimulates the philanthropist is the treatment of sun dried clay so that it becomes building material. I n parts of the world-Egypt and Israel-soil is about the only locally available building material. The natives of these areas have for many years built dwellings and other small structures of sun-dried earth. The success of these earth structures, by our standards, is generally poor. A cheap waterproofer that could be sprayed on the earth surfaces exposed to the weather to render them resistant would permit a rise in the living standard of many Asians and South Americans, as well as permit more comfortable houses in all areas. There are numerous waterproofers-ranging all the way from camel dung used by the Egyptians and others to the new and wonderful silicones studied in the laboratories a t Massachusetts Institute of Technology and elsewhere. Bitumen, costing in the one cent a pound range, is a waterproofer that is effective to a limited degree in fine-grained soils; incorporation difficulties, the high treatment levels often required, and sometimes un-
2236
predictable results have restricted the use of bitumen with the cohesive soils. Bitumen is widely and successfully used with noncohesive soils. Dispersants, incorporated in fine-grained soils prior to compaction, improve the structure of the soil and thereby impart a modest but significant amount of water resistance (Figure 2). The water soluble silicones can essentially completely waterproof soil (Figure 3 ) . The soil was treated by thoroughly mixing the soil and silicone and then air-drying. The treated specimen (upper left, Figure 3) resists the slaking effect of water, while untreated specimen (upper right, Figure 3) collapses in the presence of water. The bottom of Figure 3 shows that the treated soil, unlike the natural soil, will float. Attempts to waterproof dried blocks of clay by coating the surfaces with silicone and then drying have not been very successful. Water works back of the waterproofed surface through any untreated pinhole or abraded area, resulting in eventual disintegration of the entire block. Minimum levels for complete treatment of soil are not much below 1% of the dry soil weight. A t such high levels-Le., 27 pounds of silicone per cubic yard of treated soilthe present unit cost of the chemical is many times too great for uses such as earth houses. Strength Increase of Cohesionless Soils. Mineral particles larger than approximately 0.05 mm. usually have little attraction to each other and those soils composed of such particles are cohesionless. These soils-coarse silts, sands, and gravels-are able to generate considerable strength through internal friction when they are confined. The engineer, therefore, seldom has strength problems with the coarser-grained soils when they are confined with more than a few feet of overburden. Additives are, however, needed and widely used to give strength to cohesionless soils near the ground surface, and thus not confined. Situations where cohesionless soils are given cohesion include slopes through cuts and fills, stream banks, excavations, and load bearing surfaces, such as roads. Anyone who has tried to drive, or even walk, through dry sand or gravel is well aware of the lack of strength of these Soils. The cheapest binder for cohesionless soil is cohesive soil which is used extensively in mechanically stabilized roads. For these
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Figure 4.
CONTENT IN % DRY SOIL WEIGHT
Aggregant as compaction aid for Virginia sandy clay
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 11
SOIL STABILIZATION ~~
roads, fines are added to coarse soils to bring the percentage finer than 0.07 mm. to a minimum of approximately 4%. Portland cement and bitumen are low cost soil additives and are widely and successfully used with cohesionless soils. Since the coarse soils have relatively large voids, they can be easily injected with cement or bitumen or viscous chemical fluids. Such injections are sometimes used to strengthen the soil. Strength Increase of Cohesive Soils. Clays often fail to possess sufficient strength, usually under wet conditions, to permit their use ad desired. Clay roads, unprotected clay slopes, canal and stream banks, and clay backfills are examples where higher soil strength is needed. Portland cement is used, to some extent, to treat clays. Acrylate salts will increase clay strength in a very short time but are not economical ifor normal usage. The difficulty of incorporating additives with plastic soils has retarded the development and use of stabilizers.with these soils. Strength Increase of Organic Soils. Deposits of weak and highly compressible organic soils are common in the U. S. and other parts of the world. These deposits have been a source of trouble and are becoming of even greater concern to the builders of roads, airfields, and structure foundations. On one section of the new’ Massachusetts East-West Turnpike there is, for example, at least one swamp in every mile; further, all three of the major airports in the New York City area are situated on orga,nic deposits. Presently used techniques to build on these deposits-such as to remove and replace them with granular material, consolidate them with surcharges, and drain them with sand piles-are very expensive and time consuming. There are no additives used to any extent to treat these weak organic soils. As with the inorganic clays, these organic soils are difficult to inject because of their low permeability and to blend mechanically with additives because of their plasticity and stickiness. These soils are usually
100
200
300
400
500
600
CUMULATIVE MIXING ENERGY IN METER GRAMS /GRAM OF CLAY
Figure 5.
Mixing characteristics of clay, water, and dextrose system
November 1955
~~
~~~
so weak that they will not directly support normal construction equipment. Additives to Aid Soil Handling. Fine-grained soils are often too wet and, therefore, too weak to permit their manipulation; heat from sun or burners is commonly employed to dry and strengthen them, For the not unrare occasion where such heat cannot feasibly be applied, additives which effectively dry soils are needed. Dry soil is sometimes added to soil which is too wet in order to dry it.
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i 24
Dispersant as compaction aid for Virginia sandy clay
Research a t Massachusetts Institute of Technology, as yet unpublished, has shown that trace materials called aggregants, which increase to a modest extent soil strength a t a given moisture content, can have a marked beneficial effect on the mixing characteristics of soil chemical systems. While these materials strengthen the soil and, therefore, require more work to manipulate them, they can decrease the degree of mixing obtained for a given work input. Studies have shown that often an increase of particle-particle attraction permits a more homogeneous distribution of the particles, since more particle displacement can be obtained. Fill material is usually placed a t that molding water content, called optimum water content, which permits the maximum compacted dry density to be attained. Many soils exist in the borrow pit a t a natural water content greater than the optimum molding content; these soils have to be dried before being used for fill. Figure 4 presents laboratory data on a Virginia sandy clay t o show that an aggregant will significantly increase the optimum molding water content. Thus, this soil, which is too wet to be compacted a t 2570 moisture, can be successfully comof an aggregant is added. pacted if Since the permissible cost per volume of soil treated for compaction aids is quite low, the expensive synthetic polymers used for soil conditioners are not economical. Consideration is now being given to inorganic salts of multivalent cations, such as ferric iron and aluminum, as compaction aids. Strength Decrease. Needed by the soil engineer are additives which can reduce the cohesion of fine-grained soils and thereby permit easier handling of the soil. Figure 5 presents laboratory data on the mixing characteristics of a clay, water, and dextrose system. The data show that the addition of sodium tetraphosphate permits the attainment of a given mixing uniformity a t a lower mixing energy, or the attainment of more
INDUSTRIAL AND ENGINEERING CHEMISTRY
2237
ENGINEERING, DESIGN, AND EQUIPMENT thorough mixing with a given amount of work. Figure 6, which presents laboratory data on a Virginia sandy clay, shows that dispersants have the opposite effect of aggregants on the compaction characteristics of soil. The dispersant reduces the amount of molding water required to obtain the maximum compacted density. I n arid regions a reduction in the quantity of water to be added to a soil would, of course, be desirable,
Alteration of Soil Permeability
Permeability Decrease. I n connection with structures for the storage of water and other fluids a decrease in the permeability of Boil is usually desired. For example, soils under dams the floors of reservoirs or ponds, and the linings of canals are often SO pervious that either excessive leakage occurs or the safety of the structure is endangered by the movement of soil fines. For the treatment of buried soil strata, such as dam foundations, more than 100 chemicals have been suggested or tried. Table I ( 1 1 ) lists 10 types of chemical injection processes employed for the injection of soil. An impermeabiliaing technique, developed in the Massachusetts Institute of Technology Soil Stabilization Laboratory by Lambe (12)and Barker and Becker (S), consists of injecting a solution of monomers (N-methylol-acrylamide or acrylamide with methylene-bis-acrylamide or calcium acrylate) and catalysts which polymerize in the soil voids to form a water sensitive gel. This technique possesses several desirable features, namely, the injected fluid is a low viscosity solution, and thus readily permeates small voids; the polymerization can be effected in a short time, minimizing the loss of chemical by leaching before reaction; all of the chemicals are injected in one solution, thereby avoiding multiple-step injection; and the polymer is water sensitive, thus reducing the required chemical to the order of 1% on the dry soil weight. This process has received practical use ( 7 ) . While any of the processes described in Table I could be used for the impermeabilization of easily accessible surface soils, most of them were developed for the injection of deep strata and are not economical for treatment of accessible soils. Extensive work a t the Massachusetts Institute of Technology Soil Stabilization Laboratory (IS) has shown that the permeability of fine-grained soils can be reduced by a factor of five- to twentyfold through the’ addition of a trace quantity of dispersant. This technique has been economically and successfully employed on several jobs (14).
Table 1. Kumber
Figure 7.
Frozen sample of halloysite (4H10) Heave = 230%
1
2
3 4
Soil density is not a fundamental soil property; the reason soils for fills are compacted t o maximum density is that usually such densification results in an increase of strength, a decrease of compressibility, and a decrease of permeability. When densification is accompanied by compaction aids, such as aggregants and dispersants, the property changes normally associated with densification may or mag not be obtained. Since the degree to which a soil can be compacted depends on the strength of the soil, one would normally expect that a soil compacted to its maximum density would have approximately the same strength as that soil compacted to its maximum density when treated with an aggregant or as that soil plus dispersant compacted t o its maximum density. Laboratory tests have indeed borne out this expectation. While compaction aids have little effect on the strength of the soil immediately after compaction, they do have an effect on the strength characteristics especially after a dry and wet cycle, as was shown in Figure 2. Soil compacted with chemical aids has permeability characteristics quite different from the untreated soil. The effects of these aids on the complete strength characteristics and on the compressibility have yet to be determined. Dispersants have considerable promise as additives to aid soil handling since they are effective in very low concentrations and are relatively cheap.
2238
5
6
7 8 9 10
Injection Processes
Process
Example
Dissolution Ion exchange
Reference
Acid to dissolve silica S a + for C a + + to reduce permeability Soil structure alteration Dispersant solution to reduce permeability Cooling of thermoplas- Cooling of molten sulfur tic. or molten materials Pore water freezing Freeze with C O L Metathetical precipi- Sodium silicate magtation nesium chloride Polymers Injection of acrylate monomers to form water-sensitive polymer Emulsion breaking Pine wood resin in alkali Suspension separation Silica in water Particle hydration Clay with protective coat
(.W (11) ( I , 8, 4, 6,810,16, 19)
+
is) ( 1 7) (6) (16)
The low permeability of fine-grained soils, especially organic soils, is a source of major difficulty to the engineer. When a deposit of saturated soil is subjected to a load, such as that from the placement of an overlying fill or structure footing, it cannot mobilize the added strength attendant to the increased confining pressure until some of its pore water escapes. The rate of pore water escape depends on the permeability of the soil. The purpose of sand drains, which are used extensively in organic soil deposits, is to accelerate drainage of the soil by furnishing flow paths of high permeability. The design of earth retaining structures is often controlled by rate which the back fill drains; further, settlements of buildings overlying compressive soil usually require a period of years, rather than harmlessly occurring during construction, because of low soil permeability,
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 11
SOIL STABILIZATION
.-
characteristics. This reduction is illustrated by Figure 8 which is a plot of data obtained by the Arctic Construction and Frost Effects Laboratory.
A ‘0 0
1
r W
a’ W
S u m m a r y and Conclusions
I
%
z
LL LL 0
w
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0.2
0.4
0.6
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1.2
1.4
DISPERSANT CONCENTRATION IN % DRY SOIL WEIGHT Figure 8.
Effect of dispersants on frost characteristics
Limited use has been made of additives to increase the permeability of soil. Injection has been used to increase the yield of oil and water wells; in connection wiLh studies on soil conditioners, researchers have studied the effect of these aggregants on increasing soil permeability (18). Research a t Massachusetts Institute of Technology Soil Stabilization Laboratory has shown that acid can be injected into fine-grained soils containing organic matter or carbonates to increase significantly the permeability. Alteration of Soil Compressibility
High compressibility, rather than low strength, is the primary reason clays make poor foundation soils. Footing loads bearing on clay are kept low, not so much because fear that the clay will be overstressed and therefore rupture, but because the footing loads will cause compression of the clay with the resulting settlement and undesirable cracking of the supported structure. Additives to treat deep strata of compressible soils are not now in use; there is, however, a very great need for such additives. While the low permeability of these compressible soils will make injection of additives difficult, materials which could fill the voids of the clay or alter its structure thereby reducing the compressibility are worthy of study. Reduction of Frost Susceptibility
Certain soils draw in water to form ice lenses and heave on freezing, Highly frost-susceptible soils can suck in great quantities of water, many times the amount already in the soil pores of even a saturated soil (Figure 7 ) . This figure shows a frozen sample of halloysite (4H20) which has expanded to a length 2.3 times ita initial length on freezing. While the volume change of soil on freezing can be detrimental to a pavement overlying the soil, the most serious problem arises when the ice melts in the spring. The great quantity of excess water in the soil from the melting ice can cause a significant loss in soil strength. Because of this frost action, many soils lose as much as 8.5 or 90% of their strength during the spring thaw. Frost considerations control the selection of fill material in many parts of northern United States. Otherwise acceptable granular materials must be wasted because they cannot meet the rigid frost susceptibility specification. The Arctic Construction and Frost Effects Laboratory, Corps of Engineers, Boston, Mass., has evaluated many chemicals as frost susceptibility modifiers by treating soils with them and then freezing samples of the treated soils. The most promising materials studied to date are the dispersants which, in small quantities, can effect a modest but important improvement in frost November 1955
At the present time, there is a need for chemicals to alter soi! properties in a wide variety of engineering problems; in fact, as this paper points out, there is a potential use for chemical additives which will alter almost any soil property. Because of changes in types of construction-e.g., heavier wheel loadsand economic conditions-e.g., the dwindling supply of granular materials-the need for soil stabilizers will become more critical. The permissible pricc? of soil additives varies from less than a cent a pound to over $5.00 a pound depending on the effective concentration of the additive and the job for which it is used. The most promising additives are those which are effective a t a treatment level of less than 1% of the dry soil weight and which cost less than 10 cents a pound. Because of the very diverse requirements of soil additives, there is no such thing as a single screening test. The best laboratory method of evaluation is to measure the effect of an additive on the particular soil property for which a change is desired. The prospects for soil stabilizers are very bright and the potential market for chemicals to be used as stabilizers is tremendous, but much research remains to be done. Research on the fundamental properties, especially the response of soil to various types of chemicals, can and should be conducted predominately by educational institutions; however, the producers of chemicals and soil handling equipment must do a great deal more applied research and development work in soil stabilization. The civil engineer, whose reticence to try new things is due in part to his having been oversold on new materials, must cooperate a great deal more with the research and development workers in the field of soil stabilization. Literature Cited
Ackley, C. S., U. S. Patent 2,232,898 (Feb. 25, 1941). Ibid., 2,235,695 (March 18, 1941). Barker, C. W., and Becker, A. A., “Impermeabiliaation of Soil3 by the Injection of Monomer Paira to Form Swelling Copolymers,” master of science thesis, Massachusetts Institute of Technology, May 1953. Christians, G W., U. S. Patent 1,763,219 (June 10, 1930). Ibid., 1,858,952 (May 17, 1932). Francois, A., U. S. Patent 1,430,306 (Sept. 26, 1922). Gnaedinger, John P., IKD. EKG.CHEY.,47, 2249 (1955). Irons, C. R. (to Dow Chemical Co.), U. S. Patent 2,298,129 (Oct. 6,1942). Irons, C. R., and Stoesser, S. M. (to Dow Chemical Co.), Can. Patent 386,475 (Jan. 23, 1940). Johnston, N. (assigned to Socony Vacuum Oil Co.), U. S. Patent 2,267,683 (Dec. 23, 1941). Lambe, T. W., “Chemical Injection Processes,” presented at annual meeting, American Society of Civil Engineers. New York, October 1954. Lambe, T. W., “Effect of Polymers on Soil Properties,” Proc. Third International Conference on Soil Mechanics and Foundation Engineering, Switaerland, August 1953. Lambe, T. W., J.Boston Society Civil Enganeers, 41 (April 1954). Lambe, T. W., and ilnderson, 0. E., T A P P I , 38, No. 1 (January 1955). Leeuwen, G. H. van, U. S. Patent 2,329,148 (Sept. 7, 1943) .
Mehner, N., Ibicl., 829,664 (Aug. 28, 1906). Miller. A. B. (assigned to Herculea Powder Co.). Ibid.. 2,323,. . 929 (July 13; 1943). I1/Iichaels. A. S., and Lambe, T. W., J. Ag. Food Chem., 1, 835 (1953).
Swan, J. C., U. S. Patent 1,379,657 (May 31, 1921). Zemlin, C., Ibid., 1,820,722 (Aug. 25, 1931). RECEIVED for review April 5 , 1955.
INDUSTRIAL AND ENGINEERING CHEMISTRY
ACCEPTED September 1 , 1965.
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