indicate a goal of 65 to 70% efficiency when applied on large outdoor reservoirs. These studies indicate a possibility of water savings on large reservoirs of $0.01 to $0.015 per 1000 gallons under favorable conditions. Literature Cited
Cheves, F.A., Dressler, R.G., McGavock, W.C., IND.ENG. CHEM.PROD. RES. DEVELOP.4, 206 (1965). Crawford, F.W., Stoops, C.E. (to Phillips Petroleum Co.), U.S. Patent 2,925,318 (Feb. 16, 1960). Dressler, R.G., Fifth Monthly Report, Southwest Co-operative Committee on Reservoir Evaporation Control, SWRI, San Antonio, Tex., March 31, 1956. Dressler, R.G., Ind. Eng. Chem. 56,36 (1964). Dressler, R.G., Johanson, A.G., Chem. Eng. Progr. 54, 66 (1958). Foulds, E.L., Jr., Dressler, R.G., IND.ENG. CHEM.PROD. RES. DEVELOP.7, 75(1968). Jones, G.K., unpublished master’s thesis, Trinity University, San Antonio, Tex., 1958.
LaMer, V.K., Aylmore, L.A.G., Proc. Natl. Acad. Sci. U . S . 48, 316 (1962). LaMer, V.K., Barnes, G.T., Proc. Natl. Acad. Sci. U . S . 45, 1274 (1959). Mihara, Y., National Institute of Agricultural Sciences, Tokyo, Japan, 1962; Symposium on Water Evaporation Control, Poona, India, 1962. Noe, E.R., Dressler, R.G., IND. ENG. CHEM.PROD. RES. DEVELOP. 4, 132 (1967). Reiser, C.O., Ind. Eng. Chem. Process Design. Develop. 8, 63 (1969). Rosano, H.L., LaMer, V.K., J. Phys. Chem. 60, 348 (1956). RECEIVED for review January 29, 1969 ACCEPTED July 30, 1969
From the master’s thesis of A. J. Simko, Department of Chemistry, Trinity University, San Antonio, Tex. Division of Water, Air, and Waste Chemistry, 155th Meeting, ACS, San Francisco, Calif., March, 1968.
EVALUATION OF SOME ACRYLIC POLYMERS AS SOIL STABILIZERS A.
A .
FUNGAROLI
AND
S .
R .
PRAGER
Department of Civil Engineering and Mechanics, Drexel Institute of Technology, Philadelphia, P a .
19104
A pilot experimental study of some acrylic polymers was undertaken. Their applicability as stabilizers of soil and soil-cement, with emphasis on economy, was determined. Selection of the test polymers was based on their suitability for in situ soil stabilization. Polymers currently used in four different industries were evaluated by compression and freeze-thaw tests. In all cases, polymerstabilized soil and soil-cement specimens outperformed their unmodified counterparts. A polymer used in the textile industry produced the greatest improvement. The relative economy of this polymer made it competitive with other stabilizing agents.
THEuse of additives t o modify a soil derives from the desire to improve its engineering properties economically. The most common use of modifiers is to improve the properties of large volumes of in situ soils a t relatively shallow depths in parking lots, highways, and airports. The most frequently used soil modifier is cement. When the optimum amount of cement is combined with a soil, a relatively low-cost material (soil-cement) is produced which has a high resistance to compressive loads. However, soil-cement has low resistance to mecbanisms such as periodic abrasion. T o minimize such phenomena, a cementstabilized soil is usually covered with a protective surface, such as bitumen. Over the years many other additives have been evaluated as soil stabilizers: calcium chloride, bitumen, lime, lignin, calcium acrylate, and other natural and synthetic resins (Lambe, 1953; Leonards, 1962; Prager, 1966). The commercial success of these modifiers has varied, with many having limited application due to high unit cost, handling difficulties, minimum soil property improve450
I & E C PRODUCT RESEARCH A N D DEVELOPMENT
ment, undesirable physical properties, or excessive set time. Recently, many polymers have proved economical in industrial applications. Polymers which produce cement concretes and cement mortars of relatively high tensile strength may be of particular interest for soil stabilization (Geist, 1963; Tyler and Drake, 1961). The purpose of the experimental study reported in this paper was a pilot evaluation of some of the newer polymers to ascertain their applicability as soil and soil-cement modifiers. The results presented are not intended t o represent the end product of a comprehensive study but rather the initial exploration of the potential use of recently developed polymers as economical soil-modifying agents. Material Selection
Polymers. I n today’s chemical industry many special polymers have been developed to meet particular demands. Prior to the selection of the test polymers for the study herein, criteria for the “ideal” soil stabilizer were
established because it was not possible or desirable to evaluate all those currently available. The criteria used for selection were: Water solubility before curing Water insolubility after curing Substantial improvement of tensile and compressive strength of cement mortars Low viscosity for ease of mixing and handling Nontoxicity Suitability for curing under typical field conditions Insensitivity to temperature changes Complete compatibility with various soils and with portland cement The polymers selected for study were all obtained from the Rohm and Haas Co., Philadelphia, Pa. They were all acrylic polymers and had the trade names Rhoplex AK-240, Rhoplex B-BOA, Rhoplex HA-8, and Rhoplex MC-4530. Chemical cclmpositions are not available. Soil. The soil used was the low plasticity soil of the ACIL Standard Soils Program (U. S. Corps of Engineers, 1966). I t had a liquid limit of 28% and a plastic limit of 24%. I n the AASHO classification system this soil was in class A-4 and had a group index of 8. The estimated quantity of cement required for optimum stabilization of an A-4 soil, recommended by the Portland Cement Association, was 10% by weight (Portland Cement Association, 1959). This estimated quantity of cement was used in this study. Cement. Type I portland cement was used. Defoaming Agent. Polymers tend to foam when mixed, and a defoaming agent is used to eliminate this problem. I n soils this is especially critical, because foaming action would greatly reduce compacted densities. Kopco NXZ, obtained from the Ncipco Chemical Co., Newark, K. J., was used as the defoaming agent.
Table 1. Harvard Compaction Test Data
Description
Quantity
Kumber of layers Number of tamps per layer Spring force, pounds Maximum dry density, p.c.f. Optimum moisture content, C/c
5 25 20 106.0
16.8
Table II. Solid Constituents of Test Specimens
Specimen Series
Soil, '%'
A
100 90 98 88
B C
D
ComDonmLs Cement, 5%
Polymer, 7;
a
...
...
10
...
10
2 2
...
R of total weight.
Testing Procedure. The compression test was performed at an axial strain rate of 0.05 inch per minute with failure load recorded to the nearest pound. The freeze-thaw tests were carried out in a variable temperature environmental room. The testing procedure was a modified form of the ASTM freezing and thawing test of compacted soil-cement mixtures (D 560-57). Each specimen underwent 12 cycles with each test cycle lasting 24 hours, 16 hours a t -10°F. and 8 hours a t 78°F. At the end of the thaw portion of the cycle each specimen surface was brushed twice with a hard bristle brush. Freeze-thaw specimens were tested at 7, 67, and 91 days, and compression test specimens were tested a t 7 and 91 days. The results presented are the average of three compression and two freeze-thaw specimens in each group.
Test Program
Two physical tests were performed: the unconfined compression test and a modified freeze-thaw test. These were considered the rnost significant for delineating the influence of the polymers on the modified soil's properties. Sample Preparation. Cylindrical test specimens were prepared in a Harvard compaction mold, 15%6 inches in diameter and 2.816 inches in height. Pertinent soil compaction data are listed in Table I. All test specimens were prepared in the same manner. A specimen was accepted if its moisture content was within i l percentage point of optimum moisture content and if its wet density was within =t3 pounds per cubic foot of maximum wet density. The test specimen series are listed in Table 11. The defoaming agent was used in all the polymermodified soil specimens, and was 1.5% by weight of the polymer solids. The soil and cement were first dry-mixed. Then the water, polymer, and defoamer were added to obtain the desired specimen mixture. After mixing, the blend was compacted in the H a i ~ a r dmold. The top of each layer of soil was scarified during compaction to ensure a well bonded specimen. Curing Procedure. Prior t o testing, specimens were aircured in a controlled environmental room a t 70°F. and 70L relative humidit:y. While soil-cement is field-cured under saturated conclitions, a comparison of air-cured specimens was deemed most desirable because such field practice could substantially reduce placement costs.
....D
7day Slday
1 385
I
...
2. specimen serieq refer to definitions given in Table 11
41 I !
HA8 B60A
J79
~
HA8
AK 240
I
I
I
I
I
I
I
1
I
I I
mc 4 9 0
0
100
516
200 300 400 500 Failure Stress (psi)
I
I
600
700
I
Figure 1. Results of compression tests VOL. 8 N O , 4 DECEMBER 1 9 6 9
451
-
D) were more resistant to the freeze-thaw cycles than the unmodified soil-cement (series B) for all cure times. The HA-8 polymer-modified soil-cement specimen was more resistant than any of the other polymer-modified specimens and from three to five times more resistant than the unmodified soil-cement specimen.
/ / / A / / / A / / / , 43%
-
22
Unit Cost Analysis
To include relative economy in the final analysis, a unit cost computation was performed for specimen series B and D, using the average retail price of type I portland cement and the manufacturer's quoted bulk quantity prices for the polymers. This information, along with the cost per cubic yard of each mixture, is presented in Table
HA8 B60A
NOTES: 1.Cure Time e71 lday. 61day.. mZa Blday
.... ...
111. Gain-Cost Factor. Gain-cost factors were computed for
2. Specimen series refer to definition given in Table
If
each polymer-modified soil-cement a t each curing time. The gain-cost factor was defined as:
GCF
0
II/IC
where GCF is the gain-cost factor, I1 is the improvement of a physical property of the polymer-soil-cement mixture over the soil-cement mixture both tested at the end of the same curing time, and IC is the additional cost of the polymer-soil-cement due to the addition of the polymer to the soil-cement mixture. The results given in Table IV show clearly that all the polymers (series D) produced economically substantial improvement over the unmodified soil-cement specimens. The improvement with HA-8 was considerably superior to that of the other polymers.
10
5
=
Wt. Loss at End of Test (percentagepoints)
Figure 2. Results of freeze-thaw tests
Test Results
Figure 1 shows the compressive test results for the polymer-modified specimens of soil and soil-cement and the specimens of unmodified soil and soil-cement. The polymer-modified specimens (series C and D)were more resistant to compressive loads than the plain soil specimen (series A) and the soil-cement specimen (series B). The specimen containing HA-8 had a compressive strength more than twice that of the plain soil-cement specimen a t the 91-day test. The HA-8 modified specimen was also stronger than any of the other polymer-modified soils. I t is noteworthy that the soil modified with HA-8 alone (series C) was stronger than the unmodified soilcement specimen (series B) . Results of the freeze-thaw test are shown in Figure 2 for the polymer-modified specimens of soil and soilcement and the specimens of unmodified soil and soilcement. The polymer-modified specimens (series C and
Conclusions
Some of the newer polymers have the potential for improving stabilized soils a t relatively low cost. Polymer HA-8 produced stabilized soils (series C and D) superior to the plain soil-cement specimens in both compressive strength and resistance to freeze-thaw cycles. The exploratory nature of the experimental program and its limited scope prohibit specific recommendations as to the general applicability of the newer polymers to soil stabilization. Many other contributing factors, such as bulk quantity costs, bulk placement problems, and long-term stability, could distort, if not destroy, the favorable picture presented. However, it is believed that the results show that polymer technology has reached a level where polymers could be developed which would
Table 111. Cost Computation for Stabilized Mixtures for Specimen Series B and D
Components Solids Soil Cement Polymer B-60A HA-8 AK-240 MC-4530 Liquids Water Defoamer Air Totals
452
Specific Gravity
wt.,g.
ComDonent Quantities Laboratory Preparation: Cu. Yard wt. % VOl. % Vol. 5
...
...
...
...
2.65 3.15 1.05
675.0 75.0 15.0
75.0 8.3 1.7
59.5 5.6 3.3
... ... ... ...
... ... ... ...
1.oo
135.0
... ...
...
...
... ...
15.0
31.6
26.4
...
...
... ...
900.0
100.0
100.0
~
... ... ...
... ... ...
... ...
... ...
...
0.90
57.4
I & E C PRODUCT RESEARCH A N D DEVELOPMENT
...
...
Wt.; lb. 2523 2225 249 49
...
cost, Yard
$1 Cu.
...
...
...
...
... ...
... ...
... ...
0.1600 0.1475 0.2750 0.1475
7.82 7.21 13.45 7.21
445
...
...
...
16.2
... ...
100.0
5491
...
Unit Price, $iLb.
... ...
... ...
produce desirable soil properties a t a very competitive cost.
Table IV. Gain-Cost Factor for Polymer Stabilization for Specimen Series D
Fnceze-Thaw
Polymer
Imp rouement, points
B-60A HA-8 AK-240 MC-4530
13.5 20.3 16.3 16.5
Literature Cited
Geist, J. M., Amagna, S. V., Memmor, B. R., I n d . E n g . Chem. 45, 759-67 (1963). Lambe, T. W., “Stabilization of Soils with Calcium Acrylate,” Contributions to Soil Mechanics, 1941-1953, Boston Society of Civil Engineers, Boston, Mass., pp. 257-84, 1953. Leonards, G. A., “Foundation Engineering,” pp. 351-437, McGraw-Hill, New York, 1962. Portland Cement Association, Chicago, Ill., “Soil-Cement Laboratory Handbook,” 1959. Prager, S.R., Drexel Tech. J. 28, 6 (May 1966). Tyler, 0. Z., Drake, R. S.,Adhesives A g e 4, 30-8 (September 1961). U. S. Corps of Engineers, “Statistical Analysis of Data from a Comparative Laboratory Test Program,” Misc. Paper 4-785, 759-67 (January 1966).
Compress ion Test Improue-
Gain-cust factor
ment, p.s.i.
Gain-cost factor
91 200 113 91
6.8 35.0 14.1 7.1
...
...
...
...
7-Day Cure 1.98 2.82 1.2 2.2 67-Day Cure B-60A HA-8 AK-240 MC-4530
14.6 19.4 15.6 14.8
B-60A HA-8 AK-240 MC-4530
15.2 17.9 14.4 17.2
1.87 2.69 1.16 2.05
... ...
... ...
194 405 255 131
24.8 56.2 19.3 18.2
91-Day Cure 1.94 2.48 1.07 2.39
RECEIVED for review January 13, 1969 ACCEPTED August 1, 1969 A portion of this study was performed under SSF Undergraduate Research Grant No. GY-202.
OXIDATION OF ASPHALT FILMS MEASURED BY LIGHT SCATTERING B E T T Y
A.
BEHL’,
FRANK
H.
SCRIVNER,
AND
Highway Research Center, Texas A & M University, College Station, T e x .
RALPH
N.
T R A X L E R
77843
The! extent of oxidation of an asphalt during service is an important factor in changing its rheological and mechanical properties. One of the better evaluation methods has been to oxidize asphalt films in a dark oven and determine the increase in viscosity (megapoises) at 25’ C. in the material. A sliding-plate, thin-film viscometer is used. A procedure for forming thin films of asphalt by a rnoving slide impactor and oxidizing them by exposure to ozone for a few minutes is described. The light-scattering by the oxidized film is measured by a dlark-field microscope provided w i t h special optics and a photocell attachment. The light-scattering technique is a reliable measure of the susceptibility of an asphalt to oxidation. There i s a well defined relationship between the datg from the oven test and those obtained by the light scattering method.
ASPHALT is used mai:nly as an adhesive or waterproofing agent. The extent of oxidation occurring during service is important because of its connection with the degree of change in the rheological and mechanical properties of the asphalt. Previous Work
A number of procedures have been developed to estimate the effect of time, heat, and oxygen on asphalt films Present address, School of Medicine, University of Southern California, Pulmonary Function Research Laboratory, 2025 Zonal Ave., Los Angeles, Calif. 90033
of different thicknesses. One procedure has been used extensively (Lewis and Welborn, 1941). A layer of asphalt YS inch thick is placed in a 5%-inch-diameter aluminum pan and heated in a dark, air oven for 5 hours at 162.8”C. Standard asphalt tests (penetration, softening point, and ductility) are made on the original and hardened asphalts and the results compared. A new technique developed later (Griffin et al., 1955) evaluated the increase in viscosity a t 25°C. caused by heating 5-micron films of asphalt in a dark, air oven for 2 hours at 107.2”C. This method was modified (Traxler, 1961) by using 15-micron films to expedite preparation of the sample and determination of the viscosity value. VOL. 8 NO. 4 DECEMBER 1 9 6 9
453
