Method of upgrading rock and treated rock obtained therefrom

A method is provided for upgrading rock in the form of aggregate, block, shaped stone or concrete structures involving the treatment of such rock with a dilute aqueous solution of polyelectrolyte. Enhanced degradation resistance is achieved by further wetting the polyelectrolyte treated rock with a multi-valent ion metallic salt solution. Treated aggregate, portland cement and bituminous concrete compositions containing such treated aggregate are also provided.

BACKGROUND OF THE INVENTION 
Prior to the present invention, various methods were evaluated for treating 
rock to render the rock more resistant to environmental degradation. There 
have been many studies and methods of improving the quality of building 
stone and monuments, and limited study has been devoted to coarse 
aggregate quality improvement. 
One study directed to aggregate improvement is shown by the interim report 
of May 1977, revised and updated January 1978, report PTI 7707 of the 
Pennsylvania Transportation Institute of Pennsylvania State University of 
P. V. Cady, "Upgrading of Poor or Marginal Aggregates for PCC and 
Bituminous Pavements". Various organic materials were evaluated as 
treating agents for improving the resistance of aggregate to degradation. 
Although valuable information has been generated from the aforementioned 
study, a satisfactory solution to the problem of aggregate degradation 
resulting from exposure to adverse environmental conditions including air 
pollution, moisture, or inorganic salt contact has not been found. 
Improvement has been noted by using organic materials, such as epoxy 
resins, methyl methacrylate, etc., to treat marginal aggregate, but the 
degree of aggregate upgrading achieved has not warranted the cost of using 
such material unless the organics were extensively diluted in polluting 
organic solvents. 
Standard engineering tests can be performed to predict the quality of 
aggregate. One procedure, for example, has been the magnesium or sodium 
sulfate soundness test, ASTM C88-76. In many instances, local high quality 
course aggregate is not available for building construction and must be 
obtained at a high transportation cost. Various procedures have been used 
in an attempt to improve the quality of marginal or submarginal rock, for 
example, argillaceous limestone, highly crystalline limestone and 
graywacke sandstone to upgrade such material for use in portland cement or 
bituminous concrete. Procedures of the prior art have been found to be 
unacceptable because of economic or environmental reasons, or the treated 
rock failed to survive the magnesium or sodium sulfate soundness test. 
Improved results have been achieved as shown by U.S. Pat. No. 4,256,501 of 
George M. Banino, based on the use of an organic solvent mixture of an 
organic condensation polymer and an aliphatic polyamine. However, organic 
solvent can present environmental pollution problems. In addition, the 
aforementioned aryl condensation polymer, for example, 
silicone-polycarbonate block polymers can significantly increase the cost 
of such treatment due to the expense of the starting reactants. 
The present invention is based on the discovery that polyelectrolytes, 
i.e., polymeric substances in which the monomeric units of its constituent 
macro-molecules possess ionizable groups, for example, 
polyethylenepolyamine, can be employed in the form of an aqueous solution 
to treat rock, stone or aggregate in the substantial absence of any 
unhardened cement, or material with adhesive and cohesive properties which 
make it capable of binding mineral fragments into a compact whole. As 
shown by AM Neville, Properties of Concrete, on pages 1-102, Wiley Sons, 
New York, 1973, the term cement includes hydraulic cement. The degradation 
resistance of the treated rock has been found to be dramatically improved, 
particularly if the polyelectrolyte treated rock is further wetted with 
certain metallic salt solvent solutions. It has been found that treatment 
of the rock, stone, or aggregate in accordance with the practice of the 
invention can be accomplished in an economic and non-polluting manner. 
STATEMENT OF THE INVENTION 
Although the reason why dramatic upgrading of aggregate, or the improvement 
in degradation resistance of free standing stone or concrete structures to 
adverse environmental conditions is achieved by the method of the present 
invention is not completely understood, one possible explanation is that 
the polyelectrolyte in the substantial absence of unhardened cement forms 
a membrane or semipermeable barrier on either the rock surface, or if the 
rock is porous, the rock interior. The membrane may act as a barrier to 
deleterious elements responsible for rock degradation, while at the same 
time allow for the transport of water. 
There is provided by the present invention, a method for upgrading rock 
having an average diameter of at least 1/4" in the substantial absence of 
unhardened cement which comprises, 
(1) wetting the rock with an aqueous polyelectrolyte solution having at 
least 1% by weight of polyelectrolyte, and 
(2) allowing or effecting the drying of the polyelectrolyte treated rock. 
Another aspect of the present invention, is directed to a method for 
further treating the polyelectrolyte upgraded aggregate with a gellation 
agent to further improve aggregate performance with respect to 
environmental degradation which comprises 
(1) contacting aggregate which has been treated with polyelectrolyte in the 
substantial absence of unhardened cement, with a gellation agent in the 
form of an aqueous solution of a multivalent metallic salt, 
(2) allowing or effecting the drying of the resulting treated aggregate. 
Additional aspects of the present invention relate to polyelectrolyte 
treated aggregate, polyelectrolyte treated metallic salt gellation agent 
and reinforced portland cement compositions containing such treated 
aggregate. 
Included by the term "polyelectrolyte" as used in the practice of the 
present invention, is any water soluble ionic polymer in the form of 
either polyacid, polybase, or polyampholite, depending upon the nature of 
its ionization in water solution. A more comprehensive definition of the 
term polyelectrolyte can be found in the Encyclopedia of Polymer Science 
and Technology, Vol. 10, pp. 781-861 (1969) John Wiley & Sons, New York. 
The preferred polyelectrolytes are polyethyleneimine or polyalkylene 
polyamine, manufactured by the Dow Chemical Company, Midland, Mich., 
having a molecular weight in the range of from about 200 to about 1000. 
Some of these preferred polyelectrolytes are anhydrous polyalkylene 
polyamine polymers (XD-3259.01) of the Dow Chemical Company, having the 
following characteristics: sp 
______________________________________ 
Property XD-30259.01 
______________________________________ 
Formula H.sub.2 N(C.sub.2 H.sub.4 NH).sub.n H 
Molecular weight Approx. 250-300 
Boiling Range, .degree.C. 
&gt;250.degree. C. at 760 mm. Hg 
Freezing Point, .degree.C. 
Below 40.sup.1 
Specific Gravity, 25/25.degree. C. 
1.02 
Pounds per Gallon, 25.degree. C. 
8.46 
Flash Point, .degree.F. 
425 Cleveland open Cup 
Approximate Solubility grams per 
100 grams solvent at 25.degree. C. 
Acetone 
Benzene 
Carbon Tetrachloride 
Reacts Violently 
EthylEther 
n-Heptane &lt;0.1 
Methanol 
Water 
______________________________________ 
.sup.1 Pour Point 
Some of the following Quarternized polyalkylene polyamines XD-30267, 
XD-30268, XD-30269 and XD-30269.01 are also included. 
__________________________________________________________________________ 
Property XD-30267 
XD-30268 
XD-30269 
XD-30269.01 
__________________________________________________________________________ 
% of Quaternization 
10 25 50 75 
Mol. Wt. 40-80,000 
40-80,000 
40-80,000 
40-80,000 
pH, 25.degree. C. 
9 8 8 8 
% Solids, Active 
35 35 35 35 
% Solids, Non-volatile 
50.4 50.3 51.2 49.6 
Viscosity, cps, Brookfield 
1502 478 167 55 
RTV #3 Spindle at 100 RPM 
#3 Spindle at 50 RPM 
Specific Gravity, 25/25.degree. C. 
1.152 1.161 1.163 1.164 
Pounds per gallon, 25.degree. C. 
9.6 9.67 9.7 9.7 
__________________________________________________________________________ 
Polyvalent metallic salts which can be used as gellation agents for 
polyelectrolyte treated aggregate in accordance with the practice of the 
present invention are salts of Group IIA, IIIA and IVA metals having 
anions selected from halides, acetates, sulfates, chromates, phosphates, 
etc. In order to determine whether a polyvalent metallic salt can perform 
effectively as a gellation agent, a dilute aqueous solution of the 
metallic salt, for example, a 10% solution can be added with stirring to a 
dilute aqueous solution of the polyelectrolyte. Gellation or precipitation 
of polyelectrolyte product indicates the polyvalent metallic salt is an 
effective gellation agent. 
The term "rock" as employed in the description of the method of the present 
invention is intended to include stone, aggregate, block, concrete, having 
a diameter of at least 1/4" as well as existing stone structures, etc. 
More particularly, rock refers to those rocks containing 50% or more of 
siliceous minerals and those rocks containing 50% or more of carbonate 
minerals. Silicious rock is represented, for example, by dark gray, 
fine-grained graywacke sandstone with interbedded black shale layers and 
beds. Carbonate rocks are represented, for example, by medium crystalline 
metamorphic dolomitic marble; medium to dark gray, fine grained dolomite 
to argillaceous dolomite with interbedded black shale partings; and an 
inter-reef deposit of nearby black, fine grained, argillaceous dolomite to 
shalely dolomite. In addition to these aggregate rock, those skilled in 
the art also would know that surface treatment of existing stone 
structures, for example, monuments, road surfaces, bridges, buildings, 
etc., having existing shaped stone surfaces also can be benefited and are 
included with the scope of the present invention. Existing bridge surfaces 
can be initially treated with the above described polyelectrolyte followed 
by a post treatment with the above described polyvalent metallic salt 
gellation agent. An example of building stone is a fine grained graywacke 
sandstone which can be medium to dark gray to greenish gray.

More particularly, in FIG. 1, there is shown an inclined spiral screw 
assembly extending into a well at 10. Aggregate feed is fed into the well 
at 10 and aqueous polyelectrolyte, or "treating solution", is fed into the 
same location from a reservoir at 11 to produce an aggregate bed immersed 
in treating solution. The spiral screw is thereinafter rotated to convey 
the aggregate up an incline to a discharge point at 12 and the treated 
aggregate is then conveyed to a collection point not shown and allowed to 
dry under atmospheric conditions. Total treating time, that is time in 
which the aggregate is fed into the treating solution until it is 
discharged, can vary from 15 seconds to 90 seconds. 
FIG. 2 shows a slightly inclined screen deck at 20 and a vibrator at 21 to 
allow for the forward movement of aggregate which is fed from the upper 
section of the deck and which is allowed to pass under a spray bar at 22 
and then discharged at the end of the screen deck into a collection bin 
not shown. The treating solution is then collected at the end of the 
screen deck and recycled to the holding tank. It has been found that the 
total time for treating the aggregate on the screen deck can vary between 
about 15 seconds to 30 seconds before it is discharged. 
Another variation of aggregate treatment is shown in FIG. 3 utilizing a 
bucket elevator 28 which is passed through an aggregate bed at 30 which is 
immersed in treating solution. The treated aggregate is discharged at the 
top of the elevator at 31. The total aggregate treating time through 
treating bed averages about 15 seconds to 1 minute. 
A further variation of treating aggregate in accordance with the practice 
of the present invention is shown in FIG. 4 showing the immersion of 
aggregate on a moving conveyer belt through a holding tank 42 containing 
treating solution. The average treating time in and out of the bath can 
vary between 15 seconds to one minute depending on various factors such as 
speed of the conveyer belt, the concentration of the treating solution, 
etc. 
In the practice of the invention, aggregate can be fed into the treating 
solution and the treated aggregate can thereafter be allowed to dry. As 
previously indicated, the time for treating the aggregate can vary widely 
for effective results. Experience has shown that a solids concentration of 
between about 2 to 25% by weight of polyelectrolyte based on total weight 
of solution will provide effective results in the treating bath. Higher or 
lower concentrations can also be utilized, however, those skilled in the 
art would know that longer contact time can be required, or waste of 
polyelectrolyte might readily result rendering the procedures uneconomic. 
In particular instances, forced air can be used to effect the drying of the 
treated rock. 
Further treatment of the polyelectrolyte treated aggregate made by 
procedures described above as, for example, by FIGS. 1-4, can be achieved 
by subsequent use of a gellation agent in a bath in place of the 
polyelectrolyte. 
The test method used to evaluate rock treated in accordance with the 
practice of the present invention is the sulfate soundness test. More 
specifically, the rock was tested in accordance with New York State 
Department of Transportation "Soundness of Course Aggregates by Magnesium 
Sulfate Solutions", test method New York 207 B-76. This test is based on 
the ASTM soundness of aggregates by use of sodium sulfate or magnesium 
sulfate test method C88-76. The New York State test method maintains a 
solution temperature of 74.degree. plus or minus 1.degree. F. Another 
significant distinction between the two test methods is that the New York 
State test method is based on a 10 cycle test while the ASTM test is run 
on a 5 cycle test. 
The term aggregate as utilized in the practice of the present invention 
includes crushed stone and gravel and can vary in size from approximately 
1/4" to 4" in diameter. Preferably, the average diameter of the aggregate 
is 1/4" to 11/2". It is preferred to utilize aggregate in the practice of 
the present invention in the substantial absence of unhardened cement, or 
any material falling outside of the aforedescribed aggregate definition 
which would interfere or compete with the surface treatment of the 
aggregate by the polyelectrolyte. 
Aggregate utilized in the test method for evaluation is initially screened 
to separate out the fraction passing a 1/2 inch screen and retained on a 
1/4 inch screen. The sized aggregate is then washed to remove any dust or 
coatings. The washed aggregate is then dried in an oven to constant weight 
at a temperature of 230.degree. F. plus or minus 90.degree. F. The dried 
sample is then weighed to obtain a 2500 gram plus or minus 50 gram charge. 
The dried aggregate is then placed into a wire mesh basket and immersed 
into the treating solution for about 30 seconds to 1 minute and agitated 
slightly to displace any air pockets. The basket is then removed from the 
solution of the composition and allowed to set for several minutes until 
little or no solution runoff is observed. The treated sample is then dried 
in an oven at a temperature of 230.degree. F. plus or minus 9.degree. F. 
to a constant weight. 
The treated sample is then tested for its ability to resist environmental 
degradation by immersing it while in a wire basket into a magnesium 
sulfate solution for 16-18 hours. After immersion, the sample is removed 
and allowed to drain for about 15 minutes and then placed into a drying 
oven which is at a temperature of 230.degree. F. plus or minus 9.degree. 
F. The sample is then dried to 61/2 hours, completing one cycle. The 
process of alternate immersion and drying was repeated for 10 full cycles. 
After completing the final cycle, the sample is washed free of any 
magnesium sulfate and then dried to a constant weight of a drying oven at 
a temperature of 290.degree. F. plus or minus 9.degree. F. The dried 
aggregate is then resieved over 1/4 inch sieve and the weight recorded. 
The difference between the final weight and the original weight represents 
the loss due to "D" or "degradation". The %D is expressed as a percentage 
of the original weight. 
In instances where blocks of stone are tested, a modification of the 
above-described aggregate test procedure is employed. Approximately 
cubical shaped blocks ranging from about 11/2 inch to 3 inches on a side 
are separated from larger blocks either by sawing or by breaking the stone 
with a hammer and chisel. The blocks are then either soaked in the test 
solution for up to one minute, or coated with the solution using a paint 
brush. The blocks are then placed in an oven at a temperature of 
230.degree. F. plus or minus 9.degree. F. to constant weight. The 
temperature of 230.degree. F. plus or minus 9.degree. F. to constant 
weight. The prepared samples are then subjected to alternate immersion and 
drying for 10 cycles in the same manner as described above for the 
aggregate. Upon completion of the final cycle, the blocks are then washed 
free of magnesium sulfate and the %D is observed quantitatively in terms 
of percent weight loss based on the original weight of sample. 
In order that those skilled in the art will be better able to practice the 
invention, the following examples are given by way of illustration and not 
by way of limitation. All parts are by weight. 
EXAMPLE 1 
Marble and limestone aggregate were classified to size in accordance with 
the previously described procedure. Aqueous solutions of polyethyleneimine 
(PEI-6) having a molecular weight of about 300, manufactured by the Dow 
Chemical Company were also prepared. The concentration of PEI in water 
(g/dl) had a value between 0.3 and 1.0. A solution of 3 g/dl of PEI-6 in 
acetone was also prepared. 
The aggregate was then treated with PEI-6 by placing it in a wire basket 
dipping it into the aqueous PEI solution and allowing it to dry. The 
treated aggregate was then tested for its ability to resist environmental 
degradation in accordance with the Sulfate Soundness test as described 
above. The following results were obtained, where "conc" is concentration, 
(g/dl) of PEI-6, "L" under Rock is limestone and "M" under rock is marble 
and %D is the percent weight loss of aggregate experienced after the 
magnesium sulfate treatment is compared to the original weight of the 
aggregate: 
TABLE I 
______________________________________ 
Solvent Conc Rock % D 
______________________________________ 
Water 0 L 72.0 
Water 0 M 36.8 
Acetone 3 L 13.87-19.8 
Water 3 L 5.48 
Water 1.0 M 9.49 
______________________________________ 
The above results show that treatment of the aggregate with 
polyethyleneimine (PEI-6) considerably enhanced the degradation resistance 
of the aggregate. A significant variation is shown in limestone aggregate 
reflecting the variation in the rock being tested. 
EXAMPLE 2 
The procedure of Example 1 was repeated except that argillaceous dolomite 
aggregate was evaluated. There was utilized a 5% aqueous polyethyleneimine 
solution and the treated aggregate was air dried. It was found that the 
percent degradation was 10.2% for the treated aggregate, and 14.2% for the 
untreated using a sodium sulfate solution. 
EXAMPLE 3 
Graywacke sandstone (B) and argillaceous dolomite aggregate (D) were 
evaluated for degradation resistance after being treated with various 
polyelectrolytes. In addition to PEI-6 as utilized in the previous 
examples, there were also employed as polyelectrolytes, PEI XD 30259.01, 
PEI XD 30269.01, polyacrylic acid (PAA) and Jeffamine T-403, a 
tris-2-aminopropylether of triol, manufactured by the Jefferson Chemical 
Company. The following results were obtained: 
TABLE II 
______________________________________ 
conc 
Polyelectrolyte 
(g/dl) Rock %D 
______________________________________ 
PEI-6 0 D 26.1 
PEI-6 1.0 D 4.1 
PEI XD 30259.01 
.5 D 4.2 
PEI XD 30269.01 
.5 D 18 
Jefumine T.403 
.5 D 16.2 
PAA 300K 1.0 D 25.2 
PAA 50K .5 D 25.9 
PAA 50K 0 B 79.5 
Polymin 6 1.0 B 17.1 
PEI XD 30259.01 
.5 B 4.3 
PEI XD 30269.01 
.5 B 53.6 
Jefumine T-403 
.5 B 64.1 
PAA 300K 1.0 B 72.4 
PAA 50K .5 B 74.7 
PAA 300K .3 B 79.4 
PAA 50K .3 B 79.5 
______________________________________ 
The above results show that the polyethyleneimine polyelectrolytes 
significantly enhanced the degradation resistance of the dolomitic and 
bath stone aggregate, while the polyacrylic acid and Jefumine T-403 impart 
some degree of improvement over the untreated aggregate. 
EXAMPLE 4. 
Additional argillaceous dolomite aggregate and bath stone aggregate were 
evaluated utilizing polyethyleneimines PEI-6, polymin 6, PEI-XD-30259.01 
and XD-30269.01 of Example 3. Aqueous solutions were prepared having a 
range of from 0 part to 10 parts of the polyelectrolyte per 100 parts of 
water. Treatment of the aggregate was in accordance with the procedure 
outlined for New York test method 207B-70. The following results were 
obtained, where D and B are as defined in Example 3: 
TABLE III 
______________________________________ 
Polyelectrolyte 
Conc Rock % D 
______________________________________ 
0 D 31.1 
PEI 6 .1 D 30.5 
PEI 6 .3 D 15.7 
PEI 6 .5 D 10.7 
Polymin 6 1.0 D 4.1 
PEI-XD-30259.01 
.3 D 8.2 
PEI-XD-30259.01 
1.0 D 4.1 
PEI-XD-30269.01 
.3 D 16.7 
PEI-XD-30269.01 
1.0 D 4.2 
PEI-XD-30269.01 
0 B 71.8 
Polymin 6 1.0 B 17.1 
PEI-XD-30259.01 
.3 B 31.2 
PEI-XD-30259.01 
1.0 B 1.3 
PEI-XD-30269.01 
.3 B 55.6 
PEI-XD-30269.01 
1.0 B 27.6 
______________________________________ 
The above results further establish that the polyethyleneimine 
polyelectrolyte and modifications thereof provide superior environmental 
degradation resistance when tested in accordance with the New York State 
10 cycle magnesium sulfate test. 
In accordance with the procedure shown in FIG. 1, dolomitic aggregate is 
conveyed into a 5% solution of a polyethyleneimine described above. The 
aggregate is passed through a 5% by weight solution of a polyethyleneimine 
up the ramp by means of the revolving screw and the treated aggregate is 
discharged at the terminal point within 90 seconds. The treated aggregate 
is then allowed to collect into a hopper which is blown dry with heated 
air. There is obtained aggregate treated in accordance with the practice 
of the present invention. The treated aggregate is then blended with sand 
and portland cement to produce concrete having approximately 45% by weight 
of coarse aggregate treated in accordance with the present invention. 
Additional concrete compositions also can be made utilizing the treated 
aggregate having from 60% by weight to 90% by weight of the treated 
aggregate. Further examples of cement and concrete mixtures which can be 
used in combination with treated aggregate of the present invention are 
shown in the Encyclopedia of chemical Technology (1979) Vol. 5, pages 
163-191, John Wiley and Sons, New York. 
EXAMPLE 5 
Several polyvalent metallic salts were evaluated as possible candidates as 
polyelectrolyte gellation agents. Aqueous solutions of the respective 
salts at concentrations of 10% by weight were added with stirring to 
aqueous solutions of polyelectrolyte having a concentration of 10% by 
weight of polyelectrolyte. The following table shows the results obtained, 
where "Y" indicates gellation or precipitation, and "N" indicates no 
gellation: 
TABLE IV 
______________________________________ 
Tetramine** 
Polyacrylic 
Salt PEI* T-403 acid 
______________________________________ 
MgSO.sub.4 
Y Y Y 
Mg Acetate 
Y Y Y 
MgCl Y Y Y 
MgCO.sub.3 
N -- -- 
Na.sub.2 SO.sub.4 
N N N 
Na.sub.2 CO.sub.3 
N N N 
CaSO.sub.4 
N Y Y 
Al.sub.2 (SO.sub.4).sub.3 
Y Y Y 
FeCl.sub.3 
Y Y N 
FeSO.sub.4 
Y Y N 
CdSO.sub.4 
Y Y Y 
CoSO.sub.4 
Y Y Y 
CrSO.sub.4 
Y Y Y 
CuSO.sub.4 
N Y Y 
PbCrO.sub.4 
Y Y Y 
SnSO.sub.4 
Y Y -- 
______________________________________ 
*Imine (CH.sub.2 --CH.sub.2 --N).sub.n 
**Polyoxypropylamine 
A testing apparatus for evaluating the effect of polyvalent metallic salt 
gellation is shown by FIG. 5. A glass tube is shown at 50, a 60 mil 
thickness rock slab is shown at 53 and the testing solution interface is 
shown at 52. 
Slabs of graywacke sandstone were attached to glass tubes utilizing an 
epoxy resin adhesive. The sandstone slabs were exposed for 1-2 minutes 
with various liquids including distilled water, an aqueous 10% by weight 
of PEI-6 solution and a saturated magnesium sulfate solution. In addition, 
a sandstone slab was initially treated with the aqueous PEI-6 solution 
followed by treatment with the saturated magnesium sulfate solution. 
The degradation resistance of the treated slabs were tested by measuring 
the average loss of testing liquid through the slabs under pressure of 20 
psi. The testing liquids included distilled water, a saturated magnesium 
sulfate solution is distilled water and a 10% sodium chloride solution in 
distilled water. After 1 week, two effects were noted in certain cases. 
The back surfaces at 54 of the slabs were altered in terms of color and 
texture. In addition, extremely fine cracks were observed at a 
magnification of 10x. In those slabs which were altered after one week, 
there also was found an inorganic deposit on the back surface and a 
physical disintegration after several additional weeks. The loss of liquid 
was found to be approximately 0.5 cc per day. 
Surprisingly, the slabs treated with magnesium sulfate behaved in a 
completely different manner. The magnesium sulfate treated slab was found 
to be impervious to water after a three month period. However, the 
MgSO.sub.4 treated slab underwent a progressive change of appearance 
within four days as a result of exposure to aqueous NaCl and ultimately 
deteriorated. In contrast, the slab treated with both PEI and MgSO.sub.4 
had not undergone any loss of liquid or any change in physical 
characteristics as a result of exposure to distilled water, saturated 
MgSO.sub.4 solution or 10% aqueous NaCl. 
With further reference to FIG. 5, a further evaluation of various rock 
slabs were made to determine the effectiveness of the slabs as anionic 
exchange membranes. The rock slab surfaces at 52 were evaluated without 
treatment, treated with polyelectrolyte, or subsequently treated with 
polyelectrolyte and magnesium sulfate as described above. Sodium chloride 
testing solutions varying in concentrations between 0.01 mole to 0.1 mole 
were utilized at 51. Each of the slabs were further immersed in sodium 
chloride solutions varying in concentrations between 0.01 mole to 0.1 
mole. Electrodes were placed in the salt solution inside the tube at 51 
and in the sodium chloride in which the slab was immersed. The electrodes 
were joined to a Leeds and Northrop Research ph Meter, model #7416. 
Sandstone (S), marble (M) and dolomite (D) were evaluated as membranes. 
The following electrochemical potential data are shown in Table V, where 
the numbers shown are millivolt values for the various concentrations of 
sodium chloride, and conc. I is at 52 and conc. II is at 54: 
TABLE V 
______________________________________ 
Conc. 
I/II .01M/.1M .1M/1M .01M/.01M 
.1M/.1M 
______________________________________ 
S-17 38.0 27.2 -1.6 -1.0 
S-18 45.9 28 
S-21 35 24 -9.1 +0.1 
S-16 41.9 27 
S-16 49 24.8 -98.8 -10.1 
(treated 
with PEI) 
S-15 49.3 29.2 
S-15 57.3 13.3 -91.8 -13.0 
(treated 
with PEI/ 
MgSO.sub.4) 
M-15 17.3 6 -5.0 -.2 
D-16 32 8 -10 -.1 
M-19 16.2 2.2 -3.0 +.2 
D-15 32 8.0 -10.0 -1.0 
______________________________________ 
The above results show that sandstone, marble and dolomite can be 
classified as anionic exchange membranes. Treatment of the sandstone slabs 
with either a PEI solution, or with a PEI solution and a magnesium sulfate 
solution substantially alters the voltage. Measurement of the electrical 
resistance of both treated and untreated slabs have been found to be 
approximately 50 Kohms. 
EXAMPLE 6. 
In accordance with Example 1, graywacke sandstone aggregate was treated 
with various polyethylenepolyamine polymers of the type illustrated by 
XD-30259.01 of the Dow Chemical Company, having a molecular weight in the 
range of about 431 to 629. There was utilized a 10% aqueous solution of 
the polyethylenepolyamine to treat the aggregate. Treated and untreated 
aggregate were evaluated in accordance with the sulfate soundness test and 
the following results were obtained, where %D indicates weight percent of 
rock loss due to degradation, "control" indicates the absence of 
polyethylenepolyamine and MW indicates molecular weight of the 
polyethylenepolyamine: 
______________________________________ 
MW % D 
______________________________________ 
control 
85 
431 14.3 
507 14.0 
596 15.0 
629 16.9 
______________________________________ 
The above results show that the polyalkylenepolyamine utilized in the 
practice of the present invention is effective as a polyelectrolyte to 
impart enhanced degradation resistance to untreated aggregate although a 
decrease in degradation resistance results as the molecular of the 
polyalkylenepolyamine increases. Based on this date, those skilled in the 
art would expect that polyalkylenepolyamines having a molecular weight up 
to about 1,000 would also impart a satisfactory degree of degradation 
resistance to untreated aggregate following the same procedure. 
Although the above examples are directed to only a few of the very many 
variables which can be employed in the practice of the present invention, 
it should be understood that the present invention is directed to a much 
broader class of polyelectrolytes which can be used in the form of an 
aqueous solution or an organic solvent solution to treat a much broader 
variety of aggregate and shaped stone structure. As used in describing the 
practice of the method of the present invention and the products obtained 
therefrom, the term "polyalkylenepolyamine" is more particularly defined 
in Vol. 10, pages 616 to 621 of the Encyclopedia of Polymer Science and 
Technology, John Wiley and Sons, Inc., 1969.