AD-A171 892 ALKALI-SILICA REACTION IN CONCRETE FROH FONTANA DAN
NORTH CAROLINA TENNES. . <U> ARNV ENGINEER MATERHAVS
EXPERIMENT STATION VICKSBURG NS STRUC..
UNCLASSIFIED A D BUCK ET AL. SEP 8S MES/WYSL-86-9 F/Q 13/2
MICROCOPY RESOLUTION TEST CHART
NATIONAL BUREAU OF STANDARDS- 1963-A
MISCELLANEOUS PAPER SL-86-9
US Army Corps
of Engineers
ALKALI-SILICA REACTION IN CONCRETE
FROM FONTANA DAM, NORTH CAROLINA,
TENNESSEE VALLEY AUTHORITY
by
Alan D, Buck, Katharine Mather
Structures Laboratory
DEPARTMENT OF THE ARMY
Waterways Experiment Station, Corps of Engineers
PO Box 631, Vicksburg, Mississippi 39180-0631
DT1C
iZLECTE
StP 1 6 806
f py I)
Jg)
September 1986
Final Report
Approved For Public Release Distribution Unlimited
G3
LABORATORY
Prepared lor
Tennessee Valley Authority
Knoxville, Tennessee 37902
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ELEMENT NO
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■ 1 i I 1 Lt lltRIllVT JTtUIIE/ UldWIltdllUfiy
Alkali-Silica Reaction In Concrete from Fontana Dam, North Carolina, Tennessee Valley
Authority
12 PERSONAL AUTHOR(S)
in.
Bush. Alan D.. and Makhet.., Katharine
13a TYPE OF REPORT
Elnal-CfiBfliL
13b TIME COVEREO
FROM_TO
14 OATE OF REPORT (Yeer. Month. Diy)
September 1286-
15 PAGE COUNT
_u_
16 SUPPLEMENTARY NOTATION
This is Concrete Technology Information Analysis Center (CTIAC) Report No.
76.
1 17 COSATI CODES 5
FIELD
GROUP
SUBGROUP
18 SUBJECT TERMS (Continue on reverse if neetssery end identify by Woe* number)
Alkali-aggregate reactions
Concrete dams
Fontana Dam
J.' /*> 73 , 7 V!\
_ - < — — r
19 ABSTRACT (Continue on reverse if necessity and identify by block number) —
The Tennessee Valley Authority (TVA) in 1973Yrequested petrographic examination of several
concrete cores from Fontana Dam located in North Carolina to determine whether an alkali-
silica reaction had occurred. A petrographic examination was made, and the results of it
showed that there was evidence of alkali-silica reaction. While the evidence of reaction
was conventional (gel, rims on aggregate particles, cracks), the type of aggregate was not
one usually then thought to be reactive. The reactivity of this rock, with one variety
variously described as quartzite or feldspathic muscovite schist or metamorphic subgraywacke
and another variety as schist or phyllite, was probably due to the presence of large
amounts of strained quartz
¥
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DO FORM 1473, 84 mar
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PREFACE
The 1973 work was funded bi the TVA, and permission was given by that
agency in 1974 for publication to make the results available to a wider
audience.
The report is being published due to the continued and increasing interest
in the recognition and classification of strained quartz as potentially
reactive aggregate material. Some of the concrete thin sections originally
prepared for this work were used as part of the basis for a paper on
classification of strained quartz to be presented at the 7th International
Conference on Alkali-Aggregate Reaction to be held in Ottawa, Canada, 18-23
August 1986.
This report was prepared by Mr. Alan D. Buck and Mrs. Katharine Mather,
Concrete Technology Division, Structures Laboratory. Mr. Bryant Mather was
the Chief, Structures Laboratory, during the publication of this report.
The funds for publication of this report were provided by the Concrete
Technology Information Analysis Center (CTIAC); it is CTIAC Report No. 76.
COL Allen F. Grum, USA, was the previous Director of WES. COL Dwayne G.
Lee, CE, is the present Commander and Director. Dr. Robert W. Whalin is
Technical Director.
NT »S CRA&I
OTIC JAB
U'announced
Justification
By.
Diet ibutio.i/
Availability Codes
Oist I
1
CONTENTS
Preface .
Conversion Factors, Non-SI to SI (Metric)
Units of Measurement.
Background.
Samples .
Test Procedure.
Results.. .
Summary .
References.
Tables 1-4
Figures 1-6
CONVERSION FACTORS, NON-SI TO SI (METRIC)
UNITS OF MEASUREMENT
Non-SI units of measurement used in this report can be converted to
SI (metric) units as follows:
Multiply
*1
To Obtain
inches
25.4
millimetres
angstroms
0.1
nanometres
Fahrenheit degrees
5/9
Celsius degrees or
Kelvins*
feet
0.3048
metres
pounds (force) per
square inch
0.006894757
megapascals
pounds (mass) per
cubic yard
0.59327638
kilograms per cubic
metre
* To obtain Celsius (C) temperature readings from Fahrenheit (F) readings
use the following formula: C ■ (5/9)(F - 32). To obtain Kelvins (K)
readings, use: K = (5/9)(F - 32) + 273.15.
3
ALKALI-SILICA REACTION IN CONCRETE FROM
FONTANA DAM. NORTH CAROLINA
TENNESSEE VALLEY AUTHORITY
Background
1. A petrographic examination of concrete cores from Fontana Dam was
requested by the Tennessee Valley Authority (TVA) to determine if an
expansive chemical reaction had taken place. It was suspected that an
alkali-silica reaction might have occurred and could be responsible, or
responsible in part, for past movement of the structure and for a large
crack that had developed apparently at a date fairly recent in years but
unstated.
Samples
2. Ten ft of 6-in.-diameter concrete core from core holes 1 and 3 was
received on 20 September 1973. An additional 3.1 ft of concrete core from
core hole 6 was received in December 1973. Identifying data are shown
below:
Concrete
Laboratory
Serial No.
TVA
Designation
Approximate
Length, ft
Maximum
Aggregate
Size, in.
Hole
TVA-9 CON-
1
WES-1(A)*
2.5
3
3, normal to
2
WES-2(A)
1.5
sloping face of
7
WES-3(C)
2.3
dam at elev.
1672 ft in Block 31
Pieces 1(A) and 2(A) fit together and come from the top of the hole; piece
3(C) comes from a spot that is about 6.5 ft below the bottom of piece 2(A).
This core is solid, not overcored.
3
WES-l(B)
1
3/4 or 1
1, vertical, top
4
WES-2(B)(1-1)**
1
of dam at elev.
5
WES-2(B)(1-2)**
1
1727 ft in Block 31
6
WES-3(B)(1-3)**
3/4
(in roadway)
8
WES-4**
1-1/2
3
9
WES-5**
1-1/2
The
letter designations were
added at
WES to differentiate between
identical TVA identifications.
All of these pieces had had a 1-1/2-in.-diameter cove removed from then
before receipt at WES.
4
Pieces 1(B), 2(B)(1-1), 2(B)(1-2), and 3(B) fit together and come from the
top of the hole; pieces WES-4 and WES-5 fit together and come from an area
that is about 5.5 ft below piece.3(B).
Concrete
Laboratory
Serial No.
TVA
Designation
Approximate
Length, ft
Maximum
Aggregate
Size, in.
Hole
TVA-9 CON-
10
Specimen 2**
1
1-1/2
6, vertical, in
11
Specimen 3**
1
gallery at elev.
12
Specimen 1**
1
>3
1586 ft in Block 31
Specimens 2
and 3 (CON-10 and CON-11) fit together; the
top of 2 is about
18 ft below the top of the core at the lower gallery floor; specimen 1 is
from an elevation about 8 ft below the bottom of specimen 3.
Test procedure
3. The cores were examined and logged. Each piece of core was then sawed
down its axis.
4. Drilled, sawed, and broken core surfaces were examined visually and with
a stereomicroscope for evidence of alkali-silica reaction and to determine
the characteristics of the concrete. Several sawed surfaces were ground to
provide surfaces better suited to this examination.
5. Several thin sections were made from pieces of core from holes 1 (TVA-9
CON-4, 6-8) and 3 (TVA-9 CON-1, 2); these sections were examined with a
polarizing microscope.
6. Samples of white porcelaneous material, that was believed to be alkali-
silica gel, were carefully removed from voids in the concrete with a dissectin
needle; samples of the gel from each core were placed in oils of different
refractive indices to make powder immersion mounts, and these mounts were
examined with a polarizing microscope.
7. A small composite sample of the white gel was obtained as described above.
The sample was ground in a small amount of water and the resulting slurry was
placed on a 1/4-in.-wide glass slide to dry; the air-dried film was X-rayed.
8. Rather extensive X-ray diffraction (XRD) examinations were made of selected
coarse aggregate particles and of cement paste concentrates from core from
TVA-9 CON-1, CON-2, CON-7j the aggregate and paste appeared closely similar
to those in the other two cores. Specific details are given below:
5
a. Portions o£ eight coarse aggregate particles from piece 3(C) and
of one particle from piece 1(A) were ground to pass a No. 325 sieve; these
powders were backpacked to minimize preferred orientation and were then
X-rayed.
b. Some of the clay-sized material (<2 p,m) was separated from portions
of the powdered coarse aggregate particles by sedimentation in water. The
clay-sized particles were allowed to settle from suspension onto glass
slides and to dry there. The resulting oriented clay slides were X-rayed
air dry. A second slide of each sample was X-rayed after saturation with
glycerol, and a third slide of each sample was X-rayed after saturation with
ethylene glycol. One slide was X-rayed while the clay film was still damp
from added water.
c. A concentration of cement paste from the top and from the bottom
portion of core piece 3(C) was prepared as follows;
(1) Small portions of the core were broken.
(2) The concrete fragments were sieved over a No. 100 sieve to con¬
centrate the cement paste in the sizes finer than the sieve.
(3) The samples of concentrated cement paste were ground to pass the
No. 325 sieve and X-rayed as tightly-packed powders.
9. All X-ray patterns were made with an X-ray diffractometer using nickel-
filtered copper radiation.
Results
10. Figure 1 is a copy of the TVA sketch which shows core locations in
block 31. Figures 2 and 3 are the TVA and WES logs of hole 1 (CON-3-6, 8,
9); figures 4 and 5 are the TVA and WES logs of hole 3 (CON-1, 2, 7);
figure 6 is the WES log of hole 6 (C0N-10-12). One break in the core from
hole 3 appears to antedate drilling. The break at elevation 1567.8 (hole 6)
appears to be old; the break at the bottom of specimen 2 from hole 6 (eleva¬
tion 1557.7 may antedate drilling; the break at the bottom of specimen 3
appears to be fresh.
11. Examination of concrete surfaces revealed the presence of white,
porcelaneous material and a clear, solid material in the voids that looked
like alkali-silica gel. While it was not rare, and while it was found
on sawed surfaces and on transverse breaks made in the laboratory, filled
voids were not over 3/16 in. (4.8 mm) in maximum dimension. Some lined but
not filled voids were considerably larger. Reaction rims usually quite
narrow (^ 1-2 mn) to somewhat wider in the more coarsely clastic rocks were
common. The aggregate appears to be composed of two extreme types with an
intermediate type which is present in minor amounts. The aggregate was
described in TVA Technical Report No. 12 as "quartzites" and "schists."
In TVA Technical Monograph No, 69,* June 1953, the schists are referred to
as phyllites, while the U. S. Bureau of Reclamation petrographers described
the "quartzites" as feldspathic muscovite schist;* in the present state of
rock names, mcfamorphic subgraywacke is the name one tends to confer on the
basis of composition of the more coarsely clastic rocks with predominant
quartz and feldspar and some muscovite and another brown somewhat pleiochroic
mica as it appears in concrete. The Bureau of Reclamation petrographers
called the dark fine grained rock phyllite. In this report we refer to
"quartzite" and "phyllite" for continuity and simplicity. Examination of
concrete surfaces showed cracks in a few aggregate particles which required
30X magnification to be detected; some propagated short distances into the
paste. Without the presence of the cracks that propagate from rock to paste
one would be reluctant to assume that the cracking was related to alkali-
silica reaction but the combination, with the presence of rims and clear and
porcelaneous gel makes the assumption that the rare thin cracks in the aggre¬
gate and paste are related to alkali-silica gel more convincing.
12. The examination of thin sections with a polarizing microscope did not
detect the thin reaction rims just inside the outer boundary of aggregate
particles which are seen in reflected light. By knowing which aggregate
particles had reaction rims, it was possible to examine the rimmed particles.
In one case the reaction rim included a large feldspar grain located at the
edge of the particle. Since continuous rims were common, probably most of
the different minerals in the aggregate occur within some rim.
13. If the amount and distribution of relicts of cement are considered
while the sections are examined in plane light, such relicts are moderately
abundant and about equally so in all 10 sections. This observation, and the
elevations in cores 1 and 3 from which the sections were taken, all suggest
that the sections represent similar mixtures of interior concrete. TVA
Technical Report No. 12, 1953, says that the cement content of the interior
mass concrete ranged from 0.80 bbl (300.8 lb) per cubic yard and W/C = 0.75,
but more frequently contained 0.85 (319.6 lb) and sometimes 0.90 bbl (338.4 11
per cubic yard. This information supports the idea derived from examination
of the sections that the cement contents were similar. Table 1 shows that
the similarity of the cement content indicated by relicts was not accompanied
by the relatively abundant large and relatively evenly distributed Ca(OH )2
crystals characteristic of mature concrete with a fairly high water-cement
ratio and a moderate cement content. Instead, there was a deficiency in
Ca(01I)2l most of the crystals were unusually small for concrete of the age
and water-cement ratio. In unaltered well cured mature mass concrete such
as one expects in a dam of this age, rather large calcium hydroxide crystals
border aggregate particles and appear as islands between them. In the
Fontana sections, with uncommon exceptions (table 1, 3-C), hydroxide bordering
aggregate was small, rare, uncommon, skeletal, and in some cases in all sec¬
tions there were aggregate particles of all types surrounded by paste that
did not contain Ca(0U)2. This condition is one evidence of alkali-silica
reaction perceptible in thin sections; it confirms the evidence of the widely
distributed rims and gel that alkali-silica reaction has taken place.
14. The white gel that was found in some voids in all three cores was
more tightly packed into the voids than is usual for alkali-silica reaction
gel. However, examination of it in powder immersion mounts indicated that
it is alkali-silica reaction gel. It was found to occur in several forms
which were similar to gel found associated with an aggregate composed of
quartzite and veinquartz in an alkali-silica reaction that occurred in
concrete in a dry dock.^ The following tabulation describes the gel types
found in the Fontana cores and their refractive indices.
Gel Type
Refractive Index
Seraicrystalline;
first order gray
birefringence in
crossed polarized
light.
n < 1.460
Salt and pepper type
in crossed polarized
light.
1.482 > n < 1.502
Alternating growth
layers of clear and
of tan translucent
gel; some of the
clear material is
amorphous.
1.480 > n < 1.520
15. In addition to peaks due to small amounts of contamination by calcite
and quartz, the X-ray pattern of the composite gel sample showed peaks at
the following positions;
d, Anr
;stroms
11.3
2.90
8.6
2.74
6.6
1.84
5.0
1.82
3.57
1.78
3.29
1.56
3.14
1.55
1.54
The identity of the crystalline material or materials responsible for these
peaks was not determined, but they were essentially the same as found for
some of the dry dock gel.^
16. The similarity of this gel in appearance, refractive indices, and
X-ray pattern to that found in the dry dock concrete^ is considered to
be conclusive proof that it is gel formed by an alkali-silica reaction.
The partial chemical analysis in Table 2 supports this concept.
17. Four of the nine aggregate particles that were X-rayed were quartzite
and the other five were phyllite. The composition of all nine particles
was similar. All of the particles consisted of substantial amounts of
quartz, plagioclase feldspar, and muscovite and biotite mica; potassium
feldspar and calcite or potassium feldspar or calcite were sometimes
present, and there was usually a small amount of kaolin clay; a small
amount of 14.5-angstron chlorite or vermiculite was present in one piece
of aggregate; a small amount of amphibole was tentatively identified in
several pieces. Small amounts of iron sulfide were detected with the
microscopes. Although the two major rock types differed in color and grain
size, they were very similar in composition. The similar composition of
the major rock types, as well as the rims and the Ca( 0 H )2 deficiencies
around both suggest that the reactivity comes from one or more of the same
constituents in both types.
18. One question that has been raised in discussion with TVA engineers,
particularly Mr. Bullock, is was reaction present in all of the cores
examined here? The answer given was yes, based on the presence of rims
and gel in cores from all three of the holes. In the hope of quantifying
the differences, if any, in the observed extent of reaction in the several
lithologic types, each rock type was counted on nine finely ground surfaces
prepared from cores from holes 1 and 3 (Table 3). Table 3 showed that in
pieces from hole No. 1 more than half of the quartzite was rimmed but only
one piece of the phyllite; in hole 3 slightly less than half the quartzite
was rimmed but no phyllite. It then came to mind that this phyllite is a
dark rock and the rims perceived had been on broken surfaces and had appeared
as color difference and difference in the inclination of the fracture.
Kammer and Carlson^ show a figure from Buck Dam closely resembling the rimmed
phyllite in the Fontana cores.
19. Therefore, counts of each rock type, without and with rims, and with
rims and associated gel, were made on fresh broken surfaces of all three
cores (Table 4). While Table 4 indicates a higher percentage of rimmed
phyllite than Table 3, little phyllite is accompanied by gel. The composi¬
tion of the aggregate in Tables 3 and 4 is compared below;
Total
Aggregate Percent of
Percent Type Reacted
Ground Surfaces
Quartzite not rimmed
36 \
72
Quartzite rimmed
36 5
50
Intermediate not rimmed
Intermediate rimmed
tr £
4
tr
Phyllite not rimmed
23 1
24
Phyllite rimmed
1 $
4
Total
100
Number of particles counted
199
Broken Surfaces
Quartzite not rimmed
20-a
Quartzite rimmed
53 (
79
84
Quartzite rimmed, with gel
6 >
Intermediate not rimmed
2->
Intermediate rimmed
2 l
5
50
Intermediate rimmed, with gel
1 3
Phyllite not rimmed
10 7
Phyllite rimmed
6 c
16
38
Phyllite rimmed, with gel
tr 3
Total
100
Number of particles counted
338
What Tables 3 and 4 and the summary above make clear is;
a. The composition of the aggregate is fairly consistent in these
cores.
b. Each lithologic variety is reactive but reactivity as judged by
the proportion of each variety showing evidence of reaction is most exten¬
sive in the quartzite and least in the phyllite.
20. Figure 1 shows that core hole 1 is at the highest elevation and
nearest the upstream face. Core hole 6 is at the lowest elevation and
not much farther from the upstream face than core hole 1. Core hole 3
starts at elevation 1675 and dips into the dam normal to downstream
surface. TVA Technical Monograph No. 69 shows on figure 27 that normal
reservoir levels range from 1590 ft in late December to 1708 ft in May
through August. On this basis hole 6 is usually below reservoir level;
the same is true of hole 3 on the downstream face; hole 1 starting from
the roadway has half or more of its length above normal maximum reservoir
level.
21. Gel was not abundant in this concrete but a comparison of gel observed
associated with rimmed aggregates, rimmed aggregates without gel, and the
sura of the two, all expressed as percentages of total aggregate is of some
interest:
Core Hole
With Associated Gel, %
Rimmed, %
Sum, %
1
9
72
81
3
3
68
71
6
13
38
51
While it is assumed that moisture is a necessary participant in the reaction
between alkali hydroxyl, and some aggregates, the results above suggest that
the concrete from holes 1 and 6 was provided not only with moisture to form
rims and presumably expand the coarse aggregate, but had more water available
to make visible gel than the concrete in core 3. We cannot advance any
reasonable suggestion why the visibly reacted aggregate is so much lower a
percentage of the total in core 6, which is also the core in which gel is
most abundant.
22. A question worth consideration in terms of future aggregate selection
and future treatment of the dam is: Did the alkali-silica reaction, which
is present in all the cores from block 31 examined here, contribute to the
stress developed, to growth in height, and development of the crack near the
curve in the left abutment? Reference (1) pages 230-235 notes that a daily
thermal cycle of Uo F produced by solar radiation may cause a maximum stress
of 600-800 psi which is relaxed as the temperature decreases; the stress
rise is 1*50 to 3>00 psi in summer and 300 psi in winter; these are average
rather than extreme stresses but probably apply near the surface. Reference (l)
also points out that there is a thermal gradient from the warmer downstream
to the cooler upstream face. If this represents a situation that continued
for several years or to the present, the warmer concrete toward the downstream
face would expand and the cooler upstream face contract; if the downstream
face ratchets as it lengthens, some of the increase in height and tendency
to tilt upstream may be regarded as the result of thermal effects on concrete
with a moderate thermal coefficient. While it seems reasonable to believe
that thermal influences were active participants in the behavior of the
structure, alkali-silica reaction has gone on in block 31 to a greater degree
than can be considered innocuous or negligible. To the extent to which
expansion caused by alkali-silica reaction was not restrained by the
abutments, and by the compressive strength and elastic modulus of the
surrounding and overlying concrete, alkali-silica reaction provided an
additional expansive force. The magnitude of the expansive force
may be judged by the length-change measurements in process at the
TVA laboratories. These measurements are most important as predictors
of whether additional growth caused by alkali-silica reaction may be
expected. It will also be interesting and significant to observe
whether or not the length-change specimens develop significant cracking.
One of the odd aspects of the concrete examined here is that cracks
not produced in pulling core are few and narrow; only one example was found
of cracks in the interior of an aggregate particle and dying out at the
rim, which is one characteristic of alkali-silica reaction in relatively
unrestrained concrete. The average, modulus of the concrete is said to be
5x10^ psi which suggests that the compressive strength should be at least
5000 psi. It is believed that the restraint of the abutments, foundation,
and overlying concrete of essentially structural quality prevented the
development of frequent cracks characteristic of less restrained concrete
of lower modulus undergoing alkali-silica reaction.
23. A second question, of more than academic importance as it may affect
choices of aggregate in future construction is: Why was this aggregate
reactive in this structure? Factors that bear on the answer are outlined
in the following:
a. Table 1-D from a TVA internal report of April 19U6 shows an average
alkali content of 0.61* percent as Na^ from one source of cement and maximum
values of 0.71 and 0.75 percent as Na 20 from two others used in the dam.
b. The major constituents of the aggregate are quartz and feldspars
(in approximately equal amounts) and the micas, muscovite, and biotite.
Minerals that have generally been accepted as reactive with the alkalies
in Portland cement vrere not detected.
c. In 1955 L. S. Brown^ recorded some observations on alkali-silica
reaction that appear relevant to the Fontana concrete. Concerning observa¬
tions on broken surfaces he writes:
"Across the bottom of Fig. lU a piece of quartz aggregate is seen.
Another piece of quartz is shown in Fig. 15, this one from the same
New York concrete shown in Fig. 5. Both of these pieces of quartz
show secondary features similar to those seen in the chert."
and of sawed surfaces:
"Figure 5 is from a 1920 construction in New York. Aggregate is a
natural sand and gravel. A particular feature here is that the aggre¬
gate is practically wholly quartz. The narrow dark borders can be
seen, though less plainly because of the better optical continuity
of quartz. Observable displacement is limited to a single crack that
passes from one piece of aggregate into another, terminating in both."
p
d. Buck and K. Mather observed the phenomena Brown discussed in several
cores in which no coarse aggregate other than quartzite and vein quartz was
detected.
e. Items c and d above are the only two documented and fully straight¬
forward Instances of the reactivity of quartz in concretes, believed to have
experienced normal temperature regimes, of which we know. The reactivity
of silica flour in autoclave products is well known.
f. However, the picture is complicated by the instances of reaction in
phyllite3 and other micaceous rocks.
g. These include Dolar-Mantuani^ who found reacted argillites in dams
200 miles north of Toronto and verified the reactivity of the argillite by
the expansion of mortar bars, in the quick chemical test and by expansion of
cylinders. Sand made from graywacke drill cores showed some expansivity in
mortar bars. Dolar-Mantuani described the argillites as follows:
"Many thin sections prepared from pieces of the foundation rock and
from coarse aggregate in the concrete revealed that the medium dark gray (N 4
in the rock-color chart) argillites from the Lady Evelyn Lake area are usually
weakly metamorphosed; they consist of quartz, feldspar, sericite, illite
and some chlorite probably interlayered with kaolinite. (The micaceous
minerals were determined by the X-ray method on the plus No. 30-size fraction
of the crushed varved argillite after the coarser grained, mostly greenish
varves were eliminated.) The micaceous minerals do not seem to envelop the
minute quartz grains completely."
h. Idom^ figured several particles of phyllites showing evidence of
alkali-silica reaction in concrete showing evidence of reaction; he appears
to ascribe the reaction to "soluble silica."
i. Mather^ stated:
g
"In 19l4l Parsons and Insley reported results of petrographic examina¬
tion of phyllite from Buck Dam, Va., as 'fine-grained microcrystalline quarts
and chalcedony, mica, calcite, and traces of feldspar, chlorite, and limonite.
Later in 19UU, Bean and Tregoning 9 reported studies of reactivity of aggregate
constituents in alkali solutions and one of the materials that they studied
was phyllite from the Buck Dam. They reported that it exhibited little
reactivity in their study. My discussion of this paper^ reviewed the infor¬
mation on the nature and reactivity of various forms of silica.
"In 19U0 Kelly et al 11 reported results of mortar-bar tests of a
variety of materials, again including the Buck Dam phyllite. They reported
excessive expansion only when KOH was added to the mortar in which this
aggregate was used; but only slight expansion when no additions were made."
j. Gillott, Duncan, and Swenson discussed reactions in concrete in
Nova Scotia^2 : The main alkali-expansive rock types of Nova Scotia are
of sedimentary origin: greyuackes, argillites, and phyllites. These rocks
contain little or no opal, vitreous silica or volcanic glass. Fine quartz,
which is a common constituent, frequently showed signs of strain, inclusions,
intergrowth and sutured boundaries. The resulting defect molecular packings
on the surface probably constitute a significant proportion of the total
quartz volume. Although such material may be a causative agent of
expansive alkali-silica reaction this has yet' to be demonstrated through
experiment. This fine quartz is the only mineral present in significant
quantity, however, that can be related to the reactive component of the
classical alkali-silica aggregates. Gillott et al noted various differences
in test behavior from more customary alkali-silica reactive materials and
suspected the mechanism differed. They determined the effect on diffraction
patterns of rock wafers of phyllite made before and after immersion in 2M
NaOH for various periods to be the expansion of 10-A micas to about 12.6 a,
and interpreted this effect as removal of interlayer material in the mica
of the phyllite, allowing the mica to swell to an unlimited extent as it
imbibed water. This hypothesis may be valid for the phyllites these authors
studied but it is not completely satisfactory for the Fontana aggregates
because the so-called quartzite (metamorphic subgraywacke) is more reacted,
and thus presumably more reactive, than the phyllite.
k. Dr. Mehta^ has examined some of the Fontana cores and noted exfoliation
of the phyllites in scanning micrographs, but regards the basis for swelling
in phyllite as similar to that of other permeable solids having high internal
surface and poor intercrystalline bonding.
2U. Summary .
a. All of the cores from Fontana Dam examined here have undergone alkali-
silica reaction, demonstrated by rims formed on crushed stone, the production
of gel, and rarely, the development of microfractures in the quartzite
(metamorphic graywacke) coarse aggregate projecting into the paste.
b. It is our opinion that the rarity of microfractures, which are common
in much concrete affected by alkali-silica reaction, results from the high
modulus and strength of the concrete which restrained some of the volume
change and formation of cracks in most of the aggregate and mortar.
c. Since the TVA has the results of other tests on concrete from Fontana,
TVA engineers are better able than we, since we have less information, to
judge the importance of alkali-silica reaction in the development of the
large crack near the curve in the dam. We believe that alkali-silica reaction
contributed to the expansion of the structure to the extent that the reaction
overcame the restraint but are not in possession of information that would
establish whether it played a significant role.
d. Probably the most important predictive tests on the future behavior
of the dam are length-change tests of cores or sawed prisms stored at
100# RH and temperatures similar to thosdthat can exist in the dam.
’Acceleration of the test by raising the storage temperature to 100 F will
increase speed with which the results become available without serious
danger of changing the mechanism and producing a misleading result.
e. No positive statements are made on the reactive constituents of
the aggregates. While some quartz, usually strained, is reactive in some
circumstances2jl4 the features of the quartz or the environment that
make this so are not established. The mica in the Fontana aggregates
appeared to be normal and the question of the reactivity of mica is not
yet entirely clear.
References
1. "Measurements of the Structural Behavior at Fontana Dam," Technical
Monograph No. 69, Tennessee Valley Authority, Knoxville, Tenn.,
June 1953.
2. A. D. Buck and K. Mather, "Concrete Cores from Drydock, No. 2, Charleston
Naval Shipyard, Charleston, S. C.," Miscellaneous Paper C-69-6, U. S.
Army Ehgineer Waterways Experiment Station, Vicksburg, Miss., June 1969.
3. H. A. Kammer and R. W. Carlson, "Delayed E^ansion of Concrete at Buck
Hydro-electric Plant," Jour . ACI, Proc. Vol 37, P 671, 19l*l.
1*. L. S. Brown, "Some Observations on the Mechanics of Alkali-Silica
Reaction," ASTM Bull . No. 205, p 1*0, 1955.
5. L. Dolar-Mantuani, "Alkali-Silica-Reactive Rocks in the Canadian Shield,"
Highway Research Record No. 268, National Research Council, pages 99-117,
6 . G. M. Idorn, Durability of Concrete Structures in Denmark , Technical
University of Denmark, Copenhagen, 1967, Fig. 1*7-53, and plate 15 on p 127
7. Bryant Mather, A Discussion of the Paper "Alkali-Aggregate Reaction in
Nova Scotia. I. Summary of A Five-Year Study," by M. A. G. Duncan, et al
Cement and Concrete Research , Vol 3, No. 3, p 333.
8 . W. H. Parsons and Herbert Insley, Jour . American Concrete Institute,
1*0, p 229, 191*1*.
9. Leonard Bean and J. J. Tregoning, ibid , 1*1 , p 37, 19l*l*.
10. Bryant Mather, discussion of ( 9 ), ibid , 1*1 p 52, 19l*l*.
11. T. M. Kelly, L. Schuman, and F. B. Hornibrook, ibid , 1*5 , p 57, 19l*8•
12. J. E. Gillott (Division of Building Research, Nat. Res. Council of
Canada, now with Univ. of Calgary, Calgary, Alberta), M.A.G. Duncan
(Atlantic Industrial Research Institute, Halifax, now with Ministry
of Roads, Salisbury, Rhodesia), and E. 6 . Swenson (Div. of Building
Research, Nat. Res. Council of Canada), "Alkali-Aggregate Reaction in
Nova Scotia. TV. Character of the Reaction," Cement and Concrete
Research , Vol 3, pages 521-535, 1973. Pergamon Press, Inc., printed
in the United States.
13. P. K. Mehta, A Discussion of the Paper "Alkali-Aggregate Reaction in
Nova Scotia - Character of the Reaction," by J. E. Gillott, M.A.G.
Duncan, and E. G. Svrenson, Cemen t and Concrete Research , Vol 1*, pages
335-31*3, 1971 '-. Pergamon Press, xir:., printed in the United States.
Table 1
Section
1-A-l
1- A-2
2- A-l
2- A-2
3- C
3-C-2
2- B
3- B
fc -1
k-2
1
Fontana Thin Sections
Description
Probably interior concrete. Residual cement
abundant but like the others. Deficient in Ca(OH) ?
by comparison with residual cement and especially d
so around some aggregate particles, both quartzite
and phyllite.
Like 1-A-lj both from elevation about 1 ft in from
and normal to face of core started at elevation 1672.
Depth 2.i*0 - 2.f>0. Both show too few small and
skeletal CaCOH)^ remains to agree with the relative
abundance of residual cement.
Elevation 10.1* - 10.85 in hole. Unhydrated relicts
as in previous.
Ca( 0 H )2 reworked and recrystallized to smaller
crystals; some deficiencies in hydroxide but also
some long typical crystals along borders of aggregate.
Depth 1.0 - 1.2 ft. Partly recrystallized fine¬
grained Ca(0H)2 and some deficiencies in Ca(0H) 2 .
Depth 3.15 - 3 . 55 . Resembles 2-B; deficient in Ca(0H)2.
Depth 9.1 - 9.5 ft. Similar to two previous.
ditto
Table 2
Chemical Analysis of Gel from Cores from Fontana Dam
Percent
Loss on ignition at 550 C 2ij.80
CaO h.76
KgO 6.68
Na 2 0 6.75
Si0 2 50.70
Sum 93.69
Weight of sample from all three cores * 0.0161 g
Calculated formula: 1.6 Na^jO’l.O K 2 0*1.2 Ca0*l2 Si0 2 *20 HgO
fafofrfo Hi ft hVifo i ft' InX mk ' i
Table 3
Reacted Aggregate on Sawed Surfaces
Ground Sawed Sur fa ces
Piece Quartzite Intermed. Phyllite
No. Rim Rim Rim
Hole
Piece
Quartzite
Intermediate
Fhyllite
No.
No.
. El¬
R&G*
R*
i&g*
R'- r
R&G*
Total
1
IB
3
io
6
1
1
-
1
3
25
2B
2
21
h
1
2
- .
1
5
-
36
3B
2
18
2
-
-
m
6
-
28
k
1
15
-
-
-
-
2
-
-
18
5
-1
U
JL
_ H
_2
_ZL
_22
TOTAL
15
77
12
3
3
-
6
ik
-
130
*
12
59
9
2
2
—
5
ii
100
3
1A
13
U8
-
2
2
-
5
8
1
79
2A
3
7
1
-
-
-
-
-
-
11
3C
Ji
_9
18
TOTAL
20
6U ■
1
2
2
mm
10
8
1
108
%
18
59
2
2
2
-
9
7
1
6
2
10
19
2
-
-
2
2
mm
-
35
3
9
9
7
2
•»
-
6
mm
-
33
1
13
11
2
-
-
-
9
-
-
35
TOTAL
32
39
11
2
-
2
17
-
103
*
31
38
11
2
—
2
16
«•
100
Summary
9 2
«. u It J r c r.. S?£_A ?/£— USd/2.
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COMfUHP »V
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y/b/71
CHtCKCO BY
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or 6fe/Ctss/4
. PROJECT
t&V&Atl &><sr}
Am A*r/r />^T^tdrp-
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6*itt rY ||1 <
£tfCTCt(AL Y/WlT |.
/r £ «P<**cA ,
f A»'~‘
) V -
£/ /67S~~
£A/£iT£L.
*Ihe slope of core 3 was redrawn
to correct it by WES. ^
&/. /627£ /
12-10-73
Sent 3 Cores +0 w&s
fer petrographic analysis
&/&0+,
6 ’x/o '(sAcuer
ZyIA'/>///£ A'/. /£8C.~.
^><src.T/o//
4P///£/lP^< 7 pjtutou 3/
Figure 1
£/.
/<oD0
© . ,^ s P et - 3
■' v 'Spet- 2
|j*-5pCC. Uo.l
/r/. / < s5l
\
Nofe’ Bonny drilled normal fo
fop surface of dom
UKMSSEl TOUT U1KCU1T
( KIB( (I I • | n:»||| k «tT
LOG OF 6-IIJ. DIAMETER TV A CONCRETE CORE NO. 1
FROM BLOCK 31, FONTANA DAM
Field No.
a Serial No.
1
• TVA-
Top is formed surface,
9 CON-
elev. 1727 ft. All breaks in
this core are fresh. The
top It pieces of core contain
3/1* or 1-in. maximum-size
WES-
3
aggregate. Two rebars at
1(B)
^ 1/2 ft.
-hvT-
Zt'lf
4 -
U-Ji
—
n
T
—
•P
A/
• 1
ill -
—hi
_ iii
1*1
...1
11-
— 1 ...
—
4 ‘L
x/vl»4
A
4 - 5.1
1 ' 1
'TiJX
i
rvW'j' >yvl
A 1-1/2-in. diameter core hole
starts with piece 2(B) and
continues to the bottom of
this core.
Some void fillings of white
gel and rimmed aggregate
particles were visible when
core was sawed along its axis.
Rebar at ^ 3 ft.
Vertical Scale: 1 square « 0.1 ft
Figure 3
TVA CORE 1 (CONTINUED)
Depth, ft
9
Field No. CLSerial No.
10 J
11 J
b
t
i
L
IJ
L
t-
1
T
•-
4«._
_jii_
-■
- if-
....
-
t-i.,
P,'-
"i*“
'
X-
;.liH
/VS/V
V
—
it 1
bid
_Ji—_
m
~
if
...
jjL
jL
_l L
~!
-j
- 1
-1
_i
1
i
1_
!-
A.
vy
I
—
—
I
n
t
TVA-
9 CON-
No core from 3.5 to 12.1-ft.
Maximum aggregate size in
these two pieces is 3 in.
WES-
h
I
WES-
5
i
End of core that was received.
Figure 3 (continued)
Hole 3
fJoie: Sonnf c/n//eJ norma/ ft
downstream face of Jem
) Figure 1*
FO//TAMA PAM
BLOCK J/
6 tm/ SOUP COX'OTC ' TC COCc
UMc'SSCC VCUV illthMITT
Klltlim milKliM IKSUUti
rXf
KUtmit
*4CC»«<.kKO
irr
Tsrn
LOG OP 6-IN. DIAMETER TVA CONCRETECORE NO. 3
FROM BLOCK 31, FONTANA DAM
ft Field No. CL Serial No.
Top of core is formed
surface; elev. 1672 ft.
Ehtire core contains
3-in. maximum size aggregate.
Old vertical crack for
first half ft.
Some void fillings of white
gel and rimmed aggregate
particles were visible when
core was sawed along its axis.
Old diagonal break.
Vertical Scale: 1 square * 0.1 ft
Figure 5
TVA CORE 3 (CONTINUED)
LOG OP 6-IN. DIAMETER TVA CONCRETE CORE NO. 6,
BLOCK 31, FONTANA DAM
Depth, ft
0
Field No . CL Serial No .
TVA
9 CON-
I
'jj
•!
i r"
• v»
...... il_
i ii
—
L«L
LliL_
LFT 1
Specimen
2
Sawed
rrt-
_t- f r
i ■
:-Specimen
H- 3
j-,_ i—* —i
i i
drt
-i-i
Sawed
—J.—L—1 Specimen
1
IT
_ip.
Figure 6
Upper break at elev. 156?.8
( 18.2 ft below gallery floor)
appears to be old.
The maximum aggregate size in
pieces 2 and 3 is 1-1/2 in.;
it is 3 in. in piece 1. A
1-1/2-in. diameter core hole
extends through all 3 pieces.
Break at 1565.8 may antedate
drilling. No core from the
interval 1565.8 ft to 1557.7 ft
was furnished.
Some void fillings of white gel
and rimmed aggregate particle
were visible when the core was
sawed along its axis.
As marked by TVA this was wrong
end up. Break at bottom is
fresh.
End of core that was received
Vertical Scale: 1 square ■ 0.1 ft
