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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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m 

HI? 




U a V> 




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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- 


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_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 





















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Sent 3 Cores +0 w&s 
fer petrographic analysis 


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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