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NBSIR 88-3714

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National Bureau of Standards

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Mechanical and Physical

Properties of Coquina Stone from

the Castillo de San Marcos

National Monument

L. I. Knab and J. R. Clifton

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Building Materials Division

Gaithersburg, MD 20899

January 1988

Sponsored by:

National Park Service

Historic Architecture Division

1980 Island Ford Parkway

Dunwoody, Georgia 30350

NBSIR 88-3714

MECHANICAL AND PHYSICAL

PROPERTIES OF COQUINA STONE FROM

THE CASTILLO DE SAN MARCOS

NATIONAL MONUMENT

L. I. Knab and J. R. Clifton

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Building Materials Division

Gaithersburg, MD 20899

January 1988

Sponsored by:

National Park Service

Historic Architecture Division

1980 Island Ford Parkway

Dunwoody, Georgia 30350

U.S. DEPARTMENT OF COMMERCE, C. William Verity, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Mechanical and Physical Properties of Coquina Stone from the

Castillo de San Marcos National Monument

by Lawrence I. Knab and James R. Clifton

Center for Building Technology

National Bureau of Standards

1. Introduction

Castillo de San Marcos is located in St. Augustine , Florida, on

the shore of Matanzas Bay, about a mile from the Atlantic Ocean.

The Castillo is the oldest existing masonry fortress constructed

with coquina stone. Its construction was started in 1672 and many

modifications were made until its final deactivation as a fort in

1900. The outer walls of the structure were once covered with

lime plaster-^-*, most of which has been completely eroded.

Gradually, the exposed surfaces of the exterior stone have

weathered and some of the most severely deteriorated stone has

been replaced. Several large vertical cracks have developed near

the northwest and southwest corners which has caused concern

regarding the possibility of structural problems.

The Castillo is exposed to seasonally heavy thunderstorms and

seawater spray. Coquina is a porous stone which can be easily

penetrated by water and, as a consequence, the walls of the

Castillo are damp and in some areas efflorescence is observed.

In addition, the terreplein (roof) has numerous cracks, and

water appears to be able to penetrate the walls through the

terreplein.

The National Park Service (NPS) has developed a preservation

program for the Castillo which includes assessing the structural

condition of the walls, identifying moisture migration patterns,

and characterizing some of the important mechanical and physical

properties of coquina stone. Knowledge of the mechanical and

physical properties of coquina is needed to make decisions on the

structural stability and integrity of the fort as well as its

durability. Insufficient information, however, is available to

make such decisions. The purpose of the work described in this

report was to characterize some of the important mechanical and

physical properties of coquina such as compressive and flexural

strengths, dry density and water absorption.

2 . Coquina Stone

Coquina stone was formed from cemented sea shells and shell

fragments^. in the coquina stone samples investigated, the

* Raised numerals refer to ref erences in section 6.

1
shells were incorporated into the stone in a fairly uniform

bedding plane pattern (figure 1). This pattern resulted in the

formation of a highly porous stone with high water absorption,

low dry density, and low compressive strength (see Section 4).

3. Specimens, Preparation, and Testing Procedures

The coquina stone samples, which were air-freighted from Florida

by the NPS to the National Bureau of Standards (NBS) in Gaithersburg,

Maryland, consisted of (a) a nonhistoric piece not from the

Castillo but from the vicinity of St. Augustine, Florida, which

was roughly rectangular and measured 16x7x6 in; (b) several

smaller nonhistoric fragments; and (c) a historic sample from the

Castillo, which was an irregularly shaped piece with the longest

dimension about 13 in. (In this report, "historic" refers to the

coquina stone sample taken from the Castillo.) The exact

location of the retrieval of the historic sample was described by

the NPS as : "Castillo de San Marcos National Monument

Southwest Bastion, north scarp (wall)

Approximately 3 feet from corner and 4 feet from mean water

line

.

Note: Water at this particular section of the moat is

sea water which is subject to tidal effect;

sample was retrieved from a structurally

disturbed area where a crack runs north-south;

one section of the stone cracked while in situ

(which clearly suggests strong distresses prior

to removal)."

From the large nonhistoric sample, 32 cubes were cut and tested

in compression and 3 beams were cut and tested in flexure; from

the historic sample, 24 cubes were cut and tested in compression

and 2 beams were cut and tested in flexure. A diamond saw blade

was used for cutting. The cubes were approximately 2 in on each

side and the beams were approximately 2x2x6 in (beam span during

testing was 4.68 in). The cubes were cut such that the bedding

planes were approximately perpendicular to four of the cube faces

and parallel to the other two faces (see Figure 1., ASTM C 170^).

The beams were cut so that the bedding planes were approximately

parallel to the top and bottom of the beam as tested - i.e.

during flexural testing, the load was applied at the midspan of

the beam and the direction of loading was perpendicular to the

bedding planes. The cubes tested included two cubes cut from the

two ends of each beam after the beam had been tested in flexure.

(That is, there were 6 cubes taken from the 3 nonhistoric beams

and 4 cubes taken from the 2 historic beams tested) . Where

2
possible a

, the compressive strengths were determined according to

ASTM C 170 3

. Because of the friable and somewhat crumbly nature

of the coquina stone, it was not possible to saw the opposite

faces of cubes and beams to be parallel and flat - rather the cut

faces were only approximately parallel and flat; the surfaces as

sawn were used as bearing surfaces for compression testing - no

sanding or grinding were performed. The cubes were selected at

random from the historic and nonhistoric samples. For the

compression cubes, the following test conditions were studied:

(a) Loaded perpendicular to the bedding planes - referred to as

the "PER" loading direction; the PER loading direction was

considered by the NPS to be the typical loading direction of the

coquina stone. at the Castillo de San Marcos National Monument

(b) Loaded parallel to the bedding planes - referred to as the

"PAR" loading direction

(c) Dry (after drying at 105-108°C for 22-24 h or, for a few

cubes*3

, drying at 48°C to constant weight) - referred to as the

"D" test condition (see below for a more detailed description of

treatments performed on specimens)

(d) Wet (after immersing for 51-52 h in (i) distilled water at

room temperature, or (ii) sea water, which was obtained from the

vicinity of the Castillo, at room temperature) - referred to as

the "WDIST" (distilled water immersion) or the "WSEA" (sea water

immersion) test conditions.

All beams were tested dry at or near room temperature after they

had been dried at 105-108°C for 22-24 h.

Water absorption (percentage of dry weight) and bulk specific

gravity0 determinations were made on all cubes and beams prior to

compression or flexural testing.

The absorption, bulk specific gravity, compression, and flexural

tests were performed as follows. The beams and cubes were dried

at 105^-108 degrees C for 24-26 h, soaked in distilled water for

a There were a number of variations. For example, in some

cases the lateral dimension (distance between opposite vertical

faces) was less than the required 2 in, but almost always

exceeded 1.90 in; also in some cases, the ratio of the height to

the lateral dimension was less than the required 1:1, but the

ratio was almost always greater than or equal to 0.9:1 - see

Section 6.1 of ASTM C 170 3 . k An exception was the drying of three cubes at 48°C to

constant weight - see table 2.

° Bulk specific gravity calculations were made according to

Section 9 of ASTM C 97 4 .

3
48-50 h at room temperature, then the absorption and bulk

specific gravity values were measured according* to ASTM C 97^.

The cubes and beams were further treated as follows: (a) cubes

to be tested after immersion in distilled water were kept

immersed in distilled water until just prior to testing in

compression (the total immersion time was 51-52 h - just prior to

compression testing, the cubes were removed from the water and

their surface water removed); (b) cubes and beams to be tested

dry were dried at 105-108°C for 22-24 h and tested in compression

or flexure in their dry condition; (c) cubes to be tested after

immersion in sea water were dried at 105-108°C for 22-24 h,

immersed for 51 h in sea water at room temperature, then removed

from the water and their surface water removed just prior to

testing in compression; and (d) cubes which were cut from both

ends of each beam after the beam was tested, were dried an

additional 23-24h at 105-108°C prior to testing to remove any

water absorbed during cutting the cubes from the beams.

All compression cubes were tested at or near room temperature

using approximate load rates of either 1000-1200 Ibf/min or 1600

lbf/min. Tables 1 and 2 give the loading and test conditions for

the compression cubes. The beams were tested in flexure at or

near room temperature using a deformation rate of 0.02 in/min

(deformation applied by the testing machine to the beam at the

beam centerline).

In addition to the bulk specific gravity measurements, approximate

dry density determinations were made by dividing the oven dry

weight of the cube by the approximate volume of the cube (based

on the measured length x width x height of each cube).

4. Results and Data Analysis

Tables 1 and 2 give the compressive cube strength results for the

historic and nonhistoric coquina stone samples respectively.

Included are the absorption, bulk specific gravity, and dry

density values for the respective compressive specimens. As

shown in the tables, the data are divided into sets corresponding

to the specific test conditions used in the compressive testing.

For each set, the mean, standard deviation, and coefficient of

variation ((standard deviation/mean) x 100) is given for the

compressive strength. Table 3 presents the minimum and maximum

values of the compressive strength (for the PER and PAR loading

directions), absorption, bulk specific gravity, and dry density

* There were several variations, including weight

measurements taken to the nearest 0.1 g rather than the required

0.02 g and absorption and bulk specific gravity measurements

taken on the beams and the nonhistoric fragments, where the

longest dimension (e.g. 6 in long beams) exceeded the required 3

in maximum dimension.

4
for the historic and nonhistoric samples. Also, the mean,

standard deviation, and the coefficient of variation for the

absorption, bulk specific gravity, and dry density data taken

collectively for the historic (table 1) and nonhistoric (table 2)

samples are given in table 3.

4.1 Compressive Strength and Flexural Strength

There was considerable variation ( table 3 ) between the maximum

and minimum compressive strength values for a given loading

direction and stone sample (historic or nonhistoric) - for

example, the value of the ratio of the maximum to minimum

compressive strength was about 2 in the PER loading direction for

the historic as well as the nonhistoric samples. Values of the

coefficient of variation of the compressive strength data sets

for the historic sample (table 1) ranged from 14.5 to 39.9

percent while the corresponding range for the nonhistoric sample

(table 2) was from 4.6 to 21.8 percent.

Crushing and, in some cases, bulging was evident during compression

testing of the cubes.

The strongest effect on the compressive strength for the test

conditions studied was that of the direction of loading relative

to the bedding planes ("PER" and "PAR"). Table 4 shows four

comparisons of the PER and PAR loading directions, with each

comparison consisting of two data sets taken from tables 1 and 2.

Included in table 4 are values of the ratio of the mean compressive

strength of the PAR loading direction to that of the PER loading

direction. The range of the values of this ratio was 1.90 to

2.82. Values* of the "t" statistic and the corresppnding

cumulative distribution function (

t

ccjf ) are shown^ > ° . In this

report, only two-tailed "t" tests for comparing the means are

provided (i.e., the null hypothesis was that the means of the two

samples being tested were equal and the alternative hypothesis

was that the two means were not equal). Values of tccjf of 0.9 5

and greater for positive "t" values and 0.05 and less for

negative "t" values were considered to be statistically significant

in this report and correspond to a two-tailed test with a 0.10

For unequal sample sizes, an "F" test (reference 5, page

4-8) of the equality of the variances was performed. If the

calculated cumulative distribution function was equal to or

greater than 0.95, then it was considered that the variances were

not equal and the Behrens-Fisher test (reference 6, page 235) was

used to compute the "t" and tccj£ values; otherwise the "t" test

which assumes equal variances was used (reference 5, page 3-23)

to compute the "t" and tC£f values. For all cases of equal

sample sizes, the "t" test which assumes equal variances was used

to calculate "t" and tC £f values. These procedures were used for

all "t" and tcc^f calculations in this report.
level of significance. In this report, the "t" and tccjf values

based on small sample sizes (e.g., n = 3 to 6

,

as in tables 4 and

5) were considered approximate. The "t" and tcdf values,

however, were considered meaningful in analyzing the data. As

the tC(^f values in table 4 show, the difference between the two

loading directions was considered significant in three of the

four comparisons and was fairly close to being significant (i.e.,

tcdf = 0*089 instead of less than or equal to 0.05) in the

remaining case. If it is assumed that there was no difference in

compressive strength between immersion in distilled water and sea

water (see below), then Sets H-2 and H-5 (table 1) provide

additional support that there was an increase in compressive

strength in the PAR as compared to the PER loading direction

( ratio of the mean compressive strength of the PAR to that of the

PER loading direction was 2.58; the "t" and tcdf values for

comparing the means were -3.78 and 0.032 respectively). The

increase in compressive strength in the PAR as compared to the

PER loading direction is evident in figure 2, where the various

data sets in tables 1 and 2 are plotted. Thus, figure 2 and the

comparisons in table 4 strongly suggest that substantial increases

in compressive strength occurred when testing in the PAR direction

as compared to the PER direction for both the historic and

nonhistoric samples.

Using a format similar to that of table 4, the effects of the

condition of wetness on compressive strength are shown in table

5. Values of the ratio of the mean compressive strength of the

dry (D) test condition to the wet (WDIST and WSEA) conditions

ranged from 0.858 to 1.31, with 5 of the 6 comparisons having

ratio values of 1.13 to 1.31. The "t" and tccjf values show that,

in two of the comparisons where the ratio values exceed 1, the

difference between the means could be considered to be statistically

significant. In these two cases, there appears to be a small

increase in the compressive strength of coquina cubes tested dry

as compared to wet. The effects of the condition of wetness are

also evident in figure 2.

One comparison could be made with regard to the effect of

immersion in distilled water (WDIST) as compared to sea water

(WSEA): Set H-2 versus H-3 (table 1). The means (and the

standard deviations) of the compressive strength for the two sets

were almost the same, indicating that there was essentially no

difference in compressive strength between immersion in distilled

water as compared to sea water.

A comparison can be made with regard to the effect of loading

rate by comparing sets NH-2a and NH-2b (table 2). The value of

the ratio of the means of the compressive strength of the higher

(1600 lbf/min) to lower (1000-1200 Ibf/min) load rates was 1.16

and the "t" and tC(jf values were -1.50 and 0.083 respectively,

indicating that the higher load rate may not have caused a change

(increase) in the compressive strength. (It is noted that the

cubes in Set NH-2b had three cycles of 22-26 h drying at 105-

108°C prior to testing as compared to Set NH-2a, which had two

6
cycles of drying - this extra drying cycle is not considered to

have caused a substantial change in the compressive strength

values in Set NH-2b* . ) If it is assumed that there is no

difference in compressive strength between immersion in distilled

water and sea water (see previous paragraph), then the difference

in mean compressive strengths between sets NH-3 and NH-4 is

probably attributable to the effect of load rate. The value of

the ratio of the mean compressive strength of the higher (1600

lbf/min) to lower (1000-1200 lbf/min) load rates was 1.18 and the

"t" and tg^f values were -1.98 and 0.040 respectively, suggesting

that the increased load rate caused a small increase in the

compressive strength. An increase in compressive strength with

increasing rate of load application was not unexpected - for

example, a similar trend has been documented for concrete 7 '^. It

is also noted that the sea water immersion required an extra

cycle of drying at 105-108°C as compared to immersion in distilled

water - the extra drying is not considered to have substantially

affected the compressive strength.

A comparison can be made with regard to the temperature used to

dry the cubes. In Set NH-1 (table 2), the cubes had two cycles

of drying to constant weight at 48°C as compared to set NH-2a

which had two cycles of drying for 22-26 h at 105-108°C. The

value of the ratio of the mean compressive strength of the lower

temperature (48°C) drying to that of the higher temperature (105-

108°C) drying was 1.19 and the "t M and tC£f values were -1.43 and

0.098 respectively, indicating that drying temperature did not

appear to have caused a significant change in compressive

strength.

The variability of the coquina stone investigated was assessed by

comparing the differences in compressive strength between the

historic and nonhistoric samples: Set H-l versus Set NH-2b and

Set H-2 versus Set NH-4. The values of the ratio of the mean

compressive strength of the historic to that of the nonhistoric

samples were 1.47 and 1.44. Based on the corresponding "t"

(-5.9, -3.1) and tC(^f (0.000049, 0.0075) values, the compressive

strength of the historic sample was considered to be different

(larger) than that of the nonhistoric sample. The differences

in compressive strength between the historic and nonhistoric

samples for the comparisons discussed are shown in figure 2.

* Similarly, there did not appear to be a substantial

difference in compressive strength for the cubes in set H-l

(table 1) which had three drying cycles as compared to the cubes

in set H-l which had only two drying cycles.

7
Compressive strength did not appear to be strongly correllated

with absorption or bulk specific gravity.

To give a preliminary indication of flexural strength, two beams

were tested from the historic sample and two* from the nonhistoric

sample - the beams and compression cubes were cut from the same

samples. The flexural strengths (extreme fiber stress) for the

historic sample were 153 and 182 psi (mean = 168 psi) and for the

nonhistoric sample were 116 and 125 psi (mean = 120 psi). These

flexural strengths correspond to subjecting the bottom beam

"fibers" to tension and the top beam "fibers" to compression in

directions parallel to the bedding planes. The value of the

ratio of the mean flexural strength of the historic sample to

that of the nonhistoric sample was 1.39, which was roughly

similar to the corresponding values of 1.44 and 1.47 (see above)

for the ratio of the mean compressive strength of the historic

sample to that of the nonhistoric sample.

4.2 Absorption, Bulk Specific Gravity, and Dry Density

The percent absorption values ranged from 14.3 to 18.9 for the

historic sample and from 16.0 to 20.9 for the nonhistoric sample

(table 3). The difference between the maximum and minimum

absorption values was about 5 percent for both the historic and

nonhistoric samples.

The bulk specific gravity values ranged from 1.58 to 1.68 for the

historic sample and from 1.54 to 1.64 for the nonhistoric sample

(table 3). The difference between the maximum and minimum bulk

specific gravity values was 0.10 for both the historic and

nonhistoric samples. The dry density values ranged from 1.36 to

1.55 g/cm^ for the historic sample and from 1.32 to 1.50 g/cm7

for the nonhistoric sample.

The variability of the coquina stone with respect to its absorption,

bulk specific gravity, and dry density properties was assessed as

follows. The value of the ratio of the mean absorption value

(table 3) of the historic sample to that of the nonhistoric

sample was 1.10. Based on the corresponding "t" and tccjf values

(-5.6 and 4.1 x 10” 7 respectively ), the absorption of the historic

Actually three nonhistoric beams were tested - due to

testing machine difficulties the results of one beam could not be

used.

8
sample was considered to be- different than that of the nonhistoric

sample. The value of the ratio of the mean bulk specific gravity

value of the historic to that of the nonhistoric sample was 1.03.

Based on the "t" and t^f values (-6.4 and 1 x 10~ 7 respectively),

the bulk specific gravity of the historic sample was considered

to be different than that of the nonhistoric sample. Similarly,

the value of the ratio of the mean dry density of the historic

sample to that of the nonhistoric sample was 1.05 and the dry

density of the historic sample was considered to be different

than that of the nonhistoric sample ("t" and tcdf values of -6.1

and 1 x 10” 7 respectively) . In addition to the large nonhistoric

sample (16x7x6 in), three smaller nonhisto;ric fragments were obtained

from several nonhistoric coquina pieces. Preliminary absorption

and bulk specific gravity determinations for the three fragments

resulted in absorption values ranging from 10.6 to 12 . 2 ( percentage of

dry weight) and bulk specific gravity values ranging from 1.91 to 1.96-

substantially different from the corresponding values given in

table 3. These preliminary data, combined with the differences

discussed above in the absorption and bulk specific gravity

values of the historic as compared to the nonhistoric samples

given in table 3, demonstrate the large degree of variability

found in the absorption and bulk specific gravity values for the

coquina stone samples investigated. Additional evidence indicating

variability in the different samples was the difference in the

dry density between the historic and nonhistoric samples and the

difference in compressive strength (and flexural strength)

between the historic and nonhistoric stone samples.

5. Discussion and Significance of Results

The values of absorption (14-21, percentage of dry weight, table

3 ) of the coquina stone were extremely high relative to absorption

values for concrete aggregates (about 0.2 to 4.5,

percentage of dry weight 9

). Similarly, the dry density values

(1.32 to 1.55 g/cm9

, table 3, values include voids) of the

coquina samples were extremely low relative to density values for

common building and monument stone (density in g/cm9 of about 1.8

to 3.1, see reference 10). The high absorption and low dry

density values of the coquina stone are consistent with its

visibly evident porous structure. Relative to compressive

strengths of common building and monument stone (minimum compressive

strength of about 1000-2000 psi - based-^- 9 on "0.1" kilobars

uniaxial compressive strength) , the values of the coquina

compressive strengths were extremely low (72-413 psi, table 3).

The compressive strength values of the coquina stone in the

typical loading direction ( PER - load directed perpendicular to

the bedding planes) were the lowest, with many values below 100

psi (tables 1 and 2). The extremely low compressive strength

values of the coquina stone are believed to be caused, at least

in part, by the porous and friable nature of the coquina stone.

The compressive strength values (tables 1,2, and 3) are preliminary

because they are based on only two samples and only one of the

9
samples was from the Castillo. Additional coquina stone samples

need to be taken at the Castillo to better estimate the compressive

strength of the coquina stone.

The extremely low coquina compressive strength values are reason

for concern because of the very large difference in the compressive

strength of the coquina stone relative to common building stone.

The extremely low coquina compressive strength values need to be

taken into account when analyzing the load bearing and structural

capacity and the corresponding factor of safety of existing

structural elements (walls, etc.) comprised of coquina stone.

For example, assuming a dry density value (including voids , table 3 ) of

1.55 g/cm3

, the component of compressive stress due to the dead

load of the coquina stone alone (effect of mortar between coquina

blocks neglected) would be 0.67 psi per foot of height*. At the

bottom of a 32 ft high wall (average height of exterior wall of

the Castillo de San Marcos National Monument assumed to be 30 to

32 ft), the component of compressive stress due to the dead load

of the coquina stone would be 32 x 0.67 psi = 22 psi. A similar

calculation assuming that the coquina stone absorbs 20 percent

water (based on its dry weight, table 3) results in a density value of

1.86 g/cm3 (= 1.55 + (0.2 x 1.55)); the corresponding component

of compressive stress due to the dead load of the coquina stone

for a 32 ft high wall would be (1.86/1.55) x 22 psi = 26 psi.

These dead load calculations are preliminary because : (a) they

are based on only one sample of coquina stone from one location

at the Castillo, and (b) as the results of this report have shown

(see below), there was considerable variability in the physical

properties of the coquina stone, including its absorption and

density. Hence, additional coquina stone samples need to be

taken (also see previous paragraph) at the Castillo to better

estimate the actual absorption, density, and corresponding dead

load of the coquina stone. The calculations, however, illustrate

that the computed dead load stresses (22 to 26 psi) are substantial

when compared to the compressive strength values for the typical

loading direction (72 to 175 psi, table 3). Any additional loads

(other dead load, live load, wind load, buoyancy, etc.) and other

factors (mortar joints, taper or tilt of wall, etc.) would also

need to be taken into account in the structural analysis and in

establishing the actual stress levels.

The wide range in the absorption and bulk specific gravity values

in the three samples of coquina investigated (table 1, historic;

table 2, nonhistoric; and additional nonhistoric fragments)

clearly indicate the large variability in the coquina stone

investigated. Additional evidence indicating variability in the

different samples was the difference in the dry density between

the historic and nonhistoric samples, and also the difference in

compressive strength (and flexural strength) between the historic

and nonhistoric stone samples.

* That is, (1.55 x 62.4 lb/ft 3

) x 1 ft = 96.7 lb/ft 2 which

is equivalent to 0.67 lb/ in2 per foot of height.

10
For both the historic and nonhistoric coquina stone samples, the

compressive strength appeared to be substantially higher when the

stone was loaded parallel (176-413 psi - table 3 and figure 2) to

its bedding planes as compared to when the stone was loaded

perpendicular (72-175 psi -table 3 and figure 2) to its bedding

planes. The reason for this difference in strength due to

loading direction is not known.

The creep characteristics of coquina stone, which could result in

substantial and unwanted deformations, need to be investigated.

Creep should be measured at anticipated stress levels, moisture

conditions, temperatures, and at the anticipated loading direction

relative to the bedding planes. The unusally low compressive

strength of coquina stone may intensify the potential problem of

creep.

The effects of long term water immersion on the strength of

coquina stone also need to be investigated. Similarly, the

effects of wetting and drying cycles on the strength of coquina stone

need to be investigated. The conditions used in the immersion and

wetting-drying tests should simulate the Castillo environment

(e.g., temperature, water type (rain water, sea water, ground

water, etc.) as well as tidal action); reference 11, for

example, provides information on factors affecting the dissolution

of calcium carbonate.

Acknowl edgement

s

This work was funded by the National Park Service, Southeast

Region, Historic Architecture Division. The authors appreciate

the statistical consultation provided by Dr. James J. Filliben of

the NBS Center for Applied Mathematics. They also acknowledge

the assistance of Mr. David Savage in the water absorption and

bulk specific gravity determinations and Mr. Nat Waters in the

preparation and testing of the test specimens.

11
6.

References

1. Rands, D.G., Davis, S.D., and Arana, L.R. , "Chemical and

Biological Processes in Coquina of Castillo de San Marcos

National Monument," Schweiz. Z. Hydrol. 46/1, 109-116, 1984.

2. Schmidt, W. et.al., "Report of Investigation NO. 88, The

Limestone, Dolomite and Coquina Resources of Florida," Bureau of

Geology, Florida Department of Natural Resources, Tallahassee FL,

1979.

3. ASTM "Standard Test Method for Compressive Strength of

Natural Building Stone," ASTM C 170 - 85, Annual Book of ASTM

Standards, Volume 04.08, Philadelphia PA, 1986.

4. ASTM "Standard Test Methods for Absorption and Bulk Specific

Gravity of Natural Building Stone," ASTM C 97 - 83, Annual Book

of ASTM Standards, Volume 04.08, Philadelphia, PA, 1986.

5. Natrella, M.G., "Experimental Statistics," National Bureau of

Standards Handbook 91, National Bureau of Standards,

Gaithersburg, MD, 1963.

6. Brownlee, K. A. , Statistical Theory and Methodolgy in Science

and Engineering , John Wiley and Sons, Inc., New York, NY, 1960.

7. Neville, A. M. , ACI , Hardened Concrete: Physical and Mechanical

Aspects , Monograph No. 6, American Concrete Institute, Detroit,

MI, and The Iowa State University Press, Ames,IA, ch. 4, pp. 33-35.

8. Mindess, S. and Young, J.F., Concrete , Prentice-Hall Inc.,

Englewood Cliffs, NJ, 1981 , pp . 421-422

.

9. Neville , A. M. , Properties of Concrete , John Wiley and Sons,

Inc., New York, NY, Second Edition, 1973, Table 3-11, p. 126.

10. Robertson, E.C., "Physical Properties of Building Stone,"

Conservation of Historic Stone Buildings and Monuments , National

Academy Press, Washington D.C., 1982, pp. 62-86.

11. Friedman, G.M. and Sanders, J.E., Principles of

Sedimentology , John Wiley and Sons, Inc., New York, NY, 1978.

12
Table 1

.

Compressive Strength, Absorption, Bulk Specific Gravity, and Dry

Density Values for the Historic Coquina Stone Cubes

Set Compress i ve Strength Absorption

(%)

Bulk®

Speci f ic

Gravity

Dry e Density

( g/ cm

3

)

Test a Conditions Cube

Data

(psi )

Mean s.d. d

(psi) (psi)

b

cov

(%)

H— 1 D , PER 1 .

1

149 18.7 1 . 59 1.44

1 .

1

130 15.4 1.65 1.42

1 .

1

148 15.2 1 . 67 1 . 51

'1.1 103 18.9 1 . 58 1 . 37

1 .

1

165 17.2 1.63 1.49

1 .

1

170° 16.9 1.63 1 . 53

1 .

1

141 C 17.4 1 . 61 1.46

1.1 169° 17.4 1.61 1.46

1 .

1

146 C 147 21.2 14 .

5

16.9 1.63 1 . 53

H-2 WSEA , PER 1 . 1 146 16 .

3

1.65 1.47

1 .

1

89 16.6 1.64 1 . 36

1 .

1

132 16.9 1 . 63 1 .51

1 . 1 138 126 25.5 20 .

2

16.0 1 . 64 1 . 50

H-3 WDI ST , PER 1 .

1

175 14 .

3

1 . 68 1 . 55

1 .

1

120 17.8 1 . 60 1.37

1 .

1

120 15.9 1 . 66 1.44

1 .

1

109 17.5 1.62 1.47

1 .

1

118 128 26.4 20 .

6

17.1 1.62 1.44

H-4 D , PAR 1 .1 397 17.6 1.64 1.46

1 .

1

176 16 .

7

1.63 1.44

1 .

1

264 279 111 39.9 16.6 1.62 1.49

H-5 WD 1ST , PAR 1 . 1 236 16.0 1.65 1.47

1 .

1

413 d 17.3 1 . 64 1 . 50

1 .

1

327 d 325 88.5 27.2 16 .

1

1.64 1.49

a D = testedl after

/drying; PER = loaded perpendicular to bedding

planes; PAR = loaded parallel to bedding planes

;

1.1 = 1000- 1200 lbf/min,

approximate load rate; WDIST = tested wet after immersion in distilled water;

WSEA = tested wet after immersion in sea water .

s.d. = standard deviation; cov = (standard devi at i on/mean ) xlOO

Cubes cut from beam ends after beams were tested in flexure.

The load rate was approximately 1100 lbf/min up to about 80 percent

of the failure load, then the load rate was increased to approximately 11000

lbf/min and maintained at that rate to failure.

0 Bulk specific gravity determined according to ASTM C 97(there were

several variations - see text); dry density determined by dividing the oven dry

weight of a cube by its measured (length x width x height) approximate volume.

13
Table 2. Compressive Strength, Absorption,

Density Values for the Nonhistoric

Bulk Specific Gravity

Coquina Stone Cubes

and Dry

Bulk® Dry e Set Compressive Strength Absorption Speci f ic Density

Test K (%) Gravity

Conditions 3 Cube Mean s.d. cov° (g/cm

Data (psi) (psi) (%)

( psi )

NH-1 D , PER 1.6 13

1° 16.0 1.64 1 . 38

1.6 136° 13.2 1.60 1.40

1.6 148 C 138 8.7 6.3 17.6 1.60 1.36

NH-.2a D, PER 1.6

1.6

1.6

1.6

1.6

1.6

82

90

119

129

129

148 116 25.3 21.8

20 .

1

18.3

17.5

18.0

17.5

18.4

©

1.56

1.58

1 . 62

1.61

1.62

1.61

1.37

1.32

1.41

1 . 38

1.39

1.40

NH- 2b D , PER 1 .

1

89 d 13.0 1 . 60 1.43

1.1 105 d 19.9 1 . 59 1.43

1.1 90d 20.9 1.54 1.36

1 .

1

108 d 18.0 1.60 1.43

1.1 108d 19.9 1.59 1.43

1 . 1 99

d 100 8.7 8.7 20.9 1.54 1.36

NTH3

WDIST , PER 1.6

1.6

1.6

1.6

1.6

111

90

116

99

99 103 10.4 10.1

18.9

18.5

18 .

7

18 .

1

Values

1.55

1.61

1.60

1.61

missing

1.40

1.37

1.42

1.35

1 . 37

NH-4 WSEA, PER 1 .

1

107 Values missing 1.42

1.1 72 18.0 1.60 1.41

1 .

1

102 17.9 1.58 1.38

1 .

1

89 13 .

5

1.60 1.40

1 .

1

82 20.4 1.55 1.32

1.1 72 37 .

3

14.9 17.0 18.2 1.57 1.37

MH- 5 D , PAR 1.6

1 .

6

1.6

301

388

29 3 327 52.7 16 .

1

20.1

17 .

5

18 .

7

1.59

1 . 62

1 . 59

1 . 39

1.45

1.36

MH-6 WDIST , PAR 1.6 24 3 16.2 1 . 58 1 . 50

1.6 263 17.3 1.59 1.42

1.6 243 250 11.5 4.6 19.6 1.58 1.42

3 D = tested after drying; PER = loaded perpendicular to bedding

planes? PAR = loaded parallel to bedding planes ; 1.1 = 1000-1200 lbf /min

and 1.6 = 1600 lbf

/

min

,

approximate load rates? WDIST = tested wet after

immersion in distilled water? WSEA = tested wet after immersion in sea water .

° s.d. = standard deviation? cov = (standard deviation/mean ) xlOO

c Prior to

Q absorption and bulk specific gravity determinations, cubes were dried at 48 C to constant weight and soaked in distilled water at room temperature for 48-50 h. Prior to compression testing, the cubes

were again dried at 48 C to constant weight. This is in contrast to the

105-108 C drying temperature used for all other cubes (see text for

further details).

Cubes cut from beam ends after beams were tested in flexure.

0 Bulk specific gravity determined according to ASTM C 97(there were several variations - see text); dry density determined by dividing the oven dry weight of a cube by its measured (length x width x height) approximate volume.

14
Table

3.

Summary

Statistics

for

Compressive

Strength,

Absorption,

Bulk

Specific

Gravity,

and

Dry

Density

for

Historic

and

Nonhistoric

Samples -

Based

on

All

Values

in

Tables 1

and

2.

u

>i

+j •H>

03uOO

*H

•Hu0

a,

COHa

CQ

00C0

•rH 4404u0

CO b<

CO 0 a > —

• rH

CO

CO 44

a> cn u c

a, cd s u o 44 u co

03<

a,

03DSW

a.

b> ld r* 0 • • • • u rH PO rH CN— - -—- b cn o • cn in cn cn b o o o o • • • • • CO o o o o —

— -—

-—- c cn r" <P 0>

03 CO ^ id cn

CD t • • • 2 H rH rH rH'—

^—v * CO IT) H* O X vO LD cO ID

03 • • • . 2 rH rH rH i—1 - ' • -—

CO co CN

C id cn ID CO • r-1 • • « • 2 rH H rH rH " ' .—.

00—r b> CN cO 0 • • u cO CO b • cn CN b o CN • • • CO rH1

rH

C CO ID

03 • •

CD cO CO 2 rH r-l

O'*

X • • 03 CO o 2 i—! CN

cn o C • • • rH rf cO 2 rH rH X co CO

03 r-H CO 2 H* cn C cO cn

•rH r-» nr 2 rH CN X ID CO

03 r* H* 2 rH rH C

•rH cp CN 2 CO P"

CD rH04

CD s

rH 03 a CO e

03

u

CO •rH .—. U

—

U rH 0 CN

•rH 4J U CD CO 0 0 rH •H rH

-u

b rCb

CO 03

G 03

H -|4 0 44 X — 2 — ooX

CO r-r. CD c c 03

03 CD rH S

cu \G

CP 0 c •H •H 4-4 b 03 b -r-l <D > b CD b 0

4-1

b • U

rH CO 03

CD c b

rH 0 c

rH •H 03

03 4-1 44 u •rH CO

03

b

—r

04 c0 II b u

CD c b 4-4 0

03 CO •H 0 0 44 rH +4 03 •rH

II

b

w

<D 03 OS 44 > < 03 04 rH MH

CD 0 • Sh

CO 4J

0) >H c c <D 0

03 rC •rH H 4-) O a 0 •H

4H

rn ^4 <44 c 0 0

•H 0 b CO u b c

a) 0 II b • rH

4-1 > 0 -n 0

4-4 c u • r—1 u mh -

03 <0 c H b 0 G • rH 0 u 4J • rH 0 03 b 44 rH c > 0 CN 0

04

b

!h

b

CD c b O4 03 Sh

03

b rHb

(D c b co 03

03 CD 44 0 rH CO rH b

03 II

II 4-4

OS CD

b

w (D « 04 CO CO

03

b

O

15

Bulk

specific

gravity

determined

according

to

ASTM C97(

there

were

several

variationssee

text);

dry

density

determined

by

dividing

the

oven

dry

cube

weight

by

its

measured

(length x

width x

height)

approximate

volume.
Table

4.

Comparisons

of

the

Effect

of

Direction

of

Applied

Load

on

Compressive

Strength:

Load

Applied

Perpendicular

("PER")

as

Compared

to

Parallel

("PAR")

to

Bedding

Planes.

CN CN in 1 O 1 O 1 O

O

rH

H

H

H

4-4 "0

X

XXX 0

44 01 CN CN 0 e ft ft c 00 cn CO CO

4J 0 00 cO • • ft ft CN cn CO CO 1 1 1 H1 2 r* 44 4J 01 01 c c d O u u

44 4-1 03 03

OS a;

O H* CN co < w 01 in 00 H' O4 04 • • • • Z = rH CN CN CN

4-1 44 0 0 c c

(0 ra d (D s E

03c0 H

H cO cO

•rH e • • •

4-1

H

HHH

•rH -* 2 H H os as cD CO as as C • • < w « • < w 2 0 H rH 04 a, H H 04 Q4 4-J cj *» * 2 as as H E-i os as E-i E-1 c 4-1 < w CO CO <c w co CO 0) 03 04 a. IH 1H 04 o, IH h-t

1-4 CD - Q

QQ 2

4-1 E-*

aa 2 2 q

a 2 2

co

a;> • •rH • CN in ^ co in

•rH 03

H • • • • • • ft 03 • 04 H H C0 cO cn in H O

03 03 ' rH CN CO CN in cn

HH 0) u

04£ C •rH 0 d 03 oi C'' in co n* co 0 CO

CJ (D

O4 CN CN CN rH uo 0 E CN rH cn rH CO iH CN H 0 cn 01 cn in co cO co UO • 02 d ^ rH in cn in cn cO CO

4-1 1 1 1 l l l 1 1 0) x x X X X 2 2 2

CO 2 2 2 2 G >1

•rH

H E 2 D \ D >

44 (H •rH 03 2 rH 44 D

rH • H CD 3 2 44 D rH D 0 03 a d 2 *H 03 > d CN 2 D 0 H C4 z rH 1 C 44 0 •H - :

II

C c 0 rH

cc >H 0 •rH rH w •rH 44 d

04 II 03

U I4 c - CN ft •>» rH D 3 03 Oi 0 E 44 D 2 c iH E 3 C •rH •H C rH d >1 • — 0 d

C4 03 14 •rH > H 2 D D 44 C 44 3 44

C/3 54

d 44 2 2 0 D rH d •rH O

iH 4-)

O4 54 44 2 44 44 44 d id 2 D 03 D

4J

C 2 •rH r-> 2 •rH 2 Xj

CD

D 2 2

(D 44 2 DD 2

03 03

D 44 > C

D 2 03 •rH •rH 1 • 4-1 D 44 54 0 44 d d

CD II 44 rH

a

H II 3 E

04

a rH • E 0 E D (H u 3 0

<0 • rH CO

DU

03 c rH IH 44 44 0 d a d 2 0

(D •rH

u 2 2 C

C 44

d •rH

D 0 cd a •- d 2 03

4-1 •rH 03

DC

d

03 > 2 D 03 0 D D D 44 Q4 U 2 2 d c 03 54

•rH

d 14 •rH

D 0

54 2 0 14 &4 0 54 rH 2 c 54 4J id d 0 0

03 2 II 0 •rHu • •rH G rH 03 rH 2 id as I4 2 ft C 44 < D D C ^}* 0 03 04 44 E d c d E c

II ft E *H

u 0

II 03 •rH *H •rH

ft

D

X 14 44 44 2 2 C 0 D 03 O 2 • d >4 44 *H D

03 iH Oi’+4 44 CO

•-

Q4 O4 d

d • D ft d 44 C D

rH 03 2 44 03 •H > Q4 D c - D •rH E 44 •rH c 2 : D 44

(0 id 2 *H 44 44

d

03

u 2 s 2 z 0 2

•rH

DD

CD

D

H 2 44 44

D 44

C

C

a 2 03 2 0 0 D 0 H D 44 0 D

4-1

U 44 44 44 2

03 0 D

44 14 0 II 54 2 0 U 0 d cO d D 44

•rH

HH < 44

54 14 3 w H4H3

C 0 D u 11 CO 2-t D

4-1 2 •rH 2 OD -X

03 E 2 co 44 54d

•rH

OC ft •- 44 2 G D H 14 2 D

04

DC

D

D

II II 14 2 44

d 03 54

D c d

D 2 C Q4 d 2 44 1 2

-x

-x * * -X -X

16
200

rd2s0u

CO0

CM CM rH

Q 1 o 1 o 1 o I rH rH rH

>i = X

XX 0 < Q Cd * <4-1 (D o o

CO * 2 • • •

•• 2 * u r- On

m 2 = 4J w

4-)

cnc 0 co 0 0 * ln LD 0 2 * • • • -u rd * r-H rH o

CO 2 4J 1 1 1

CD 03 c > CD •H CO

CO z

CO 0 <

CD 0 Cd 0 CO a— 2 e = Z 0 F0 z U CO Q 0

i—i z O c Q 0 2 <4-1 z CO 0 E-< r- an un

CO >— CO «-H pH CO

CO

a

H • •

0)

n 03

Q r-H rH o c a) d> 2 U 2 S z

<D rd 2 2 <44O

<4-1 rQ o a) c H 03 0 2 0 0 S

•rH _jj 4-1 CO -H

T3

Q co

r-' c 0 c 0 rH rH U -rH •rH r-H • • 2 • rH rH 21 cn •rH r-H •* 0 C 2 r-H •* rH 0d rH QS •H -K a • cd • Cd * < 2 4J * 0 <—I Cd rH CU rH Qj U co

r—

u ' CU

CD 0 4J Qd - QC Eh as E-*

<4-1 C_ On 2 Cd < Cd CO < co

<44 r-» CO Oh Cd CU 44 2 44 W 0 3 0 - CO - Q ~ a

4J 0 EhQ 2 O 2 Q 2

(D 2 2 0 CO 2 0

•rH (D * cm un CM nT un 2 0 > 2 • rH • • • • • • 0 a, •rH • 0 r-H IT) H v^Q -H CO

co 0 a CM CM CM CM

H CO

CO CO rH 0 d) CD 0 co s-l CO s-l 2 0 •pH

•rH Q) e 0 0 so r. co an un 0 E O 0 a 0- CN x^ CM px cm

03 S U e rH rH rH rH cm cn

O-I

H £0 o U 2 * c on 2 on un

m cn

in • O

(D 2

r-H r-l CM rH cn ^ un

4J 1 1 i i 1 1 03 (D cn x X CC X CC

E-< CO

4-1

O

H

O rH CN 0

-*

C 1 *H 0 0 2 c 0 H CM CM 0 0 0

<-H 1 1 1 2 rH *H H O O O 0 0 0 H H rH 0 2 Ui > H 0 0 X X X 2 S C <44

11 0 E 0 2

un

m ^r 0 -H •H

O • • • Cd rH 4J 2

rH un

m 2 S—1 0

CU 11 0 C 0 • 44 0 2

CN • •» i-H <44 2 44 cm • 0 H CO un 2 c H 0 CP • • • 0 •H 44 0 C

rH

H CM 0 >1 0 •H * rH l 1 1 0 0 3 2 0 H 2 0 0 0 0 2 2 2 0 0 0 0 •H s 0 0 H 4J 0 0 H 2 cu 0 2 U 2 <44 0 0 0 0 cn 44 H 2

4J c 2 0 2 •H || S4 0 0 2 0 0 0 2 2 E 4) 0 0 0 0 0 CO 0 > 0 0 2 H 3 *r4 0 1 2 Q 2 0 2 0 0 0

cn xtf

H 0 II 44 0 H 0

rH

H

m

H •X 0 0 2 • • • a Q rH U) E

rHH rH cz 0 0C 0 0 • «* H -lJ *rH O • 0 C H fO H 0 0 S4 C On • 0 •H ui 0 0 nr c 4-4 0 2-'-' •H 0 0 CU 0 0 2 0 2 •rH 0 U4 0 0 0 > 2^0 0 •»-* 0 0 E 2 2 u 2 2 0S 0 O

•H 0 4-4 -H 0 0

V4 2 0 0 0 cn 0 S4 r-4 S V4 0 2 0 •H 0) 0 0 0 2 II X 44 O -H

sO sO • rH

C 0 <44 • rH • r* 0 QC 54 0 2 0 H • H c 4J < 2 0 2 * H •» 0 0 Cu 2 4J 0 0

SO Qd

H *» sO CC 0 0 0 0 • • Cd • Qd • < II •x 2 U 2 0 H CU rH [d 1-4 cu II 0 x -r4 0 C> • 0 C 2 2 0 -r4 OS Eh Cd - a Eh 2 2 C -h 0 0 2 4-) Cd CO Cd < < CO 2 • 0 E 44 •H f0 CU H CU Cd CU H 0 h4 \ 0 2 2 On - Q - CO x a ••* 2 <44 0 0 0 0 a 2 a 2 a 2 0 •- 2 4J 2 2 0 H 0 (J1 rH 0 0

cu 0 c 11

H QJ

g 4J •HO = 02 cn nT px on px un 0 0 2 O < 2 0 0 U 2 so 2 = 0

un 0 CO nr CM -H •H 0 <-1 2 0 2

CM

HH LP)

h 0 H 2 2 0 0 c cu ll 2 0 0 0 0 0 2 0

4J S-4

u so

u 1 2 cn 0 • 0 0 0

sO cn

O • px

O <44

U

H

u 0 x 2

rH

O

O r- cn un 0 0 0 0 0 >1

H rH 1—1 co

m cm •rH

H 2 3 H

S4 S4 0 c 20

U 0 0 U 0 2 2> 0

4-1 2 •H QJ Oh 2

SO un sO sO cn cn 0 S 2 C <—1 2 2

•rH 0 C ‘rH rH

U 0 a 0 S -H 2 0 0 2\ 4J 0 2 0

II 11U 44 0 •"D CO

H 0 2 '4 0 0 0 12 i-th c 2 <~! 2 2 0 >

CN cn CM nT un so 1 1 1 1 l l * X 2 2 2 2 2 4e * 2 2 2 2 2 2 * -K *

17
18

Figure

1.

Coquina

stone

from

Castillo

de

San

Marcos
500

lx

0) XJ I I

II II

II I III II oo oo

rn

OO

<N oo

(isd) HiONSHiS 3AISS3HdW00

xJ 03

CO

C

4) 0

EU

Ec/o i—i Q2

Eh

c/3 i—i Q2<

Cd

C/3 3<

CjJ CO3

&-CO

I—I Q3

E-CO

I—I Q3Q

XXo

OS<

CL,

OS

<C

cu

OS<

a, x<

CuXw

a,

os

Cd

CL,

osu

cu

OS

CdCu

cO

cD

CO

osCd

a.

ascd

CL,

cO

u

a)u

•rH Q

CTi C

03

(002

<u XJ

03 OS

cnc

•pH 03

(0O2

CO CO O o/ 2 rH

S3

E- 03 Cd ECO —

03 xj

03 CD 2 xj 1 03 'rH 03 2 03 X 2 2 03 O •

03 Lx 03 03 0 Q, 03 xH

rH a, XJ a,

m 03 to 2 XJ l II 03 03 03 X •> XJ to as c 03 < -rH II 03 03 a- 2 C *rX \ <c 0 Lx -WH XJ 03

to 2 co to 03 rH 3 0) ' ID c 0 Lx 1 03 O •* •px 03 2 rH O Lj Lx 2 2 OicD 03 0

rH XJ XJ 2

CTl 03 to

O . ,i CHS -rH •rH

Xj1 -H 2 2 H 03 cO 03 3 2

03 • 03 0

<U rH rH c (0 rO XJ 03 -H II 0) 0 C xJ to xj 03 CO 2

•pH 2 Lx

Hi" u, c 03 0) 1 f3 ‘"H • 

2 rH E C 03 XJ 2 3 ’H rH 0

CJ XX Cu •h33 C 2 rH 03 rH 0 03 rH C -r-> to 03 CN 0) o to 1 0,0 Lx 03 0 2 u, cn ai C XJ

03 rH E 0

a, i 2 XJ 03 O 'rH to 03 03 O Lx 0) O U 0 03 03 rH 03 •rH a

n 3 XJ 2 • l 0 II CM 0 0 — 2 rH CO XJ O CN 2 rH to

II • XJ •rH (0 0) —1 0) 2 rH ro OS 2 2 1 Cd .. II C3 03 2 2 to 03 0 xj

0) 03 2 2 *r 3 XJ 03

cr ro to •» c C H JJ Lx xj 03 •pH Q, XJ 03 ,03 >1 XJ XJ

in cn ii 03 03

X

03 2 03

C 2 03 03 'O CCI CN •rH E-, •rX XJ 1 1 1 >h 03 C/3 03 Lx D 03 h 03 03 0) 2 2 2 xj 03 a to 03 xx 2 2 to to

03 c 03 •—

rH 0 » -pX 2 1 03 xJ to CJ X 03 03 c rHO

XJ <—1

XJ 0 1 CO

to 0) 03 •pX 2 O

03 rH L, to 2 rH

XJ Lx 1 03 03 a) XJ LD

11 lx 03 2 03

O

03 0 c C/3 —i

a Qx rH +

CN + +

(N

03c

03

U3

03 rH2

03C • 2 —O 0) rH

to

a2

to 03 xj to

03

CO 0)

03

O

03 t0U

03 2 Lx XJ O

Lx CO O -<H XX 2

03C

0) c

XJXJ II 0

rH 2 a, i

03

03 0) 03 rH

xj 03 cn to

0) 0)

Lx

C

4J

O

C0 XJ

to 03> O • pH *rH

to

w

to

O

03 XJ

Lx CO Q, *rX 0y

ii

03 : 2 * 3 = U

CN

03

Lx3

tji •rH

[-H

19
NBS-114A irev. 2-80

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

1. PUBLICATION OR

REPORT NO.

2. Performing Organ. Report No. 3. Publication Date

SHEET (See instructions) NBSIR 88-3714 JANUARY 1988

4. TITLE AND SUBTITLE

Mechanical and Physical Properties • of Coquina Stone from the Castillo

de San Marcos National Monument

5. AUTHOR(S)

Lawrence I. Knab and James R. Clifton

S. PERFORMING ORGANIZATION (If joint or other than NBS, see instruction s) 7 . Contract/Grant No.

NATIONAL BUREAU OF STANDARDS -

U.S. DEPARTMENT OF COMMERCE

GAITHERSBURG, MD 20899

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City . State, ZIP

)

National Park Service

Historic Architecture Division

. Type of Report & Period Covered

1980 Island Ford Parkway

Dunwoody, Georgia 30350

10. SUPPLEMENTARY NOTES

J Document describes a computer program; SF-185, FlPS Software 5ummary, is attached.

11. ABSTRACT ( A 200-word or less factual summary of most si gnificant in formation. If document includes a significant

bi bl iography or literature survey, mention it here

)

Some important mechanical and physical properties of coquina stone, which was used to

construct the Castillo de San Marcos National Monument, were determined to aid in the

condition assessment of the monument. Mechanical properties determined included

compressive strengths under several different testing conditions, including testing wet

as compared to dry, and the direction of the applied load relative to the bedding plane j orientation. Physical properties determined included water absorption and dry density.

The results indicated that the coquina stone has an extremely low compressive strength

relative to common building stone. The low compressive strength was believed to be

caused, at least in part, by the friable and very porous nature of the coquina stone.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

Castillo de San Marcos; compressive strength; coquina stone; dry density;

mechanical properties; physical properties; water absorption

13. AVAILABILITY

X i Unl imited

I ; For Official Distribution. Do Not Release to NTIS

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