NATIONAL BUREAU OF STANDARDS REPORT

Mia

CONTROL OF LEAKAGE THROUGH JOINTS

IN CAST- STONE MASONRY AT

THE NATIONAL NAVAL MEDICAL CENTER

Progress Report No. 1

by

A* Hockman, E. J. McCamley and

E. W. Krussell

District Public Works Office

Potomac River Naval Command

Bureau of Yards & Docks

Department of the Navy

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

To
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

THE NATIONAL BUREAU OF STANDARDS

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S^ATIDWAL BUREAU OF STANDARDS REPORT

HiS PROJECT MBS REPORT

1001-UO-U813 June 8, 19# UlUl

CONTROL OF LEAKAGE THROUGH JOINTS

IN CAST-STONE MASONRY AT

THE NATIONAL NAVAL MEDICAL CENTER

Progress Report No. 1

by

A. Hockman, E. J. McCamley and

E. W. Krussell

To

District Public VJorks Office

Potomac River Naval Command

Bureau of Yards & Docks

Department of tie Navy

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication, re|

unless permission Is

25, D, C, Such peri

cal ly prepared If U

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) on October 9, 201 5.

In part, Is prohibited

indards, Washington

jort has been spe.clflport for Its own use,

CONTROL OF LEAKAGE THROUGH JOINTS

IN CAST- STONE MASONRY AT

THE NATIONAL NAVAL MEDICAL CENTER

by

A. Hockman, E. J. McCamley and E. W. Krussell

Abstract

This is the first progress report of an investigation to determine causes and possible means of controlling leakage through the walls of some of the buildings

at the National Naval Medical Center. An experimental

waterproofing treatment applied to the masonry of Building No. 1, 19th floor and above is described, and results

of treatment given. Laboratory studies of thermal and

moisture properties were made on samples of the original

cast-stone used at the center. Thermal coefficient computed for temperatures between -|j. and +lIj.0 o F was

6.2 x 10“ ° per deg F and moisture expansion for 19 day

immersion was 0.0385 percent.

Laboratory studies are in progress on 50 samples of

calking materials. Tests including shrinkage, bond

plasticity, rate of hardening, etc., are described.

Measurements of joint movements made on four elevations, Building No. 1, 19th floor, over a 7 l/2 month

period, revealed movements averaging 0.0066 inches. A

complete graphical record is given of all joint movements

on four elevations. In general, joint movements corresponded to changes in temperature.

Inspection of the masonry made 7 l/2 months after

the waterproofing treatment was applied, revealed the

existence of cracks in 80 percent of the vertical joints

examined. Cracks ranged from hairline (less than 0.001

in.) to l/l6 in. (corner joint, southwest). The average

of the openings in the joints was estimated to be 0.006 in.

No leakage has been reported sine© the application of the

waterproofing treatment.

Plans for future study in the project include: (1)

A continuation of joint movement measurements with a

Brinell microscope and new type of gage station, (2)

Completion of the study of calking materials, ( 3 ) Determination of the effects of various relative humidities

on expansion properties of cast-stone, and (1^.) Study of

effectiveness and durability of several types of silicone

water-repellents

.

Table of Contents

1. INTRODUCTION

2. WATERPROOFING TREATMENT OF CAST-STONE AND JOINTS

2.1 Condition of joints and panels before treatment

2.2 Field tests of silicone waterproofing

2.3 Preparation of the joints for treatment by contractor

2„li Re-pointing and grouting of joints

2.5 Application of silicone solution

2. 6 Effects of the waterproofing treatment

3« LABORATORY STUDIES OF CAST- STONE

3.1 Thermal expansion test

3.1.1 Test procedure

3.1.2 Test results

3.1.3 Comparative expansion data for stone used as facing material

3» 2 Moisture expansion test

3.2.1 Test procedure - non-waterproofed sample

3.2.2 Test procedure - waterproofed sample

3*2.3 Test results

3.3 Absorption test

3.3.1 Test procedure

3.3® 2 Test results

3.3.3 Comparative moisture expansion and absorption data for

stone used as facing material

ho LABORATORY STUDIES OF PLASTIC CALKING MATERIALS

11.1 Description of tests

1101.1 Fabrication of cast-stone blocks

11.1.2 Rate of hardening

11.1. 3 Shrinkage

U.l.U Tenacity

It. 1.5 Consistency

h. 1.6 Bond and plasticity at room temperature

U.1.7 Bond and plasticity at low temperatures

U.1.8 Exposure studies

5. MEASUREMENT OF JOINT MOVEMENTS

5.1 Description of strain gage

5.2 Installation of gage stations

5.3 Frequency of measurements

5.U Results of measurements

6. RELATION OF LABORATORY TESTS TO FIELD STUDIES OF JOINT MOVEMENTS

7. PRESENT CONDITION OF MORTAR JOINTS

8. PUNS FOR FUTURE STUDY

9. SUMMARY

10.

REFERENCES

-1-

L, INTRODUCTION

At the request of the District Public Works Office of the Potomac

River Naval Command and under the sponsorship of the Bureau of Medicine

and Surgery, Department of the Navy, the National Bureau of Standards

has started a study of the causes and possible control of leakage by

wind-driven rain through the walls of some of the buildings at the

National Naval Medical Center, Bethesda, Maryland* In planning the

first part of this study, the Bureau proceeded with the assumption that some and possibly most of the leakage occurs through the open mortar

joints 5 such faulty joints being prevalent throughout many of the buildings that are faced with the cast-stone panels* This decision was reached

after several inspections were made of the Medical Center buildings by

members of the Bureau staff* In order to facilitate the proposed investigation, all field observations, measurements, and experimental treatments were confined to Building No. 1, specifically to the cast-stone

panels and joints located along the 19th floor level and above.

The report describes in some detail the progress of the study and

includes a statement of plans for future study.

2. WATERPROOFING TREATMENT OF THE

CAST- STONE AND JOINTS

- In the early part of May 195k9 a decision was made by representatives

of the District Public Works Office of the Potomac River Naval Command,

the Bureau of Medicine and Surgery, and the National Bureau of Standards

to have Building No. 1 at the Medical Center waterproofed from the 19th

floor level to the top of the building. The treatment was to include

cleaning, grouting and re-pointing of the joints between the cast-stone

panels (joints containing sound mortar were not to be re-pointed). In

addition, all exposed exterior surfaces were to be treated with one coat

of silicone water repellent. A specification was proposed by this Bureau

and finally written by the District Public Works Officer of the Potomac

River Naval Command, as Navdocks Specification No. 1*3W45>(SF). The contract

(NOy 83739) was awarded to the U. S. Building, Cleaning, Renovating and

Maintenance Company of Washington, D. C. The work was started on August 18

and completed on September 30, 193>U«

2.1 Condition of joints and panels

before treatment

Examination of the masonry at the 19th floor level before the treatment was applied revealed that practically every vertical joint contained

cracks. These cracks occurring primarily at the sides of the joints
-2 -

varied in width from hairline to as ranch as one tenth of an inchj the

latter occurring in some corners * Some of the cracks extended upwards

continuously to the top of the building, while others only intermittentlyo

There were a few instances of loose mortar in the vertical joints, the

worst cases occurring in the corners* Many of the horizontal joints

appeared in good condition up to the 10 ft* level* It was difficult to

estimate the condition of the joints above this height* The cast-stone

panels appeared to be in excellent condition with the exception of a few hairline cracks barely visible to the naked eye*

2*2 Field tests of silicone waterproofing

Three inconspicuous panels on the power plant building were selected

for the testing of three samples of silicone waterproofing* The samples

were? (1) Dow-Corning 129G resin, $ percent in xylene $ (2) General

Electric, SR5>3 resin, 5 percent in xylene | (3) Linde Air Products C2J? resin, k percent in mineral spirits* The three solutions were applied

with a brush to the three panels, respectively, and were observed for

water repellency and possible staining effect* All three types of treatments caused no discoloration and produced water repellent surfaces.

2*3 Preparation of the joints

for treatment by contractor

The contractor started the job by brushing the joints clean of dirt

and dust which was followed by the application of 1 1/2 in. of masking

tape to both sides of all joints. The joints were then sandblasted to

remove old calking compound and dirt from the surface and sides of the

joints, and at the same time exposing the faces of cracks between the

panels and the mortar (see figure 1-A)«

2oh Re-pointing and grouting of joints

All loose mortar joints were raked out and filled with a mortar

containing one part of white portland cement to 3 parts of silica sand,

by volume, followed by tooling to a smooth concave surface* All other

joints were grouted with a mixture containing equal parts of white

Portland cement and silica sand, by volume* The grout was applied in

the form of a heavy cream using a special grouting brush (see figure 1-B).

The fine cracks in some of the cast-stone panels were also grouted.

2*5 Application of silicone solution

The silicone water repellent used by the contractor was "Sta-Bri"

(5 percent Dow- Corning resin 129G in Xylene), manufactured by the

Sta-Dri Corporation, Brentwood, Maryland* Ten days after the grouting

and pointing job was finished, the silicone solution was applied with

a power spraying machine* The masonry retained a slightly yellowish
- 3-

appearance for several days after treatment, but it subsequently faded

to the natural appearance of the stone®

2.6 Effects of the -waterproofing treatment

Figures 2-A,B illustrates a typical vertical joint before and after

treatment. The photograph 2B was taken four days after the contractor

completed the job. Also at this time a few panels were tested for water

repellency by spraying with a stream of water® The east-stone appeared

to be highly water repellent.

No further inspections were made until November 5 when fine cracks

were noticed in many of the vertical joints on all four sides of the

building at the 19th floor level. (For results of a later inspect! on, see chapter 7)«

3. LABORATORY STUDIES OF CAST-STONE

In view of the fact that no test data on the physical properties

of the cast-stone used at the Medical Center have ever been made available, it seemed advisable to include such tests in this investigation.

For this purpose, a small sample of cast-stone, originally used in a panel in one of the buildings at the Center (apparently the only sample

available), was acquired from Mr. R. Corbin of the Maintenance Office.

This sample was used for the sbicfy- of thermal and moisture expansion and

water absorption properties.

3®1 Thermal expansion test

3.1.1 Test procedure

Measurements of linear thermal expansion were made by means of the

bonded wire resistance strain gage. Information on the development and

descripticn of the wire s train gage are given by Ramberg i/and NBS

Circular 528 [2] .

A specimen of cast-stone and one of fused quartz were cut to the

shape of a rectangular prism, 1 1/2 by 1/2 by 1/8 in. and both dried

in an oven at 160®F ± 2

° for four days® (Material of known thermal

expansion, such as fused quartz is used as a reference sample along

with the sample under test). Two SRli (type A-11 ) strain gages connected

in series, were attached with epoxy resin cement to opposite sides of

each specimen, and the entire assembly placed in an oven at l60°F ± 2

° for three hours, for curing of the cementing material (see figure 3).

After waterproofing and binding with black cellulose tape, the specimens

were placed in a thermal chamber in which the temperature could be varied

from -li® to +liiO®F. (Far detailed description of thermal chamber see Hockman and Kessler [3] ® During the test, temperatures were measured

1/

Figures in brackets indicate the literature references at the end of

the report.
-u- by a three junction thermocouple located close to the test specimen,,

A Baldwin strain indicator (figure 1H3) recorded the linear changes

directly in microinches per inch,

3,1.2 Test results

Figure 5 shows the thermal expansion curve obtained on the specimen

of cast-stone when heated ftom -h to +lh0®F (-20 to +60 deg C). The coefficient of linear thermal expansion was calculated to be 6.2 x 10"^

per deg F, or 11.1 x 10"° per deg C, for this temperature range. Both

the amount of the expansion and the regularity and shape of the curve appear to be within the normal range. for cast-stone of this particular

composition. On cooling, the specimen returned to its original length

showing no tendency for residual or "permanent” expansion.

3.1.3 Comparative expansion data for

stone used as facing material

For comparison purposes, linear thermal expansion coefficients for

a few common building stones generally used as facing material in structures are given in Table 1.

Table 1. Thermal expansion values far common building stones

Material Source

Mean coefficient of linear

thermal expansion F X 10"°

-U to +ll*0®F

Limestone Alabama 0.6?

Limestone Indiana 1.9

Marble Tennessee 1.7

Marble Georgia 2.2

Marble Vermont hck

Granite Various

)

sources)

3.U average

Sandstone Ohio 5.2

3.2 Moisture expansion test

3.2.1 Test procedure, non-waterproofed sample

Measurements of moisture expansion were made with a modified bonded

wire resistance strain gage developed by Valore £2) at the National

Bureau of Standards for measurements of internal strain in concrete.

A rectangular specimen, 2 1/2 by 1 l/k by 1 l/k in. was cut from

the original piece of cast-stone received from the maintenance office
-5-

of the Center and was dried at 220®F ± 2®F for 2h hours and cooled in a desiccator

.

The gage (modified SR-i** type A-ll) was then cemented with epoxy

resin cement to one long face of the specimen* and the assembly heated

for k hours at l60°F ± 2°. The specimen and gage* after cooling to room

temperature in a desiccator* was placed in a small tank and water was poured into the tank until the level reached the top of the specimen,,

Movement of the castes tone resulting from absorption of water was measured by a Baldwin strain indicator similar to the one used for the

thermal expansion test. (See figure 1*).

Expansion and contraction readings were taken over a period of

38 days in a room maintained at constant temperature ± 2®F. At the

end of the 19th day the water was removed and the specimen allowed to

dry while readings were continued,. On the 36th day* the specimen was placed in an oven at 160®F ± 2® for 1*8 hours and a final reading taken on the 38th day.

3o2o2 Test procedure,, waterproofed sample

The specimen used for moisture expansion study was dried for four

days at 160®F ± 2® and after cooling* given a liberal brush coating of

9 percent Dow Corning silicone resin in xylene. After the coating had

dried for two days the specimen was tested for moisture expansion.

3«2.3 Test results

Figure 6 gives the moisture expansion and contraction curves for

a sample of cast-stone originally used at the Naval Medical Center.

After 19 days immersion in distilled water at constant temperature

(75°F ±2°) the specimen expanded 385 microinches per in. or 0.0385

percent. The expansion curve rises sharply at the start of the test*

attaining 15 percent of the total expansion after one hour and 66 percent after 2h hr. immersion. When the water was removed and the specimen allowed to dry* contraction proceeded at a comparatively slow rate.

After 17 days of drying at room temperature* the specimen contracted

to 50 percent of the amount it expanded when immersed. A heating of

the specimen at l60°F for two days brought it back abruptly to its

original length.

Figure 6, lower portion* shows the moisture expansion curve (dashed lines) of the waterproofed specimen of cast-stone. After 19

days of immersion* the sample expanded 115 microinches per in. or 0.0115 percent. Unlike that of the non-waterproofed specimen* the

curve rises slowly and the expansion proceeds at a fairly uniform

rate. Waterproofing of the cast-stone reduced the moisture expansion

obtained on the non-waterproofed specimen by 92 percent for 2k hr.

immersion and 70 percent for 19 days immersion.
3.3 Absorption test

3.3.1 Test procedure

Two specimens* weighing approximately 9k and 162 grams* respectively*

were cut from the original piece of cast-stone obtained from the Medical

Center. The specimens were dried for 2k hours at 220*F ± 2° and cooled

in a desiccator until reacty

- for test. After obtaining the dry weights to

the nearest hundredth of a gram, the specimens were immersed in a pan of

distilled water for U8 hours at room temperature. During immersion

weighings were made at hourly intervals up to 6 hours followed by weighings at one and two days.

3.3.2 Test results

Figure 7 gives the absorption curve for total immersion of caststone in a U8 hr. period. The absorption value for U8 hours was 5*8

percent by weight. The curve rises sharply at the start of the test*

attaining 75 percent of the total absorption after 1 hour and 98 percent

after 6 hours. This behavior is characteristic of the natural building

stones such as granite* limestone* marble and sandstone.

3. 3-3 Comparative moisture expansion and absorption

data for stone used as facing material

For comparison purposes* moisture expansion and absorption values

for some building stones used as facing material in structures are given

in table 2.

Table 2

Table 2. Moisture expansion and absorption values for common building stones

Material Source

Moisture expansion

2U-hr. immersion

(average values)

%

Absorption

Ii8-hr. immersion

(average values)

% by weight

Limestone Alabama 0.0032 5.6

Limestone Indiana .0028 5.3

Limestone Texas .0015 6.3

Marble Alabama .0010 0.1

Marble Georgia . 0025 0.1

Marble Vermont .0010 o.l

Granite Various sources .0039 0.2

Sandstone Amherst, Ohio .013 6.0

Sandstone Glenmont* Ohio .010 7.3

Sandstone McDermott* Ohio .oiUi 6.2
- 7-

ho LABORATORY STUDIES OF PLASTIC CALKING MATERIALS

The use of plastic calking compounds as a joint sealer in masonry

structures has been widely recognized by architects and engineers. The

compounds serve as fillers for expansion joints* as waterproof sealers

in the spaces between window and door frames* as pointing, material in

the joints of copings* sills* cornices* etc.* and in most any joint

where some movement is expected and water- tightness is required.

The compositions of the compounds are variable* the most typical

consisting of treated drying and/or semi-drying oils* reduced to a plastic condition with inert fillers* plus some asbestos fiber and

coloring matter. In addition many compounds contain some volatile

solvent and chemical drier to aid in the formation of a protective

"skin" after installation. Some manufacturers use synthetic resins

with or without the oils. A few formulas include synthetic rubber bases.

The outstanding requirements for a good calking material are adhesiveness* plasticity and durability. Requirements of somewhat lesser

importance are color permanence* possession of a non-staining vehicle*

and ease of application.

In view of the fact that the installation of some type of plastic

calking material might be necessary to prevent the leakage through the

joints of the cast-stone at the Medical Center* it seemed advisable to

include in this investigation a laboratory study of such materials that

are presently available. For this purpose 5>0 samples have been acquired

by purchase ftom retail stores and by donations from manufacturers. The

samples cover practically all types of compounds that are being manu- factured at the present time.

The following sections describe some of the laboratory tests which

are now in progress. The data accumulated from the results of these

tests will aid in the selection of the most promising material to be

used as the joint filler. Many of these tests are described in detail

in Federal Specification TT-C-^98* while others are being designed for

the particular requirements of this investigation.

Iwl Description of tests

kolol Fabrication of the cast-stone blocks

Since an accessory porous material is necessary with which to test

the calking compounds* six hundred blocks of suitable sizes were fabricated (to date) using the same type of materials and mix design (cement,

sand and gravel) as that used for the fabrication of the cast-stone

panels at the Medical Center.
-8-

U.1.2 Rate of Hardening

This is determined with a Penetrometer on a joint between cast-stone

slabs spaced 3/8 in., filled with the plastic to a depth of 1 l/k in. and

length of 3 1/2 in* The depth to which a standard needle penetrates ihe

material in 5 sec is recorded before and after curing for 15> days at room

temperature. The rate of hardening is computed from the formulas

(P-, “ Po) ioo

h £

P1

in which h is the rate of hardening, and and ?2 are the averages of

the original and final penetrations, respectively. (See figure 9)®

1|.1.3 Shrinkage

This property is determined by means of a brass ring 2 5/8 in. in

diameter and 1/2 in. high (volume, V, known to .01 ml), a ground glass cover plate and a slab of cast-stone, 3 1/2 by 3 1/2 by 1 in. (see

figure 8-C,D). After the combined weight of the ring, slab and cover plate is determined, the ring is centered on the slab, 1/8 in. layer

of compound is spread inside the ring, in firm contact with the stone

and a weight determined (¥2

). The ring is then filled over the calking

with distilled water and a third weight determined (W

3

). Since the

volume of 1 gram of water is approximately 1 ml, the volume of the

layer of calking, Vc

= V-(Wo - W2). The water is then poured off and

the sample exposed at room temperature for 15 days, after which Wg' and

corresponding to ¥^ and are determined. The final shrinkage is

calculated as follows?

Sh = (W3' V) fa w

2

) V

x 100

Uol.U Tenacity

After the brass ring is removed from the shrinkage test specimen,

half of the calking layer is loosened from the stone and is folded over the remaining part and creased six times along the same line (see

figure 8-E). Embrittlement or lack of tenacity can be observed. This

test is also being made at below freezing temperatures.

U.1.5 Consistency

A metal trough U in. long, 1 in. deep and 3/8 in. wide is filled

with the compound and suspended for 2k hours at room temperature,

followed by a similar test at 122°F (figure 8-B). The material is

observed for flow tendencies. Slump tests are also being made in caststone grooves.
-9-

1|.1.6 Bond and plasticity at room temperature

The joint tested is made between two slabs of cast-stone, 6 by 7

by 1 in., one of which has a 2 1/2 in. round hole. Calking is placed

between slabs which are held apart by a l/h in. brass spacer, making a joint l/U in. thick and 3/h in. deep on all four sides of the stone.

(Figure 10). After 30 days of curing at room temperature, the slabs are drawn apart by a special apparatus (figure 10), the amount of separation

being measured by a 0.001 in. micrometer dial gage. At the start of the

test, water is poured into the hole of the top block and the joint is

watched for leakage as the blocks are drawn apart. Figure 10, right,

shows a compound after test in which premature failure was caused by lack

of bond.

h.1.7 Test at low temperature

The apparatus used to make this test is described in Federal

Specification SS-R-U06c, No. 223.11, for testing asphalt joint sealers.

Two cast-stone blocks, forming a joint 2x2x 3/8 in. is filled with

calking and allowed to cure for 30 days at room temperature. After the

test specimen is placed in a cold box for at least h hours, it is

clamped into place in the stretching machine, and the blocks drawn apart

at the rate of 1/8 in. per hour until the joint is extended 1/10 in.

(figure 11). During the test the temperature is maintained at 0°F.

Observations are made of the bond and plasticity properties.

U.1.8 Exposure studies

All samples of the calking materials are being esposed in caststone joints on the roof of the Industrial Building at the National

Bureau of Standards. Periodic examinations are being made for changes

in plasticity, adhesion, etc. Many of the tests described will be

duplicated on test specimens that have been exposed to natural weather

conditions.

5. MEASUREMENT OF JOINT MOVEMENTS

The 19th floor level of Building No. 1 of the Medical Center was selected far measuring joint movements resulting from the expansion

and contraction of the cast-stone panels. This location seemed to be

ideal for making measurements and observations because of its accessibility and the fact that leakage had occurred many times at this floor

level. It was decided to use the Whittemore 5 in. strain gage to measure

the movements of 16 vertical joints located on the northeast, northwest,

southeast and southwest elevations.

5.1 Description of the strain gage

The Whittemore Strain Gage jU] is a precision mechanical gage which

measures changes in length over a specified gage length (5 in. in this
-10-

case) with a 0*0001 in. micrometer dial gage. The frame of the improved

gage consists of two coaxial tubes (the innertube made of invar), con- nected near the ends by fulcrum plates of thin spring steel which constrain

the tubes to move axially. A point is rigidly attached to one end of

each tube. When the points are seated in small holes in the material to

be measured the position of one tube with respect to the other is indicated on the micrometer dial clamped in the inner tube. Figure 12 shows

the gage, standard bar and double pointed punch for spotting holes.

£.2 Installation of gage stations

Figures 13 and 111 give the exact locations of the gage stations

installed in the cast^stone panels on the northeast, northwest, se ^nd S|W

elevations. At the start of the investigation, six stations were installed

at each elevation in such manner that each station straddled a vertical

joint at the U 1/2 ft. level. Stations Nos. 1 and 6 were installed for

measurement of panel movements in corners. After many unsuccessful

attempts were made to obtain dependable and accurate measurements of the corner joint movements, it was decided to abandon the corner stations

and restrict the measurements to stations 2, 3, U, and 5, on all four

sides of the building.

Figures l£-A to F show the operations that were required to install

a gage station. The finished station consisted of two cylindrical stainless steel plugs, 1/h in. in diameter and 1/2 in. long, set into the

cast-stone panels with high-early-strength cement, approximately 2 l/2 in. on each side of the vertical joint at about the U 1/2 ft. level. Holes,

1.2 mm in diameter, were drilled into the plugs to accommodate the points

of the gage. Figure 15>-G shows a finished gage station and figure IJp-H

illustrates an operator making a measurement.

5.3 Frequency of measurements

Measurements of joint movements at the 16 gage stations were started

on September 9, 195U, and continued until April 27, During this

period of 7 1/2 months, gage readings were taken on fifteen separate

occasions. Attempts were made to include measurements on very hot and

cold days. Such readings were taken on September 29 and January 31,

respectively.

The first set of measurements, made on September 9 were recorded

as ’’zero" readings. All subsequent readings that were numerically higher

than the ’kero” readings were called "plus", and indicated that the mortar

joint expanded relative to its position at the "zero” reading. Readings

that were numerically less than the "zero" reading were "minus’1 and

indicated that the mortar joint contracted, relative to its position at

the zero reading.

2/ All measurements except the first two were made after the joints were waterproofed.
-11 -

5.1* Results of measurements of joint movements

Figure 16 and table 3 give the complete record of joint movements

as measured at all 16 gage stations on 15 separate occasions from

September 9 to April 27, 1955* In general, the joint movements were directly related to tie changes in temperature® A rise in temperature

caused the cast-stone panels to expand which resulted in a closing or contraction of the joints® This is illustrated by the September 29

readings, when the temperature rose to 90®F and the joints contracted

in most instances (cast-stone panels expanded)® Similarly, a drop in

temperature to 39°F on December 1*, 195U, caused most of the joints to

open or expand (cast-stone panels contracted)® Figure 1? shows the

correlation between the joint movements and the air temperature

recorded at the time of gage readings®

It is probable that joint movements resulting fhom wetting and

drying of the cast-stone, caused by rains, were reduced to a minimum

on account of the water-repellent surfaces of the cast-stone® However,

it is also probable that movements of the cast-stone panels may have

been affected by changing relative humidities - a problem which will be

investigated at a later date®

Table 3 gives the maximum expansions and contractions of joints 2,

3, 1*, and 5, on all four sides of the building, recorded from September 9,

195U, to April 27, 1955* During this period, the greatest change in

temperature observed when measurements were made, was 61* F deg® (Weather

Bureau records show a maximum change of 89 F deg® ) The total movement in

anyone joint ranged from a minimum of 0.0021* in. (1.0 percent of its

Initial width) as in joint No® 1*, southwest, to a maximum of 0.0115 in.

(1*®6 percent) in joint No® 2, southeast. The average movement for all

16 joints was 0.0066 in. or 2.6 percent® The joints on the southwest

side averaged the smallest movement, 0.001*3 in., and the southeast side

averaged the largest, 0.0083 inches®

6® RELATION OF LABORATORY TESTS TO FIELD

STUDIES OF JOINT M) CEMENTS

The results obtained from the field measurements of the joint movements indicate that the average movement over the 7 1/2 month period,

September 9, 1951* to April 27, 1955, was considerably less than what

might have been expected if judged by laboratory tests alone® Laboratory

studies (Chapter 3) indicate that the cast-stone expands 6.2 x 10"° in.

per deg F due to heating, and 0.0385 percent due to wetting. For a 61* degree change in temperature (the maximum observed) a 5 foot cast-stone

panel is capable of expanding as follows

;

6® 2 x 10“^ x 61*° x 60 in® = 0.0238 inches
-12-

As suming that a. 5 ft panel is saturated with water the expansion

would be?

0,000385 x 60 in, or 0,0231 Inches

Therefore* the total linear expansion of a 5 ft cast-stone panel due to

heating and wetting is?

0,0238 + 0,0231 = 0.01*69 inches

Actual measurements on the building have shown that the maximum

movement observed for all joints (or panels) averaged 0,0066 inches,

or 1U.1 percent of the maximum theoretical expansion indicated bylaboratory studies.

Three factors might have contributed to the apparent discrepancyin the -values of joint movements?

(1) It is very unlikely that the cast-stone panels heated or cooled throughout their entire volume, to ihe air temperature recorded

at the time of measurement,

(2) Expansion due to absorption of water after heavy rains was

probably reduced considerably because of the silicone waterproofing

treatment,

(3) It is extremely unlikely that both moisture and temperature

conditions coincide in such a manner as to produce maximum and minimum

joint widths.

7, PRESENT CONDITION OF MORTAR JOINTS

On April 22, 1955s a visual examination was made of the vertical

joints on the four sides of Building No, 1 at the 19th floor level,

Wherever cracks were found, measurements of their width were made with

a set of feeler gages. Table h gives the results of these measurements.

Although the authors have been informed by a representative of the

maintenance department of the Medical Center that there has been no

leakage of any consequence subsequent to the application of the waterproofing treatment, measurements made with the Whittemore gage indicated

joint movements, which averaged 0,0066 in, for all four sides of the

building, excluding the corner joints (chapter 5)» Figure 18-A illustrates a corner joint (southeast) as it appeared the day before the

waterproofing treatment was applied and figure 18-B shows the same corner as it appeared on April 22 approximately 7 months after the

treatment.
-13-

The results of the examination of the joints made on April 22

corroborated to some extent the results obtained with the Whittemore

strain gage® As shown in Table U joint cracks ranged in width from hairline (less than OoOOl in® ) to a maximum of l/l6 in. - the latter in corner joint No® 6 on the southwest side® Except for the hairline cracks and

the one large crack (l/l6 in®)* the average of the openings in the rest

of the joints was 0®006 in® This latter figure is practically the same

as the average movement of 0o 0066 in® obtained with the Whittemore strain

gage® However, this similarity appears to be only a coincidence since

measurement of cracks on the northeast side made on April 22 revealed

no opening greater than hairline (Table 10* whereas* previous strain

gage measurements of these same joints showed an average movement of

OoOOTi inches® Similarly* joints No® 2 to 5 on the northwest side had

average cracks of less than 0®001 in® on April 22* whereas strain gage

measurements revealed movements averaging 0®006£ in® for the same joints®

Although cracks of various sizes are prevalent on all four sides of

Building No® 1, 19th floor levels as indicated by inspection on April 22*

they seem to be of insufficient size and number to allow leakage through

the walls® It appears that the waterproofing treatment was instrumental

in stopping the leakage that had occurred before the treatment was applied®

It might be noted here* that during the inspection of the joints on April 22* the senior author could* in many instances and with little

effort* flake off* by means of a small knife blade, the thin coating of

mortar from the side of a joint* and by so doing* reveal a crack that

most likely existed before the grouting was applied® This indicates

that, in many instances the cement grout did not penetrate into the

opening of the joint* and was merely functioning as a thin shell-like

coating over the existing crack®

The question still remains whether the walls of the Building No® 1

at the 19th floor level will be free from leakage for any reasonable

length of time® If the cracks continue to increase in size and number

due to continued movements of the panels or to the flaking off of thin

layers of the cement coating* it is doubtful whether the mortar grout

applied in the waterproofing treatment will continue to stop the leakage

through the joints®

8® PLANS FOR FUTURE STUDY

1® The method of measuring the joint movements will be changed

with the hope of obtaining more accurate data® The Brinell microscope*

reading directly in hundredths of millimeters will replace the Whittemore

strain gage® Figure 19 illustrates the microscope and the type of gage

station that will be installed for its use® Joint movements will be

measured at more frequent intervals and especially after long periods

of extreme hot and cold weather®
2. The study of the properties of the -various types of calking

compounds and joint fillers mil be continued until completion. Exposure

tests under natural weather conditions will be made for all s amples . If

possible accelerated weathering tests will be made.

3. A study will be made of the effects of various relative humidities

on the expansion properties of cast-stone.

U. Several types of silicone waterproofing formulas will be studied

for effectiveness and durability.

9. SUMMARY

1. The NBS has started an investigation to determine the causes

and possible control of leakage of rain through the walls of some of

the buildings at the National Naval Medical Center, Bethesda, Maryland.

All field studies were confined to the 19th floor level of Building No. 1.

2. An experimental waterproofing treatment as applied to 19th floor

level and above is described. The treatment consisted of sandblasting of

the joints followed by repointing of joints containing unsound mortar,

and a grouting of all joints with cement, sand, water mixture of a cream

consistency. The cast-stone panels and joints were finally given a spray

coating of water-repellent solution ( 5% solution of silicone resin in

xylene).

3. Laboratory studies were made on samples of the original caststone used at the medical center, and included tests for thermal and

moisture expansion and absorption. The linear thermal expansion coefficient was 6.2 x 10"° per deg F. for the range -U to +lU0*, F (11.1 x

10"° per deg C, -20 to +60°C). The moisture expansion value for a 19 day immersion period at constant temperature was 0.038£$. This value

was reduced by 70% for the same immersion period by waterproofing with

silicone water-repellent. The absorption value was £.78$ by weight, for

a Ij.8 hour immersion period. Curves illustrating the expansion properties

are given. For comparison, thermal and moisture expansion and absorption

values are given for typical natural building stones.

U. Tests for evaluating the properties of plastic calking compounds

are described in some detail. Fifty samples of almost every type of

calking available are being tested far shrinkage, plasticity, bond,

tenacity, rate of hardening, etc. The materials are being tested at

various temperatures and compounds showing promise will be exposed to

natural weather conditions far durability studies.

A series of measurements of joint movements resulting from the

expansion and contraction of the cast-stone panels was completed. Joint
-15-

movements were measured with a 5 inch Whittemore strain gage, on U sides

of the Building No. 1, 19th floor level, from September 99 19$k to April 27,

1955o During this period readings were taken on a total of 16 vertical

joints on 15 separate occasions. The maximum change in temperature observed for this period was 61| fahrenheit degrees . The average movement

for all 16 joints was 0.0066 inches or 2.6$ of the original l/k in. jointo

The total movement in any one joint ranged from a minimum of 0o 002U inches

to a maximum of 0o 01l5 inches, the latter occurring on the southeast

elevation,, In general, the joint movements were directly related to the

changes in temperature, ies a rise in temperature caused the cast-stone

panels to expand resulting in a closing or contraction of the joints,,

Similarly, a fall in temperature caused a reverse movement.

6. Results obtained from the field measurements of joint movements

were considerably less than what might have been expected if judged by

laboratory tests of the cast-stone. Three factors might contribute to

this apparent discrepancy? (1) It is improbable that the cast- stone

paiels heated or cooled throughout their entire volume, to the air temperatures recorded at time of measurement^ (2) Expansion, due to absorption of water after heavy rains was probably reduced considerably by the

silicone treatment! (3) It is improbable that both moisture and temperature conditions were simultaneously such as to produce maximum joint

movements

.

7. An inspection of the joints at the 19th floor level made 7 1/2

months after the waterproofing treatment was applied, revealed the

existence of cracks in 8

0

% of the joints examined. The cracks ranged

in width from hairline (less than 0.001 inches) to a 1/1.6 inch, the

latter in a corner joint on the southwest side. The average of the

openings in the joints was estimated to be 0.006 inches, excluding the

hairline and the l/l6 inch cracks.

No leakage has been reported on the 19th floor level of Building No.l

since the waterproofing treatment has been applied. If the cracks continue to increase in size and number, due to the continued movements of

the panels or to the flaking off of thin layers of the mortar grout, it

is doubtful whether the grout applied in the waterproofing treatment

will continue to be effective in controlling leakage through the joints.
-16-

Table 3* Maximum movements of joints* 19th floor level. Building No. 1, as recorded from Septenber 9, 195U to April 27, 19tt

Northeast Joint Movements*

Joint No.

Maximum

Contraction

10“4 in.

Maximum

Expansion

Total

Movement

10*4 in. 10**4 in.

2 -Ik +91 10$ It. 2

3 - 2 +55 57 2.3

k -22 +58 80 3.2

5 - k +38 k2 1.7

Avg. 71 2.8

Northwest

2 -36 +U6 82 3.3

3 -30 +13 U3 1.7

k -30 +25 25 1.0

5 0 +109 109 U.ii

Avg. 65 2.6

Southeast

2 -55 +60 115 U.6

3 -32 +60 92 3.7

k -13 +35 U8 1.9

5 -31 +U5 76 3.0

Avg. U 3.3

Southwest

2 -hh +29 73 2.9

3 -22 +13 35 i.a

k -23 + 1 2U 0.96

5 -35 + 6 la 1.6

Avg. k3 1.7

Grand Avg. 66 2.6

#Minus quantities indicate closing of joints as compared with “zero**

readings on Sept. 9, 195U. Plus quantities indicate opening of

joints relative to "zero" readings.

#*Percentages based on one quarter inch joints.
-17“

Table Condition of vertical joints, on four elevations, 19th floor

level. Building No 0 1, April 22, 1955-

Northeast Condition of Joints

Joint No, 1

2

3

k

5

6

Very few hairline cracks, 1st course and extending

intermittently to top of building

" 11 8} M in 1st course only

No crack visible

ttn Very few hairline cracks extending intermittently to top

Northwest

1

2

3

h

Cracks, ,01 in, 1st course extending intermittently to top

Few hairline cracks, 1st course only

No cracks

n 5

6

Cracks, <,002 ±n0 1st course extending intermittently to top

Wide cracks, .015 in." 81 ” u "

Southeast

l Cracks, 0 OOI4

. in. 1st course extending intermittently to top

2 « . 006 " ti ii it tt tl 3 . 003 » it « ii ii II

1; " hairline it it ii it II 5

« .01 « it it ii ti tt 6 " .01 » n it it ti II

Southwest

1 Cracks, ,002 in. 1st course extending intermittently to top

2 “ .002 «* ti n n ii II 3

" . 001 »' a ti 81 81 tl h Wide cracks, «0l5it ii it II II tt 5 Cracks, .005" ti it It tt II 6 Wide cracks,l/l6't ti n

, extends, but narrows towards top

^Estimates of width of cracks apply to only the first course (10 feet).

The condition of the joints above this level were judged with the aid

of a pair of 3 power binoculars

»
-18-

10. REFERENCES

1. W. Ramberg, Contributions of Electricity to Mechanics, J.

Washington Acadeny of Sciences, Vol. 39, 281 (19U9).

2. Characteristics and Applications of Resistance Strain Gages,

National Bureau of Standards Circular 528 (1951).

3. A. Hockman and D. W. Kessler, Thermal and Moisture Expansion

Studies of Some Domestic Granites, J. Research, NBS, Vol. Uli, 395s

R.P. 2087 (1950).

U. H. L. Whittemore, The Whittemore Strain Gage, Instruments,

Vol. 1, No. 6, p. 299, (1928).
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TEMPERATURE, °C

5 THERMAL EXPANSION CURVE OF SAMPLE OF CAST

STONE USED AT THE NAVAL MEDICAL CENTER.

EXPANSION,

MILLIONTHS

19 18 17 15 13 II 9 7 5 3

DRYING IN AIR, DAYS

o

FIGURE NO. 6 MOISTURE EXPANSION AND CONTRACTION CURVES (75°F)

OF CAST STONE USED AT THE NAVAL MEDICAL CENTER.

ABSORPTION

-

PERCENT

BY

WEIGHT

FIGURE NO. 7 WATER ABSORPTION CURVE OF SAMPLE OF CAST

STONE USED AT THE NAVAL MEDICAL CENTER.

8 .

'Pig. 8. Calking test specimens

(A) Test specimens used for plasticity and bond studies

at -cold temperatures, (B) consistency test specimens,

(C,d) shrinkage test specimens, (E) tenacity test specimen..

Fig. 9. Rate of hardening test of calking materials

' A ) Cast-stone specimen before filling joint, ready for test with penetrometer, (C) calking joints ready for exposure test.

(B) calking

in cast-stone

a

®

+3 ! ~ Pr ^

40 (D -P

H

4^ «h® -P rtaj

ra id ^ Cl oDO

®)J

O ®*rl

40 <hO KVio &

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Fig. 12* Whittemore strain gag© and accessories

Top, double pointed punch to spot holes on 5>-in. span.

Center, measuring instrument with dial.

Bottom, standard bar for correction of reading.

—

1

J

FIGURE NO. 13 PLAN VIEW SHOWING LOCATION OF ALL GAGE STATIONS

USED IN MEASUREMENT OF JOINT MOVEMENTS.

(19TM FLOOR LEVEL, BUILDING NO. I, NAVAL MEDICAL

CENTER.)

FIGURE

NO.

14

TYPICAL

WALL

ELEVATION

SHOWING

LOCATION

OF

ONE

SET

OF

GAGE

STATIONS

USED

IN

MEASUREMENT

OF

JOINT

MOVEMENTS.

(19TM

FLOOR

LEVEL,

BUILDING

NO.

I

,

NAVAL

MEDICAL

CENTER.)

Pig. 15. Series of photographs showing operations necessary

"TaT^

s ^ a^i a^i°n gage stations.

holes in cast-stone.

JB) Wetting the holes for placing of mortar.

vC) “lacing of the mortar.

(D) Insertion of the 1/If. in. dia steel plugs.

Fig. 15. (continued)

(E) Spotting holes with double pointed punch.

(F) Drilling 1.2 mm holes in steel gage plugs.

(G-) Completed gage station.

(H) Operator taking readings with strain gage.

JOINT

MOVEMENTS,

lO

" 4

IN,

TEMPERATURE,

DATE READINGS TAKEN DATE READINGS TAKEN DATE READINGS TAKEN DATE READINGS TAKEN

Fig. 16. Complete record of joint movements measured at

16 gage stations on Ij. elevations. (19th floor

level. Building No* 1, Naval Medical Center)*

Corresponding air temperatures for each date

that readings were taken are plotted along the

top of the graph.

JOINT

MOVEMENTS

*

I0'

4

INCHES

AIR TEMPERATURES, °F

FIGURE NO. 17 RELATIONSHIP BETWEEN JOINT MOVEMENTS AND AIR

TEMPERATURES RECORDED AT THE TIME GAGE READINGS

WERE TAKEN. EACH POINT REPRESENTS THE AVERAGE

DATA OBTAINED ON EACH OF THE 15 DAYS THAT

MEASUREMENTS WERE MADE FROM SEP'T. '54 THROUGH

APRIL '55. (I9IH FLOOR LEVEL, BUILDING NO. I

,

NAVAL MEDICAL CENTER.)

Fig.

18.

Illustration

of

a

corner

vertical

joint

on

the

southeast

side,

(19th

floor.

Building

No.

1).

(A)

Just

before

waterproofing

treatment.

(B)

as

it

appeared

7

months

after

treatment.

V Si *;/; - >

• - T

. 1 .

/ ,>

'

' ['-i.

-

' siit|

• :

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i

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, mm

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' \ ' , . '.

. a

:r <

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19.

(A)

Type

of

gage

station,

(rectangular

stainless

steel

strips),

being

used

at

the

present

time

for

measurement

of

joint

movements.

(B)

Operator

measuring

the

distance

between

steel

strips

with

a

Brinell

microscope.

THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods

for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials,

devices, and structures; advisory services to Government Agencies on scientific and technical

problems; invention and development of devices to serve special needs of the Government; and the

development of standard practices, codes, and specifications. The work includes basic and applied

research, development, engineering, instrumentation, testing, evaluation, calibration services, and

various consultation and information services. A major portion of the Bureau’s work is performed

for other Government Agencies, particularly the Department of Defense and the Atomic Energy

Commission. The scope of activities is suggested by the listing of divisions and sections on the

inside of the front cover.

Reports and Publications

The results of the Bureau’s work take the form of either actual equipment and devices or published papers and reports. Reports are issued to the sponsoring agency of a particular project

or program. Published papers appear either in the Bureau’s own series of publications or in the

journals of professional and scientific societies. The Bureau itself publishes three monthly periodicals, available from the Government Printing Office: The Journal of Research, which presents

complete papers reporting technical investigations; the Technical News Bulletin, which presents

summary and preliminary reports on work in progress; and Basic Radio Propagation Predictions,

which provides data for determining the best frequencies to use for radio communications throughout

the world. There are also five series of nonperiodical publications: The Applied Mathematics

Series, Circulars, Handbooks, Building Materials and Structures Reports, and Miscellaneous

Publications.

Information on the Bureau’s publications can be found in NBS Circular 460, Publications of

the National Bureau of Standards ($1.25) and its Supplement ($0.75), available from the Superintendent of Documents, Government Printing Office. Inquiries regarding the Bureau’s reports and

publications should be addressed to the Office of Scientific Publications, National Bureau of

Standards, Washington 25, D. C.
NBS