Fire endurance tests on unit masonry walls with gypsum wallboard

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Fire endurance tests on unit masonry walls with gypsum wallboard

Allen, L. W.; Stanzak, W. W.; Galbreath, M.

NATIONAL RESEARCH COUNCIL OF CANADA DIVISION O F BUILDING RESEARCH

FIRE ENDURANCE TESTS ON UNIT MASONRY WALLS WITH GYPSUM WALLBOARD

b y

L. W. Allen, W. W. Stanzak and M. Galbreath

F i r e Study No. 3 2 of the

Division of Building R e s e a r c h

OTTAWA February 1974

FIRE ENDURANCE TESTS ON UNIT MASONRY WALLS WITH GYPSUM WALLBOARD

by

L. W. Allen, W. W. Stanzak and M. Galbreath

ABSTRACT

Standard f i r e endurance t e s t s , following the p r o c e d u r e s

d e s c r i b e d in ASTM E 11

9,

w e r e conducted on s i x concrete block walls with 3f _{8 in. and 1/2 in. thick gypsum wallboard finishes on one o r} both f a c e s . The r e s u l t s suggest that the f i r e endurance of 4 in. and

6

in. block walls can be doubled by the judicious u s e of gypsum wallboard protection. Two methods of estimating the contribution of gypsum wallboard t o the f i r e endurance of m a s o n r y walls with

ESSAIS D E RESISTANCE AU F E U E F F E C T U E S SUR DES MURS D E MAC ONNERIE REC OUVERTS D E PLAC OPLATRE

Par

L. W. Allen, W. W. Stanzak et M. Galbreath

RESUME

On a effectuk, conformkment la norme ASTM E 119, d e s e s s a i s standard d e r e s i s t a n c e au feu s u r s i x m u r s d e blocs de beton recouverts d e placopldtre d'une kpaisseur de 3/8 po. et d e 1/2 po. s u r une face ou s u r l e s d e u x f a c e s . Les resultats indiquent qu'on peut doubler la rksistance au feu d e s m u r s d e blocs de 4 po. et d e 6 po. en faisant un usage judicieux du placopldtre. On propose deux mkthodes servant

%

6valuer l e r61e du placopliitre dans l a rksistance au feu d e s m u r s de magonnerie avec un degr6 raisonnable de pr6cision.

FIRE ENDURANCE TESTS ON UNIT MASONRY WALLS WITH GYPSUM WALLBOARD

by

L. W. Allen>:<, W. W. Stanzak** and M. Galbreath':*)::

Gypsum wallboard in 3/8

-

o r 1 /2 -in. thickness i s often applied to unit m a s o n r y walls t o improve t h e i r acoustical p r o p e r t i e s and finished appearance. The finish h a s not, however, been incorporated in f i r e tested a s s e m b l i e s o r credited with improving the f i r e endurance of a m a s o n r y wall.

In Supplement No. 2, F i r e P e r f o r m a n c e Ratings 1965, of the National Building Code, a simple f o r m u l a was included t o p e r m i t the a s s e s s m e n t of the contribution of gypsum p l a s t e r t o the f i r e endurance of m a s o n r y walls. This formula was not applied t o gypsum wallboard because of the absence of t e s t information.

Accordingly, the F i r e R e s e a r c h Section of the Division of Building R e s e a r c h of the National R e s e a r c h Council of Canada designed a s e r i e s of f i r e r e s i s t a n c e t e s t s that a r e described in this r e p o r t . Six walls w e r e tested and sufficient information was obtained t o make recommendations f o r u s e in building standards.

DESCRIPTION O F TEST SPECIMENS

A general description of the various t e s t walls i s given in Table I.

Additional d e t a i l s on components of the different wall a s s e m b l i e s follow. A) Concrete m a s o n r y units: Walls w e r e constructed of either nominal 4- o r 6 -in. hollow o r solid concrete m a s o n r y units. Mix designs employed in the production of units w e r e a s follows:

4-in. hollow 4-in. solid 6-in. hollow

cement 400 lb 450 lb 480 lb

s and 2650 lb 3000 l b 3050 1.b

stone 1200 lb 1900 lb 1300 lb

.1.

-,. _{F o r m e r National Concrete p r o d u c e r s t Association Fellow;}

.'. .k

-,.

., _{F o r m e r Steel Industries Fellow; and}

::c $c ;:c R e s e a r c h Officer, F i r e R e s e a r c h Section, Division of Building

All units w e r e standard (low p r e s s u r e ) cured and taken from regular production r u n s of t h r e e block producers.

B) k' Wallboard: Standard laminated wallboard was used

(CSA 82. 27, 1963) in either 4- by 9-ft s h e e t s 3/8-in. thick o r in 4- by 10-ft sheets 1/2-in. thick. ~ c t u a . 1 m e a s u r e d thickness was 0. 35 and 0. 52 in. respectively.

C) Laminating Adhesive: Domtar 'Gypstikt type

N

panel adhesive

was used throughout. This m a t e r i a l i s classified a s extremely flammable and i s supplied in a standard s q u i r t can for n o r m a l gun application.

D) Joint Compound: Two types of joint compounds w e r e used

-

-

Domtar Gyproc premixed compound and Sheetrock r e a d y mixed joint c o m - pound a s manufactured by Canadian Gypsum Company. Both w e r e used t o fully imbed a 2-in. s t r i p of 'PERF-A-TAPEt joint tape applied t o joints of adjacent wallboard sheets.

E) Wood f u r r i n g s t r i p s : Nominal s i z e wood stripping, where used,

was 1 by 3 in. (actually 3/4 by 2 5/8 in. ).

F)

**Resilient Steel Channels: Size of resilient channels, where

used, was 2 1/8 by 1/2 i n . , 0. 021 in. thick.

G) **Steel Studs: Where used, s t e e l studs m e a s u r e d approximately

2 1/2 by 1 5/8 in. and w e r e 0. 019 in. thick.

The standard p l a s t e r stops w e r e either 1 by 9/16 by 0. 018 in. depending on the thickness of the wallboard used. Material was normally supplied in 10-ft lengths and was cut t o fit along the s i d e s and top of wall a s s e m b l i e s .

i-" Standard gypsum wallboard i s manufactured by s e v e r a l f i r m s in Canada. The individual products of each f i r m a r e sufficiently s i m i l a r to yield almost identical f i r e performance, i. e . , they generally r e m a i n in place f o r a v e r y s h o r t t i m e (thirty minutes o r l e s s ) . To improve the p e r f o r m a n c e , most m a n u f a c t u r e r s provide a v a r i e t y of "Type XI1 wallboards, whose ability t o r e m a i n in place during f i r e exposure is improved by c e r t a i n additives, in-

cluding g l a s s f i b r e reinforcement. No satisfactory t e s t (other than the standard

f i r e t e s t ) h a s been developed, however, to a s s e s s the quality of t h e s e s p e c i a l products. Use of standard wallboard in the p r e s e n t t e s t s eliminates the difficult m a t e r i a l identification problem involved with p r o p r i e t a r y products.

:::: Components F t o H a r e commonly employed in drywall construction and a r e available f r o m s e v e r a l Canadian manufacturers.

J) *:kFloor T r a c k s : Standard type floor t r a c k s approximately 1 3/16 by 2 1/2 in., 0. 020 in. in thickness w e r e used t o anchor the s t e e l s t u d s on wall No. 4.

CONSTRUCTION O F TEST WALLS

Unit m a s o n r y walls w e r e laid up i n a p r e c a s t c o n c r e t e r e s t r a i n i n g f r a m e in a c c o r d a n c e with recognized and acceptable m a s o n r y p r a c t i c e . Workmanship was g e n e r a l l y good throughout. T e s t walls m e a s u r e d a p p r o x - i m a t e l y 10 by 12 ft and w e r e allowed t o c u r e f o r one month p r i o r t o application of drywall. F i g u r e 1 shows construction of a typical t e s t wall.

Gypsum wallboard of specified thickness was e i t h e r laminated o r s e c u r e d t o m a s o n r y by m e a n s of wood stripping o r r e s i l i e n t s t e e l channels on the exposed f a c e of a l l t e s t s p e c i m e n s . In t h r e e of the t e s t s (Nos. 1, 2 and 3), d r y w a l l was applied t o the exposed s u r f a c e and one-half of t h e un- exposed face. In the r e m a i n i n g t h r e e t e s t s , d r y w a l l was applied t o c o m - pletely cover both the exposed and unexposed s u r f a c e . This a r r a n g e m e n t enabled f i r e p e r f o r m a n c e d a t a t o be developed f o r walls commonly used as e i t h e r i n t e r i o r partition walls, e x t e r i o r building walls, o r w a l l s adjacent t o s t a i r w e l l s .

F o r t e s t walls i n which wallboard was s e c u r e d d i r e c t l y t o m a s o n r y s u r f a c e s (Nos. 1, 3 and 5), t h e laminating adhesive was applied u s i n g a s t a n d a r d applicator as shown in F i g u r e 2. A 3/8-in. bead of m a t e r i a l was applied around the p e r i m e t e r and along t h e diagonals of t h e wallboard. F i g u r e 3 shows a close-up view of t h e adhesive a f t e r application. A f t e r being laminated t o the m a s o n r y s u r f a c e , the wallboard was s e c u r e d by 3/4-in. c o n c r e t e n a i l s (approximately one n a i l p e r 2 s q ft of wall a r e a ) . F i g u r e s 4 and 5 show the wallboard being nailed i n place and t h e application of the joint compound and tape. The exposed and unexposed s u r f a c e s of a typical t e s t wall p r i o r t o f i r e e x p o s u r e a r e shown in F i g u r e s 6 and 7.

In t e s t No. 6, wallboard was s e c u r e d t o nominal 1

-

by 3 -in. wood f u r r i n g s t r i p s spaced at 16 in. o. c. S t r i p s w e r e attached t o m a s o n r y with 2-in. c o n c r e t e n a i l s and wallboard s e c u r e d t o wood s t r a p p i n g with 1 1/4-in. lath nails.

F o r t e s t No. 2, r e s i l i e n t s t e e l channels 2 by 1/2 i n . , 0. 021 in. thick w e r e spaced a t 24 in. o. c. and attached t o m a s o n r y with 1/2-in. c o n c r e t e n a i l s a t 16 in. on v e r t i c a l c e n t r e . Wallboard was s e c u r e d t o s t e e l channels with 1 -in. s c r e w s a t 8 t o 12 in. o. c.

In t e s t No. 4, two l a y e r s of 1/2-in. r e g u l a r gypsum board w e r e applied on e i t h e r s i d e of t h e wall. The f i r s t l a y e r w a s s e c u r e d in the v e r t i c a l position t o 2 1 /,?!-in. s t e e l s t u d s spaced a t 16 in. o. c. by 1 1 /4-in.

*':: Component J i s commonly employed in d r y w a l l construction and i s available f r o m s e v e r a l Canadian m a n u f a c t u r e r s .

s c r e w s . The second l a y e r was laminated in a horizontal position and further secured with 3/4-in. concrete nails.

F I R E ANT) HOSE STREAM TESTS

Test walls were subjected t o standard f i r e and hose s t r e a m t e s t s

in accordance with ASTM E l 19-71. The furnace t e m p e r a t u r e was m e a s u r e d

by 9 s y m m e t r i c a l l y distributed thermocouples enclosed in 13/16-in. o. c.

inconel tubes with a carbon s t e e l cap. Both the individual t e m p e r a t u r e at 9 points of the furnace and the average f u r n a c e t e m p e r a t u r e were recorded.

Unexposed s u r f a c e t e m p e r a t u r e s of walls w e r e m e a s u r e d by

9

thermocouples covered with standard a s b e s t o s pads, 6 in. s q u a r e and 0. 4 in. thick. F o r walls with no wallboard on one half of the unexposed surface,

5 thermocouples w e r e positioned s y m m e t r i c a l l y on either half of the un-

exposed surface.

During the f i r e exposure, t e m p e r a t u r e s w e r e recorded under the wallboard on both the unexposed and exposed faces of the walls.

Deflection m e a s u r e m e n t s w e r e a l s o taken t o d e t e r m i n e the mid-point deflection h i s t o r y of walls during the t e s t s .

OBSERVATIONS DURING

FIRE

TEST

Exposed Surface

The observations in a l l t e s t s w e r e quite s i m i l a r . At about 30

seconds the paper covering of the wallboard b u r s t into flame and the flaming continued f r o m 3 to 5 minutes until the paper was completely cleared. By

7 minutes the tape and joint s e a l e r w e r e peeling from a l l joints. All thicknesses

of wallboard w e r e s t i l l intact a t 10 minutes.

The 3/8 -in. wallboards began cracking and deflecting significantly

by about 11 or 12 minutes. The 1 /2 -in. wallboards displayed the s a m e

behaviour about 8 t o 10 minutes l a t e r .

In

the c a s e of the wall protected by

a double l a y e r of 1 / 2 _{-in. board, the p r o c e s s simply repeated i t s e l f with the}

second layer after the f i r s t had fallen off.

Falloff t i m e s for the wallboard ( a r b i t r a r i l y assumed t o be the time a t which thermocouples installed between the board and the block face reached 500" F ) a r e listed in Table 11.

Unexposed Surface

On _{the walls where half of the unexposed side was left bare, some}

v e r t i c a l cracking was observed in the blocks after about 1 hour. Walls

until they collapsed at 117 and 130 minutes, respectively. Figure 8 shows the wall in the e a r l y stage of collapse and Figure 9 shows i t s condition a f t e r collapse. Note that the unexposed gypsum l a y e r was s t i l l in place and the wood f u r r i n g s t r i p s in reasonably good condition.

RESULTS F i r e T e s t s

The f i r e t e s t r e s u l t s a r e summarized in Table 11. F i g u r e s 10 to

15 show the significant t e m p e r a t u r e h i s t o r i e s and deflections. Hose Stream T e s t s

All walls, with the exception of Nos. 3 and 6, successfully withstood the hose s t r e a m t e s t . Because the collapse of Nos. 3 and 6 was unexpected, no alternate specimen had been prepared f o r a hose s t r e a m t e s t . These

walls, therefore, w e r e assigned ratings of only 1 hour r a t h e r than 1 1/2 hours. DISCUSSION

Although the f i r e t e s t s e r i e s was limited i n scope, the d a t a w e r e examined t o d e t e r m i n e i f a simple and reliable method could be found f o r calculating the contribution of gypsum wallboard to the f i r e endurance of masonry-wallboard a s s e m b l i e s . Two methods a r e proposed which appear to provide acceptable r e s u l t s .

The membrane method a s s u m e s that the additional protection provided by the wallboard i s a function p r i m a r i l y of i t s ability t o s t a y in place. Its contribution t o f i r e endurance, based on thickness, m a y be added d i r e c t l y t o that of the unprotected wall. Where wallboard is applied t o both s i d e s of a m a s o n r y wall, that on the unexposed s u r f a c e h a s been assigned t h r e e t i m e s the rating of that on the exposed s u r f a c e because it m a y be expected t o

remain in place for a significantly longer period. Table I11 shows the time assigned various thicknesses of wallboard by this method. Owing t o the collapse of both a s s e m b l i e s involving 4-in. hollow units in the test s e r i e s , the total allowable contribution of the wallboard on both the exposed and un- exposed s u r f a c e s should be limited t o a n increment equal t o the f i r e endurance value a s assigned in " F i r e P e r f o r m a n c e Ratings"

*

to the unprotected wall.

It will be noted that the t i m e assigned t o wallboard m e m b r a n e s on the exposed surface corresponds t o that assigned by Supplement No. 2 t o s i m i l a r protective m e m b r a n e s when used in s t e e l or wood stud construction. For t h i s reason, the recommendations in Table I11 have been extended to include 5/8-in. standard gypsum wallboard.

-

:!: National Building Code of Canada, Supplement No. 2, F i r e P e r f o r m a n c e Ratings, ACNBC, 1965 (Note that f i r e performance ratings assigned depend on the type of aggregate in the units)

The p l a s t e r equivalent method d i f f e r s f r o m the m e m b r a n e method in that wallboard protection on t h e unexposed s u r f a c e i s a s s u m e d t o provide the s a m e protection a s gypsum p l a s t e r . Accordingly, i t s contribution t o the f i r e endurance of the composite a s s e m b l y m a y be calculated by t h e method

d e s c r i b e d in Table 1. 5. 1 of Supplement No. 2 for a s s e s s i n g t h e contribution

of p l a s t e r protection.

In t h i s method, the contribution of t h e wallboard on the exposed s u r f a c e i s calculated in a m a n n e r s i m i l a r t o that outlined in the m e m b r a n e method.

The limitation placed on t h e t o t a l contribution of the wallboard in t h e c a s e of 4-in. solid o r hollow walls a l s o applies in the c a s e of t h e p l a s t e r m e m b r a n e method.

The following examples show t h e calculations in computing the f i r e endurance of a 4-in. solid c o n c r e t e m a s o n r y wall having 1/2-in. gypsum wallboard on both s i d e s .

A) Membrane Method

-

Equivalent thickness of m a s o n r y units a s

d e t e r m i n e d by m e a s u r e m e n t

-

F r o m Supplement No. 2, f i r e endurance of

unprotected wall

-

Contribution provided by 1/2-in. wallboard

on both s i d e s (Table 111)

-

F i r e endurance of composite a s s e m b l y = 3. 60 in.

=

57 rnin = 60 rnin

=

117 rnin B) P l a s t e r Membrane Method

-

Equivalent thickness of m a s o n r y units

=

3. 60 in.

-

Additional equivalent thickness provided by 1 /2-in.

wallboard on unexposed s i d e = 1 . 5 x 1 /2 = 0. 75 in.

-

Total equivalent thickness = 4. 35 in.

-

F r o m Supplement No. 2, f i r e endurance

contribution provided by 1 /2 -in

wallboard on exposed s i d e (Table 111)

-

F i r e endurance of composite a s s e m b l y

=

8 2 rnin

=

1 5 rnin

=

97 rnin

As t h e s e examples i l l u s t r a t e , t h e p l a s t e r equivalent method yields m o r e c o n s e r v a t i v e r e s u l t s than t h e m e m b r a n e method but m a y provide m o r e flexibility in dealing with v a r i o u s types of composite a s s e m b l i e s .

Table IV shows a c o m p a r i s o n of the r e s u l t s obtained by both methods in computing t h e composite f i r e endurance p e r i o d s of t h e a s s e m b l i e s t e s t e d in this p r o g r a m .

REG OMMENDATIONS AND CONCLUSIONS

Based on the limited amount of t e s t d a t a available, the proposed

methods appear t o provide a reasonably a c c u r a t e approach t o a s s e s s i n g

the contribution of wallboard t o the f i r e endurance of composite m a s o n r y

a s s e m b l i e s . In the absence of any specific t e s t d a t a o r when r e s o u r c e s

a r e not available t o p e r m i t a detailed analytical study, t h e s e methods m a y

be used t o provide acceptable e s t i m a t e s .

It should be noted that the method of attaching wallboard to m a s o n r y i s c r i t i c a l if the d e s i r e d performance in f i r e i s t o be achieved. Because little published information i s available on the ability of various attachment methods to e n s u r e adequate retention during f i r e exposure, it i s recommended that the methods employed in this t e s t s e r i e s constitute minimum acceptable

requirements, i. e.

,

the method of attachment shall be at l e a s t equivalent to

those described in this study. ACKNOWLEDGEMENT

The authors wish t o thank M e s s r s . E. 0. Porteous and J.

E.

Berndt

Gyp s u m B o a r d I 1 !" 3/8-in. r e g u l a r w a l l - I b o a r d e a c h s i d e

+-I---

2 -':

1

1 /2-in. r e g u l a r w a l l - b o a r d e a c h s i d e I 3/8-in. r e g u l a r w a l l - b o a r d e a c h s i d e 1 /2 -in. r e g u l a r w a l l - b o a r d e a c h s i d e 4 - - - 3/8 -in. r e g u l a r w a l l - board e a c h s i d e Two 1/2-in. l a y e r s r e g u l a r w a l l b o a r d e a c h s i d e

::: On unexposed f a c e wallboard w a s applied t o one-half of wall s u r f a c e only. T A B L E I

DESCRIPTION O F TEST SPECIMENS

Unit M a s o n r y Method of R e m a r k s

Wall Attachment

6 -in. hollow L a m i n a t e d Wallboard s e c u r e d with

u n i t s 3/4-in. c o n c r e t e n a i l s ,

a p p r o x . 1 n a i l p e r 2 s q ft

4-in. solid 2 - x i - x 0. 021 -in. S t e e l c h a n n e l s s p a c e d u n i t s s t e e l r e s i l i e n t a t 24 in. o. c . a t t a c h e d t o

channels m a s o n r y with 5-in. c o n c r e t 1 n a i l s a t 16 in. o. c . Wall- b o a r d s c r e w e d a t 8 t o 12 in. 0. C.

4-in. hollow L a m i n a t e d Wallboard s e c u r e d with

u n i t s 3/4-in. c o n c r e t e n a i l s , a p p r o x . 1 n a i l p e r 2 s q ft 6 -in. hollow u n i t s 4-in. s o l i d u n i t s 4-in. hollow u n i t s F i r s t l a y e r s c r e w e d , s e c o n d l a y e r l a m i n a t e d Filmst layer v e r t i c a l l y screwerl t o 2 4 - x 1 5/8-in. s t e e l s t u d s , second l a y e r h o r izontalIy l a i n i n a t e d . S t e c l stud s p a c i n g tvas 16 in.

I

0. C . L a m i n a t e d Nailed t o n o m i n a l 1

-

x 3-in. wood s t r i p s Wallboard s e c u r e d with 3/4-in. c o n c r e t e n a i l s , a p p r o x . 1 n a i l p e r 2 s q f t Wood s t r i p p i n g s e c u r e d t o rnasonr y at 16 in. o. c. with 2-in, c o n c r e t e n a i l s . Wallboard secured t o s t r i p p i n g with I + - i n . l a t h nails.

TABLE I1

SUMMARY O F FIRE TEST RESULTS

ma son r y w a l l without gypsum wallboard on either

(1) A l l e n , L. W., Fire Endurance of Selected Non-Load Bearing Concrete Masonry Walls, DBR F i r e Study No. 25

Ottawa, M a r c h 1070, (NRCC 11275)

(2) Small-scale t e s t _m Ref. (1 1, with time reduced by 7'70 ( 3 ) Failed by collapse, no h o s e s t r e a m test

(4) Failed by c o l l a p s e , no hose stream t e s t

(5) Time f o r thermocouples under wall board to r e a c h 500°F

T A B L E

III

REC OMMENDED C ONTRIBUTION

TO

FIRE RESTSTANC E RATING O F G Y P S U M WALLBOARD FINISH ON

MASONRY

A N D

CONCRETE

( 1 ) F o r 4-in. walls of hollow m a s o n r y , t h e maximum allowable contribution of t h e wallboard is not t o exceed the value

assigned t o t h e unprotected wall itself (due t o the d a n g e r of c o l l a p s e ) Wallboard Thickness (in. ) 3 /8 1 / 2

5

/8 Total (1) 40 60 120 Contribution (Min) When Applied T o Exposed S u r f a c e Unexposed Surface 10 30 1 5 I 30 4 5 90

I

I 1

I

-

PRESCRIBED TEMP EXPOSED WALLBOARD TEMP

MINUTES

FURNACE AND TEMPERATURE UNDER EXPOSED WALLBOARD

MINUTES UNEXPOSED BARE MINUTES UNEXPOSED COVERED MINUTES DEFLECTIONS

I I I I I 20 40 60 8i) 100 120

MINUTES

FURNACE AND TEMPERATURE UNDER EXPOSED WALLBOARD

MINUTES UNEXPOSED RARE I I I I I ( 20 A,] fin ao 1011 I 2.7, M l H U T f S UNEXPOSED COVEREP MINUTES LlFFLECTlONS

MINUTES

FURNACE AND TEMPERATURE UNDER EXPOSED WALLBOARD

MINUTES UNEXPOSED BARE MINUTES UNEXPOSED COVERED MINUTES DEFLECTIONS

I I -FURNACE TEMP

---

PRESCRIBED TEMP I rr IF; l4 I.? HOURS

tURNACE AND TEMPERATURE UNDER EXPOSED WALLBOARD

I HOURS UNEXPOSED SURFACE I 7 8 HOURS

UNEXPOSED SIDE UNDER GYPSUM BOARD

I I ! I I I I ! I

0 I ?

HOURS DEFLECTION

I I I

I A

FURYBSF TEMP

--- PRESCRIBED TEMP

----

EXPOSED WALLBOARD TEMP

I

80 _{100 120}

MINUTES

FURNACE AND TEMPERATURE UNDER EXPOSED WALLBOARD

MINUTES

UNEXPOSED SIDE UNDER GYPSUM 8omn

MINUTES

UNEXPOSED SURFACE

MINUTES

DEFLECTIONS

MINUTES

FURNACL AND TEMPERATURE UNDER EXPOSED WALLBOARD

MINUTES UNEXPOSED SURFACE

MINUTES

UNEXPOSED SIDE UNDER GYPSUM BOARD

MINUTES DEFLECTIONS