DBR Studies on Unit Masonry - (May 1958 to July 1959)

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Publisher’s version / Version de l'éditeur:

Technical Note (National Research Council of Canada. Division of Building Research), 1959-08-01

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Gibbons, E. V.

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NATIONAL RESEARCH COUNCIL OF CANADA

DIVISION OF BUILDING RESEARCH

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No.

288

NOT FOR PUBLICATION

PREPARED ｂｾｏｖｑ Gibbons CHECKED BY

FOR INTERNAL USE

APPROVED BY NBH

PREPARED FOR CIB Working Group on Rain Penetration

SUBJECT DBR STUDIES ON UNIT MASONRY =

(May

1958

to

July 1959)

DATE August

1959

The Division of Building Research has not always found it possible to send representatives to the meetings of the CIB Working Group on Rain Penetration on which it holds ｭ･ｾ｢･ｲｳｨｩｰｯ but has attempted to report progress through Notes such as this to all meetings not attendedo In May

1958

_{v Technical Note Noo}

249 (I}

was circulated to members of the Working Groupo A short desoription was given of the work of the Division related to rain penetration

since the Paris meeting in

19570

This present Note has been prepared to supplement the information given at that time and to inTorm the members of rain penetration studies carried on and other project work of special interest during the past yearo

In the previous Note reference was made to DBR Internal Report Noo 108 ＨＲＩｾ which presented the initial results of rain penetration tests on

21

large masonry panelso These ｰｾｮ･ｬｳ had been constructed with different types of brick and mortar ･ｯｭ｢ｩｮ｡ｾ

tions and tested when about six weeks oldo The panels have now been retested after a minimum of 1

1/2

years of outdoor weatheringe A report is being prepared in which a comparison is made of the information obtained at the two different times of teste The results indicate that those panels constructed with bricks of low

initial rates of absorption (IRA v

3-9)0

and which showed little or no leakage initiallyv continued to have high ｲ･ｧｩｳｴ｡ｮｾ･ to leakage after two years of ｷ･｡ｴｨ･ｲｩｮｧｾ This was true ofpanel$ constructed with either a high proportion of-cement or a high proportion of Itme in the mortar mixo The test panels made with intermediate IRA bricks

(15-19)0

and which showed same leakage initiallyv were found to have their resistance to leakage considerably improved after weatheringo This too applied to panels made with either a high cement or high lime type of mortaro

A few panels which had been constructed with intermediate IRA bricks and a

19299

mortar9 and panels made with high IRA

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· .

"" 2 ""

of wetting and drying after the weathering periodo In eaoh instance leakage was reduoed to negligible quantities despite appreciable leakage when they were first testedo

Silioone was applied after the initial leakage tests to a concrete brick panel and to a pressed brick panelo The ｴｾ･

for water to appear on the baok side of the panel increased oonsiderably in eaoh instanoe over the time required for· the panels when untreatedo It was observed9 however9 that with a

prolonged ｳｾｵｬ｡ｴ･､ wind-driven'rain oondition little improvement in the rate of leakage resultede

The small panel leakage testing apparatusl) described in DBR Internal Report Noo 160 (3)l) has been used to study the

influenoe of silioone pretreatment and wetting of brioks on

moisture penetration of brick maaonryo Many Canadian bricks are high in suctionl) and are therefore difficult to bond with mortar o Moisture can usually'penetrate the ｢ｲｩｾｫ］ｭｯｲｴ｡ｲ interfaoe readilyo

One of the three UoSoAo produoers of silicones has promoted the treatment of bricks with water=soluble silicone (at the plant)

in order to eliminate briokwork staining and effloresceno60 Suoh a treatment reduces the brick suotion and therefore was considered worth investigating as a means of improving bond between brick and mortar and so enhanoing the resistanoe of the

brickwork to moisture penetrationo 'Soaking of briQks has long been reoognized as being useful for improving bond» 'but in

Canadian ｰｲ｡｣ｴｩ｣ｾ it is rarely done and may have some disadvantagese Thirty=two small panels or the fivs=brick type used in

previous studies were constructed of two types of brioks (both high suction) and two mortars (lg3 masonry cementg ｳｾｮ､ and

19299 portland cementglimegssndl) relatively low and moderately

high in water retentivitY9 respeotively)o Each briok was used in

4

conditionsg (1) dryv (2) soaked 10 minutesD

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treated

with a relatively llght applioation of water=soluble silicone

_r

and

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treated with a heavier application of si1ioon90 After ｬｾ days of curing,9 the panels were tested by water spray on the

surface and an ｡ｩｾ pressure ､ｩｦｦ･ｲ･ｮﾩｾ aoross the panela Records were kept of the time for dampness to reach the baok of the pane1g

the rate of 1eakagev and the total leakage in

24

hours of teste

The silicone pretreated bricks (condition 49 above) produced panels highly superior to the others in resistance to moisture penetration e Soaking the bricks improved the tightness

9f

the panel alsop compared with bricks used dry.9 but the

improvement was much less than that obtained ｦｲｾ the sili©one

0" pretreatmento The ｢ｾｩ｣ｫｳ with a light ｡ｰｰｬｾｾｳｴｩｯｮ of silicone

(condition

3)

produoed panels which were generally inferior to

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_---those of soaked brick80 It was concluded that water=soluble silioone pretreatment p which reduGed ｢ｾｩ｣ｫ suction to a low valu6 p was very beneficial to the bonding of mortar to brick with regard to resiBtance to moisture ｰ･ｮ･ｴｲ｡ｴｩｯｾｯ

Several panels

ware

exposed outdoors over

one

wintero It was observed that those in whi@h ｾＱＱｩ｣ｯｮ･ pretre,ted bricks had been used presented a much cleaner ｡ｰｰ･｡ｲ｡ｮ｣ｾＹ those of untreated bricks being stained by _{salts o None of the panels} showed signs of damage from weatheringo

Studies of the influence of soaking and silicone pre-treatment of bricis on the strength of bond between brick and

mortar have been started p but insufficient information has been obtained to draw ｇｯｮ｣ｬｵｳｩｯｮｾｯ

Rain penetration studies at the ｄｩｶＱｳｩｯｮｾｾ regional

station at Halifax' have constituted the major laboratory activity there during the past 1ea1"o Extensive use has been made of the gmall panel leakage ｡ｰｰ｡ｲ｡ｴｵｾ in investigating the performance of the local ｭ｡ｴ･ｲｩ｡ｬｾ available in this maritime ereso The results of a preliminary program involving same

25

small panels have been des@ribed in DBR Internal Report Noo 161 (4)0 Since then further studies have been undertaken to determine the effect of such factors ｡ｾ (a) time interval between laying a mortar

bed and placing _{the se©ond brick in it v (b) the pressure applied} to the bri6k after it has been placedo (©) flow properties of the mortaro This work will be reported in d*tail ｬ｡ｴ･ｾｰ but in general it was observed that ｢ｯｾ､ strength and resistance to leakage decreased when the time interval for (8) above was over

30

ｳ･｣ｯｮ､ｾｯ Increased pressure (heavy tap) gave better value

for bond as did higher flow mortariSlo Some ｗｏｬＢｾ is in progl"e81S to ､･ｴ･ｾｩｮ･ the effect of tooling the ｪｯｩｮｴｾｯ

The effect of loss of moisture from mortars upon oontact with brioks of var10us ｾｵｾｴｩｯｮｳ has been given in DBR Internal

ｒ･ｰｯｾｴ Noo 173 (5)0 This work was .UUdertaken to investigate

lr

the loss of moistUF6 from the mortar bed to the lower bri©k would affect the ultimate bond of the top bricko From this study it

was concluded that

wA

ｾｵ｢ｳｴ｡ｮｴｩ｡ｬ reduction in the moisture ©QDtent of a mortal" takes place upon conts@t with ｢ｲＱ｣ｫｾＹ and this

reduction increases as the su@tlon of the brick ｩｮ｣ｲ･｡｡･ｾｯ

Greatest moisture loss takes pla©e during the initial stage of

conts@t₉ and during this timev with bricks of high suctionD moisture

losses are 1Sufficientto lower p1s$1ticity of the mortsw to a point where it is not capable of good bonding with another bricko"

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=

4

ｾ

COLD WEATHER MASONRY STUDIES

Referenoe was made in Technioal Note Noo

249

of the plans of the Division to study the effect of laying=up unit masonry in cold weather conditionso During the past year the ｣ｯｮｳｴｲｵ｣ｴｩｯｾ

of a cold room9 designed for these purpos8SD was oq,mpletedo and

some laboratory work ｷ｡ｾ undertakeno Prelfminary studies were started to determine the oube crushing strength of frozen fresh mortar and the bond strength between bricks and frozen fresh mortars0 The work has been extended to study the performance of

various mortars with low IRA suction brickso These studies were

undertaken about seven months ago o and it-is too soon as yet to show trends or draw tentative ooncluslonso

MASONRY CEMENT STANDARDS

Increased use of masonry oements oontinues ｩｾ Canadso

During the year ｣｡ｭｭｩｾｴ･･ work has been undertaken on the develop-ment of a standard for s high lime masonry cedevelop-mento Field studies

have been planned to observe the ｰ･ｲｦｯｲｭ｡ｮｾ･ in buildings of this and other mortar materials over a period of yearso Studies of the autoclave expansion test as applied to the high ｉｴｭｾ masonry cement have been startedo

MOISTURE EVAPORATION

Studies were started to determine tha haat ｴｾ｡ｮｳｦ･ｲ 00=

efficients from an open water surfaoe during the winter monthso This work is being done by the Snow and Ice Section of the

Division by means of a tank 9 feet in diameter and 1 foot in depthp exposed to the natural weather conditionso Observations

to date indi©ste that a good ©orrelat1on exists between the rate of heat 105s from the water surfaoe and the ､ｩｲｦ･ｲ･ｮｇｾ between the hourly mean scl air temperature and hourly mean ｳｵｲｦ｡ｾ･ water temperatU,J"60

MOISTURE MEASUREMENT

Methods for measuring the moisture content of soils in situ have been a continuing study of the Soil ｍ･ﾩｨ｡ｮｩｾ｡ Section of the Divisiono The proceedings of the Conference on Building Resear©h-1953o contains a paper entitled "The Measurement of Moisture Content"

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The paper outlines ｳｯｭｾ of the problems

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... 5 ...

More recently a neutron moisture meter has been oonstructed foJ!' measuring the moisture content of soilo As yet only limited use

has been made of this instrument!) but Teohnical Note NOl)

269

may be of interest since it assesses materials which might be used in the oalibration of this type of metero

Instrumentation has been developed which enables the length of time of wetness to be measured on .an exposed metal surfacti"o' This work was undertaken as part of the studies of ASTll Committee

B-3

on Corrosion of Non-Ferrous Metalso The

sensitivity of the instrument permits traoes of moisture as with a light dew or snow at low temperatures to be detected and be differentiated from moisture due to a heavy raino A progress report in which the measuring device is desoribed appears in ASTM Bulletin Noo 228_D February

1958

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Two briok masonry test huts were oonstruoted in

1954

by the Building Servioes'Seot10no One of the huts was insula tad!) the other uninsulated o The temperatures through the bricks of the walls facing the four principal directions have been recorded continuously since the huts were put into operationo An analy is of these temperature cycles 1s now in progr and ...i11 provide information on freeze=thaw cycling in these wall 0 Rainfall

measurements have been oontinued bY' mans of NRC rain cups on eaoh ｷ｡ｬｾ of the test huts as well as total rainfa 1 by the directional rain gaugeo

A start has been made on the development or s. test method and design of equipment for the measurement of rain leakage and air infiltration of windowso This work is of special interest

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REFERENCES

ｬｾ Gibbons,!) Eo

V

o Resume of DBR Unit Masonry Studies (May

1957 .."

April

1958)0

National Researoh Counoi19 Df,vision of

Building Researoh.l) ｔ･ｾｨｮｩ｣｡ｬ Note

2490

OttawSl,!) June

19580

\

20 _{Ritohie D To and GoW}o Pleweso Preliminary tests of the,rain

resistance of briokwork panelso ｎｾｴｩｯｮ｡ｬ Researoh

Counci19 Division of Building Researchg Internal Report

1080 Ottawag Septo

19560

30

Ritohie,!) To A sma11=panel method for investigating moisture penetration of briok masonryo National Research Counoilg

Division of Building ｒ･ｳ･｡ｲｾｨＬＡＩｉｮｴ･ｲｮ｡ｾ Report 1600

ｏｴｴ｡ｷｾＹ Septo

1958

0

40

DavisoDD ｊ｡ｉｾ and JoDo Atkinso Small brick panel tests at Halifax <=> a preliminary program on leakage and bond

strength0 National Research Council_v Division of Building

1610

OttawaD Novo

19580

50

DavisonD JoI e Loss of moisture from mortars upon contaot with

brioks of various 9uotionso National Researoh Counoils Division of Building Resear@h_v Internal Report

1730

OttawaD April

19590

60

PennerD Eog CoBo Crawford and "oJ0 Edena The measurement of

21

to 239

19530

National Research Counoil,!)

NRC

3568

D po

65=730

Ottawa,!) Septo

19550

70

_{Sereda s PoJo} Measurement of surfaoe moisture = a progress , reporto uASTM ｂｕＢｉＱＮ･ｴＱｮｬｩｯｯＭｾｄ 7eoo ＺｊＺＹＵｻｲｾｰｯＵｊ･ｯＵｾｾ

(Reprint available fram Division of Building ｒ･ｳ･｡ｾﾩｨＹ