Effect of silicone treatment on small panels assembled with high suction dry-press bricks

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Effect of silicone treatment on small panels assembled with high

suction dry-press bricks

CANADA

Dl VISION OF BUILDING RESEARCH

EFFECT OF SILICONE TREATMENT ON SMALL PANELS ASSEMBLED WITH HIGH SUCTION DR Y -PRESS BRICKS

by

J. 1. Davison

Internal Report No. 241 of the

Division of Building Research

OTTAWA February 1962

PREFACE

Studies carried out as part of the brick masonry research program of the Division on a high suction, dry-press brick manufactured in the Atlantic area have been extended to include the bricks now

pro-duced, following a major modification to the brick kiln. Bricks

from this source have also been used in a further extension of the program to cover an examination of the effects of various treatments, including the use of silicones, on the bond strength and leakage

characteristics as found in small masonry panels. All of this work

has been carried out at the Atlantic Regional Station of the Division at Halifax by the author who is a chemist and a research officer with the Division and is engaged in masonry studies there.

Ottawa

February 1962

N. B. Hutcheon, As sistant Dir ector.

ASSEMBLED WITH HIGH SUCTION DR Y -PRESS BRICKS by

J. 1. Davison

In a previous study (1), tests on small brick panels assembled with a high suction dry-press brick manufactured in the Atlantic area and four different mortars revealed leakage in all panels and established that it was occurring through the bricks as well as at the interface

between the brick and mortar bed. No attempt was made, however,

to assess the relative importance of these two sources of leakage. While the above-mentioned test program was in progress,

changes were made in the tunnel kiln at the plant. The burners

formerly located in the top of the kiln (Brulax System) were relocated along the sides in an effort to eliminate problems associated with

the former system. A second shipment of bricks was, therefore,

obtained during the summer of 1960 for the purpose of (a) comparing

the properties with those of the previous shipment and (b) continuing

the study of leakage on small panels assembled with these bricks and the influence of some silicone treatments on the panels.

PROPER TIES OF BRICKS Absorption

The 471 bricks in the lot wer e red in colour, uniform in

size with dimensions of 8 by 3 3/4 by 2 1/4 in. All bricks were dried

for 72 hours in a drying oven at 110°C and then the Initial Rates of

Absorption (IRA) were determined. Distribution of IRA values for the

shipment is shown in Fig. 1. In comparison with values for bricks

in the previous lot, suctions (IRA) were slightly lower, e. g. 73.1 per

cent of the new lot had values under 60 gm compared with 51. 0 per cent for the previous lot, while 58.8 per cent of the new bricks were under 50.0 gm compared with 35.5 per cent of the old.

Twenty samples, r epr esentative of the over -all suction range (11. 0 - 101. 0 gm), were selected for 24-hr submersion and

5-hr boiling absorption tests. Results are given in Table 1.

Com-parison with values for the previous lot again indicates somewhat lower absorptions for the new bricks.

2

-COMPRESSIVE STRENGTH AND FREEZE-THAW TESTS

Eleven of the above bricks wer e cut in half for compr es sive

strength and freeze-thaw tests. Compressive strength values are

also listed in Table 1. It will be noted that compressive strength

values decrease as the brick suction increases and a sharp reduction in compressive strength occurs when brick suction increases above 85 grn ,

All 11 samples failed during fr eeze -thaw tests - the

failures occurring between 11 and 32 cycles. Results indicate that

the number of cycles to failure decreased with increasing brick suction (Table I I).

Five bricks which had been dipped for various time intervals in a 3 per cent aqueous silicone solution were subjected to freeze-thaw

cycling; results are also shown in Table I1. Further information on

this treatment, its effect on the absorption of the bricks, and subse-quent freeze-thaw tests is given in Table III.

Sample No.1, immersed in the solution for only 5 sec,

failed after 16 freeze-thaw cycles. This is comparable to the failure

of the 65-gm suction untreated brick after 15 cycles. The remaining

4 treated samples successfully completed 50 freeze-thaw cycles. These results also indicate that immersion time has little effect on the final suction of the br i ck although the amount of silicone

absorbed by the bricks increased with the immersion time. The 5-sec

immersion time was, however, apparently not sufficient to effectively

" w aterproof" the surface of sample No. 1 from water penetration during

the soaking period in freeze -thaw cycling and deterioration occurred during subsequent freezing; sample No.2, however, which absorbed less silicone while reaching a lower final suction value, survived the

test with the lesser weight loss. It is possible that there were cracks

in sample No. 1 that were too large to be completely waterproofed

by this small amount of silicone. Visual observation of fractured

portions of sample No. 1 revealed silicone penetration to a depth of approximately 1/2 in.

EFFLORESCENCE

The effect of a silicone treatment on efflorescence in these

bricks was briefly investigated. An untreated high suction dry-press

brick (IRA 85 gm), and an untreated low suction extruded stiff-mud brick (IRA 7 gm) were immer sed to a depth of 1 in. in a solution of

sodium sulphate (Fig. 2a). Heavy efflorescence occurred with the high suction brick within a few hours but only a "water -line" deposit of the salt appeared on the low suction brick even after several months

had elapsed. Seven half-bricks ranging in suction from 6.5 to 90.0

gm, including 5 of the red dry-press bricks, were then given 2 coats of a 5 per cent mineral spirit based silicone solution by dipping them

in the solution to a depth that left only 1 3/4 in. untreated. These

bricks were also immersed in the sodium sulphate solution - the

untreated portions to a depth of 1 in. No efflorescence appeared on

the siliconed areas of the bricks during a 3 -month test period nor was there any indication of a build -up of salt under the siliconed surface (Fig. 2b).

TRANSPIRATION OF WATER VAPOUR THROUGH SILICONE-TREATED BRICK SURFACES

A brief investigation into the capacity of water vapour to transpire from the bricks through a silicone-treated surface was also

conducted. In the first instance, five sides of a high-suction brick

(IRA 81. 5 gm) were siliconed by dipping the brick (all but one side)

in a 5 per cent mineral spirit base solution for 10 sec. This brick

and an untreated control brick were soaked in water for 24 hr. The

untreated side of the siliconed brick and a similar surface of the control

brick were then sealed off with Lasto -Meric and polyethylene.

Tran-spiration of water from the bricks was followed by weighing the

samples at measured intervals. During the "drying" period samples

were kept in a controlled atmosphere of 70°F and 50 per cent RH.

Results are shown in Fig. 3a. In a second experiment, the procedure

was repeated with one surface of a brick being siliconed and the remaining sides sealed off after soaking the brick in water for 24 hr.

Results are shown in Fig. 3b. In both cases, the water in the bricks

was able to "escape" through the siliconed surface. This is consistent

with the claims of the manufacturers that a silicone treatment does not seal off the surface but rather lines the pores with a water -repellant material while still permitting the brick to "br eathe. "

LEAKAGE THROUGH BRICKS

Near the end of the previous study (1) it was established that moisture penetration was occurring through individual bricks. Eleven bricks representative of the over -all IRA range of the lot were thus selected and subjected to the regular 24-hr test in the small panel

4

-leakage cabinet (using a 4-brick dummy panel in conjunction with

the test brick). Water passed through all the bricks, small totals

for low suction bricks increasing as the suction of the bricks

increased. Leakage totals are compared with the brick suction

in Fig. 4. A sharp increase in leakage will be noted when the brick

suction increases above 55 gm.

CONCLUSIONS ON STUDIES OF BRICK CHARACTERISTICS A study of the properties of dry-press bricks fired in a tunnel kiln recently converted from a "top -firing" to a "side -firing"

system indicates:

(1) A slight r eduction in IRA and absorption values by

comparison with similar values for bricks produced before the change.

(2) Water can penetrate through these bricks under conditions

of the DBR small panel leakage test. A sharp increase in leakage occur s

when the brick suction increases above 55.0 gm.

(3) Although these bricks meet the physical requirements

for Grade SW Bricks as laid down by CSA Specifications for Building Brick, they fail at a comparatively early stage during freeze-thaw

cycling. Dipping the bricks for 10 sec in a 3 per cent aqueous silicone

solution improves their durability during freeze -thaw cycling.

(4) Application of a 5 per cent mineral spirit base silicone

solution to the bricks resulted in elimination of efflorescence occurring as a result of capillary action in a high suction brick and did not

prevent water vapour from transpiring through the siliconed surfaces.

PANEL PROGRAM

In developing the panel program the prime objectives were:

(1) To assemble a panel with these dry-press bricks that

would not leak during the laboratory leakage test.

(2) To assess the two sources of leakage (a) through the bricks

and (b) at the brick - mortar interface. The program therefore included:

(1) A series of control panels assembled with the bricks and

four different mortars and including different IRA combinations using both dry and soaked bricks.

(2) A series of panels duplicating the basic control group with the addition of a coating of 5 per cent mineral spirit base silicone solution.

(3) A series of panels containing bricks with a similar

silicone treatment on the exposed face but having untreated rno rta r joints.

(4) A brief attempt to investigate the effect of bricks

predipped in an aqueous silicone solution (Silaneal Process) on small panel performance.

General

All panels were assembled and tested for moisture penetration and bond strength following the procedures outlined in DBR Internal Reports 160 (2) and 175 (3).

Materials used in preparing mortars were those commonly

used by the trade in the area. These included Maritime Brand Portland

Cement, Canada Brand Masonry Cement, lime putty obtained from a local supplier, Shubenacadie Sand with a fineness modulus of 2.05 and a grading which fell within the CSA limits for aggregate for masonry mortar.

Mortar s wer e rnixe d to a flow of approximately 115 per cent

and panels were assembled with a 30-sec time interval between placing a mortar bed and laying the next brick which was "bedded" with a

heavy tap.

All panels were assembled in duplicate and were cured for 14 days in controlled laboratory air at 70°F and 50 per cent RH before moisture penetration tests, after wbi ch they were allowed a

14-day drying period before bond strength tests. Control Panels

There were 16 panels in the control series; information concerning their assembly as well as leakage and bond strength tests

is contained in Table IV. The first 8 panels included duplicate sets

assembled with bricks in the 44- to 72-gm suction range and the following 4 mortar s:

(l) 1: 3 masonry cement: sand,

(2) 1:1:6 c e rn errt : l i rne putty: sand,

(3) 1 :2:9 cement: lime putty: sand,

6

-The bricks for the lime putty: sand mortar panels were used dry; those for the other 6 panels were soaked in water prior to panel assembly.

There was considerable moisture penetration through

all 8 panels during the leakage te st ; the average totals are shown

graphically in Fig. 5, where it will be noted that the most leakage occurred with the lime mortar panel and the least with the 1 :2:9 cement -lime mortar panels.

Leakage began about 20 -25 minutes after the start of the test for the cement-lime mortar panels - reflecting the greater

retentivity of the former mortars. There was considerably heavier

leakage for the one lime mortar panel tested; there was very little bond strength in these panels and one was broken during handling prior to the leakage test.

The "leakage pattern" for these panels was fairly consistent during the length of the test, e. g., the hourly leakage rate remained

steady. This is a contrast to results noted in previous studies of

leakage in panels of dense low-absorption bricks where leakage through cement-lime mortar joints tended to taper off after reaching an early maximum, and in some cases stopped altogether before the end

of the test (4). The steady leakage pattern for cement-lime mortar

panels in the control series of this study was interpreted as evidence that the major source of leakage was through the bricks rather than at the brick-mortar interface, where the influence of the mortar would

have tended to reduce the leakage rate. Visual observations during

leakage tests verified the leakage through the bricks, and also possibly at the brick mortar interface, although what appeared to be leakage from the mortar joints might have been water coming from leaks in the bricks above, which spread along the mortar joint before continuing its downward path.

Best bond strength values occurred in the l: l:6 cement-lime mortar panels (average 42.4 psi) closely followed by the 40.6 psi

value for the masonry cement mortar panels. A somewhat lower

value of 30.8 psi for the 1 :2:9 cement -lime mortar panels was also

satisfactory. Visual examination of fractured mortar joints from

the 6 panels revealed a good extent of bond in all cases with no evidence

of moisture penetration at the brick-mortar interface. Typical

fractured joints are shown in Fig. 6. A bond strength value of 0.2 psi

was obtained for two joints of the lime mortar panel. The lime mortar

comparison of these 3 mortars is not possible because of the complicating leakage through the bricks.

The next 6 panels in the control series contained 1:1:6

cement-lime mortar with bricks in a lower suction (20-30 gm) and a higher suction (75-87 gm) range than those in the original group. Panels of low-suction bricks were assembled with dry and soaked bricks, while only soaked bricks were used in the high-suction range. Again there was leakage for all panels, the best result (89.5 ml)

occurring with the soaked low-suction brick panels and the most leakage

occurring with the high-suction brick panels (1247. 3 ml). Leakage

occurred within 3 min of the start of the test for the dry low-suction brick panels and after 60 min for the wet low-suction brick panels. Here it is apparent that soaking was beneficial, even with the

comparatively low-suction bricks; this resulted in better bonding and a tighter joint than that between the same mortar and dry low-suction bricks, with resulting earlier leakage in panels of the latter bricks. Combining the results for panels of soaked low- and high-suction bricks with those for panels of bricks in the 44- to 72-gm range, it is possible to illustrate the detrimental effect of increasing IRA on moisture penetration, all bricks having been soaked for 10 min prior to use (Fig. 7).

Bond strength values for low-suction brick panels contra-dicted leakage results, with the 24.0 psi value for the soaked brick panel being well below the 38.4 psi value for the dry brick panel. Visual examination of fractured mortar beds indicated a lesser extent of bond for the dry brick panels (Fig. 8) than for the soaked brick

panels. The best bond strength value, 42.9 psi, however, occurred

in the high-suction brick panel which also had the most leakage. The

latter value is about the same as the value for panels of bricks in

the suction range 44-72 gm using the same mortar. Evidence from

this group of panels substantiates a widely accepted view among

students of the moisture penetration problem, that there is no relation between moisture penetration and bond strength.

The remaining 2 control panels were assembled with dry

low-suction (11. 0-18. 5 gm) bricks and masonry cement mortar. Both

panels leaked, average total being 365 ml, and a bond strength value

of 24.2 psi was obtained. There were not enough bricks in this suction

range to try any other combinations.

Figures indicating the amount of water absorbed by the

8

-amounts range Irorn 490 gm for a soaked low-suction brick (1: 1:6

cement -lime mortar combination) to 815 gm for a dry medium-suction brick-lime mo r tar panel.

The control series thus illustrates that these bricks and several mortars cannot be combined, using a variety of favourable combinations, in a panel capable of successfully resisting moisture

penetration during the small panel leakage test. It was also concluded

that a considerable portion of the leakage occurred through the bricks and that bonding between b r i cks and mortar was relatively sound in many of the panels.

Panels Treated with Silicone on the Face

In the second phase of the panel program the control series was duplicated, with the exception of the low-suction brick-masonry cement mortar combination, and at the midway point (one week) in the curing period 2 coats of silicone solution were applied to the

exposure face of the panels. The silicone solution contained

Dow-Corning Silicone Fluid No. 770 in mineral spirit base and was 5

per cent in concentration. Application was carried out by flooding

the solution on the face of the panel from a plastic squeeze bottle. The second coat was applied 24 hr after the fir st one.

Pertinent information on the assembly of these panels, subsequent leakage, and bond strength tests are contained in Table V. There was no leakage for any panels, including the one lime mortar panel (again the duplicate broke while being handled prior to the leakage

test) which had very low bond strength. More remarkable than the

elimination of leakage is the evidence that practically no water entered

the panels during the leakage tests. This can be seen in the "water

absorbed" column in Table I V where, with one exception, totals lie

between 3 and 10 gm. These minor amounts probably represent the

water on the face of the panel at the end of the test. Panel No. 17, the

lone exception, . absorbed 128 gm of water and this is attributed to either incomplete coverage with the silicone, or a crack in one of the bricks too large to be effectively waterproofed by the silicone.

Upon completion of leakage tests, panels 13 to 18 inclusive (duplicates containing masonry cement and 1:1:6 and 1:2:9 cement-lime mortars) were placed on exposure at the York Redoubt Site to

study the durability of the silicone coating. It is proposed to return

these panels to the laboratory for a leakage for a leakage test after

is noted in the s iLi con e d surfaces.

Bond strength results for the r e rnainin g 6 panels were

inconsistent. The value of 47.5 psi for panels of dry low-suction

bricks and 1: l:6 c erri ent-Lirn e rn o r ta r was higher than the 38.4 psi

obtained in the control panel series, but it should be noted that

one of the control panels had a value of 47.9 psi and that the average value for the pair was lowered by an inferior value for the duplicate

panel. Inconsistencies of this nature occurred frequently in bond

strength tests throughout the study.

The value of 31.5 psi for soaked low-suction brick panels

of l: 1: 6 c ern e nt -Lirn e rno rta r was also higher than the 24. 0 psi

value for the control panels, while the 14.7 psi value for the soaked

high suction brick (L: 1: 6 c ernerit-Lirn e rn o rta r panel) was rnu ch lower

than the 42.9 psi obtained for the control panel. Typical rno r ta r joints

fr orn fractured panels in this group are shown in Fig. 9. The average

value of 0.9 psi for 3 joints of the l irn e m o r tar panel was higher than

the 0.2 psi value for the control panel, but the bond between bricks

and rrio rta r was still very inferior.

In this phase of the study the leakage in the control panels was e l irninat e d by a silicone application to the face of the panels. Panels Containing Bricks with a Silicone TreatITlent on their Face and Untreated lYlortar Joints

The next 8 panels were a s s ernb l ed with bricks that had previously received a coating of silicone on their exposed face; the

rn o rta r joints in the panels were not treated with silicone. The purpose

of this was to see whether water would penetrate the panel through

untreated rno rta r bed, or at the brick rno rta r interface. The silicone

tr eatrn ent consisted in the i rnrn e r sion of the bricks, face down, to a depth of 1/8 in .. in a 5 per cent rn in e r a.l spirit base silicone solution.

This procedure was repeated 24 hr later. All bricks were soaked in

water for 10 rnin before panel a s s ernbly , Panels were a s s erribl ed with

rn a s o n ry c ern ent rn o rta r and bricks in the 45- to 70-gITl suction range,

and with 1: 1:6 c ern errt -Lirn e mortar and bricks in the low, medium,

and high suction ranges previously used. Information on panel assembly,

leakage, and bond strength tests is recorded in Table VI. No leakage

occurred in any of the panels during the test, but there was some water penetration of the mortar joints indicated as "water absorbed. "

lO

-and therefore the tightest mortar joints occurred in the masonry

cement rn o r ta r panels. It is also interesting to note that moisture

penetration of the c ern cnt vl irn e rn orta r joints was inversely

pro-portional to the suction of the bricks used in the panels. It is

difficult to explain this, particularly since leakage totals for the

comparable control panels increased with increasing suction. It

is probably a result of the difference in bonding at the edge of the mortar joints caused by penetration of the silicone through capillary action

beyond the 1/8 in. to which the bricks were immersed. The arnount

of silicone thus depo sited on the p e r irn et e r ar ea of the bedding

surface of the brick possibly had a detrirn errt a l effect on bonding in that

area, varying with the suction of the bricks.

Bond strength values for these panels were less than half those obtained for the control panels (further evidence of the detrimental effect of silicone deposited on the perimeter areas of the bedding

surface on bonding). This was particularly evident for cement-lime

mortars, but not so for masonry c ern erit mortar. Best values were

obtained with medium-suction bricks while a lower value for the high suction brick panel was in contrast to high values for these

panels in the control series. Visual examination of typical fractured

joints from these panels substantiated a poor extent of bond along the

perimeter of the bedding surface. Typical examples may be seen in

Fig. 11.

Results from this series of panels establish that (l) tight

mortar joints can be obtained between dry-press bricks soaked in water and 2 mortars, and (2) most of the leakage occurring in control panels resulted from water penetration of the bricks.

Panels As sembled with Bricks Dipped in Aqueous Silicone Solution Ill. view of current interest in the use of bricks pretreated with silicone and possible benefits to be derived from such treatment, the final phase of this study included s orn e panels assem.bled with bricks pretreated by dipping in an aqueous silicone solution.

Enough bricks to assemble 6 panels were selected and immersed in Abbey "Raincheck", a commercial product claimed to

be a 3 per cent aqueous solution. The bricks were chosen from the

suction range used in the control series (45-70 gm) and after a

2-min irnrn e r sion in the solution they wer e air -dried overnight, and IRA

values then rechecked. The suction range was reduced to O. 2-1. 1 gm,

during the tr eatrn e nt . There was also a trend indicating an increase

in silicone absorbed, as brick suction increased. Three sets of

panels wer e as s errib l e d using masonry cement mortar 1: 1: 6 and

1:2:9 cement-lime mortars. Information on panel assembly, leakage

and bond strength tests is included in Table V I (Panels 39 -44 inclusive). During panel assembly, the operator noticed that the mortar remained very plastic and was extruded from lower mortar joints with

succes sive taps of the drop hammer. This was in contrast to

previous panels where mortar stiffened quite rapidly. It was also

noted that moisture losses to matched pairs of bricks, investigated in conjunction with panel assembly, were far below similar losses to soaked brick pairs investigated during assembly of control panels (5) .

MOISTURE LOSSES TO MATCHED PAIRS

Mortar Siliconed Soaked Bricks

Bricks (Control Panels)

1:3 masonry cement 0.1% 1.2%

1: 1:6 cement -lime 0.6% 0.9%

1:2:9 cement -lime 0.2% 0.8%

The panels wer e very fragile; one of the masonr y cement and one of the 1: 1 : 6 cement -lime mortar panels wer e broken during

routine handling prior to leakage tests. In both cases one brick was

lost from the panel, permitting completion of the leakage tests with 4-brick panels.

There was no leakage in any of the panels during the test

period. The ends of mortar joints of the masonry cement mortar

panels were darkened at the conclusion of the test while joints of

both c ern ente-Lim e mortar combinations were completely discoloured.

The first indication of moisture penetration (darkening of joints) occurr ed after 8 hr for the 1: 1: 6 cement -lime mortar and at

3 to 5 hr for the 1:2:9 combination. "Water Absorbed" totals were

60 gm for the panels of masonry cement mortar, 1.27 gm for the panels

of 1:1:6 mortar, and 167 gm for the panels of 1:2:9 mortar.

While the results of leakage tests were excellent, bond

12

-obtained for the control panels. The l sets of values are compared

as follows:

COMPARISON OF BOND STRENGTH VALUES

Mortar Siliconed Soaked

Brick Panels Brick Panels

1: 3 masonry cement 9.0 psi 40.6 psi

1:1:6 cement -lime 10.2psi 42.4 psi

1:2:9 cement -lime 4.6 psi 30.8 psi

Visual examination of fractured mortar joints revealed a reasonably good extent of bond for masonry cement mortar panels, but extensive unbonded areas in the cement-lime mortar panels.

(Typical examples are shown in Fig. 12.) In Fig. 12(a), masonry

cement mortar panels are compared with control panels of this

mortar and dry low-suction bricks (11. 0-18.5 gm}: Fig. l2(b) shows typical joints from the cement-lime mortar panels.

On the basis of these results, it was considered that the silicone treatment was too severe and had reduced the IRA values

of the bricks below the lower limit acceptable for good bonding. Of

the 3 mortars used, the masonry cement came the closest to giving a satisfactory result.

Accordingly, the silicone treatment was modified by

reducing the immersion time from 2 min to 10 sec, and enough bricks

were treated for four more panels. Twelve of the bricks had original

suction values in the 60.0- to 72. 5-gm range, while the remaining

12 fell in the 30 - to 40 -gm range. The final suctions and the amounts

of silicone absorbed by the treated bricks are summarized as follows:

RESULTS OF 10-SEC IMMERSION IN

30/0

SILICONE

IRA Range, gm/30 sq in. / sec Original 60.0 - 72. 5 30.4 - 40. 0 Final 0.5 - 1. 7 0.4 - 1. 5

Average Amount of Silicone, gm

Absorbed

22. 5

ReducinQ the immersion time from 2 min to 10 sec was

not sufficient to appreciably affect the final result. The ability of the

high absorption bricks to absorb the most silicone and thereby become reduced to the s arn e low suction range as the lower suction bricks is again demonstrated.

Panels were assembled with 1:1:6 cem.ent-lime and 1:3 masonry cement mortars; information concerning their assembly and leakage and bond str ength tests is included in Table V I (Panels

45-48 inclusive). Moisture losses to matched pairs of bricks were

of the same order as those in the previous group, 0.2 per cent for the cement -Lirn e mortar and 0.6 per cent for the masonry cement

mortar. There was no leakage for any of the 4 panels, but all

mortar beds were discoloured, indicating moisture penetration. The

discoloration of the mortar joints began after 7 hr of testing. Moisture absorbed during the test was slightly higher than totals

for the previous panels. Bond strength value of 10.1 psi for the

cement-lime mortar panels was about the same as the value for corresponding panels in the previous series, but the 16.1 psi value for masonry cement mortar panels was an improvement.

Typical joints from these panels, shown in Fig. 13, indicate a much better extent of bond for masonry cement mortar panels than for thos e containing cement -Lirn e mortar.

It was considered that for a good result the silicone treatment should be further modified to reduce the original brick

suction range to 5 - 15 gm. In the light of the minor change in final

suction values obtained by reducing the immersion time from 2 min to 10 sec, it did not appear that the desired results could be obtained

solely by adjusting this variable. To substantiate this, 6 bricks with

an original IRA of 66 gm were dipped in a 3 per cent aqueous silicone

solution for 5, 10, 20, 30, and 60 sec and 2 min. The amount of

silicone absorbed increased from 17.2 gm at 5 sec to 40. 2 gm at 2 min,

but the final suction range was 0. 5 - 1.

°

gm. There was no apparent

correlation between the final IRA and the i rnrn e r sion time. The

experiment was repeated using a 1 1/2 per cent silicone solution and an almost identical set of suction values was obtained.

A much weaker silicone solution was then prepared with

27 gm of Dow Corning No. 772 in 8000 rnl of water. The Dow Corning

fluid is reported to contain 1/3 silicone solids, so that the new solution

was about 0.1 per cent in concentration. Six high suction bricks ranging

from 67.

°-

90.

°

gm were immersed in the solution for 5, 10, 20, 30,

14

-time. Results ar c given in Table V II.

The final suction values for the bricks dipped for 5 and

lOsee, 1. 7 and 1. 2 gm, were higher than those obtained with the

stronger solutions, but were still considered too low for good bonding with the mortar s .

The silicone solution was further diluted by adding

2000 ml of water, making the concentration approximately 0.09 per

cent. Six bricks in the suction range 55.0 - 67.6 gm were immersed

in it for 5 sec with the following results:

Original Silicone Final

IRA, Absorbed, IRA,

gm/30 sq in./sec gm gm/30 sq in./sec 55.0 5.3 14.0 58.2 4.8 7.0 58.5 4.0 17.0 59.4 4.9 10.0 66.8 6.0 2.0 67.6 6.5 4.2

The final IRA range, 2. 0 - 17. 0 gm, was in the desirable area and a total of 28 bricks with original suctions between 45.5 and

67.6 gm were similarly treated. The final suction range was 1. 0

-18.5 gm and again there was a trend indicating greater absorption

of silicone with increasing brick suction. In Fig. 16, final suction

is plotted against original suction. Four high suction bricks (66. 8

-77. 0 gm) absorbed the lar gest quantities of silicone with resulting

lowest suctions, Unfortunately, there were not enough high suction

bricks treated to definitely substantiate the trend that high suction bricks, because of their ability to absorb larger amounts of silicone, have lower final suction values than bricks with lower initial values.

Twenty bricks in the suction range 2.4 - 14.8 gm were selected from the group, and duplicate panels were assembled with

masonry cement and 1:1:6 cement-lime mortars. Information pertinent

to their assembly, leakage, and bond strength tests is also contained in Table V I (Panels 67 to 70 inclusive).

All ,1 panels leaked; leakage started at 25 min for the masonry cement mortar panels, and within the first 10 min of test

for the cement-lime mortar panels. Average totals of 995 rn l for the

masonry cement mortar panels and 1414 mi for the cement-lime mortar p an e l s were higher than the respective totals of 701 and 932 rn l for

comparative panels in the control series. The average water absorption

totals were similar for the control and silicone -irnmersed brick panels. The leakage rate was consistent throughout the test for the masonry cement mortar panels, unlike that of the cement -lime mortar panels which declined after reaching an initial maximum shortly after the

start of the test. Visual observations during the test indicated leakage

through the bricks as well as at the brick mortar interface. The

silicone treatment made it pos sible to obtain a good pictur e of leakage

in these panels (Fig. 14).

The 36.6 psi bond strength value for masonry cement mortar panels was within 10 per cent of the control panel value and examination of fractured joints indicated an excellent extent of bond; most of the leakage occurr ed through the bricks rather than at the brick mortar interface.

The 24.9 psi value for the cement -lime mortar panels was 40 per cent lower than the value for comparative panels in the control series, and visual examination of broken joints revealed some good

extent of bond and some instances of incomplete bond. Typical examples

from the 4 panels are shown in Fig. 15 where incomplete perimeter

bonding will be noted for masonry cement mortar panels.

Results for th e s e panels indicate that a 5 -sec immer sian in

a very dilute aqueous silicone solution (0.09 per cent) was ineffective in preventing water penetration of panels assembled with the bricks, although the suction was reduced to the desirable 2- to l5-gm range. Panels of tr eat e d bricks and masonry cement mortar performed 80 -90 per cent as well as control panels of soaked bricks during leakage and bond strength tests, but panels assembled with 1:1:6 cement-lime mortar did not perform nearly as well as their counterparts in the control series.

CONCLUSIONS

A study of small panels assembled with red dry-press bricks having a broad suction range and 4 different mortars, and including

16

-(1) \Vater penetration occurred in all panels assernbled with

the various mortars without a silicone treatment. The beneficial effect of

soaking bricks prior to use, even when they were in a relatively low

initial suction range, was established. Highest bond strength values

occurred in panels assembled with soaked high suction bricks.

(2) Application to the face of test panels of two coats of a

5 per cent mineral spirit base silicone solution e l irninat e d leakage

from all panels.

(3) Results of leakage tests on panels with siliconed bricks

and untreated mortar joints established that most of the leakage in the control series occurred through the bricks.

(4) There are m.1.ny problems associated with the process

of dipping bricks in a silicone solution to achieve a more desirable

IRA range. Relatively weak aqueous solutions must be used. Other

variables include the time of immer sion and the original suction of the

brick. A wide initial IRA range, such as that of the bricks used in

this study, wouldlncrease the problem of trying to reach a desirable final suction range within reasonably narrow limits.

(5) Treatment of bricks with a weak aqueous silicone solution,

while effective in reducing suction to a desirable 1- to 18. 5-gm range, was not effective in reducing leakage in small panels assembled with the bricks and masonry c ern.errt and cement -lime mortar s .

REFERENCES

(l) Davison, J. 1. Leakage and bond strength tests on small panels

assembled with red dry-press bricks and four m o r ta r combinations.

National Research Council, Division of Building Research, DBR

Internal Report No. 215, Ottawa, December 1960.

(2) Ritchie, T. A s m a.l.lvpan e l method for investigating rno i s tu r e

pene-tration of brick masonry. National Research Council, Division of

Building Research, DBR Internal Report No. 160, Ottawa,

September 1958.

(3) Hodgins, P. T. Small brick panel tests at Ottawa. Apparatus and

techniques for study of bond strength. National Research Council,

Division of Building Research, DBR Internal Report No. 175,

(4) Davison, J.1. and J. D. Atkins. Small brick panel tests at Halifax. Preliminary program on leakage and bond strength. National Research Council, Division of Building Research, DBR Internal Report No. 161, Ottawa, November 1958.

(5) Davison,

J.1.

Loss of moisture from mortars upon contact with bricks of various suctions. National Research Council, Division of Building Research, DBR Internal Report No. 173, Ottawa, April 1959.

TABLE I

PROPER TIES OF RED DR Y-PRESS BRICKS. SAMPLES ARE A REPRESENTATIVE

CROSS-SECTION OF OVER-ALL IRA RANGE

IRA Absorption,

_%

Saturation Apparent Bulk Cornp r e s sive

gIT1/ITlin/30 sq in. 24-hr 5-hr Coefficient Porosity, Density, St r ength,

Subrri e r s i on Boiling

_%

gITl/ cc ｰｾ［

11. 0 3.2 4.8 O. 667 10.8 2.24 15.5 4. 5 6.2 0.737 14.4 2. 33 7137.0 24. 0 4. 3 5.8 0.741 13.2 2.28 25.2 4. 7 6. 5 0.732 14. 6 2.26 7293.2 31. 0 4.9 6.5 0.753 14.6 2.24 36. 0 5. 5 7.2 O. 767 16.0 2.22 6859.6 43.8 5.0 6.7 0.749 14.9 2.24 6334. 5 47.0 5. 5 7.2 0.756 17.6 2.24 53. 0 5.5 7.8 0.713 16.6 2. 13 9711. 7 57.0 6. 3 7.9 0.791 16. 1 2.04 60.0 6.8 9.0 0.747 19.2 2. 12 65.0 6.4 8.5 0.758 18. 3 2. 16 6293.1 68.0 7.6 10.0 0.759 22. 6 2.27 74.6 6.2 8.2 O. 765 17.8 2. 18 2696.7 78.0 7.6 10.0 0.766 20.9 2. 10 82.0 7. 1 9.4 0.758 19.8 2. 11 84.5 6.9 9.3 O. 741 19.5 2.09 6087.8 92. 5 7.6 9.9 O. 767 20. 7 2. 10 4362.2 99.6 8.9 11. ₅ 0.776 23.5 2.04 3523.0 101. 0 7.8 10.0 O. 780 21. 0 2. 10 3716.2 Average

6.

1 8. 1 0.751 17.6 2. 17 5819. 5

Sample No. 2 3 4 5 6 7 8 9 10 11

RESULTS OF FREEZE-THAW TESTS ON UNTREATED AND SILICONED BRICKS

UNTREAT ED BRICKS

IRA Failed

gm/30 sq in. /min (Cycle No. ) Remarks

15.5 32 Faint hair line cracking at

16 cycles.

25.2 23

36.0 24 Small hairline cracks at

16 cycles.

43.8 23

53.0 24 Hairline cracking at 16 cycles.

65.0 15 Bad crack developing at

6 cycles

74.6 20 Bad crack eloping at

16 cycles.

84.5 15 Hairline cracking at 6 cycles.

92.5 24 Hairline cracking at 16 cycles.

99.6 11 Hairline cracking at 6 cycles.

101. 1 11 Badly cracked at 6 cycles.

SILICONED BRICKS

66.0 16 Dipped 5 sec in 3% aqueous

silicone solution.

2 66.0 Completed Dipped 10 sec in 3% aqueous

50 cycles silicone solution.

3 66.0 Completed Dipped 20 sec in 3% aqueous

50 cycles silicone solution.

4 66.0 Completed Dipped 30 sec in 3% aqueous

50 cycles silicone solution.

5 66.4 Completed Dipped 60 sec in 3% aqueous

TABLE III

Wt of Weight loss

Sample Original Immersion Final silicone during 50

No. IRA time. IRA absorbed, freeze -thaw

gm/30 sq in. /min sec gm/30 sq in. /min gm cycles

1 66.0 5 0.8 17.2 Failed after 16 cyc l e s 2 66.0 10 0.5 15.0 0.7% 3 66.0 20 0.8 22. 7 0.9% 4 66.0 30 0.6 25.0 1.0% 5 66.4 60 1.0 38.0 1.6%

PANEL ASSEMBLY, LEAKAGE AND BOND STRENGTH RESULTS ON CONTROL PANELS

Panel IRA of Type of Flow, Tap Time, Total Water Bond :\0. Bricks, Mortar 0/0 sec Leakage, Absorbed, Strength,

gm/min/30 sqin. ml gm psi

45. 8 - 71. 0 1:3 masonry 114. 7 Heavy 30 780.0 720 43. 4 cement 2 45.5-7l.2 1:3 masonry 115. 0 Heavy 30 622.0 738 37.8 cement 3 45.2-7l.5 1: 1:6 cement- 116.C Heavy 30 977.0 740 36.2 lime 4 45.7-71.3 1:1:6 cement- 1 15. 5 Heavy 30 887.0 797 48.6 lime 5 45.0-72.0 1:2:9 cement- 117. 0 Heavy 30 710. 0 790 38.2 lime 6 45. 8 - 71. 5 1:2:9 cement- 115. 9 Heavy 30 507. 0 760 23.3 ｾＺｾ lime 7 21. 9 - 30. 0 1: 1:6 cement- 114. 5 Heavy 30 391. 0 595 47.9 ;:: lime 8 21.0-30.0 1:1:6 cement- 1 16. 3 Heavy 30 728.0 662 28.9 lime 9 21.3-29.7 1:1:6 cement- 114. 0 Heavy 30 80. 0 490 29.6 lime 10 ,,0. 5 - 30. 0 1: 1:6 cement- 1

zz.

0 Heavy 30 99.0 544 18.4 lime 11 75.0-86.5 1:1:6 cement- 115. 5 Heavy 30 1662.0 780 41. 4 lime 1/ 76.5 - 85.0 1:1:6 cement- 117. 0 Heavy 30 832. 5 780 44.3 lime " )

-

_{44.0-71.0 1: 3 lime} 114. 0 Heavy 30 1205.0 815 0.2 _:J 26 43.8 - 72.2" 1:3 lime 1 13. 8 Heavy 30 37 11. 0 - 18.5':' 1: 3 masonry 116. 3 Heavy 30 352. 0 540 23. 8 cement '.' 30 378.0 615 24.6 38 12.7-18.0 1:3 masonry 115. 0 Heavy cement

TABLE V

PANEL ASSEMBLY, LEAKAGE AND BOND STRENGTH RESULTS FOR PANELS TREATED WITH SlLICONE ON FACE

Panel IRA of Type of Flow, Tap Time, Total Water Bond

No. Bricks, Mortar

_%

sec Leakage, Absorbed, Strength

gm/min/30 sq in. ml gm psi

13 43.8 - 70.8 1:3 masonry 117.5 Heavy 30 Nil 8

cement

14 43.8 - 70.8 1:3 masonry 118.0 Heavy 30 Nil 3

cement

15 43. 0 - 70. 5 1:1:6 cement- 114.0 Heavy 30 Nil 3

lime

16 44.0 - 70.0 1:1:6 cement- 120.0 Heavy 30 Nil 5

lime

17 43.0 - 72.6 1:2:9 cement- 117.6 Heavy 30 Nil 128

lime

18 43.5-72.0 1 :2:9 cement- 118.0 Heavy 30 Nil 2

.'.

lime

','

114.6

19 22.0 - 30.8 1:1:6 cement- Heavy 30 Nil 2 48.5

,:t lime

20 22. 5 - 30.5 1:1:6 cement- 114.0 Heavy 30 Nil 5 46. 5

lime

21 22.0 - 31. 0 1:1:6 cement- 115.0 Heavy 30 Nil 10 34.7

lime

22 22. 0 - 31. 0 1: 1:6 cement- 114. 0 Heavy 30 Nil 5 28. 3

lime

23 75.7 - 83.0 1:1:6 cement- 114.4 Heavy 30 Nil 5 12.2

lime

24 75.0-82.5 1:1:6 cement- 115.2 Heavy 30 Nil 5 17.2

ｾＧ｣ lime

27 43.5 - 69.0 1:3 lime 116.0 Heavy 30

':<

28 44.0 - 72.0 1:3 lime 113.8 Heavy 30 Nil 3 0.9

PANEL ASSEMBLY, LEAKAGE AND BOND STRENGTH RESULTS FOR PANELS WITH VARIOUS SILICONE TREATMENTS

Panel IRA of Type of Flow, Remarks Total Water Bond

No. Bricks, Mortar _"!o Leakage, Absorbed, Strength,

gm/min/30 sq in. m1 gm psi

2.9

n.3

- 30.7 1:1:6 cement- 112. 0 Face of bricks Nil 250 10. J

lime siliconed

30 23.4

-

31. 0 1:1:6 cement- 112.7 Face of bricks Nil 302 11. 2

lime siliconed

31 45. 7 - 69.5 1:1:6 cement- 113. 0 Face of bricks Nil 1 18 21. 5

lime siliconed

32 46.2. - 68.8 1:1:6 cement- 113.0 Face of bricks Nil 239 L,6.6

lime siliconed

33 46. 2 - 68.3 1: 3 m a son r y 116. 0 Face of bricks Nil 40 16.0

cement siliconed

34 46. 0 - 68.0 1:3 masonry 116. 0 Face of bricks Nil 47 22.6

cement silicone d

35 77.5 - 89. 1 1:1:6 cement- 114.2 Face of bricks Nil 93 20. 4

lime siliconed

36 77.5 - 88.0 1:1:6 cement- 112. 0 Face of br icks Nil 130 16.4

*

lime siliconed

39 44. 8 - 68.0 1:3 masonry 116. 0 Bricks dipped in Nil 65 10. 8

O. 4

-

0.8 cement silicone for 2. min

40 46. 0 ＭＶＹＮＶｾＧ 1:3 masonry 117. 0 BriCKS dipped in Nil 55 7. 1

O. 7

-

1.0 cement silicone for 2 min

41 46.0 - 68. 5" 1:1:6 cement- 113. 5 Bricks dipped in Nil 130 8. 1

0.6 - 1.0 lime silicone for 2 min

42 45. 0 - 68.0':' 1:1:6 cement- 114. 0 Bricks dipped in Nil 125 12. 3

0.5

-

1. 1 lime silicone for 2 min

43 45. 5 - 68.ｏｾＧ 1 :2:9 cement- 117.0 Bricks dipped in Nil 168 6.8

0.3 - 0.8 lime silicone for 2 min

44 45. 5 -69.0" 1:2:9 cement- 116. 4 Bricks dipped in Nil 166 2.3

0.2

-

O.7 lime silicone for 2 min

45 60.0 - 69.ＲｾＧ 1:1:6 cement- 112. 5 Bricks dipped in Nil 150 7.5

O. 7

-

1.7 lime silicone for 10 sec

46 59.0 - 72.5" 1: 1:6 cement- 114.0 Bricks dipped in Nil 140 12.6

O.5

-

1.5 lime silicone for 10 sec

47 30.4 - 40.0':' 1:3 masonry 116.0 Bricks dipped in Nil 65 18. 9

O.5

-

1.2 cement silicone for 10 sec

48 30. 5 - 40.ｏｾＧ 1:3 masonry 115. 8 Bricks dipped in Nil 85 13. 2

0.4 - 1.5 cement silicone for 10 sec

67 47.6 - 59.0':' 1:3 masonry 116.0 Bricks dipped in 1095 745 37.9

2.4 - 13. 0 cement weak silicone for

5 sec

ｾＺＺ

68 48. 5 - 58.2. 1:3 masonry 115. 5 Bricks dipped in 895 727 35.2

3. 0 - 14.0 cement weak silicone for

ｾＺＺＺ 5 sec

69 46.8 - 67.6 1:1:6 cemcnt- 113. 0 Bricks dipped in 967 792 26.5

3.8 - 12. 3 lime weak silicone for

5 sec

70 45. 5 - 48.3':' 1:1:6 cement- 112. 8 Bricks dipped in 1861 740 23.3

3.2

-

14.8 lime weak silicone for

5 sec

ｾＬ _{Top figures are initial brick suctions. Bottom figures are suctions after}

TABLE

VII

Original Immersion Silicone Final

IRA Time Absorbed IRA

gm/30 sq in. /min sec gm gm/30 sq in. /min

67.0 5 22.7 1.7 77.0 10 23.0 1.2 77.8 20 25.5 0.5 79.8 30 26.6 0.9 87.8 60 31. 5

O.

5 90.0 120 35.8 0.8

<tt-0::0 -.J

20

<t z 0:: oC/) ｗｾ

₁₅

t - u u

-wa::

-.JCD W-.J

10

C/)<t z t -_ 0 t-C/)lL.

5

ｾｯ u Ｍｾ ｡ＺＺｾ CD

₀

r-- r, -r--

-... r -I- ... rr

-n

0 0 0 0 0 0 0 0 0 0 N f'0 V co U> l"- ex> m 0 0 I

,

,

I I

,

I

,

-

_I 0 0 0 0 0 0 0 0 ₀ N f'0 ｾ lO U> l"- ex> m

-IN ITI AL RATE OF ABSORPTION

( GR AMS

PE R MIN PER 30 SO I N. )

FIGURE

I

IRA DISTRIBUTION OF 471 RED

DRY-PRESS BRICKS

Figure 2(a)

High suction (85 gm), left, and low-suction (7 gm) , right, bricks in sodium sulphate solution. Note efflorescence on high suction brick.

Figure 2(b)

Silicone-treated bricks in suction range 6. 5 to 90.0 gm in sodium sulphate solution. Note absence of efflorescence.

-.'----

ｾＮ u 90 t- . / .,..--. < , / / .

ｾ ｾｾ

r-1

/ / . / .

; 60 • -SILICONED ｾ 50 . ex: • o 40 .

I

ｾ

30

I

IRA 81·5 GM ｾ 20

Ii.

o 10 -I I I I

o

10 20 30 40 TIME, DAYS

FIGURE 3 (A)- TRANSPIRATION

OF MOISTURE FROM

SILICONE-TREATED BRICK- 5 SIDES

100 ｃｏｎｔｒｏｌＭｾＮ _ ｾＮ u 90 y.'•. ｾ 80 /' -5 70

I .

ｾ

. .

; 60

-i

/

ｾ

50

L

.

ｾ

40 - .../SILICONED u... o 30 - . / 20 / ｾ • IRA 80-83GM 10 ;"

o

20 40 60 80 100 120 140 TIME, DAYS

FIGURE 3(B}- TRANSPIRATION

OF MOISTURE FROM

SILICONE-TREATED BRICK- I SIDE

350

....J

300

ｾ ｾ

250

w

(.!)

ｾ

200

<t W ....J

150

-1

;: 100

0

₇₅

...

50

25

0

I

o

o ....:-0_0 - -0

10 20 30 40 50 60

70 80 90 100

IRA OF SRI CKS

GRAMS

PER MIN PER

30

sa

IN.

FIGURE 4

LEAKAGE TOTALS FOR INDIVIDUAL

BRICKS

...J ｾ

1000

...

w (,!) <t ::.:::

₇₅₀

<t

ｾ

W ...J l.JJ ...J

500

Ｏｾ

<t rt')<J l - .. >-0 - 0 : :_Z I-

₂₅₀

₀ (J)

«

:e

FIGURE

5

COMPARISON

OF LEAKAGE

RESULTS FOR

CONTROL PANELS -

BRICK

SUCTION

45-70

GM

Figure 6

Typical mortar joints from control panels. Bricks, suction 45 to 70 gm, were soaked before use.

Left - 1:3 masonry cement. Centre - 1:1:6 cement-lime.

1250

...

ｾ

1000

«

ｾ

ｾ

750

....J ....J

ｾ

500

o

....

250

PANELS

FIGURE 7

EFFECT OF BRICK

SUCTION

ON

MOISTURE

PENETRATION

Figure 8

Typical mortar joints from control panels assembled with l: l: 6 cement -lime mortar and

Left - bricks in suction range 20 to 30 gm used dry; Centre - same bricks soaked before use;

coats of 5 per cent mineral spirit base silicone solution were applied to the face of the panels which are a combi-nation of 1:1:6 cement-lime mortar and

Left - bricks in suction range 20 to 30 gm used dry; Centre - same bricks soaked before use; and

1:3

MASONRY

CEMENT

MORTAR

r--ll

I

1:1:6

ｃｅｍｅｎｔｾＭＱ

r--L1ME MORTAR

I

50

300

..

Cl lJJ

_eo

200

0::

o

ｾ

150

<X 0:: lJJ

100

I--<X ｾ ....J

250

ｾ

22-31

45-70 77-89 45-70

SUCTION OF BRICKS IN PANELS

( GM/30 S

Q

IN / MIN )

FIGURE 10

COMPARISON OF WATER ABSORBED

DURING TEST. BRICKS OF

VARIOUS

SUCTION - TWO MORTARS

of differ ent suction levels and I: I : 6 cement -lime and I: 3 masonry cement (right centre) mortar. Face of these bricks received two coats of 5 per cent mineral spirit base

silicone solution before use. Note Infe rio r bonding along edge of bedding area due to silicone treatment.

Figure 12(a)

Typical mortar joints panels assembled with masonry cement mortar.

Top - low suction bricks (11.0 - 18. 5 gm).

Bottom - bricks of original suction 45.0 to 70.0 gm

pretreated by immersion for 2 min in a 3 per cent aqueous silicone solution.

lime mortar and bricks of original suction 45. 0 - 70.0 gm pretreated by immersion for 2 min in a 3 per cent aqueous silicone solution. Final suction O. 3 to 1. 1 grn ,

Top - 1:1:6 cement-lime mortar. Bottom - 1:2:9 cement-lime mortar.

Figure 13

Typical mortar joints from panels assembled with bricks pretreated by immersion for 10 sec in a 3 per cent aqueous

silicone solution, suction range O. 4 to 1. 7 gm.

Top - bricks with original suction 60.0 to 72. 5 gm and 1: 1:6 cement -lime mortar.

Bottom - bricks with original suction 30.0 to 40. 0 gm and 1: 3 masonry cement mortar.

face. This panel was assembled with bricks whose original suction range was reduced from 47.6-59.0 gm

to 2.4-13.0 gm by a 5-sec immersion in a weak (f0. 09)

aqueous silicone solution. A masonry cem ent mortar

Figure 15

Centre and right - typical mortar joints from panels assembled with bricks reduced to 2.4- to 14. 8-gm suction range by 5 -sec immersion in a weak (approxi-mately 0.09%) aqueous silicone solution and 1:3

masonry cement mortar (centre) and 1:1:6 cement-lime mortar (right).

o

o

o

o

o

o

o

o

o

o

o

-lJ..

2

ｏｌＮＮＮＮｬＭｬＭｌＮＮＮｉＮｾｬＮＮＮＮＮＮＮｌＮＮｉＮＭｌＮＮｌＮｾｌＮＮＮｊＮＮＮＮＮｌＮＮＮＮｌＮＮｌＮＮｌＮＮＮｊＮＭｉＬＮＮＮｊＭＮｌＮＮＮＮｌＮＮＮｌＮＮＮｌＮＮＮＮｬＭｉＮｾＢＭＭＧ

45·0

50-0

55·0

60·0

65·0

70-0

75-0

ORIGINAL IRA {GM/30SQ IN./MIN}

<t

a:::

6

0

o

0

cP

;;.

4

0

z

00 o

8

-18

_z

ｾ

16

<,

ｾ

14

C1 0

(J)12

_{0 _} 0

o

t()

ｾ

10

(!)

FIGURE 16

REDUCTION IN IRA FOR BRICKS

IMMERSED IN AQUEOUS SILICONE

SOLUT ION