Note: Descriptions are shown in the official language in which they were submitted.
I
--1--
SHEET MATERIAL OF FIBRE-REINFORCED CEMENT
This invention relates to sheet material of fibre-reinforced
cement, which Jay be flat or of profiled cross-section, en
corrugated. Such material is suitable for use as building panels,
for roofing. The flat material is particularly suitable for use as
roofing slates.
Sheet materials of cement reinforced with asbestos fires have
been known Pro many years and provide a lightweight roofing material
which is both weather-resistant and fire-resis~ant. There is now a
need to replate asbestos as a component of such materials, but the
product obtained as a result of such replacement must be substantially
equivalent to the existing asbestos-cement materials in all their
desirable properties. The materials must also be capable of being made
on existing asbestos-cement equipment so as to avoid the capital cost
of replacing or drastically altering such equipment.
The use of glass fire as a replacement for asbestos fire in
such equipment has been the subject of considerable research over the
past 10 to lo years. The problems originally encountered, which are
discussed for example in our US Patent Specification No. 1,543,951,
have been overcome to the extent that it is now possible to formulate
glass fibre-con~aining cement slurries which can be run on
asbestos cement machines, by the measures descried on
Specification No. 1,543,~51. This ability is not necessarily
accompanied by the production of a product with adequate properties for
a particular purpose.
Sheets or panels for use in building generally require to have a
mean modulus of rupture (bending strength of at lest 16 No and a
density of at least 1.3 g.cm~3. For roofing slates, the requirements
: '
, .. .. . . . ...
~;22~5~3~
are more stringent. Presently available asbestos cement roofing
slates, otherwise known as compressed asbestos cetnent slaves, have a
smooth surface which generally carries an acrylic coating of the
desired killer and are required by current US standard
specifications to have an average minimum mean modulus of rupture MY
of 22.5 N.r~n~2 A minimum density of 1.8 g.cm~3 is advisable to avoid
porosity which could result in frost damage in roofing slates.
Simple replacement of the asbestos content of asbestos-cement
lo sheet materials by glass fire in chopped strand form does not produce
materials of equivalent appearance, because the chopped strands tend to
be visible in or to project from the surface, resulting in a surface
finish which is either unacceptable when the usual amount of coating
has been applied or requires so much decorating material to produce an
acceptable coating as to cause an unacceptable increase in cost.
Furthermore such simple replacement ox the asbestos by chopped strand
lass fire does not enable one to achieve equivalent strengths with
economic amounts of glass fire, due to uneven distribution of the
glass fire in the cement and attack on the glass fire by the alkalis
in the cement. In our US Patent Specification No. 1,543,951 we have
described a method of manufacturing an asbestos-free fibre-reinforced
cement composite material from an aqueous cement slurry incorporating
both chopped strands of glass fire and single filaments of inorganic
non-crystalline material, which latter Jay be produced from continuous
filament chapped glass fire strands which separate or fulminates on
contact with the cement slurry. If glass fire in such single filament
phony produced from filamentised chopped strands is used as the sole
fibrous reinforcement, a smooth surface finish can be obtained. The
strength problems are aggravated, however, because the single filaments
are open to attack by the alkalis in the cement and there is also
; difficulty in achieving an adequate bond between the fire and the
matrix.
I, , . ,.. .. ..
~2~5~
--3--
To improve the strength of glass fire reinforced cement
products, various proposals have been made for the incorporation ox
reactive silica in different forms. For example, US Patent
Specification No. 1,402,~5 (N.R.D.G.) relates to a glass fire
reinforced pozzolanic cement product comprising a cement matrix
containing at least 10~ by weight of a pozzolana which is a silicate
glassy material capable of reacting with calcium hydroxide and thereby
setting into a hard strong material) and fires of an alkall-resistant
silica/zirconia glass containing at least 6 mol. % ZrO2. The
spectfiçation states that a very desirable increase in the strength of
the composites may be obtained by controlled heat treatment which
accelerates the attainment of stable properties and ultimate strength
and which may take the form of at least two days under water at a
temperature of e 60C to ~0C. One of the preferred pozzolanas
described is pulverized fuel ash PEA used in amounts from 15~ to 40
by weight. US Patent Specification No. 1,421,556 TOKYO Construction
Materials Limited) describes the production of cement board products
reinforced with a mixture of long and short staple alkali resistant
vitreous ~ibres, I chopped glass fire strands and milled mineral
fires, with cellulose fire and sufficient silica, in the form of
diatomite, to react with the free lime liberated during the hydration
of the cement. The board products are autoclave to assist the
reaction. European Patent Application No. 68,742 (Cape Boards Panels
Limited) relates Jo shaped articles such as boards and sheets for
cladding and roofing, and describes a manufacturing process using an
aqueous slurry comprising, on a dry weight basis, SO to 90~ cement, UP
to 40% highly reactive pozzolanic silica and I to 15~ cellulose
fires. Reaction occurs between the cement and the silica by air
curing. The specification states that mixtures of highly reactive
pozzolanic silicas, e.g. volatilized silica and diatomite~ may be used
and that glass fires may be incorporated in addition to the cellulose
fires. US Patent Specification No. 2,~48~330B (Rockwell
International A/S) describes a method ox preparing a fire reinforced
so
--4--
cementitious plate from an aqueous slurry of cement and fires selected
from the group consisting of synthetic mineral fires, natural organic
fires and inures thereof, wherein a fine material (specifically a
filter dust produced as a product in the manufacture of silicon or
silicon alloys by an electrothermal process and consisting essentially
of volatilized silica) having an average particle s key lower than that
of the cement particles is incorporated in the slurry to reduce the
loss of fine cement particles and to neutralize alkaline products in
the mixture, thus inhibiting alkaline degradation of the mineral
lo fires. It is said that the amount of fine particles should preferably
not exceed 15~ by weight based on the weight of the cement because high
concentrations of fine particles reduce the rate at which excess water
is removed from the slurry. Finally in our own US Patent
Specification Nut 1,565,823 we disclose the use of reactive silica in
the form of pulverized fuel ash PEA or a fine silted flour such as
diatomite or ELK EM silica which is a volatilized silica, which were
found to have a synergistic effect with the particular size
compositions described in that specification for application to
alkali-resistant glass fires for reinforcement of cement. Proportions
of 10~ to 40~ of the reactive silica were shown to produce a further
improvement in durability of the sized glass fire strands incorporated
in the cement We believe that the reactive silica assists in bonding
the glass fire into the cement matrix as well as reacting with alkalis
in the matrix.
Our own recent investigations indicate that the various forms of
reactive silica have different effects on the early strength and on the
long term strength of the composite materials. This is particularly
the oases where slays fire In single filament form is used for
reinforcement. Our investigations have shown that if one uses
filamentised dispersible glass fire strands as the sole fibrous
reinforcing material, it is essential to use a mixture ox two different
reactive silicas, namely pulverized fuel ash and vslatilised silica,
within specific ranges, Jo order to be able to produce flat sheet
5~3~
material suitable for use as building panels on existing asbestos-
cement machinery, with both a good start strength and good long term
durability, which can oven be accompanied by an increase of strength
beyond the initial strength. Use of the volatilized silica without the
pulverized fuel ash gives a good start strength but on subjection to
simulated aging tests the material shows a marked falling off in
strength. Polarized fuel ash on its own without the volatilized
silica gives a poor start strength and a poor overall matrix strength.
According to the invention, therefore, a sheet material is
provided, formed of a fibre-reinforced cement composition comprising,
in percentages by weigh of solids:-
Ordinary Port land cement 50 to 71P
Pulverized fuel ash 14 to 40
Volatilized silica containing at least 86
by weight Sue) 5 to 12~
Filamentised chopped glass fire strands to 7X
in which these components constitute at least 90~ by weight of the solid constituents of the composition and in which, when the cement
composition comprises less than I by weight of volatilized silica, the
volatilized silica is of a grade containing more than 86~ by weight of
Sue, and when the cement composition comprises only I by weight
vola~ilised silica, the volatilized silica is of a grade containing at
least 94~ by weight Sue, the sheet material having a minimum average
modulus of rupture of 16 N.mm~2 and a minimum density of 1.3 g,cm~3.
The combination of polarized fuel ash and volatilized silica in
the proportions set out above results in a product with a satisfactory
initial strength and long term durability, accompanied by an increase
of strength beyond the initial strength after curing. The use of
filamentised glass fire produces a smooth surface, as required where a
coating is to be applied, by avoiding the occurrence of projecting
strand ends as would occur if integral chopped strands were used.
I
--6--
The term "volatilized silica" is used herein to describe the
material (otherwise known as micro silica or silica fume) which is
commercially produced as a by-product during the manufacture of silicon
or silicon/metal alloys by an electro-metallurgical process. Its
chemical composition can vary slightly according to the characteristics
of the process and of the main product, but it normally contains at
least 86~ by weight Sue and 0.1 to 0.7~ Sick Grades of lower purity
are not suitable for use in the present invention because the quantity
then required causes problems in de-watering the cement sheet material.
Purer grades of relatively carbon-free volatilized silica are
available, containing at least 94~ Sue and around 0.1~ Sick It has
been found that these purer grades have a higher surface activity and
hence can be used in smaller quantities than the normal grades, in the
present invention. If the proportion of volatilized silica used in the
sheet material of the present invention is less than I by weight, the
volatilized silica must therefore be of a grade containing more than
86% by weight Sue and where the minimum proportion of 5g of
volatilized silica is used, the latter material must contain at least
94~ by weight Sue-
The preferred percentage of filamentised chopped glass fire
strands in the sheet material is from 3 to I Although the percentage
may be as low as 2%, problems can then arise in handling the green
(i.e. uncured) sheet. With percentages between I and I difficulties
can be encountered in ensuring uniform dispersal of the glass fires in
the cement matrix.
The balance of the composition may comprise up to I by weight of
cellulose pulp, which is included as a processing aid to assist
drainage. Up to 5% by weight of a plasticizer, for example ball clay,
bentonite or talc, may also be incorporated to improve the plasticity
of the material prior to curing. Small quantities of conventional
dispersing and flocculating agents may also ye used.
The ~ilamentised strands are preferably made of an
i5~3g
--7--
alkali-resistant glass composition containing a least 6 mol. ZrO2.
For example, the glass fire strands may be of the type described and
claimed in our US Patent Specification No. 1,290,528 and sold by
Fjbreglass Limited under the Trade Mark Cem-FIL, and their composition
may be substantially, in milks
Sue 69
Zra2 9
Noah 15.5
Coo 6.5~
The invention further provides a flat sheet material suitable for
use as roofing slates, formed of a fibre-reinforced cement composition
comprising, in percentages by weight of solids:-
Ordinary Port land cement 50 to 70
Pulverized fuel ash 20 to 40
; Volatilized silica (containing at least
86% by weight Sue) 8 to 12~
Filamentised chopped glass fire strands 2 to 5%
these components constituting at least 98~ by weight of the solid
: 20 constituents of the composition, the balance (if any) consisting of
compatible constituents, the sheet material having a minimum average
modulus of rupture of 20 N.mm~2 and a minimum density of 1.8 g.cm~3
and a smooth surface for reception of a coating.
Tests on roofing slates made from such material have shown that
they have a considerably better resistance to repeated freezing and
thawing and general weathering than conventional asbestos cement slates.
::
the invention also resides in a method of making a sheet material
: of fibre-reinforced cement comprising the steps of mixing an aqueous slurry whose solid contents i include:-
Ordinary Purloined cement 50 to 71
'
I_ .. . .. . . . ..
1;~2
Pulverized fuel ash 14 to 40
Volatilized silica (containing at least 86~
by wet go So Ox) 5 to 1 2X
Dispersible chopped glass fire strands 2 to I
in which these components constitute at least 90% by weight of the
solid contents of the slurry and in which, when the slurry comprises
less than 8% by weigh: of volatilized silica, the volatilized silica is
so a trade containing more Han 86~ by weight sj2, and when the slurry
comprises only I by weight of volatilized silica, the volatilized
lo silica is of a grade containing at least 94g by weight Sue, the mixing
being carried out so as to disperse the chopped glass fire strands
into swig filaments, depositing a famine from the slurry on to a
pheromones surface, superimposing a plurality of said laminate on one
another to build up a sheet of cementitious material, and curing the
sheet.
In order to avoid mechanical damage to the glass fires during
processing, the slurry mixing may be carried out by first mixing the
cement pulverized fuel ash and silt cay with water in a hi go shear mixer
and then adding the dispersible chopped glass fire strands under low
20 shear mixing conditions. Alternatively the slurry mixing may be
carried out by first mixing the cement and pulverized fuel ash and
optionally some of the silica with water in a high shear mixer and then
adding the silica or the remet nuder of the silica with the dispersible
chopped glass fire strands under low shear mixing conditions.
The deposition of the famine and the building up of the sheet can
be carried out on an asbestos-cement machine of the Bell or Hatschek
type.
The sheet may be shaped to a desired cross-sectional profile
before curing, eye. so as to provide it with contiguous or spaced
30 corrugations. The sheet may, for example, be shaped by application of
a vacuum profiling head of known type, or by placing it on a former
, .
_ . .... . . . . . . . .. . ., ... .. . .. , . ...
~2~5~3~
plate whose upper surface has the desired cross-sectional profile and
allowing the sheet to collapse into contact with said surface. In the
latter case, a second former plate may be placed over the sheet to
complete the shaping.
The sheet may be cured at a temperature in the range from 6~C to
90C, preferably from 70C to 80C, for 24 hours and then stored at
ambient temperature for at least 7 days to complete the cure. Such a
high temperature initial cure assists in ensuring the long term
durability of the finished product, while the presence of the
pulverized fuel ash and vola~ilised silica enables the filamentised
glass fire to survive the cure in sufficient quantity to provide
adequate reinforcement.
The sheet may be pressed to de-water it before curing, eye. by
placing a stack of such sheets with interleaving plates in a press and
subjecting the stack to pressure to expel water.
For making roofing slates, the shapes of the roofing slates are
preferably stamped out from the sheet before it is pressed and cured
and the slates are separated after curing.
Specific embodiments of the invention will now be described in
more detail by way of example.
Sheet material in accordance with the invention, suitable for
making roofing slates, can be made on conventional asbestos cement
machines ox either the Bell type, as described in Us Published Patent
Application No. AYE, or of the well-known Hatschek type. In
both these machines, several laminate (typically eater superimposed
to on a sheet of glass ire reinforced cement with 3 thickness of 4
to S mm after pressing. In the case of the jell machine, a glass fire
containing aqueous cement slurry is transferred through a doctor roll
system on to a moving web or belt where it is de-watered to around 25~
water content by suction. The famine so formed is transferred from the
* Trade Mark (Bell Maschinen Fiberlike AGO. )
65~39
-10-
belt on to a rotating drum. When sufficient l~minae have been
superimposed on one another on the drum to build up a sheet of the
desired thickness, the sheet is cut off the drunk. In the case of the
Hatschek machine the famine is deposited on a rotating sieve and then
transferred to a belt and thence to a drum. Again the sheet is cut off
the drum once a suffusion number of laminate hale been superimposed to
build up the required thickness.
The subsequent processing is virtually the same in each case. A
cutter us used to stamp out the shape of several slat rectangular
roofing slates with their fixing holes on the sheet. The states my be
of the standard dimensions of 600 x 300 mm, or 500 x 25G my, for
example. The sheet is placed on a steel interleaving plate and
transferred to a stack of similar sheets. When a sufficient number of
stamped-out sheets have been accumulated in the stack, it is passed to
a press where the sheets are further de-watered by pressure to a final
water content of about 20X. The interleaving plates ore then removed
and the sheets are cured at 80C for 24 hours and finally stored at
ambient temperature for seven days. The individual roofing slates can
then be detached from one another and are ready for coating if desired.
The following specific Examples I and II relate to production of
roofing slates in the above manner on a Bell machine.
Example I
An aqueous slurry was formulated having the fang composition
expressed as parts by weight of solids:-
Ordinary Paranoid cement 61
Pulverized fuel ash
Yolatilised silica (86~ by weight Sue) 9
Filamentised chopped strands of alkali-resistant
glass fire as sold under the Trade Mark "Cem-FIL"
by Fiberglass Limited I
Cellulose pulp 2X
:.,
65~39
Conventional dispersing agents, flcccula~ing agents etc. may also
be incorporated in small quantities (less than 0.1~ in known manner.
The glass fire strands were substantially 3 mm in length, made
up of filaments substantially 20~ in diameter sized with a size
composition designed to ensure that the strands disperse or fulminates
in contact with the slurry. Examples of such sizes are disclosed in
US. Patent Specification No. 3,948,673. The composition of the glass
fire was, in mol. X:-
Sue 69%
Zrû2 9
Noah 15.5
Coo 6.5~
After curing as described above at 80C for 24 hours and storage
for seven days at ambient temperature, the slates were tested to
ascertain their bending strengths in both the longitudinal and
transverse directions relative to the direction of movement of the belt
of the Bell machine; they were also tested for impact strength.
Further sample slates were subjected to accelerated aging by total
immersion in water at 70C for sixteen days, simulating approximately
30 years natural weathering, and then retested. The results obtained
we-e as follows--
--1 2--
Table 1
_ . . . _ _ __
Long mu- Trays- Mean
do net verse
__ _
Limp t of Propriety on-
Immediately amity ~N.mln~2) 22.9 12.6
Modulus of Rupture
after (N.n~n~2~ 25.8 15.1 2û.5
Impact strength
cur ( Nmm. no 3 . 2
Limit of Proportion-
After amity (N.mm~~ 28.7 16.0
Modulus of Rupture
accelerated (N.n~n~2) 29.7 17.3 23.5
Impact Strength
age no ) _ - 2. 4
Density of slates: 1.95 y.cm~3
-13-
It will be seen that the mean modulus of rupture was over 20
N.mm-2 and increased after aging.
Example II
Roofing slates were made up as described above from an aqueous
cement slurry having the following composition expressed as percentages
by weight of the solids content:-
Ordinary Port land cement 61
Pulverized fuel ash 24,5
Volatilized silica (8Ç~ by weight Sue) 9
Filamentised chopped glass fire strands
(as in Example 1) 3.5X
Cellulose pulp 2g
Dispersing agents, flocculating agents etc.~O.l~
The slates produced were tested as in Example I with the following results:-
Tall e 2
. Long tug Trays- Mean
Jo _ dial _ verse
Limit of Proportion-
Immediately amity (N.mm-2)24.6 15.9
Modulus of Rupture
after ~N.mm~2) 25.8 16.5 21.2
Impact Strength
cure 2. 9
Density of slaves: 1.90 g.cm~3
....
Swahili
-14-
ROQfjng slates were made up as in Examples I and II from an
aqueous slurry having the following solids contents, by weight;-
Ordinary Port land cement 7
Pulverized fuel ash 14
Volatilized silica (86~ by weight Sue) 11
Filamentised chopped glass flare strands
(as in Example I) 3.
Processing aids cellulose pulp, dispersing
agent, flocculating agent) 1.5
Comparative Example IV
For comparison, a further set of slates were made up from slurry made up as in example III but with the pulverized fuel ash
replaced by limestone flour tCaC03).
Comparative Example Y
For further comparison, roofing slates were made from a slurry
whose solids contents were, by weight:-
Ordinary Port land cement 69
Pulverized fuel ash 6
Volatilized silica ~86~ by weight Sue) 20
Filamentised chopped lass fire strands
(as in Example I) 3
Processing aids (cellulose pulp, dispersing
agent flocculating agent) I
: Results of tests on the roofing slates of Example Ill and
: Comparative Examples IV and Y were as follows:-
, ..... , _.. .. . . .. . . .. . .... .
5~9
-15-
Table 3
.
Density LOP MOW Impact Specific
MOW
III Immediately
after
cure 1.7 12.3 15.1 3.8 8~9
After accelerated
aging 1~7 16.0 17.0 2.7 1~.1
-- _ _
IVY In~ediately
after
cure 1.7 12.6 15.4 4.0 Sol
After accelerated
aging 1.7 11.1 11.4 1.0 6.7
V Immediately
after
cure 1.5 8.7 11.8 I 7.g
....~
: It will be seen that the replacement of the pulverized fuel ashby limestone flour in Example IVY gave much reduced strength after
j aging, while Example Y with too much silica and insufficient
- 20 pulverized fuel ash had poor strength even immediately after curing.
Example VI
This example relates to the production of a flat sheet of
: glass-fibre reinforced cement on a Hatschek motion or use as a
-16-
building panel, for which a minimum mean modulus of rupture (MOW) of 16
N.~n~2 and a minimum density of 1.3 g.cm~3 may be specified.
The aqueous slurry had the following composition, in parts by
weight:-
Ordinary Port land Cement 60,5
Pulverized fuel ash 24.5
Yolatilised Silica (86~ by weight Sue
Dispersible chopped glass fire strands 3.5
Processing Aids (cellulose pulp, dispersing
lo agent, flocculating agent) 3.5~
The glass fire strands were as described above in detail in
Example I.
Sheets were formed in conventional manner on the Hatschek
machine. Some of these sheets were profiled (i.e. corrugated) by use
of a conventional profiling head and deposited on a correspondingly
shaped former plate for curing. Other sheets were pressed to de-water
them to a water content of 20~ before curing. In each case the sheet
was then cured at ~0C for 24 hours and stored for seven days
thereafter at ambient temperature. Samples cut from the sheet were
tested as described above to ascertain their bending strengths, in both
the longitudinal and transverse direction relative to the movement of
the cylindrical sieve and belt of the Hatschek machine. They were also
tested for impact strength. The results obtained were:-
i8~3
-17-
Tall e 4
Profiled unpressed sheet: Dry density 1.4 g.cm-3
Longitudinal Transverse Mean
LOP 13.8 12.6 13.2
MOW 22.4 16.7 19.6
¦ Pressed flat sheet. Dry density 1.7 g.cm~3
I Longitudinal Transverse Mean
! LOP 18.7 16.9 17.8
I MOW 31.8 19.8 25.8
¦ Impact - - 3-5
Further trials have been made in the laboratory to investigate
the range of possible compositions for the sheet material for making
roofing slates. In such laboratory trials, with normal equipment, it
is difficult Jo produce as thin a product as on the full scale machines
and it is not possible to build up the slate as a series of laminate or
to obtain the same product density. The results obtained are useful in
a comport sense though the absolute values obtained cannot be
translated directly into values which would be obtained using similar
formulations in full scale operation on a Bell or Hatschek mashing.
The laboratory trials were carried out by forming a slate, 30 cm square
and 8 mm thick, and de-watering it by simultaneous application ox
pressure and suction. The slate was then cured a 60C for 24 hours
and the strengths measured as in the preceding examples. The results
are set out in Table 5, which also includes the composition of each
slate, the length of the glass filaments employed and a figure for the
modulus of rupture corrected for the lower density of the slate as
opposed Jo that to be expected for a slate produced from the same
composition in full scale operation. In all these samples, volatilized
silica of at least 86S by weigh S10z content was used.
-18-
Table S
Sample OPT PEA Vale- Glass Film- Solely- Den- LOP MOW Imp- Specs
No. X lilt- Fire mint lose, sty act ific
sod % 1 length do super sire- MOW
So 1 i cay slants, ngth ( Con-
phlox- feat-
tents Ed for
& C. Dens-
ivy
I_
: 10 1 I 25 3.5 6 mm ~.~ 1.68 7.3 13.1 2.'j7.~
2 59 14.5 ills 3.5 6 nllR 1.5 1.72 1~.9 16.93.~ I
3 69 14.5 11.5 3.5 3 on 1.5 1.72 18.3 2~.34.0 11.7
4 62 28.5 5.0 3.0 3 no 1.5 1.59 11.4 12.5~.3 7.9
So 24 9.5 3.0 3 no 1.66 15.4 l~.B3.3 lû.l
6 57 29 9.5 3.0 3 no 1.5 1.64 15.3 16.73.5 10.2
7 I 27 11 3.5 3 mm 1.5 1.67 15.2 16.64.7 9.9
8 I 32 11 I 3 nun 1.5 1.63 13.7 15.B4.9 9.7
9 71 14 11 2.5 6 nun 1.5 1.68 14.g lb.l3.4 9.6
81 0 lo 3.0 3 errs 6.0 1.55 1~.0 14.53.2 9.4
Jo
In the above Table, OPT = Ordinary Port land cement, PEA = Pulverized
fuel ash, LOP = Limit of Proportionality and MOW = Modulus of rupture.
Of the ten samples tested samples 1 and 10 are included only as
comparative samples which are outside the scope of the invention
because they contain no volatilized silica or pulverized fuel ash,
respectively. Sample 4 is also outside the scope of the invention
because the convent of volatilized silica is too low for use of a
material of only 86~ by weight Sue content. The strengths obtained
could be increased by increasing the temperature of cure and would
certainly be increased in full scale operation due Jo the better
distribution of the glass fire which arises prom the formation of
individual laminate on the jell and Hatschek machines.
* Trade Mark
-l 9-
Table 5 demonstrates what if the volatilized silica is not
present (sample 1) the overall strength of the matrix is poor compared
with those samples containing o'er 8% of the volatilized silica.
Sample 10 shows what in the absence of pulverized fuel ash, the initial
strength is low as compared with those samples containing equivalent
amounts of volatilized silica; products made from such a composition,
when subjected to artificial aging, show a further falling off in
strength. The strength of sample 4 would be substantially increased of
volatilized silica of 94~ Sue convent were used in accordance with the
invention.
To demonstrate the importance of using volatilized silica of 94Z
Sue content rather Han 86~ Sue content when the proportion of
volatilized silica in the material is relatively low, a series of
samples were made in the laboratory differing only in the type and
proportion of volatilized silica, and tested for LOP and MORN with the
following results. Two grades of Yolatilised silica containing 86~
Sue and one containing 94~ Sue, identified in the Tables as Grades 1,
2 and 3, were used.
Table PA
! LOP MOW
I
owe Volatilized Silica (86~ So?) (Grade 1) 12.6 15.3
6 2 ED I 11 11 1 1 . 1 1 3 . 4
5-~ if if if 10.4 12.4
table 6B
,, _ _ _ _ _ ............. .. . . . .. _ _ _ .
owe Yolatilised Silica (86~ Sue) (Grade 1) 10.6 13.2
81D 11 11 grade 2) 10.8 13.6
owe ,. ., ,. 10.3 12.5
Lo
-20-
Table 6C
- . _
LOPMOR
_ I
owe Volatilized Silica (86~ Sue) (Grade 1) 10.6 12~2
8' Volatilized Silica (94Z Sue) grade 3) 9.6 12.5
aye ., ;. 9.4 12.0
Lowe .. 9.5 12.0
It will be seen that reduction of the silica content from owe Jo
owe was accompanied by a substantial loss of strength where 86Z Sue
content volatilized silica was used, but that with the 94Z Sue content
volatilized silica no appreciable loss of strength resulted.
