IMPROVEMENTS IN THE MANUFACTURE OF MORTAR AND DWN SAD DHSS ROSE CONCRETE, AND OF BRICKS OR BLOCKS FOR BUILDING PURPOSES
Year: 1870

page_text: LETTERS PATENT to Henry Young Darracott Scott, of Ealing, in the
County of Middlesex, Lieutenant-Colonel Royal Engineers, for the
Invention of "IMPROVEMENTS
IN THE MANUFACTURE OF MORTAR AND
DWN SAD DHSS ROSE D
sealed the 9th August 1870, and dated the 26th April 1870.
PROVISIONAL SPECIFICATION left by the said Henry Young Dar.
racott Scott at the Office of the Commissioners of Patents, with his
Petition, on the 26th April 1870.
I, HENRY YOUNG DARRACOTT Scorr, of Ealing, in the County of
Middlesex, Lieutenant-Colonel Royal Engineers, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF
MORTAR AND CONCRETE, AND OF BRICKS OR BLOCKS FOR BUILDING PURPOSES," to
be as follows:-
My Invention has for its object the manufacture of mortar and
concrete of a highly cementitious character, and the converson of the
same when required into bricks or blocks for building purposes.

page_text: In carrying out my Invention I take sulphate of lime or other
sulphate in a fine state of division, or sulphuric acid, and mix the same
with water. To this mixture I add lime in a finely divided state and
agitate the whole together; I then add sand, burnt clay, shingle, gravel,
or equivalent substances thereto until the whole is brought to a stiff
consistency. The compound thus prepared is applicable to general
building purposes, or it may be compressed in moulds so as to form
from it bricks or blocks.
The proportions which I employ are, in ordinary cases, 1 part by
weight of sulphate of lime and 20 parts of lime; and to this mixture
I add variable proportions of sand or burned clay or their equivalents,
according to the uses to which the compound is to be applied. I some-
times add also 4 parts of Portland cement, more or less, whereby I am
enabled to increase greatly the proportion of clay or sand or equivalent
materials without deterioration to the quality of the manufacture.
The mortar or concrete should be mixed as it is required to be used,
and the bricks or blocks as they are removed from the moulds are
stacked until sufficiently indurated for use.
When bricks are made by the ordinary process of burning, and the
clay used is found to contain lime in quantities detrimental to the
stability of the brick, I intimately mix with such clay before moulding
a small proportion of a cheap sulphate or sulphuric acid, and thereby
greatly improve the quality of the brick.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Henry Young Darracott Scott in the Great Seal 2
Patent Office on the 26th October 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
YOUNG DARRACOTT SCOTT, of Ealing, in the County of Middlesex,
Lieutenant-Colonel Royal Engineers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her 3
Letters Patent, bearing date the Twenty-sixth day of April, in the year
of our Lord One thousand eight hundred and seventy, in the thirty-third
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Henry Young Darracott Scott, Her special licence
that I, the said Henry Young Darracott Scott, my executors, adminis- 3

page_text: trators, and assigns, or such others as I the said Henry Young Darracott
Scott, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention
for "IMPROVEMENTS IN THE MANUFACTURE OF MORTAR AND CONCRETE, ANd of
BRICKS OR BLOCKS FOR BUILDING PURPOSES," upon the condition (amongst
others) that I, the said Henry Young Darracott Scott, my executors or
administrators, by an instrument in writing under my, or their, or one
of their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next and immediately after the date
of the said Letters Patent.
NOW KNOW YE, that I, the said Henry Young Darracott Scott, do
hereby declare the nature of my said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained in
and by the following statement (that is to say) :-
My Invention relates to an improved method of compounding with
quick lime cementitious materials for plastering walls, uniting bricks
and stone, manufacturing bricks and concrete blocks, making concrete
for building purposes, and other like objects. By my improved method
of compounding such materials I not only attain economy, but greatly
better results.
My method differs in the most essential particulars from the ordinary
methods of compounding lime mortars. In the ordinary method the
lime is first slaked by adding thereto a moderate quantity of water,
avoiding excess of water lest the lime be“ chilled," as it is termed, and
the slaking action being checked the mortar become poor and gritty.
The sand is next mingled with the lime so slaked, and more water is
added to bring the whole to a pasty condition, the chief aim being to
prepare a mixture in which the lime shall have become thoroughly
slaked, or, in chemical terms, "hydrated" before use. Again, for
plastering, the prepared stuff is by preference allowed to remain for a
fortnight or three weeks in a heap so that no particles may remain
unslaked, and by subsequently passing into the hydrated state in the
work occasion blisters.

page_text: The plan which I adopt in dealing with the lime is the very reverse of
all this. Instead of slaking the quick lime I so conduct the mani-
pulation of it that none of the action termed slaking shall take place
before use, but that the whole of the lime shall become, as it were,
"chilled" (to use the ordinary expression). The hydration then takes
place in the work after the mortar has been used, the "stuff" being
applied even in the case of plastering immediately or within one or two
hours of its being made up.
Having pointed out the essential difference between my mode of
treating lime for building purposes and the methods hitherto practised,
all of which (excepting the exploded method of M. Loriot, who proposed
using a proportion of quick lime with slaked lime for mortar, and
excepting also the case of concrete making, in which the lime can
slake in the work without injury to it), however they may vary in
details, have for their object the thorough slaking or hydration of the
lime before use, I shall proceed to explain in what manner I accomplish
what to builders will appear so improbable a thing as the safe employ-
ment of lime neither slaked by the air nor by water, for plastering and
other purposes.
In carrying out this object I make use of four agencies for the
prevention of the slaking process, and it may render my Invention
more intelligible and easy to be practised if I first state what they are.
They are these:-(1.) The reduction of the lime to a fine state of
division by mechanical means in lieu of the chemical method by
hydration accompanied by slaking. (2.) The employment of water so
used as to check the slaking process in lieu of promoting it. (3.) The
impregnation of this water with sulphuric acid by mingling with it
finely divided plaster of Paris or gypsum, or other soluble or partially
soluble sulphate or sulphates. (4.) The employment of mechanical
means in bringing about the free and unimpeded action upon the
particles of quick lime of the water and the sulphate of lime with which
it is impregnated.
The precise mode of proceeding in the preparation of mortar for
building or for coarse stuff for plastering is as follows:-I provide on
the site of the building works a grinding mill with an edge stone runner,
and a sifting apparatus attached thereto. With this machinery I reduce
the plaster and quick lime to a fine powder separately, grinding enough
for the day's consumption or for the whole job. Having determined how

page_text: much the mill can conveniently work in the wet condition at one
mixing, say, about one-third of a cubic yard, I take a pailfull of water
and stir into it one-eighth of a cubic foot of the plaster or sulphate, so
that the plaster may be well diffused through the water. Before it can
settle down and set I throw this into the pan of the grinding mill. I
then add to this mixture another pailfull or so of water, and then put in
by degrees two and a half cubic feet of the ground quick lime, adding
more water occasionally, until three and a half or four pails, say, thirteen
gallons in all, have been added, so as to keep the whole in the condition
As
of a thin "slip," the mill of course being at work the whole time.
the total quantity of water required will depend somewhat on the
condition of the sand, whether dry or otherwise, it is as well to keep the
quantity for the "slip" somewhat below the whole quantity necessary,
so that the consistency of the mortar obtained may be easily regulated.
If this operation be conducted as described (the quick lime having
become as I term it selenitic) will show no tendency to slake or even
warm, and the "slip" will remain quite cool while the ingredients of the
'slip" are agitated together by the action of the mill. The behaviour
of the lime under this treatment will indeed chemically be similar (so
far as I understand the chemistry of the action which takes place) to
that of cement prepared from quick lime which has been impregnated
with sulphurous acid gas and oxydising agencies. These ingredients
admit of being mixed up in the same way as Portland, Roman, and
other cements. This mixture is effected by lightly turning them over
with the sand so as to partially mix them, and then adding to these dry
or comparatively dry ingredients a sufficiency of water to convert them
into paste.
66
Special advantages are however obtained by my now invented fluid mode
of mixing the lime and the sulphate of lime, which advantages cannot be
secured either by the gaseous mode of procedure or by any dry method
of mixing the ingredients, coupled with the ordinary modes of preparing
cement mortar, for not only by my new process are notable proportions of
sulphate actually dissolved by the water and are through such solution
brought into the finest possible state of division and thus enabled to act
freely on every particle of lime throughout the compound, but the
freedom of movement obtained between the solid particles of sulphate
and those of the lime in this liquid condition enables a perfection of
admixture to be arrived at not attainable by other modes of procedure,

page_text: which require a nicety of attention (not always given by the manufacturer)
in order to secure with certainty the desired result. Every particle of
lime becomes infected as it were by actual contact with the leavening
influence of the sulphate, and is thereby deprived of its normal chemical
activity as respects its action with water. The new process is manifestly
applicable however as an improved mode of using cement prepared by
the processes alluded to, and I here think it as well to call attention also
to the fact that the plaster is not added with the view of deriving from it
the setting properties of the plaster as such, for plaster which has already
passed through the setting process (e.g. old plaster moulds) will answer the
purpose, and as already stated even unburned gypsum, and many other
soluble sulphates, may be used. There is, in fact, no analogy between the
use of plaster in this process and its use in what is termed "guaged stuff,"
when the plaster must be present in considerable quantity to provide a
notable effect. When the "slip" has assumed one uniform fluid
condition, a proportion of sand or other equivalent substance is added
by degrees, and the whole by means of a further addition of water if
required is brought to the consistency at which the workman prefers to
use it. The mortar thus prepared is fit for immediate employment on
the work. The proportion of extraneous material added to the "slip"
varies with the nature of the employment for which the mortar is
intended. In using grey chalk lime for conversion into "selenitic
mortar for ordinary building mortar or for coarse stuff, or selenitic plaster
for plastering, I use from ten to fifteen cubic feet of sand or other
equivalent substance to the above quantity of slip, but for damp or wet
situations I reduce this quantity of sand considerably. For coarse stuff
for plastering on lathwork I add to the slip about the usual proportion
of hair before adding the sand, and I find that the mill stones separate
and intermix the hair with the mortar far more effectually than can be
done by hand by the usual method, and that without the previous
beating hitherto practised. For floating, which can be done within a
few hours after the application of the first coat (so that in fact the two
processes form one coat, as do also the rendering and floating on brick)
the usual quantity of hair may be reduced one half. On brickwork
hair can be dispensed with altogether. For fine stuff for setting I may
replace part of the sand by slaked lime or finely ground chalk (or old
broken plaster moulds may be substituted for chalk), whereby I impart
greater unctuosity to the stuff, giving more facility to the plasterer in
applying it and improving the face which he can give to the work. I find
.
"

page_text: a good mixture for an ordinary setting coat to be one-eighth cubic foot
of sulphate of lime, two and a half cubic feet of ground lime, two and
a half cubic feet of ground chalk or slaked lime, and five cubic feet of
washed sand. For mortar for pointing one-eighth cubic foot of sulphate
of lime, two and a half cubic feet of ground lime, one half cubic foot of
chalk, and from ten to fifteen cubic feet of screened sand, will give good
results. For concrete I employ the sulphate of lime and lime in pro-
portion already stated. The "selenitic slip" thus prepared I mingle
either by hand or in a pug mill with the requisite quantity of shingle,
gravel, broken stone, burned clay, &c., according as it is intended for
blocks or for bricks, or for concrete, thrown into receptacles to form
monolithic walls.
In making bricks or blocks, I prepare the slip in the manner already
described and add thereunto the ballast, burnt clay, or other ingredients,
and having thoroughly incorporated them, I form the blocks either with
or without pressure in moulds, whence they may be removed and stacked
until sufficiently indurated for use or carriage.
In making bricks or blocks under heavy pressure it is sometimes of
importance that the ingredients should contain the minimum quantity
possible of water, and to effect this the plaster and lime with a small
quantity of water must be ground together in the consistency of a stiffish
paste, the grinding being continued for a longer period than is necessary
when a larger quantity of water can be employed. This paste with the
needful quantity of sand and ballast may then be thoroughly mixed and
dealt with as before described, and the compound be then subjected
to a heavy pressure in any of the machines now employed for similar
purposes.
In some cases I find it advisable to mix with the slip, or with the
selenitic mortar after its preparation, a proportion of Portland or other
cement, as, for instance, when the lime possesses little or no hydraulic
properties of its own. Or the selenitic mortar may be mixed with
plaster for the purpose of forming running mouldings, or with Parian or
Keene's cement; or the slip may be guaged with plaster for the purpose
of making moulds or to obtain a rapid set. The "selenitic" plaster may
also be used as a groundwork on which to finish with materials of more
expensive character, such as Parian cement; or again, it may be used
as a groundwork for setting with ordinary fine stuff or guaged stuff, or
for any method by which a fine face is given in plastering. In the

page_text: preparation of the selenitic mortar I sometimes also employ in lieu of
sand (either partially or wholly) natural or artificial puzzolanas for the
purpose of imparting hydraulic properties to the compound,
In the foregoing description I have stated the plan which I have
found the best in practice, but I do not confine myself to this precise
method or order for carrying out my process. In lieu (for instance) of
completing the process of making the mortar in the mortar mill I may
prepare the "slip" in a small mill insufficient to take the sand as well
as the slip, and when the slip is prepared I mix it with the sand either
by hand or in a pug mill; or again, for common mortar for rough brick-
work, in lieu of grinding the materials previous to the actual operation
of making the mortar I commence this operation with the material in
lump. In this case, when the whole of the lime has been ground in
water to a fine powder without allowing it to slake I sometimes (as for
instance when a neat struck joint is essential) get rid of the coarser
particles which would cause blisters by straining the slip through a
fine sieve. I may sometimes also grind the sulphate of lime and lime
together and introduce these ingredients (thus partially incorporated)
into the mortar mill, and then proceed as in the first instance to further
agitate them together in water to complete the process and insure that
the whole of the lime may be brought under the influence of the sulphate
and be sufficiently impregnated to prevent its slaking. Or again, when
chalk is used in combination with lime to impart more unctuosity than
can be given by sand only I frequently find that it is moro economical
(owing to the moisture in the chalk) to grind it in the mill in its moist
condition and then to proceed with making the slip as before. Or again,
the materials may be brought to the ground in the pulverised condition
and the slip be prepared in a wash tub suitably arranged with arms which
will agitate the ingredients together. The slip and the sand can then be
passed through a pug mill, so as to effect their thorough incorporation,
or they may be mixed by hand. I find, however, no process so effica-
cious and simple for bringing about the complete amalgamation of the
requisite ingredients and their proper action as the process first described,
the use of which I recommend wherever possible.
My description hitherto has been based on the assumption that grey
chalk lime or lime having similar properties is to be operated upon. It
remains for me to give the operator instructions by which he may be
guided in dealing with other limes commonly met with.

page_text: In the case of the pure limes, such as those prepared from some of the
mountain limestones or white chalk lime, I recommend the increase of
the quantity of sulphate of limo to one part for every fifteen parts of
quick lime; for some lias limes I may reduce the quantity of sulphate
to one part for every twenty-five or thirty parts of quick lime, and in
some instances of very argillaceous limes it may be reduced to one part
for every fifty parts of quick lime. The quantity of clay indeed which a
limestone contains may as a general rule be taken as a measure of the
proportion of sulphate to be used, those which are freest from clay
requiring most sulphate. Other modifying elements are, first, the
existence of a certain amount of sulphate found in some limes either
resulting from calcination or being naturally present; and, secondly, the
condition of freshness or otherwise in which the lime is employed. The
quantity of sulphate of lime may be somewhat reduced with advantage
when the lime is partially slaked before it is operated on.
Other soluble sulphates may sometimes be used instead of sulphate of
lime or gypsum, such as sulphate of iron, sulphate of zinc, or sulphate
of magnesia, or sulphuric acid may be employed in lieu of sulphates;
but I find no substance so generally useful for the purpose, whether
considered with reference to price or action, as sulphate of lime. Certain
sulphates succeed ill with some limes, and others I have found not to
answer at all. Sulphate of copper gave bad results in every case in
which I tried it, and sulphate of iron gives unsatisfactory results with
grey chalk lime. Some of the alkaline sulphates also do not succeed in
all cases.
If the lime is improved by the presence of oxide of iron
I use sulphate of iron, as, for instance, with the hydraulic limes of North
Wales.
Having now described my Invention, and the means by which I carry
the same into effect, I wish it to be understood that I make no claim for
such mixtures of lime with plaster of Paris as are commonly used by
plasterers, where the quick setting property of the plaster itself is the
only object of the mixture, but I claim,-
First. Producing a "slip" or a liquid mixture consisting of lime and
a small per-centage of sulphate of lime, or other equivalent sulphate, in
order that the lime may become thoroughly impregnated with the sul-
phate (or becomes, as I have termed it," selenitic,”) and thus lose its
normal avidity for chemical combination with water.

page_text: Second. I claim producing a highly plastic and cementitious selenitic
preparation or compound by agitating, triturating, or rubbing together,
with water in the manner described, quick lime with a small per-
centage of sulphate of lime or other equivalent sulphate (accompanied
or not by extraneous materials, such as sand, chalk, burnt clay, or other
substances) for the more perfect neutralization of the slaking properties
of the lime, as herein set forth.
Third. Combining the selenitic " slip" or the selenitic mortar,
prepared as above set forth, with any of the existing cements, for the
purpose of imparting to such selenitic "slip" or mortar hydraulic or
quick setting properties.
Fourth. The employment of selenitic concrete for the manufacture of
bricks or blocks moulded either with or without pressure.
In witness whereof, I, the said Henry Young Darracott Scott, have
hereunto set my hand and seal, the Eighteenth day of October, in
the year of our Lord One thousand eight hundred and seventy.