Hi humam,
The "best clay" to use will vary depending on the job at hand and it's
impossible to pinpoint one clay and say it is the best for brick
making because the uses of brick are about as vast as the properties
of clay. Rather than seek the the ideal clay which meet their needs,
brick makers buy clay which is readily available to them and adjust
its properties to fit their needs. With that said, we can go a step
further and say that surface "alluvial clay", the mainstay of brick
making in historical times, still makes fine bricks. However, alluvial
clay isn't always readily available and older, deeper deposits,
although requiring more preparation to make it suitable for brick
making, is used. This often requires blending different clays and
adding minerals on a trial and error basis until the desired results
is achieved. I've copied and pasted some relevant sections below but
please click on the links for full details.
>>> Alluvial Clay
"Clay - Different clays perform different tasks. Bentonite and
taylorite are used in petroleum mud drilling; fireclay with its high
percentage of alumina and silica is used as refractory clay. Kaolin
for the manufacture of china and ceramics, white clay for brickmaking.
Brick, pipe and tile clays can be used directly for the manufacture of
tiles and pipes, but are usually mixed with other materials. Alluvial
clay and shale makes some of the best bricks."
http://www.cmewa.com.au/eai_default.aspx?eai_general.aspx?itid=119
"...sticky alluvial clay, your mudbricks will be excellent"
http://www.hotkey.net.au/~bobrich/mudsmith/builsamp.html
Alluvial - definition, images, and more
http://www.websters-online-dictionary.org/definition/english/al/alluvial.html
>>> Brick clay overview
VITA : Understanding the Small-Scale Clay Products Enterprise
"Most clays are predominantly kaolin mixed with other clay minerals
and impurities such as iron, manganese, mica, silica, and rock
fragments. The different mixes and proportions affect the working
properties of clays, causing them to vary in their behavior. Some
clays are suitable for one kind of product only, others have broader
uses, and still others are totally unusable. The only sure way to
determine the workability of a particular clay is to make the desired
product on a trial basis and analyze the results. This kind of
practical test is much more satisfactory for most operations than the
more complicated laboratory testing, which should be undertaken only
after a clay or blend is deemed usable."
http://sleekfreak.ath.cx:81/3wdev/VITAHTML/SUBLEV/EN1/CLAYPROD.HTM
"It is impossible to give a typical composition for such clays, as the
percentages of the different constituents vary through such wide
ranges. The clay substance may vary from 15 to 80%, the free silica or
sand from 5 to 80%, the oxide of iron from I to 10%, the carbonates of
lime and magnesia together, from I to 5 %, and the alkalis from I to
4%. Organic matter is always present, and other impurities which
frequently occur are the suiphates of lime and magnesia, the chlorides
and nitrates of soda and potash, and iron-pyrites."
http://www.cmewa.com/eai_default.aspx?eai_general.aspx?itid=95s
PROPERTIES
"All properties of brick are affected by composition of the raw
materials and the manufacturing processes. It is for this reason that
most manufacturers blend clays to reduce the possibility of impurities
from one clay source affecting the overall quality of the finished
product. Similarly, the standardization of the manufacturing processes
permits the manufacturer to limit variations due to processing and to
produce a more uniform product.
Product Use
The properties that most concern the users of brick are 1) durability,
2) color, 3) texture, 4) size variation, 5) compressive strength and
6) absorption."
http://www.bia.org/BIA/technotes/t9.htm
"Common clay is clay or a claylike material that is easily molded or
shaped and changed into a glasslike material at temperatures of 1,100
°C (about 2000 °F) or less. The minerals found in common clay are
biotite, illite, muscovite, and sericite; other minerals, such as
kaolinite, smectite-group clays (montmorillonite, saponite,
nontronite, and so forth), mixed-layer clays, and chlorite, also are
present in many deposits. Common clay is usually higher in alkalies,
alkaline earths, and iron-rich minerals and lower in aluminum than
ball clay, fire clay, and kaolin. Common clay is mined in hundreds of
places across the United States. When common clay is processed, it is
used mainly in the manufacture of building bricks."
http://resourcescommittee.house.gov/subcommittees/emr/usgsweb/materials/clays.html
Taken from the websites posted here, I've put together a little
summary of what to look for in brick clay.
1. Alluvial clay
2. Clay and silt 25 - 50%
3. Sand 50 - 75%
4. Low shrinkage percentage
5. Low swelling percentage
6. Consistent firing color
7. Relatively low firing temperature
8. Good strength after firing
9. Small percentage of carbonate of lime
10. Hydrated aluminium silicates (higher percentage = stronger brick)
11. Undecomposed grains of felspar
12. Iron oxide, 5 - 8% (red brick colour)
("A clay containing from 5 to 8 % of oxide of iron will, under
ordinary conditions of firing, produce a red brick; but if the clay
contains 3 to 4% of alkalis, or the brick is fired too hard, the color
will be darker and more purple.
13. Alumina
(an excess of this compound tending to make the color lighter and brighter)
14. Weathering or aging improves clay
"Clays which are strong or plastic are known as fat clays, and they
always contain a high percentage of true clay substance, and,
consequently, a low percentage of sand. Such clays take up a
considerable amount of water in tempering; they dry slowly, shrink
greatly, and so become liable to lose their shape and develop cracks
in drying and firing. Fat clays are greatly improved by the addition
of coarse sharp sand, which reduces the time of drying and the
shrinkage..."
http://www.cmewa.com/eai_default.aspx?eai_general.aspx?itid=95
Brick Clay: suitable clay for the manufacturing of bricks or coarse
pottery. Often an impure clay containing iron, calcium, magnesium and
other ingredients is referred to as brick clay. The chief chemical
composition of brick clays is silica, alumina, iron oxide, magnesia,
lime and alkalis. Either more or less than the required amount of any
of these constituents may cause serious damage to the products. The
presence of some harmful constituents like iron concretions, stone
particles, soluble salts and limestone has a detrimental effect on
brick."
http://banglapedia.search.com.bd/HT/B_0626.htm
"The manufacturer minimizes variations in chemical composition and
physical properties by mixing clays from different locations in the
pit and from different sources. However, because clay products have a
relatively low selling price, it is not economically feasible to
refine clays to produce uniform raw materials. Since variations in
properties of raw materials must be compensated for by varying
manufacturing processes, properties of finished products from
different manufacturers will also vary somewhat."
PROPERTIES
"All properties of brick are affected by composition of the raw
materials and the manufacturing processes. It is for this reason that
most manufacturers blend clays to reduce the possibility of impurities
from one clay source affecting the overall quality of the finished
product. Similarly, the standardization of the manufacturing processes
permits the manufacturer to limit variations due to processing and to
produce a more uniform product.
Product Use
The properties that most concern the users of brick are 1) durability,
2) color, 3) texture, 4) size variation, 5) compressive strength and
6) absorption."
http://www.bia.org/BIA/technotes/t9.htm
"Clay is required to form the bricks. It is normally obtained by
excavating it with pickaxes or similar from a clay deposit. To be
suitable for making bricks, it should contain 25-50% clay and silt and
50-75% coarser material such as sand. These proportions can be
determined using a simple sedimentation test. The coarse material
prevents the clay cracking as it dries and should be added if the
percentage on excavation is too low. A test to assess suitability is
to roll a 10 mm diameter cylinder of wet clay and allow it to hang
from one end. If a portion 50-150 mm long breaks off, the clay is
suitable for bricks. Clay should be mixed with water and kneaded to
give it a uniform plastic consistency. Linear shrinkage of the
prepared clay should not be greater than 7%."
http://www.ifgworld.org/subsites/documents/document_view.asp?title=Clay+Brick+Surface&siteid=1&id=92
>>> Details
Brick
"The alluvial and drift clays (which were alone used for brickmaking
until modern times) are found near the surface, are readily worked and
require little preparation, whereas the older sedimentary deposits are
often difficult to work and necessitate the use of heavy machinery.
These older shales, or rocky clays, may be btought into plastic
condition by long weathering (i.e. by exposure to rain, frost and sun)
or by crushing and grinding in water, and they then resemble ordinary
alluvial clays in every respect."
Clay - Different clays perform different tasks. Bentonite and
taylorite are used in petroleum mud drilling; fireclay with its high
percentage of alumina and silica is used as refractory clay. Kaolin
for the manufacture of china and ceramics, white clay for brickmaking.
Brick, pipe and tile clays can be used directly for the manufacture of
tiles and pipes, but are usually mixed with other materials. Alluvial
clay and shale makes some of the best bricks."
"The clays or earths from which burnt bricks are made may be divided
into two principal types, according to chemical composition: (I) Clays
or shales containing only a small percentage of carbonate of lime and
consisting chiefly of hydrated aluminium silicates (the true clay
substance ) with more or less sand, undecomposed grains of felspar,
and oxide or carbonate of iron; these clays usually burn to a buff,
salmon or red color; (2)"
"Brick clays of class (I) are very widely distributed, and have a more
extensive geological range than the marls, which are found in
connection with chalk or limestone formations only. These ordinary
brick clays vary considerably in composition, and many clays, as they
are found in nature, are unsuitable for brickmaking without the
addition of some other kind of clay or sand. The strongest brick
clays, i.e. those possessing the greatest plasticity and tensile
strength, are usually those which contain the highest percentage of
the hydrated aluminium silicates, although the exact relation of
plasticity to chemical composition has not yet been determined. This
statement cannot be applied indiscriminately to all clays, but may be
taken as fairly applicable to clays of one general type (see CLAY).
All clays contain more or less free silica in the form of sand, and
usually a small percentage of undecomposed feispar. The most important
ingredient, after the clay-substance and the sand, is oxide of iron;
for the color, and, to a less extent, the hardness and durability of
the burnt bricks depend on its presence. The amount of oxide of iron
in these clays varies from about 2 to 10%, and the color of the bricks
varies accordingly from light buff to chocolate; although the color
developed by a given percentage of oxide of iron is influenced by the
other substances present and also by the method of firing. A clay
containing from 5 to 8 % of oxide of iron will, under ordinary
conditions of firing, produce a red brick; but if the clay contains 3
to 4% of alkalis, or the brick is fired too hard, the color will be
darker and more purple. The actions of the alkalis and of increased
temperature are probably closely related, for in either case the clay
is brought nearer to its fusion point, and ferruginous clays generally
become darker in color as they approach to fusion. Alumina acts in the
opposite direction, an excess of this compound tending to make the
color lighter and brighter. It is impossible to give a typical
composition for such clays, as the percentages of the different
constituents vary through such wide ranges. The clay substance may
vary from 15 to 80%, the free silica or sand from 5 to 80%, the oxide
of iron from I to 10%, the carbonates of lime and magnesia together,
from I to 5 %, and the alkalis from I to 4%. Organic matter is always
present, and other impurities which frequently occur are the suiphates
of lime and magnesia, the chlorides and nitrates of soda and potash,
and iron-pyrites. The presence of organic matter gives the wet clay a
greater plasticity, probably because it forms a kind of mucilage which
adds a certain viscosity and adhesiveness to the natural plasticity of
the clay. In some of the coalmeasure shales the amount of organic
matter is very considerable, and may render the clay useless for
brickmaking. The other impurities, all of which, except the pyrites,
are soluble in water, are undesirable, as they give rise to scum,
which produces patchy color and pitted faces on the bricks. The
commonest soluble impurity is calcium sulphate, which produces a
whitish scum on the face of the brick in drying, and as the scum
becomes permanentlyfixed in burning, such bricks are of little use
except for common work. This question of scumming is very important to
the maker of high-class facing and moulded bricks, and where a clay
containing calcium sulphate must be used, a certain percentage of
barium carbonate is nowadays added to the wet clay. By this means the
calcium sulphate is converted into calcium carbonate which is
insoluble in water, so that it remains distributed throughout the mass
of the brick instead of being deposited on the surface. The presence
of magnesium salts is also very objectionable, as these generally
remain in the burnt brick as magnesium sulphate, which gives rise to
an efflorescence of fine white crystals after the bricks are built
into position. Clays which are strong or plastic are known as fat
clays, and they always contain a high percentage of true clay
substance, and, consequently, a low percentage of sand. Such clays
take up a considerable amount of water in tempering; they dry slowly,
shrink greatly, and so become liable to lose their shape and develop
cracks in drying and firing. Fat clays are greatly improved by the
addition of coarse sharp sand, which reduces the time of drying and
the shrinkage, and niakef the brick more rfgfd during the firing
Coarse sand, unlike clay-substance, is practically unaffected during
the drying and firing, and is a desirable if not a necessary
ingredient of all brick clays. The best brick-clays feel gritty
between the fingers; they should, of course, be free from pebbles,
sufficiently plastic to be moulded into shape and strong enough when
dry to be safely handled. All clays are greatly improved by being
turned over and exposed to the weather, or by standing for some months
in a wet condition. This weathering and ageing of clay is particularly
important where bricks are made from tempered clay , i.e. clay in the
wet or plastic state; where bricks are made from shale, in the
semi-plastic condition, weathering is still of importance."
http://www.cmewa.com/eai_default.aspx?eai_general.aspx?itid=95
Classification by Use
"Clays are rarely present as pure minerals, but rather are mixtures of
the different clay types, one group or type normally being dominant.
The physical properties of clays, which determine their commercial
value, depend on whether or not the various types are admixed, what
types of clays are present and their percentages, the percentage and
composition of non-clay materials present, and other factors.
Important physical properties are firing temperature, shrinkage or
swelling percentage on firing, plasticity index, bloating
characteristics, firing color, percentage of fines (slack) produced
upon crushing, and fired strength.
Utilization of clay as a resource material requires that the clay have
a restricted range of properties for each industry. Therefore, a brick
manufacturer wants a large-volume source of moderately uniform clay
that has a low shrinkage/swelling percentage, consistent firing color,
relatively low firing temperature, and good strength after firing. A
lightweight aggregate manufacturer desires a clay which upon firing,
bloats or swells to become a cellular frothy mass. A paper
manufacturer has a specific whiteness test that any given kaolinite
must pass before it can be used as a surface coating for high-quality
paper. Because individual clay deposits can be unique due to their
specific modes of formation and physical characteristics of any given
blend of clays, industry usually classifies clay by the properties
which determine its usage. This type of classification includes ball
clay, bentonite, bloating clay, brick clay, common clay, fuller's
earth, pottery clay, fire or refractory clay, high purity kaolin, and
several others."
Common Clay
Clay suitable for the manufacture of heavy clay products, such as
building and paving bricks, drain tile, and sewer tile, are present in
several areas of the state and have been utilized for many years. Many
deposits of kaolin, ball clay, and fire clay are suitable for heavy
clay products. To manufacture heavy clay products, the natural
material must possess certain working and drying properties, the most
important include plasticity when wet, little shrinkage when drying
and being fired, and good strength as both a green (unfired) and fired
product. The fired color of the clay is important to both the consumer
and manufacturer. A building-brick clay that fires white may be
developed commercially because, by the addition of various minerals,
the color may be modified to meet whatever is popular among consumers.
Clay from another deposit, otherwise comparable in size and clay
quality, that fires to a red to orange color may not be commercially
suitable for the brick industry, but may be considered usable by the
manufacturer of unglazed clay flower pots."
http://www.state.ar.us/agc/clay.htm
The Northwest Masonry Guide
http://www.masonryinstitute.com/guide/part2/prod_a1-p3-4.html
"Clays are categorized into six categories in industry. These
categories are ball clay, bentonite, common clay, fire clay, fuller?s
earth, and kaolin."
http://www.mii.org/Minerals/photoclay.html
Colour oxides:
"Oxides used for coloring clay bodies have to be fairly cheap. That
excludes most oxides, leaving us with iron oxide, manganese dioxide
and ilmenite. Coloring of engobes for decoration will not be dealt
with here.
Iron oxide exists in two main forms. Red iron oxide (Fe2O3) is the
same as rust, and has a dark red color. Black iron oxide (Fe3O4) has a
coarser particle size than red iron oxide. Black iron oxide can be
produced by roasting iron metal to 400° to 700° C in the flue channel
or chimney of the kiln. The black crust of oxide is knocked off the
metal and ball milled. Ochre is a yellowish material often used for
painting houses. It contains iron oxide in a mixture of clay, sand and
sometimes limestone. When the ochre contains manganese, it is called
umber. Both materials can be used as coloring agents in clay and
glazes. Ilmenite (FeO.TiO2) is a black crystal, often occurring as
black stripes in beach sand together with zircon sand.
The coloring effect of iron oxide depends very much on the atmosphere
and temperature in the kiln:
- Iron oxide in an oxidizing firing below 1020° C will produce a brick red colour.
- Oxidizing firing to 1100° C turns the red colour darker and brownish.
- In a reducing firing the colour will be grey or black.
Above 1000° C iron oxide acts as a strong flux in reducing atmosphere,
but when the condition is oxidizing, its fluxing action only starts
above 1200° C. Whiting present in the clay has a bleaching effect on
the red colour of iron oxide. In red firing surface clays iron oxide
content is often 10% .
Manganese dioxide (MnO2)is dark brown to black. As a colorant in clay
it produces yellow, brown, purple or black colors. It acts as a strong
flux. Only half a percent of manganese will give red clay a brown
colour, and with increasing amounts the clay will become black. Black
colors are obtained by adding a mixture of iron oxide and manganese
dioxide. "
Examples of water absorption: Red bricks: 20 - 40 %
http://www.sadl.uleth.ca/nz/collect/hdl/import/gtz/g41cle/g41cle.htm
"It is impossible to give a typical composition for such clays, as the
percentages of the different constituents vary through such wide
ranges. The clay substance may vary from 15 to 80%, the free silica or
sand from 5 to 80%, the oxide of iron from I to 10%, the carbonates of
lime and magnesia together, from I to 5 %, and the alkalis from I to
4%. Organic matter is always present, and other impurities which
frequently occur are the suiphates of lime and magnesia, the chlorides
and nitrates of soda and potash, and iron-pyrites. The presence of
organic matter gives the wet clay a greater plasticity, probably
because it forms a kind of mucilage which adds a certain viscosity and
adhesiveness to the natural plasticity of the clay. In some of the
coalmeasure shales the amount of organic matter is very considerable,
and may render the clay useless for brickmaking. The other impurities,
all of which, except the pyrites, are soluble in water, are
undesirable, as they give rise to scum, which produces patchy color
and pitted faces on the bricks. The commonest soluble impurity is
calcium sulphate, which produces a whitish scum on the face of the
brick in drying, and as the scum becomes permanentlyfixed in burning,
such bricks are of little use except for common work.
http://54.1911encyclopedia.org/B/BR/BRICK.htm
DESCRIPTIVE MINERAL TABLE
http://www.utm.edu/departments/ggp/mineraltable.htm
"First, the clay or shale used to make the brick must possess certain
qualities. Top quality bricks are made using clay or shale which has
excellent plasticity and fusibility."
http://www.askthebuilder.com/069_Brick_and_Colored_Mortar.shtml
Raw Materials
"Clay is one of the most abundant natural mineral materials on earth.
Clay for the production of brick must, however, possess some specific
properties and characteristics. To satisfy modern production
requirements, clays must have plasticity, which permits them to be
shaped or molded when mixed with water; and they must have sufficient
wet and air-dried tensile strength to maintain their shape after
forming. Also, when subjected to rising temperatures, the clay
particles must fuse together (see Firing and Cooling).
Types of Clay
Clays occur in three principal forms, all of which have similar
chemical compositions but different physical characteristics. They
are:
Surface Clays. Surface clays may be the upthrusts of older deposits or
of more recent, sedimentary formation. As the name implies, they are
found near the surface of the earth.
Shales. Shales are clays that have been subjected to high pressures
until they have hardened almost to the form of slate.
Fire Clays. Fire clays are usually mined at deeper levels than other
clays and have refractory qualities.
Clays are complex materials; surface clays and fire clays differ from
shales more in physical structure than in chemical composition.
Chemically, all three are compounds of silica and alumina with varying
amounts of metallic oxides and other impurities. Although technically
metallic oxides are impurities, they act as fluxes, promoting fusion
at lower temperatures. Metallic oxides (particularly those of iron,
magnesium and calcium) influence the color of the finished fired
product.
The manufacturer minimizes variations in chemical composition and
physical properties by mixing clays from different locations in the
pit and from different sources. However, because clay products have a
relatively low selling price, it is not economically feasible to
refine clays to produce uniform raw materials. Since variations in
properties of raw materials must be compensated for by varying
manufacturing processes, properties of finished products from
different manufacturers will also vary somewhat."
http://www.bia.org/BIA/technotes/t9.htm
Waterstruck Brick
"In addition to an uncommon and rugged handsomeness, the physical
properties of waterstruck brick are almost never matched by other
brick types and certainly never surpassed."
http://www.vermontbrick.com/index_files/Page894.htm
Additional Links of Interest:
Dictionary of Mining, Mineral, and Related Terms
http://www.maden.hacettepe.edu.tr/dmmrt/index.html
What is adobe?
"Adobe bricks are largely local mud, usually mixed with some sort of
vegetable additive (often straw but sometimes animal manure). Not all
soils are appropriate for making an adobe brick. This sometimes meant
that the missions had to import their building materials from other
locations if the local soil was not found to be practical for making
bricks. Soil with too much clay will typically cause bricks to shrink
and crack badly as they dry. The soil you want for adobe is a loamy
sand material as described in this table...
Soil Texture % Sand % Clay % Silt
Loamy sand 70-85 0-15 0-30
Sandy loam 50-70 15-20 0-30
Sandy clay loam 50-70 20-30 0-30
Note, particularly, that in all cases the percentage of clay is always
less than a third of the material and the percentage of sand is always
better than half sand. That's the soil type best for making adobe
bricks."
http://missiontour.org/related/adobe.htm
"This Technical Notes describes the various kinds of brick and their
classification. Specific requirements including physical properties,
efflorescence, dimensional tolerances, distortion, chippage, and
coring are described. Additional requirements for each kind of brick
are also covered."
http://www.bia.org/BIA/technotes/t9a.htm
Environmental Health Criteria 231
BENTONITE, KAOLIN, AND SELECTED CLAY MINERALS
http://www.inchem.org/documents/ehc/ehc/ehc231.htm
> Books
If any of these titles interest you, you can search for them on
Amazon.com, or for used copies, try BookFinder.com.
W F Cole
STUDIES ON CLAY MINERALS, AUSTRALIAN CLAYS, PROPERTIES OF FIRED CLAYS
AND SET CEMENTS
Newton, Joseph
Clay- Its Composition, Properties and Uses: Idaho Bureau of Mines and Geology
Bartel, Marvin P.
Clay: a Programmed Study of the Types and Properties of Clay-and How
It is Formulated for Pottery
Blackmon, Paul D.
Neutralization Curves and the Formulation of Monovalent Cation
Exchange Properties of Clay Minerals
Smothers, William J., & Paul G. Herold
A Study of the Flow Properties of Concentrated Clay-Water Mixtures
Alanah Fitch
Electrochemical Properties of Clays
[?]
Clay: A programmed study of the types and properties of clay
Pusch Roland
Clay particles - their size, shape and arrangement in relation to some
important physical properties of clay
Rossman F. Giese
Colloid and Surface Properties in Clays and Related Materials
ILO, World Employment Programme
Small-Scale Brickmaking
Alfred B Searle
Modern Brickmaking
Hammond, Martin
Bricks and Brickmaking
Dunham A
Developments in industrial mineralogy: I. The mineralogy of brickmaking
Dobson, Edward
[1850] Rudimentary Treatise on the Manufacture of Bricks and Tiles.
Containing an Outline of the Principles of Brickmaking, and detailed
accounts of the various processes employed in the making of Bricks and
Tiles in different part of England. In Two parts
Anne Beamish
Village-Level Brickmaking
Kelvin Mason
Brick by Brick: Participatory Technology Development in Brickmaking
Karl Gurcke
Bricks and Brickmaking: A Handbook for Historical Archaeology
Marcel F. De Boodt; Michael H.B. Hayes; Adrien Herbillon
Soil Colloids and Their Associations in Aggregates
Amrhein, J.E.
Reinforced Masonry Engineering Handbook Brick and Other Structural Clay Units
Beyer, Albin H., & William J. Krefeld
Comparative Tests of Clay, Sand-Lime and Concrete Brick Masonry
George H. Cook, u.a
[1878] Report on the Clay Deposits of Woodbridge, South Amboy and
other Places in New Jersey, together with their Uses for Fire Brick,
Pottery, & C.
R.C.De Vekey
Clay Bricks and Clay Brick Masonry (Digest)
MORRISON, R. B.
Brickmakers' Manual
I hope my research proves to be just what you need. If you have any
questions, please post a clarification request and wait for me to
respond before closing/rating my answer.
Thank you,
hummer
Some of the Google search terms used (but there were many): red brick
raw clay alumina iron oxide top quality clay making bricks alluvial
composition properties minerals common "brick clay" characteristics |
,
0 Comments
)