ABRASION, SPECIFIC GRAVITY.
_Abrasion._--In this country it is not customary to test bricks and
stone by means of the abrasion process, though many English materials
have been dealt with in this manner on the continent.
Abrasion tests are of special value in regard to paving bricks, and
this mode of experiment is largely carried out in the United States.
As Mr. H. Ries remarks,[21] the abrasion test approximates closely the
conditions under which the paving brick is used, and is, therefore, an
important one. The usual method of conducting this test is to put the
bricks in an ordinary “foundry rattler,” filling it about one-third
full. It is then rotated at the rate of about 30 revolutions per
minute, and about 1,000 turns are sufficient. The bricks are weighed
before and after to determine loss by abrasion.
A more recent modification is to line the “rattler” with the bricks to
be tested and then put in loose scrap iron. This is claimed to give
more accurate results, and avoids loss by chipping due to the bricks
knocking against each other, as in the previous method, although
that has been somewhat obviated by Professor Orton, jun., by the
introduction of a few billets of wood into the rattler.
The abrasion test may also be made by putting the weighed bricks on
a grinding table covered with sand and water, and noting the weight
before and after grinding. This last method seems to us to be decidedly
the best, provided the bricks be weighted, that the weight is constant,
that the feed of sand and water is uniform, and that the bricks to be
tested are placed equidistant from the centre of the turning table. If
this last point be not attended to, it will be obvious that in course
of the revolutions the sand will tend to accumulate towards the centre
of the table, and the bricks placed in that vicinity would receive
more than their fair share of abrasion, as compared with those bricks
situated near the edge of the table. Conversely, those bricks near
the periphery would be subjected to greater grinding action, from the
circumstance that the table would move faster underneath them than
under those bricks nearer the centre of the table.
The bricks should certainly be weighted in such abrasion tests, and
it seems desirable that the weights should be so adjusted that the
weight of the brick is also taken into account. It is obvious that the
abrading action of, say, street traffic, will be the same on a brick,
no matter what the latter weighs, depending on the area of surface
exposed to traffic. And if we experiment with one brick, weighing say 7
lbs., and another weighing 14 lbs., the greater weight of the latter,
will (_cæteris paribus_), by the abrasion tests as usually adopted,
give a much higher result than would the lighter brick. On the other
hand, if the 7 lbs. brick be weighted another 7 lbs., then the results
would be strictly comparable, provided always that the area exposed to
abrasion in each case be the same, and that the other conditions we
have laid down are strictly observed.
Knowing as we do that the rough and ready method of “rattling” cannot
possibly give truly comparative results, we do not intend to enlarge
much on the results of the American tests; but the following are
suggestive as shewing the connexion between the tests for absorption,
rattling, and strength combined.
Some valuable and interesting tests were recently made by the Ohio
Geological Survey, to determine the relative merits of fire-clays and
shales for the manufacture of paving bricks, as well as the influence,
if any, of the method of manufacture adopted. Twenty-two varieties of
shale bricks, or bricks the largest constituent of which is shale, were
grouped together: fifteen varieties of fire-clay brick; four varieties
composed of shale and fire-clay mixed in equal proportion; and three
varieties made from Ohio River sedimentary clays. The averages of these
four classes of results were as follow:--
--------------------------------------------------
TESTS OF FIRE-CLAY AND SHALES.--PAVING BRICKS.
----------+-----------+---------+-----------------
|Absorption.|Rattling.| Crushing.
+-----------+---------+--------+--------
| | |Square | Cubic
| | |Inches. | Inches.
| | +--------+--------
Shales | 1.17 | 17.61 | 7,307 | 1,764
Fire-clay | 1.62 | 17.32 | 6,876 | 1,678
Mixture | 1.44 | 18.72 | 5,788 | 1,400
River Clay| 1.36 | 19.02 | 4,605 | 1,176
----------+-----------+---------+--------+--------
From a series of tests recently made by Mr. Fickes,[22] the following
factors were educed:--
1. A brick which stands the “rattling” test well, has ample crushing
strength and rarely chips under less than 5,000 lbs. per square inch,
or crushes under less than 10,000 lbs. The crushing strength tends to
vary with the resistance to abrasion, however, but more slowly and
irregularly.
2. The transverse strength also tends to vary with the resistance to
abrasion, but more slowly and irregularly.
3. The toughest bricks usually absorb the least water.
_Specific Gravity._--The practical value of knowing the specific
gravity of a brick has, perhaps, been a little over-rated by writers on
the subject. At the same time we do not deny that there is some use in
ascertaining this property. Foremost, we have to mention its value in
conjunction with absorption in arriving at a rough and ready means of
gauging the strength of a brick, without having actual recourse to the
crushing machine. It appears to us, however, that the specific gravity
of bricks is rarely quoted in a proper manner, and until there is one
uniform method, the results will always be at a discount. We allude to
the fact that some experimenters take the specific gravity of a porous
brick, without stating whether the amount of water absorbed, during the
process, was taken into account in arriving at the specific gravity
or not. Theoretically, of course, the substance to be dealt with is
non-porous, and experimenters, worthy the name, either render the
brick waterproof, or, ascertaining the amount of water the brick has
absorbed, take that into consideration in calculating results.
The writer is in the habit of quoting the specific gravity in two ways,
viz.: (_a_) the true specific gravity, and (_b_) the specific gravity
of the particles. In an elementary treatise like the present, however,
it is not desirable to enlarge on this subject.
THE END.
FOOTNOTES
[1] This, and all other technical terms used, will be explained in an
alphabetical glossary at the end of the book.
[2] “Canal and River Engineering,” p. 315.
[3] See, Geikie’s “Text Book of Geology,” 1882, p. 72.
[4] Information on this subject will be found in Mr. J. H. Collins’
work, “The Hensbarrow Granite District.” Truro, 1878.
[5] “Text Book of Geology,” 1882, p. 85.
[6] “Aids in Practical Geology,” 1893, page 36.
[7] See E. S. Dana, “Minerals and How to Study Them,” 1895, p. 154.
[8] Consult “Applications of Geology,” etc., by Prof. Ansted, 1865, p.
116, _et seq._
[9] “Industrial Resources of the Tyne, Wear and Tees,” 1864, p. 204.
[10] R. H. Scott, “Elementary Meteorology,” 1883, p. 137.
[11] Report of British Association for 1846, Part II., p. 17.
[12] Geological Magazine, N.S., Dec. III., Vol. V, 1888, pp. 26 _et
seq._
[13] Such as “The Study of Rocks,” by F. Rutley: “Aids in Practical
Geology,” by Prof. Grenville Cole; “Tables for the Determination of
the Rock-forming Minerals,” by Prof. Lœwinson Lessing; “Petrology for
Students,” by A. Harker; and especially “Microscopic Physiography of
the Rockmaking Minerals,” by Rosenbusch (transl. Iddings).
[14] Consult the works on petrology previously mentioned.
[15] The mode of preparation of thin rock sections for examination by
the microscope is described in much detail in the works of Mr. Rutley
and Professor Cole previously alluded to; also in “Outlines of Field
Geology,” by Sir Archibald Geikie, 1882, p. 202 _et seq._
[16] 16th Ann. Rep. U. S. Geol. Surv. (1894–95), pt. IV., p. 532.
[17] 16th Ann. Rep. U. S. Geol. Surv. (1894–95), pt. IV., p. 539.
[18] “Testing of Materials of Construction,” 1888, p. 438.
[19] _British Clayworker_, April, 1896, Supplement, p. iv.
[20] _Op. cit._ p. iv.
[21] 16th Ann. Rep. U.S. Geol. Surv. Pt. IV., 1895, p. 532.
[22] _Engineering News_ (U.S.), Dec. 13th, 1894.
INDEX, &c.
Abrasion tests, 146
Absorption of bricks, 132
Acids defined, 76
Actinolite, 69
Air, chemical composition of, 105
Albite felspar, chemical composition, 34
Almandite, 68
Aluminium, under blowpipe, 73
Anorthite felspar, chemical composition, 34
Aragonite, 49
Bases defined, 76
Basic bricks, 90
dolomite for, 55
magnesite for, 56
Biotite mica, 43
under blowpipe, 73
Black bricks, 101
Blowpipe, 58
Blue bricks, 101
Bluish-black brick-earths, 27
Boulder clay, 50
Bourges, Oxford clay of, 24
Bovey Heathfield clays, 20
Bracknell bricks, 135
Brick earths, artificial mixing, 42
artificial mixtures, 94, 95
bluish-black, 27
boulder clay, 50
brown, 27
chalk pebbles in, 50
changes in character on being dug into, 2, 5, 10
chemical composition of, 23, 52, 83, 84, 85
chemistry of, 58, 75
chert in, 41, 42
coprolites found in, 51
Cornwall, 35
Crayford, 1
Devon, 35
Erith, 1
estuarine, 21
fluviatile--Chapter I., 1–16
fossil shells in, 50
Ilford, 1
Kimeridge clay, 26
lacustrine--Chapter II., 17–21
Lincolnshire, 21
London clay, 33
marine, 22
mineral constitution, 28
minerals found in (see Kaolin, Felspar, Quartz, Flint, Mica, Iron,
Calcite, Aragonite, Selenite, Dolomite, Salt, etc.).
Northamptonshire, 21
North-Eastern France, 20
Oxford clay, 33
Reading mottled clay, 19
of river terraces, 12
salt in, 25
sea-shore, 25
section of fluviatile brick-earths, 10
several kinds of fluviatile, discussed, 14, 15
Switzerland, 89
Thames Valley, 1, 2, 3, 4, 5
value of chemical analyses of, 28, 29
Brickmaking: earths suitable for (see Brick-earths)
Bricks, abrasion tests, 146
absorption of, 132
basic, 90
Bracknell, 135
colour of, 100
Dinas, 81
discolouration of, 114
durability of, 103
effect of conflagrations on, 117
efflorescence on, 110
London stock, 97
micro-structure of, 29, 118, 128
rubber, 29
specific gravity, 146, 149
Staffordshire blue, 99
Stourbridge, 82
strength of, 136
vegetable growth on, 113
weathering of, 105, 113
British Museum, fossils in, from brick-earths, 3, 26
Bronzite, 69
Brown brick-earths, 27
Burning bricks, 94
changes produced by, 98
temperature, 89
Calc spar, 49
Calcite, 39, 49
behaviour in kiln, 39
micro-structure of, 131
under blow-pipe, 74
Californian magnesite, 56
Carbon dioxide in quartz, 41
Carbonate of lime (see Calcite, Aragonite)
Chalk in brick-earths, 1
mixed with brick-earths, 53
pebbles in brick-earths, 50
Chateauroux, Oxford clay of, 24
Chemical affinity, 76
analyses of brick-earths, 28
analysis, 77
composition of air, 106
composition of brick-earths, Dinas, 52
composition, china clays, 78
composition of fire-clays, 80
composition of Kieselguhr, 92
composition of magnesian limestones, 90
composition, pottery clays, 82
composition of slates, 87
disintegration of rocks, 20
re-agents, 60, 63, 71
Chemistry of brick-earths, 58, 75
Chert, 41
Cheshire, salt in clays in, 25
China-clays, behaviour in the kiln, 36
chemical composition, 78
Cornwall, 35, 36, 37
Devon, 35
China-clay (see Kaolin and Felspar)
thickness of, 38
China-stone, decomposed, 37
Colour in the kiln, 98, 99
Colouring matter of bricks, 45
of bricks, 53
Colour of bricks (see Blue, Black, etc.).
Coprolites: impure varieties of phosphate of lime
found in brick-earths, 51
Cornish granite, 35
Cornwall, china-clays, 35, 36, 37
Cracks formed in bricks, 52
Crayford, brick-earth at, 1
Dartmoor granite, 55
Denudation, agents of, described, 6, 7
of sea-cliffs, 22
Devon, china-clays, 35
Diatomaceous earth, 42, 91
Dinas bricks, 52, 81
Discolouration of bricks, 114, 135
Dolomite in brick-earths, 55
micro-structure of, 131
under blow-pipe, 74
Drying bricks, 94
Durability of bricks, 103
Efflorescence on bricks, 110
Electric furnace, 33
Elephants’ remains, found in brick-earth, 2, 3
Erith, brick-earth at, 1
Estuarine brick-earths, 21
Expansion of bricks and variations of temperature, 115
Felspar, 34
chemical composition of, 34
micro-structure of, 129
under blow-pipe, 73
Ferruginous matter (see Iron)
Fire-bricks, Dinas, 52
earths suitable for making, 21
effect of lime in, 53
Kieselguhr for, 42, 91
strength of, 136
Fire-clays, chemical composition of, 80, 81
Newcastle-on-Tyne, 80
tests, 148
Welsh localities, 81
Fishes, fossil, 25
Flint, 39, 41
behaviour of in the kiln, 42, 43
implement: an implement, or tool, made of flint--in the sense
indicated in this work an implement made by pre-historic man.
implements, found in brick-earths, 3, 5
micro-structure of, 129
origin of, 41
Fluid inclusions in quartz, 41
Fluorine in clays, 59
Fluviatile brick-earths: brick-earths that have been deposited in
rivers
Fossil shells, carbonate of lime in, 50
shells found in brick-earths, 4
sponges, in flint, 42
Fusion of brick-earths in the kiln, 29, 31
Gault clay, 51
Glaze, micro-structure of, 119, 120
Glazing, salt, 57
Granite, Cornish, 35
Dartmoor, 35
Granites, weathering of, 36
Greece, magnesite in, 56
Green bricks, 101
Grizzly bear’s remains found in brick-earth, 2
Gypsum in brick-earths, 54
under blow-pipe, 74
Heat, bricks affected by, 117
Hippopotamus remains found in brick-earth, 2
Ilford, brick-earth at, 1
Infusorial earth, Tuscany, 92
Iron, 44
a constituent of brick-earths, 44
behaviour in the kiln, 45
bricks, Saarbrücken, 92
micro-structure of, 130
mode of occurrence in brick-earths, 45
under blow-pipe, 73, 74
vapour in the kiln, 46
pyrites, 46, 131
pyrites, behaviour in the kiln, 48
pyrites, under blow-pipe, 74
pyrites, weathering of in bricks, 48
Jurassic estuarine clays, 21
Kangaroo rats, fossil, 25
Kaolin: a hydrous silicate of alumina, derived chiefly from the
decomposition of felspars
Kaolin, 31
behaviour in the kiln, 32, 33
chemical composition of, 78
micro-structure, 32, 33
under blow-pipe, 73
“Kaolinised” matter, 33
Kilns, temperature in, 98
Kieselguhr: a diatomaceous earth
Kieselguhr, 91
chemical composition of, 92
of the Isle of Skye, 42
Kimeridge clay brick-earth, 26
Labradorite felspar, chemical composition, 34
Lacustrine brick-earth: that laid down or deposited in lakes
brick-earths--Chapter II., 17–21
brick-earths, formation of, 17, 18
Lime, builder’s, 52
in bricks, 52
in manufacture of fire-bricks, 53
Limestone, a flux, 54
Limonite, under blow-pipe, 73
Lincolnshire brick-earths, 21
Loam: sandy clay
London stock bricks, 97, 140
Magnesian limestones, chemical composition of, 90
limestone (see Dolomite)
Magnesite, 55
behaviour in the kiln, 56
Californian, 56
in Greece, 56
Styrian, 56
under blow-pipe, 74
Malachite, 67
Malm bricks, 53, 86
Manganese, under blow-pipe, 74
Marcasite, 46, 47
behaviour in the kiln, 48
weathering of, 47, 48
Marine brick-earths: those laid down or deposited on the sea-floor
Marine brick-earths, not so variable in character as river,
lacustrine, or estuarine, 23
brick-earths--Chapter III., 22–27
brick-earths, origin of, 23
Marl: clay containing much lime.
Mica, 43
behaviour in the kiln, 44
micro-structure of, 130
under blow-pipe, 73
Microscopes, 121
Microscopes, use of, 59
useful in analysing earths, 30
Micro structure as a means of determining fusibility of minerals and
brick-earths, 43
of bricks, 118, 128
Minerals, their behaviour in the kiln (see Kaolin, Felspar, Quartz,
Flint, Mica, Iron, Calcite, Aragonite, Selenite, Dolomite,
Salt, etc.).
behaviour under the blow-pipe (see Quartz, Felspar, Mica,
Calcite, etc.).
Mississippi, sediments of the Delta of, 7
Mortar and Scum, 112
Muscovite mica, 43
mica, under blow-pipe, 73
Musk-sheep remains, found in brick-earth, 2, 3
Natrolite, 68
Newcastle-on-Tyne fire-clays, 80
Newton Abbot, clays near, 20
Northamptonshire brick-earths, 21
Oligoclase felspar, chemical composition, 34
felspar, under blow-pipe, 73
Origin of fluviatile brick-earths--Chapter I., 1–16
Orthoclase, 69
felspar, chemical composition, 34
felspar, under blow-pipe, 73
Overburden: the material for the most part useless, overlying the good
brick-earth, sand, limestone, or other rock for which the pit
or quarry was exploited, and which, in the majority of cases,
has to be removed to obtain the material sought for.
Oxford clay, 24, 25, 33
Oxidising flame, 65
Paving bricks, tests, 148
Peterborough bricks, 24
clays, 51
Plants, fossil, 21, 26
Platinum wire, 60, 63, 66
Plesiosaurus, fossil reptile, 26
Porcelain earths, 30
Pottery clays, chemical composition, 82
Power of transport of sediment by rivers, 8
Pumice for brickmaking, 93
Pyrite, 46
behaviour in the kiln, 48
under blow-pipe, 74
Pyrometers, 99, 100
Quartz, behaviour in the kiln, 39, 42, 43
cavities in, 40, 41
characters of, 39
imperishable, 40
micro-structure of, 128
occurrence in brick-earths, 40
under blowpipe, 72
vein, 40
Race: concretions of carbonate of lime, commonly found in brick-earths
in brick-earths, 50
Rainfall and the durability of bricks, 108
“Rattling” tests, 148
Reading mottled clay, 18
Red brick, 100
Red brick clay, 86
Red bricks, colouring matter of, 45
Reducing flame, 65
Refractory minerals (see Calcite, Dolomite, Magnesite, Quartz, etc.).
Reindeer remains, found in brick-earth, 2, 3
Reptiles, fossil, 25
Rhinoceros’ remains, found in brick-earth, 2, 3
River deposits, typical section, 10, 11
River terraces, brick-earths of, 12, 13
Rock crystal, 40
Rock salt, under blow-pipe, 74
Ruabon bricks and terra-cotta, 84
terra-cotta, 116
Rubbers, 29, 86
Saarbrücken “iron bricks,” 92
Salt, a powerful flux, 57
behaviour in the kiln, 57
glazing, 57
in brick-earths, 25, 27, 56
in quartz crystals, 41
under blow-pipe, 74
Schorl, 40
Scum, 110
Sea-shore, brick-earths from the, 25
Selenite, 54, 131
under blow-pipe, 74
Septaria: tabular or rounded concretions of argillaceous limestone,
commonly found in clays
Septaria, 51
Shrinkage of brick-earth in the kiln, 85
Silica, behaviour in the kiln, 28
group of minerals, 39
Slates, chemical composition of, 87
débris for brickmaking, 87
refuse, 47
used in brickmaking, 47
Snails, found in brick-earth, 4
Specific gravity of bricks, 146, 149
Stacking in the kiln, 97
Staffordshire blue bricks, 99
Stibnite, 68, 70
Stocks, London, 140
Stoneware, earths for making, 21
Stourbridge bricks, 82
Strength of bricks, 136
Styrian magnesite, 56
Swiss brick-earths, 89
Temperature and weathering of bricks, 115
in kilns, 98
Terra-cotta earths, 19, 30
earth, chemical composition of, 84
expansion of in weathering, 115
Ruabon, 116
Tests for bricks (see strength, absorption, specific gravity, chemical
composition, micro-structure, etc.).
Thames, mineral salts in solution in the, 7
Thames Valley brick-earths, 1, 2, 3, 4, 5
Tuscany, infusorial earth, 92
Variable character of brick-earths, 10
Variability in character of marine brick-earths, 23, 24
of estuarine brick-earths, 21
of lacustrine brick-earths, 17
Vegetable growth on bricks, 113
Vein quartz, 40
Volcanic ejectamenta for brickmaking, 93
Wales, fire-clays of, 81
Warping, 98
“Weathering” agents which affect bricks, 6
Weathering of brick-earths, 27
White bricks, 100
Yellow bricks, 101
[Illustration]
Transcriber’s Notes
As Footnote 1 states, technical terms are explained in the Index at the
end of the book.
Punctuation and spelling were made consistent when a predominant
preference was found in the original book; otherwise they were not
changed.
Inconsistent hyphenation was not changed.
Simple typographical errors were corrected; unbalanced quotation
marks were remedied when the change was obvious, and otherwise left
unbalanced.
Figures 1 and 4 were repositioned slightly in the paragraphs that
reference them, thereby splitting those paragraphs.
The uncaptioned illustration above the second advertisement is an image
of that advertisement. The uncaptioned illustration at the end of the
book is decorative.
In this Plain Text version of the eBook, the chemical formulas on pages
76–77 are shown unsubscripted, e.g., H2O.
The original book used middle-dots to represent decimal points; this
eBook uses baseline periods.
The index was not checked for proper alphabetization or correct page
references.
End of Project Gutenberg's The Science of Brickmaking, by Georg F. Harris