rete, broken stone or slag macadam, or of brick laid flat, the first named b

quired temperature they will fuse into a glassy texture. Brick roads are constructed on roads carr

road construction, and paving brick, even though truly vitrified, are of different degrees o

through the dies, which form the prism from which the brick are cut. If the clay is unsuitable in character or is not properly ground and mixed, the brick will possess planes of weakness between the various layers of

d therefore not of maximum durability. It is customary to specify that

ng are often encountered, but unless these are deep, that is 3/16 inch or more, they do not impair the wearing quality of the brick, nor indicate structural weakness. Kiln marks are formed

the brick for the filler. These lugs or letters are not less than 1/8 inch nor more than ? inch high a

are to be had, the difference bein

en brick, after it has been cut to size, into a mold on one face of which are recessed

ing lug, it being contended that the irregularities of the brick are such as to provide all of the space required. In practice this does not always work out, as the brick are so regular in shape that w

ided by cutting one face in a special manner which provided lugs for spacing. In this

nd 30.5 revolutions per minute. The duration of a test is 1800 revolutions. Ten brick constitute a charge and these are placed in the rattler along with 300 lbs. of cast iron spheres. The spheres are of

the loss allowable for the severa

rage Loss M

any

per cent

per cent 2

per cent

ll pass the rattler tests which fails to pass a reasonable absorption test. Absorption of water in an amount exceedi

Failure in service more frequently occurs from excessive wear than from any other cause and the cross breaking tes

For well drained soils and normal highway traffic, 5 inches is the ordinary thickness of foundation. Under favorable conditions such as locations with sandy soils or in semi-arid or arid re

tandard thickness of foundation that will be equally economical for all locations and all kinds of traffic. As the brick pavement is essentially a heavy traffic type of surface, the design cannot be varied greatly with similar foundation conditi

gregate would insure concrete of adequate strength. A somewhat leaner mixture is sometimes employed and would be satisfactory if the aggregates were of exceptional concrete making quality. Mixtures of sand and pebbles (unscreened gravel) may also be used if car

loads that are expected to use the road. The macadam is placed in a single layer and is rolled and bonded with screenings as described in the chapter dealing with water-bound macadam. Six inches is a common thickness for the macadam base. This type of foundation should be employed only where

his is permissible are comparatively few in number. When an old macadam is to be used it is reshaped to the

rse for Bri

terial into which the brick may be forced by rolling. In this way the upper surfaces of all brick can be brought to

even because the brick have pushed down into the sand after the pavement was used for a time. The sand for the bedding course should preferably be fine grained, all particles passing the e

Sections for

, a lean cement mortar is sometimes employed rather than the straight sand. Sand and cement in the ratio of one part cement to four or five parts of sand

rick are laid directly on the green concrete base before the concrete has taken a set a

for Bric

ting to the bedding course. A suitable filler must adhere to the brick and fill completely the spaces between them. It must withs

of Portland cement and fine sand. When properly mixed and applied the grout filler meets all requirements

nd consequently solid at ordinary temperature. They are poured into the joints hot and when they cool are firm enough to comply with the

ture is prepared at high temperature and is worked into the joints between the brick while hot. When cool it resembles th

sion

ension in the brick, but when the grout filler is used either the expansion joint must be provided or the pavement must be designed to withstand the compression due to expansion of the brick. Expansion

ourses of brick at the place where a joint is required. After the pavement has been groute

the bedding course in place. The curb is usually constructed integral with the base and of concrete of the same mixture as the

ion of th

ompletely than for a less costly type of surface since it does not pay to jeopardize the stability of the pavement by fail

here are places where the soil will not compact properly under rolling, these places are corrected by

mixer is employed which is drawn along the road as the work progresses, the materials being placed directly in the mixer. If stored at a central point, they may be transported to the

hinery. If the marginal curb is to be employed, it is constructed immediately afte

d and cement are mixed dry and spread to prescribed thickness. It is considered to be desirable to roll the sand bedding course with a light hand roller before the brick a

th spacing lugs are employed, and with the lugs in contact with the brick of adjoining courses. If brick without spacin

and replaced with good brick and after this culling has been completed the surface is once more thoroughly rolled. If a cement-sand bedding course is employed, the surface is sprinkled just after the final rolling so that water will flow down between the brick and moisten the bedding course sufficiently to caus

poured onto the surface and worked into the joints by means of squeegees, with comparatively little material left on t

is mixed to a thin consistency and poured onto the surface and is then worked into the joints with squeegees. Two or more applications are usua