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Unformatted text preview: om mud, dirt, oil, organic deposits,
or other foreign material which may prevent a tight bond between the
Seams shall be cleaned to a suitable depth and to firm
rock and concrete.
rock along the side. Where excavation methods or the natural rock strata
do not leave a sufficiently rough surface of contact, the bed shall be
roughened by cutting steps. grooves, trenches, or keyways into the solid
rock. Scaly coatings, hardened grout or concrete, construction debris,
and other objectionable materials shall be removed. Seepage shall be
The foundation bed and sides shall be
properly controlled and diverted.
carefully cleaned with stiff brooms, picks, jets of water and air applied
at high velocity or other equally effective means, followed by thorough
washing. After washing and before placing any concrete, water shall be
removed from del’ressions and the rock surface shall be left uniformly
4.9.3 All flat surfaces shall then be coated with mortar about 1.5 cm
( or 4 in ) thick in the case of concrete surfaces and 2 cm ( or 2 in ) thick on
rock surfaces. The water-cement ratio for the mortar layer shall not
exceed that for the regular contrite mixture, and the mortar shall be of
such consistency that it can be spread evenly without flowing. It shall be
16 IS : 457 - 1957
thoroughly broomed and worked into all irregularities,
cracks and crevices.
The manner of spreading and working shall be such as not to cause any
segregation, and concrete shall be placed immediately
upon the fresh mortar
before its initial .set.
4.9.4 On very rough or broken surfaces, the first few batches
crete may, if so required, contain only about one-half the regular
tion of coarse aggregate. of conpropor- 4.9.5 No concrete shall be deposited until the foundation
inspected and approved.
Where the rock is dry enough to absorb water
from the mortar layer, it shall be soaked for at least 24 hours prior to
placing the concrete.
shall be issued for preparing
scaly or cracked foundations
requiring special treatment
4.9.6 Ear& OY Shale Foundations 18.104.22.168 In the case of earth or shale foundations,
mui and surface debris shall be scraped and removed.
be moistened to a depth of about 15 cm ( or 6 in ) to prevent
water from the fresh concrete.
concrete, the surface of the earth shall be tamped or otherwise
general, concrete shall be deposited only upon material lying
state. soft or loose
in a natural, 22.214.171.124 Foundations
of porous or free-draining
compacted by flushing and by subsequent
tamping or rolling,
The finished foundation
surface shall then be blanketed with
a layer of tar paper or closely woven burlap carefully lapped and fastened
down along the seams so as to prevent the loss of mortar froni the concrete.
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- Fall '13