Page 48 - Construction Waterproofing Handbook

2.12 CHAPTER TWO
Backfilling should take place as soon as possible after installation; using the available
site soil is acceptable. Backfill should be compacted as required by specifications using
plate vibratory compactors. Caution should be taken during compaction not to damage the
fabric material.

WATERSTOPS

Whenever a construction joint occurs in a below-grade concrete structure, a waterstop
should be installed in the joint to prevent the transmission of water through the joint.
Construction joints, also referred to as “cold-joints,” occur when one section of concrete
is placed and cured or partially cured before the adjacent concrete placement occurs. This
occurs frequently in concrete structures at locations including

● Transitions between horizontal and vertical components
● When formwork is insufficient to finish the structure in one placement, such as long
lengths of wall area
● Where design elements require a change in form design
● When concrete placement is stopped, for schedule reasons or end of workday
In most of these cases a joint is not actually formed; the cold or construction joint ref-
erence refers to the area of concrete structures where two different concrete placements
have occurred (properties of concrete preventing it from forming an excellent bond to itself
and the previously placed concrete). In addition, control joints are added to a poured-in-
place concrete structure to control cracking that occurs from shrinkage in large place-
ments. Control joints are typically recommended for installation at no more than 30 ft
apart. The joints are typically the weakest points of the concrete structural components, but
not subject to movement other than structural settlement.
Below-grade conditions present conditions that make it very likely that water, which is
present under hydrostatic pressure, will infiltrate through these construction joints. To pre-
vent this from occurring, waterstops are commonly specified for installation at every con-
struction joint on concrete work below-grade. The capability of waterstops to prevent
infiltration at these weak points in the structure is critical to successful waterproofing of
below-grade structures, so their importance should never be underestimated.
Waterstops are used for waterproofing protection on a variety of below-grade concrete
structures including

● Water treatment facilities
● Sewage treatment structures
● Water reservoirs
● Locks and dams
● Basement wall and floors
● Parking structures
● Tunnels
● Marine structures