without absorbing moisture and compromising the bond?
2.6.6.4 Parameters of cement and chemical grouts—
a) Cement grouts—Cement and other grouts containing
solids in suspension can be used only where the width of the
opening is sufficient to accept the solid particles. For the
reliable penetration of neat grouts (hydraulic cement mixed
with a latex with or without pozzolans and other admixtures)
mixed with approximately 83 L of water to 100 kg (10 gal.
per 100 lb) of solids (water-to-solids ratio of approximately
0.8), minimum crack width at the point of introduction
should be approximately 3 mm (0.1 in.). With flow started in
the opening, such grout penetrates through cracks 0.25 mm
(0.01 in.) wide. As crack widths increase to 6 mm (0.25 in.)
or more, the mixing water may be reduced to 42 to 50 L/100 kg
(5 to 6 gal. per 100 lb) of solids (water-to-solids ratio of
approximately 0.4 to 0.5), especially when water-reducing
admixtures are used. For openings of 12 mm (0.5 in.) or
more and for interior voids, grouting sand or masonry sand
ranging from one to two times the mass or volume of the
cementing material can be included. Fine aggregate meeting the requirements of ASTM C 33 can also be used when
filling large voids.
Finely ground specialty cements and silica fume moves
into finer openings more readily than normal hydraulic
cements, but definitive information on the penetrability of
these materials into cracks and joints is limited.
Hydraulic cement grouts are excellent for reintegrating
and stabilizing cracked structures, such as bridge piers,
tunnel linings, or walls, where reestablishing compression
and shear strength is the main goal. Cement grouts also
provide some tensile bond, but tensile strength is difficult to
predict. Expansive cement grouts are widely used to prevent
water movement (ACI 223).
b) Chemical grout—Chemical grouts should be considered
under two categories according to whether they harden to a
rigid condition or to a flexible gel or foam. Epoxies and
acrylates are examples of rigid types; polyurethane is an
example of a gel.
Rigid chemical grouts bond exceedingly well to dry
substrate and some bond to wet concrete. These grouts can
prevent all movement at an opening and restore the full
strength of a cracked concrete member. If tensile or shear
stresses exceeding the capability of the concrete recur after
grouting, however, new cracks appear in the concrete near,
but generally not at, the grouted crack. Rigid grouts can
penetrate cracks somewhat finer than 0.05 mm (0.002 in.),
the penetration being dependent on viscosity, injection
pressure, temperature, and grout set time.
The principal use for gel-type chemical grouts is to shut
off or greatly reduce water movement. Gel grouts do not
restore strength to a structure, but they generally maintain
water tightness despite minimal movement across a crack.
Most gel grouts are water solutions and therefore exhibit
shrinkage if allowed to dry, but they do recover when
rewetted. Some gel grouts can be formulated at consistencies
so near that of water that they can be injected into any
opening through which water flows. Others can be made to
yield a foam that can be used in openings approximately
100 mm (4 in.) wide.
2.6.7 Underwater placement—Placing concrete directly
underwater by means of a tremie or pump is a frequently
used repair method. In general, the same requirements for
material and procedures that apply to new construction also
apply to repair placements underwater. Underwater repairs
are presented in ACI 546.2R. Placing concrete under water
by tremie and by pump is covered in detail in ACI 304R.
Preplaced-aggregate concrete is frequently used on underwater
repair projects. The concrete mortar is pumped from
the bottom of the placement, displacing the water as it rises.
The use of preplaced-aggregate concrete is covered in ACI
304.1R and ACI 546.2R
without absorbing moisture and compromising the bond?2.6.6.4 Parameters of cement and chemical grouts—a) Cement grouts—Cement and other grouts containingsolids in suspension can be used only where the width of theopening is sufficient to accept the solid particles. For thereliable penetration of neat grouts (hydraulic cement mixedwith a latex with or without pozzolans and other admixtures)mixed with approximately 83 L of water to 100 kg (10 gal.per 100 lb) of solids (water-to-solids ratio of approximately0.8), minimum crack width at the point of introductionshould be approximately 3 mm (0.1 in.). With flow started inthe opening, such grout penetrates through cracks 0.25 mm(0.01 in.) wide. As crack widths increase to 6 mm (0.25 in.)or more, the mixing water may be reduced to 42 to 50 L/100 kg(5 to 6 gal. per 100 lb) of solids (water-to-solids ratio ofapproximately 0.4 to 0.5), especially when water-reducingadmixtures are used. For openings of 12 mm (0.5 in.) ormore and for interior voids, grouting sand or masonry sandranging from one to two times the mass or volume of thecementing material can be included. Fine aggregate meeting the requirements of ASTM C 33 can also be used whenfilling large voids.Finely ground specialty cements and silica fume movesinto finer openings more readily than normal hydrauliccements, but definitive information on the penetrability ofthese materials into cracks and joints is limited.Hydraulic cement grouts are excellent for reintegrating
and stabilizing cracked structures, such as bridge piers,
tunnel linings, or walls, where reestablishing compression
and shear strength is the main goal. Cement grouts also
provide some tensile bond, but tensile strength is difficult to
predict. Expansive cement grouts are widely used to prevent
water movement (ACI 223).
b) Chemical grout—Chemical grouts should be considered
under two categories according to whether they harden to a
rigid condition or to a flexible gel or foam. Epoxies and
acrylates are examples of rigid types; polyurethane is an
example of a gel.
Rigid chemical grouts bond exceedingly well to dry
substrate and some bond to wet concrete. These grouts can
prevent all movement at an opening and restore the full
strength of a cracked concrete member. If tensile or shear
stresses exceeding the capability of the concrete recur after
grouting, however, new cracks appear in the concrete near,
but generally not at, the grouted crack. Rigid grouts can
penetrate cracks somewhat finer than 0.05 mm (0.002 in.),
the penetration being dependent on viscosity, injection
pressure, temperature, and grout set time.
The principal use for gel-type chemical grouts is to shut
off or greatly reduce water movement. Gel grouts do not
restore strength to a structure, but they generally maintain
water tightness despite minimal movement across a crack.
Most gel grouts are water solutions and therefore exhibit
shrinkage if allowed to dry, but they do recover when
rewetted. Some gel grouts can be formulated at consistencies
so near that of water that they can be injected into any
opening through which water flows. Others can be made to
yield a foam that can be used in openings approximately
100 mm (4 in.) wide.
2.6.7 Underwater placement—Placing concrete directly
underwater by means of a tremie or pump is a frequently
used repair method. In general, the same requirements for
material and procedures that apply to new construction also
apply to repair placements underwater. Underwater repairs
are presented in ACI 546.2R. Placing concrete under water
by tremie and by pump is covered in detail in ACI 304R.
Preplaced-aggregate concrete is frequently used on underwater
repair projects. The concrete mortar is pumped from
the bottom of the placement, displacing the water as it rises.
The use of preplaced-aggregate concrete is covered in ACI
304.1R and ACI 546.2R
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