GROUTING AND GUNITING

GROUT
▪ a construction material used to Initially, its application confines mainly
embed rebars in masonry walls, in void filling, water stopping and
connect sections of pre-cast consolidation. Nowadays, it extends
concrete, fill voids, and seal joints
(like those between tiles). ▪ to alleviate settlement of ground
caused by basement and tunnel
▪ is generally a mixture of water, excavation works,
cement, sand, often color tint, and
sometimes fine gravel (if it is being ▪ to strengthen ground so that it can
used to fill the cores of cement be used as a structural member
blocks). ▪ or retaining structure in solving
▪ is applied as a thick liquid and geotechnical problems
hardens over time, much like
mortar.
GROUTING
Grouting is the process of placing a material into cavities in
concrete or masonry structure for the purpose of-
— increasing the load bearing — filling voids around pre cast ▪ The water to
capacity of a structure, connections steel base plates, cement ratio is
— restoring the monolithic nature of a — stopping leakages, around 0.5.
structural member, — placing adhesives and
— providing fire stops, — soil stabilization.
▪ Fine sand is used to
avoid segregation.
Sand /
Water reducers /
Grout = Water + Cement optional + Expansion agents /
pozzolans
CATEGORIES OF GROUT
▪ Suspension grout is a ▪ Liquid grout or
mixture of one or solution grout consists
several inert materials of chemical products in
like cement, clays etc a solution or an
suspended in a fluid i.e emulsion form and their
water. Suspension grout reagents. The most
is a mixture of pure frequently used
cement with water. products are sodium
silicate and certain
resins.
PROPERTIES OF GROUT
▪ Fluidity
▪ Minimum bleeding and segregation
▪ Low shrinkage
▪ Adequate strength after hardening
▪ No detrimental compounds
▪ Durable
SPECIFICATION FOR GROUT
▪ The sand should pass 150 μm IS sieve
▪ The compressive strength of 100 mm cubes of the grout shall not be less than 17
N/mm² at 7 days
TYPES OF GROUTING MATERIALS AND
THEIR USE
▪ Chemical grouting ▪ Epoxy grouting
—control seepage —seal cracks
—shut- off seepage —bolt anchoring
—soil stabilization —base plate levelling
—acidic environment
▪ Cementitious grouting
—mass placement ▪ Polyesters
—structural(high strength) —bolt anchoring
—caustic environments
▪ Silicones
—high temperatures
—smoke seals
—fire stops
 APPLICATIONS OF GROUTING
Repairing of cracks Strengthening existing walls For soil stabilization
▪ The wide cracks may be The lateral strength of buildings Common methods are
repaired by filling them with can be improved by increasing the —chemical grouting
portland cement grout. strength and stiffness of the —compaction grouting
▪ The grout mixture may contain existing individual walls, whether —jet grouting
cement and water or cement, they are cracked or uncracked.
sand and water, depending
upon the width of crack.
▪ The water cement ratio should
be kept as low as practicable
to maximize
▪ strength and minimize shrinkage
APPLICATIONS OF GROUTING
Used for soil stabilization - Common methods are:
chemical grouting compaction grouting jet grouting
TYPES OF GROUTS
▪ Durability depending on the quantity and quality of the components
▪ Easy preparation and availability
▪ Ease of use
▪ Relatively low cost mixes
TYPES OF GROUTS
1. Cement-based Grouts:
▪ Cement-based grouts are the most frequently used in both water stopping and
strengthening treatment. They are characterized by their water cement ratio and
their Total Dry Matter / Water weight ratio. The properties and characteristics of
these grouts vary according to the mix proportions used. However, they have the
following properties and characteristics in common.
▪ Stability and fluidity according to the dosage of the various components and their
quality
▪ Unconfined compressive strength linked to water cement ratio
TYPES OF GROUTS 1/3
1. Cement-based Grouts 2. Pure cement grout
▪ Cement-based grouts are the most frequently ▪ It is an unstable grout. However, bleeding
used in both water stopping and can be avoided with water cement ratio less
strengthening treatment. They are than 0.67.
characterized by their water cement ratio
and their Total Dry Matter / Water weight ▪ Usual mix proportions are from water cement
ratio. The properties and characteristics of ratio 0.4 to 1 for grouting. Very high
these grouts vary according to the mix mechanical strength can be attained with this
proportions used. However, they have the type of grout.
following properties and characteristics in
common. ▪ During grouting, cement grains deposit in
inter-granular voids or fissures is analogous
▪ Stability and fluidity according to the to a kind of hydraulic filling.
dosage of the various components and their
quality ▪ The grout usually undergoes a significant
filtration effect. The grain fineness is an
▪ Unconfined compressive strength linked to important factor for fine fissures.
water cement ratio
TYPES OF GROUTS 2/3
3. Bentonite cement grout 4. Grouts with fillers

It is a stable grout. When bentonite is added to a cement ▪ Fillers are added in order to modify the viscosity of a given
suspension, the effects are: grout so as to obtain a low cost product to substitute the
cement. The most commonly used fillers are the natural sands
and fly ash from thermal power stations.
▪ Obtain a homogeneous colloidal mix with a wide range
of viscosity. ▪ The term “mortar” is commonly used to specify grouts with
fillers that have a high sand content. Adding fillers reduces
▪ Avoid cement sedimentation during grouting. the grout penetrability, as the fillers are of larger grain sizes.
▪ Decrease the setting time index and separation filtering ▪ Grouts with fillers are used when water absorption and/or
processes. the size of voids are such that filling becomes essential and
when the leaking of grout into adjoining areas should be
▪ Increase the cement binding time. limited.

▪ Improve the penetration in compact type soils ▪ In addition, fillers in grout will produce low slump grout with
high viscosity for certain grouting purposes.
▪ Obtain a wide range of mechanical strength values.
▪ In water stopping, grout will include a lot of bentonite
and little cement. In consolidation works, grout will contain
a lot of cement and little bentonite. Ideal mixes should be
both stable and easy to pump.
TYPES OF GROUTS 3/3
5. Silicate based grouts 6. Soft gels

▪ Slicates based grouts are sodium silicate in liquid form ▪ It is mainly for water stopping purpose. They are gels
diluted and containing a reagent. with a very low dosage in silicate in which the gelling
process is most generally obtained by adding a mineral
▪ Their viscosity changes with time to reach a solid state
that is called the “gel”. reagent

▪ They are used in soils with low permeability values such ▪ Their very low degree of viscosity (close to water)
that all suspension grouts cannot penetrate. According to ensures the injection of very fine sand to achieve the
the type of grout used, the gel obtained will be water- water stopping purpose.

▪ Tightness and/or with strength that are temporary or ▪ Reduction in permeability can be up to 1 x 10-6 m/s
permanent. and, in some case even up to 1 x 10-7 m/s when more
lines of grout holes are added. There is also a slight
▪ When the temperature of a silicate decreases, its
improvement in strength, about 0.2 MPa.
viscosity increases very rapidly. This temperature should
not fall below 0 degree C in order to eliminate any risks
of modification of its properties.
PROCEDURE OF GROUTING
▪ A 1:2 cement-sand grout with a water-cement ratio
between 0.6 and 0.8 is prepared using a mechanical
mixer.
▪ The mixture is then sent down under pressure (of about
120kg/cm²) through a 30-50 mm diameter pipe
terminating into steel cages.
▪ As the grouting proceeds the pipe is raised gradually
upto a height of not more than 60 cm above its starting
level after which it is withdrawn and placed into the next
cage for further grouting by the same procedure.
▪ After grouting the whole area for a height of about 60
cm , the same operation is repeated, if necessary , for
the next layer of 60cm and so on.
Grouting of Tunnel
GROUT MIXER
Grout Mixers. Many types of grout mixers have been used, including hand-turned dough mixers, concrete mixers of various
sizes, and especially designed grout mixers. Any machine is suitable that has the desired capacity and that mixes the grout
mechanically to a uniform consistency.
Two mixers can be arranged to discharge into the same sump to satisfy high capacity requirements. Manual stirring of
cement and clay grouts in a tub is not satisfactory except in emergencies. Handpowered dough mixers are not recommended
because of their limited capacity.
High-speed colloidal-type mixers.
High-speed colloidal-type grout mixers are commercially available in both the single - and double –drum types. These
mixers are equipped with small centrifugal pumps, which cause the grout to circulate at high speed while being mixed.
Particles of cement may be broken and rounded to a significant degree in high-speed mixers. This results in an increase in
pumpability and penetrability for Portland-cement grout. In an emergency, grout can be pumped at low pressures into the
foundation or other places with the centrifugal pumps of these mixers.
Water meters.
A satisfactory water meter is the single-disk type, size 1-1/2 in., and threaded for pipe connection. This type has a 6 -in.
vertical register with a long hand that makes one revolution per cubic foot of water and a short hand that indicates 10 cu ft
per revolution. For use in grouting, the meter should have a reset knob to set the hands to zero and a direct-reading totalizer.
A screen should be provided if sand or rock particles are present in the water supply
AGITATOR SUMPS
▪ After mixing, grout should be agitated to prevent settlement while it is being
pumped. This can be done by pumping the grout into a sump equipped with a
stirring blade.
▪ Agitator should have the same capacity as the mixer so that one batch of grout can
be pumped while the next batch is being mixed. When emptying the grout from the
mixer into the agitator, the grout should pass through a 1/8-in. -mesh screen to
remove pieces of sacks, strings, wire, ties, or other foreign matter that may be
dropped into the mixer.
PUMPS
Pumps for cement grouting should be sufficiently
flexible to permit close control of pressure and to
provide for a variable rate of injection without
clogging of valves and feed lines. With constant
speed pumps, special arrangements of the supply
piping systems and valves are needed to provide
close control of the grouting operation. Constant
speed pumps are powered by electric motors or
internal-combustion engines. Variable speed pumps
are hand operated, steam driven, or air driven.

Grout Agitator
GROUT LINES
a. General. There are two primary arrangements of piping used to
supply grout from the pump to the hole. The simpler of the two is the single-line system. It
consists of a pipe or a hose or a combination of both, extending from the pump to the header
at the hole.
The pump speed controls the rate of injection. The second arrangement is the double -line or
circulating system. This system has a return line from the header to the grout sump in addition
to the pump line of the single -line system. Thus, if the header connection to the hole is closed,
grout can be continuously circulated from the grout sump to the pump, through the pump line,
through the header, and back to the sump through the return line. While grouting, the amount
of grout entering the hole through the header can be varied by opening or closing a valve on
the return line without changing pump speed. The double-line system is generally preferred
because it permits better control of grouting pressures and allows less material to settle out of
the mix to plug the lines
Hose
Flexible hose is most commonly used for suction and discharge lines. If the length of the
discharge line is such that pipe is necessary, a short length of hose should be provided at
the pump discharge and at the connection to the grout header.
Piping
Black steel pipe and fittings 1-1/2 in. in diameter are normally suitable for pressure lines
; but where large quantities of grout are to be injected and the supply line is long, it may
be desirable to provide a larger size pipe and connection hoses.
Grout Header
The grout header is usually assembled as a unit in order—that it may be moved from one
grout hole to another. The assembly consists of the operating valves, a pressure gage,
pipe, and the necessary fittings to attach the header to the hole and to attach the grout
supply and return lines.
Pressure Gages Schematic Plan of Grout Plant
29
Reliable pressure gages are essential in pressure grouting. They constitute the principal
index to the behavior of the hole and the stresses that are being produced in treated
material.
GUNITING
▪ Guniting is an effective technique, which has been ▪ Sand and cement are mixed dry in a mixing
extensively used in the rehabilitation of structurally chamber, and the dry mixture is then transferred
distressed R.C members. There has been case of by air pressure along a pipe or hose to a nozzle,
heavy rusting of the mesh in the form of powder where it is forcibly projected on to the surface to
or in the form of a sheet coming out. Distressing be coated
before restoration is possible only in case of
overheads tanks which can be restored when the ▪ Water is added to the mixture by passing it
tanks are empty. through a spray injected at the nozzle
▪ Gunite is also known as shotcrete or pneumatically ▪ The flow of water at the nozzle can be controlled
applied mortar to give a mix of desired stiffness, which will
adhere to the surface against which it is projected
▪ It can be used on vertical and overhead, as well
as on horizontal surfaces and is particularly useful ▪ A cement-sand mix, in the ratio 1:2 or 1:3 depending
for restoring surfaces spalled due to corrosion of upon the requirement, is applied at high pressure
reinforcement over the surface with the help of specialized
equipment.
▪ Gunite is a mixture of Portland cement, sand and
water, shot into the place by compressed air ▪ Guniting is extensively used to rehabilitate concrete
bridges, dams, spillways, buildings, marine structures,
etc.
SPRAYING OF CONCRETE
▪ There are two different methods of ▪ It is because of its fast application process
spraying: and restoration of structural strength at an
—Dry process spraying early stage.
—Wet process spraying ▪ The performance characteristics of dry
sprayed concrete are they have good
▪ Dry process spraying is the process in which density and high strength.
the mixture of damp sand and cement is
passed through the delivery hose to the ▪ It has very good bond to a suitable
nozzle and the water is mixed at that time. substrate.
▪ Water cement ratio should be between 0.33 ▪ These advantages make it more variable
and 0.50 than conventional concrete and wet process
sprayed concrete.
▪ This process is often used for repair work.