REPAIR AND REHABILITATION OF STRUCTURES
GROUTING – REPAIR TECHNIQUE
GROUT is a mixture of water, cement and optional material like
sand, water reducing admixtures, expansion agents and
pozzolans
The water to cement ratio is around 0.5.
Fine sand is used to avoid segregation.
Generally, a fluid prepared from a mixture of sand, cement,
water, or a liquid prepared from a mixture of chemical
substances for waterproofing is called grout.
But gravel is also used in grout along with sand, cement, and
water to strengthen large areas like the core of concrete blocks.
Grouting
Grouting is the process of placing a material into cavities in
concrete or masonry structure for the purpose of
•increasing the load bearing capacity of a structure
•restoring the monolithic nature of a structural member,
•filling voids around pre cast connections steel base plates,
•stopping leakages,
•placing adhesives and soil stabilization
Grout materials are used in a variety of ways to strengthen
building structures during construction. such as pile
foundation, ground anchor, under reaming, dam construction,
road construction, etc.
Apart from this, grout is also used to overcome the problem of
water seeping into the roof and exterior walls of the building
and to fix the tiles to the floor and walls.
Categories of Grout:
1. Suspension Grout
2. Liquid Grout or Solution Grout.
Suspension grout is a mixture of one or several inert materials
like cement, clays etc suspended in a fluid i.e water
Suspension grout is a mixture of pure cement with water
Liquid grout or solution grout consists of chemical products in
a solution or an emulsion form and their reagents
The most frequently used products are sodium silicate and
certain resins categories of grout
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
1.Chemical grouting
control seepage
shut-off seepage
soil stabilization
2.Cementitious grouting
mass placement
Structural(high strength)
caustic environments
high temperatures
3. Epoxy grouting
Seal cracks
Bolt anchoring
Base plate levelling
Acidic environment
4. Polyesters
Bolt anchoring
5. Silicones
Smoke seals
Fire stops
Applications of grouting
•Repairing of cracks
The wide cracks may be repaired by filling them with
Portland cement grout.
The grout mixture may contain cement and water or cement,
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.
•Strengthening existing walls
The lateral strength of buildings can be improved by
increasing the strength and stiffness of the existing individual
walls, whether they are cracked or not
•Soil stabilization
Common methods are chemical grouting, compaction
grouting, and jet grouting
Types of Grouts
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
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
Durability depending on the quantity and quality of the
components
Easy preparation and availability
Ease of use Relatively low cost mixes
Pure cement grout:
It is an unstable grout. However, bleeding can be avoided
with water cement ratio less than 0.67
Usual mix proportions are from water cement ratio 0.4 to 1
for grouting. Very high mechanical strength can be attained
with this type of grout. During grouting, cement grains deposit
in inter granular voids or fissures is analogous to a kind of
hydraulic filling
The grout usually undergoes a significant filtration effect.
The grain fineness is an important factor for fine fissures
Bentonite cement grout
It is a stable grout. When bentonite is added to a cement
suspension, the effects are
Obtain a homogeneous colloidal mix with a wide range of
viscosity.
Avoid cement sedimentation during grouting
Decrease the setting time
Increase the cement binding time.
Improve the penetration in compact type soils
Obtain a wide range of mechanical strength values.
In water stopping, grout will include a lot of bentonite and
little cement. Ideal mixes should be both stable and easy to
pump
Grouts with fillers
Fillers are added in order to modify the viscosity of a given
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.
The term “mortar” is commonly used to specify grouts with
fillers that have a high sand content. Adding fillers reduces the
grout penetrability, as the fillers are of larger grain sizes.
Grouts with fillers are used when water absorption and/or the
size of voids are such that filling becomes essential and when
the leaking of grout into adjoining areas should be limited.
In addition, fillers in grout will produce low slump grout with
high viscosity for certain grouting purposes.
Applications of Grout
It is used to repair machine foundations, base plates, load-
bearing, and pillar joints in prefabricated structures.
Grouting is used to fill gaps, cracks in concrete structures.
Used for repairing footpaths and the ground under
foundations.
Defects in masonry and cracks in concrete are repaired by
grouting.
Used in soil stabilization.
Used to control water leakage in mines, tunnels, dams,
underground structures.
Grouting is used to repair unusual and difficult geotechnical
and structural problems
Used to aid in the excavation process.
