GROUTING

Grouting is generally a mixture of cement, sand and water or chemical used to fill gaps or used as reinforcement in existing structures.

The purpose of grouting can be either to strengthen a formation or to reduce water flow through it. It is also used to correct faults in concrete and masonry structures

Applications of grouting

1.   For grouting machine foundation, base plate, bearing and column joints in precast construction

2.   It is used for filling voids, gaps and cavities in the concrete

3.   Grouting is done for filling the voids between the rock face and lining in tunnel work

4.   It is used for fixing tendons post-tensioned in prestressed concrete construction.

5.   It is used for repairing pavement and ground below the foundation.

6.   It is used for repairing cracks in concrete and defects in masonry

 7.  Also, for fixing ground anchors for concrete pile wall.

The process of grouting consists of filling pores or cavities in soil or rock with a liquid form material to decrease the permeability and improve the shear strength by increasing the cohesion when it is set. Cement base grout mixes are commonly used for gravely layers or fissure rock treatment.

TYPES OF GROUTS

1. Cementitious Grouts

Cementitious grout is used to create a solid bearing surface between structural baseplates and base foundations. It enables even dispersal of the load into the existing concrete slab. Cementitious grout is suitable for a range of different bedding and fixing applications.

a) Ordinary Portland cement grouting

It is commonly used for repairing concrete cracks. Since they have the particulate size of 15 microns they can help in filing the wider cracks.

b) Micro-fine cement grouting

Finely ground slag, fine fly ash, or Portland cement are mixed with water to allow penetration into the fine cracks. They have the particulate size in the range of 6 to 10 microns.

 c) Ultra-fine cement grouting

This grout is used for sealing the very fine hairline like cracks and have the particulate size of 3 to 5 microns. They are used for stabilizing waste plumes.

d) Sanded grout 

Sanded grout is most commonly used for ceramic tile, stone and any tile with a grout joint or larger. It is composed of Portland cement, sand and other additives, it is mixed with water and troweled into the grout joint, where it takes approximately 24 hours to dry.

For joints 3.175 to 9.525 mm (1/8 to 3/8”) wide, fine sanded grout

For joints 9.525 to 12.7 mm (3/8 to 1/2”) wide, Coarse sand will be used.

e) Unsanded grout 

Unsanded grout, commonly called “wall grout,” is essentially sanded grout without the sand. It is used on ceramic tile and polished marble with grout joints smaller than 1/8 inch.

f) Latex modified grout

Sanded grouts may be formulated with a latex polymer additive, either included in the dry mix or added in as the grout is mixed with water.

2. Chemical grouts

Chemical grouts are an emulsion of water and liquid resin. Chemical grouting requires injection of specially formulated chemical grouts into finer cracks that cannot be possible by cement grouts. Some of the popular ones are epoxy, acrylic and furan resin grouts.

a) Epoxy grout 

Epoxy grout is strong and durable. It is highly resistant to stains, cracks, chemicals, harsh weather conditions, and climate changes. These characteristics make epoxy grout the only way to go if you’re looking for the most durable, efficient way to do tile work.

b)            Acrylic grout 

With acrylic grout is that you don’t have to cover the entire work surface. You can just apply it in the joints between the tiles. The silicone additive, which comes premixed with Portland cement grout, aid¬s in greater adhesion. Because of its stability in freezes and thaws, it can be used outdoors, making it perfect for deck or garage projects.

c)            Furan grout 

Furan grout is similar to epoxies, but are composed of polymers of furfuryl alcohol, which are highly resistant to chemical action. Furans are two-component systems that contain a furan resin and a filler powder with an acid catalyst. It is the acid catalyst that causes the furan resins to cure, forming a thermosetting resin that has unsurpassed chemical, physical and thermal-resistance.

Furan grout is commonly used to grout brick pavers and quarry tile and it is also recommended in areas exposed to chemicals and grease. The tile surfaces may be smooth, non-skid, or abrasive, depending on the intended use for the floor. The tile or brick surfaces must receive a wax coating to protect them from staining prior to the installation of furan

3.            Polyester grouts

For decades, grouting has been the most popular soil stabilization method. Some additives, as well as cement and polymeric materials, are also widely used as grout mixtures in order to lower costs and achieve the best engineering properties with early strength gain. Unconfined compression and dynamic tests of grouted granular soils were conducted with different mixtures to evaluate the feasibility of using polyester, red mud and micronized clay as grouting materials. This type of grouts advances with increasing additive percentages and curing time. Polyester grout is used for anchoring to impart strength to foundations that must be achieved in limited available space.

4.            Non-shrink grout

Non-shrink grouts are hydraulic cement grout that, when hardened under stipulated test conditions, does not shrink, so its final volume is greater than or equal to the original installed volume. It is often used as a transfer medium between load-bearing members. This grout often sets rapidly. It is a pre-mix product that needs only to be mixed with [water] which includes ingredients to compensate against cement stone shrinkage

G1 Grout

It is mainly used for steel structures, small pumps, ships, towers and all other non-vibration machinery. It should be cementitious, nonshrinkable and free flow with compressive strength equal or greater than the foundation’s concrete, but not less than 30n/mm2 in 7 days and 40n/mm2 in 28 days.

G2 Grout

It is generally used for prefabricated concrete structures, compressors, heavy equipment subjected to vibration and for massive structure’s column bearing plates. Minimum compressive strength should be 50N/mm2 in 7 days and 60n/mm2 in 28 days. The grout’s flexibile strength should not exceed 9n/mm2 in 28 days.

It should be cementitious, nonshrinkable high strength grout.

Mixing of grout

Mixing of grouting powder with water can be done mechanically using an electric drill

For Flowable grouting – Water:Powder = 0.14 to 0.16 by weight (4.2 to 4.8 litres water for 30 Kg bag)

For Pourable grouting – Water:Powder = 0.12 to 0.14 by weight (3.6 to 4.2 litres water for 30 Kg bag)

The minimum mixing time is 3 minutes

5. Bituminous grouting

In this method, hot bitumen is used as a grouting material. Hot bitumen is employed associated with solidify based suspension grout. this is often never really grout from spreading and to create the mechanical quality of the finished result.

A hard-oxidized environment friendly, having a high solidification point is used for grouting.

Process of bituminous grouting

Firstly, the bitumen is heated up to 200 degrees Celsius. At this time the grout has a dynamic viscosity in the range 15 to 100 cp.

Unlike another grouting, the hot bitumen’s curing is thermally driven. This hot bitumen turns from its fluid state to a highly viscous elastoplastic state, when it is injected into medium saturated water. Finally, when this is injected the pass is plugged.

6. Resin grouting

In traditional resin grout, it is the composition of epoxy resin mixed with the filler. But new type of water-based resin has been recently developed that is better than the traditional ones.

It is also known as penetration grouting and is the most conventional grouting for use. This grouting method is used in non-cohesive soil, sand, and other porous media for filling cracks and joints.

It is injected inside the porous medium without disturbing its original structure. It is commonly used in soil and rock deposits to change its geotechnical properties.

There are two types of Permeation grouting injecting system:

•              Circulating grout system

•              Direct grout system

Types of Grouting based on the the Process

1) Compaction grouting

 Compaction grouting is done to strengthen the subsurface or surface of the permeable soil to reduce the voids and sinkholes.

It is driven to the depth through the drill. Cement, sand, fly ash, and water is then placed from bottom to top according to the pressure criteria. After each step, the drill is lifted up until it is fully taken out. This grouting is commonly called low mobility grouting

2) Bentonite grouting

Bentonite is made up of the clay having thixotropic properties that is a highly water-resistant gel which forms the permanent barrier to water flow when mixed with additives.

This method is used in the soil particles that cannot accept the cement grouting. This is commonly used for plugging old wells.

It is composed of 50 pounds of powdered bentonite to 34 gallons of water in which 50 pounds of washed sand is added.

3) Fracture grouting

In this method, grout uses the low viscosity grouts that splits by hydraulic fracture under the high pressure and enters into the cracks by creating the lenses. It is also known as compensation grouting and is commonly used for structural releveling.

Procedure of hydraulic fracture:

In this method, a hydraulically pressurized liquid composed of water, sand, and chemical mixture is used to fracture the rock. Artificial cracks are provided with pre-split holes. Then, the grout is passed down the holes.

The casing is inserted to the fracture section and grouted. A pressurized fluid carrier is inserted into the opening casing and spread throughout fractures. The casing remains open after fracturing.

4) Jet grouting in construction

This is a process of creating soil concrete column or jet grouted column using high-pressure jet through the nozzle in a borehole.

The specially designed drill stem and the monitor are raised and rotated at slow, smooth, and constant speed cutting the soil with water or/and air at high pressure to create the soil concrete column. The end product is then cemented round column. This grout is effective for almost soil.

Procedure of jet grouting:

1.            Initially, the hole is drilled in the required place and depth.

2.            The drill is done until a weak subsoil exists. It may be up to 10 to 20 cm.

3.            Then, equipment is placed in the hole to conduct an injection process that consists of a jet grouting string of almost 7 to 10 cm.

4.            The string consists of a nozzle to have an injection on high velocity, having a diameter of 1 to 10mm.

5.            Then, the string is raised and rotated to seal the whole column with soil and the fluid system. Now, the jetting starts. The string is raised when the fluid is injected. For every raising, there is rotation performed smoothly and constantly. This gives a perfectly refined grouting column.

Types of jet grouting system

1.            Single

2.            Double

3.            Triple fluid system.

Application of jet grouting

•              Horizontal barriers

•              Groundwater control

•              Tunneling

•              Supporting excavation

•              Underpinning

Jet grouting steps

Types of Grout for Ceramic Tile 

There are four basic types of grout:

•              Unsanded Grout

•              Finely Sanded Grout

•              Quarry TypeGrout

•              Epoxy Grout

1. Unsanded Grout

This is used for wall tiles where the grout joint is less than 1/8” wide.

2. Finely Sanded Grout

This is used for floor tiles where the joints are 1/8” to 3/8” wide.

3. Quarry Type Grout

•              This is the same as finely sanded grout for ceramic tiles except that a coarser grade of sand is used.

•              The quarry-type grout is used for joints that are 3/8” wide to 1/2” wide such as those used with Terracota / Saltillo tiles.

4. Epoxy Grout

•              This consists of an epoxy resin and hardener.

•              Epoxy grout for ceramic tile is highly resistant to stains and chemicals and has a tremendous bonding strength.

•              It is ideal for countertops and other areas susceptible to stains.

IS code for grouting

A fundamental requirement of a grout is that it shall develop adequate gel strength after a control- Page 11 IS 14343 : 1996 lable interval of time. This should be determined by relevant test procedures.

Applications of Grouting

(Courtesy: sika.com)