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What is Injection Grouting – Its Types, Procedure and Benefits

One of the most common issues that most construction workers face is dealing with holes, cracks, fine pores, uneven surfaces, etc. These not only deteriorate the surface texture but also weaken the overall construction. Germs, pests, and bugs can thrive in holes, cracks, and other depressions. So injection grouting is the best way to solve these issues. It is a new method of filling holes rather than reapplying plaster to the entire wall. Despite its importance, only some people are aware of injection grouting.

Injection Grouting
Fig: Injection Grouting

What is Injection Grouting?
The process of injecting grout into open joints, cracks, voids, or honeycombs in concrete or masonry structural members is known as injection grouting. The desired outcomes, such as strengthening a structure and preventing water infiltration, are achieved under pressure with a grout material that cures in place.

The shrinkage of grout, a flowable plastic material, should be minimal to fill any gaps or voids and remain stable without cracking, delaminating, or crumbling. Various types of grouts are available for strengthening and repairing masonry and concrete structural members. The type of grout chosen for a specific type of concrete or masonry repair work should be based on how well the grout works with the original material.

Different types of Injection Grouting:
1. Polymer Injection Grouting:
Polymers in polymer injection grouting include polyester epoxy, vinyl ester, polyurethane, and acrylic resins. The polymer is an epoxy grout that is widely used. Polymer injection grouting is available in various grout materials, including liquid resin content, curing agent, and aggregate. These injection grouting types are appropriate for concrete repair work. To achieve the desired properties, polymer injection grouts can be modified by adding modifiers to basic resins and curing agents. Polymer-based injection grouting comes in three varieties:

i) Epoxy-Based Injection Grouting:
It is resistant to UV exposure and high temperatures, is non-shrinkable, effective in crack sealing, and has good bonding with all construction materials.

ii) Lignosulphonates Based Injection Grouting:
When plastic shrinks and dries out, this injection grouting help to make up for it.

iii) Acrylic Polymer Based Injection Grouting:
It has tensile characteristics and is waterproof, resistant to segregation, and resistant to cracking. It sets quickly and is chemical-resistant.

2. Fibre Reinforced Injection Grouting:
Concrete with fiber reinforcement is frequently used to repair masonry and concrete structural members. The structural members are typically repaired and strengthened using Portland cement and fibers such as polypropylene, steel, or glass. Injection grouting with fiber reinforcement offers good flexural strength, impact resistance, and flexibility.

3. Gas-Forming Grouting:
The basic concept behind gas-forming injection grouting is that the gas bubbles expand the grout to compensate for shrinkage after it has been applied. These gas bubbles will combine with the cement slurry to form ingredients. Proper confinement is required to develop good strength and volume stability. The reaction that creates the gas bubbles is very fast and will be completed before the grout is applied. Because this type of grouting is temperature sensitive, it cannot be used in places where the temperature is extremely high.

4. Sulfo-aluminate Injection Grouting:
Anhydrous sulfo-aluminate additives are used as the grout to prevent cement shrinkage. It allows the grout to expand once the setting is complete, allowing the curing process to be completed quickly. However, if the curing process is dry, it will not be suitable for injection grouting.

5. Cement Sand Injection Grouting:
It requires a sizable amount of cement and water combined. The cement and water mixture shrinks during the hardening phase, which causes the grout to crack or split open, even though it is perfect for masonry and progress structures. Since increasing strength is not the main objective, it is primarily used in those situations. Additionally, it is not recommended in areas that require extensive repair work because the mixture shrinks and leaves gaps that must be filled in.

Types of Grouting Materials:

i) Epoxy resin.
ii) Cement grout or cement-based mortars.
iii) Cement sand with additive grouts.
iv) Polymer Modified cement grout.

Properties of Grouting Materials:

Procedures of Injection Grouting:

i) Drill the Ports on the Surface:
Drill short holes, also known as ports, into cracks/openings to serve as entry and venting terminals. The minimum port diameter and depth are 2.5cm and 5cm, respectively. The distance between holes varies from 150 mm c/c for finer cracks to 300 mm c/c for others. Port spacing is typically kept greater than the desired depth of grout penetration, but it may be adjusted based on judgment and project requirements.

ii) Cleaning the Holes and Cracks:
It is critical to clean and flush the cracks and holes thoroughly before beginning the grouting process. Cleaning the cracks can be done either manually or with a vacuum. Sprinkle water into the cracks. It is critical to thoroughly clean it to form a strong bond and gain maximum strength.

iii) Seal Cracks Between Ports:
Epoxy, polyester or cementitious materials should be used to patch the crack between the ports. The time required to harden the seal depends on the material used. Cracks are typically routed 6 mm wide and 13 mm deep to stiffen the surface seal. The crack can sometimes be cut out to a depth of 13 mm and a width of about 20 mm in a V-shape, which is then filled with epoxy to achieve a flush surface. Surface seals and ports are applied on both sides of a structure with cracks, such as a wall.

iv) Grout the Hose Connections:
A hand-held, cone-shaped fitting on the grout hose is sufficient for smaller grout pressures up to 350 kPa. To obtain grout hose connections for higher grout pressures, short pipe nipples are connected to the holes. Fix the nipple or pipe into the holes and seal it with adhesive so it cannot move.

v) Injection Grouting on the Cracks:
The grouting machine should be used to inject the grout material into the crack. With pressure, it ought to be filled. Skilled labor was necessary for injection grouting. When processing, keep in mind the local temperature.

Applications of Injection Grouting:

Benefits of Injection Grouting:

Injection Grouting is applying grout under pressure to fill voids and cracks in structural elements to strengthen masonry structures that have been damaged or deteriorated and to repair cracks. You can easily decide if you need this process of repairing gaps and cracks in masonry and concrete structures now that you are aware of the major facts. Furthermore, you will understand when to call a professional because certain types of injection grouting necessitate extensive and specialized skill levels.

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5. Sofi, Waseem. “Why Is Injection Grouting Important, and Where Is It Used?” Why Is Injection Grouting Important, and Where Is It Used?, 25 Oct. 2022,
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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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