Injection grouting is a technique used to repair and strengthen concrete or masonry structures by filling cracks, voids, or honeycombs under pressure. The process involves using a flowable plastic material called grout, which should have minimal shrinkage to completely fill gaps or voids and remain stable without cracking, de-lamination, or crumbling.
Different types of grouts are used for repairing and strengthening concrete and masonry structures, and the selection of the appropriate grout for a specific repair job should be based on the compatibility of the grout with the original material.
Grout is an important material for repairing and strengthening concrete or masonry structures because it helps to restore the integrity and stability of the structure. However, selecting the right type of grout is crucial to ensure the effectiveness of the repair work. Therefore, it is important to consider the compatibility of the grout with the original material before beginning any repair work. This will help to ensure that the repair work is durable and can withstand the stresses and strains placed on the structure over time.
Types of Injection Grouting and Materials for Concrete Crack Repair
Following are the various types of injection grouting and materials for concrete crack repair:
- Polymer injection grouting
- Fiber-reinforced injection grouting
- Cement – sand grouting
- Gas-forming grouting
- Sulfo-aluminate grouting
1. Polymer Injection Grouts:
Polymer injection grouting is a technique that utilizes polymers, such as polyester, epoxy, vinyl ester, polyurethane, and acrylic resins, for various purposes. Epoxy is the most commonly used polymer for epoxy grout, while polyurethane and acrylic resin-based polymers are ideal for treating water-retaining and underground structures and preventing water seepage. Polymer injection grouts come in either two-component materials or three-component materials. The three-component materials include liquid resin, curing agent or hardener, and aggregate or dry filler, while the two-component materials consist of only the curing agent or hardener and the aggregate or dry filler. To customize the grout for repair work, modifiers are added to the basic resins and curing agents to achieve the desired properties. However, the recommended usage of these materials may vary depending on the manufacturer, and it is essential to follow their instructions for optimal results.
Following are properties of different types of Polymer Based Injection Grouting:
There are various types of injection grouts available in the market, each with its unique set of properties and benefits. Epoxy-based injection grouts are known for their excellent bonding capabilities with almost all building materials, effective sealing of cracks, and good chemical resistance. However, they have certain drawbacks such as a low pot life, non-resistance to ultraviolet exposure and high temperatures, and non-shrinkage.
On the other hand, acrylic polymer-based injection grouts have improved flexural and tensile properties, resistance to cracking, segregation, improved impermeability, chemical resistance, and rapid setting. They are also resistant to dynamic loads and vibrations, which is an added advantage. However, shrinkage can impact their corrosion resistance, either positively or negatively.
In addition to these types of injection grouts, there are also lignosulfonate-based injection grout admixtures. These admixtures are known to lower the viscosity of cement slurry, which helps in compensating for drying and plastic shrinkage. This property makes them a valuable addition to the construction industry as they help to reduce the potential for cracking and other issues.
2. Fiber-Reinforced Injection Grouts:
Fiber reinforced concrete is a commonly used material for repairing and strengthening concrete and masonry structures. It involves adding fibers, such as polypropylene, steel, or glass fibers, to Portland cement or shrinkage compensating mortar. This results in improved flexural strength, impact resistance, and ductility of the structural members.
Another application of fiber reinforcement is in injection grouts, which require skilled handling to prevent the segregation of fibers. The grout is injected into the damaged area to repair and strengthen the structural member. The fibers in the grout help to provide additional reinforcement and improve the overall performance of the repaired structure.
Overall, the use of fiber reinforcement in repairing and strengthening structural members has become a popular choice due to its effectiveness in improving the mechanical properties of the material. Whether it’s in concrete, masonry, or injection grouts, the addition of fibers can greatly enhance the strength and durability of the repaired structure.
3. Cement – Sand Grouts:
Cement-sand grout is a commonly used material for repairing concrete or masonry structures that require minor repairs. This type of grout is readily available in the market and is considered to be the most affordable option for repairing structural members. However, it is important to note that cement-sand grout is not suitable for areas where structural strength enhancement is required.
To inject cement-sand grout into the affected area, a high water and cement content is necessary. Unfortunately, the use of this material can lead to shrinkage and cracking during the hardening process. To counteract these negative effects, it is recommended to use suitable shrinkage compensating agents.
While cement-sand grout is commonly used in masonry buildings, it is not as frequently used in concrete structures. Despite its drawbacks, it remains a popular option due to its low cost and availability. Overall, cement-sand grout is a useful material for minor repairs that do not require significant structural changes.
4. Gas-forming Grouts:
Gas-forming injection grout is utilized in construction applications where the principle of using gas bubbles to expand the grout is required. This expansion compensates for any shrinkage that occurs after the grout has been applied. The formation of gas bubbles is facilitated by a reaction between certain ingredients, typically Aluminum and Carbon powder, that are contained within the grout and the cement liquor. It is important to note that these grouts are temperature-sensitive and may not be suitable for high-temperature applications. Moreover, they require proper confinement to ensure that the grout develops strength and volume stability. If the reaction that forms the gas bubbles occurs too rapidly, it may be completed before the grout is placed.
5. Sulfo-aluminate Grouts:
Sulfo-alum injection grout is a type of grout that utilizes the principle of shrinkage compensation. It employs either shrinkage-compensating cement or an anhydrous sulfo-aluminate expansive additive in conjunction with Portland cement. Upon hydration, the additive causes expansion, which occurs after the grout has set. This method of expansion is considered more dependable than gas-forming grouts. However, post-hardening curing is necessary for the expansion of such grouts to be effective. Moist curing is required for this method to work, and if it is not available, the grout will not be effective. More information on concrete repair guides can be found by following the link.