Injection grouting is a technique used for repairing cracks, voids, and honeycombs in concrete or masonry structures. It involves filling these defects under pressure with a flowable plastic material called grout. The purpose of injection grouting is to strengthen damaged structural members and repair cracks to prevent further deterioration of the structure.
To ensure that the grout fills the gap or void completely, it should have negligible shrinkage. It should also remain stable after injection and not crack, delaminate, or crumble. There are various types of grouts available for repairing and strengthening concrete and masonry structures.
When selecting a grout for a particular type of repair work, it’s essential to consider the compatibility of the grout with the original material. The chosen grout should be compatible with the concrete or masonry in terms of properties such as strength, density, and durability. It’s important to choose the right type of grout to ensure that the repair work is effective and long-lasting.
Types of Injection Grouting and Materials for Concrete Crack Repair
When it comes to concrete crack repair, there are several types of injection grouting and materials that can be used. One of these is polymer injection grouting, which involves injecting a polymer material into the crack in order to seal it and prevent further damage. This type of grouting is commonly used for smaller cracks or where there is a need for flexibility, as the polymer material can expand and contract with the movement of the concrete.
Another type of injection grouting is fiber-reinforced grouting, which involves adding fibers to the grout mixture in order to increase its strength and durability. This type of grouting is often used for larger cracks or where there is a need for increased stability.
Cement-sand grouting is another popular option for concrete crack repair. This involves injecting a mixture of cement and sand into the crack, which hardens and seals the crack. This type of grouting is often used for larger cracks or where there is a need for increased strength and stability.
Gas-forming grouting is a unique type of injection grouting that involves injecting a gas-forming substance into the crack. This causes the grout mixture to expand and fill the crack, creating a strong seal. This type of grouting is often used for larger cracks or where there is a need for increased stability.
Finally, sulfo-aluminate grouting involves injecting a mixture of sulfo-aluminate cement and water into the crack. This mixture reacts with the concrete and forms a hard, durable seal. This type of grouting is often used for larger cracks or where there is a need for increased strength and durability.
1. Polymer Injection Grouts:
Polymer injection grouting involves the utilization of various polymers, such as polyester, epoxy, vinyl ester, polyurethane, and acrylic resins. Epoxy is the most commonly used polymer for epoxy grout, while polyurethane and acrylic resin-based polymers are preferred for treating underground and water-retaining structures, as well as preventing water seepage. Polymer injection grouts are available in both two and three component materials.
Three-component materials grout comprises liquid resin content, curing agent or hardener, and aggregate or dry filler. On the other hand, the two-component materials grouts consist of curing agent or hardener and aggregate or dry fillers. By adding modifiers to the basic resins and curing agents, the polymer injection grouts can be customized for repair works to achieve the desired properties.
It is important to note that the modifiers and other materials used may vary from one manufacturer to another. Therefore, it is essential to adhere to the manufacturer’s guidelines when selecting and using the polymer injection grouts.
Following are properties of different types of Polymer Based Injection Grouting:
Epoxy-based injection grouts have a number of notable characteristics. These grouts are not resistant to ultraviolet exposure or high temperatures, and they have a low pot life. However, they are non-shrink and flowable, making them highly effective in sealing cracks. Additionally, they exhibit excellent bonding with almost all building materials and have good chemical resistance.
Acrylic polymer-based injection grouts offer some improvements over their epoxy-based counterparts. They possess improved flexural and tensile properties, making them more resistant to cracking and segregation. They also exhibit improved impermeability and chemical resistance, and can set more rapidly. However, it should be noted that shrinkage may reduce or increase the grout’s resistance to corrosion of steel, as well as its ability to withstand dynamic loads and vibrations.
Lignosulfonate-based injection grout admixtures are also available. These admixtures can help to lower the viscosity of cement slurry and compensate for both drying and plastic shrinkage.
2. Fiber-Reinforced Injection Grouts:
Fiber reinforced concrete is a type of material commonly utilized in repairing damaged concrete and masonry structures. This approach involves incorporating fibers such as polypropylene, steel, or glass into a mixture of Portland cement or shrinkage compensating mortar. By doing so, the structural members can be strengthened and improved in terms of flexural strength, impact resistance, and ductility.
However, it’s worth noting that working with fiber reinforced injection grouts requires a certain level of skill and expertise. Without proper handling, there is a risk of segregation of fibers, which can compromise the overall quality and effectiveness of the repair work. Therefore, it is essential to ensure that the proper techniques are utilized when working with this material.
3. Cement – Sand Grouts:
Cement-sand grout is a commonly used grouting material for repairing concrete or masonry structures. It is readily available and widely used due to its cost-effectiveness. However, it is not recommended for areas where strength enhancement is necessary. This grouting method requires high amounts of water and cement to be injected into the structure. Unfortunately, using cement-sand grout can lead to shrinkage and cracking during the hardening process. To reduce this risk, appropriate shrinkage compensating agents are required. While cement-sand grout is commonly used in masonry buildings, it is not as commonly used in concrete structures.
4. Gas-forming Grouts:
Gas-forming injection grout is a type of grout that utilizes gas bubbles to compensate for the shrinkage of the grout after it has been applied. This type of grout is formulated with certain ingredients, typically Aluminum and Carbon powder, which react with the cement liquor to produce the gas bubbles that expand the grout. However, it is important to note that the gas-forming injection grouts are temperature-sensitive and may not be suitable for high-temperature applications.
Proper confinement is necessary to ensure that the gas-forming injection grout develops sufficient strength and volume stability. If the reaction forming the gas bubbles occurs too quickly, it may complete before the grout is placed, leading to an unstable and weak grout. Therefore, it is important to carefully control the temperature during the grouting process and to use appropriate techniques to ensure that the grout is properly confined. By doing so, it is possible to achieve a strong and stable grout that is well-suited for a variety of applications.
5. Sulfo-aluminate Grouts:
Sulfo-alum injection grout is a type of grout that utilizes the principle of shrinkage compensation. It is composed of either shrinkage-compensating cement or an anhydrous sulfo-aluminate expansive additive mixed with Portland cement. The addition of the expansive additive causes expansion during the process of hydration, which is a more dependable method than using gas-forming grouts.
However, it is important to note that the expansion of sulfo-alum injection grout requires post-hardening curing to be effective. This means that if moist curing is not available, the expansion may not occur as intended. Thus, proper curing techniques are essential for ensuring the reliability of the grout.
Overall, the use of sulfo-alum injection grout is an effective method for concrete repair, as long as proper curing methods are employed to ensure the desired expansion occurs.