Injection grouting is a specialised construction technique designed for strengthening, stabilising, and repairing various structures. This process is carried out under pressure with a grouting material that fills the cracks, open joints, voids, or honeycombs in concrete or masonry structural members to produce a desired result, like preventing water ingress.
However, while injection grouting is evidently an indispensable tool in modern construction and infrastructure maintenance, the selection of the grout for a particular project is essential. Let us help you make an informed decision by sharing an overview of the various grouting materials available and the factors to consider when choosing one for your project.
Grout is a combination of cement, sand, and water or chemical substances that is applied in pressure grouting injections to fill voids and seal the joints between a building’s foundation. To put it simply, it is used to fill cavities, with its primary application being the reinforcement of concrete structures and the prevention of water seepages. In fact, when the grouting material is correctly mixed and applied with quality workmanship, it forms an effective water-resistant seal that stops moisture ingress for years.
Notable characteristics of grout include:
As we have highlighted, the grout selection for your construction project is pivotal. As a result, you must understand the common types available and their characteristics to ensure you implement the most appropriate treatment to strengthen the infrastructure and prevent any leakage problems.
Polyurethane (PU) injection grouting is ideal for dealing with water leakage issues. Due to its versatile and close-cell nature, the PU resin is suitable for dealing with both fine cracks and larger fissures. It creates a resilient and flexible seal that prevents moisture and water from permeating structural joints and crack lines, thus ensuring a durable and permanent watertight seal.
Another reason for its popularity is its elasticity characteristic, which allows it to withstand not only thermal movements but also mechanical loads. That, along with its durability, cost-efficiency, and easy application, has made PU grouting material a standout solution for most construction projects.
Learn More: Building Resilience: 4 Advantages of PU Injection Grouting
Like polyurethane grout, epoxy grout is derived from mixing a base material and a hardener. The adhesive material produced offers a robust bond when applied, resulting in extremely low failure rates, thus making it suitable for tiny and ultra-fine cracks. If you seek reliable grouting work, look no further than epoxy grout. Regardless of thermal tension or soil pressure, the material is durable enough to withstand it.
With that said, the material also comes with several drawbacks. For one, epoxy takes a longer time to cure, often requiring more than an hour at room temperature. Furthermore, it can be more challenging to apply than regular grout and costs more. These factors combined can significantly impact the timeline and budget of your project.
Cementitious grout, a mixture of sand and water, is one of the most traditional grouting materials available. It can be further classified into two sub-categories – sanded and non-sanded grout. The latter is suitable for joint widths 4mm or smaller. Meanwhile, the former is ideal for joint widths above 4mm.
While cementitious grout is usually easier to work with and cheaper than epoxy, most contractors have moved away from this injection material in recent years. Its highly viscous nature requires significant mechanical pressure to grout into the structure, which can further stress and damage a structure.
Its porous features also allow moisture to seep through the grout, promoting the growth of bacteria, mould, or mildew under its surface. Moreover, the material is not highly resistant to chemicals\, which means that it will deteriorate when exposed to alkali or acid compounds. As such, regular maintenance is necessary over time, thus increasing costs.
Acrylic grout features a flexible gel with low adhesive,, and tear strength, making it extremely stain and crack-resistant. As a result, this injection material is most suitable for dynamic cracks and movement joints.
Another crucial benefit of acrylic grouting is its suitability for curtain grouting. In instances where exterior excavation is cost-prohibitive, curtain grouting offers a permanent solution for stopping active leaks, preventing situations where the liquid is flowing through the wall and into the structure.
Various manufacturers, like Adcos Asia, have a comprehensive portfolio of grouting products to support a broad range of projects. However, the truth is that no one grouting material is suitable for every application. So, the pertinent question is: how do you choose the ideal grout? Keeping the below factors in mind can help you make an informed choice.
When deciding on the appropriate grouting material, it is essential to fully understand the unique properties of open-cell and closed-cell formulations and assess each option and how they pertain to your project before moving forward.
Grout products are classified as ‘open-cell’ when more than half of the foam’s cells are open. Naturally, this makes such formulations more porous. As a result, they are only useful as a temporary solution to a water leakage problem. However, their very nature provides greater flexibility, allowing them to more easily conform to various sealing applications than closed-cell foams.
Conversely, the cells within closed-cell foams are completely enclosed and do not interconnect with other cells. As a result, they are sturdy and do not require a second treatment with resin. Their closed-cell nature makes them ideal for projects where liquid resistance is critical, such as hydropower applications and deep tunnel sewerage systems, as they can seal any crevices effectively, thus reducing liquid and gas flow.
When paying attention to the grout strength reported by manufacturers, it is essential to note that the figures quoted are usually established under controlled conditions, which may differ from results reported for site-prepared samples. Nevertheless, they can serve as a vital guide. The crucial numbers you should heed include the compressive and tensile strength of the grouting material.
While cement-based grout often has high compressive strength, it will generally have relatively lower tensile strength than epoxy grout, which can virtually glue the baseplate to the concrete foundation, making any future removal much more challenging (something for you to note). Meanwhile, polyurethane grout offers the ideal balance in both departments.
As we mentioned, there is no one-size-fits-all grout solution for every application. Distinct scenarios will require different grouting materials that best fit the circumstance at hand. For example, situations such as grouting at a tunnel face to permeate longer distances may favour 1-component resin instead of 2-component resin due to the ability to control the reaction time when in contact with water.
In contrast, 2-component resin works well when you need an immediate reaction to stop gushing water. Such incidents can happen during a sudden blowout during excavation or when the contractor cannot achieve sufficient drilling depth to prevent chemical wash-out. Remember, the workability or viscosity of the grout must suit the requirements of your project. If you are unsure, do not hesitate to consult the manufacturer and let them know your needs.
The grouting environment can play an essential role in determining the ideal injection material to use. For instance, cement-based grout is not chemical resistant. However, it can handle extreme temperatures (up to 250°C), provided you apply it correctly and allow it to cure completely before exposure.
Meanwhile, while epoxy grout cannot withstand water and long-term exposure to high temperatures unless they are specially formulated for such environments, it is usually the better choice when chemical resistance is necessary. However, polyurethane grout is the best option in this regard, as its durability allows it to fulfil either criterion.
In addition, it is essential to note that the temperature and PH levels of the water are crucial to the reaction time of the resin when solving high-flow situations. Cold water will prolong the reaction time of the resin, while hot water will accelerate the reaction time of the resin.
Before starting any project, it is recommended that you clearly outline any challenges and requirements for a particular grout in the project specification. Being too generic may lead to the use of inferior or ill-suited materials. Meanwhile, a narrow stipulation may cause a delay, as you spend too much time looking for the right product.
Now that you have a clear understanding of how to select the ideal injection material, it is crucial for you to familiarise yourself with the grouting process, as each step must be executed correctly with expert supervision to ensure the best result. The entire procedure is outlined step by step below.
Drill short holes, otherwise known as ports, into the cracks at a regular interval to serve as entry and venting terminals. The minimum diameter and depth of the ports should be 1 cm and 10 cm, respectively.
Meanwhile, the spacing between each hole should be approximately 150 mm c/c for finer cracks to 300 mm c/c for others. Additionally, the gap between each port is usually kept greater than the desired depth of grout penetration. However, this can be adjusted depending on the actual situation and requirements for a particular project.
The opening surfaces between ports can be covered using cementitious patching mortars or epoxy putty. Please note that the time required for the adhesive to harden depends on the type of injection material used. To stiffen the surface seal, the cracks are generally routed 6 mm in width and 13 mm in depth.
Occasionally, the opening can extend to a width of around 20 mm and a depth of 13 mm in a V-shape, which is then filled with epoxy to achieve a flush surface. If there are cavities passing through the structure, such as a wall, the surface seals and ports are applied on both sides.
Subsequently, the crevices may be sealed by plugging them with cloth or fabric. This way, water or air can still pass through while retaining the solids. Paper and plastic materials are not suitable for this application.
Before grouting can begin, it is crucial to clean and flush the cracks and holes properly with clean water. This process helps achieve the following objectives:
For lower grout pressures up to 350 kPa, a hand-held, cone-shaped fitting on the grout hose is sufficient. If the grout pressure is any higher, short pipe nipples must be connected to the holes to obtain a grout hose connection. Remember to fix the nipple or pipe in the holes and seal it with adhesive to prevent it from shifting from its place.
In cases of V-grooving, you need to drill holes 10 mm in diameter and 10 to 25 mm deep below the groove at the required spacing to install the entry and vent ports. The pipe nipple or tyre valve stem is usually bonded with an epoxy adhesive.
Meanwhile, the primary installation method for rectangular grooves is to use a flush fitting with an opening at the top for the adhesive to enter and a flange at the bottom bonded to the concrete face.
Grouting usually starts with relatively thin grout, which is thickened as quickly as possible to the heaviest consistency that can be pumped without blockage. You can begin the process at one end of a horizontal opening or the bottom of a vertical opening and continue until grout appears at the next port or the surface seals of the cracks bulge out.
When this happens, you can shift to the next hole. Ensure the port valves, where the grout flows out, are plugged before moving to the subsequent injection location. Please exercise extreme caution when injecting cracks that are not visible on all surfaces. The pressure must be carefully applied and should not be excessive.
For vertical or inclined crevices, the procedure begins by pumping your selected grouting material, whether it is epoxy or polyurethane grout, at the lowest level until it reaches the entry port above. Afterwards, the lower injection port is capped. This action is repeated until the crack is filled.
Injection grouting is undoubtedly a versatile and effective technique to address various challenges in construction, infrastructure, and maintenance. However, its effectiveness throughout multiple applications depends significantly on your choice of grouting material. By keeping what we shared in mind, you can continue to rely on this method as a valuable tool for achieving sustainable and resilient structures.
At Adcos Asia, our portfolio of speciality chemicals is designed to solve complex issues, such as heavy water ingress and structure leakage, providing flexibility and customisation to meet the specific needs of each project. Contact us today to learn more about our chemical grouting solutions.
