Chemical grouts come in two types: hydrophilic and hydrophobic. Hydrophilic grouts are attracted to water and seek it out, whereas hydrophobic grouts repel water and typically resist moving toward wet areas. Each type is better suited to different projects, and it’s critical to know which to use and when.
When to Use Hydrophilic Grouts
Hydrophilic grouts are made specifically for injection into tight cracks and pores, which helps to stabilize wet concrete or masonry. The material forms an incredibly strong bond to masonry and wet concrete and can be an effective long-term solution if properly used and cared for.
Hydrophilic grouts can also be used for waterproofing a spalled or cracked concrete surface. Spalling occurs when the water-cement ratio is too high. As liquid migrates through cracks in the concrete, it expands from its original volume and causes flakes to separate from the slab.
Why Use Hydrophilic Grouts?
Why should you use hydrophilic grouts? They are exceptionally good at sealing out water, and if you have an issue with water penetration through cracks and crevices, then hydrophilic grouts will do the trick.
How to Use Hydrophilic Grouts
If you want to seal a surface using hydrophilic grout, there are four steps:
- Ensure your work area is free from dust, dirt, loose debris, and other contaminants before applying the mix for sealing purposes.
- Mix the grout with water to a consistency that is neither too runny nor too dry.
- Apply the mixture liberally, filling all cracks and crevices until it runs out of them naturally onto the surface you want to be sealed.
- Scrape any excess off to prevent staining on surfaces.
It’s important to note that hydrophilic grouts retain water after curing. If the water-resin ratio is too high, then you could encounter issues with excessive shrinking during dry periods.
When to Use Hydrophobic Grouts
For areas that have a regular wet-dry cycle, hydrophobic grouts are ideal since they don’t shrink in the absence of water. These types of grouts are also perfect when needing to seal gushing leaks, fill voids, stabilize soil, and provide compression sealing. Gushing leaks can be partially sealed using hydrophobic grouts, then when the leak is manageable, hydrophilic grout can be used to finish the job.
Why Use Hydrophobic Grouts?
One of the most important aspects of sealing a leak is whether or not the sealant has any shrinkage after curing. Hydrophobic grouting does not. This is one of the biggest reasons why many contractors like to use hydrophobic grouts for large-scale sealing projects.
Hydrophobic grouting is great for sealing large leaks and filling voids. Since it does not shrink, it’s also good at providing a base where other materials or objects, like a CNC milling machine, can sit and be installed on top of the material without any movement that might jeopardize its integrity.
How to Use Hydrophobic Grouts
Hydrophobic grouts are ideal to use when filling large areas, thanks to their expansion rate. With hydrophobic grout, it’s important to remember that:
- They need little to no water to react and transform from liquid to rigid foam.
- During expansion, they will push farther into the substrate, repelling water back into the micro-cracks and fissures that form off the main crack.
Hydrophobic grout should not be used if compression of the crack is expected. If the cured foam is compressed, it will reduce in size and be unable to reform to the proper size required to plug the leak or fill the void into which it has been installed.
Hydrophobic chemical grouts are typically not recommended for repairing minor leaks in cracks or joints. This will only repair the leak temporarily, and you’ll have a repair job on your hands later due to their poor bonding with the interior walls of the crack.
Christine Evans is the Director of Product Marketing & Content Strategy at Fictiv, an on-demand manufacturing company. Over the past six years, Christine has grown Fictiv’s popular Hardware Guide and Digital Manufacturing Resource Center, with over 2,000 teardowns, DFM guides, and mechanical design articles to help democratize access to manufacturing and hardware design knowledge.
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