Selecting Crack Filler and Crack Sealer
WELCOME to The Pavemade Crack Repair Master Guide, your easy-to-read practical field guide to asphalt repair. This aims to serve as your reliable guide and state-of-the-art data resource that would take you to the world of asphalt and concrete repair. Not only does it cover a broad scope of topics that ranges from identifying different types of cracks, but it also introduces you to various sealants and fillers and to application techniques on how to fix cracks.
This guide was made to be a helpful tool, whether you are just starting out or already an expert. Through this, newbies will understand the right steps to completely and correctly fix a client’s parking lot, driveway, or even a roadway. For professional sealcoating contractors, we included thorough discussions of particular topics of materials and methods of application.
We hope to curate a comprehensive guide about concrete and asphalt maintenance. We plan to have a continuous update on this guide and its success will depend on your valuable feedback. We would want you to inspire us with your input and give comments regarding the guide’s content, style and usefulness to your business. If you would want to give suggestions and contribute ideas, feel free to contact us!
What Are Pavement Cracks?
Having a basic understanding on why pavement cracks occur and knowing what to do about it are important steps towards skillfully repairing asphalt and concrete. Given the information presented in this section, you’re on your way to developing concrete repair knowledge and know-how.
Cracks on pavement are caused by stress buildup on the surface layer that exceeds the strength of the pavement. This stress triggers the concrete to crack and cause a fissure. Cracks are normally caused when traffic and temperature constantly change, creating strains that the pavement cannot hold. The cracks might open vertically or horizontally with temperature and moisture changes and may experience vertical movements due to load applications. Some factors that affect cracking of pavements include extreme and constantly changing temperatures, pavement structural design, construction quality, temperature susceptibility, aging characteristics of the asphalt cement, and traffic characteristics.
There are several types of cracks. Examples are fatigue cracks, longitudinal cracks, transverse cracks, block cracks, reflective cracks, edge cracks, and slippage cracks.
So what can you do with these? Sealing and filling are the two methods that can be done to repair the cracks in pavement surfaces. The cause of the cracks must be thoroughly determined because knowing this would help define the success of the sealing and filling efforts. By sealing and filling, water and other materials will be prevented from entering the cracks. These basic methods may vary in terms of the amount of crack preparation required and the types of sealant or filling materials to be used.
To Seal or To Fill?
Delving deeper into the world of asphalt and concrete repair requires an understanding of working and non-working cracks, and whether to use the sealing or filling method. This section does just that.
Now that you know the basic methods of repairing a crack, the next step is for you to determine whether to seal it or fill it. In order to know this, you must first determine whether a crack is working or non-working, and whether it undergoes a horizontal or vertical movement. Knowing such movements is important because the primary determining factor for whether a crack is working or non-working is its total horizontal movement over a period of one year. Other factors are the crack’s width and type. At this point, it is important to remember that cracks are only sealed or filled when greater than 3mm (0.1 inches) or up to 25mm (1 inch).
Going back to the question of whether to seal or fill the crack, the answer is that working cracks must be sealed, and non-working cracks can be filled.
Working cracks are those that experience extensive horizontal and/or vertical movement due to temperature change and/or traffic application. Typically, these cracks have horizontal and/or vertical crack movements of 2.5 mm or more. Working cracks can be transverse or longitudinal to the pavement, but most of the time it is transverse. In addition to this, the width of the crack plays a role in determining if it is a working or non-working crack. If the width exceeds 6 mm (1/4 in), then it must be sealed.
Non-working cracks are defined as those that experience relatively slight horizontal and/or vertical movement as a result of temperature changes and/or traffic loading. Non-working cracks usually have horizontal and/or vertical crack movements of less than 2.5 mm. When the conditions for working cracks is not met, or when cracks are closely spaced and have little movement, crack filling is less expensive.
Crack Sealing and Crack Filling
Knowing and learning the details of sealing and filling methods are important when you want to effectively repair asphalt concrete cracks. With this section, you will have a broader understanding on what it takes to repair a seemingly simple crack.
Crack sealing and filling both prevent the intrusion of water and incompressible materials into cracks. How these methods vary depends on the amount of crack preparation required, and also on the types of sealant materials used.
As mentioned in the previous section, crack sealing is the perfect solution to working cracks. This method requires comprehensive crack preparation and often needs specialized high quality materials placed either into or above the working cracks. This is considered as a longer-term solution, as compared to crack filling.
Crack sealing treatments are usually applied when the crack width is at its midpoint to widest; as asphalt expands in warmer temperatures, this normally happens during winter, spring, and fall (or basically during moderately cold weather conditions). For this method, the weather condition must always be appropriate; it must be not too cold or wet.
Since non-working cracks do not change in width considerably with temperature, application of crack filling can be done at any time of the year when weather conditions are suitable for treatment.
It is also important to note that traffic passing over a hot applied sealed or filled crack is actually not an issue; but traffic control during the treatment application should be in force long enough to allow for sufficient curing of the product and prevent tracking.
Crack Sealants and Fill Material
In addition to knowing the methods, you should also learn about the materials used in sealing and filling cracks. Basically, the difference between crack sealants and crack fill material has something to do with their performance. Generally speaking, crack sealants are the ones with higher-performance materials and are required to expand and contract under a variety of temperatures and loads. The main requirement of fill material, on the other hand, is to avoid the intrusion of water and incompressible materials.
Understanding how crack sealants work will enable you to use it properly and effectively. The success of sealing cracks also depends on how much you know about the sealing materials.
Crack sealing materials are made to hold to the walls of the crack, expand with the movement of the crack over various conditions and loads, and resist abrasion and damage produced by traffic. For sealing working cracks, the ideal sealant is commonly elastomeric. This may sound complicated, but this simply means that the sealant can easily stretch high distances (at around a hefty 10 times its non-strained dimensions!) without breaking up. Such sealants also recover over time to close to their original dimensions. These sealants are normally used at high temperatures because they tend to get so thick when used at ambient or normal temperatures, and they set or cure by cooling and reforming into intricate structures. Called thermoplastic, hot pour materials need a very high temperature, normally between 370 to 390°F (188 to 200°C). It is important to note though that these materials might get damaged or cross link when exposed to extreme temperatures for long periods of time. That is why you must always follow the manufacturer’s recommendations precisely.
Thermoplastics can form physical structures while cooling but this can be reversed when reheated. Hot application guarantees good adhesive bond to the crack walls. Most of the hot pour materials are rubber-modified asphalt which have outstanding abrasion resistance and are very useful for higher trafficked surfaces.
On the other hand, cold pour materials for crack sealing are typically silicone based and often used before paving. The materials can cure by either being exposed to moisture in the air or by mixing with a hardening agent with the base silicone. These materials often have low abrasion tolerance and you might not want to use it in trafficked areas.
Depending on the amount of preparation and material selection, it has been found that crack sealants can give you up to 9 long years of service. Due to the moving nature of working cracks a perfect crack sealant must be able to:
- Remain adhered to the walls of the crack
- Elongate to the maximum opening of the crack and go back to its original dimensions without breaking
- Expand and contract over a range of service temperatures without breaking or separating from the crack walls, and
- Resisting abrasion and damage caused by traffic.
This section lets you have a closer look at the materials used for filling cracks. Similar with that of knowing more about the sealants, having a deeper understanding of the filling materials will enable you to use these properly and effectively.
Simply put, crack filling is the placement of materials into non-working or low movement cracks to reduce penetration of water and incompressible materials. These cracks are not totally inactive and need some flexible characteristics. Filling usually involves less crack preparation than that of sealing and performance requirements are a bit lower as compared with the filler materials. It is often considered as a short-term solution that aims to hold the pavement together between major maintenance operations or until a scheduled rehabilitation activity. Fillers can give up to 8 years of service.
Crack filling materials can either be hot-applied rubber or polymer asphalts, or cold-applied emulsion-based products. The emulsion products help form a good adhesive bond with the crack wall, and additives like Styrene Butadiene Rubber (SBR) latex guarantees that the material can tolerate some amount of traffic. In some cases, hot-applied fiber-modified asphalt binders may be used.
A suitable filler material must be able to:
- Remain attached to the walls of the crack,
- Possess some elasticity, and
- Resist abrasion and damage caused by traffic.
It is important to remember that emulsions or asphalt materials located in a flush configuration in unrouted cracks can provide 2 to 4 years of service, while hot applied rubber and fiber modified asphalt fillers located in a flush or overbanded configurations can give you around 6 to 8 years of service.