Highway Preventive Measures and Preservation Treatments
Pavement preservation is a proactive approach for pavement maintenance and preservation to keep them within the right conditions (Walker, 2019). Before the right pavement repair strategy can be adapted to any distressed asphalt pavement, its extent and type of deterioration have to be understood. At the same time, the primary cause of its distress is identified. Among the common causes of pavement distress includes; disintegration, cracking, distortion, and skidding hazards. Additionally, the common causes of pavement deterioration involve; climatic influences, traffic loading, and material quality problems (Walker, 2019). As pavements age or experience traffic repetitions, there is an accumulation of pavement distress. Moreover, pavement distress can also compound itself from various issues like a crack allowing water to slip through the pavement. This factor leads to the development of stripping or potholes (Walker, 2019). Based on this understanding, performing timely maintenance on the pavement is a crucial undertaking. Among the most commonly applied maintenance actions include crack and joint sealing, patching, and fog seals. These pavement maintenance actions help slow down the overall deterioration rate because they identify and address existing pavement deficiencies that contribute to the overall deterioration. On the other hand, pavement rehabilitation refers to repairing specific portions of existing pavements to reset the deterioration process. For example, removing and replacing wearing course within a pavement allows for the provision of new wearing materials on which a deterioration process can begin afresh.
Materials to Preserve Flexible and Rigid Pavements
A normal flexible pavement comprises bituminous surface courses lying over a base course or a sub-base course. The material that male up the surface course is layers of bituminous material or Hot Mix Asphalt (Walker, 2019). Such pavements tend to have negligible flexure, and it is a factor that causes them to experience deformations when exposed to too many loads. On the other hand, rigid pavements tend to have high flexural rigidity on their concrete slab, which means that their pavement structure can only deflect little under load because of a high modulus elasticity within their surface course (Walker, 2019). This concrete slab can distribute traffic load in large areas that have small depth. This situation minimizes the overall need to have several layers that help reduce stress.
Moodley (2019) argues that pavement preservation can be a powerful tool for prolonging systems with limited government budgets. At the same time, under such setups, contracting services tend to be one way that allows for expansion of preservation programs. Today, various pavement preservation treatments leverage on asphalt emulsions, particularly for bituminous-surfaced roads. Surface treatment using the asphalt emulsion technique involves a homogenous mixture involving two insoluble substances, mainly oil and water (Moodley, 2019). Asphalt emulsions have a chemistry that allows for excellent coating or adhesion of residual asphalt cement on the aggregate surface in open-graded and dense mixes. An asphalt emulsion is also an economical approach, particularly where very little mix quantities have to be produced remotely away from the asphalt plants.
Crack Sealing, Crack Filling, and Joint Sealing
Cracks on pavement can be addressed using different approaches, namely, crack sealing, crack filling, and joint sealing. The more involved and permanent approach is crack sealing. The technique is intended to bar foreign materials and water from entering pavements where cracks exist. Crack sealing tends to be an effective technique when applied in areas where the pavement moves at the cracks (Horan, 2019). This technique requires very little work to prepare, and its primary intention is to reduce the volume of water that entering into the pavement. Both pavement filling and sealing are intended to extend a pavement’s life by reducing fatigue, striping, and raveling (Horan, 2019). The sooner these techniques are applied on a pavement, the better the probability of extending its life. For pavements with numerous hairlines or surface cracks, joints sealing’s can be applied
Localized Pavement Repair
Portholes form due to contraction and expansion, especially during water cycles occasioned by freeze-thaw combined with the overall traffic on these pavements. In most cases, potholes tend to appear during late winter or early spring due to changing temperatures. This constant thawing and freezing, combined with the spring rain, tend to weaken pavements, leading to potholes and cracks (Horan, 2019). Potholes exist in different shapes and sizes, which implies that the material and method used to repair these portholes should also vary to match these changing conditions (Horan, 2019). In particular, the overall quality of an asphalt mix used to repair potholes tends to make huge differences, particularly regarding the pothole repair’s durability and aesthetics. Several custom mixes are developed to ensure that appropriate asphalt mix is made to patch potholes.
Chip Seals, Fog Seals, and Slurry Seals
A cheap seal refers to a pavement surface treatment combining two or more layers of the asphalt pavement with a single or finer aggregate layer. In the US, chip seals are normally used on roads with low traffic volumes in a process called asphaltic surface treatment (Lee & Shields, 2011). On the other hand, a fog seal refers to the light application of diluted asphalt emulsion sprayed on the existing surface. This technique is often used when renewing HMA pavements that have bristled with age and lessen raveling and surface defects (Lee & Shields, 2011). In most cases, rejuvenation emulsions are often applied as fog seals to enhance aged asphalt properties and replace them with some asphalt components lost during aging. Rejuvenator seals tend to be effective when the distress is more than the normally addressed chip seals. Finally, slurry seals are mixtures of graded fine aggregates, water, and asphalt emulsion. Slurry seals are often applied as surface treatments, with their application being in the thickness of large aggregate particles (Lee & Shields, 2011). Slurry seals don’t increase a pavement’s structural capacity but instead help reduce surface distress resulting from oxidation, end raveling, or improved skid resistance.
Hot Mix Asphalt (HMA) Overlay
Thin overlays that are constructed using warm or hot mixes of HMA are the most common presentation techniques. Such overlays are often put at thicknesses of about 1.5 inches, and they contain top-size aggregates of about 0.5 inches or less (Wang, 2013). They contain several variations ranging from thin, bonded, and ultra-thin wearing course overlays.
Normally, thin lift overlays are placed between 1.0 to about 1.5 inches in thickness. On the other hand, the ultra-thin overlays tend to take advantage of the slightly finer gradations, and they are placed at a thickness of about 0.6 to 1.0 inches (Wang, 2013). These mixes are often designed using the current best practices, with the binder grades generally being selected based on climate and traffic conditions. Utilizing such overlays tends to provide safe and smooth riding surfaces that can last for about ten years and beyond, especially when put in low distress surfaces (Wang, 2013).
Horan, B. (2019). Explore free pavement preservation webinars. Retrieved from https://asphaltmagazine.com/pavementpreservationwebinars/
Lee, J., & Shields, T. (2011). Treatment guidelines for pavement preservation. doi:10.5703/1288284314270
Moodley, S. (2019). Prioritising maintenance and rehabilitation projects to ensure sustainable pavement preservation. Pavement and Asset Management, 159-164. doi:10.1201/9780429264702-19
Walker, D. (2019). The importance of preserving pavements. Retrieved from https://asphaltmagazine.com/the-importance-of-preserving-pavements/
Wang, H., & Wang, Z. (2013). Performance evaluation of pavement preservation using long-term pavement performance data. Airfield and Highway Pavement 2013. doi:10.1061/9780784413005.070